Growth and molecular evolution of vesicular stomatitis serotype New Jersey in cells derived from its natural insect-host: evidence for natural adaptation.

In this study we evaluated the growth and molecular evolution of a natural isolate of VSV-NJ (89GAS) from sand flies in cells derived from sand flies (LL5), mosquitoes (C6/36) or hamsters (BHK21). Two VSV-NJ natural isolates of mammalian origin were used for comparison. For each virus we measured: (i) ability to grow in one-step growth curve or after serial passage on each cell type; (ii) ability to induce persistent infection, and (iii) genetic stability of the glycoprotein gene (G) after serial passage in each cell type. Sand fly virus 89GAS grew to higher titers in insect cells compared with viruses of mammalian origin and showed increasing titers with each passage only in C6/36 cells. All viruses established productive persistent infections in both mosquito and sand fly cells but only LL5 cells yielded sustained high virus titers for periods of up to 81 days. Analyses of the consensus sequences of the G gene from each virus after 0, 10 or up to 25 passages in each cell line showed nucleotide substitution rates between 1.39 x l0(-4) and 6.95 x l0(-5). The majority of these changes were non-synonymous, suggesting positive selection. We did not detect increased nucleotide substitution rates on the G gene of 89GAS after passage in cell lines of mosquito or mammalian origin, nor in viruses of mammalian origin after passage in insect cells. This indicates that although VSV G is positively selected in vitro by the insect cell environment, this does not fully explain VSV natural adaptation. This is the first evidence of naturally occurring adaptation of VSV to cells derived from its natural host.

Genetic analysis of vesicular stomatitis virus-New Jersey from the 1995 outbreak in the western United States.

OBJECTIVE: To compare molecular associations between the vesicular stomatitis virus (VSV)-New Jersey isolates of the 1995 outbreak with those from previous outbreaks between 1982 and 1985 in the western United States. SAMPLE POPULATION: 23 virus isolates considered representative of the 1995 outbreak of vesicular stomatitis. PROCEDURE: Viral gene coding for surface-envelope protein G was evaluated by use of nucleotide sequencing and phylogenetic analysis. RESULTS: Changes in up to 0.77% of the nucleotide bases and 1.35% of the amino acids were detected among the 1995 viral isolates, whereas changes in up to 3.2 and 2.9% of the nucleotides and amino acids, respectively, were found, compared with the 1982 to 1985 viruses. Insertions or deletions were not found in the entire gene, which spanned 1,554 nucleotide bases. CONCLUSIONS AND CLINICAL RELEVANCE: Phylogenetic analysis indicated that the 1995 VSV-New Jersey belongs to a lineage distinct from that of the 1982 to 1985 viruses that caused previous outbreaks in the western United States. Furthermore, it also is distinct from strains from Central America and from the Georgian Hazelhurst strain.

Re-emergence of vesicular stomatitis in the western United States is associated with distinct viral genetic lineages.

Phylogenetic analysis of partial phosphoprotein and glycoprotein gene sequences showed that a single genetic lineage of vesicular stomatitis virus (VSV) serotype New Jersey (NJ) caused the 1995 and 1997 outbreaks of vesicular stomatitis (VS) in the western United States. While distinct from VSV-NJ strains causing previous outbreaks in the western United States and those circulating in feral swine in the southeastern United States, this lineage was closely related to viral lineages circulating in the Mexican states of Guerrero, Veracruz, and Oaxaca in 1996, 1989, and 1984 respectively. In 1997 and 1998, VSV serotype Indiana 1 (IN1) re-emerged in the western United States after 30 years. Viruses causing these outbreaks grouped within a single genetic lineage distinct from VSV-IN1 isolates causing outbreaks in the western United States in 1929 and 1956 but closely related to a strain circulating in the state of Colima in central Mexico in 1997. Our data showed that sporadic VS outbreaks in the western United States are caused by genetically distinct viral lineages closer to those circulating in enzootic areas of central and southern Mexico than to those causing previous outbreaks in the United States. The genetic evidence and temporal distribution of outbreaks are not consistent with a pattern of long-term maintenance of VSV in the western United States.