Typically, T cells of the immune system respond to a specific feature (antigen) of a microbe, thereby generating protective immunity. As reported in the journal Immunity, an international team of scientists have discovered an exception to this rule. Namely, a group of divergent bacterial pathogens, including pneumococci, all share a small highly conserved protein sequence, which is both presented and recognized by human T cells in a conserved population-wide manner.
The study set out to understand immune mechanisms that protect against pneumococcus, a bacterial pathobiont that can reside harmlessly in the upper respiratory mucosae but can also cause infectious disease, especially in infants and older adults, which can range from middle ear and sinus infections to pneumococcal pneumonia and invasive bloodstream infections.
Most currently used pneumococcal polysaccharide-based conjugate vaccines (PCVs) are effective against 10–13 serotypes, but growing serotype replacement becomes a problem.