Confronting the avian influenza threat: vaccine development for a potential pandemic

Abstract

Sporadic human infection with avian influenza viruses has raised concern that reassortment between human and avian subtypes could generate viruses of pandemic potential. Vaccination is the principal means to combat the impact of influenza. During an influenza pandemic the immune status of the population would differ from that which exists during interpandemic periods. An emerging pandemic virus will create a surge in worldwide vaccine demand and new approaches in immunisation strategies may be needed to ensure optimum protection of unprimed individuals when vaccine antigen may be limited. The manufacture of vaccines from pathogenic avian influenza viruses by traditional methods is not feasible for safety reasons as well as technical issues. Strategies adopted to overcome these issues include the use of reverse genetic systems to generate reassortant strains, the use of baculovirus-expressed haemagglutinin or related non-pathogenic avian influenza strains, and the use of adjuvants to enhance immunogenicity. In clinical trials, conventional surface-antigen influenza virus vaccines produced from avian viruses have proved poorly immunogenic in immunologically naive populations. Adjuvanted or whole-virus preparations may improve immunogenicity and allow sparing of antigen.

Adjuvanted H5N1 vaccine induces early CD4+T cell response that predicts long-term persistence of protective antibody levels

“…In recent years the emergence of highly pathogenic H5N1 avian influenza strains, their transmission from poultry to humans, and the increase in global travel have created the potential of a new pandemic and the need to define strategies to limit its spread and mortality (1,2). Lessons from previous influenza pandemics suggest that case isolation and social distance play a critical role in containing the spread of infection (1,3). Mathematical models suggest that a vaccine inducing a protective response in 2 weeks, if given at the start of the outbreak, can reduce clinical cases by 90% (1).…”

T cell epitope engineering: an avian H7N9 influenza vaccine strategy for pandemic preparedness and response

“…Relative to seasonal influenza, vaccination against avian influenza poses a unique challenge because the human population is immunologically naïve. 17 Vaccination cannot rely on preferential recruitment of memory B and T cells to elicit a protective antibody response due to distant sequence relatedness with seasonal influenza. Any cross-reactive memory B and T cells would be present at frequencies too low to confer protective antibody immunity by seasonal vaccination.…”

Gripe aviar: lo que un intensivista debe conocer

“…Estos tres tipos se clasifican en función de las proteínas de su núcleo (NP y M) 34 . La gripe A infecta mamíferos y pájaros mientras que la B y la C se restringen a los seres humanos 36,37 .…”

“…Estos receptores en el intestino permiten una réplica viral continua y separarse junto con la materia fecal producida. Por lo tanto, el ambiente, principalmente los humedales, lagos y ríos, donde es predominante la presencia de patos, gansos y otras aves acuá-ticas, facilita la exposición a las partículas virales 36 . La migración de pájaros salvajes propaga la infección entre las especies de pájaros y la extensión de nuevos tipos de virus a los terrenos de la ingenuidad inmunológica, en donde se produce la infección rápida de pájaros y la manifestación de la enfermedad [51][52][53] .…”

“…Las vacunas existentes corresponden a tres grupos principales: virus entero, productos divididos y antí-genos de superficie 36 . Se obtiene una eficacia protectora del 70-95% en adultos jóvenes sanos cuando hay un buen encuentro antigénico entre la vacuna y las cepas que circulan 97 , una reducción del 19-63% en la hospitalización para la neumonía y la gripe, del 17-39% en todas las condiciones respiratorias y del 27-75% en todas las causas de mortalidad 36 .…”