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Author: Ahmed, Rofique × End date: 2022 × Start date: 2022 × Type: Thesis × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    Evaluation of immune response in broiler chicks immunized with a minimum cold chain dependent Newcastle disease virus formulation
    (College of Veterinary Science, Assam Agricultural University, Khanapara Campus, 2022-09) Ahmed, Rofique; Nath, Mrinal Kr
    Among the infectious diseases of poultry, Newcastle disease (ND) is considered one of the most economically fatal viral diseases causing morbidity and mortality of about 90-100% in its velogenic form. Only through vaccination the economic menace and clinical condition caused by NDV can be controlled. But commercially available vaccines against ND are generally thermolabile and lose their potency if kept at room temperature (25°C) for 1-2 hours. The recent COVID-19 pandemic clearly showed the weakness of the vaccine supply chain and its maintenance. The lack of thermostable formulations is one of the major limitations that the COVID-19 pandemic has brought to light. Addressing the need for thermostable vaccine development, the present study was carried out with the study of the thermal stability of a thermostable NDV vaccine formulation (As/Km/19/44) and its immunogenic potential in broiler chicks. In the present study, after receiving the thermoadapted ND seed virus (As/Km/19/44) confirmation was done by haemagglutination test (HA) and by Reverse Transcription- Polymerase Chain Reaction (RT-PCR) by the amplification of the 363 bp partial F gene. After confirmation, a thermal stability test of the seed virus (As/Km/19/44) was done by subjecting the isolate at 40°C and 56°C for 120 minutes respectively. The thermoadapted ND seed virus (As/Km/19/44) retained its HA activity and infectivity at 40°C up to 120 minutes without any decay in virus titre and at 56°C, the thermoadapted ND seed virus (As/Km/19/44) retained its half-life for 83.13 and 96.60 minutes in terms of HA activity and infectivity respectively. Further, lyophilization of the seed virus (As/Km/19/44) was done using chemical excipients viz., Pullulan (10% w/v), Trehalose (0.5M) and Inulin (45mg/ml) to prepare the immunogenic formulation. After formulation, the comparative HA activity and infectivity before and after lyophilization showed no significant difference at P<0.05. The lyophilized NDV immunogenic formulations (As/Km/19/44) were grouped and kept at different temperatures viz., 4ºC for six months, room temperature (about 25°C) for six months, 37ºC for one month, and 56ºC for 15 days for evaluating the thermal stability. At 4ºC, no fall of virus titer in terms of HA activity and infectivity were recorded for up to 6 months. The estimated half-life period of the live NDV immunogenic formulation exposed at room temperature (around 25°C), 37°C and 56°C in terms of HA activity and infectivity was found to be 1008 and 1037; 50.03 and 71.51; 2.194 and 2.764 days respectively. For evaluation of humoral immune response, the minimum cold-chain dependent NDV formulation (As/Km/19/44) was administered in experimental chicks through an intra-nasal route with a standard dose of 106EID50 per chick and compared with the commercial LaSota® vaccine. The HI (log2) and I-ELISA (log10) antibody titers in the serum samples of the experimental chicks at different days post-immunization revealed that there was no significant difference between overall humoral immune response in immunized chicks with minimum cold chain dependent live NDV immunogenic formulation As/Km/19/44 and commercially available LaSota® vaccine strain at P<0.001. Therefore, the minimum cold-chain-dependent NDV immunogenic formulation As/Km/19/44 can be recommended as a suitable live thermostable ND vaccine candidate for prevention and control of ND in areas where cold chain facilities are usually unreliable and can lead to the reduction of vaccine wastage, increase in vaccine efficacy, reduction in cost, ease of application and transportability.