Efficacy of various Marek's disease vaccines protocols for prevention of Marek's disease virus-induced immunosuppression. Issue 35 (29th July 2016)

• Record Type: Journal Article
• Authors: Faiz, Nik M.; Cortes, Aneg L.; Guy, James S.; Fogle, Jonathan E.; Gimeno, Isabel M.
• Is Part Of: Vaccine. Volume 34:Issue 35(2016)
• Page Start: 4180
• Page End: 4187
• Publication Date: 2016-07-29
• Subjects: MD Marek's disease -- MDV Marek's disease virus -- MDV-IS Marek's disease virus-induced immunosuppression -- ILT infectious laryngotracheitis -- ILTV infectious laryngotracheitis virus -- PFU plaque forming units -- CEO chicken embryo origin -- CEF chicken embryo fibroblasts -- CKC chicken kidney cells; MDV -- Control -- ILTV -- Immunosuppression -- Immune system -- Vaccine; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2016.06.061
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Protection against tumors is not enough to protect against late-MDV-IS induced by vv+MDV. Currently used vaccine protocols cannot protect against late-MDV-IS induced by vv+MDV. Experimental vaccine Md5ΔMEQ protect against both tumors and late-MDV-IS induced by vv+MDV. Abstract: Marek's disease virus (MDV) induces tumors and severe immunosuppression in chickens. MDV-induced immunosuppression (MDV-IS) is very complex and difficult to study. In particular, the late MDV-IS (late-MDV-IS) is of great concern since it can occur in the absence of lymphoid organ atrophy or gross tumors. We have recently developed a model to reproduce late-MDV-IS under laboratory conditions. This model measures MDV-IS indirectly by assessing the effect of MDV infection on the efficacy of infectious laryngotracheitis (ILT) vaccination; hence the name late-MDV-IS ILT model. In this study, we have used the late-MDV-IS ILT model to evaluate if MD vaccination can protect against late-MDV-IS. One experiment was conducted to determine whether serotype 1 MD vaccines (CVI988 and Md5ΔMEQ) could induce late-MDV-IS by themselves. Three additional experiments were conducted to evaluate efficacy of different MD vaccines (HVT, HVT+SB-1, CVI988, and Md5ΔMEQ) and different vaccine protocols (day-old vaccination, in ovo vaccination, and double vaccination) against late-MDV-IS. Our results show that none of the currently used vaccine protocols (HVT, HVT+SB-1, or CVI988 administered at day of age, in ovo, or in double vaccination protocols) protected against late-MDV-IS induced by vv+MDV strains 648A and 686. Experimental vaccine Md5ΔMEQ administered subcutaneously at one day of age was the only vaccine protocol that significantly reduced late-MDV-IS induced by vv+MDV strain 686. This study demonstrates that currently used vaccine protocols confer high levels of protection against MDV-induced tumors (protection index = 100), but do not protect against late-MDV-IS; thus, commercial poultry flocks could suffer late-MDV-IS even in complete absence of tumors. Our results suggest that MDV-IS might not be related to the development of tumors and novel control methods are needed. Further evaluation of the experimental vaccine Md5ΔMEQ might shed light on protective mechanisms against late-MDV-IS.