Showing papers by "Sharad Kumar published in 1993"

Protection of sheep against bovine leukemia virus (BLV) infection by vaccination with recombinant vaccinia viruses expressing BLV envelope glycoproteins: correlation of protection with CD4 T-cell response to gp51 peptide 51-70.

Abstract: We have previously constructed vaccinia virus (VV) recombinants containing a complete or truncated envelope (env) gene of bovine leukemia virus (BLV). Only recombinants carrying the complete env gene (VV-BLV2 and VV-BLV3) expressed env glycoprotein on the surface of virus-infected cells and produced an antibody response in rabbits. In the present study, these VV recombinants were used to immunize sheep prior to challenge with BLV-infected peripheral blood mononuclear cells. Both humoral and cell-mediated immunity were monitored in infected animals. Sheep inoculated with recombinants containing the complete env gene showed a CD4 response to a defined epitope of gp51, but this response was absent 4 months postchallenge. Anti-gp51 antibodies appeared in animals inoculated with complete env 2 weeks after challenge, reached a peak at 4 weeks, and subsequently declined over 16 months. No CD4 response was recorded in animals inoculated with recombinants containing truncated env gene (VV-BLV1). BLV-infected control animals and those animals receiving VV-BLV1 were slower to develop antibodies postchallenge, and the titers of anti-gp51 antibodies continued to increase over 16 months. Proviral DNA was detected by the polymerase chain reaction in the four groups at 6 weeks after challenge. However, it could not be detected 4 months postinfection in the VV groups inoculated with complete env. Provirus was present in the VV-BLV1 and control groups over the 16-month trial period. These results demonstrate that vaccination with VV recombinants containing the complete env gene of BLV protects sheep against infection and that protection correlated with a CD4 T-cell response to a defined epitope.

Expression of GTP-binding protein gene drg during Xenopus laevis development.

Abstract: To study the genes which may play a role in the development of the vertebrate central nervous system (CNS) using a subtraction cloning approach, we previously identified a set of novel genes which are predominantly expressed in the mouse embryonic CNS and down-regulated during development. One of these genes, drg, encodes a novel 41 kilodalton GTP-binding protein (DRG), which is highly expressed in the embryonic CNS and shows remarkable evolutionary conservation. To study the biological role of this protein during Xenopus embryonic development, we cloned the Xenopus drg cDNA (Xdrg). The predicted Xenopus DRG protein (XDRG) is more than 95% identical to the mouse DRG. Analysis of Xdrg expression by Northern blots, whole-mount in situ hybridization and RNA-PCR revealed the presence of varying levels of transcript for this gene in embryos and adult tissues. Among the three mRNA species detected by Northern hybridization, two smaller ones show temporally regulated expression patterns during embryonic development.