In process quality control factors affecting efficacy of Hydropericardium syndrome virus vaccine

Hydropericardium syndrome (HPS) is common even in the commercial broilers that are vaccinated using locally prepared HPS virus infected liver homogenate (HPS-LH) vaccine. In the HPS-LH vaccine production process, some of the in process quality control factors mitigate its efficacy. The HPS-LH vaccine containing more than 10(4.6) units of bird lethal dose 50 (LD50) when injected to 14 days old broilers and 21 days post vaccination given challenge with infection dose (100 units of LD50 of HPS-LH) showed 100 per cent protection. Moreover, less than 25 doses of the vaccine prepared from one gram of the HPS-LH induced 90 per cent protection in the vaccinated birds. Addition of adjuvant such as oil base (Montanide ISA 70) or aluminum hydroxide gel (AHG) in the vaccine showed additive effect on its efficacy. The birds vaccinated with montanide based HPS-LH vaccine (10(4.6) units of LD50: 25 doses/gram) showed 100 percent protection to challenge infection. The montanide is more effective adjuvant as compared to AHG. Infectivity titer (LD50) of HPS virus infected chicken embryo hepatocyte homogenate (CEHH) was 100 times less 10(2.5) units than that of HPS-LH. Gel based HPS-CEHH vaccine (LD50 titer 10(2.5) units showed poor response in the vaccinated birds (40 per cent protection) as compared to that of gel based HPS-LH vaccine (90 per cent). It is concluded that gel based vaccine prepared from fresh HPS-LH is more effective and economical as compared to that of HPS-CEHH vaccine.