BackgroundPlasmodium vivax has the potential to infect 2.85 billion individuals worldwide. Nevertheless, the limited number of studies investigating the immune status of individuals living in malaria-endemic areas, as well as the lack of reports investigating serological markers associated with clinical protection, has hampered development of vaccines for P. vivax. It was previously demonstrated that naturally total IgG against the N-terminus of P. vivax merozoite surface protein 1 (Pv-MSP1) was associated with reduced risk of malarial infection.MethodsImmune response against Pv-MSP1 (N-terminus) of 313 residents of the Rio Pardo rural settlement (Amazonas State, Brazil) was evaluated in a cross-sectional and longitudinal follow up over two months (on site) wherein gold standard diagnosis by thick blood smear and rRNA gene-based nested real-time PCR were used to discriminate symptomless Plasmodium vivax-infected individuals who did not develop clinical symptoms during a 2-months from those uninfected ones or who have had acute malaria. The acquisition of antibodies against Pv-MSP1 was also evaluated as survival analysis by prospective study over a year collecting information of new malaria infections in surveillance database.ResultsThe majority of P. vivax-infected individuals (52-67%) showed immune recognition of the N-terminus of Pv-MSP1. Interesting data on infected individuals who have not developed symptoms, total IgG levels against the N-terminus Pv-MSP1 were age-dependent and the IgG3 levels were significantly higher than levels of subjects had acute malaria or those uninfected ones. The total IgG anti ICB2-5 was detected to be an important factor of protection against new malaria vivax attacks in survival analysis in a prospective survey (p = 0.029).ConclusionsThe study findings illustrate the importance of IgG3 associated to 2-months of symptomless in P. vivax infected individuals and open perspectives for the rationale of malaria vaccine designs capable to sustain high levels of IgG3 against polymorphic malaria antigens.

The human malaria is widely distributed in the Middle East, Asia, the western Pacific, and Central and South America. Plasmodium vivax started to have the attention of many researchers since it is causing diseases to millions of people and several reports of severe malaria cases have been noticed in the last few years. The lack of in vitro cultures for P. vivax represents a major delay in developing a functional malaria vaccine. One of the major candidates to antimalarial vaccine is the merozoite surface protein-1 (MSP1), which is expressed abundantly on the merozoite surface and capable of activating the host protective immunity. Studies have shown that MSP-1 possesses highly immunogenic fragments, capable of generating immune response and protection in natural infection in endemic regions. This paper shows humoral immune response to different proteins of PvMSP1 and the statement of N-terminal to be added to the list of potential candidates for malaria vivax vaccine.

Historically, the alcohol consumption has been associated to occurrence of different crimes, including homicides, rapes and sexual assault, among others. Hence, the aim of this study was to evaluate the blood alcohol levels (BAC) in samples taken from medico- legal cases in Manaus, northern Brazil. An observational retrospective study covering May-2018 through April-2019 was carried out and the database of the referral center was employed. In total, 142 cases were evaluated. The mean age of participants was 36.2 ± 10.9 years (range 18-78 years, CI 95% 34.34-38.42) and the majority of them was male (87.32%), single (66.20%), attended the secondary school level (47.89%) and living in the city of Manaus at the time of the incidence (61.70%). The mean BAC was 0.20 ± 0.08 g/dL (range 0.1-0.64 g/dL, CI 95% 0.10-0.15). In relation to the incident, the weekday with most cases was Sunday (30.28%) and in the early morning (24 to 06 hours; 40.14%). Only a small percent was alive before the blood draw (7.04%) and traffic accidents were the most registered occurrence (61.27%). Cocaine was also found in some cases (4.23%). Highest BAC levels were observed for the homicide cases whereas lowest BAC values were attained for the suicide cases (p=0.01). Furthermore, there was a weak positive correlation between age and BAC (r=0.27; p=0.01). For the first time, the study of BAC in samples taken from medico-legal cases was performed in Manaus. Taking into account the results, authorities may develop dedicated strategies to deal with this problem.