Neonatal immunization with Listeria monocytogenes induces T cells with an adult-like avidity, sensitivity, and TCR-Vβ repertoire, and does not adversely impact the response to boosting

Listeria monocytogenes (Lm) holds promise as a neonatal vaccine vehicle. Here we show that Lm immunized neonatal mice reached maximal Ag-specific CD8+ T cell expansion after only a single immunization, while adults required two doses. Ag-specific CD4+ T cell expansion in both age groups required a boost to reach its peak. Neither functional avidity, sensitivity, nor the TCR-Vβ repertoire of the Ag-specific T cells differed between mice immunized as neonates or adults. Lastly, neonatal immunization did not decrease protection or preclude a booster response. Overall, our data provide further evidence in support of immunization at birth as a feasible public health strategy to combat early life infections.