Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2011
Publication Date: 9/1/2011
Citation: Chang, S., Ding, Z., Dunn, J.R., Lee, L.F., Heidari, M., Song, J., Ernst, C.W., Zhang, H. 2011. A comparative evaluation of the protective efficacy of rMd5-delta-Meq and CV1988/Rispens against a vv+ strain of Marek's disease virus infection in a series of recombinant congenic strains of white leghorn chickens. Avian Diseases. 55(3):384-390. Interpretive Summary: Marek’s disease (MD), an ongoing concern of the poultry industry, is caused by MD virus. The economic damage of MD to the world poultry industry is estimated to be a billion U.S. dollars annually. The present control measure of MD is through vaccination. The best commercially available MD vaccine today is known as CVI988/Rispens and has been used by the industry in the U.S. since the 1990s. In this study, a new MD vaccine, developed at our laboratory and named rMd5deltaMeq, was evaluated in 19 relatively resistant lines of chickens against challenge with a very virulent strain of MD virus. Data from this study showed that the new candidate vaccine provided much better protection against MD in all chicken lines. This study provided evidence that rMd5deltaMeq can be used as a vaccine for better control of MD, regardless of line of chickens used.
Technical Abstract: Marek’s disease (MD) is a lymphoproliferative disease of domestic chickens caused by a highly infectious, oncogenic alpha-herpesvirus known as Marek’s disease virus (MDV). MD is presently controlled by vaccination. Current MD vaccines include attenuated serotype 1 strains (e.g. CVI988/Rispens), avirulent serotype 2 (SB-1), and serotype 3 (HVT) MDV strains. In addition, recombinant MDV strains have been developed as potential new and more efficient vaccines to sustain the success of MD control in poultry. One of the candidate recombinant MDV strains, named rMd5deltaMeq, was derived from Md5, a very virulent strain of MDV, lacking the MDV oncogene Meq. Our earlier reports suggest that rMd5deltaMeq provided protection equally well or better than commonly used MD vaccines in experimental and commercial lines of chickens challenged with very virulent plus (vv+) strains of MDV. In this study, maternal antibody positive (trial 1) and negative (trial 2) chickens from a series of relatively MD resistant lines were either vaccinated with the rMd5deltaMeq or CVI988/Rispens followed by infection of a vv+ strain of MDV, 648A, passage 10. This report presents experimental evidence that the rMd5deltaMeq protected significantly better than the CVI988/Rispens (P < 0.01) in the relatively resistant experimental lines of chickens challenged with the vv+ strain of MDV. Together with early reports, the rMd5deltaMeq appeared to provide better protection, comparing with the most efficacious, commercially available vaccine, CVI988/Rispens, for control of MD in lines of chickens regardless of their genetic background.