MAIT cell clonal expansion and TCR repertoire shaping in human volunteers challenged with Salmonella Paratyphi A.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can detect bacteria-derived metabolites presented on MR1. Here we show, using a controlled infection of humans with live Salmonella enterica serovar Paratyphi A, that MAIT cells are activated during infection, an effect maintained even after antibiotic treatment. At the peak of infection MAIT cell T-cell receptor (TCR)ß clonotypes that are over-represented prior to infection transiently contract. Select MAIT cell TCRß clonotypes that expand after infection have stronger TCR-dependent activation than do contracted clonotypes. Our results demonstrate that host exposure to antigen may drive clonal expansion of MAIT cells with increased functional avidity, suggesting a role for specific vaccination strategies to increase the frequency and potency of MAIT cells to optimize effector function.

Small bowel in typhoid fever.

Twenty-eight patients with typhoid fever and one patient with paratyphoid fever were subjected to intestinal function tests (faecal fat and D-xylose) and jejunal biopsy soon after recovery from the acute phase of the disease in order to assess the residual functional and morphological status of the small bowel. The results indicate that almost 50% (14/29) initially had defective D-xylose absorption which recovered rapidly. No patient had steatorrhoea. Jejunal biopsies of eight patients out of 22 showed increased chronic cell infiltration; there was, however, no specific lesion. It appears that intestinal injury following salmonellosis results only in mild functional derangement of the bowel which recovers rapidly.