Induction profiles of mRNA of toll like receptors and cytokines in chickens pre-exposed to low pathogenic avian influenza H9N2 virus followed by challenge with highly pathogenic avian influenza H5N1 virus

Abstract

Herein, the induction of TLRs and cytokines in chickens pre-exposed to low pathogenic avian influenza H9N2 virus followed by challenge with highly pathogenic avian influenza (HPAI) H5N1 virus was studied. Four groups (1–4) of chickens inoculated with 106 EID50 of H9N2 virus were challenged with 106 EID50 of H5N1 virus on days 1, 3, 7 and 14 post H9N2 inoculation, respectively. In groups (1–4) TLRs and cytokines induction was studied in chicken PBMCs on day 3 post H5N1 challenge. In H5N1 control group TLRs (1, 2, 5 and 7) cytokines (IFNα, IFNβ, IFNγ, IL1β, IL2, IL4, IL8 and TGF β3) were down regulated. In group 1 down regulation of cytokines and TLRs was similar to H5N1 control birds. Down regulation of TLRs and cytokines in H5N1 control and group 1 resulted death of all the chickens. In group 2, up-regulation of TLRs (3, 7 and 15) and induction of TNFα, IFNα, IFNβ, IFNγ aided virus clearance leading to survival of all the chickens. In group 3 significant up-regulation of TLRs (3, 4 and 15) and significant induction of cytokines (IFNγ, TNFα, IL1β, IL4, IL6, IL8, IL10 and TGF β3) was detected. In group 4 significant up-regulation of TLRs (2, 3, 7 and 15) and significant induction of cytokines (IFNγ, TNFα, IL1β, IL2, IL6, IL8 and IL10) was detected. In groups 3 and 4 simultaneous and significant induction of pro-inflammatory, antiviral and anti-inflammatory cytokine resulted cytokine dysregulation leading to death of (2/6) and (3/6) chickens respectively. Hence, the study revealed TLRs and cytokines role in modulating the H5N1 infection outcome in chickens pre-exposed to H9N2 virus.