title: Comparative study of lymphocytes from individuals that were vaccinated and unvaccinated against the pandemic 2009-2011 H1N1 influenza virus in Southern Brazil.
abstract: BACKGROUND
  While no single factor is sufficient to guarantee the success of influenza vaccine programs, knowledge of the levels of immunity in local populations is critical. Here, we analyzed influenza immunity in a population from Southern Brazil, a region with weather conditions that are distinct from those in the rest of country, where influenza infections are endemic, and where greater than 50% of the population is vaccinated annually.
  
  
  METHODS
  Peripheral blood mononuclear cells were isolated from 40 individuals. Of these, 20 had received the H1N1 vaccine, while the remaining 20 were unvaccinated against the disease. Cells were stimulated in vitro with the trivalent post-pandemic influenza vaccine or with conserved major histocompatibility complex I (MHC I) peptides derived from hemagglutinin and neuraminidase. Cell viability was then analyzed by [3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide)]-based colorimetric assay (MTT), and culture supernatants were assayed for helper T type 1 (Th1) and Th2-specific cytokine levels.
  
  
  RESULTS
  Peripheral blood lymphocytes from vaccinated, but not unvaccinated, individuals exhibited significant proliferation in vitro in the presence of a cognate influenza antigen. After culturing with vaccine antigens, cells from vaccinated individuals produced similar levels of interleukin (IL)-10 and interferon (IFN)-γ, while those from unvaccinated individuals produced higher levels of IFN-γ than of IL-10.
  
  
  CONCLUSIONS
  Our data indicate that peripheral blood lymphocytes from vaccinated individuals are stimulated upon encountering a cognate antigen, but did not support the hypothesis that cross-reactive responses related to previous infections can ameliorate the immune response. Moreover, monitoring IL-10 production in vaccinated individuals could comprise a valuable tool for predicting disease evolution.
authors.affiliation: Laboratório de Biologia Molecular e Cultivo Celular, Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: Deise Nascimento de
authors.initials: DN
authors.lastname: Freitas
authors.affiliation: Laboratório de Biologia Molecular e Cultivo Celular, Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: Henrique Ataíde
authors.initials: HA
authors.lastname: Isaía
authors.affiliation: Laboratório de Microbiologia Molecular, Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, Rio Grande do Sul, Brazil.
authors.forename: Andréia
authors.initials: A
authors.lastname: Henzel
authors.affiliation: Laboratório de Biologia Molecular e Cultivo Celular, Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: Eder
authors.initials: E
authors.lastname: Simão
authors.affiliation: Laboratório de Biologia Molecular e Cultivo Celular, Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: Rodrigo Benedetti
authors.initials: RB
authors.lastname: Gassen
authors.affiliation: Laboratório de Biologia Molecular e Cultivo Celular, Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil.
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Rodrigues Junior
mesh_terms: D000328:Adult; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology*; D001938:Brazil / Q000453:epidemiology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D003430:Cross-Sectional Studies; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control; D007371:Interferon-gamma / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology*; D058873:Pandemics; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D016753:Interleukin-10; D007371:Interferon-gamma