Swine Influenza A Vaccines, Pandemic (H1N1) 2009 Virus, and Cross-Reactivity

DOI: 10.3201/eid1606.100138
Suggested citation for this article: Dürrwald R, Krumbholz A, Baumgarte S, Schlegel M, Vahlenkamp TW, Selbitz H-J, et al. Swine influenza A vaccines, pandemic (H1N1) 2009 virus, and cross-reactivity [letter]. Emerg Infect Dis. 2010 Jun; [Epub ahead of print]

Swine Influenza A Vaccines, Pandemic (H1N1) 2009 Virus, and Cross-Reactivity

To the Editor: Since its first emergence in the human population in spring 2009 (1–3) infections with pandemic (H1N1) 2009 virus have been reported in pigs, turkeys, and some carnivore species (4,5). The pandemic (H1N1) 2009 virus can be experimentally transmitted between pigs (6). The reported transmissibility of the virus raises the question as to whether authorized swine influenza vaccine strains may be cross-reactive to pandemic (H1N1) 2009 virus. Kyriakis et al. (7) investigated the cross-reactivity of 66 pig serum samples from different infection and vaccination trials and reported cross-reactions between the avian-like H1N1 viruses circulating in the European pig population (avH1N1) and the classical swine H1N1 viruses (cH1N1) with pandemic (H1N1) 2009 virus by hemagglutination inhibition assay.

To investigate this cross-reactivity in more detail, a neutralization test was applied in the study we report here. A serial dilution of serum samples was prepared (log4). All virus strains were adjusted to 100 fifty-percent tissue culture infectious doses. This working dilution of virus was mixed with serum dilutions and incubated 1 hour at 37°C. Madin-Darby bovine kidney monolayers were infected with the neutralization mixtures. After 48 hours of incubation, cells were fixed with acetone (4°C–8°C) and investigated by indirect immunofluorescent assay. Finally, the 50% neutralization titer was calculated.

Hyperimmune serum samples were established by using a 4-fold vaccination of pigs with antigens of H1N1 vaccine strains (A/New Jersey/8/1976, A/sw/Netherlands/25/1980, A/sw/IDT/Re230/1992, A/sw/Haselünne/IDT2617/2003), and a strain of pandemic (H1N1) 2009 virus (A/Hamburg/7/2009) by using Freund adjuvant. Blood samples were taken 14 days after last immunization. A vaccine containing the pandemic (H1N1) 2009 virus was produced. Swine influenza vaccines available in central Europe and the newly produced vaccine containing...

open here to see the full-text:
http://www.cdc.gov/eid/content/16/6/pdfs/10-0138.pdf