Submitted to: Research Conference on Orthomyxoviruses
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2009
Publication Date: September 9, 2009
Citation: Kapczynski, D.R., Petkov, D., Kulkarni, G., Hunt, H.D., Liljebjelke, K.A. 2009. Cross reactive immunity derived from chickens infected with H9N2 low pathogenic avian influenza against homologous and heterosubtypic challenge [abstract]. 5th Orthomyxovirus Research Conference, September 9-12, 2009, Freiburg, Germany. p. 32. Technical Abstract: Because vaccines for use in commercial poultry against avian influenza (AI) are mainly inactivated and delivered parenterally, our knowledge of protective immunity of poultry against AI is largely based on the induction of serum-neutralizing antibodies produced against a specific hemagglutinin (HA) protein subtype. In mice and humans, cytoxic T lymphocyte (CTL) responses specific for influenza A viruses have been shown to be broad and multispecific, mainly targeted against internal AI proteins. In contrast to mammalian immunology, little is known about cross reactive immunity following low pathogenic AI (LPAI) infection in chickens. Therefore, we tested the hypothesis that H9N2 LPAI in chickens could provide cross reactive humoral and/or CTL responses against heterosubtypic LPAI. In these studies, major histocompatibility complex (MHC)-defined (B2/B2) chickens were infected with a H9N2 LPAI isolate recovered from live bird markets in the U.S. and antibody and CTL’s cross reactivity against homologous (H9N2) and heterosubtypic (H6N2 and H5N9) AI viruses of U.S. origin was determined ex vivo. In addition, protection against homologous and heterosubtypic challenge of chickens following H9N2 infection was determined. Results indicate antibodies produced against H9N2 AI displayed better cross reactivity to the H6N2 isolate than the H5N9 isolate. Additionally, splenic lymphocytes from H9N2-infected chickens displayed cross reactive lysis of B2/B2 lung target cells infected with any of the isolates tested here. Removal of the CD8+ population, but not CD4+ T cells, abrogated specific lysis of target cells. The possible mechanisms of the mode of cross protective immunity against LPAI will be discussed in the context of recent findings.