Resumo

Meningococcal infection evokes persistent immune protection against the disease in individuals with normal immune system. In contrast, protection induced by meningococcal vaccines always requires booster injections of vaccine. Vaccination against disease aims at the induction of long-lasting cellular and humoral immune responses. Few studies have addressed the mechanisms by which meningococcal vaccines generate and sustain immunological memory. In Brazil, Neisseria meningitidis serogroup C (MenC) and serogroup B (MenB) have been the main cause of the disease during the last years. The goal of this study was to investigate the bactericidal antibody response and cellular immunity to Neisseria meningitidis after infection. Blood samples were obtained from 13 convalescent patients suffering of meningococcal disease (MD) from Instituto Estadual de Infectologia São Sebastião. The specificity of bactericidal antibodies was investigated using strains N79/96 (C:2b:P1.10), Cu385 (4,7:P1.19,15) and N753/00 (C:23:P1.14-6). For activation of memory T cells, peripheral blood mononuclear cells were stimulated with outer membrane vesicles (OMVs) from strains N79/96 (C:2b:P1.10), H355 (4,7:P1.19,15) and a mutant strain derived from H355 which does not express the porin PorA. OMVs were used at 50 μg/ml and the positive control, PHA (Sigma), at 10 μg/ml. The negative control consisted of un-stimulated cells. The reaction was incubated for 3 h at 37 °C in 5% CO2 atmosphere. Cells were stained for a panel of cell surface markers including fluorescein isothiocyanate (FITC)-conjugated CD4; phycoerythrin (PE)-conjugated CCR7; PerCP-conjugated CD69; and APC-conjugated CD45RA (all from BD Biosciences Pharmingen, San Diego, CA). The results showed that 38.5%, 46% and 31% of convalescent individuals had bactericidal antibody titers > 4 against strains N79/96, N753/00 and Cu385, respectively. Laboratorial diagnosis of MD were done by latex agglutination (46% of cases), culture (7.7%), Gram-staining of liquor (31%) or PCR (15%). We found a similar distribution (~50%) of T central memory cells (TCM: CD4+CD45RA-CCR7+) and T effector memory cells (TEM: CD4+CD45RA-CCR7-) in peripheral blood samples of patients. However, after antigenic stimulation with OMVs-MenC, a higher proportion (18,9%) of TCM was activated (CD69+) compared with TEM (8,49%). Reactivity of memory T cells after stimulation with OMVs-MenB had a similar pattern as stimulation with OMVs-MenC. A higher proportion of TCM (14,4%) was activated (CD69+) compared with TEM (7,2%). Therefore, this study suggests that meningococcal disease induced a heterogeneous T cell and bactericidal antibody responses.