RESUMO
BACKGROUND: In recent years, promising vaccination strategies against rickettsiosis have been described in experimental animal models and human cells. OmpB is considered an immunodominant antigen that is recognized by T and B cells. The aim of this study was to identify TCD4+INF-γ+ and TCD8+INF-γ+ lymphocytes in an autologous system with macrophages transfected with the vaccine candidate pVAX1-OmpB24. Lymphocytes and monocytes from 14 patients with Rickettsia were isolated from whole blood. Monocytes were differentiated into macrophages and transfected with the plasmid pVAX1-OmpB24 pVax1. Isolated lymphocytes were cultured with transfected macrophages. IFN-γ-producing TCD4+ and TCD8+ lymphocyte subpopulations were identified by flow cytometry, as was the percentage of macrophages expressing CD40+, CD80+, HLA-I and HLA-II. Also, we analyzed the exhausted condition of the T lymphocyte subpopulation by PD1 expression. Macrophages transfected with pVAX1-OmpB24 stimulated TCD4+INF-γ+ cells in healthy subjects and patients infected with R. typhi. Macrophages stimulated TCD8+INF-γ+ cells in healthy subjects and patients infected with R. rickettsii and R. felis. Cells from healthy donors stimulated with OmpB-24 showed a higher percentage of TCD4+PD1+. Cells from patients infected with R. rickettsii had a higher percentage of TCD8+PD-1+, and for those infected with R. typhi the larger number of cells corresponded to TCD4+PD1+. Human macrophages transfected with pVAX1-OmpB24 activated TCD4+IFN-γ+ and CD8+IFN-γ+ in patients infected with different Rickettsia species. However, PD1 expression played an important role in the inhibition of T lymphocytes with R. felis.
RESUMO
RESUMEN Las rickettsiosis son un grupo de enfermedades zoonóticas causadas por bacterias del género Rickettsia, transmitidas por ectoparásitos hematófagos. Debido a su cuadro clínico inespecífico (fiebre, artralgias, mialgias y exantema) es subdiagnosticada y confundida con otras de mayor prevalencia como son el dengue y Chikunguya. Dada su creciente incidencia, se han estudiado antígenos rickettsiales, así como la respuesta inmune que generan con el fin de poder desarrollar vacunas, de ellos los más destacados son las proteínas OmpA y OmpB; en recientes estudios se muestra una respuesta inmune efectiva contra esta enfermedad, por lo que la presente revisión tiene como objetivo brindar un panorama de los resultados obtenidos en estudios enfocados al desarrollo de vacunas a partir de estas proteínas.
ABSTRACT Rickettsioses are a group of zoonotic diseases caused by bacteria of the genus Rickettsia, transmitted by hematophagous ectoparasites. Due to its non-specific clinical characteristics (fever, arthralgia, myalgias and exanthema) is underdiagnosed and confused with others of greater influence such as Dengue, and Chikunguya. In attention to its increasing incidence, rickettsial antigens have been studied along with the immune response they generate, in order to develop vaccines against rickettsiosis, being OmpA and OmpB the most prominent. Recent studies indicate an effective immune response against this disease, so the present review aims to provide an overview of the results obtained in studies focusing in vaccine development using these two proteins.
RESUMO
Background & objectives: The nature of the rickettsial antigens and the immune response generated by them, have been the subject of exhaustive research so that a suitable vaccine can be developed. Till date evaluations of Rickettsia rickettsii antigens that induce both humoral and cellular responses in animal models have only shown partial protection and short-term immunological memory. This study was aimed to evaluate the immune response induced by DNA plasmids generated from the OmpA and OmpB genes of R. rickettsii in peripheral blood mononuclear cells of rickettsial (sensitized) patients compared to healthy subjects. Methods: Plasmids OmpA-49, OmpB-15 and OmpB-24 were generated in the pVAX vector. Macrophages derived from the THP-1 cell line were transfected in vitro with the plasmids and were co-cultured with T-lymphocytes from sensitized subjects and healthy subjects to evaluate cell proliferation and cytokine production. Results: The OmpB-24 plasmid induced proliferative response in human lymphocytes, with production of IL-2, IFN-γ, IL-12p70, IL-6 and TNF-α, likely due to the presence of conserved epitopes among R. rickettsii, R. typhi and R. felis (differing from 1 to 3 amino acids) during the construction of the plasmids. Interpretation & conclusion: DNA sequences of rickettsial epitopes can be cloned into the pVAX vector. Constructed plasmids can generate a proliferative response and produce cytokines in vitro, in co-culture of transfected macrophages with sensitized human lymphocytes. Plasmid OmpB-24 proved to be the most immunogenic with respect to plasmids OmpA-49 and OmpB-15.