Clinical and immunological profiles of anaemia in children and adolescents with Plasmodium vivax malaria in the Pará state, Brazilian Amazon

Children and adolescents are at great risk for developing iron deficiency anaemia worldwide. In the tropical areas, malaria and intestinal parasites may also play an important role in anaemia pathogenesis. This study aimed at evaluating clinical and immunological aspects of anaemia in children and adolescents with Plasmodium vivax malaria, in the Pará State, Brazil. A longitudinal study was performed in two Reference Centers for malaria diagnosis in the Brazilian Amazon in children and adolescents with malaria (n = 81), as compared to a control group (n = 40). Patients had blood drawn three times [before treatment (D0), after treatment (D7) and at the first cure control (D30)] and hemogram, autoantibody analysis (anticardiolipin, antibodies against normal RBC membrane components) and cytokine studies (TNF and IL-10) were performed. Stool samples were collected for a parasitological examination. Malaria patients had a 2.7-fold greater chance of anaemia than the control group. At D0, 66.1% of the patients had mild anaemia, 30.5% had moderate and 3.5% had severe anaemia. Positivity to intestinal helminths and/or protozoa at stool examinations had no influence on anaemia. Patients had significantly lower levels of plasmatic TNF than control individuals at D0. Low TNF levels were more prevalent among patients with moderate/severe anaemia than in those with mild anaemia and among anaemic patients than in anaemic controls. TNF levels were positively correlated with the haemoglobin rates and negatively correlated with the interval time elapsed between the onset of symptoms and diagnosis. Both plasma TNF levels and haemoglobin rates increased during the follow-up period. The IL-10 levels were lower in patients than in the controls at day 0 and decreased thereafter up to the end of treatment. Only the anti-anticardiolipin autoantibodies were associated with moderate/severe anaemia and, possibly by reacting with the parasite glycosylphosphatidylinositol (a powerful stimulator of TNF production), may have indirectly contributed to decrease the TNF levels, which could be involved in the malarial vivax anaemia of these children and adolescents. More studies addressing this issue are necessary to confirm these findings and to add more information on the multifactorial pathogenesis of the malarial anaemia.

Cellular and humoral immune responses against the Plasmodium vivax MSP-1₁₉ malaria vaccine candidate in individuals living in an endemic area in north-eastern Amazon region of Brazil

BACKGROUND

Plasmodium vivax merozoite surface protein-1 (MSP-1) is an antigen considered to be one of the leading malaria vaccine candidates. PvMSP-1 is highly immunogenic and evidences suggest that it is target for protective immunity against asexual blood stages of malaria parasites. Thus, this study aims to evaluate the acquired cellular and antibody immune responses against PvMSP-1 in individuals naturally exposed to malaria infections in a malaria-endemic area in the north-eastern Amazon region of Brazil.

METHODS

The study was carried out in Paragominas, Pará State, in the Brazilian Amazon. Blood samples were collected from 35 individuals with uncomplicated malaria. Peripheral blood mononuclear cells were isolated and the cellular proliferation and activation was analysed in presence of 19 kDa fragment of MSP-1 (PvMSP-1₁₉) and Plasmodium falciparum PSS1 crude antigen. Antibodies IgE, IgM, IgG and IgG subclass and the levels of TNF, IFN-γ and IL-10 were measured by enzyme-linked immunosorbent assay.

RESULTS

The prevalence of activated CD4+ was greater than CD8+ T cells, in both ex-vivo and in 96 h culture in presence of PvMSP-1₁₉ and PSS1 antigen. A low proliferative response against PvMSP-1₁₉ and PSS1 crude antigen after 96 h culture was observed. High plasmatic levels of IFN-γ and IL-10 as well as lower TNF levels were also detected in malaria patients. However, in the 96 h supernatant culture, the dynamics of cytokine responses differed from those depicted on plasma assays; in presence of PvMSP-1₁₉ stimulus, higher levels of TNF were noted in supernatant 96 h culture of malaria patient's cells while low levels of IFN-γ and IL-10 were verified. High frequency of malaria patients presenting antibodies against PvMSP-1₁₉ was evidenced, regardless class or IgG subclass.PvMSP-119-induced antibodies were predominantly on non-cytophilic subclasses.

CONCLUSIONS

The results presented here shows that PvMSP-1₁₉ was able to induce a high cellular activation, leading to production of TNF and emphasizes the high immunogenicity of PvMSP-1₁₉ in naturally exposed individuals and, therefore, its potential as a malaria vaccine candidate.

Multifocal electroretinography after high dose chloroquine therapy for malaria

PURPOSE

To investigate changes in multifocal electroretinography (mfERG) parameters associated with high dose chloroquine therapy for treatment of malaria in the Amazonia region of Brazil.

METHODS

Forty-eight subjects who had received chloroquine treatment for single or multiple malaria infections with a cumulative dose ranging from 1,050 to 27,000mg were included. The control group consisted of 37 healthy aged-matched subjects. Data was collected on amplitude and implicit time of the N1, P1 and N2 waves in the central macular hexagon (R1) and in five concentric rings at different retinal eccentricities (R2-R6).

RESULTS

No significant difference was observed in any mfERG parameter between chloroquine treated patients and control subjects. A comparison with previous data obtained from patients with rheumatologic disorders in the same region of Brazil who had received larger cumulative doses of chloroquine and had displayed mfERG changes, indicated that retinal toxicity seems to be dependent on cumulative dose.

CONCLUSION

Lack of mfERG changes in the current study suggests that intensive high dose chloroquine therapy for treatment of malaria is not associated with retinal toxicity.

Characterisation of pvmdr1 and pvdhfr genes associated with chemoresistance in Brazilian Plasmodium vivax isolates

Plasmodium vivax control is now being hampered by drug resistance. Orthologous Plasmodium falciparum genes linked to chloroquine or sulfadoxine-pyrimethamine chemoresistance have been identified in P. vivax parasites, but few studies have been performed. The goal of the present work is to characterise pvmdr1 and pvdhfr genes in parasite isolates from a Brazilian endemic area where no molecular investigation had been previously conducted. The pvmdr1 analysis revealed the existence of single (85.7%) and double (14.3%) mutant haplotypes, while the pvdhfr examination showed the presence of double (57.2%) and triple (42.8%) mutant haplotypes. The implications of these findings are discussed.

Chloroquine and sulphadoxine-pyrimethamine sensitivity of Plasmodium falciparum parasites in a Brazilian endemic area

BACKGROUND

The goal of the present study was the characterization of Plasmodium falciparum genes associated to malaria drug resistance (pfcrt, pfdhfr and pfdhps), in samples from two Brazilian localities.

METHODS

Parasites from 65 P. falciparum samples were genotyped using nested-PCR and direct DNA sequencing.

RESULTS

Six resistant sulphadoxine-pyrimethamine (SP) pfdhfr genotypes and one haplotype associated to SP sensitivity were detected. For pfcrt gene, SVMNT chloroquine (CQ)-resistant genotype was detected as well as the CVMNK CQ-sensitive haplotype in the same sample from Paragominas, that showed a SP-sensitive genotype.

CONCLUSION

This study is the first to document the sensitivity of P. falciparum parasites to CQ and SP in Brazilian field samples. The importance of these findings is discussed.

Real-time PCR versus conventional PCR for malaria parasite detection in low-grade parasitemia

We have optimized a faster and cheaper real-time PCR and developed a conventional genus specific PCR based on 18S rRNA gene to detect malaria parasites in low-grade parasitemias. Additionally, we compared these PCRs to the OptiMAL-IT test. Since there is no consensus on choice of standard quantitative curve in real-time assays, we decided to investigate the performance of parasite DNA from three different sources: "genome", amplicon and plasmid. The amplicon curve showed the best efficiency in quantifying parasites. Both PCR assays detected 100% of the clinical samples tested; the sensitivity threshold was 0.5 parasite/mul and no PCR positive reaction occurred when malaria parasites were not present. Conversely, if OptiMAL-IT were employed for malaria diagnosis, 30% of false-negative results could be expected. We conclude that PCR assays have potential for detecting malaria parasites in asymptomatic infections, in evaluation of malaria vaccine molecule candidates, for screening blood donors, especially in endemic areas, or even in monitoring malaria therapy.

Some aspects of the behavior of the hypothalamus-pituitary-adrenal axis in patients with uncomplicated Plasmodium falciparum malaria: Cortisol and dehydroepiandrosterone levels

We studied the behavior of cortisol and dehydroepiandrosterone (DHEA) in 24 patients with uncomplicated Plasmodium falciparum malaria of the Evandro Chagas Institute, Belém, Pará, Brazil. The patients were evaluated before treatment (Day 0), 24h after the beginning of medication (Day 1) and on Day 8 of follow-up (Day 7). Steroid levels were correlated with parasitemia, temperature and time of the disease. The levels of these hormones were found to be significantly higher on Day 0 than on Day 7, showing no correlation with parasitemia or temperature, but temperature had a positive effect on the correlation between cortisol and dehydroepiandrosterone. Cortisol was not correlated with the time of disease, but a significant negative correlation was observed between DHEA and time of disease on Day 7, suggesting a decline in the adrenal reserve of this steroid. In conclusion, an increase in cortisol and dehydroepiandrosterone is observed in patients with falciparum malaria, with these levels declining with decreasing parasitemia. The finding that temperature interfered with the correlation between cortisol and dehydroepiandrosterone suggests a common mechanism for the activation of these hormones in malaria.

Genetic polymorphism of the serine rich antigen N-terminal region in Plasmodium falciparum field isolates from Brazil

In this work we investigated the frequency of polymorphism in exon II of the gene encoding most of the amino-terminal region of the serine rich antigen (SERA) in Plasmodium falciparum field samples. The blood samples were collected from P. falciparum infected individuals in three areas of the Brazilian Amazon. Two fragments have been characterized by polymerase chain reaction: one of 175 bp corresponding to the repeat region with 5 octamer units and one other of 199 bp related to the 6 repeat octamer units of SERA protein. The 199 bp fragment was the predominant one in all the studied areas. The higher frequency of this fragment has not been described before and could be explained by an immunological selection of the plasmodial population in the infected individuals under study. Since repeat motifs in the amino-terminal region of SERA contain epitopes recognized by parasite-inhibitor antibodies, data reported here suggest that the analysis of the polymorphism of P. falciparum isolates in different geographical areas is a preliminary stage before the final drawing of an universal vaccine against malaria can be reached.

Assessment of chloroquine single dose treatment of malaria due to Plasmodium vivax in Brazilian Amazon

Malaria regions of the Amazon basin have been characterized by difficult access and non-compliance of the patients to treatment. In an attempt to assess the schizonticide efficacy of chloroquine in a single dose of 600 mg, the authors realized a double-blind, placebo-controlled trial in 132 outpatients with vivax malaria. Patients were distributed into two groups: group CPLA, given chloroquine 600 mg (single dose) on the first day of treatment, and two doses of placebo on second and third days. Group CHLO, given chloroquine 600 mg on first day and 450 mg on second and third day. Geometric means of the parasite density during the follow-up was similar in both groups. No differences were observed in the parasitological cure between the two groups (p = 0.442). There was clinical and parasitological efficacy in treatment of patients given a single-dose of chloroquine. This suggests that its restricted use could be indicated in remote areas of Brazilian Amazon Region, nevertheless the inadequate response of three patients indicates the need for further studies.

[Importance of clinical and laboratory profiles for the differential diagnosis of malaria and acute viral hepatitis]

OBJECTIVE

To establish clinical and diagnostic findings of malaria and acute viral hepatitis in children, stressing similarities and differences, so as to enhance the sensitivity of early malaria diagnosis in childhood.

METHODS

Two groups were studied, each including 30 children between 2 and 10 years of age. The patients presented either primary malaria infection or acute viral hepatitis, confirmed by thick blood film and tests for markers of viral hepatitis A and B. The patients were submitted to the following evaluations: erythrocyte, leucocyte and platelet counts, hemoglobin and hematocrit dosage, hepatic enzymes, urea, creatinine and bilirubin dosage. Clinical and laboratory findings were described for both groups and compared. Individuals with alterations on the physical exam in both groups were compared using Fisher's exact test.

RESULTS

Baseline clinical findings were the same in all patients: fever, headache, digestive problems and dark urine. One half of malaria patients did not present the classical malaria signs, but all of them presented fever, differently from patients with hepatitis. In malaria patients, anemia and thrombocytopenia were significantly more frequent than in hepatitis patients. A remarkable increase of bilirubin and hepatic enzyme levels was found in hepatitis patients.

CONCLUSIONS

A detailed physical examination and a thorough evaluation of non-specific laboratory tests are sufficient to allow the presumptive diagnosis of both malaria and viral hepatitis, and to reinforce the early diagnosis and treatment of malaria.

Esquemas terapêuticos encurtados para o tratamento de malária por Plasmodium vivax

Visando avaliar esquemas terapêuticos encurtados eficazes no tratamento de malária vivax, foi realizado um estudo aberto, prospectivo, alocando 234 pacientes com malária por P. vivax, distribuídos aleatoriamente em 8 grupos terapêuticos. Seis grupos usaram como esquizonticida sangüíneo o artesunato via oral em diferentes dosagens por um dia e aos outros dois grupos foi administrada a cloroquina em dose única. Como hipnozoiticida, foi utilizada a primaquina em dose diária de 30mg dia durante cinco ou sete dias, em ambos os grupos. O desaparecimento da parasitemia nos pacientes tratados com artesunato (independente da dose) foi mais rápido quando comparados aos que fizeram uso de cloroquina (p<0,01). Cura ocorreu em 92,3% e 80,2%, respectivamente nos pacientes tratados com primaquina por sete e cinco dias (p=0,0372), independente do esquizonticida sanguíneo utilizado.

[Short course schemes for vivax malaria treatment]

with the objective of evaluating shortened therapeutic outlines effective in vivax malaria treatment, we accomplished an open, prospective study allocating 234 patients with vivax malaria distributed at random into eight therapeutic groups. Six groups used oral arthemisin as blood esquizonticide at different doses for one day and the other two groups received chloroquine in a single dose. The primaquine was used as a hypnozoiticide in all groups. They received a daily dose of 30mg in the course of five or seven days in all groups. The clearance of parasitaemia in patients treated with arthemisin (independent of dosage) was faster than the chloroquine group (p <0.01). Cure was acheived in 92.3% and 80.2%, in patients treated with primaquine for seven or five days, respectively (p=0.0372).