International Journal of Pediatric 74 (2010) 7–14

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International Journal of Pediatric Otorhinolaryngology

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Review article The role of HPV type in Recurrent Respiratory Papillomatosis

A.J. Donne a,*, L. Hampson b, J.J. Homer c, I.N. Hampson b a Department of Otolaryngology, Alder Hey Children’s NHS Foundation Trust, Eaton Road, Liverpool, L12 2AP, United Kingdom b University of Manchester Gynaecological Oncology Laboratories, St Mary’s Hospital, Hathersage Road, Manchester, M13 OJH, United Kingdom c Department of Otolaryngology, Manchester Royal Infirmary, Oxford Road, Manchester, M13 9WL, United Kingdom

ARTICLE INFO ABSTRACT

Article history: Objective: Human Papillomavirus (HPV) 6 and 11 are the aetiological agents responsible for Recurrent Received 20 May 2009 Respiratory Papillomatosis (RRP). There is general consensus that HPV11 results in more aggressive Received in revised form 29 August 2009 disease compared to HPV6. Accepted 3 September 2009 Method: Pubmed was searched using the terms respiratory papillomatosis, HPV 6 and HPV11. Available online 1 October 2009 Comparisons were made in the outcomes of HPV6 versus HPV11 positive RRP disease. Results: There are numerous sub-types or variants of both HPV6 and HPV11. These sub-types have Keywords: different activities at least in-vitro. The numbers of different HPV types within RRP tissue may be more Human Papillomavirus (HPV) extensive than initially appeared. This depends specifically upon the HPV types tested for. HPV6 HPV11 Conclusion: The clinical differences between HPV6 and HPV11 disease may not be accurately predictable Recurrent Respiratory Papillomatosis as these exist in numerous sub-types. Also, RRP tissue may contain more than one subtype or even be co-infected with other viruses that may influence outcome. In-vitro studies upon cell lines are a reasonable starting point for evaluation of these differences. ß 2009 Elsevier Ireland Ltd. All rights reserved.

Contents

1. Introduction ...... 7 2. HPV type (number), low and high risk ...... 8 3. Viral aetiology ...... 8 4. Dormant commensal HPV and sample testing reliability ...... 8 5. Structure of Human Papillomavirus ...... 9 6. HPV E6 and E7 proteins...... 10 7. Defining disease severity...... 10 7.1. Disease severity defined as high frequency of surgeries...... 11 7.2. Disease severity defined as need for tracheostomy...... 11 7.3. Disease severity defined as malignant transformation ...... 11 7.3.1. The sequence of malignant expression...... 11 7.3.2. HPV 6 and 11 in ...... 11 7.3.3. HPV 11 integration ...... 12 7.3.4. HPV 16 and 18 oncogenic potential ...... 12 7.4. Understanding the value of co-infection ...... 12 8. Conclusion...... 12 References...... 12

1. Introduction tract. It is caused by the so called ‘‘low risk’’ Human Papillomavirus (HPV) types 6 and 11. Contemporary opinion amongst otolar- Recurrent Respiratory Papillomatosis (RRP) is a disease in yngologists is that HPV 11 related disease is more aggressive than which squamous -like lesions occur within the respiratory HPV 6 [1] although this is not universally supported by the published data. If there were HPV type related differences in the * Corresponding author. severity of RRP, this would indicate that optimum choice of E-mail address: [email protected] (A.J. Donne). therapy could be dependent on the HPV type that is present.

0165-5876/$ – see front matter ß 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2009.09.004 8 A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14

However, this is not a simple problem since the prevalence of HPV of these variants confirmed differences between them as great as in both dormant pre-clinical and clinical conditions is variable and 190 fold [17]. In clinical terms, it is difficult to functionally link a the influence of co-infection with other HPV types has not been change in the LCR to viral pathogenesis although it is clear that this fully evaluated. can alter the activity of high-risk HPVs in cervical tumours [18] and low-risk HPV in condyloma accuminata and Buschke–Lowenstein 2. HPV type (number), low and high risk tumours [19]. Yet interestingly, a genetic nucleotide duplication within HPV11 has been identified that may potentially indicate a The Human Papillomavirus (HPV) family are small double more severe disease process in RRP [7]. stranded DNA viruses of approximately 8 Kb in size. HPV is a non- By the use of highly sensitive SYBR-green real-time PCR, HPV encapsulated with an icosahedral structure formed by 72 has been found in 100% of from RRP patients [20].Itis capsomeres. It affects characteristic regions of the body as a result clear that the sensitivity of technique used for HPV detection is of its predisposition for the stratified of either relevant although it is also important to analyse the viral sub type, cutaneous or mucosal surface. HPV infection therefore results in plus any variants that may be present. Seven different HPV sub- either clinically subtle commensal infection or (wart) types have been identified from papilloma tissue from RRP patients formation. The latter typically results in in the anogenital of which 28/47 cases were HPV6 and 11 [21]. One patient had six region (Condylomata acuminata), cutaneous warts, or the papil- and two had five different sub-types of HPV. Indeed others have loma of Recurrent Respiratory Papillomatosis. also shown that multiple HPV types occur in papillomas harvested There are around 130 different HPV types and these are broadly from RRP patients [22]. Furthermore, the viral copy number has characterised into the low risk (benign disease) or high-risk been estimated to be about 102–107 copies per mg of extracted (malignant disease potential) types where risk implies the sample DNA which is considerably higher than is found for HPV potential for malignant transformation. HPV types are classified positive of the and which contain less by genotype which is defined by the sequence of the viral L1 gene than 10 copies per mg of sample DNA. Interestingly HPV DNA copy [2]. The L1 region encodes for the major capsid protein and number seems to vary by several orders of magnitude during the demonstrates the greatest conservation. It is therefore best suited course of the disease [12] which, to some extent, could account for to construction of the family taxonomy [3]. The major HPV types the difficulty in detecting HPV DNA. Clearly this variance in HPV differ from each other by at least 10% [4] and each HPV type copy number could be prognostically important although the contains within it a family of ‘‘variants’’ that are characterised by relatively low numbers involved do not permit this type of differences in nucleotide sequence of approximately 2% in analysis. (See Table 1 for summary of proportions of RRP samples conserved and 5% in less conserved regions [4]. ‘‘Species’’ is a confirmed to contain HPV). term reserved for phylogenetic associations of different HPV types within a genus that demonstrates 60–70% sequence identity and 4. Dormant commensal HPV and sample testing reliability considerable biological similarity, such as HPV 6 and HPV 11 [5]. The prevalence of HPV in the normal larynx/respiratory tree is 3. Viral aetiology clearly difficult to gauge as this requires ethical approval to persons with no coincidental pathology and it would be difficult to In 1923 Ullmann originally confirmed the presence of an gain approval for such a study. A UK autopsy study of apparently infectious agent by injecting an extract of a laryngeal papilloma normal larynges, combined with oral sampling, indicated that 25% into his arm with the resultant development of papillomata [6]. may be HPV positive with 3/25 being positive for HPV 11 [23]. Subsequently it has been established that HPV is the causative Consequently, there has been a reliance on oral sampling to agent with the majority of studies demonstrating that either HPV6 measure prevalence, as this is more acceptable. However, even and/or HPV11 are present in most cases of RRP: 98% [7], 83% [8], with this anatomical site there is considerable variation in results 100% [9], 50% [10,11], 100% [12]. The observed differences in depending on the method of tissue sampling. A 3% sucrose detection rate are most likely related to the method of HPV DNA mouthwash versus three separate site buccal mucosal scrapes detection used. For example, Pignatari initially performed in-situ versus buccal mucosal biopsy in the same patient revealed 51%, 45% hybridisation and found HPV in 50% [13]. However, further studies and 12% HPV positive results [24]. The importance of these data is using PCR based techniques, detected HPV in 100% of cases [14].In the low figure obtained with biopsy which arguably should give 1982 Mounts identified only 20% to be positive but this work only the most reliable results. One interpretation of this could be that used HPV6 DNA probes [11]. Interestingly, the value of this report not all cells contain HPV and as the two former methods sample a was that it identified four different sub-types of HPV6 (HPV6c– larger area of mucosa they are more likely to be informative. In this HPV6f) by restriction endonuclease digestion analysis. The series 14% were HPV 6/11 positive and 26% were HPV 16 and/or 18 importance of this observation is that the variation in the positive. On meta-analysis 10% of normal oral mucosa has been effectiveness of RRP therapies could be in part due to possible found to contain high-risk HPV [25]. However, some individual differences in virulence of the different sub-types. Supporting reports were as high as 55% positive for HPV 16/18 which may be evidence comes from the observation that HPV16 E6 variants do associated with geographical differences [26]. Mucosal HPV testing appear to differ in their functional ability [15]. Furthermore, HLA (using swabs) has indicated that family members of children with type and HPV16 E6 variants may together have prognostic RRP do not have HPV in oral brushing [27]. Interestingly, 80% of the significance [16]. Initially, two sub-types of HPV11 were identified patients with multiple, as opposed to single sites of papillomas, which were designated HPV11a and b. HPV11b was only identified were positive for HPV in non-diseased sites [13]. Later work by the in genital condylomata accuminata [11]. As with the different sub- same group using PCR techniques to detect HPV in diseased and types of HPV6, those identified for HPV11 could have different non-diseased sites, indicated that 100% of the papillomas studied characteristics as regards virulence. were positive for HPV and 80–100% of the tracheo-bronchial tree This is potentially very significant since 19 HPV6 and 10 HPV11 was also positive whereas only 25% of the nasopharynx sites tested variant genomes have now been identified from worldwide were positive [14]. sampling. These variations were found in the Long Control Regions Given that RRP and genital warts are both caused by HPV6/11 it (LCR) of the viral genomes and even though most differences were is clearly relevant to consider the role of HPV viral types in the due to point mutations, functional assays of the enhancer activity latter. Almost 100% of genital warts (Condylomata accuminata) A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14 9

Table 1 Summary of HPV positivity and type in RRP lesions and technique use to identify HPV.

Reference Proportion Technique of HPV detection Numbers of patients HPV types HPV positive (%)

Gabbott et al. [7] 98 PCR 44/47 43% (HPV6) 55% (HPV11)

Pou et al. [8] 83 PCR 24/29 72% (HPV6) 10% (HPV11 and/or 16)

Duggan et al. [9] 100 DISH 9/9 44.5% (HPV6) 44.5% (HPV11) 11.% (HPV6 and 11)

Gissman et al. [10] 50 DNA hybridisation on extracted DNA 7/14 0% (HPV6) 50% (HPV11a)

Mounts et al. [11] 20 DNA hybridisation on extracted DNA 4/20 Only tested for HPV 6

Major et al. [12] 100 PCR and RE evaluation 10/10 60% (HPV6) 40% (HPV11)

Pignatari et al. [13] 50 DISH to HPV6/11 6/12 50% (HPV6 and/or 11) Smith et al. [14] 100 PCR amplification and DNA hybridisation 5/5 20% (HPV6) 60%(HPV11) 20%(HPV6 and 11)

Penaloza-Plascencia et al. [21] 100 PCR 47/47 19% (HPV6) 28% (HPV11) 13% (HPV6 and 11) 40% (other HPV)

Dragonov et al. [20] 100 Real-time PCR 23/23 23.8% (HPV6) 61.9% (HPV11) 14.3% (HPV6 and 11) contain either HPV 6 or 11 with HPV 6 being the most prevalent, HPV 11 with HPV 6b DNA sequences which showed strong although 20–50% also have high-risk HPV co-infection [28],[29]. sequence conservation even in the non-coding region (7300– Treatment for genital warts is not as arduous as RRP as this 7500 bp). Alignment of HPV6b E6 and HPV11 E6 amino-acid typically requires no general anaesthetic and they tend to persist sequences using NCBI BLAST shows considerable homology with for 12–18 months before spontaneous resolution [30]. A small 122/150 amino acids conserved (Fig. 1). minority have more persistent disease which carries an increased Even HPV16 has five distinct phylogenetic lineages classified risk of developing cervical yet this shows no preference according to their presumed origin: European (E), Asian (A), Asian- for either HPV11 or HPV6 [31,32]. American (AA), African-1(Af1) and African-2 (Af2) [40,41,42]. Dormant HPV is important since whether or not remission of These differences, which are manifested predominantly through RRP occurs, it is possible to demonstrate HPV DNA in mucosa that variations in the E6 protein at the N-terminal end, appear to alter appears otherwise histologically normal in tissue adjacent to the activity of E6 in functional assays carried out in human affected tissue or at sites of remission [33,34,35]. Indeed rates of keratinocytes [15]. How is this possible? E6 has been described as detection of dormant HPV in macroscopically normal sites of RRP an intrinsically disordered protein (IDP) which implies that small patients can be as high as 61% [14] and the factors that trigger the changes in the protein can have profound effects on its tertiary development of papilloma from normal HPV containing mucosa structure [43]. In support of this, a recent study has shown that a are unknown. In a United States survey reported by Derkay [36] single amino acid substitution can actually convert high-risk E6 both children and adults have been shown to develop RRP into a tumour suppressor [44]. Thus it is hypothesised that associated with infection with human immune deficiency virus different HPV16 variants may ultimately produce different (HIV). This study also noted a child who developed RRP following pathological effects although this is controversial. organ transplant and subsequent immuno-suppressive therapy. HPV has only eight viral genes compared to human cells which PCR analysis of DNA obtained by vaginal lavage has shown that 79% can express >25,000, this means that each viral gene product/ of HIV positive women harbour a large variety of HPV types [37]. protein must be, by necessity, extremely multifunctional. These findings indicate that it is probable that disease remission is The HPV genome can be categorised into three main domains: influenced by immunological status, though no clear pattern has upstream regulatory regions (URR) or long control region (LCR) yet been found. However, a recent study has identified that which are non-coding, early region (E) open reading frames () children with RRP have significantly reduced CD4/CD8 ratios and a and late (L) region open reading frames. Early and late broadly poor lymphocyte response to mitogen stimulation. This indicates relates to the early or late promoter initiation. The URR is that an impaired cell mediated immunity may be responsible for approximately 1 kb and contains binding sites for a number of the frequent recurrence of papilloma in patients [38]. transcriptional activators that are either positively or negatively regulating [45]. The six early proteins affect cell growth and 5. Structure of Human Papillomavirus function whereas the two late proteins make up the viral capsid protein structure. The HPV genome encodes genes classified as early expressing (E The HPV genome is differentially expressed depending on its prefix) and late expressing (L prefix). Indeed, all the E and L position within the differentiating epithelium. E6, E7, E1 and E2 proteins from types HPV6 to 11 have an extremely high level of are transcribed following early promoter initiation [46,47].The sequence homology. Dartmann [39] published the nucleotide late promoter is activated in the productive phase of the viral life sequence of HPV 11 and carried out a DOT matrix comparison of cycle resulting in high level transcription of E1, E2, E4, E5, L1 and 10 A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14

Fig. 1. NCBI BLAST analysis of HPV E6. Black font indicates HPV6b E6 amino acid sequence. The red font letters are identified differences in amino acids in HPV11 E6. HPV6b accession number NC_001355 . HPV11 accession number M14119 . (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)

L2 [46], and ultimately high-level amplification of the viral It is clear that the structure of the E6 protein will affect its genome. This is known as the vegetative phase of the viral life function. Indeed, the presence of specific amino-acid chains cycle. Additionally, there are promoters designated P1, P2 and P3. (termed zinc-fingers) on low and high-risk E6 proteins suggests These initiate expressions of E6 [48],E7[49] and E1 (and E1^E4 that both can bind to DNA and potentially influence transcription. fusion protein) [48], respectively. The sites of the promoters Many viruses compromise the function of p53 (tumour have been represented diagrammatically in the HPV 6b gene in suppressor protein) in order to effectively subvert control of the Fig. 2. Other HPV types have the same sequence of genes but cell cycle [50]. p53 functions to sense uncontrolled cell division differ slightly in the nucleotide number at the beginning of the and to stimulate repair of damaged DNA. If persistent uncontrolled genes. cell division occurs or if extensive DNA damage is present p53 induces apoptosis of the affected cell. High-risk E6 promotes the 6. HPV E6 and E7 proteins rapid degradation of p53 through the ubiquitin-proteosome degradation pathway. Conceptually HPV E6 therefore hijacks the E6 and E7 are arguably the most important ‘early’ gene products cells own proteolytic machinery since E6AP does not normally which respectively target the p53 and Rb (retinoblastoma) tumour recognise p53 as a target for ubiquitinisation [51]. Low-risk E6 suppressor proteins to suppress apoptosis and de-regulate cell abrogates the function of p53 in in-vivo experiments albeit less growth control. The HPV6b and HPV11 E6 proteins each consist of efficiently that its high-risk counterpart [52]. 150 amino-acids and show strong nucleotide sequence conserva- tion even in the non-coding region (7300–7500 bp) [39]. Align- 7. Defining disease severity ment of HPV6b E6 and HPV11 E6 amino-acid sequences using NCBI BLAST illustrates this homology (Fig. 1). Indeed, protein structure The virulence of HPV is manifest in the severity of the clinical predictive software does not demonstrate significant differences condition and this obviously depends upon its component genes. between these two E6 proteins. Yet high-risk HPV16 E6 amino acid The clinical severity of RRP has been defined in numerous ways but sequence is different as it contains 158 amino acids and there are typically as the frequency of surgeries necessary to keep the airway significant differences between HPV6b E6 and HPV16 E6. patent. The problem with this indicator is that it is dependent on

Fig. 2. Summary of HPV6b gene relationship. A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14 11 the surgeons’ opinion of when to operate and extent of surgery. requiring tracheostomy seem to represent a select group with Indeed the frequent removal of small papillomas may not be more aggressive disease before having the tracheostomy. These patients aggressive than the relatively infrequent removal of larger typically have widespread disease at onset, present at a younger growths. Other indicators of severity are arguably the need for age and 50% develop distal spread (mainly to the or stoma) tracheostomy and malignant progression, with the latter strongly [35]. However, there does appear to be some indication that HPV11 implying a true biological difference. Numerous staging systems is more likely to result in tracheostomy compared to HPV6 [58].A exist but they all seem too complex for routine use by the surgeon. study of 19 RRP patients revealed 7/10 HPV11 patients required They more probably serve as research tools as it is not known if tracheostomy compared to 2/9 HPV6 patients. Overall if HPV11 there is a specific change in prognosis which occurs with produces more aggressive disease than HPV6 the former type papillomatous involvement of specific regions of the airway, should be more prevalent in children (as RRP is more aggressive in (except pulmonary involvement). children). Indeed, this HPV prevalence is implied in published data [59], [60]. 7.1. Disease severity defined as high frequency of surgeries 7.3. Disease severity defined as malignant transformation The previously discussed frequency of surgeries required to maintain a patent airway is one potential indicator of disease 7.3.1. The sequence of malignant expression severity. Disease remission can occur at any stage and the duration Both low and high-risk HPVs are known to be associated with of remission is extremely variable [53]. Laryngeal disease is more malignancy although high-risk types are considerably more likely likely to result in remission unlike pulmonary disease that is often to result in transformation, hence the nomenclature, ‘‘high risk.’’ fatal. It has often been stated that the onset of puberty may bring The low risk HPV genome typically exists as a circular episomal about the remission in juvenile-onset disease but there is no DNA that does not integrate into the host DNA unlike high-risk evidence to support this [54,55]. It follows (though perhaps virus which often integrates but may also exist episomally. It is indirectly) that extent of disease is therefore also important. generally accepted that integration of high-risk HPV DNA into the Contemporary opinion amongst otolaryngologists is that HPV11 host genome is associated with a higher frequency of malignant disease is more aggressive than HPV6 [1] (See summary Table 2) transformation [61] although integration does not guarantee although work by Penaloza-Plascencia identified seven different malignant change [62]. Clearly any transformation event is further HPV types in 47 patients and did not identify any difference enhanced by E6 and E7 dependent inactivation of the host tumour between different HPV types. Most importantly it identified that suppressor proteins p53 and pRb. Significantly integration of HPV HPV16 was the most common type present in 39 cases (83%), into the host genome very often disrupts the E2 open reading though often it was present with other HPV types. This study frame. E2 has DNA binding activity and is an important negative indicates that it is not just the individual HPV type present that is transcriptional regulatory factor controlling expression of E6/E7, important but rather may the mixture of types that are present in hence inactivation of E2 increases the expression of E6 and E7 [63]. an individual patient. Significantly most diagnostic tests in current use only identify HPV6, 11, 16, 18 whereas an appreciation of any 7.3.2. HPV 6 and 11 in malignancy other HPV types present may enable better prediction of prognosis. Even though both HPV 6 and 11 are considered to be low risk, Finally recent published data indicates that pregnancy is data from clinical cases indicates that HPV 11 does demonstrate a accompanied by excessive growth of papillomata in HPV11. greater probability of producing malignant changes. However, 100% of women with HPV11 were affected in the study compared even the potentially more benign HPV 6 has also been documented to 16.7% of HPV6 women (P = 0.001) [56]. These data indicate that to cause malignant change e.g. HPV6a causing carcinoma [64], there must be clinical differences between the HPV types which HPV 6 tonsillar carcinoma [65], malignant progression in HPV6 might allow targeted treatment according to HPV type. laryngeal papilloma [66] and laryngeal carcinoma [67]. Malignant transformation to is an 7.2. Disease severity defined as need for tracheostomy uncommon outcome and the incidence varies between series. In adult-onset RRP, a large series of 102 cases yielded a rate of 3% [68] Tracheostomy may be required when there is serious risk of but rates of up to 6% have been reported [69]. In juvenile-onset RRP laryngeal airway obstruction. The clinical evaluation in this setting malignant transformation is very rare therefore any such case is is at least partly subjective and some surgeons advocate repeated worthy of further evaluation. Derkay [36] reported 13 cases of microlaryngoscopies as an alternative [55]. Indeed, tracheostomy malignant transformation in a total of 1193 patients (<1% rates vary between 13% and 21% in juvenile-onset RRP [33], [36], transformation rate). Other paediatric cases in the literature are [55],[57] and 4% and 6% in adult-onset RRP [36], [57]. Patients only occasionally reported [70,71,72]. As RRP is relatively

Table 2 Summary of papers commenting upon HPV types and prognosis.

Reference HPV6 vs 11 difference detected Numbers of patients (6/11/both) HPV test

Penaloza-Plascencia et al. [21] No 47 (10/13/5) PCR Gabbott et al. [7] No 44 (19/24/1) PCR Wiatrak et al. [1] Yes 58 (31/23/4) PCR and ISH Buchinsky et al. [59] Yes 118 (71/47) PCR and Restriction Fragment Length Polymorphism (RLFP) Maloney et al. [96] Yes 15 (4/4/7) ELISA and PCR Draganov et al. [20] Yes 21 (5/13/3) PCR Mounts and Kashima [95] Yes 21 (21/?/?)a ISH Rabah et al. [97] Yes 61 (29/32) PCR and ISH Rimell et al. [91] Yes 19 (9/6/4) PCR Gerein et al. [58] Yes 31 (17/14) Not disclosed

a Only HPV6 was assessed and not HPV11. HPV6c was more likely associated with more extensive disease or tracheostomy; HPV6d only occurred in non-Caucasians and indicated geographical origin may be important. 12 A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14 uncommon it may be valuable to comment on cervical HPV as the trachea is far less likely to be involved in papilloma infections as cervical HPV is common and there are effective formation. established cervical programs that ensure good popula- tion sampling. Indeed, HPV 6 and 11 are frequently associated with 7.3.4. HPV 16 and 18 oncogenic potential low-grade cervical squamous intraepithelial lesions (LSIL), 8.1% The prevalence of high-risk HPV in tumours is variable. In and 3.2% are HPV 6 and 11 positive respectively on meta-analysis cervical carcinoma 70–90% of European cases contain HPV 16 or 18 review [73]. However, the proportion of co-infection was not [86], [87], whereas, about 50% of laryngeal [67], 40% of posterior determined and this data suggests that HPV11 may be less tongue [88] and up to 74% of tonsil carcinomas [26] are associated aggressive than HPV6 in inducing cervical . with high-risk HPV. Certainly, for tonsil tumours HPV is considered Risk factors for malignant transformation in RRP include an important aetiological factor. The prognosis of HPV tonsil previous radiotherapy [74], smoking and HPV type [1]. Smoking tumours is more favourable and may reflect greater sensitivity to has been shown to influence expression of p53 [75], an important chemotherapy [89] which is consistent with the therapeutic feature of malignant transformations in numerous tissues. response of HPV positive cervical tumours which have a However, recent work on Taiwanese patients with RRP has statistically significantly more favourable outcome than HPV demonstrated that the ability to detect HPV may be the most negative tumours [90]. important factor for malignant progression. Surprisingly, the lack of PCR-detectable HPV within papillomatous lesions increases the 7.4. Understanding the value of co-infection risk of malignant transformation [76]. The explanation of this phenomenon could be that integration of HPV into the host DNA Unlike children, co-infection with virus (HSV) may disrupt E2 and abort the L protein dependent replicative stage and Epstein–Barr virus (EBV) in adults may lead to more aggressive of the virus life cycle. This would have the effect of drastically RRP [91]. Indeed, a PCR based study failed to detect cytomega- reducing the viral genome copy number yet enhancing E6 lovirus (CMV) and HSV in from paediatric RRP patients expression. HPV 11, HPV 16 and HPV 18 are more associated [91]. However, another study showed a correlation between a poor with malignant transformation than HPV 6 [8,75,77]. However, as prognosis in 17/29 patients of which 11/17 had co-infections. HSV already stated, transformation can still be associated with HPV 6 and EBV present in 50% and 12.5%, respectively [8]. Yet infection [69],[66]. It is not fully understood how HPV mediated interestingly, is not effective in reducing the rate of RRP. malignant transformation takes place and it has been proposed Another intriguing possibility is that co-infection with adeno- that this could be influenced by tumour suppressor genes or associated virus type 2 (AAV2) may have implications for both the oncogenes being at or near HPV integration sites. development and prognosis of RRP. AAV2 is a helper dependent human parvovirus which may have an inhibitory effect on the 7.3.3. HPV 11 integration development of HPV associated cervical from clinical In general, from work on cervical lesions, low risk HPV 6 and 11 studies [92], [93]. Furthermore, in-vitro studies have confirmed exist in episomal forms irrespective of grade of cervical lesion from that AAV2 inhibits HPV16 cellular transformation [94]. which they originated. HPV16 and 18 are more likely to integrate the higher the CIN grade [78]. The integration process should 8. Conclusion therefore be linked to malignant change however many workers have demonstrated contrary evidence [79,80,81]. i.e. HPV16 The opinion that HPV 11 related RRP is more aggressive than present in episomal form in malignant tissue. Therefore, the HPV 6 mediated disease is supported by the clinical evidence and integration process itself may not be the direct cause of malignant even as early as 1984 [95] it was clear that different subtypes of transformation. HPV 6 may have differing degrees of virulence. Clarifying the HPV11 does seem to deliver a higher rate of progression to underlying clinical differences between HPV6 and HPV11 are malignancy [82], however, as previously discussed there are difficult, since this could also involve differences between HPV some documented cases of HPV 6 associated laryngeal malig- type specific variants which are compounded by co-infection with nancy, [67]. Indeed, in these carcinomas HPV 6 was found to other HPV types neither of which are definitively tested for. have integrated in only 20% with the remainder being episomal. Furthermore, the involvement of other non-HPV related infections Clearly, these HPV6 associated carcinomas could have resulted in the pathogenesis of RRP cannot be excluded. The relatively low from an alternative aetiology, although this point merits note as numbers of patients with RRP clearly hamper studies that might oral carcinomas have demonstrated episomal HPV 16 with the identify genuine disease associated differences and this is same virus type detectable in normal adjacent tissue [83], [84] additionally complicated by the previously discussed potential i.e. not all high-risk HPV results in transformation. Interestingly, differences in geographical variation between HPV types. the same HPV type was detected in normal laryngeal mucosa adjacent to HPV 6 associated laryngeal malignancies suggesting References infection with only one type. Furthermore, one case of tongue squamous cell carcinoma contained episomal HPV 6 rather than [1] B.J. Wiatrak, D.W. Wiatrak, T.R. Broker, et al., Recurrent respiratory papilloma- tosis: a longitudinal study comparing severity associated with human papilloma HPV 11 although this could be coincidental. The lack of low risk viral types 6 and 11 and other risk factors in a large pediatric population, HPV integration in general suggests that there may be other Laryngoscope 114 (11 Pt 2 (Suppl 104)) (2004) 1–23. factors that stimulate increased expression of E6/E7 in addition [2] E.M. de Villiers, Papillomavirus and HPV typing, Clin. Dermatol. 15 (March (2)) to the previously discussed integration dependent, disruption of (1997) 199–206. [3] H.U. Bernard, S.Y. Chan, M.M. Manos, et al., Identification and assessment of E2. A study on the latent infection of respiratory mucosa of RRP known and novel human papillomaviruses by polymerase chain reaction ampli- patients found HPV DNA to be present to the same extent in fication, restriction fragment length polymorphisms, nucleotide sequence, and both adjacent normal laryngeal mucosa and normal tracheal phylogenetic algorithms, J. Infect. Dis. 170 (November (5)) (1994) 1077–1085. [4] H.U. Bernard, I.E. Calleja-Macias, S.T. Dunn, Genome variation of human papillo- mucosa. This study on HPV6 and HPV 11 followed 61 patients mavirus types: phylogenetic and medical implications, Int. J. Cancer 118 (March for 3–18 years and showed no correlation between type and (5)) (2006) 1071–1076. virulence [85]. Despite the small numbers of patients involved, [5] E.M. de Villiers, C. Fauquet, T.R. Broker, et al., Classification of papillomaviruses, Virology 324 (June (1)) (2004) 17–27. this work indicated a lower rate of papilloma occurrence in [6] E.V. Ullman, On the aetiology of laryngeal papilloma, Acta Otolaryngol. 5 (1923) tracheal mucosa and no difference in HPV type. This is important 317. A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14 13

[7] M. Gabbott, Y.E. Cossart, A. Kan, et al., Human papillomavirus and host variables as [36] C.S. Derkay, Task force on recurrent respiratory papillomas. A preliminary report, predictors of clinical course in patients with juvenile-onset recurrent respiratory Arch. Otolaryngol. Head Neck Surg. 121 (December (12)) (1995) 1386–1391. papillomatosis, J. Clin. Microbiol. 35 (December (12)) (1997) 3098–3103. [37] T.R. Broker, G. Jin, A. Croom-Rivers, et al., Viral latency – the papillomavirus [8] A.M. Pou, F.L. Rimell, J.A. Jordan, et al., Adult respiratory papillomatosis: human model, Dev. Biol. (Basel) 106 (2001) 443–451. papillomavirus type and viral coinfections as predictors of prognosis, Ann. Otol. [38] Y. Stern, A. Felipovich, R.T. Cotton, et al., Immunocompetency in children with Rhinol. Laryngol. 104 (October (10 Pt 1)) (1995) 758–762. recurrent respiratory papillomatosis: prospective study, Ann. Otol. Rhinol. Lar- [9] M.A. Duggan, M. Lim, M.J. Gill, et al., HPV DNA typing of adult-onset respiratory yngol. 116 (March (3)) (2007) 169–171. papillomatosis, Laryngoscope 100 (June (6)) (1990) 639–642. [39] K. Dartmann, E. Schwarz, L. Gissmann, et al., The nucleotide sequence and genome [10] L. Gissmann, L. Wolnik, H. Ikenberg, et al., Human papillomavirus types 6 and 11 organization of human papilloma virus type 11, Virology 151 (May (1)) (1986) DNA sequences in genital and laryngeal papillomas and in some cervical , 124–130. Proc. Natl. Acad. Sci. U.S.A. 80 (January (2)) (1983) 560–563. [40] L. Ho, S.Y. Chan, R.D. Burk, et al., The genetic drift of human papillomavirus type 16 [11] P. Mounts, K.V. Shah, H. Kashima, Viral etiology of juvenile- and adult-onset is a means of reconstructing prehistoric viral spread and the movement of ancient squamous papilloma of the larynx, Proc. Natl. Acad. Sci. U.S.A. 79 (September (17)) human populations, J. Virol. 67 (November (11)) (1993) 6413–6423. (1982) 5425–5429. [41] T. Yamada, C.M. Wheeler, A.L. Halpern, et al., Human papillomavirus type 16 [12] T. Major, K. Szarka, I. Sziklai, et al., The characteristics of human papillomavirus variant lineages in United States populations characterized by nucleotide DNA in head and neck cancers and papillomas, J. Clin. Pathol. 58 (January (1)) sequence analysis of the E6, L2, and L1 coding segments, J. Virol. 69 (December (2005) 51–55. (12)) (1995) 7743–7753. [13] S. Pignatari, E.M. Smith, S.D. Gray, et al., Detection of human papillomavirus [42] T. Yamada, M.M. Manos, J. Peto, et al., Human papillomavirus type 16 sequence infection in diseased and nondiseased sites of the in recurrent variation in cervical cancers: a worldwide perspective, J. Virol. 71 (March (3)) respiratory papillomatosis patients by DNA hybridization, Ann. Otol. Rhinol. (1997) 2463–2472. Laryngol. 101 (May (5)) (1992) 408–412. [43] V.N. Uversky, A. Roman, C.J. Oldfield, et al., Protein Intrinsic Disorder and Human [14] E.M. Smith, S.S. Pignatari, S.D. Gray, et al., Human papillomavirus infection in Papillomaviruses: Increased Amount of Disorder in E6 and E7 Oncoproteins from papillomas and nondiseased respiratory sites of patients with recurrent respira- High Risk HPVs, J. Proteome. Res. 5 (August (8)) (2006) 1829–1842. tory papillomatosis using the polymerase chain reaction, Arch. Otolaryngol. Head [44] T. Ristriani, S. Fournane, G. Orfanoudakis, et al., A single-codon mutation converts Neck Surg. 119 (May (5)) (1993) 554–557. HPV16 E6 oncoprotein into a potential tumor suppressor, which induces p53- [15] Y. Asadurian, H. Kurilin, H. Lichtig, et al., Activities of human papillomavirus 16 E6 dependent senescence of HPV-positive HeLa cells, Oncogene 28 natural variants in human keratinocytes, J. Med. Virol. 79 (November (11)) (2007) (February (5)) (2009) 762–772. 1751–1760. [45] C.M. Hebner, L.A. Laimins, Human papillomaviruses: basic mechanisms of patho- [16] I. Zehbe, J. Mytilineos, I. Wikstrom, et al., Association between human papillo- genesis and oncogenicity, Rev. Med. Virol. 16 (March (2)) (2006) 83–97. mavirus 16 E6 variants and human leukocyte antigen class I polymorphism in [46] M. Hummel, J.B. Hudson, L.A. Laimins, Differentiation-induced and constitutive cervical cancer of Swedish women, Hum. Immunol. 64 (May (5)) (2003) 538–542. transcription of human papillomavirus type 31b in cell lines containing viral [17] P.A. Heinzel, S.Y. Chan, L. Ho, et al., Variation of human papillomavirus type 6 episomes, J. Virol. 66 (October (10)) (1992) 6070–6080. (HPV-6) and HPV-11 genomes sampled throughout the world, J. Clin. Microbiol. [47] P.J. Morris, C.L. Dent, C.J. Ring, et al., The octamer binding site in the HPV16 33 (July (7)) (1995) 1746–1754. regulatory region produces opposite effects on gene expression in cervical [18] C. Kammer, M. Tommasino, S. Syrjanen, et al., Variants of the long control region and non-cervical cells, Nucleic Acids Res. 21 (February (4)) (1993) 1019– and the E6 oncogene in European human papillomavirus type 16 isolates: 1023. implications for cervical disease, Br. J. Cancer 86 (January (2)) (2002) 269–273. [48] L.T. Chow, M. Nasseri, S.M. Wolinsky, et al., Human papillomavirus types 6 and 11 [19] A. Rubben, S. Beaudenon, M. Favre, et al., Rearrangements of the upstream mRNAs from genital condylomata acuminata, J. Virol. 61 (August (8)) (1987) regulatory region of human papillomavirus type 6 can be found in both 2581–2588. Buschke-Lowenstein tumours and in condylomata acuminata, J. Gen. Virol. 73 [49] D. Smotkin, H. Prokoph, F.O. Wettstein, Oncogenic and nononcogenic human (December (Pt 12)) (1992) 3147–3153. genital papillomaviruses generate the E7 mRNA by different mechanisms, J. Virol. [20] P. Draganov, S. Todorov, I. Todorov, et al., Identification of HPV DNA in patients 63 (March (3)) (1989) 1441–1447. with juvenile-onset recurrent respiratory papillomatosis using SYBR Green real- [50] E.A. Slee, D.J. O’Connor, X. Lu, To die or not to die: how does p53 decide? Oncogene time PCR, Int. J. Pediatr. Otorhinolaryngol. 70 (March (3)) (2006) 469–473. 23 (April (16)) (2004) 2809–2818. [21] M. Penaloza-Plascencia, H. Montoya-Fuentes, S.E. Flores-Martinez, et al., Mole- [51] K. Butz, C. Denk, A. Ullmann, et al., Induction of apoptosis in human papilloma- cular identification of 7 human papillomavirus types in recurrent respiratory viruspositive cancer cells by peptide aptamers targeting the viral E6 oncoprotein, papillomatosis, Arch. Otolaryngol. Head Neck Surg. 126 (September (9)) (2000) Proc. Natl. Acad. Sci. U.S.A. 97 (June (12)) (2000) 6693–6697. 1119–1123. [52] V. Band, S. Dalal, L. Delmolino, et al., Enhanced degradation of p53 protein in HPV- [22] P. Dickens, G. Srivastava, S.L. Loke, et al., Human papillomavirus 6,11, and 16 in 6 and BPV-1 E6-immortalized human mammary epithelial cells, EMBO J. 12 (May laryngeal papillomas, J. Pathol. 165 (November (3)) (1991) 243–246. (5)) (1993) 1847–1852. [23] D.A. Nunez, S.M. Astley, F.A. Lewis, et al., Human papilloma viruses: a study of their [53] J.N. Evans, Recurrent Respiratory Papillomatosis, 6th Edition, W. G. Scott-Brown’s prevalence in the normal larynx, J. Laryngol. Otol. 108 (April (4)) (1994) 319–320. Otolaryngology, vol. 4, Butterworth-Heinemann Ltd., 1996, pp. 1–5 Chapter 23. [24] G. Lawton, S. Thomas, J. Schonrock, et al., Human papillomaviruses in normal oral [54] D.J. Doyle, G.J. Gianoli, T. Espinola, et al., Recurrent respiratory papillomatosis: mucosa: a comparison of methods for sample collection, J. Oral. Pathol. Med. July juvenile versus adult forms, Laryngoscope 104 (May (5 Pt 1)) (1994) 523–527. (21) (6) (1992) 265–269. [55] B. Benjamin, D.S. Parsons, Recurrent respiratory papillomatosis: a 10 year study, J. [25] C.S. Miller, B.M. Johnstone, Human papillomavirus as a risk factor for oral Laryngol. Otol. 102 (November (11)) (1988) 1022–1028. squamous cell carcinoma: a meta-analysis, 1982-1997, Oral. Surg. Oral Med. [56] V. Gerein, I.L. Soldatski, N. Babkina, et al., Children and partners of patients with Oral Pathol. Oral Radiol. Endod. 91 (June (6)) (2001) 622–635. recurrent respiratory papillomatosis have no evidence of the disease during long- [26] Z.Y. Zhang, P. Sdek, J. Cao, et al., Human papillomavirus type 16 and 18 DNA in oral term observation, Int. J. Pediatr. Otorhinolaryngol. 70 (December (12)) (2006) squamous cell carcinoma and normal mucosa, Int. J. Oral. Maxillofac. Surg. 33 2061–2066. (January (1)) (2004) 71–74. [57] H. Lindeberg, O. Elbrond, Laryngeal papillomas: the epidemiology in a Danish [27] J.D. Sun, R.A. Weatherly, C.F. Koopmann Jr., et al., Mucosal swabs detect HPV in subpopulation 1965–1984, Clin. Otolaryngol. Allied. Sci. 15 (April (2)) (1990) laryngeal papillomatosis patients but not family members, Int. J. Pediatr. Otorhi- 125–131. nolaryngol. 53 (June (2)) (2000) 95–103. [58] V. Gerein, E. Rastorguev, J. Gerein, et al., Incidence, age at onset, and potential [28] C.J. Lacey, Therapy for genital human papillomavirus-related disease, J. Clin. Virol. reasons of malignant transformation in recurrent respiratory papillomatosis 32 (March (Suppl 1)) (2005) S82–S90. patients: 20 years experience, Otolaryngol. Head Neck Surg. 132 (March (3)) [29] P. Vandepapeliere, R. Barrasso, C.J. Meijer, et al., Randomized controlled trial of an (2005) 392–394. adjuvanted human papillomavirus (HPV) type 6 L2E7 : infection of [59] F.J. Buchinsky, J. Donfack, C.S. Derkay, et al., Age of child, more than HPV type, is external anogenital warts with multiple HPV types and failure of therapeutic associated with clinical course in recurrent respiratory papillomatosis, PLoS ONE vaccination, J. Infect. Dis. 192 (December (12)) (2005) 2099–2107. 3 (5) (2008) e2263. [30] A.B. Jenson, R.J. Kurman, W.D. Lancaster, Tissue effects of and host response to [60] C.M. Carvalho, L. Huot, A.L. Charlois, et al., Prognostic factors of recurrent human papillomavirus infection, Dermatol. Clin. 9 (April (2)) (1991) 203–209. respiratory papillomatosis from a registry of 72 patients, Acta Otolaryngol. [31] H.X. Ji, S. Syrjanen, K. Syrjanen, et al., In situ hybridization analysis of HPV DNA in (February) (2009) 1–9. cervical precancer and cervical cancers from China, Arch. Gynecol. Obstet. 247 (1) [61] S. Schneider-Maunoury, O. Croissant, G. Orth, Integration of human papilloma- (1990) 21–29. virus type 16 DNA sequences: a possible early event in the progression of genital [32] S.R. Ghaffari, T. Sabokbar, H. Mollahajian, et al., Prevalence of human papilloma- tumors, J. Virol. 61 (October (10)) (1987) 3295–3298. virus genotypes in women with normal and abnormal cervical cytology in Iran, [62] K.B. Choo, C.C. Pan, M.S. Liu, et al., Presence of episomal and integrated human Asian Pac. J. Cancer Prev. 7 (October (4)) (2006) 529–532. papillomavirus DNA sequences in cervical carcinoma, J. Med. Virol. 21 (February [33] R.R. Cole, C.M. Myer III, R.T. Cotton, in children with recurrent (20) (1987) 101–107. respiratory papillomatosis, Head Neck 11 (May (3)) (1989) 226–230. [63] G. Steger, S. Corbach, Dose-dependent regulation of the early promoter of human [34] Y. Stern, J.E. McCall, J.P. Willging, et al., Spontaneous respiration anesthesia for papillomavirus type 18 by the viral E2 protein, J. Virol. 71 (January (1)) (1997) 50– respiratory papillomatosis, Ann. Otol. Rhinol. Laryngol. 109 (January (1)) (2000) 58. 72–76. [64] T.P. DiLorenzo, A. Tamsen, A.L. Abramson, et al., Human papillomavirus type 6a [35] A.M. Shapiro, F.L. Rimell, D. Shoemaker, et al., Tracheotomy in children with DNA in the lung carcinoma of a patient with recurrent laryngeal papillomatosis is juvenile-onset recurrent respiratory papillomatosis: the Children’s Hospital of characterized by a partial duplication, J. Gen. Virol. 73 (February (Pt 2)) (1992) Pittsburgh experience, Ann. Otol. Rhinol. Laryngol. 105 (January (1)) (1996) 1–5. 423–428. 14 A.J. Donne et al. / International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14

[65] J.A. Bercovich, C.R. Centeno, O.G. Aguilar, et al., Presence and integration of human [82] P.M. Reidy, H.H. Dedo, R. Rabah, et al., Integration of human papillomavirus type papillomavirus type 6 in a tonsillar carcinoma, J. Gen. Virol. 72 (October (Pt 10)) 11 in recurrent respiratory papilloma-associated cancer, Laryngoscope 114 (1991) 2569–2572. (November (11)) (2004) 1906–1909. [66] A.P. Zarod, J.D. Rutherford, G. Corbitt, Malignant progression of laryngeal papil- [83] R.E. Howell, L. Gallant, Human papillomavirus type 16 in an oral squamous loma associated with human papilloma virus type 6 (HPV-6) DNA, J. Clin. Pathol. carcinoma and its metastasis, Oral. Surg Oral. Med. Oral Pathol. 74 (November 41 (March (3)) (1988) 280–283. (5)) (1992) 620–626. [67] A. Venuti, V. Manni, R. Morello, et al., Physical state and expression of human [84] M. Bouda, V.G. Gorgoulis, N.G. Kastrinakis, et al., High risk’’ HPV types are papillomavirus in laryngeal carcinoma and surrounding normal mucosa, J. Med. frequently detected in potentially malignant and malignant oral lesions, but Virol. 60 (April (4)) (2000) 396–402. not in normal oral mucosa, Mod. Pathol. 13 (June (6)) (2000) 644–653. [68] J. Klozar, M. Taudy, J. Betka, et al., Laryngeal papilloma – precancerous condition? [85] A.L. Abramson, M. Nouri, V. Mullooly, et al., Latent Human Papillomavirus Acta Otolaryngol. Suppl. 527 (1997) 100–102. infection is comparable in the larynx and trachea, J. Med. Virol. 72 (March (3)) [69] C. Hartley, J. Hamilton, A.R. Birzgalis, et al., Recurrent respiratory papillomatosis – (2004) 473–477. the Manchester experience, 1974–1992, J. Laryngol. Otol. 108 (March (3)) (1994) [86] D.J. McCance, M.J. Campion, P.K. Clarkson, et al., Prevalence of human papillo- 226–229. mavirus type 16 DNA sequences in cervical intraepithelial neoplasia and invasive [70] D. Orphanidou, K. Dimakou, P. Latsi, et al., Recurrent respiratory papillomatosis carcinoma of the cervix, Br. J. Obstet Gynaecol. 92 (November (11)) (1985) 1101– with malignant transformation in a young adult, Respir. Med. 90 (January (1)) 1105. (1996) 53–55. [87] M. Durst, L. Gissmann, H. Ikenberg, et al., A papillomavirus DNA from a cervical [71] D. Solomon, R.R. Smith, H.K. Kashima, et al., Malignant transformation in non- carcinoma and its prevalence in cancer biopsy samples from different geographic irradiated recurrent respiratory papillomatosis, Laryngoscope 95 (August (8)) regions, Proc. Natl. Acad. Sci. U.S.A. 80 (June (12)) (1983) 3812–3815. (1985) 900–904. [88] L. Dahlgren, H.M. Dahlstrand, D. Lindquist, et al., Human papillomavirus is more [72] H.M. Matsuba, S.E. Thawley, G.J. Spector, et al., Laryngeal epidermoid carcinoma common in base of tongue than in mobile tongue cancer and is a favorable associated with juvenile laryngeal papillomatosis, Laryngoscope 95 (October prognostic factor in base of tongue cancer patients, Int. J. Cancer 112 (December (10)) (1985) 1264–1266. (6)) (2004) 1015–1019. [73] G.M. Clifford, R.K. Rana, S. Franceschi, et al., Human papillomavirus genotype [89] W. Li, C.H. Thompson, C.J. O’Brien, et al., Human papillomavirus positivity predicts distribution in low-grade cervical lesions: comparison by geographic region and favourable outcome for squamous carcinoma of the tonsil, Int. J. Cancer 106 with cervical cancer, Cancer Epidemiol Biomarkers Prev. 14 (May (5)) (2005) (September (4)) (2003) 553–558. 1157–1164. [90] K. Lindel, P. Burri, H.U. Studer, et al., Human papillomavirus status in advanced [74] M. Majoros, K.D. Devine, E.M. Parkhill, Malignant transformation of benign cervical cancer: predictive and prognostic significance for curative radiation laryngeal papillomas in children after radiation therapy, Surg. Clin. North Am. treatment, Int. J. Gynecol. Cancer 15 (March (2)) (2005) 278–284. 43 (August) (1963) 1049–1061. [91] F.L. Rimell, D.L. Shoemaker, A.M. Pou, et al., Pediatric respiratory papillomatosis: [75] V. Gorgoulis, G. Rassidakis, A. Karameris, et al., Expression of p53 protein in prognostic role of viral typing and cofactors, Laryngoscope 107 (July (7)) (1997) laryngeal squamous cell carcinoma and dysplasia: possible correlation with 915–918. human papillomavirus infection and clinicopathological findings, Virchows. Arch. [92] J. Smith, R. Herrero, K. Erles, et al., Adeno-associated virus seropositivity and HPV- 425 (5) (1994) 481–489. induced cervical cancer in Spain and Colombia, Int. J. Cancer 94 (November (4)) [76] L.A. Lee, A.J. Cheng, T.J. Fang, et al., High incidence of malignant transformation of (2001) 520–526. laryngeal papilloma in Taiwan, Laryngoscope 118 (January (1)) (2008) 50–55. [93] H.D. Mayor, S. Drake, J. Stahmann, et al., Antibodies to adeno-associated satellite [77] H. Lindeberg, S. Syrjanen, J. Karja, et al., Human papillomavirus type 11 DNA in virus and herpes simplex in sera from cancer patients and normal adults, Am. J. squamous cell carcinomas and pre-existing multiple laryngeal papillomas, Acta Obstet. Gynecol. 126 (September (1)) (1976) 100–104. Otolaryngol. 107 (January (1–2)) (1989) 141–149. [94] P.L. Hermonat, Adeno-associated virus inhibits human papillomavirus type 16: a [78] G. Hudelist, M. Manavi, K.I. Pischinger, et al., Physical state and expression of HPV viral interaction implicated in cervical cancer, Cancer Res. 54 (April (8)) (1994) DNA in benign and dysplastic cervical tissue: different levels of viral integration 2278–2281. are correlated with lesion grade, Gynecol. Oncol. 92 (March (3)) (2004) 873–880. [95] P. Mounts, H. Kashima, Association of human papillomavirus subtype and [79] T. Matsukura, S. Koi, M. Sugase, Both episomal and integrated forms of human clinical course in respiratory papillomatosis, Laryngoscope 94 (January (1)) papillomavirus type 16 are involved in invasive cervical cancers, Virology 172 (1984) 28–33. (September (1)) (1989) 63–72. [96] E.M. Maloney, E.R. Unger, R.A. Tucker, et al., Longitudinal measures of human [80] P.G. Fuchs, F. Girardi, H. Pfister, Human papillomavirus 16 DNA in cervical cancers papillomavirus 6 and 11 viral loads and antibody response in children with and in lymph nodes of cervical cancer patients: a diagnostic marker for early recurrent respiratory papillomatosis, Arch. Otolaryngol. Head Neck Surg. 132 metastases? Int. J. Cancer 43 (January (1)) (1989) 41–44. (July (7)) (2006) 711–715. [81] B.C. Das, J.K. Sharma, V. Gopalakrishna, et al., Analysis by polymerase chain [97] R. Rabah, W.D. Lancaster, R. Thomas, et al., Human papillomavirus-11-asso- reaction of the physical state of human papillomavirus type 16 DNA in cervical ciated recurrent respiratory papillomatosis is more aggressive than human preneoplastic and neoplastic lesions, J. Gen. Virol. 73 (September (Pt 9)) (1992) papillomavirus-6-associated disease, Pediatr. Dev. Pathol. 4 (January (1)) 2327–2336. (2001) 68–72.