Experimental evaluation of a novel bivalent vaccine against porcine circovirus type 2d and Mycoplasma hyopneumoniae.

The aim of this study was to evaluate the efficacy of a newly developed bivalent vaccine against porcine circovirus type 2d (PCV2d) and Mycoplasma hyopneumoniae. A total of 85 colostrum-fed, conventional 2-week-old pigs derived from sows not previously vaccinated against PCV2 or M. hyopneumoniae were used. The pigs were randomly assigned to seven groups. The bivalent vaccine was administered intramuscularly at 21 days of age according to the manufacturer's instructions. At 49 days of age, pigs in the vaccinated and positive control groups were challenged intranasally with PCV2d or intratracheally with M. hyopneumoniae. Regarding PCV2d infection, vaccinated and challenged pigs exhibited higher neutralizing antibody titers against PCV2d and increased numbers of PCV2d-specific interferon-γ-secreting cells (IFN-γ-SC) compared with unvaccinated and challenged pigs. In addition, vaccinated pigs showed significantly reduced PCV2d viremia and lower lymphoid lesion scores. Regarding M. hyopneumoniae infection, vaccinated and challenged pigs demonstrated higher numbers of M. hyopneumoniae-specific IFN-γ-SC, reduced laryngeal mycoplasmal loads, and decreased mycoplasmal lung lesion scores compared with unvaccinated and challenged pigs. These findings demonstrated that the bivalent vaccine provides effective protection against both pathogens, with particularly marked efficacy against PCV2d, the currently predominant genotype in global swine populations.