Chong Li and colleagues from the University of Minnesota provide new insights for the potential use of the heterologous prime-boost vaccination strategy to control swine infuenza A virus (IAV) infection in pigs by bringing us a research article published in Veterinary Research.
- Heterologous prime-boost vaccination has the potential to deal with diverse IAV infection in multiple animal models.
- Pigs in the heterologous prime-boost vaccination group had more favorable outcomes consistent with a better response against virus challenge (H1N1 and H3N2 IAV) than non-vaccinated pigs.
- Similarly, a multivalent heterologous inactivated vaccine boost to pigs following a single live attenuated IAV vaccine (LAIV) administration was also beneficial.
- More studies are still needed to validate the concept of heterologous prime-boost to control IAV under feld conditions.
Currently, vaccination is the primary measure to control swine infuenza A virus (IAV) infection in pigs, and whole-cell inactivated vaccines (WIV) remain the most commonly used licensed vaccines. However, a live attenuated infuenza vaccine (LAIV) became commercially available in the US in 2018. In this study, the protective efficacy of heterologous prime-boost vaccination with WIV and LAIV vaccines in a swine model against H1 and H3 IAV co-infection was evaluated.
A total of ninety, 3-week-old, IAV-free pigs were randomly allocated into 8 treatment groups distributed in two separate studies. The first study included only pigs vaccinated with commercial (COM) or autogenous (AUT) WIV and had five diferent treatment groups: COM/COM, AUT/AUT, AUT/COM, COM/AUT and no vaccination but challenged (NO VAC/CHA). The second study included pigs vaccinated with the LAIV and two treatment groups: LAIV/COM and LAIV/NONE (NONE=no boost vaccination). In addition, six pigs from NO VAC/NO CHA group served as unvaccinated negative controls. When applicable, pigs were vaccinated against infuenza using diferent prime-boost vaccination protocols at 3 and/or 6 weeks of age. Two seeder pigs (one H1 seeder and one H3 seeder) were commingled with the pigs in each room, thus, they served as infection sources to the vaccinated and NO VAC/CHA pigs. All pigs were euthanized and necropsied at 7 days post-contact with the seeder pigs.
For more information regarding the experimental design, sample collection and testing, please refer back to the full manuscript on the journal’s webpage.
Results & Discussion
The heterologous AUT/COM prime/boost vaccine combination resulted in lower numbers of infected pigs than a WIV homologous prime/boost vaccine combination when compared to NO VAC/CHA pigs. Among the LAIV groups, lower infection levels were also observed in pigs receiving heterologous LAIV/COM prime/boost vaccination compared to a single administration of LAIV. Furthermore, the heterologous prime-boost vaccination protocols showed an expanded antibody response to both H1 and H3 challenge strains as demonstrated by the higher hemagglutinin inhibition (HI) titers especially in pigs from AUT/COM and LAIV/COM treatment groups.
Overall, the pigs in the treatment group that received the heterologous AUT/COM vaccination had more favorable outcomes consistent with a better response against the virus challenge than non-vaccinated pigs and compared to all the other WIV groups. The responses seen in the heterologous LAIV/COM
treatment group were also more favorable than those responses observed compared to the treatment group receiving the single dose of LAIV vaccine.
To read the results and discussion in more detail, refer to the full manuscript here.
Influenza A viruses evolve rapidly to escape host immunity. In swine, this viral evolution has resulted in the emergence of multiple H1 and H3 influenza A virus (IAV) lineages in the United States (US) pig populations. The heterologous prime-boost vaccination strategy is a promising way to deal with diverse IAV infection in multiple animal models. However, whether or not this vaccination strategy is applicable to US swine to impart immunity against infection from North American strains of IAV is still unknown. We performed a vaccination-challenge study to evaluate the protective efficacy of using multivalent inactivated vaccine and/or a live attenuated IAV vaccine (LAIV) in pigs following multiple prime-boost vaccination protocols against a simultaneous H1N1 and H3N2 IAV infection. Our data show that pigs in the heterologous prime-boost vaccination group had more favorable outcomes consistent with a better response against virus challenge than non-vaccinated pigs. Additionally, delivering a multivalent heterologous inactivated vaccine boost to pigs following a single LAIV administration was also beneficial. We concluded the heterologous prime boost vaccination strategy may potentiate responses to suboptimal immunogens and holds the potential applicability to control IAV in the North American swine industry. However, more studies are needed to validate the application of this vaccination approach under field conditions.