Efficacy of vaccination of pigs with different H1N1 swine influenza viruses using a recent challenge strain and different parameters of protection.
This study investigates whether antigenic evolution within H1N1 swine influenza viruses can compromise vaccine efficacy and, specifically, whether the A/New Jersey/8/76 strain in the commercial swine influenza vaccines needs to be updated. Pigs were vaccinated twice intramuscularly with experimental monovalent vaccines derived from different H1N1 strains (A/New Jersey/8/76, Sw/Belgium/1/83 or Sw/Belgium/1/98) or with a commercial bivalent vaccine based on A/New Jersey/8/76 (H1N1) and A/Port Chalmers/1/73 (H3N2). Experimental and commercial vaccines contained a different adjuvant. Two weeks after the second vaccination, all pigs were challenged intratracheally with Sw/Belgium/1/98. Mean pre-challenge haemagglutination inhibition (HI) antibody titres against the challenge virus were lower for the experimental A/New Jersey/8/76 vaccine than for the other vaccines. The reduction in mean virus titres in the lungs was highly significant for the latter vaccines, including the commercial New Jersey-derived vaccine, but not for the experimental A/New Jersey/8/76 vaccine. Clinical signs after challenge were negligible in all vaccinates. Post-challenge levels of interferon-alpha and tumor necrosis factor-alpha in bronchoalveolar lavage fluids were reduced in the vaccinates, while levels of interleukin-1 and neutrophils were less consistent. Though the A/New Jersey/8/76 strain is less effective in preventing infection by Sw/Belgium/1/98 than the homologous virus or than Sw/Belgium/1/83, all strains can protect completely if antibody titres against the challenge virus are sufficiently high. Apart from the vaccine strain, adjuvant and antigenic dose may play a crucial role in vaccine efficacy.
Van Reeth
K
K
Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium. kristien.vanreeth@rug.ac.be
Labarque
G
G
De Clercq
S
S
Pensaert
M
M
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D007115:Immunization Schedule; D007249:Inflammation / Q000517:prevention & control / Q000662:veterinary; D053118:Influenza A Virus, H1N1 Subtype; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007273:Injections, Intramuscular; D007442:Intubation, Intratracheal; D008168:Lung / Q000473:pathology; D009976:Orthomyxoviridae Infections / Q000276:immunology / Q000517:prevention & control* / Q000662:veterinary*; D013552:Swine; D013553:Swine Diseases / Q000276:immunology / Q000517:prevention & control*; D014611:Vaccination / Q000662:veterinary
D000914:Antibodies, Viral; D007252:Influenza Vaccines