Research Projects

Fowl Adenoviruses (FAdV), of the DNA viral genus Aviadenovirus, cause major pathology in chicken, manifesting as inclusion body hepatitis (IBH), hepatitis-hydropericardium syndrome (HHS), and gizzard erosion (GE). The Fowl adenoviruses have been detected in India from 1971 and Inclusion body hepatitis has been described in Indian poultry since 1981. Twelve serotypes of FAdV have been characterized (1 to 7, 8a, 8b, 9 to 11), which are grouped in five species (A to E). Many serotypes have been recorded in India, prominently FAdV4, FAdV8, and FAdV11. Of these serotypes, the prevalence of FAdV11 of species D is increasing in India in recent times. FAdV11 causes inclusion body hepatitis and is associated with a decrease in productivity, increased infections, and mortality, which are mainly observed in young broilers. FAdV11 is the most prevalent serotype of FAdV causing IBH. Mixed infections with multiple serotypes in the same bird has also been recorded. Significant economic losses to the Indian poultry sector across the country due to FAdV infections has been reported earlier. Inactivated vaccines were developed in the mid 1990’s in India and are traditionally used to control FAdV infections in broilers and breeders. The inactivated vaccines use FAdV4 serotypes and sometimes FAdV8 serotypes. Despite vaccination, the diseases due to FAdV persist even today in India, often causing severe economic loss. The factors contributing to the inadequacy of existing inactivated vaccines are; (i) The inability of inactivated vaccines to stimulate cell mediated cytotoxic T cell response that is essential to clear the virus infection. (ii) The inactivated vaccines do not stimulate immunity against non structural proteins in the FAdVs which have a large genome with more than 40 genes out of which only three are structural proteins; hexon, penton base and fibre (iii) The inherent diversity in the FAdV serotypes (especially, variations in structural proteins) and their ongoing evolution combined with the lack of generation of cross neutralizing antibodies by inactivated vaccines makes them ineffective. There are no live attenuated vaccines which can generate a robust immune response to control FAdV. The adenoviral genomes are well known to contain genes that are non-essential for viral replication. Removal of these non-essential genes will result in attenuation of the virulence without affecting viral replication. A gene-deleted FAdV vaccines will stimulate cell mediated cytotoxic T cell response that is essential to clear the virus infection. To address the gap in the lack of a robust vaccine, we propose developing a gene-deleted FAdV11 vaccine. Further, this vaccine will also serve as a vector platform for other poultry pathogens. The viral vector platforms based on avian herpesviruses, fowlpox virus and Newcastle disease virus have already made their mark as vectors for poultry vaccines. However, adenovirus-based vector platforms have not yet been commercialized in poultry vaccines. Hence, developing a gene-deleted FAdV11 vaccine, will address the requirement for an efficient vaccine for FAdV11-induced Inclusion body hepatitis and also enable the development of a novel viral vector platform for poultry vaccines with broader application.