Whether mucosal immunization is required for optimal protective CD8 T cell memory at mucosal surfaces is controversial. In this study, using an adoptive transfer system, we compare the efficacy of two routes of acute lymphocytic choriomeningitis viral infection on the generation, maintenance, and localization of Ag-specific CD8 T cells in tissues, including the vaginal mucosa. Surprisingly, at day 8, i.p. infection results in higher numbers of Ag-specific CD8 T cells in the vaginal mucosa and iliac lymph node, as well as 2–3× more Ag-specific CD8 T cells that coexpress both IFN-γ and TNF-α in comparison to the intranasal route of infection. Expression of the integrin/activation marker CD103 (αEβ7) is low on vaginal mucosal Ag-specific CD8 T cells in comparison to gut mucosal intraepithelial lymphocytes. At memory, no differences are evident in the number, cytokine production, or protective function of Ag-specific CD8 T cells in the vaginal mucosa comparing the two routes of infection. However, differences persist in the cytokine profile of genital tract vs peripheral Ag-specific CD8 T cells. So although the initial route of infection, as well as tissue microenvironment, appear to influence both the magnitude and quality of the effector CD8 T cell response, both systemic and mucosal infection are equally effective in the differentiation of protective memory CD8 T cell responses against vaginal pathogenic challenge.

Immunoglobulins in secretions play a critical role in protection at mucosal surfaces. We examined the generation of viral-specific IgG and IgA in plasma and mucosal secretions of mice following systemic or mucosal immunization with lymphocytic choriomeningitis virus (LCMV), a widely used experimental model of viral infection. While there are early differences in humoral responses depending on the route of viral entry, we show that both routes generate comparably robust viral-specific IgG in plasma, vaginal, lung, and nasal secretions of immune mice. In contrast, LCMV elicited poor viral-specific IgA responses. Mice that were infected IN showed elevated viral-specific IgA in nasal and lung washes compared to IP-infected mice; however, LCMV-specific IgG overwhelmingly contributed to the humoral response in all mucosal secretions examined. Thus similarly to HIV-1, and several other mucosally-encountered microbial infections, these data suggest that LCMV infection fails to induce vigorous viral-specific IgA responses.

In this study we compared the efficacy of two different routes of viral infection on the generation, maintenance, and localization of antigen specific CD8T cells in lymphoid, non-lymphoid, and mucosal tissues during peak effector and memory phases of an immune response. We used an adoptive transfer system of naïve transgenic CD8 T cells, followed by intra-peritoneal (i.p) or intra-nasal (i.n) LCMV infection. Surprisingly, on day 8 the peak of the primary response, i.p. infection resulted in higher numbers of antigen-specific CD8T cells in the vaginal mucosa and ILN only, in addition to 2–3x more antigen specific CD8 T cells that co-expressed both IFNγ and TNFα, when compared to the i.n. route of infection. During memory, equivalent numbers of antigen specific CD8T cells were detected at all sites, irrespective of the route of infection. Following intravaginal re-challenge, both i.p. and i.n generated memory CD8 T cells showed robust secondary responses in the vaginal tract, however the i.n. memory CD8 T cell response was consistently greater. These data suggest that both systemic and mucosal routes of infection can generate a similar quantity of memory CD8 T cells in mucosal sites. However, the initial route of infection appears to influence the programming of the memory CD8T cells generated, and these early differences in priming may impact the quality of protective secondary responses.