Hypoxic response protein 1 as a potential immunogenic antigen against tuberculosis infection

MARÍA PAULA MORELLI; NICOLÁS O. AMIANO; DELFINA PEÑA; NANCY TATEOSIAN; JOAQUIN M. PELLEGRINI; AGUSTÍN ROLANDELLI; LORENA CIALLELLA; GRACIELA DE CASADO; DOMINGO J. PALMERO; VERONICA GARCIA

Simposio; Tuberculosis: Science Aimed at Ending the Epidemic; 2020

Keystone Symposia

Hypoxic response protein 1 or Rv2626c, a protein encoded at the Dormancy Survival Regulator (DosR) regulon of Mycobacterium tuberculosis, is overexpressed in hypoxia. In this work, by using different experimental approaches, we analyzed the potential immunogenicity of Rv2626c to be used as a possible vaccine candidate. We initially analyzed whether polyfunctional responses against Rv262c protein might be generated. Therefore, peripheral blood mononuclear cells from latently Mtb infected (LTBI) individuals, tuberculosis patients (TBP), and healthy donors (HD) were cultured with Rv2626c and the expression of IFNγ, IL-2, and TNF were analyzed by flow cytometry. Our results showed a significantly higher frequency of CD4+IFNγ+TNF+IL-2+ cells induced in LTBI subjects as compared to TBP and HD. Next, we searched for the immunodominant regions of Rv2626c to which only LTBI individuals responded. For this, we employed overlapping peptides arranged in six pools (A-F) composed of six peptides each, covering the entire Rv2626c protein. We found that the pools B, D and F induced the highest IFNγ levels, allowing to discriminate LTBI subjects from HD and TBP. In addition to our studies in humans and considering the relevance of multistage vaccines against tuberculosis, we initiated in vivo experiments in BALB/c mice. Animals were administered with three doses (separated by two weeks) of Rv2626c protein plus Ag85Aprotein and IL-12 DNA as an adjuvant. After 10 days of the last priming dose, strong IgG levels against both proteins were measured in sera from immunized mice. Moreover, when splenocytes from vaccinated mice were stimulated ex vivo with Rv2626c, Ag85A, or both antigens, a significantly increased secretion of IFNγ by cells from mice that had received IL-12 DNA was observed. Furthermore, Rv2626c peptide pools also elicited IFNγ production from ex vivo stimulated splenocytes of immunized mice. Surprisingly, similar immunodominant regions of Rv2626c protein were identified in both humans and mice. Thus, our findings indicate that the murine model might be useful in the development of new therapeutic or prophylactic tuberculosis vaccines including hypoxic response protein 1.