Comparative analysis of routes of immunization of a live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine in a heterologous virus challenge study

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is caused by PRRS virus (PRRSV), which infects primarily the respiratory tract of pigs. Thus intranasal (IN) delivery of a potent vaccine-adjuvant formulation is promising. In this study, PRRS-MLV (VR2332) was coadministered ± an adjuvant Mycobacterium vaccae whole cell lysate or CpG ODN through intramuscular (IM) or IN route as a mist, and challenged with a heterologous PRRSV 1-4-4 IN at 42 days post-vaccination (dpv). At 14 and 26 dpv, vaccine viral RNA copies were one log greater in the plasma of PRRS-MLV IM compared to IN vaccinated pigs, and the infectious replicating vaccine virus was detected only in the IM group. In PRRS-MLV ± adjuvant IM vaccinated pigs, reduced viral RNA load and absence of the replicating challenged virus was observed at 7, 10 and 14 days post-challenge (dpc). At 14 dpc, in BAL fluid ≥5 log viral RNA copies were detected in all the pig groups, but the replicating challenged virus was undetectable only in IM groups. Immunologically, virus neutralizing antibody titers in the plasma of IM (but not IN) vaccine groups was ≥8 against the vaccine and challenged viruses. At 26 dpv, PRRS-MLV IM (without adjuvant) received pigs had significantly increased population of CD4 and CD8 T cells in PBMC. At 14 dpc, relatively increased population of IFN-γ+ total lymphocytes, NK, CD4, CD8 and γδ T cells were observed in the MLV-IM group. In conclusion, PRRS-MLV IM vaccination induced the virus specific T cell response in pigs, but still it is required to improve its cross-protective efficacy.

Th1-biased immunoadjuvant effect of the recombinant B subunit of an <i>Escherichia coli</i> heat-labile enterotoxin on an inactivated porcine reproductive and respiratory syndrome virus antigen via intranasal immunization in mice

“…Current vaccines available for PRRSV prevention include the modified live virus and inactivated vaccines. The PRRSV live attenuated vaccine clinically reduces porcine lung lesions and viral shedding, and confers protection against the homologous virus [14, 26], but does not induce adequate heterologous immunity [9, 29]. More importantly, the PRRSV live attenuated vaccine can potentially revert to virulence [30].…”

Future perspectives on swine viral vaccines: where are we headed?

“…The benefits of alternative routes may include induction of a strong localized/mucosal immune response, especially at the point of virus entry (i.e. respiratory system) [ 101 , 102 ].…”

The Function of the PRRSV–Host Interactions and Their Effects on Viral Replication and Propagation in Antiviral Strategies

“…A total of 54 mutated amino acids were found in CH-1R; among them, 11 and three mutations are located in nsp2 and GP5, respectively [82]. PRRS-MLV can protect homologous viruses and mitigate lung damage but does not induce sufficient heterologous immunity [86]. Compared with PRRSV-1 MLV vaccines, PRRSV-2 MLV vaccines are more effective against both PRRSV-1 and PRRSV-2 infection [87,88].…”