International Journal of Pediatric Otorhinolaryngology 74 (2010) 7–14 Contents lists available at ScienceDirect International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl 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 viruses 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 malignancy. 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 wart-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 virus with an icosahedral structure formed by 72 has been found in 100% of papillomas 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 epithelium 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 papilloma (wart) types have been identified from papilloma tissue from RRP patients formation. The latter typically results in warts 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 carcinomas of the larynx and pharynx 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 biopsy 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].