Phylogenetic analysis of small ruminant lentiviruses.

Abstract

Based on available sequence data, a phylogeny of small ruminant lentiviruses (SRLV) was established for env, pol, gag and LTR fragments using maximum likelihood, neighbour-joining and minimum evolution reconstruction techniques. To reconstruct topologies as accurately as possible, phylogenetic parameters like base composition, percentage divergences, kappa, the gamma shape parameter alpha and codon position-specific rates were estimated prior to the reconstruction of trees. Divergences between fragments of SRLV ranged from 16 % in gag and pol to 22 % in env and 35 % in LTR. The codon position bias found and the ratios of synonymous to nonsynonymous substitutions were inversely related to overall divergence, indicating the existence of both negative and positive Dar-

Direct Evidence for Natural Transmission of Small-Ruminant Lentiviruses of Subtype A4 from Goats to Sheep and Vice Versa

“…Although some subtypes of the large and diverse SRLV group are found among both goats and sheep, thus presenting evidence for more than one event of interspecies transmission in the past (12,26,32), and although interspecies transmission has been achieved experimentally (1), the natural transmission of these viruses across the species barrier has never been documented directly. Here we have phylogenetically analyzed viruses isolated from goats or sheep that seroconverted after they were newly exposed to SRLV-infected animals of the other species.…”

“…MVV can, indeed, be experimentally transmitted to goats and, vice versa, CAEV can be transmitted to sheep (1). The fact that some SRLV subtypes have been isolated from both sheep and goats furthermore indicates that interspecies transmission must have occurred at least once in each of these subtypes, although the frequency and direction of transmission remain unknown (12,21,22,32). While interspecies transmission from goats to sheep under natural conditions has never been observed (1,16,23,27), we have recently forwarded statistical evidence suggesting that transmission of the newly discovered SRLV subtype A4 from sheep to goats must occur regularly, though rarely (26).…”

“…(14,17,18,28). Earlier phylogenetic analysis, mostly based on short sequences, has suggested that these very diverse viruses can be divided into six different sequence clades, I to VI (12,21,22,32). Recent work based on long sequences in gag and pol of more than 100 new isolates from Switzerland and all available database sequences has, however, demonstrated that the SRLV should rather be divided into four principal sequence groups A to D, which differ by 25 to 37% in gag and pol sequences.…”

Development and comparison of strain specific gag and pol real-time PCR assays for the detection of Visna/maedi virus

“…Few reports describe real--time protocols designed for diagnostic use. Given the high degree of genetic heterogeneity which characterizes the SRLVs ( Zanoni, 1998), diagnostic assays were based on conserved sequences of the LTR, gag and env regions , Herrmann--Hoesing et al, 2007. Samples were simply classified as positive or negative by Brinkhof and by Peterson, who did not report quantitative data.…”

Vírus da artrite encefalite caprina: isolamento e caracterização de parte do gene gag

“…Dessa forma, o isolamento e a caracterização de novas amostras virais provenientes de regiões geográficas distintas possibilita uma melhor verificação da heterogeneidade genética entre os LVPR, importante tanto para os estudos epidemiológicos relacionados à transmissão intra e interespecíficas dos vírus, quanto para esclarecer a origem e a evolução desse grupo viral. A maioria dos estudos filogenéticos dos LVPR foram baseados nos genes pol, env e gag, com poucos estudos comparando os genes regulatórios (Castro et al, 1999) e a região LTR (Zanoni et al, 1998).…”