Vaccination of piglets at 2 and 3 weeks of age with Ingelvac PRRSFLEX® EU provides protection against heterologous field challenge in the face of homologous maternally derived antibodies

Abstract

BackgroundDue to difficulties in eradicating porcine reproductive and respiratory syndrome (PRRS) linked to biosecurity challenges, transmission of the virus and the lack of efficient DIVA vaccines, successful control of PRRS requires a combination of strict management measures and vaccination of both sows and piglets. The present study aimed to assess the efficacy of a recently developed MLV vaccine (Ingelvac PRRSFLEX® EU) in piglets at 2 and 3-weeks of age in the presence of homologous maternally derived antibodies as the dams were vaccinated with the same vaccine strain (ReproCyc® PRRS EU).MethodsThe study was carried out on a Hungarian farrow to finish farm naturally infected with PRRSv. The study was designed as a blind, placebo controlled side by side trial. ORF5 sequence similarity of the vaccine strain and the resident field strain was 87.8 %. PRRS specific real-time quantitative PCR was performed from serum samples to measure both the viral load and the frequency of virus positive animals.ResultsAt the time of the natural infection observed in the control group at 10–12 weeks of age, the number of viraemic animals did not increase significantly in the vaccinated group. To understand the infection dynamics, positive PCR samples with low Ct values were sequenced (ORF5) and the data analysis indicated the circulation of wild type virus in both groups, however wild type virus was only found in non-vaccinated animals.ConclusionsOur data indicate that piglets vaccinated at as early as 2 weeks of age with Ingelvac PRRSFLEX® EU were protected both in terms of proportion of viraemic animals and viraemia levels. It has to be highlighted that these results were achieved in piglets with high levels of homologous maternally derived antibodies (MDA) at the time of vaccination.

Initial vaccination and revaccination with Type I PRRS 94881 MLV reduces viral load and infection with porcine reproductive and respiratory syndrome virus

“…Although genetic distance in the ORF5 gene locus is not a stoichiometric indicator of the likelihood of protection, the protection demonstrated in this study with the chosen genetic distance of less than 87% homology between the vaccine and challenge should provide a good level of assurance that the vaccine could protect against heterologous PRRSV strains. As in previous cases, this should also be verified in field studies [ 27 ].…”

“…Some animals did not test positive by either RT-qPCR or ELISA and showed the same level of protection upon challenge compared with animals that had seroconverted. Incomplete seroconversion alongside full protection from PRRS has already been observed in other studies [ 27 ] and most likely reflects variability in immune responses between animals.…”

Gilt Vaccination with a Mixed Administration of a PRRS MLV and a PPV1 Subunit Vaccine Protects against Heterologous PRRSV1 Infection and Prevents Detrimental Effects on Piglet Performance

“…However, challenge-induced viremia reduction was not linked to seropositivity at challenge in any of the studies. Incomplete seroconversion alongside full protection from PRRS has already been described in other studies and most likely reflects the relevant role of the cell-mediated immunity in PRRSV clearance from the blood as well as the variability in immune responses between animals [11,21,22].…”

Maternally-derived neutralizing antibodies reduce vaccine efficacy against porcine reproductive and respiratory syndrome virus infection

“…This interference of MDNAs with postvaccination immune response suggested weak protection against PRRSV infection of piglets vaccinated in presence of high MDNA levels that could explain the lower vaccine efficacy observed in the field. Previous studies reported that vaccination in piglets with high MDA levels had no impact on vaccine efficacy but neutralizing antibodies (NAs) were not considered [15]. In the present study, piglets were vaccinated in the presence of low or high MDNA levels and further challenged with a wild PRRSV-1 to assess the impact of MDNAs on the efficacy of PRRSV-1 MLV vaccination.…”