Vaccines against Major Poultry Viral Diseases: Strategies to Improve the Breadth and Protective Efficacy

Abstract

The poultry industry is the largest source of meat and eggs for human consumption worldwide. However, viral outbreaks in farmed stock are a common occurrence and a major source of concern for the industry. Mortality and morbidity resulting from an outbreak can cause significant economic losses with subsequent detrimental impacts on the global food supply chain. Mass vaccination is one of the main strategies for controlling and preventing viral infection in poultry. The development of broadly protective vaccines against avian viral diseases will alleviate selection pressure on field virus strains and simplify vaccination regimens for commercial farms with overall savings in husbandry costs. With the increasing number of emerging and re-emerging viral infectious diseases in the poultry industry, there is an urgent need to understand the strategies for broadening the protective efficacy of the vaccines against distinct viral strains. The current review provides an overview of viral vaccines and vaccination regimens available for common avian viral infections, and strategies for developing safer and more efficacious viral vaccines for poultry.

Keywords: broadly protective viral vaccines; cross protection; engineered viral vaccines; poultry viral infections; vaccine efficacy; viral vaccine vectors.

Figure 1

Schematic diagram of broadly protective vaccine designs. (A) The three major steps to the creation of neutralizing epitopes-based vaccines. Major neutralizing epitopes on the protective antigen are identified with neutralizing antibodies. Next, the distribution of the identified epitopes is analyzed across multiple lineages for the selection of optimal vaccine strains or enable the modification of a vaccine antigen to best represent the neutralizing epitopes of antigenic subtypes. (B) Computationally optimized broadly reactive antigen (COBRA). The consensus sequences for each genotypic group are realigned to generate a secondary consensus, which is then aligned to obtain a single final consensus sequence based on conserved regions, designated as COBRA. (C) The ‘chimeric’ approach involves sequential vaccination with vaccines containing HA heads of distinct influenza subtypes grafted onto a conserved HA stalk for universal or broad protection against AIV subtypes. (D) The ‘mosaic’ approach replaces variable immunodominant antigenic sites with equivalents from other influenza HA subtypes to produce an immunogen with conserved epitopes in both the stalk and head domains.