Análise da resposta imune à vacina contra o Streptococcus pyogenes em camundongos selecionados para alta e baixa produção de anticorpos

Abstract

Streptococcus pyogenes is a gram-positive group A (GAS) bacteria responsible for causing various clinical manifestations, such as pharyngitis, rheumatic fever (RF) and rheumatic heart disease. Approximately 600 million new cases of pharyngitis and 15 million occurrences of rheumatic heart disease per year are estimated worldwide, while the number of deaths may exceed 500,000 over the same period. Considering the impacts of S. pyogenes infections on people's health, it is necessary to study a vaccine for the prevention of the disease. Several studies with vaccines against Streptococcus infections have been conducted, but there is still no vaccine effective for use in humans. A peptide vaccine, StreptInCor, was developed at the Heart Institute, from the S. pyogenes M5 protein, the major bacterial antigen. This vaccine underwent several in vitro and in vivo tests, showing to be capable of inducing both cellular and humoral responses in isogenic and heterogenic mouse strains, and may be a vaccine candidate against bacterial infections caused by Group A Streptococcus. However, in order to be considered effective, it is important that it exhibits good vaccine coverage in the population, inducing the immune response among individuals with variable antibody production capabilities. Thus, this work searched for the potential of the vaccine candidate, StreptInCor, in stimulating the immune response of selected mice to high and low antibody production. Therefore, the serum antibody titer, the cytokine production and the splenocyte cell proliferation of the immunized animals were analyzed. The cellular response was detected only by the production of IL-5 and IL-2. In accordance with what has already been published, the humoral response is present and increases according to the number of immunizations in both strains. The production of antibodies by the LIII mouse strain suggests that this vaccine should be effective in individuals with a poor immune response, which makes StreptInCor a strong candidate vaccine for the human population.