Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2012
Publication Date: January 15, 2012
Citation: Zhang, H., Chang, S., Dunn, J.R., Heidari, M., Song, J., Fulton, J. 2012. Host genetic resistance sustains HVT protective efficacy comparable to CV1988/Rispens' in lines of chickens relatively resistant to Marek's disease. Plant and Animal Genome Conference. Available: https://pag.confex.com/pag/xx/webprogram/Paper3980.html. Technical Abstract: Marek’s disease (MD) is a continual threat to the poultry industry worldwide as the MD virus continues to mutate and increase in virulence. MD and the economic losses it causes have been controlled primarily by massive use of vaccines since the 1970s. Based on the antigenic and pathogenic differences of the viruses from which the vaccines were derived, commonly used MD vaccines are classified into three serotypes, known as serotype 1, 2, and 3 MD vaccines. This study was designed to compare the protective efficacy of serotype 1 and serotype 3 vaccines against a very virulent plus strain of Marek’s disease virus (vv+MDV) challenge in experimental and commercial lines of chickens. Chickens from two experimental lines known to differ in their susceptibility and resistance to MD and two commercial production lines (one white egg layer (WL) and one brown egg layer (BL)) were challenged under controlled experimental conditions. Chickens from each of the lines were divided into five groups. One group was unvaccinated. The other four were vaccinated with one of two HVT or one of two CVI988/Rispens vaccines following manufacturer’s instructions. All groups were then challenged with the vv+MDV, 648A. The two HVT and two CVI988/Rispens conveyed protective indices of 82%, 86%, 66%, and 72%, respectively, in Line 6 chickens (resistant); 40%, 54%, 46%, and 76% in WL chickens; 57%, 46%, 50%, and 92% in BL chickens; but 0%, 10%, 27%, and 69% in Line 7 chickens (susceptible). With the exception of one of the two CVI988/Rispens vaccines in the two commercial lines, our data showed serotype 3 HVT vaccine largely conveyed comparable protective efficacy as did CVI988/Rispens in the relatively MD resistant lines of chickens but little or no protection as compared to CVI988/Rispens in the highly susceptible line of chickens (Line 7). The difference of HVT protective efficacy between the resistant and susceptible lines was striking. Further investigations are warranted to explore genetic and epigenetic factors underlying the protective efficacy differences between MD resistant and susceptible lines of chickens.