Location: Virus and Prion ResearchTitle: Cross-fostering to prevent maternal cell transfer did not prevent vaccine-associated enhanced respiratory disease that occurred following heterologous influenza challenge of pigs vaccinated in presence of maternal immunity
|GAUGER, PHILLIP - Iowa State University|
|ZANELLA, ERALDO - Universidad De Passo Fundo|
|Kehrli Jr, Marcus|
Submitted to: Viral Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2014
Publication Date: 8/28/2014
Citation: Loving, C.L., Brockmeier, S.L., Vincent, A.L., Gauger, P.C., Zanella, E.L., Lager, K.M., Kehrli, Jr., M.E. 2014. Cross-fostering to prevent maternal cell transfer did not prevent vaccine-associated enhanced respiratory disease that occurred following heterologous influenza challenge of pigs vaccinated in presence of maternal immunity. Viral Immunology. 27(7):334-342.
Interpretive Summary: Influenza A virus (IAV) in pigs continues to be a problem for pork producers world-wide. The only current vaccines available on the market for IAV in swine contain inactivated whole virus preparations. This vaccine can protect the pigs against infection with some strains of IAV, but not all. And in some cases, when the pigs do become infected, the disease can be worse. Pork producers routinely vaccinate sows repeatedly to increase transfer of immunity from mother to piglet. But, this immunity can block the effect of the IAV vaccine in the piglet. And again, it can actually alter the immune response to the vaccine such that the vaccine is ineffective and the disease may be worse if pigs get infected. After pigs are born, they nurse/suckle to receive colostrum and milk from their mother, which contains components of the mothers immune system that can prevent disease in the baby pigs. Newborn piglets can be moved to another sow (cross-fostered) to suckle and then, only some components of the mother’s immunity transfers. We used cross-fostering to show that the cellular component of colostrum is not involved in blocking IAV vaccine effects in piglets. Instead, our data shows that antibody is the likely immune component in colostrum that blocks the effects of the inactivated whole virus vaccine in piglets. Results of the study published highlight the point that sow vaccination inhibits vaccine effects in piglets, and may actually increase disease severity.
Technical Abstract: Whole-inactivated virus (WIV) vaccines for influenza A virus (IAV) provide limited cross-protection to diverse antigenic strains that are circulating or may emerge in a population. Maternal vaccination is used to protect neonatal animals from disease through passive transfer of immunity. It is desirable to vaccinate at a young age to induce active immunity that provides protection against infection before maternal immunity wanes; however, maternal-derived immunity (antibody or cells) can interfere with vaccine priming. Previous work indicates that vaccine-associated enhanced respiratory disease (VAERD) occurs in pigs following heterologous IAV challenge if pigs were previously vaccinated with WIV vaccine in the presence of matched maternal-derived immunity (MDI). However, the component of MDI (antibody or cells) that is required for the mispriming of piglet immunity has not been determined. While antibody from colostrum is absorbed into piglet circulation regardless of the sow from which it receives colostrum, transfer of maternal cells requires colostrum from the biological dam. We used cross-fostering (CF) as a tool to determine if maternal cells are required for the mispriming of piglet immunity upon WIV vaccination in presence of MDI. Piglets vaccinated in the presence of maternal derived immunity (MDI), regardless of CF, displayed characteristics of VAERD following heterologous challenge. MDI alone (no piglet vaccination) did not provide cross-protection against the antigenic variant; however, it did not induce VAERD. WIV vaccine provided complete protection against homologous challenge when delivered to piglets without MDI. Vaccination in the presence of MDI inhibited an increase in hemagglutination inhibiting (HI) antibody titers to vaccine antigen, but did not alter development of total immunoglobulin levels to vaccine virus. Taken together, the cellular component of MDI did not contribute to the mispriming of piglet immunity to WIV vaccine, but maternal-derived antibody (MDA) alone was sufficient and future work is aimed at understanding how MDA alters WIV vaccine immunogenicity.