- Volume 84, Issue 1, 2003

Although transmission of human hepatitis B virus (HBV) variants to nonhuman primates is well documented, it remains to be elucidated whether nonhuman primate HBV is transmissible to humans. The prevalence and transmission routes of gibbon HBV were analysed in 101 captive gibbons in Thailand. Approximately 40 % of these animals showed at least one marker of HBV infection; 19 animals were chronic HBV carriers, characterized by elevated levels of alanine amino transferase and the presence of HBV DNA. Some of the chronic animals were found to be anti-HBc (HBV core antigen) negative (4 of 19), while precore promoter point mutations (nt 1762 or 1764) were determined in four animals by RFLP analysis. Phylogenetic tree analysis of the complete surface gene sequences revealed that gibbon viruses clustered separately from hepadnaviruses of other hosts. Evidence for horizontal and vertical transmission in captive gibbons was obtained. HBV DNA was also detected in the saliva of HBV carrier gibbons. Although some of the animal caretakers at the Krabok Koo Wildlife Breeding Centre were found to be chronic HBV carriers, genotype and sequence analysis did not reveal any evidence for zoonotic disease transmission.

Using synthetic peptides we have shown that positively charged sequences present at the C terminus of the L1 protein and the N and C termini of the L2 protein of human papillomavirus type 16 (HPV-16) bind to both DNA and heparan sulfate receptors. Moreover, these short amino acid sequences are sufficient to mediate gene transfer in COS-7 cells. The L1 proteins of other HPVs were shown to contain one or two DNA- and heparin-binding sequences that have the capacity to transfer genes. These DNA-binding sequences also recognized the enhancing packaging sequence of bovine papillomavirus type 1. The results suggest that the L2 protein could participate in DNA packaging during maturation of virions.

The genomic sequence of a new icosahedral DNA virus infecting Myzus persicae has been determined. Analysis of 5499 nt of the viral genome revealed five open reading frames (ORFs) evenly distributed in the 5′ half of both DNA strands. Three ORFs (ORF1–3) share the same strand, while two other ORFs (ORF4 and ORF5) are detected in the complementary sequence. The overall genomic organization is similar to that of species from the genus Densovirus. ORFs 1–3 most likely encode the non-structural proteins, since their putative products contain conserved replication motifs, NTP-binding domains and helicase domains similar to those found in the NS-1 protein of parvoviruses. The deduced amino acid sequences from ORFs 4 and 5 show sequence similarities with the structural proteins of the members of the genus Densovirus. These data indicate that this virus is a new species of the genus Densovirus in the family Parvoviridae. The virus was tentatively named Myzus persicae densovirus.

Genetic diversity and biological variation were compared for California isolates of Cucumber mosaic virus (CMV). These fell into five pathotypes based on their reactions on three cucurbits including a susceptible squash, a melon with conventional resistance and a commercial CMV-resistant transgenic squash. Thirty-three isolates infected and caused symptoms on CMV-resistant transgenic squash. Forty-two isolates infected the CMV-resistant melon, but only 25 isolates infected both. Single-strand conformation polymorphism (SSCP) analysis was used to differentiate 81 California isolates into 14 groups, and the coat protein (CP) genes of 27 isolates with distinct and indistinguishable SSCP patterns were sequenced. Fourteen isolates corresponding to the different SSCP patterns were also used for phylogenetic analysis. Seventy-nine isolates belonged to CMV subgroup IA, but two belonged to CMV subgroup IB. This is the first report of subgroup IB isolates in the Americas. All CMV isolates had a nucleotide identity greater than or equal to 93·24 %. There was no correlation between CP gene variation and geographical origin, collection year, original host plant, or between the degree of CP amino acid sequence identity and the capacity to overcome transgenic and/or conventional resistance. SSCP and sequence analyses were used to compare 33 CMV isolates on CMV-resistant transgenic squash and susceptible pumpkin plants. One isolate showed sequence differences between these two hosts, but this was not due to recombination or selection pressure of transgenic resistance. CMV isolates capable of infecting cucurbits with conventional and transgenic CMV resistance were present in California, even before CMV transgenic material was available.