Co-administration of heat labile enterotoxin of Escherichia coli enhances systemic cellular immune response to Newcastle disease virus in chicken

Newcastle disease (ND) causes substantial losses to poultry industry through mortality and reduction in productivity parameters such as egg production and meat quality. Improved vaccines that provide stronger and longer duration of immunity are desirable. In the present study we evaluated the efficacy of heat labile enterotoxin of Escherichia coli (LT) adjuvant to modulate the immune responses to replicating Newcastle disease vaccine in chickens. The lentogenic ND vaccine co-administered with LT was inoculated into chicken through intranasal route and systemic anti-viral humoral and cell mediated immune responses were assayed. Addition of LT to lentogenic NDV vaccine elicited higher cell mediated immune response compared to chicken vaccinated with vaccine alone. However, anti-viral antibody levels were not influenced by inclusion of LT adjuvant in lentogenic vaccine. Overall, the study shows adjuvant modulation of immune responses to live replicating vaccines in chicken.