Avaliação da resposta imunogênica de extratos proteicos de Plasmodium berghei ANKA e seu potencial efeito protetor na infecção experimental

Abstract

Malaria is a parasitic disease widely distributed across continents and is an important issue in public health worldwide, given the high annual rates of morbidity and mortality. Immune responses against Plasmodium are complex and slow, resulting from the mechanisms that the protozoan has to evade the host's immune processes against infection. Numerous efforts have been made to understand the ability of Plasmodium proteins to modulate a protective immune response in the host in order to reduce protozoan replication in the blood stage and minimize the complications of severe malaria. In this context, this study aimed to analyze the ability of protein extracts obtained from the erythrocytic phase of Plasmodium berghei ANKA to stimulate an effector immune response in the murine model and suppress parasitemia after challenge with 1x105 parasitized red blood cells, using the intraperitoneal route. Three cycles of immunizations were carried out using the crude extract of P. berghei ANKA, associated with two different adjuvants: Aluminum Hydroxide (HA) and Freund's Adjuvant (FA). Furthermore, this immunization scheme was also evaluated in infected mice that were subsequently treated and cured, as well as in animals without prior immunity against malaria. Each immunization was carried out at an interval of 15 days, in female mice, Mus musculus species, BALB/C lineage, aged 6 to 8 weeks. Thirty days after the last immunization, the animals were challenged with the infective inoculum and evaluated for humoral immune response and suppression of parasitemia. A significant humoral immune response was observed compared to the control group in the first immunization, with an increase in the production of cytophilic antibodies, IgG2a and IgG2b, for animals previously exposed to malaria. Furthermore, in these same groups, there was a suppression of parasitemia when compared to the group of uninfected/untreated animals. The experimental group composed of animals previously exposed to infection and immunized with protein extract/HA showed complete suppression of parasitemia on the 13th day. A similar result was observed in the group immunized with the protein extract/FA, showing a significant reduction in the parasite load, both in comparison to the control group and in comparison to the non-immunized group, but subjected to successive infections. The results obtained in this study show that animals immunized with the adjuvants used, in the condition of previous exposure to the parasite, present high levels of specific antibodies and, possibly, are less prone to the development of complications of severe malaria, when compared to the non-parasite group. immunized and with animals subjected to reinfection without immunization.