| Ամփոփում: | Marek’s disease virus (MDV) is a highly contagious alphaherpesvirus that causes rapid onset lymphoma in chickens. Marek’s disease (MD) is effectively controlled using vaccination; however, MDV continues to break through vaccinal immunity, due to the emergence of highly virulent field strains. Earlier studies revealed that deletion of the <i>meq</i> gene from MDV resulted in an attenuated virus that protects against MD in chickens challenged with highly virulent field strains. However, the <i>meq</i> deleted virus retains the ability to induce significant lymphoid organ atrophy. In a different study, we found that the deletion of the <i>vIL8</i> gene resulted in the loss of lymphoid organ atrophy in inoculated chickens. Here, we describe the generation of a recombinant MDV from which both <i>meq</i> and <i>vIL8</i> genes were deleted. In vitro studies revealed that the <i>meq</i> and <i>vIL8</i> double deletion virus replicated at levels similar to the parental very virulent plus (vv+) virus. In addition, in vivo studies showed that the double deletion mutant virus (686BAC-ΔMeqΔvIL8) conferred protection comparable to CVI988, a commercial vaccine strain, when challenged with a vv+ MDV virus, and significantly reduced lymphoid organ atrophy, when compared to <i>meq</i> null virus, in chickens. In conclusion, our study describes the development of a safe and effective vaccine candidate for prevention of MD in chickens.
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