Laryngotracheitis (LT) is a highly contagious respiratory disease of chickens that produces significant economic losses to the poultry industry. Traditionally, LT has been controlled by administration of modified live
vaccines. In recent years, the use of
recombinant DNA-derived
vaccines using turkey herpesvirus (HVT) and fowlpox virus has expanded, as they protect not only against the vector used but also against LT. However, HVT-based
vaccines confer limited protection against challenge, with emergent very virulent plus
Marek's disease virus (vv+MDV). Serotype 1
vaccines have been proven to be the most efficient against vv+MDV. In particular, deletion of oncogene MEQ from the oncogenic vvMDV strain Md5 (BACδMEQ) resulted in a very efficient
vaccine against vv+MDV. In this work, we have developed two
recombinant vaccines against MD and LT by using BACδMEQ as a vector that carries either the LT virus (LTV) gene
glycoprotein B (gB; BACΔMEQ-gB) or LTV gene
glycoprotein J (gJ; BACδMEQ-gJ). We have evaluated the protection that these
recombinant vaccines confer against MD and LT challenge when administered alone or in combination. Our results demonstrated that both
bivalent vaccines (BACΔMEQ-gB and BACδMEQ-gJ) replicated in chickens and were safe to use in commercial meat-type chickens bearing maternal
antibodies against MDV. BACΔMEQ-gB protected as well as a commercial recombinant (r)HVT-LT
vaccine against challenge with LTV. However, BACδMEQ-gJ did not protect adequately against LT challenge or increase protection conferred by BACΔMEQ-gB when administered in combination. On the other hand, both BACΔMEQ-gB and BACδMEQ-gJ, administered alone or in combination, protected better against an early challenge with vv+MDV strain 648A than commercial strains of rHVT-LT or CVI988. Our results open a new avenue in the development of
recombinant vaccines by using serotype 1 MDV as vectors.