EVALUATION OF THE IMMUNOGENIC RESPONSE OF PROTEIN EXTRACTS FROM Plasmodium berghei ANKA AND ITS POTENTIAL PROTECTIVE EFFECT IN EXPERIMENTAL INFECTION
malaria; protein extracts; immunogenicity; murine model.
Malaria is a parasitic disease with a wide distribution across continents and is an important public health issue worldwide, in view of the high annual morbidity and mortality rates. Immune responses against Plasmodium are complex and slow, as a protozoan mechanism to attenuate the host's immune processes to infection. Numerous efforts have been made towards the ability of Plasmodium proteins to modulate a protected immune response in the host in order to reduce the replication of the protozoan in the blood phase and minimize the complications of severe malaria. In this instance, this study aimed to analyze the ability of protein extracts originating from Plasmodium berghei ANKA to stimulate an immune response in the murine model and protect against the challenge. Thus, three immunization cycles were performed using the protein extract of Plasmodium berghei ANKA, associated with two different adjuvants: aluminum hydroxide and complete and incomplete Freund's adjuvant. In addition, this immunization schedule was also evaluated in mice already infected and previously treated, as well as in animals that were not previously infected. Each immunization was performed at an interval of 15 days, in female mice, Mus musculus species, Lineage BALB/C, aged between 6 and 8 weeks. 30 days after the last immunization, the animals were experimentally challenged with 1 x 105 parasitized red blood cells from Plasmodium berghei ANKA to analyze the protection of immunized mice by reducing parasitemia. A significant humoral immune response was observed compared to the control group already in the first immunization for the five patient IgG subclasses: Total IgG, IgG1, IgG3, IgG2a and IgG2b. As well as an increase in the production of cytophilic, in the murine model, IgG2a and IgG2b, for groups that were infected and treated before immunizations and then immunized. Furthermore, these same groups obtained a significant reduction in parasitemia after the challenge, in comparison with the other experimental groups. The analyzed data allow inferring that animals immunized with the aforementioned adjuvants have a high specific tolerance titre, as well as being less tolerant against the development of complications of severe malaria. However, the proteins involved in these immune responses elicited through immunizations need to be investigated in detail, in order to assess the immunodominance of each one of them.