The immune system of chicken and its response to H9N2 avian influenza virus

Abstract

Influenza A virus is a negative-sense single-stranded RNA virus that belongs to Orthomyxoviridae family. Based on the antigenic characteristics of hemagglutinin (HA) and neuraminidase (NA) influenza viruses are classified into multiple subtypes. H9N2 belongs to the low pathogenic Avian Influenza Viruses (AIVs) and is one of the widely spread viruses in poultry, which can pose a threat to humans by directly infecting or providing internal genes for various zoonotic avian influenza strains. It has the potential to directly or indirectly participate in becoming an AIV that causes a human pandemic. When the virus enters a host, the innate immune system is activated first by pattern recognition receptors. The cytokines produced at the site of infection recruit innate immune cells and antigen-presenting cells and those cells subsequently transmit antigenic signals to adaptive immune cells (i.e. B cells and T cells), to trigger specific humoral and cellular immune responses. As a result, humoral and cellular immunity can clear virus and infected cells via antibody-mediated neutralization and cytotoxicity, respectively. Understanding how chicken immune systems respond to H9N2 is a top priority for effectively controlling the virus’s spread and designing vaccines. In this review, we comprehensively discuss the role of the chicken immune system in defending against H9N2, and clarify the current limitations in understanding chicken immune responses to H9N2 virus, thereby providing potential directions for future research as research on the chicken respiratory mucosal immune system has been stagnant for more than 20 years especially on how the mucosal immune system in chicken responds to avian influenza.

Comparison of Infectious Bronchitis Virus (IBV) Pathogenesis and Host Responses in Young Male and Female Chickens

“…The anti-IBV antibody titers in the serum of all the experimental groups were within the negative range at both 4 and 11 dpi. The negative results in the IBV-infected male and female chickens at 4 dpi could be because the antibody-mediated immune response in chickens only starts at 4-5 dpi and the level of anti-IBV antibody in serum at this time will be very low [41,42]. In addition, the anti-IBV antibody titers in the serum of infected male and female chickens at 11 dpi were also negative.…”

Evolutionary Events Promoted Polymerase Activity of H13N8 Avian Influenza Virus

“…Since first identified in United States turkeys in 1966, H9N2 AIVs have spread widely around the world [ 9 , 10 , 11 ]. H9N2 AIVs are the most prevalent subtypes in China and are endemic in multiple avian species [ 12 , 13 ].…”

Expression of Toll‐like receptors and host defence peptides in the cecum of chicken challenged with Eimeria tenella

“…It is generally accepted that innate immunity and adaptive immunity are both important in the prevention of chicken coccidiosis 10 . However, in the early stages of infection, the innate immunity of the host ensures an immediate response to invading parasites, and activation of innate immune responses primarily depends on innate immune receptors 11 . Toll‐like receptors (TLRs) are major components of innate immune system in vertebrate species, and these transmembrane proteins are responsible for microbial recognition.…”

“…10 However, in the early stages of infection, the innate immunity of the host ensures an immediate response to invading parasites, and activation of innate immune responses primarily depends on innate immune receptors. 11 Toll-like receptors (TLRs) are major components of innate immune system in vertebrate species, and these transmembrane proteins are responsible for microbial recognition. Once activated by specific ligands such as bacterial lipopolysaccharide (LPS), glycolipids, viral nucleic acids and CpG Oligodeoxynucleotides (CpG ODN), TLR signals can lead to the recruitment of various immune cells and generate a wide range of biologically active molecules including chemokines, cytokines and antimicrobial peptides, which stimulates the innate immune responses necessary for parasite clearance and resistance to re-infection.…”