Refractoriness of Eryptotic Red Blood Cells to Plasmodium falciparum Infection: A Putative Host Defense Mechanism Limiting Parasitaemia

Recently, we have described that apoptosis-like process of red blood cells (RBC) – eryptosis – in malaria is not restricted to parasitized cells, occurring also in non-parasitized RBC (nRBC). Besides to pathogenic proprieties, apoptosis also participates in the innate defense trough restriction of intracellular pathogens propagation. In the present study, we investigated the capacity of P. falciparum parasites to infect eryptotic RBC. Schizont parasitized RBC concentrated by magnetic separation were cultured with eryptotic RBC obtained by ionomycin treatment and, then, parasite growth was evaluated in Giemsa-stained thin blood smears. While parasites infected and developed normally in control non-eryptotic RBC, cultures performed with eryptotic RBC had a marked decrease in parasitaemia. It was noteworthy a great number of free merozoites in eryptotic RBC cultures, indicating that these cells were not susceptible to invasion. We suggest that although eryptosis could be involved in malaria pathogenesis, it could also acting protectively by controlling parasite propagation

Development of an immunoenzymatic assay using a monoclonal antibody against a 50-kDa catabolite from the P126 Plasmodium falciparum protein to the diagnosis of malaria infection

The WHO criterion of defering any donation of blood by a confirmed case of malaria for three years after cessation of therapy can not be applied in areas where malaria in endemic. For this reason we developed an immunoenzymatic assay for the detection of plasmodial antigens for blood screening in malararial endemic areas. So, we tested sera from 191 individuals. Among patients with active disease 100% of the cases of Plasmodium falciparum or mixed infections and 91.7% of those with P. vivax were positive for the presence of plasmodial antigens. The lower parasitaemia detected was 0.0003% for P. vivax malária. When the frequency of positive circulating malarial antigens was evaluated among asymptomatic and symptomatic individuals with negative TBS, positive results were found in respectively 38.7% and 17.7% of the individuals studied in the 30 days after confirmed malaria attack. Data provide by these assays have shown that ELISA seemed to be more sensitive than parasitological examination for malaria diagnosis. This test by virtue of its high sensivity and the facilities in processing a large number of specimens, can prove to be useful in endemic areas for the recognition of asymptomatic malaria and screening of blood donors

Apoptosis of non-parasitized red blood cells in malaria: a putative mechanism involved in the pathogenesis of anaemia

<p>Abstract</p> <p>Background</p> <p>Severe anaemia is a common complication of <it>Plasmodium falciparum </it>malaria in hyperendemic regions. Premature elimination of non-parasitized red blood cells (nRBC) has been considered as one mechanism involved in the genesis of severe malaria anaemia. It has been reported that apoptosis can occur in RBC and, consequently, this cell death process could contribute to anaemia. This study was performed to evaluate the susceptibility of nRBC to apoptosis in a malaria anaemia murine model.</p> <p>Methods</p> <p>Balb/c mice were intraperitonially inoculated with 1 × 10⁶<it>P. yoelii </it>17XL parasitized RBC (pRBC) and, then, parasitaemia and anaemia were monitored. Apoptosis in both pRBC and nRBC was assessed during early and late phases of infection by flow cytometry using Syto 16 and annexin V-PE double staining and forward scatter measurement.</p> <p>Results</p> <p>As expected, experimental infection of Balb/c mice with <it>Plasmodium yoelii </it>17XL parasites was characterized by progressive increase of parasitaemia and acute anaemia, leading to death. Flow cytometry analysis showed that a number of pRBC was in the apoptotic process. It was noteworthy that the increase of nRBC apoptosis levels occurred in the late phase of infection, when anaemia degree was notably accentuated, while no significant alteration was observed in the early phase.</p> <p>Conclusion</p> <p>The increased levels of nRBC apoptosis herein firstly reported, in malaria infection could represent a putative mechanism worsening the severity of malarial anaemia.</p

Brazilian Plasmodium falciparum isolates: investigation of candidate polymorphisms for artemisinin resistance before introduction of artemisinin-based combination therapy

<p>Abstract</p> <p>Background</p> <p>This study was performed to better understand the genetic diversity of known polymorphisms in <it>pfatpase6 </it>and <it>pfmdr1 </it>genes before the introduction of ACT in Brazil, in order to get a genotypic snapshot of <it>Plasmodium falciparum </it>parasites that may be used as baseline reference for future studies.</p> <p>Methods</p> <p>Parasites from <it>P. falciparum </it>samples collected in 2002, 2004 and 2006-2007 were genotyped using PCR and DNA sequencing at codons 86, 130, 184, 1034, 1042, 1109 and 1246 for <it>pfmdr1 </it>gene, and 243, 263, 402, 431, 623, 630, 639, 683, 716, 776, 769 and 771 for <it>pfatpase6 </it>gene.</p> <p>Results</p> <p>A <it>pfmdr1 </it>haplotype NEF/CDVY was found in 97% of the samples. In the case of <it>pfatpase6</it>, four haplotypes, wild-type (37%), 630 S (35%), 402 V (5%) and double-mutant 630 S + 402 V (23%), were detected.</p> <p>Conclusion</p> <p>Although some polymorphism in <it>pfmdr1 </it>and <it>pfatpase6 </it>were verified, no reported haplotypes in both genes that may mediate altered response to ACT was detected before the introduction of this therapy in Brazil. Thus, the haplotypes herein described can be very useful as a baseline reference of <it>P. falciparum </it>populations without ACT drug pressure.</p

Evaluation of the genetic polymorphism of Plasmodium falciparum P126 protein (SERA or SERP) and its influence on naturally acquired specific antibody responses in malaria-infected individuals living in the Brazilian Amazon

<p>Abstract</p> <p>Background</p> <p>The <it>Plasmodium falciparum </it>P126 protein is an asexual blood-stage malaria vaccine candidate antigen. Antibodies against P126 are able to inhibit parasite growth <it>in vitro</it>, and a major parasite-inhibitory epitope has been recently mapped to its 47 kDa N-terminal extremity (octamer repeat domain – OR domain). The OR domain basically consists of six octamer units, but variation in the sequence and number of repeat units may appear in different alleles. The aim of the present study was to investigate the polymorphism of P126 N-terminal region OR domain in <it>P. falciparum </it>isolates from two Brazilian malaria endemic areas and its impact on anti-OR naturally acquired antibodies.</p> <p>Methods</p> <p>The study was carried out in two villages, Candeias do Jamari (Rondonia state) and Peixoto de Azevedo (Mato Grosso state), both located in the south-western part of the Amazon region. The repetitive region of the gene encoding the P126 antigen was PCR amplified and sequenced with the di-deoxy chain termination procedure. The antibody response was evaluated by ELISA with the Nt47 synthetic peptide corresponding to the P126 OR-II domain.</p> <p>Results</p> <p>Only two types of OR fragments were identified in the studied areas, one of 175 bp (OR-I) and other of 199 bp (OR-II). A predominance of the OR-II fragment was observed in Candeias do Jamari whereas in Peixoto de Azevedo both fragments OR-I and OR-II were frequent as well as mixed infection (both fragments simultaneously) reported here for the first time. Comparing the DNA sequencing of OR-I and OR-II fragments, there was a high conservation among predicted amino acid sequences of the P126 N-terminal extremity. Data of immune response demonstrated that the OR domain is highly immunogenic in natural conditions of exposure and that the polymorphism of the OR domain does not apparently influence the specific immune response.</p> <p>Conclusion</p> <p>These findings confirm a limited genetic polymorphism of the P126 OR domain in <it>P. falciparum </it>isolates and that this limited genetic polymorphism does not seem to influence the development of a specific humoral immune response to P126 and its immunogenicity in the studied population.</p

Finding connections in the unexpected detection of Plasmodium vivax and Plasmodium falciparum DNA in asymptomatic blood donors: a fact in the Atlantic Forest

Abstract\ud A recent paper in Malaria Journal reported the observation of unexpected prevalence rates of healthy individuals carrying Plasmodium falciparum (5.14%) or Plasmodium vivax (2.26%) DNA among blood donors from the main transfusion centre in the metropolitan São Paulo, a non-endemic area for malaria. The article has been challenged by a group of authors who argued that the percentages reported were higher than those found in blood banks of the endemic Amazon Region and also that that paper had not considered the literature on the classical dynamics of malaria transmission in the Atlantic Forest, which involves Anopheles (Kerteszia) cruzii and bromeliad malaria, due to P. vivax and Plasmodium malariae parasites, but not P. falciparum. The present commentary paper responds to this challenge and brings evidence and literature data supporting that the observed prevalence ratios may indicate a proportion of individuals that are exposed to Plasmodium transmission in permissive environments; that blood carrying parasite DNA may not be necessarily infective if used in transfusion; and that in the literature, there are examples supporting the circulation of P. falciparum in the area.FAPES

Reemergence of human malaria in Atlantic Forest of Rio Grande do Sul, Brazil

Unforeseen Plasmodium infections in the Atlantic Forest of Brazilian Extra-Amazonian region could jeopardise malaria elimination. A human malaria case was registered in Três Forquilhas, in the Atlantic Forest biome of Rio Grande do Sul, after a 45 years’ time-lapsed without any malaria autochthonous notification in this southern Brazilian state. This finding represents the expansion of the malaria distribution areas in Brazil and the southernmost human malaria case record in South America in this decade. The coexistence of the bromeliad-breeding vector Anopheles (Kerteszia) cruzii and non-human primates in the Atlantic Forest regularly visited by the patient claimed for the zoonotic origin of this infection. The reemergence of Atlantic Forest human malaria in Rio Grande do Sul was also discussed

AÇÕES EDUCATIVAS DE PROMOÇÃO E PREVENÇÃO DAS EXPOSIÇÕES TÓXICAS:: a capacitação profissional continuada para o aproveitamento de novos saberes em Toxicologia

O objetivo deste estudo foi identificar e propor um modelo de ações e material didático para qualificação, promoção e prevenção, dos casos de intoxicações e acidentes por animais peçonhentos, para os profissionais da saúde que atuam na Atenção Básica, no município de Campina Grande, Paraíba, Brasil. A pesquisa foi desenvolvida no CEATOX (Centro de Assistência Toxicológica), entre os anos de 2010 e 2015. Antes e após a realização das ações educativas foi aplicado um Teste para avaliação do conhecimento sobre Toxicologia. Foi aplicado também, um questionário de satisfação (Escala de Likert). Os cinco principais casos de intoxicações notificados foram por medicamentos, serpentes, escorpiões, domissanitários e agrotóxicos. Ocorreram nas pessoas com faixa etária entre 10 e 39 anos, principalmente no gênero feminino e de forma acidental. Quanto ao teste teórico aplicado, o desempenho melhorou no pós-teste. No que diz respeito ao Nível de Satisfação dos Cursos desenvolvidos, verificou-se que todos os pesquisados ficaram muito satisfeitos e/ou satisfeitos com o treinamento, evidenciando uma grande aceitação por parte desses profissionais pesquisados. Foram confeccionados materiais didáticos na forma de Cordéis e Cartazes. Com isso, facilitou-se a disseminação do conhecimento científico com uma maior e melhor adequação da linguagem da realidade local sobre as intoxicações e acidentes com animais peçonhentos

Plasmodium falciparum isolates from Angola show the StctVMNT haplotype in the pfcrt gene

<p>Abstract</p> <p>Background</p> <p>Effective treatment remains a mainstay of malaria control, but it is unfortunately strongly compromised by drug resistance, particularly in <it>Plasmodium falciparum</it>, the most important human malaria parasite. Although <it>P. falciparum </it>chemoresistance is well recognized all over the world, limited data are available on the distribution and prevalence of <it>pfcrt </it>and <it>pfmdr1 </it>haplotypes that mediate resistance to commonly used drugs and that show distinct geographic differences.</p> <p>Methods</p> <p><it>Plasmodium falciparum</it>-infected blood samples collected in 2007 at four municipalities of Luanda, Angola, were genotyped using PCR and direct DNA sequencing. Single nucleotide polymorphisms in the <it>P. falciparum pfcrt </it>and <it>pfmdr1 </it>genes were assessed and haplotype prevalences were determined.</p> <p>Results and Discussion</p> <p>The most prevalent <it>pfcrt </it>haplotype was <b>S</b>_tctVMN<b>T </b>(representing amino acids at codons 72-76). This result was unexpected, since the <b>S</b>_tctVMN<b>T </b>haplotype has previously been seen mainly in parasites from South America and India. The CV<b>IET</b>, CVMN<b>T </b>and CV<b>I</b>N<b>T </b>drug-resistance haplotypes were also found, and one previously undescribed haplotype (CVM<b>DT</b>) was detected. Regarding <it>pfmdr1</it>, the most prevalent haplotype was <b>Y</b>EYSNVD (representing amino acids at codons 86, 130, 184, 1034, 1042, 1109 and 1246). Wild haplotypes for <it>pfcrt </it>and <it>pfmdr1 </it>were uncommon; 3% of field isolates harbored wild type <it>pfcrt </it>(CVMNK), whereas 21% had wild type <it>pfmdr1 </it>(NEYSNVD). The observed predominance of the <b>S</b>_tctVMN<b>T </b>haplotype in Angola could be a result of frequent travel between Brazil and Angola citizens in the context of selective pressure of heavy CQ use.</p> <p>Conclusions</p> <p>The high prevalence of the <it>pfcrt </it><b>S</b>VMN<b>T </b>haplotype and the <it>pfmdr1 </it>86<b>Y </b>mutation confirm high-level chloroquine resistance and might suggest reduced efficacy of amodiaquine in Angola. Further studies must be encouraged to examine the <it>in vitro </it>sensitivity of <it>pfcrt </it><b>S</b>VMN<b>T </b>parasites to artesunate and amodiaquine for better conclusive data.</p