Human rotavirus specific T cells: Quantification by ELISPOT and expression of homing receptors on CD4⁺ T cells

Using an intracellular cytokine assay, we recently showed that the frequencies of rotavirus (RV)-specific CD4⁺ and CD8⁺ T cells secreting INFγ, circulating in RV infected and healthy adults, are very low compared to the frequencies of circulating cytomegalovirus (CMV) reactive T cells in comparable individuals. In children with acute RV infection, these T cells were barely or not detectable. In the present study, an ELISPOT assay enabled detection of circulating RV-specific INFγ-secreting cells in children with RV diarrhea but not in children with non-RV diarrhea without evidence of a previous RV infection. Using microbead-enriched CD4⁺ and CD8⁺ T cell subsets, IFNγ-secreting RV-specific CD8 ⁺ but not CD4⁺ T cells were detected in recently infected children. Using the same approach, both CD4⁺ and CD8⁺ RV-specific T cells were detected in healthy adults. Furthermore, stimulation of purified subsets of PBMC that express lymphocyte homing receptors demonstrated that RV-specific INFγ-secreting CD4⁺ T cells from adult volunteers preferentially express the intestinal homing receptor α4β7, but not the peripheral lymph node homing receptor L-selectin. In contrast, CMV-specific INFγ-secreting CD4⁺ T cells preferentially express L-selectin but not α4β7. These results suggest that the expression of homing receptors on virus-specific T cells depends on the organ where these cells were originally stimulated and that their capacity to secrete INFγ is independent of the expression of these homing receptors.