Infection with chicken anaemia virus impairs the generation of pathogen-specific cytotoxic T lymphocytes.
Infection with chicken anaemia virus (CAV), a circovirus, can result in immunosuppression and subsequent increased susceptibility to secondary infections. This is the first report of impairment of pathogen-specific cytotoxic T lymphocytes (CTL) after natural and experimental infection of chickens with CAV and Marek's disease virus (MDV) or reticuloendotheliosis virus (REV). MDV- and REV-specific CTL were generated at 7 days post infection by 9-30-day-old-chickens that were positive for maternal antibodies to CAV at 9-17 days of age. Replication of CAV could not be demonstrated in these chickens using quantitative real-time polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR assays. In contrast, REV-specific CTL failed to develop when chickens negative for maternal antibodies at 9-17 days of age were infected. Infection with CAV at 45 days of age after CAV maternal antibodies had waned also caused a decreased REV-specific CTL response. In these chickens increased levels of CAV DNA of up to 107 copy numbers per micro g DNA and increased relative transcript levels of CAV by up to a factor of 106 were detected by quantitative real-time PCR and RT-PCR. Interleukin (IL)-1beta and IL-2 mRNA levels were not significantly affected by CAV infection at 7 or 14 days p.i. Similar assays for interferon-gamma (IFN-gamma) transcripts demonstrated a 10-fold increase in IFN-gamma mRNA levels at 7 days post infection following REV or REV + CAV infection, while CAV alone caused a two- to fourfold increase. These results show a strong link between CAV antibody status, CAV replication, and the ability to generate REV-specific CTL. It is likely that the immunosuppressive effects of subclinical infection have previously been underestimated.
Markowski-Grimsrud
Carrie J
CJ
Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Schat
Karel A
KA
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D017727:Chicken anemia virus; D002645:Chickens; D018173:Circoviridae Infections / Q000276:immunology* / Q000662:veterinary; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D003602:Cytotoxicity, Immunologic; D004279:DNA, Viral / Q000097:blood; D007108:Immune Tolerance; D007112:Immunity, Maternally-Acquired; D008380:Marek Disease / Q000276:immunology; D016133:Polymerase Chain Reaction / Q000379:methods; D011201:Poultry Diseases / Q000276:immunology*; D012333:RNA, Messenger / Q000235:genetics; D055761:Reticuloendotheliosis, Avian / Q000276:immunology / Q000662:veterinary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
D000914:Antibodies, Viral; D016207:Cytokines; D004279:DNA, Viral; D012333:RNA, Messenger