Efficacy of commercial swine influenza vaccines against challenge with a recent European H1N1 field isolate

• Published in: Veterinary microbiology 2010-07, Vol.144 (1), p.67-74
• Main Authors: Kyriakis, C.S., Gramer, M.R., Barbé, F., Van Doorsselaere, J., Van Reeth, K.
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Animals; Antibodies, Viral - immunology; Antigenic drift; antigenic variation; Applied microbiology; Biological and medical sciences; disease prevention; Efficacy; Emulsions; Europe - epidemiology; Fundamental and applied biological sciences. Psychology; genetic variation; H1N1 swine influenza virus; hemagglutination inhibition test; Hemagglutination Inhibition Tests - veterinary; hemagglutinins; Hemagglutinins, Viral - genetics; Hemagglutinins, Viral - immunology; immune response; immunity; immunogenetics; Influenza A virus; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - immunology; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza Vaccines - therapeutic use; microbial genetics; Microbiology; Miscellaneous; Orthomyxoviridae Infections - epidemiology; Orthomyxoviridae Infections - immunology; pathogenicity; pathotypes; Pigs; protective effect; serotypes; Swine; swine diseases; Swine Diseases - immunology; Swine Diseases - virology; vaccination; Vaccines; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Vaccines, Inactivated - therapeutic use; Virology
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2009.12.039

This study examines the immunogenicity and efficacy of four commercial swine influenza (SI) vaccines against challenge with a recent European H1N1 virus, Sw/Gent/112/07. The vaccines contained different H1N1 strains showing between 77% and 95% genetic homology with the haemagglutinin (HA) of the challenge virus. Four groups of 10 pigs each received a double vaccination, with a 4-week interval, with one of the vaccines; a fifth group served as unvaccinated controls. All pigs were challenged 3 weeks after the second vaccination intratracheally with 10 5.0 EID 50 of Sw/Gent/112/07. Sera were examined in haemagglutination inhibition (HI) tests against the homologous vaccine H1N1 strains, the challenge virus and a panel of five recent H1N1 isolates. Pigs were euthanized at 24 or 72 h post-challenge and virus titres were determined in right and left lung halves. Two vaccines, in which the H1N1 strains showed a genetic homology of 93% and 89% to Sw/Gent/112/07, significantly reduced virus replication. The vaccine containing an H1N1 strain with 95% homology to Sw/Gent/112/07, did not offer significant protection, neither did it induce the highest HI titres. In general, pigs with HI antibody titres ≥20 against Sw/Gent/112/07 were virologically protected against challenge. HI titres against other viruses, however, differed compared to the challenge virus and between viruses. Our data clearly show that the genetic homology with the challenge virus is not the ultimate predictor for SI vaccine performance. The true reason for the differences in vaccine potency remains obscure because other factors, such as the antigen dose and/or the adjuvant, also differed between the vaccines.