Schat

Chicken Infectious Anemia Virus: Immunosuppression, Transmission, and Impact on Other Diseases

Immunosuppression (IS) is a costly problem for the poultry industry. Chicken infectious anemia virus (CIAV) is a major cause of IS. The reason for CIAV-induced IS was elucidated when Markowski-Grimsrud and Schat (Immunology 109, 283, 2003) showed that replication of CIAV caused an absence of antigen-specific cytotoxic T cells (CTL) in CIAV antibody-negative (AB-) chicks co-infected with CIAV and reticuloendotheliosis virus (REV) or Marek's disease virus (MDV). This proposal plans to further elucidate the impact of CIAV infection on viral and bacterial infections using MDV, REV, and Salmonella typhimurium (STM). Although CIAV infection is considered to be ubiquitous, Dr. Davidson et al (KVI) in a recent study were unable to detect CIAV in flocks lacking typical CIAV signs, while it was amplified from flocks with signs of disease. These data suggest a link between the presence of CIAV, various CIAV signs and increased susceptibility to other diseases. All growth parameters, mortality, or enhancement of other diseases indicated a decline in the health, productivity and profitability in CIAV-positive flocks. Recent data from Dr. Davidson also indicated that CIAV may be shed through feathers, thus contributing to the efficient spread of the virus. Dr. Schat will examine the impact of CIAV on CTL responses to MDV and REV if CIAV infection precedes or follows challenge with MDV or REV. Dr. Davidson will focus on experimental infections with CIAV and MDV to further delineate the impact of CIAV on MD, various parameters of morbidity, horizontal spread of both MDV and CIAV, and cell-mediated immunity by measuring IFN-g levels in serum. Prof. Heller (HUJI) will study the impact of CIAV infection on bacterial colonization, represented by STM, a major zoonotic pathogen. Special attention will be devoted to the horizontal spread of CIAV, and on the differences between a recent Israeli isolate and the prototype Cux-1 strain of CIAV. These studies will contribute to a better understanding of the role of CIAV in IS and are expected to lead to recommendations for future vaccine development, and on a better understanding of the horizontal dissemination of CIAV in poultry houses. To study the impact of CIAV on CTL development AB+ and AB- chickens will be inoculated with CIAV preceding or following infection with MDV or REV. CIAV replication will be measured by quantitative, real-time (q)PCR and qRT-PCR and CTL responses will be examined in chromium release assays. The Israeli groups will also use qPCR and qRT-PCR approaches to monitor experimental CIAV infections.