Pesquisa de anticorpos anti-PBP2a em pacientes colonizados por Staphylococcus Aureus resistente ?? meticilina (MRSA)

Abstract

As infec????es causadas por Staphylococcus aureusresistentes ?? meticilina (MRSA) s??o temidas em virtude da dificuldade de seu tratamentoe da elevada morbidade associada. A PBP2a (penicillin binding protein 2a), enzima respons??vel pela s??ntese da parede celular em MRSA, apresenta baix??ssima afinidade porbeta-lact??micos. Pelo fato de a PBP2a estar localizada na superf??cie externa, a mesma seria acess??vel ao sistema imune. Durante as infec????es causadas por MRSA, pouco se sabe se o hospedeiro infectado ou colonizado desenvolve anticorpos anti-PBP2a e se osmesmos seriam protetores ou n??o. O presente projeto tem por finalidade avaliar a presen??a e n??veis de anticorpos anti-PBP2a em um grupo de 56 pacientes colonizados por MRSA e investigar se estes anticorpos seriam protetores ou n??o. Os resultados gerados permitiram observar que 71% das amostras analisadas apresentaram anticorposanti-PBP2a pelo teste ELISA. Estas amostras foram submetidas ?? Western blot paraconfirma????o, demonstrando que 46% das amostras possu??ram anticorpos anti-PBP2a. Ap??s estes resultados, as amostras positivas foram submetidas ?? purifica????o para avaliar a cin??tica de crescimento de MRSA. Foi observado que houve ligeira redu????o do crescimento bacteriano entre amostras de soro com anticorpos MRSA comparadas comas de soro com anticorpos anti-MSSA (PBP2a negativos). Por conseguinte avaliamos a curva de crescimento de MRSA em presen??a de imunoglobulinas purificadas de soro de pacientes colonizados por MRSA, (quantifica????o bacteriana). Observamos que houve uma redu????o dr??stica do crescimento bacteriano em presen??a destas imunoglobulinas. Os resultados obtidos indicaram que: (i) pacientes colonizados por MRSA podem produzir anticorpos anti-PBP2a e (ii) estes anticorpos podem conferir prote????o contra MRSA. Estes dados parecem indicar que uma potencial vacina anti-PBP2apoderia ser efetiva para preven????o de infec????es causadas por MRSA, como tamb??m para o emprego de imunoterapia passiva para o tratamento de pacientesinfectados por este pat??geno.Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are feared because of the difficulty of their treatment and the high associated morbidity. The PBP2a (penicillin binding protein 2a), the enzyme responsible for cell wall synthesis in MRSA, presents low affinity for beta-lactams. Because of the PBP2a is located on the external surface, it would be accessible to the immune system. During the MRSA infections, little is known whether the infected orcolonized host can produce antibodies anti-PBP2a and whether these antibodies would be protective or not. This project aims to assess the presence and levels of anti-PBP2a in a group of 56 patients colonized by MRSA and investigate whether these antibodies wouldbe protective or not. The results showed that 71% of the samples presented anti-PBP2aantibodies in ELISA. These samples which were subjected to Western blot for confirmation, it was demonstrated that 46% of the samples presented antibodies anti-PBP2a. After these results, the positive samples were subjected to purification to assess the MRSA growth kinetics. It was observed that there was a slight reduction in bacterial growth between serum samples with antibodies and MRSA compared to those of the serum with anti-MSSA (PBP2a negative). Therefore, the curve of growth ofMRSA was evaluated in the presence of purified immunoglobulins from the serumof patients colonized by MRSA (bacterial quantification). We observed that there was a drastic reduction in bacterial growth in the presence of immunoglobulins, thus demonstrating that these antibodies could have a protective action. These results indicated that: (i) MRSA colonized patients can produce antibodies against PBP2a and (ii) these antibodies can be protective against MRSA. These data suggest that a potential vaccine anti-PBP2a could be effective for prevention of infections caused byMRSA and for the use of passive immunotherapy in the treatment of patients infectedby this pathogen