Location: Avian Disease and Oncology Laboratory
Title: Host genetic resistance to Marek’s disease sustains protective efficacy of herpesvirus of turkey in both experimental and commercial lines of chickens Authors
Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2014
Publication Date: February 13, 2014
Citation: Chang, S., Xie, Q., Dunn, J.R., Ernst, C.W., Song, J., Zhang, H. 2014. Host genetic resistance to Marek’s disease sustains protective efficacy of herpesvirus of turkey in both experimental and commercial lines of chickens. Vaccine. 32(16):1820-1827. Available: http://www.sciencedirect.com/science/article/pii/S0264410X14001558. Interpretive Summary: Marek’s disease, a disease of poultry caused by Marek’s disease viruses and controlled by vaccination, remains a threat to the poultry industry. This study through a series of experiments examined different vaccine protective efficiency against the disease in chickens with varied genetic backgrounds. Data from this study indicated herpesvirus of turkey, commonly known as HVT, the first generation and less expensive Marek’s disease vaccine, conveys equal protection against Marek’s disease as does the industry’s golden standard Marek’s disease vaccine, CVI988/Rispens, in chickens that are relatively resistant to the disease. This finding provides experimental evidence supporting the theory that the genetic background of chickens plays an important role in modulating vaccine protective efficiency and inspiring consideration for alternative strategies in selection and use of vaccines to control infectious diseases.
Technical Abstract: Marek’s disease (MD) remains a continual threat to the poultry industry worldwide as the MD virus continues evolving in virulence. MD has been controlled primarily by intensive use of vaccines since 1969. Based on the antigenic and pathogenic differences of the viruses that the vaccines were derived from, commercially available MD vaccines are classified into three categories, MDV-1, -2, and -3 vaccines. This study was designed to compare the protective efficacy of MDV-1 (CVI988/Rispens) and MDV-3(HVT) vaccines against challenge of a very virulent plus strain of Marek’s disease virus (vv+MDV) in experimental and commercial egg-layer lines of chickens under controlled experimental conditions. The two experimental lines (63and 72) of chickens carry a uniform MHC B*2 haplotype and are known to differ in resistance to MD. One of the two commercial egg-layer lines (WL and BL) segregates for three MHC haplotypes (B*2, B*15, and B*21); the other is unclear. MD incidences of the unvaccinated groups of both experimental lines and both commercial lines were 100% or close to 100% induced by the vv+MDV, 648A.Survived day patterns of the unvaccinated groups significantly differed between the two experimental lines, but did not between the two commercial lines, which suggested the two experimental lines do differ in resistance to MD but not between the two commercial lines. At manufacturers’ recommended vaccine dosage, two HVTs conveyed comparable protection for the MD resistant line 63chickens as did both CVI988/Rispens used in this study. The two HVTs also conveyed comparable protection for both commercial lines of chickens as did one of two CVI988/Rispens (CVI988/Rispens-A). At a 2000 PFU uniform dose, HVT and CVI988/Rispens again conveyed comparable protection for the MD resistant experimental line of chickens. The findings suggest vaccine protective efficacy is modulated by factors including the types and the sources of vaccines and the genetic backgrounds of chickens. The findings also suggest HVT delivers equal protection in MD resistant lines of chickens as does the industry-recognized golden standard of MD vaccine, CVI988/Rispens.