A bivalent porcine circovirus type 2 (PCV2), PCV2a-PCV2b, vaccine offers biologically superior protection compared to monovalent PCV2 vaccines

Abstract

Recent publications suggest PCV2 vaccine-induced protection is superior when the vaccine and challenge are closely matched. PCV2’s evolutionary rate, propensity for recombination, and genotype shifting, all provide rationale for modernizing PCV2 vaccines. One mechanism to increase a vaccine’s epitope breadth is by designing a bivalent vaccine. The objective of these studies was to evaluate efficacy of a monovalent (PCV1-2 chimera, cPCV2a or cPCV2b) and bivalent (cPCV2a–cPCV2b) vaccine in terms of homologous and heterologous efficacy. In Study A, pigs were vaccinated with cPCV2a or saline and challenged with PCV2a or PCV2b. In Study B, pigs were vaccinated with cPCV2a, cPCV2a–cPCV2b bivalent, or saline, and challenged with PCV2a. In Study C, pigs were vaccinated with cPCV2b, cPCV2a–cPCV2b bivalent, or saline, and challenged with PCV2b. In all studies vaccines and saline were administered intramuscularly to pigs at three to four weeks of age. Virulent PCV2b or PCV2a was administered to all animals approximately three weeks post-vaccination. Both mono and bivalent vaccinated groups demonstrated significantly lower viremia, percent of animals ever viremic, percent of animals with lymphoid depletion and/or histiocytic replacement, and percent of animals with PCV2 colonization of lymphoid tissues compared to saline controls. In Study A, a biologically relevant, though not significantly different, improvement in homologous versus heterologous protection was observed. In Studies B and C, biologically superior efficacy of the bivalent cPCV2a–cPCV2b vaccine compared to either monovalent vaccine was demonstrated. Taken together, cross-protection among mismatched PCV2 vaccine and challenge genotypes is not 100%; a bivalent PCV2 vaccine may provide the best opportunity to broaden coverage to circulating strains of PCV2.

H1N1 G4 swine influenza T cell epitope analysis in swine and human vaccines and circulating strains uncovers potential risk to swine and humans

“…While this study does not absolutely confirm the relevance of the EpiCC tool for the prediction of human and swine influenza vaccine efficacy, a relationship between EpiCC scores and vaccine efficacy is observed and could be used to establish a threshold for vaccine efficacy in the context of European vaccine strains. In a separate study, EpiCC correctly predicted the efficacy of a novel porcine circovirus type 2 (PCV2) viral vaccine against circulating strains of PCV2 in swine 40,41 . That prospective study and this retrospective analysis of G4 influenza serve to illustrate the utility of EpiCC analysis for additional prospective studies of existing vaccine strains against emergent strains.…”

Efficacy Studies of a Trivalent Vaccine Containing PCV-2a, PCV-2b Genotypes and Mycoplasma hyopneumoniae When Administered at 3 Days of Age and 3 Weeks Later against Porcine Circovirus 2 (PCV-2) Infection

“…Although this needs to be demonstrated at an efficacy level, these data may suggest that PCV2b-based vaccines could offer better protection against PCV-2d compared to PCV-2a-based vaccines [70]. In fact, in a recent study by Bandrick et al [43], animals vaccinated with a cPCV-2a/cPCV-2b bivalent vaccine showed higher levels of protection compared to PCV-2a and PCV-2b monovalent vaccines against PCV-2a and PCV-2b challenges. Animals treated with the bivalent vaccine showed less (although non-significant) PCV-2 shedding in faeces, evershed PCV-2 in their faeces, viraemia and ever-viraemic pigs compared to animals treated with the monovalent vaccine.…”

“…Although PCV-2 vaccines are responsible for PCVD reduction in pig herds, they do not confer full protection and do not eliminate virus replication and transmission [10]. Due to this, PCV-2 vaccination may induce vaccine-escape variants, causing the overall prevalence of PCV-2 positive herds to become unchangeable [10,40,42], and promoting wild-type strains that can circulate in a less susceptible population [43]. Moreover, it has been shown that PCV-2 monovalent vaccines induce protection against a homologous infection but with a lack of full crossprotection against other PCV-2 genotypes [41,43].…”

“…Due to this, PCV-2 vaccination may induce vaccine-escape variants, causing the overall prevalence of PCV-2 positive herds to become unchangeable [10,40,42], and promoting wild-type strains that can circulate in a less susceptible population [43]. Moreover, it has been shown that PCV-2 monovalent vaccines induce protection against a homologous infection but with a lack of full crossprotection against other PCV-2 genotypes [41,43]. Taken together, a bivalent vaccine containing PCV-2a and PCV-2b genotypes would be an interesting option to protect the population against the most clinically relevant PCV-2 genotypes [44].…”

Porcine Circovirus Type 2 Vaccines: Commercial Application and Research Advances

“…To increase the width of the vaccine epitope, a PCV2a-PCV2b bivalent vaccine was developed. The cross-protection of the PCV2 vaccine against different genotypes was not satisfied, but the bivalent PCV2 vaccine provided superior protection [68]. The porcine IL-18 gene, PCV2 Cap, and M-like protein (SzP) gene of Streptococcus equi ssp.…”