Overexpression of Interleukin-7 Extends the Humoral Immune Response Induced by Rabies Vaccination.

Rabies continues to present a public health threat in most countries of the world. The most efficient way to prevent and control rabies is to implement vaccination programs for domestic animals. However, traditional inactivated vaccines used in animals are costly and have relatively low efficiency, which impedes their extensive use in developing countries. There is, therefore, an urgent need to develop single-dose and long-lasting rabies vaccines. However, little information is available regarding the mechanisms underlying immunological memory, which can broaden humoral responses following rabies vaccination. In this study, a recombinant rabies virus (RABV) that expressed murine interleukin-7 (IL-7), referred to here as rLBNSE-IL-7, was constructed, and its effectiveness was evaluated in a mouse model. rLBNSE-IL-7 induced higher rates of T follicular helper (Tfh) cells and germinal center (GC) B cells from draining lymph nodes (LNs) than the parent virus rLBNSE. Interestingly, rLBNSE-IL-7 improved the percentages of long-lived memory B cells (Bmem) in the draining LNs and plasma cells (PCs) in the bone marrow (BM) for up to 360 days postimmunization (dpi). As a result of the presence of the long-lived PCs, it also generated prolonged virus-neutralizing antibodies (VNAs), resulting in better protection against a lethal challenge than that seen with rLBNSE. Moreover, consistent with the increased numbers of Bmem and PCs after a boost with rLBNSE, rLBNSE-IL-7-immunized mice promptly produced a more potent secondary anti-RABV neutralizing antibody response than rLBNSE-immunized mice. Overall, our data suggest that overexpressing IL-7 improved the induction of long-lasting primary and secondary antibody responses post-RABV immunization.