title: CD4+ T cells mediate antibody-independent acquired immunity to pneumococcal colonization.
abstract: Acquired immunity to Streptococcus pneumoniae (pneumococcus) has long been assumed to depend on the presence of anticapsular antibodies. We found, however, that colonization with live pneumococci of serotypes 6B, 7F, or 14 protected mice against recolonization by any of the serotypes and that protection from acquisition of a heterologous or homologous strain did not depend on anticapsular antibody. Further, intranasal immunization by live pneumococcal colonization or by a killed, nonencapsulated whole-cell vaccine protected antibody-deficient mice against colonization, suggesting independence of antibodies to any pneumococcal antigens. Protection by intranasal immunization with whole-cell vaccine was completely abrogated in T cell-deficient mice, and in mice that were congenitally deficient in CD4(+) T cells or depleted of these cells at the time of challenge. In contrast, mice congenitally deficient in, or depleted of, CD8(+) T cells were fully protected. Protection in this model was observed beyond 2 months after immunization, arguing against innate or nonspecific immune mechanisms. Thus, we find that immunity to pneumococcal colonization can be induced in the absence of antibody, independent of the capsular type, and this protection requires the presence of CD4(+) T cells at the time of challenge.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA. richard.malley@childrens.harvard.edu
authors.forename: Richard
authors.initials: R
authors.lastname: Malley
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Trzcinski
authors.forename: Amit
authors.initials: A
authors.lastname: Srivastava
authors.forename: Claudette M
authors.initials: CM
authors.lastname: Thompson
authors.forename: Porter W
authors.initials: PW
authors.lastname: Anderson
authors.forename: Marc
authors.initials: M
authors.lastname: Lipsitch
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007111:Immunity, Cellular; D051379:Mice; D008810:Mice, Inbred C57BL; D011008:Pneumococcal Infections / Q000517:prevention & control*; D013045:Species Specificity; D022541:Streptococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*; D013997:Time Factors
chemical_list: D022541:Streptococcal Vaccines