Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 23, 2013
Publication Date: December 8, 2013
Citation: Rajao, D., Vincent, A.L., Loving, C.L., Sandbulte, M., Kitikoon, P. 2013. Heterologous challenge of weaned piglets in the presence of maternal derived antibodies results in vaccine-associated enhanced respiratory disease [abstract]. 2013 Conference of Research Workers in Animal Diseases, December 8-10, 2013, Chicago, IL. Paper No. 090. Technical Abstract: Effective vaccine immunization against influenza A viruses (IAV) in pigs in the United States is challenging because of the great antigenic diversity of co-circulating viruses. Maternally derived antibodies (MDA) interfere with vaccine efficacy and can lead to vaccine-enhanced respiratory disease (VAERD) in pigs vaccinated in the presence of MDA. Our aim was to evaluate if MDA alone interferes with IAV infection, clinical disease, and transmission in weaned non-vaccinated piglets. Sows with existing antibodies to 2009 pandemic H1N1 (H1N1pdm09) were boosted with H1N1pdm09 whole inactivated (WIV) or live attenuated (LAIV) vaccine. At three weeks of age, MDA-positive piglets were challenged with homologous H1N1pdm09 or heterologous delta1-H1N2 virus, along with MDA-negative controls. All MDA-positive piglets had high hemagglutinating antibody titers, as well as virus-specific cross-reactive serum IgG at the time of challenge. WIV-MDA piglets were protected from homologous infection with H1N1pdm09 and did not transmit to contact pigs. LAIV-MDA piglets were partially protected from homologous challenge with H1N1pdm09, but they transmitted virus to all their indirect contacts. However, this group had less virus shedding than the naive infected controls. The major finding of this study was that piglets with WIV-derived MDA and challenged with delta1-H1N2 developed VAERD, with more pronounced lung lesions and clinical signs. Two piglets in this group died at 2 days post infection from severe VAERD and respiratory complications. LAIV-derived MDA did not cross-protect piglets against heterologous challenge with delta1-H1N2, however it did not result in VAERD. All pigs in indirect contact with the delta1-H1N2 challenged groups were infected, indicating that mismatched MDA does not mitigate viral shedding and transmission. Our data supports that although homologous vaccine-derived MDA can protect piglets against disease, and to some extent against infection, MDA alone can induce VAERD upon heterologous infection.