Human papovaviruses

In this review, we describe features of the human papoviruses. These, although still ‘viruses in search of a disease’ are certainly of importance as latent viruses which can be reactivated in patients who are immunosuppressed, either as a result of specific treatment or through underlying disease. Some of the newer techniques of molecular biology have been used to detail the finer structure of these viruses and we mention these as they illustrate approaches which others besides virologists should be aware of. These methods indicate that, in spite of significant biological differences, the group possess close similarities. Thus JC virus is associated in some way with progressive multifocal leucoencephalopathy, BK virus produces a latent infection in renal tissue and SV40 appears to be seldom responsible for natural (as opposed to iatrogenic) human infection. SV40 and JC viruses are oncogenic; BK is much less so. The molecular closeness in biological diversity suggests that it might be feasible to identify the packets of genetic information that, for example, transmit the message ‘transformation’ in the case of SV40 and JC which is absent or blocked in the case of BK. At the clinical level, reactivation of BK in immunocompromised patients is common and that of JC occurs. Whether such reactivation is associated with significant disease remains unclear, and this is a definite area where clinicians could stimulate progress by invoking the aid of their microbiological colleagues.