Cytotoxic T lymphocytes are critical in the control of infectious bronchitis virus in poultry

Various strains of infectious bronchitis virus (IBV) cause respiratory, kid ney, enteric and reproductive illnesses in chickens, especially in newly ha tched chicks. Assays have been developed to identify Gray strain IBV-specif ic cytotoxic T lymphocyte (CTL) responses using viral infected antigen pres enting cells (APC) and using the Semliki Forest virus vector infected APC e xpressing individual Viral polypeptides. It was shown that major histocompa tibility complex restricted CTL are responsible for early control of IBV in fection. The kinetics of viral load observed in the lungs and kidneys corre lated with the level of IBV-specific CTL activity of effector cells prepare d from spleens of infected chicks. Adoptive transfer of immune T cells to c hicks prior to infection demonstrated that IBV primed CD8(+), alpha beta T lymphocytes could protect chicks from acute infection. CTI, determinants in the viral particle can be mapped to the spike and nucleocapsid proteins bu t not to the membrane protein. The carboxyl terminus of the nucleocapsid pr otein houses an epitope(s) responsible for induction of CTL responses to IB V N protein. Inoculation of DNA plasmid expressing the carboxyl terminus of Gray strain N resulted in induction of CTL that cross-react with two disti nct IBV strains. In addition, this potential DNA vaccine resulted in protec tion of chicks against acute infection. (C) 2000 Elsevier Science Ltd. All rights reserved.