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Flynn Webinar: What immune cells play a role in protection against M.tb re-infection?

Approximately a quarter of the global population is estimated to have Mycobacterium tuberculosis infection (tuberculosis etiological agent). However, only 5-10% of infected individuals progress to disease. On the 8th of March, the IUIS-Immunopaedia-Frontiers webinar series featured a talk by tuberculosis immunologist Dr. JoAnne Flynn. In honour of World TB  Day on the 24th of March, we shall provide three summaries highlighting findings shared during Dr Flynn’s talk.

Adapted from Cadena et al., 2018

In this summary, we shall highlight research she presented that provided evidence for the role of CD4 T cells in protection against M.tb reinfection. Previous findings by Dr Flynn and collaborators demonstrated that prior M.tb infection is associated with protection against M.tb reinfection (Cadena et al., 2018). This study showed that non-human primates  (NHPs) that were re-infected had a significantly lower M.tb bacterial burden and a significantly higher proportion of sterile granulomas compared to M.tb infected naïve NHPs. Further, they showed that adaptive Th1 immune responses were not different between M.tb reinfected and naïve (primary M.tb infected) NHPs. As a follow-up to this study, Dr Flynn’s research group aimed to determine if CD4 T cells are necessary for protection against reinfection. They focused on CD4 T cells because they are important for the control of TB, and depletion results in worse acute infection and latent TB reactivation in NHPs.

In this summary, we shall highlight research she presented that provided evidence for the role of CD4 T cells in protection against M.tb reinfection. Previous findings by Dr Flynn and collaborators demonstrated that prior M.tb infection is associated with protection against M.tb reinfection (Cadena et al., 2018). This study showed that non-human primates  (NHPs) that were re-infected had a significantly lower M.tb bacterial burden and a significantly higher proportion of sterile granulomas compared to M.tb infected naïve NHPs. Further, they showed that adaptive Th1 immune responses were not different between M.tb reinfected and naïve (primary M.tb infected) NHPs. As a follow-up to this study, Dr Flynn’s research group aimed to determine if CD4 T cells are necessary for protection against reinfection. They focused on CD4 T cells because they are important for the control of TB, and depletion results in worse acute infection and latent TB reactivation in NHPs.

In summary, results presented in the webinar suggest that CD4 T cells play an important role in protection against re-infection. This protective effect is not restricted to CD4 T cells function but is associated with the induction and maintenance of CD8 T cells that produce granzyme H and K.

Summary by Cheleka AM Mpande