- Volume 69, Issue 11, 1988

Analysis of biopsies of cervical intraepithelial neoplasia (CIN) revealed a high percentage with human papillomavirus (HPV) sequences that would hybridize to a mixture of HPV probes only under conditions of relaxed stringency. The DNA sequences of one of these viruses was molecularly cloned and shown to be a new HPV, type 52 (HPV-52). This virus is most closely related to HPV-33. Hybridization analysis with restriction fragments of HPV-52 showed collinearity with the HPV-33 genome. DNA sequencing revealed a high level of conservation between the two viruses within the L1 open reading frame but significant divergence in the non-coding region of the viral genomes. Prevalence studies indicated that HPV-52 sequences were present in three of 137 (2%) CIN and in one of 48 (2%) cervical squamous cell cancers studied in the U.S.A.

Some properties of Triatoma virus (TrV), a picorna-like virus recently isolated from Triatoma infestans, have been studied. Electron microscopic observations of purified viral preparations showed the presence of non-enveloped viral particles 30 nm in diameter. The sedimentation coefficient of virus particles was about 165S and the buoyant density in CsCl was 1.39 g/ml. The viral genome was composed of one single-stranded RNA molecule with an M r of 3 × 106. Three major polypeptides with M r values of 39K, 37K and 33K and a minor one of about 45K were found in the virus particle. TrV particles contain about 35% RNA and 65% protein by weight. These data support the classification of this virus in the family Picornaviridae.

The replication of cowpea mosaic virus (CPMV) RNA was studied in crude membrane fractions prepared from leaves of CPMV-infected cowpea and Chenopodium amaranticolor. In vitro replicase assays showed that in the cowpea extract only the replicative intermediate (RI) and replicative form (RF) were synthesized. In the C. amaranticolor extract however, single-stranded progeny RNA was produced in addition to RI and RF. Production of the ssRNA in the C. amaranticolor extract was a result of the greater stability of the CPMV replication complex in this host. Comparison of the viral replicase activity and the amount of virus-encoded proteins in cowpea and C. amaranticolor crude membrane fractions indicated that only a small fraction of the non-structural proteins detected in cowpea is active in RNA replication. This suggests that viral replication proteins are used only once, perhaps because of a stringent coupling of polyprotein processing and replication.

Two experimental systems were used to study the translocation of virus particles in plants and translocation followed by infection of non-wounded plant cells. Translocation of virus particles in cut plant stems occurred with the beetle-transmissible viruses southern bean mosaic, bean pod mottle and cowpea severe mosaic, but not with sunn hemp mosaic and tobacco ringspot viruses, which are not transmitted by beetles. When purified viruses were injected below sections of steam-killed stems, only the beetle-transmissible viruses were translocated and infected non-wounded tissue above the steam-killed area. However, sunn hemp mosaic, tobacco ringspot and bean yellow mosaic viruses, which are not transmitted by beetles, did not infect plants above killed portions of the stem. These results suggest that both translocation of virus particles in the xylem of plants and establishment of infection in non-wounded tissue are key properties of viruses that are transmitted by beetles.