Strategies and challenges for eliciting immunity against avian influenza virus in birds

Abstract

Vaccines and vaccination have emerged during the past two decades as essential tools in avian influenza (AI) control for poultry, because they increase resistance to infection, prevent illness and death, reduce virus replication and shed from respiratory and alimentary tracts, and reduce virus transmission to birds and mammals, including humans. Such protection in birds is primarily mediated by homosubtypic humoral immunity against the hemagglutinin protein, but cell-mediated and innate immunity contribute to protection in some bird species. The immune response to the neuraminidase protein can contribute to protection, but immunity to the viral internal proteins is generally not protective. Although, some preliminary studies with M2e protein in chickens suggest partial protection may be achievable. Historically, the H5 subtype AI vaccines have demonstrated broad homosubtypic protection, primarily against H5 high-pathogenicity (HP) AI viruses isolated in the early stages of outbreaks. However, as H5 viruses have become endemic and outbreaks prolonged, some drift variants with resistance to earlier H5 AI vaccines have emerged in Central America, China, Egypt, and Indonesia. How widespread such drift variants are will remain unknown until more detailed genetic and antigenic analyses are conducted on field isolates. Future vaccines will utilize biotechnology to produce new AI vaccine seed strains using HA genes more closely matching circulating field viruses. In addition, newer technologies for AI vaccines will improve vaccine coverage by using mass application technologies for example by drinking water, by spray, or via injection in ovo or at the hatchery.

Characterization of the 2012 Highly Pathogenic Avian Influenza H7N3 Virus Isolated from Poultry in an Outbreak in Mexico: Pathobiology and Vaccine Protection

“…), diagnostics and surveillance, elimination of infected poultry, and potentially decreased poultry susceptibility (i.e., after vaccination) (42). One of the goals of this study was to evaluate both Mexican and U.S. H7 LPAI viruses as potential vaccines for control of the H7N3 HPAI virus.…”

Highly Pathogenic Avian Influenza Virus Subtype H5N1 Escaping Neutralization: More than HA Variation

“…As a consequence, antibodies and viruses coexist. In turn, so-called "escape mutants" resulting from antigenic drift of the viruses are selected (40). These escape mutants are less susceptible to vaccine-induced neutralizing antibodies.…”

Gene expression profiles in primary duodenal chick cells following transfection with avian influenza virus H5 DNA plasmid encapsulated in silver nanoparticles

“…13 Our previous study showed that chickens given an oral H5 DNA vaccine using AgNPs as a carrier showed antibody and T cell responses with enhanced Th1-like cytokine expression in the spleen. 11 However, there is no direct evidence of specific cytokines induced by hemagglutinin of avian influenza virus.…”

“…11 Spread of the highly pathogenic avian influenza virus (H5N1) remains a major global concern. 13 The development of safe and efficient avian influenza vaccines for animal and human use is essential for preventing panzootic influenza and pandemics worldwide. Protective immunity against avian influenza depends largely on development of the immune response against hemagglutinin glycoprotein.…”