At 14 days post-boosting, MenB-TCM frequencies (mean of 65%) were higher (P < 0.05) than MenB-TEM frequencies (mean of 35%). By 28 days after boosting MenB-TCM frequency (mean of 59%) decreased to levels not significantly different from the ones detected before booster (mean of 57% from selleck screening library days 0 to 14) but remained higher (P < 0.05) than MenB-TEM frequency (mean of 41%). Similar changes were observed for MenB-TEM frequencies at day 28 (mean of 41%) which returned to levels statistically similar to pre-boosting (mean of 51%) ( Fig. 4B). Therefore, these data indicated that in contrast to the early primary T-cell response, the 14 day-recall response to

vaccination was marked by a predominance of TCM. This difference may be attributed to the fact that the analysis of T-cell frequency after the primary series was restricted to a period of 3 days. By day 28, post-boosting T memory-cells returned to homeostatic levels. In agreement with the significant increase of FG-4592 nmr MenB-TCM frequency at 14 days after booster immunisation, these cells reached a maximal (P < 0.05) frequency of activation by day 14 after booster (mean of 26%) as determined by the expression of CD69 ( Fig. 5C). From days 3 to 14 after boosting frequencies of activated MenB-TCM (13–26%) were significantly higher than activated MenB-TEM frequencies (5.8–9.2%) ( Fig. 5C and D). MenB-TEM reached its maximal expression of CD69 at day 28 (mean of

14.6%, P < 0.05 compared to day 14 but not to day 0) after boosting but were still lower in Florfenicol frequency than the TCM/CD69+ (mean of 22.8%) at the same time point. No significant differences were seen in activation status of specific TCM and TEM after primary immunisation (Fig. 5A and B), although a discrete increase of TCM/CD69+

was detected after the third dose (mean of 4.1%) of vaccine when compared with 1 dose (mean of 2.3%) or before vaccination (mean of 1.3%) (Fig. 5A). Fig. 5B shows that about 1.7% of TEM cells were activated before or after immunisation. In conclusion, vaccination with the Cuban MenB vaccine induced a significant memory CD4+ T-cell population that was activated by the booster immunisation. As expected for an efficient recall response, TCM was readily activated after stimulation with specific antigen. The design of optimal strategies to improve MenB vaccine efficiency is an ongoing challenge [4] and [17]. We reported here that the porin PorA, the serosubtype protein of meningococci, had a prominent role in inducing bactericidal as well as opsonic antibodies after immunisation of volunteers with the VA-MENGOC-BC® vaccine. Similarly, previous studies have demonstrated the potential of PorA, especially loops 1 and 4, for evoke bactericidal antibodies [18] and [19]. In contrast, opsonic antibodies have been shown to be directed mainly to PorB proteins [20] and [21]. Maintenance of long-term antibody responses is critical for protective immunity against N. meningitidis.