The pivotal role of central memory (cm) CD4 in long term protective immunity has recently been confirmed in a murine model of leishmaniasis (Zaph et al, Nature Medicine 2004). Upon secondary infection, T(cm) cells proliferate in draining lymph nodes before differentiating into tissue-homing effector T cells and mediating protection. Because of their capacity to persist after antigen clearance, T (cm) cells are privileged targets for vaccine development. Here we report on the characterization of CD4+ T(cm) elicited in cattle during contagious bovine pleuropneumonia (CBPP). CFSE and flow cytometric analysis of antigen recall responses in draining lymph nodes of cattle developing chronic CBPP indicated that both CD62L-CD45RO+CD4+ and CD62L+CD45RO+CD4+ T cells proliferate to a similar extent during the first 5 days of stimulation in vitro. However, after 7 days, CD62L+ cells that have proliferated (CFSEdim) represent up to 80% of total CD4 which coincides with a substantial increase in absolute numbers of CD4. IFN-[gamma] secretion (ELISA) was only marginally affected by the enrichment of cultures for CD62L+ CD4. Finally, pathogen-induced IFN-[gamma] synthesis was detected primarily in CD62L-CD4+ T cells as early as day 2 by direct intracellular staining. High CD62L expression and proliferation but low cytokine production in response to Ag are characteristics of T(cm) cells in mice. In summary, the approach described here allows direct characterization of pathogen-derived bovine CD4+T(cm) in uncloned populations. This has direct applications for the development of vaccines inducing long-term protection against CBPP and will also provide better insight into the regulation of CD4+ T(cm) during infection in cattle. (Texte intégral)