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 rF PV-gB/R alone and in combination with herpesvirus of turkey (HVT) preparati ons were evaluated for their protective efficacy against challenge with ver y virulent MDV strains Md5 and RB1B in different chickens. The rFPV-gB/R al one induced protection comparable to that by HVT vaccines in both Ab(-) SPF chickens and Ab(+) production chickens. Significant protective synergism w as observed in one of these two types of commercial production chickens whe n rFPV-gB/R was combined with HVT of either cell-associated or cell-free pr eparations. Immunogenesis studies showed that rFPV-gB/R, just like conventi onal vaccines, significantly reduced the level of viremia, splenocytes infe ction and feather follicle shedding of challenge virus in vaccinated chicke ns.