Effect of passive immunization on immunogenicity and protective efficacy of vaccination against a Mexican low‐pathogenic avian H5N2 influenza virus
Heather L. Forrest1 
Alejandro Garcia2 
Angela Danner1 
Jon P. Seiler1 
Kimberly Friedman1 
Robert G. Webster1 
[1] Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN, USA;Laboratorios Avilab, Loma Morad 7652 Col. Lomas del Manantial, Tonala, Jalisco, Mexico
Despite the use of vaccines, low-pathogenic (LP) H5N2 influenza viruses have continued to circulate and evolve in chickens in Mexico since 1993, giving rise to multiple genetic variants. Antigenic drift is partially responsible for the failure to control H5N2 influenza by vaccination; the contribution of maternal antibodies to this problem has received less attention.
Methods
We investigated the effect of different antisera on the efficacy of vaccination and whether booster doses of vaccine can impact immune suppression.
Results
While single doses of inactivated oil emulsion vaccine to currently circulating H5N2 influenza viruses provide partial protection from homologous challenge, chickens that receive high-titer homologous antisera intraperitoneally before vaccination showed effects ranging from added protection to immunosuppression. Post-infection antisera were less immunosuppressive than antisera obtained from field-vaccinated chickens. Homologous, post-infection chicken antisera provided initial protection from virus challenge, but reduced the induction of detectable antibody responses. Homologous antisera from field-vaccinated chickens were markedly immunosuppressive, annulling the efficacy of the vaccine and leaving the chickens as susceptible to infection as non-vaccinated birds. Booster doses of vaccine reduced the immunosuppressive effects of the administered sera.
Conclusion
Vaccine efficacy against LP H5N2 in Mexico can be severely reduced by maternal antibodies. Source-dependent antisera effects offer the possibility of further elucidation of the immunosuppressive components involved.