Vaginal Protection and Immunity after Oral Immunization of Mice with a Novel Vaccine Strain ofListeria monocytogenesExpressing Human Immunodeficiency Virus Type 1gag

Abstract

Natural transmission of human immunodeficiency virus (HIV) occurs at mucosal surfaces. During acute infection, intestinal and other mucosae are preferential sites of virus replication and rapidly become depleted of CD4؉ T cells. Therefore, mucosal immunity may be critical to control both initial infection and the massive early spread of virus. An attenuated D-alanine-requiring strain of the oral intracellular microorganism Listeria monocytogenes expressing HIV type 1 gag was shown to induce protective cell-mediated immunity in mice against viruses that express HIV gag when immunization occurs in the presence of a transient supply of D-alanine. In this study, we examined the efficacy of new attenuated strains that are able to synthesize D-alanine from a heterologous dal gene tightly regulated by an actA-promoted resolvase recombination system. In the absence of D-alanine, Gag-specific cytotoxic T lymphocytes (CTLs) were induced systemically after intravenous immunization, and one strain, Lmdd-gag/pARS, induced strong dose-dependent Gag-specific CTLs after oral immunization. A significant level of Gag-specific CD8 ؉ T cells was induced in the mucosal-associated lymphoid tissues (MALTs). Upon intravaginal challenge of these orally immunized mice with recombinant vaccinia virus (rVV) expressing HIV gag, gamma interferon-and tumor necrosis factor alpha-secreting Gag-specific CD8 ؉ T cells were dramatically increased in the spleen and MALTs. Oral immunization with Lmdd-gag/pARS led to complete protection against vaginal challenge by a homologous clade B gag-expressing rVV. In addition, strong cross-clade protection was seen against clades A and C and partial protection against clade G gag-expressing rVV. These results suggest that Lmdd-gag/pARS may be considered as a novel vaccine candidate for use against HIV/AIDS.

PDL-1 Blockade Impedes T Cell Expansion and Protective Immunity Primed by Attenuated Listeria monocytogenes

“…During infection, Lm primes a robust Ag-specific CD8 and CD4 T cell response, and accordingly Lm infection is a widely used experimental model whereby priming and activation of Ag-specific T cells and the protective effects of these T cells are examined (14). Furthermore, because of the relative ease by which recombinant Lm strains can be generated, as well as the existence of many highly attenuated and immunogenic Lm mutant strains, recombinant Lm expressing protective Ags from other pathogens are being explored as a new class of live attenuated vaccine vectors (15)(16)(17). In this study we examined the effects of PDL-1 blockade on T cell priming and expansion after primary infection with Lm ⌬actA, and of protective immunity following secondary challenge with virulent Lm.…”

Novel Vaccination Protocol with Two Live Mucosal Vectors Elicits Strong Cell-Mediated Immunity in the Vagina and Protects against Vaginal Virus Challenge

“…Most importantly, whereas ivag infection of naive mice led to high accumulations of vaccinia virus in ovaries and oviduct (the favored replication site after ivag infection; Ref. 34), ivag immunized mice were fully protected, allowing little or no virus replication in these tissues (Fig. 7B).…”

“…Lymphocytes from Peyer's patches were prepared by digestion with collagenase D and DNase I at 37°C for 30 min and then incubated in the presence of 5 mM EDTA for 5 min as described (34). The digested tissues were teased into suspension and filtered through nylon mesh to remove debris.…”

An Attenuated Listeria monocytogenes Vector Primes More Potent Simian Immunodeficiency Virus-Specific Mucosal Immunity than DNA Vaccines in Mice

“…The deletion of these genes was partially complemented by introducing the Bacillus subtilis dal gene into the vector, thus retaining attenuation (3). rLm, when administered orally, followed by a booster with a replication-incompetent recombinant adenovirus serotype 5 (rAd5) vector, has been shown to induce robust antigen (Ag)-specific cellular immune responses in systemic and mucosal inductive sites (4,5). However, the elucidation of L. monocytogenes vector-induced cellular immunity in the effector sites of the gastrointestinal mucosa remains unclear, and the vector's potency compared with that of DNA vaccine priming remains to be determined.…”