Progress 09/01/04 to 08/31/06
Outputs
OUTPUTS: J Kamil is no longer with the University, we are not able to get a final report. Please terminate this project without the final report. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
N/A
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
A viral lipase homolog encoded by the Mareks disease virus (MDV) was found to be important for wild-type levels of pathogenesis in vivo. Specifically, vLIP was found to enhance replication of MDV at later time points after infection. Furthermore, both tumor incidence and disease were reduced by approximately 30 percent in birds infected with vLIP mutant viruses compared to those infected with parental or revertant viruses encoding wild-type vLIP. The data obtained on the role of vLIP in MDV pathogenesis will be of practical use to future design of Mareks disease vaccines. Since our data shows that vLIP enhances viral replication at later points in infection, vLIP may be important in suppression of acquired immunity. Therefore, our findings provide an impetus for testing the efficacy of vaccine strains of MDV where vLIP is mutated or deleted. During our studies, an alanine point mutant of the serine nucleophile, as well as a deletion mutant of the lipase homologous
region of vLIP were generated the context of recombinant MDV genomes using bacterial artificial chromosome technology and tested in MDV susceptible P2a-line chickens. The resulting data indicate that MDV harboring a serine nucleophile mutant of vLIP behaves remarkably like a vLIP deletion mutant in respect to reduced replication and pathogenesis in vivo. Since vLIP lacks a complete lipase enzyme catalytic triad and is thus unlikely to serve as a conventional enzyme, the finding that the serine nucleophile is relevant to MDV replication in vivo is notable. It is suggested that vLIP may employ a novel mechanism of action for a secreted factor in viral pathogenesis. One hypothesis to explain the fact that the serine nucleophile is still important in pathogenesis is that the virus has repurposed this lipase homologous domain for lipid bonding. Specific Aim 1 from my original NRI proposal: Determine the phenotypes of vLIP deletion and point mutant viruses has been completed and has
resulted in a publication. Specific Aim 2, as it was originally proposed, has not been completed. In light of the recent findings that vLIP is a secreted virulence factor of MDV, I am currently exploring whether vLIP specifically binds to any population of chicken peripheral blood leukocytes. The hypothesis is that vLIP enhances viral replication by binding to receptor molecules on immune effector cells and events involved in activation of the acquired immune response. In order to pursue this aim, vLIP has been fused at its carboxyl-terminus to the Fc portion of the human IgG heavy chain and is being expressed as a secreted protein in a baculovirus expression system. Binding of vLIP to leukocytes can be probed by incubating vLIP-Fc with peripheral leukocytes or splenocytes. Phycoerythrin-conjugated anti-Fc antibodies can then be used to detect vLIP binding to cells by flow cytometry. Such cells could later be identified with monoclonal antibodies to chicken lymphocyte markers, which
are available commercially. In addition, a viral CXC chemokine encoded by MDV is also being examined in parallel using the same approach.
Impacts
A lipase homologous gene, vLIP, encoded in the genome of Mareks disease virus, has been demonstrated to enhance the disease-causing potential of the virus. Because Mareks disease virus is an economically important herpesvirus pathogen of chickens, the identification of this gene as virulence factor will aid in the design of novel vaccines against Mareks disease and may thus benefit the US poultry industry.
Publications
- Kamil, J.P., Tischer B.K., Trapp S., Nair V.K., Osterrieder N. and Kung H.-J. 2005. vLIP, a Viral Lipase Homologue Is a Virulence Factor of Mareks Disease Virus. J Virol 79 (11) 6984-6996.
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