Comparative evaluation of 4 commercial modified‐live porcine reproductive and respiratory syndrome virus (PRRSV) vaccines against heterologous dual Korean PRRSV‐1 and PRRSV‐2 challenge

Abstract

Background Four commercial porcine reproductive and respiratory syndrome virus (PRRSV) modified‐live vaccines (MLV) was compared to protect growing pigs against dual challenge of PRRSV‐1 and PRRSV‐2. Methods Two of the vaccines were based on PRRSV‐1, and two on PRRSV‐2. A total of 72 PRRSV‐naïve pigs were divided into six groups (12 pigs/group). Results Two PRRSV‐1 MLV‐vaccinated and two PRRSV‐2 MLV‐vaccinated groups reduced significantly (p < .05) genomic copies of PRRSV‐1 in their sera compared to the unvaccinated challenged group. Two PRRSV‐2 MLV‐vaccinated groups reduced significantly (p < .05) fewer genomic copies of PRRSV‐2 in their sera whereas two PRRSV‐1 MLV‐vaccinated groups were unable to reduce genomic copies of PRRSV‐2 compared to unvaccinated challenged groups. Two PRRSV‐1 MLV‐vaccinated groups induced a stronger PRRSV‐1 specific IFN‐γ‐SC response, while two PRRSV‐2 MLV‐vaccinated groups induced a stronger PRRSV‐2 specific IFN‐γ‐SC response. Two PRRSV‐2 MLV‐vaccinated groups showed significantly (p < .05) lower mean macroscopic and microscopic lung lesion scores compared to two PRRSV‐1 MLV‐vaccinated groups. Conclusions These data demonstrated that two PRRSV‐2 vaccines were efficacious and exhibited similar protection while, two PRRSV‐1 vaccines were largely ineffective against the dual challenge.

Efficacy of the Synergy Between Live-Attenuated and Inactivated PRRSV Vaccines Against a NADC30-Like Strain of Porcine Reproductive and Respiratory Syndrome Virus in 4-Week Piglets

“…According to one farm owner's description, the outbreak of PRRS due to NADC30-like infections in a farrowfinish farm with a 2,000-sow inventory resulted in over 2 million RMB losses in 2020. The Ingelvac PRRS R MLV vaccine has been shown to provide cross-protection against over 10 genetically diverse PRRSV isolates, including several fieldisolated NADC30-like strains currently circulating in China (26,(28)(29)(30)(40)(41)(42). However, compared with homologous protection, lower protection was observed in the heterologous challenge groups (19).…”

The Ability of Porcine Reproductive and Respiratory Syndrome Virus Isolates to Induce Broadly Reactive Neutralizing Antibodies Correlates With In Vivo Protection

“…PRRSV-2 isolate, and cross-protection between PRRSV-1 and PRRSV-2 is considered insignificant, as demonstrated in different studies carried out in adult sows (38,39), boars (40,41), and piglets (42,43). This is probably due to the enormous genetic divergence between the two PRRSV species (14).…”

“…However, it should be mentioned that the characteristics of the PRRSV isolates used for the secondary exposure in some of those groups might have also contributed to the outcome of infection. Thus, the pigs of group A.2 were exposed to a PRRSV-2 isolate, and cross-protection between PRRSV-1 and PRRSV-2 is considered insignificant, as demonstrated in different studies carried out in adult sows ( 38 , 39 ), boars ( 40 , 41 ), and piglets ( 42 , 43 ). This is probably due to the enormous genetic divergence between the two PRRSV species ( 14 ).…”

Porcine Reproductive and Respiratory Syndrome Modified Live Virus Vaccine: A “Leaky” Vaccine with Debatable Efficacy and Safety

“…At the individual level, MLV vaccination usually cannot induce sterilizing immunity to completely block the infection of heterologous strains [ 75 , 104 , 105 , 106 , 107 ]. However, many experimental vaccination-challenge trials or field studies have indicated that PRRSV vaccination can provide partial protection against heterologous strains, shown as delaying the onset of viremia, reducing the duration of viral shedding and significantly decreasing viral load throughout infection, not showing severe clinical signs as unvaccinated animals [ 75 , 97 , 106 , 108 , 109 , 110 , 111 , 112 , 113 , 114 ].…”