14 Nature Vol. 285 1 May 1980 extremely strong, but much less certain is Deep sea diving the connection between HSV type 2 and from M. J. Halsey cervical cancer. R.P. Eglin and his colleagues (Institute of Virology, Glasgow) A new record was recently set at Duke water work. reported some very careful in situ University when three men successfully Current work on a wider pharma­ hybridization experiments which showed underwent conditions simulating a dive cological approach to the problem low level expression of HSV -specific RNA to a depth of 650m of sea water. This suggests that selective drugs for HPNS sequences in pre-invasive and invasive achievement set the background for a may exist. Structural isomers of some carcinoma tissues, while two groups recent workshop• on the problems of steroid anaesthetics, such as althesin, reported the induction of cervical car­ very deep dives, in the range 460-760m have been found in animals to continue cinomas in animal model systems, W.B. (1500-2500ft). their action against HPNS even though Wentz and colleagues (Case Western Fifty years ago men dived using only they no longer have anaesthetic effect. Reserve University, Cleveland) using compressed air but nitrogen narcosis, Additional problems in deep diving inactivated HSV type 2, and C. Minhui and which increases with increasing partial include those of temperature control, associates (Hupei Medical College, pressure of the gas, effectively prevented respiration and decompression. Tem­ Wuhan, China) using live virus. A very this technique from being used at depth. perature control is of great concern in large prospective study to determine the The subsequent development of helium/ working dives because high pressure risks associated with HSV type 2 infections oxygen mixtures allowed safe diving to seems to affect the body's thermoregul­ in women is currently underway in depths beyond 50m, but problems atory capacity. Not only is there a Czechoslovakia (V. Vonka and colleagues, develop when the 450-550m range is narrowing of the limits within which the Institute of Sera and Vaccines, Prague) reached. At these depths the high body can make corrections to mantain a involving colposcopy, cytological smears pressure neurological syndrome (HPNS), stable temperature but also the subjective and blood tests on 10,000 women selected characterised by muscular tremor, experience of heat and cold may become at random. disorientation, and short sleep-like divorced from actual conditions. One of the tantalizing questions about periods of loss of attention develops; in Respiration in chamber dives is not a herpes viruses is how latent infections are animal experiments even higher pressures general problem but dyspnoea, ex­ maintained for long periods. What factors have been shown to cause convulsions. acerbated by exercise, is present. This are important in the suppression of the However, a breakthrough has now been could become a limitation in future deep infection? This is an area in which very little achieved by the discovery that HPNS can dives. The phenomenon appears to be real progress has been made although it is be overcome by the use of low partial unrelated to gas density but is an aspect of generally accepted that specific antibodies pressures of anaesthetics. It is this that HPNS that is not alleviated by nitrogen. are important in maintaining HSV latency. has lead to new techniques and to new Decompression from deep depths is However some elegant experiments records in deep diving. In experiments proving possible although recompression described by H. Openshaw (University of with animals, gases with anaesthetic or a change of gas breathing mixture may California, Sacramento) using a mouse action such as nitrogen or nitrous oxide prove difficult. model throw considerable doubt on this and low doses of intravenous anaesthetics Although diving beyond 460 m has idea. Latent infections were established in such as ketamine or althesin have been now certainly been made possible, and mice which were protected during the found effecuve. Nitrogen deliberately both naval and commercial interests primary infection by administration of introduced in small quantities into the agree there will be a definite need for such immune antibody so that their own helium/ oxygen breathing mixture was dives, it must be remembered that the immune systems were not primed. It was the basis of the trimix which was used in principles underlying the effects shown in the majority of animals that as the the record chamber dive. This has also described above are not at all understood. passive antibodies faded the latent been used in the successful open sea dive The number of men who have been infections were maintained. to 460 m by Comex, S.A. Marseille, beyond 300m remains very small; only an From the clinical point of view there are which has set a new standard for deep understanding of the basic mechanisms two areas which require urgent attention. involved can ensure that such deep dives The clinician would like to be in a position can continue in safety. 0 to offer some protection to a patient (e.g. a •The meetina was held at the Institute of Marine Biomedical Research, Wilmington, N. Carolina and the proceedings will prospective organ recipient) who he knows be published as Techniques for diving deeper than /500ft by M.J. Halsey is in the HPNS group at the will be at risk from these viruses in the the Undersea Medical Society, Bethesda, Maryland. Clinical Research Centre, Harrow, U.K. immediate future. Such protection could be generated by a suitable vaccine. (University of Chicago). Over a brief mother leaving the fetus with only a 50/50 Secondly he needs effective drugs to period there were 8 cases of HSV chance of survival (A.J. Nahmias, Emory control the more serious diseases encephalitis at Massachusetts General University, Atlanta). HSV, CMV and VZV associated with these viruses. There appear Hospital, and since this is an extremely rare are all common infections of immunosup- to be encouraging developments in both disease it was inevitably thought that the pressed patients such as those under-going areas. epidemic was caused by a particularly cancer therapy or organ transplantation. The problems associated with assessing neurovirulent strain of virus. However, The diseases in these patients are often very the safety of attenuated herpesvirus restriction enzyme analyses were made on severe and they are a significant cause of vaccines are considerable since we have to the genome DNA of viruses isolated from death. There were also suggestions that take into account not only the primary all 8 patients and as the patterns were such diverse conditions as hardening of the infection but also recurrent disease and the distinct from each other it was proven that arteries and psychotic depression (S. oncogenic potential of these viruses. the cases were caused by different virus Sprecher, Institut Pasteur du Brabant) and Attenuated VZV vaccine strains have been strains. even gastric ulcers (B.F. Vestergaard, developed and are in use in some countries The viruses may be particularly Institute of Medical Microbiology, although the prevailing view, expressed by dangerous in two situations; infections of Copenhagen) might be initiated by P.A. Brunnel (University of Texas), was the newborn and of the immunosup­ recurrent HSV infections. that these vaccines should be used only in· pressed. CMV may cross the placenta and It has long been debated whether herpes cases where patients are exposed to serious infect the fetus sometimes causing severe viruses are involved in the induction of risk. An attenuated CMV vaccine has also brain damage. HSV may be contracted human cancers. Certainly the association Graham Darby is in the Department of from the infected genital tract of the between EBV and Burkitt's Lymphoma is Pathology, University of Cambridge. 0028-0836/80/ 19014-0lSOl.OO ------~©-1·9-80-M~a-cm-,~. lla-n~Jo-u-rruU~s~Ltd