A RECOMBINANT FOWLPOX VIRUS VACCINE EXPRESSING GLYCOPROTEIN B GENE FROM CVI988/RISPENS STRAIN OF MDV: PROTECTION STUDIES IN DIFFERENT CHICKENS

Recombinant fowlpox virus (rFPV) was constructed to express glycoprotein B (gB) gene from CVI988/Rispens strain of Marek’s disease virus (MDV). The rFPV-gB/R alone and in combination with herpesvirus of turkey (HVT) preparations were evaluated for their protective efficacy against challenge with very virulent MDV strains Md5 and RB1B in different chickens. The rFPV-gB/R alone induced protection comparable to that by HVT vaccines in both Ab- SPF chickens and Ab+ production chickens. Significant protective synergism was observed in one of these two types of commercial production chickens when rFPV-gB/R was combined with HVT of either cell-associated or cell-free preparations. Immunogenesis studies showed that rFPV-gB/R, just like conventional vaccines, significantly reduced the level of viremia, splenocytes infection and feather follicle shedding of challenge virus in vaccinated chickens.