A conserved epitope in VAR2CSA is targeted by a cross-reactive antibody originating from Plasmodium vivax Duffy binding protein

During Plasmodium falciparum infection in pregnancy, VAR2CSA is expressed on the surface of infected erythrocytes (IEs) and mediates their sequestration in the placenta. As a result, antibodies to VAR2CSA are largely restricted to women who were infected during pregnancy. However, we discovered that VAR2CSA antibodies can also be elicited by P. vivax Duffy binding protein (PvDBP). We proposed that infection with P. vivax in non-pregnant individuals can generate antibodies that cross-react with VAR2CSA. To better understand the specificity of these antibodies, we took advantage of a mouse monoclonal antibody (3D10) raised against PvDBP that cross-reacts with VAR2CSA and identified the epitopes targeted by this antibody. We screened two peptide arrays that span the ectodomain of VAR2CSA from the FCR3 and NF54 alleles. Based on the top epitope recognized by 3D10, we designed a 34-amino acid synthetic peptide, which we call CRP1, that maps to a highly conserved region in DBL3X. Specific lysine residues are critical for 3D10 recognition, and these same amino acids are within a previously defined chondroitin sulfate A (CSA) binding site in DBL3X. We showed by isothermal titration calorimetry that the CRP1 peptide can bind directly to CSA, and antibodies to CRP1 raised in rats significantly blocked the binding of IEs to CSA in vitro. In our Colombian cohorts of pregnant and non-pregnant individuals, at least 45% were seroreactive to CRP1. Antibody reactivities to CRP1 and the 3D10 natural epitope in PvDBP region II, subdomain 1 (SD1), were strongly correlated in both cohorts. These findings suggest that antibodies arising from PvDBP may cross-react with VAR2CSA through the epitope in CRP1 and that CRP1 could be a potential vaccine candidate to target a distinct CSA binding site in VAR2CSA.

Epidemiology and impact of frailty in patients with atrial fibrillation in Europe

BACKGROUND

Frailty is a medical syndrome characterised by reduced physiological reserve and increased vulnerability to stressors. Data regarding the relationship between frailty and atrial fibrillation (AF) are still inconsistent.

OBJECTIVES

We aim to perform a comprehensive evaluation of frailty in a large European cohort of AF patients.

METHODS

A 40-item frailty index (FI) was built according to the accumulation of deficits model in the AF patients enrolled in the ESC-EHRA EORP-AF General Long-Term Registry. Association of baseline characteristics, clinical management, quality of life, healthcare resources use and risk of outcomes with frailty was examined.

RESULTS

Among 10,177 patients [mean age (standard deviation) 69.0 (11.4) years, 4,103 (40.3%) females], 6,066 (59.6%) were pre-frail and 2,172 (21.3%) were frail, whereas only 1,939 (19.1%) were considered robust. Baseline thromboembolic and bleeding risks were independently associated with increasing FI. Frail patients with AF were less likely to be treated with oral anticoagulants (OACs) (odds ratio 0.70, 95% confidence interval 0.55-0.89), especially with non-vitamin K antagonist OACs and managed with a rhythm control strategy, compared with robust patients. Increasing frailty was associated with a higher risk for all outcomes examined, with a non-linear exponential relationship. The use of OAC was associated with a lower risk of outcomes, except in patients with very/extremely high frailty.

CONCLUSIONS

In this large cohort of AF patients, there was a high burden of frailty, influencing clinical management and risk of adverse outcomes. The clinical benefit of OAC is maintained in patients with high frailty, but not in very high/extremely frail ones.

Comparative clinical prognosis of massive and non-massive pulmonary embolism: A registry-based cohort study

AIMS

Little is known about the prognosis of patients with massive pulmonary embolism (PE) and its risk of recurrent venous thromboembolism (VTE) compared with non-massive PE, which may inform clinical decisions. Our aim was to compare the risk of recurrent VTE, bleeding, and mortality after massive and non-massive PE during anticoagulation and after its discontinuation.

METHODS AND RESULTS

We included all participants in the RIETE registry who suffered a symptomatic, objectively confirmed segmental or more central PE. Massive PE was defined by a systolic hypotension at clinical presentation (<90 mm Hg). We compared the risks of recurrent VTE, major bleeding, and mortality using time-to-event multivariable competing risk modeling. There were 3.5% of massive PE among 38 996 patients with PE. During the anticoagulation period, massive PE was associated with a greater risk of major bleeding (subhazard ratio [sHR] 1.72, 95% confidence interval [CI] 1.28-2.32), but not of recurrent VTE (sHR 1.15, 95% CI 0.75-1.74) than non-massive PE. An increased risk of mortality was only observed in the first month after PE. After discontinuation of anticoagulation, among 11 579 patients, massive PE and non-massive PE had similar risks of mortality, bleeding, and recurrent VTE (sHR 0.85, 95% CI 0.51-1.40), but with different case fatality of recurrent PE (11.1% versus 2.4%, P = .03) and possibly different risk of recurrent fatal PE (sHR 3.65, 95% CI 0.82-16.24).

CONCLUSION

In this large prospective registry, the baseline hemodynamic status of the incident PE did not influence the risk of recurrent VTE, during and after the anticoagulation periods, but was possibly associated with recurrent PE of greater severity.

Spanish cohort profile, antithrombotic therapy and clinical outcomes at 1 year in the EORP atrial fibrillation long-term registry

Background

Atrial fibrillation (AF) is associated with a high risk of stroke and mortality. Some years ago, the EURObservational Research Programme launched the General Long-Term Registry with the aim to evaluate contemporary management of AF patients in Europe, the current use of vitamin K antagonists (VKAs), direct-acting oral anticoagulants (DOACs) and other AF treatments, in relation to guideline recommendations.

Purpose

The present report aims to describe the characteristics of a large database on the management of AF in Spain, using the Spanish cohort included in the EORP-AF Long-Term Registry.

Methods

The EORP-AF Long-Term General Registry is a prospective, observational, large-scale multicentre registry sponsored and conducted by the ESC, enrolling AF patients in current cardiology practices in 250 centres from 27 participating ESC countries. Patients were enrolled consecutively when presenting with AF as primary or secondary diagnosis to inpatients and outpatient cardiology services from October 2013 to September 2016. The first Spanish patient in the EORP-AF Long-Term Registry was included in 2014. Initially, the aim was to carry out a follow-up up to 3 years but this was reduced to 2 years by the Executive Committee. To date, only data from the first year of follow-up is available for the Spanish cohort.

Results

A cohort of 729 AF Spanish patients was included (57.1% male, median age 75 [IQR 67–81] years, median CHA2DS2-VASc and HAS-BLED of 3 [IQR 2–5] and 2 [IQR 1–2], respectively). A relatively low proportion of patients (634, 87%) received oral anticoagulants (OACs), of which 389 (53.4%) were on VKAs and 245 (33.6%) were on DOACs (rate ratio = 1.59 [95% CI 1.35–1.87], p&lt;0.001). Importantly, there were 98 (13.4%) patients taking concomitantly antiplatelet therapy and OACs; as well as 5.5% of patients were taking parenteral anticoagulation or antiplatelets alone. After 1 year, the proportion of patients on OACs increased from 87.0% to 88.1%. The proportion of DOACs users increased from 33.6% at baseline to 39.9%, partly due to switches from VKA to DOACs in relation to poor time in therapeutic range. At the same time, 34 (4.7%) patients withdrew OACs. During the first year of follow-up, 48 patients (6.6%) died, 7 (1.0%) suffered ischemic strokes and 6 (0.8%) transient ischemic attacks. Of note, there was a substantial rate of major bleeds (ISTH criteria) (57, 7.8%), of which 10 (1.4%) were intracranial haemorrhages.

Conclusions

Baseline data of the Spanish cohort are similar to that reported for the whole EORP cohort, including similar stroke and bleeding risks. OAC use slightly increased at 1-year, with low discontinuation rates which could be related with a low incidence of thromboembolic events. However, despite the ∼8% rate of major bleeding in overall, the use of a safer therapy such as DOACs is still low compared to VKAs, being the antiplatelets commonly used concomitantly with OACs

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Unconditional grant by Boehringer-Ingelheim

D-dimer levels and risk of recurrence following provoked venous thromboembolism: findings from the RIETE registry

BACKGROUND

Patients with venous thromboembolism (VTE) secondary to transient risk factors may develop VTE recurrences after discontinuing anticoagulation. Identifying at-risk patients could help to guide the duration of therapy.

METHODS

We used the RIETE database to assess the prognostic value of d-dimer testing after discontinuing anticoagulation to identify patients at increased risk for recurrences. Transient risk factors were classified as major (postoperative) or minor (pregnancy, oestrogen use, immobilization or recent travel).

RESULTS

In December 2018, 1655 VTE patients with transient risk factors (major 460, minor 1195) underwent d-dimer measurements after discontinuing anticoagulation. Amongst patients with major risk factors, the recurrence rate was 5.74 (95% CI: 3.19-9.57) events per 100 patient-years in those with raised d-dimer levels and 2.68 (95% CI: 1.45-4.56) in those with normal levels. Amongst patients with minor risk factors, the rates were 7.79 (95% CI: 5.71-10.4) and 3.34 (95% CI: 2.39-4.53), respectively. Patients with major risk factors and raised d-dimer levels (n = 171) had a nonsignificantly higher rate of recurrences (hazard ratio [HR]: 2.14; 95% CI: 0.96-4.79) than those with normal levels. Patients with minor risk factors and raised d-dimer levels (n = 382) had a higher rate of recurrences (HR: 2.34; 95% CI: 1.51-3.63) than those with normal levels. On multivariate analysis, raised d-dimers (HR: 1.74; 95% CI: 1.09-2.77) were associated with an increased risk for recurrences in patients with minor risk factors, not in those with major risk factors.

CONCLUSIONS

Patients with raised d-dimer levels after discontinuing anticoagulant therapy for VTE provoked by a minor transient risk factor were at an increased risk for recurrences.

Cross-Species Immune Recognition Between Plasmodium vivax Duffy Binding Protein Antibodies and the Plasmodium falciparum Surface Antigen VAR2CSA

Background

In pregnancy, Plasmodium falciparum parasites express the surface antigen VAR2CSA, which mediates adherence of red blood cells to chondroitin sulfate A (CSA) in the placenta. VAR2CSA antibodies are generally acquired during infection in pregnancy and are associated with protection from placental malaria. We observed previously that men and children in Colombia also had antibodies to VAR2CSA, but the origin of these antibodies was unknown. Here, we tested whether infection with Plasmodium vivax is an alternative mechanism of acquisition of VAR2CSA antibodies.

Methods

We analyzed sera from nonpregnant Colombians and Brazilians exposed to P. vivax and monoclonal antibodies raised against P. vivax Duffy binding protein (PvDBP). Cross-reactivity to VAR2CSA was characterized by enzyme-linked immunosorbent assay, immunofluorescence assay, and flow cytometry, and antibodies were tested for inhibition of parasite binding to CSA.

Results

Over 50% of individuals had antibodies that recognized VAR2CSA. Affinity-purified PvDBP human antibodies and a PvDBP monoclonal antibody recognized VAR2CSA, showing that PvDBP can give rise to cross-reactive antibodies. Importantly, the monoclonal antibody inhibited parasite binding to CSA, which is the primary in vitro correlate of protection from placental malaria.

Conclusions

These data suggest that PvDBP induces antibodies that functionally recognize VAR2CSA, revealing a novel mechanism of cross-species immune recognition to falciparum malaria.

Submicroscopic Plasmodium infection during pregnancy is associated with reduced antibody levels to tetanus toxoid

Submicroscopic Plasmodium infections in pregnancy are common in endemic areas, and it is important to understand the impact of these low-level infections. Asymptomatic, chronic infections are advantageous for parasite persistence, particularly in areas where the optimal eco-epidemiological conditions for parasite transmission fluctuate. In chronic infections, the persistence of the antigenic stimulus changes the expression of immune mediators and promotes constant immune regulation, including increases in regulatory T cell populations. These alterations of the immune system could compromise the response to routine vaccination. This study aimed to evaluate the effect of submicroscopic plasmodial infection with P. falciparum and P. vivax during pregnancy on the immune response to the tetanus toxoid vaccine in Colombian women. Expression of different cytokines and mediators of immune regulation and levels of anti-tetanus toxoid (TT) immunoglobulin (Ig)G were quantified in pregnant women with and without submicroscopic plasmodial infection. The anti-TT IgG levels were significantly lower in the infected group compared with the uninfected group. The expression of interferon (IFN)-γ, tumour necrosis factor (TNF) and forkhead box protein 3 (FoxP3) was significantly higher in the infected group, while the expression of cytotoxic T lymphocyte antigen 4 (CTLA-4) and transforming growth factor (TGF)-β was lower in the group of infected. In conclusion, submicroscopic Plasmodium infection altered the development of the immune response to the TT vaccine in Colombian pregnant women. The impact of Plasmodium infections on the immune regulatory pathways warrants further exploration.

Clinical Outcomes of Submicroscopic Infections and Correlates of Protection of VAR2CSA Antibodies in a Longitudinal Study of Pregnant Women in Colombia

Malaria in pregnancy can cause serious adverse outcomes for the mother and the fetus. However, little is known about the effects of submicroscopic infections (SMIs) in pregnancy, particularly in areas where Plasmodium falciparum and Plasmodium vivax cocirculate. A cohort of 187 pregnant women living in Puerto Libertador in northwest Colombia was followed longitudinally from recruitment to delivery. Malaria was diagnosed by microscopy, reverse transcription-quantitative PCR (RT-qPCR), and placental histopathology. Gestational age, hemoglobin concentration, VAR2CSA-specific IgG levels, and adhesion-blocking antibodies were measured during pregnancy. Statistical analyses were performed to evaluate the impact of SMIs on birth weight and other delivery outcomes. Twenty-five percent of women (45/180) were positive for SMIs during pregnancy. Forty-seven percent of infections (21/45) were caused by P. falciparum, 33% were caused by P. vivax, and 20% were caused by mixed Plasmodium spp. Mixed infections of P. falciparum and P. vivax were associated with lower gestational age at delivery (P = 0.0033), while other outcomes were normal. Over 60% of women had antibodies to VAR2CSA, and there was no difference in antibody levels between those with and without SMIs. The anti-adhesion function of these antibodies was associated with protection from SMI-related anemia at delivery (P = 0.0086). SMIs occur frequently during pregnancy, and while mixed infections of both P. falciparum and P. vivax were not associated with a decrease in birth weight, they were associated with significant risk of preterm birth. We propose that the lack of adverse delivery outcomes is due to functional VAR2CSA antibodies that can protect pregnant women from SMI-related anemia.

Evolutionary structure of Plasmodium falciparum major variant surface antigen genes in South America: Implications for epidemic transmission and surveillance

Strong founder effects resulting from human migration out of Africa have led to geographic variation in single nucleotide polymorphisms (SNPs) and microsatellites (MS) of the malaria parasite, Plasmodium falciparum. This is particularly striking in South America where two major founder populations of P. falciparum have been identified that are presumed to have arisen from the transatlantic slave trade. Given the importance of the major variant surface antigen of the blood stages of P. falciparum as both a virulence factor and target of immunity, we decided to investigate the population genetics of the genes encoding “Plasmodium falciparum Erythrocyte Membrane Protein 1” (PfEMP1) among several countries in South America, in order to evaluate the transmission patterns of malaria in this continent. Deep sequencing of the DBLα domain of var genes from 128 P. falciparum isolates from five locations in South America was completed using a 454 high throughput sequencing protocol. Striking geographic variation in var DBLα sequences, similar to that seen for SNPs and MS markers, was observed. Colombia and French Guiana had distinct var DBLα sequences, whereas Peru and Venezuela showed an admixture. The importance of such geographic variation to herd immunity and malaria vaccination is discussed.

Efficacy of Different Primaquine Regimens to Control Plasmodium falciparum Gametocytemia in Colombia

Treatment against Plasmodium falciparum malaria includes blood schizonticides to clear asexual parasites responsible for disease. The addition of gametocytocidal drugs can eliminate infectious sexual stages with potential for transmission and the World Health Organization recommends a single dose (SD) of primaquine (PQ) to this end. The efficacy of PQ at 0.75 mg/kg to suppress gametocytemia when administered in single or fractionated doses was evaluated. A clinical controlled study with an open-label design was executed; three groups of 20 subjects were studied sequentially. All subjects were treated with the standard dose of artemether-lumefantrine plus the total dose of 0.75 mg/kg of PQ administered (without previous G6PD testing) in three different ways: Group "0.75d-3" received 0.75 mg/kg on day 3; Group "0.50d-1 + 0.25d-3" received 0.50 mg/kg on day 1 and 0.25 mg/kg on day 3; Group "0.25d-1,2,3" received 0.25 mg/kg on days 1, 2, and 3. Subjects were evaluated on days 1, 4, and 7 by thick smear microscopy and quantitative polymerase chain reaction to determine the carriage of immature and mature gametocytes. There were no adverse events. The three schemes caused a marked reduction (75-85%) in prevalence of gametocytes on day 4 compared with day 1, but only the group that received 0.75 mg/kg on day 3 maintained the reduced gametocyte burden until day 7. None of the three treatments were able to clear gametocyte carriage on days 4 or 7, but the group that received the SD had the lowest prevalence of gametocytes (15%). Further studies are needed to establish a PQ regimen with complete efficacy against gametocytes.

Microscopic detection of hemozoin in peripheral leukocytes fails to indicate plasmodial placental infection in pregnant women

INTRODUCTION

Malaria in pregnancy very often includes gestational (parasites in maternal peripheral blood) and placental (parasites in placental blood) infection, but the later condition can only be detected after delivery. High frequency of placental plasmodial infection has been confirmed in many countries and is associated with negative birth outcomes. With the hypothesis that placental infection is accompanied by hemozoin circulation in maternal peripheral blood, an exploratory study was conducted to evaluate the association between peripheral leukocytes with hemozoin and placental infection by Plasmodium vivax or Plasmodium falciparum in parturient women.

METHODOLOGY

A descriptive, transversal and exploratory (pilot type) study was carried out with women from two malaria-endemic localities of northwest Colombia. A total of 25 parturient women with confirmed placental infection and 25 without placental infection were included. Two independent readers measured the number of leukocytes with hemozoin in thick smears of maternal peripheral blood. Plasmodial infection in maternal peripheral blood and placental blood was detected by thick smear and quantitative polymerase chain reaction (qPCR).

RESULTS

Four parturient women had leukocytes with hemozoin in peripheral blood; three of them had placental plasmodial infection and one was negative for placental infection. No statistically significant association between leukocytes with hemozoin in peripheral blood and placental infection was observed.

CONCLUSIONS

With this limited sample size, detection of leukocytes with hemozoin by thick smear of maternal peripheral blood did not indicate presence of placental infection.

Outcome of Patients with Venous Thromboembolism and Factor V Leiden or Prothrombin 20210 Carrier Mutations During the Course of Anticoagulation

BACKGROUND

Individuals with factor V Leiden or prothrombin G20210A mutations are at a higher risk to develop venous thromboembolism. However, the influence of these polymorphisms on patient outcome during anticoagulant therapy has not been consistently explored.

METHODS

We used the Registro Informatizado de Enfermedad TromboEmbólica database to compare rates of venous thromboembolism recurrence and bleeding events occurring during the anticoagulation course in factor V Leiden carriers, prothrombin mutation carriers, and noncarriers.

RESULTS

Between March 2001 and December 2015, 10,139 patients underwent thrombophilia testing. Of these, 1384 were factor V Leiden carriers, 1115 were prothrombin mutation carriers, and 7640 were noncarriers. During the anticoagulation course, 160 patients developed recurrent deep vein thrombosis and 94 patients developed pulmonary embolism (16 died); 154 patients had major bleeding (10 died), and 291 patients had nonmajor bleeding. On multivariable analysis, factor V Leiden carriers had a similar rate of venous thromboembolism recurrence (adjusted hazard ratio [HR], 1.16; 95% confidence interval [CI], 0.82-1.64), half the rate of major bleeding (adjusted HR, 0.50; 95% CI, 0.25-0.99) and a nonsignificantly lower rate of nonmajor bleeding (adjusted HR, 0.66; 95% CI, 0.43-1.01) than noncarriers. Prothrombin mutation carriers and noncarriers had a comparable rate of venous thromboembolism recurrence (adjusted HR, 1.00; 95% CI, 0.68-1.48), major bleeding (adjusted HR, 0.75; 95% CI, 0.42-1.34), and nonmajor bleeding events (adjusted HR, 1.10; 95% CI, 0.77-1.57).

CONCLUSIONS

During the anticoagulation course, factor V Leiden carriers had a similar risk for venous thromboembolism recurrence and half the risk for major bleeding compared with noncarriers. This finding may contribute to decision-making regarding anticoagulation duration in selected factor V Leiden carriers with venous thromboembolism.

Impact of Malaria in Pregnancy as Latin America Approaches Elimination

In Latin America, four million pregnancies are at risk of malaria annually, but malaria in pregnancy is largely overlooked. As countries progress toward malaria elimination, targeting reservoirs of transmission is a priority. Pregnant women are an important risk group because they harbor asymptomatic infections and dormant liver stages of Plasmodium vivax that cause relapses. Of significant concern is the discovery that most infections in pregnant women fail to be detected by routine diagnostics. We review here recent findings on malaria in pregnancy within Latin America. We focus on the Amazon basin and Northwest Colombia, areas that harbor the greatest burden of malaria, and propose that more sensitive diagnostics and active surveillance at antenatal clinics will be necessary to eliminate malaria from these final frontiers.

Immune responses during gestational malaria: a review of the current knowledge and future trend of research

Women pregnant with their first child are susceptible to severe P. falciparum disease from placental malaria because they lack immunity to placenta-specific cytoadherence proteins. In subsequent pregnancies, as immunity against placental parasites is acquired, there is a reduced risk of adverse effects of malaria on the mother and fetus and asymptomatic parasitaemia is common. In the case of vivax malaria, with increasing reports of severe cases in Asia and South America, the effects of infection by this species during pregnancy remain to be elucidated. This review summarized the main aspects involved in the acquisition of specific antimalarial immune responses during pregnancy with emphasis in research carried out in America and Asia, in order to offer a framework of interpretation for studies on pregnant women with malaria which are recently being produced in these regions. The authors conclude that (1) Effective humoral responses during gestational malaria are mainly directed against variant surface antigens codified by genes of the var2Csa family of P. falciparum; (2) Acquisition of immunity against these variant antigens depends on the degree and intensity of transmission, and the chance increases with age and successive pregnancies; (3) Antibody development is guided by specific cellular immune responses in cases of placental and maternal infection, and (4) The study of the significance of acquisition of specific immunity against both P. falciparum and P. vivax in America, should be performed.

Submicroscopic infection of placenta by Plasmodium produces Th1/Th2 cytokine imbalance, inflammation and hypoxia in women from north-west Colombia

BACKGROUND

A large-scale study was set up in order to study the epidemiology, clinical aspects, and immunopathology of gestational and placental malaria in north-west Colombia. In this region, recent reports using a qPCR technique, confirmed frequencies of infection, by Plasmodium falciparum or Plasmodium vivax, up to 45%. Given the high rates of infection observed both in mother and placenta, a first exploratory study was proposed in order to characterize the effect on the inflammation status, tissue damage and hypoxia in Plasmodium spp. infected placentas.

METHODS

A descriptive, prospective, cross-sectional design was applied to pregnant women with (PM+) and without (PM-) placental malaria. Messenger RNA expression of Fas, FasL; COX-1, COX-2, HIF, VEGF, and the cytokines IL-2, IL-4, IL-10, IFN-γ and TNF, were measured in peripheral and placental blood using a quantitative PCR. The percentage of apoptotic cells was determined with a TUNEL assay.

RESULTS

In total 50 placentas were studied: 25 were positive for submicroscopic infection and 25 were negative for Plasmodium infection. Expression of IL-4 and IL-10 was observed high in placental tissue of PM+, while IL-2 was high in peripheral blood of the same group. Expression of TNF and IFNγ in peripheral blood of the PM + group was high. Similarly, the apoptotic index and Fas expression were significantly high in PM+. However, FasL expression was observed low in PM + compared to PM-. Inflammation markers (HIF, VEGF) and hypoxia markers (COX-1, COX-2) were high in the PM + group.

CONCLUSION

During placental malaria expression of some pro-inflammatory cytokines is up-regulated and markers of hypoxia and tissue damage are increased in cases of submicroscopic infection.

Status of allele frequency and diversity of Plasmodium falciparum msp1, msp2 and glurp before implementation of artemisinin based combined therapy in Northwest Colombia

Introduction. msp1, msp2 and glurp allele frequency and diversity of P. falciparum in Northwest Colombia before introduction of artemisinin combined schemes has been explored by few authors and in relatively small number of samples from this highly endemic region. Objective. To evaluate the msp1, msp2, and glurp allele frequency and diversity of P. falciparum in two Colombian regions before use of artemisinin combined therapy. Methods. This study was part of a major antimalarial efficacy trial designed as a random clinical controlled study, in which 224 subjects were recruited. Region 2 of msp1 and msp2 (central region) were amplified by a nested PCR; glurp (region RII) was amplified by a semi-nested PCR. Results. For msp1, five genotypes were observed, representing K1, MAD20, and RO33 allelic families. All samples corresponded with a MAD20 150 bp allele. For msp2 (IC family), two alleles were detected and for glurp, eight were observed. A total 33 haplotypes were detected Conclusions. Analysis of glurp can be used to successfully genotype parasite populations in new studies in Colombia aimed at exploring Plasmodium spp.population dynamics. In addition, analysis of msp1 and msp2 can also be of value to compare with past studies, but not when the objective is to study parasites obtained from the same patient in a reduced period of time, for instance, during treatment efficacy studies.

Prevalence of gestational, placental and congenital malaria in north-west Colombia

BACKGROUND

The frequency of pregnancy-associated malaria is increasingly being documented in American countries. In Colombia, with higher frequency of Plasmodium vivax over Plasmodium falciparum infection, recent reports confirmed gestational malaria as a serious public health problem. Thick smear examination is the gold standard to diagnose malaria in endemic settings, but in recent years, molecular diagnostic methods have contributed to elucidate the dimension of the problem of gestational malaria. The study was aimed at exploring the prevalence of gestational, placental and congenital malaria in women who delivered at the local hospitals of north-west Colombia, between June 2008 and April 2011.

METHODS

A group of 129 parturient women was selected to explore the prevalence of gestational, placental and congenital malaria in a descriptive, prospective and transversal (prevalence) design. Diagnosis was based on the simultaneous application of two independent diagnostic tests: microscopy of thick blood smears and a polymerase chain reaction assay (PCR).

RESULTS

The prevalence of gestational malaria (thick smear /PCR) was 9.1%/14.0%; placental malaria was 3.3%/16.5% and congenital malaria was absent. A history of gestational malaria during the current pregnancy was significantly associated with gestational malaria at delivery. Plasmodium vivax caused 65% of cases of gestational malaria, whereas P. falciparum caused most cases of placental malaria.

CONCLUSIONS

Gestational and placental malaria are a serious problem in the region, but the risk of congenital malaria is low. A history of malaria during pregnancy may be a practical indicator of infection at delivery.

Molecular detection of malaria at delivery reveals a high frequency of submicroscopic infections and associated placental damage in pregnant women from northwest Colombia

Plasmodium infection in pregnancy causes substantial maternal and infant morbidity and mortality. In Colombia, both P. falciparum and P. vivax are endemic, but the impact of either species on pregnancy is largely unknown in this country. A cross-sectional study was carried out with 96 pregnant women who delivered at their local hospital. Maternal, placental, and cord blood were tested for malaria infection by microscopy and real-time quantitative polymerase chain reaction (qPCR). A high frequency of infection was detected by qPCR (45%). These infections had low concentrations of parasite DNA, and 79% were submicroscopic. Submicroscopic infections were associated with placental villitis and intervillitis. In conclusion, the overall frequency of Plasmodium infection at delivery in Colombia is much higher than previously reported. These data prompt a re-examination of the local epidemiology of malaria using molecular diagnostics to establish the clinical relevance of submicroscopic infections during pregnancy as well as their consequences for mothers and newborns.

Placental malaria in Colombia: histopathologic findings in Plasmodium vivax and P. falciparum infections

Studies on gestational malaria and placental malaria have been scarce in malaria-endemic areas of the Western Hemisphere. To describe the histopathology of placental malaria in Colombia, a longitudinal descriptive study was conducted. In this study, 179 placentas were studied by histologic analysis (112 with gestational malaria and 67 negative for malaria). Placental malaria was confirmed in 22.35%, 50.0% had previous infections, and 47.5% had acute infections. Typical malaria-associated changes were observed in 37%. The most common changes were villitis, intervillitis, deciduitis, increased fibrin deposition, increased syncytial knots, mononuclear (monocytes/macrophages and lymphocytes), polymorphonuclear cell infiltration, and trophozoites in fetal erythrocytes. No association was found between type of placental changes observed and histopathologic classification of placental malaria. The findings are consistent with those reported for placental malaria in other regions. Plasmodium vivax was the main parasite responsible for placental and gestational malaria, but its role in the pathogenesis of placental malaria was not conclusive.

Genotype comparison of Plasmodium vivax and Plasmodium falciparum clones from pregnant and non-pregnant populations in North-west Colombia

BACKGROUND

Placental malaria is the predominant pathology secondary to malaria in pregnancy, causing substantial maternal and infant morbidity and mortality in tropical areas. While it is clear that placental parasites are phenotypically different from those in the peripheral circulation, it is not known whether unique genotypes are associated specifically with placental infection or perhaps more generally with pregnancy. In this study, genetic analysis was performed on Plasmodium vivax and Plasmodium falciparum parasites isolated from peripheral and placental blood in pregnant women living in North-west Colombia, and compared with parasites causing acute malaria in non-pregnant populations.

METHODS

A total of 57 pregnant women at delivery with malaria infection confirmed by real-time PCR in peripheral or placental blood were included, as well as 50 pregnant women in antenatal care and 80 men or non-pregnant women with acute malaria confirmed by a positive thick smear for P. vivax or P. falciparum. Five molecular markers per species were genotyped by nested PCR and capillary electrophoresis. Genetic diversity and the fixation index FST per species and study group were calculated and compared.

RESULTS

Almost all infections at delivery were asymptomatic with significantly lower levels of infection compared with the groups with acute malaria. Expected heterozygosity for P. vivax molecular markers ranged from 0.765 to 0.928 and for P. falciparum markers ranged from 0.331 to 0.604. For P. vivax infections, the genetic diversity was similar amongst the four study groups and the fixation index from each pairwise comparison failed to show significant genetic differentiation. For P. falciparum, no genetic differentiation was observed between placental and peripheral parasites from the same woman at delivery, but the parasites isolated at delivery showed significant genetic differentiation compared with parasites isolated from subjects with acute malaria.

CONCLUSIONS

In North-west Colombia, P. vivax parasites have high genetic diversity that is equivalent in pregnant and non-pregnant populations as well as in symptomatic and asymptomatic infections. For P. falciparum, the overall genetic diversity is lower, with specific genotypes associated with asymptomatic infections at delivery.

Relationship between Duffy blood groups genotypes and malaria infection in different ethnic groups of Choco- Colombia

Background: The negative homozygous condition for the Duffy blood group (Fy-/Fy-) confers natural resistance to Plasmo­dium vivax infection. In this direction, studies carried out in Colombia are scarce Objective: To describe the relationship between Duffy genotypes in three ethnic communities in La Italia (Chocó) and malaria infection. Methodology: a descriptive, cross-sectional study in symptomatic and asymptomatic malaria subjects. Sample size : Afro American, 73; Amerindian (Emberá), 74 and Mestizo, 171. Presence of Plasmodium infection was assessed by thick smear and the status of the Duffy gene by PCR and RFLP in order to identify the substitutions T-46C y A131G which origin the genotypes T/T, T/C , C/C y G/G, G/A, A/A. Results: Infection by Plasmodium was detected in 17% with 62% due to P. falciparum and 27% to P. vivax. Duffy genotypes were significantly associated to ethnicity (p= 0,003). Individuals with the C/C, A/A diplotype were exclusively infected by P. falciparum, whereas other diplotypes were infected with either species. In the Amerindian and Mestizo populations, the frequency of the T-46 allele was 0,90-1,00, among Afrocolombians this was 0,50, equal to the C allele and with absence of heterozygous At locus 131, the highest frequency of the G allele was 0,30 in Amerindians and the A allele was 0,69 in Afro­colombians. Conclusions: In the Amerindian and mestizo populations studied, a predominance of the allele T-46 (FY+) was observed, but P. vivax was not the most common. Infection by P. vivax was out ruled in all FY- individuals.

Relationship between genotypes of the Duffy blood groups and malarial infection in different ethnic groups of Choco, Colombia

INTRODUCTION

The negative homozygous condition for the Duffy blood group (Fy-/Fy-) confers natural resistance to Plasmodium vivax infection. Studies carried out in pursuing this direction in Colombia are scarce.

OBJECTIVE

To describe the relationship between Duffy genotypes in three ethnic communities of La Italia (Chocó) and malarial infection.

METHODS

This is a descriptive, cross-sectional study in symptomatic and asymptomatic subjects with malaria.

SAMPLE SIZE

Afro-Colombians 73; Amerindian (Emberá) 74, and Mestizo, 171. The presence of Plasmodium infection was assessed by thick smear and the status of the Duffy gene was studied by PCR and RFLP to help identify changes to T-46C and A131G which originate the genotypes T/T, T/C , C/C and G/G, G/A, A/A.

RESULTS

Infection by Plasmodium was detected in 17% of cases with 62% due to P. falciparum and 27% due to P. vivax. Duffy genotypes were significantly associated with ethnicity (p= 0.003). Individuals with the C/C, A/A diplotypes were exclusively infected by P. falciparum, whereas the other diplotypes were infected with either of the species. In the Amerindian and Mestizo populations, the frequency of the T-46 allele was 0.90-1.00, among Afro-Colombians this was 0.50, the same as with the C allele and with an absence of heterozygous. At locus 131, the maximum frequency of the G allele was 0.30 in Amerindians and the maximum of the A allele was 0.69 in Afro-Colombians.

CONCLUSIONS

In the Amerindian and mestizo populations studied, there was a predominance of the allele T-46 (FY+) but this was not observed with the P. vivax infection. P. vivax was ruled out in all FY- individuals.

High IFN-gamma and TNF production by peripheral NK cells of Colombian patients with different clinical presentation of Plasmodium falciparum

BACKGROUND

In Colombia, Plasmodium falciparum infection rarely results in severe disease or mortality compared to infections in African populations. During natural infection NK cells exhibit a cytolytic effect and regulate dendritic cells, macrophages, neutrophils as well as affect antigen specific T and B cell responses. To characterize the NK cells in P. falciparum infected patients of a highly endemic region of Colombia, the degree of NK proliferation and production of IFN gamma and TNF production in these cells were explored.

METHODS

Seventeen patients with acute and three with severe P. falciparum malaria patients from the Northwest region of the country were recruited in the study. In addition, 20 healthy controls were included: 10 from Medellin (no-transmission area) and 10 from the Uraba region (a malaria endemic area). Immunophenotypic analysis of peripheral mononuclear cells was performed by FACS to detect total number of NK cells, subtypes and intracellular IFNγ and TNF production by NK cells in the different patient groups.

RESULTS

The total mean CD56(+)/CD3(-) NK cell proportions in acute and severe malaria subjects were 9.14% (7.15%CD56(dim), 2.01%CD56(bright)) and 19.62% (16.05%CD56(dim), 3.58%CD56(bright)), respectively, in contrast to healthy controls from endemic (total mean CD56(+)/CD3(-)1.2%) and non-endemic area (total mean CD56(+)/CD3(-) 0.67%). Analysis of basal IFNγ and TNF levels confirmed the CD56(bright) NK population as the main cytokine producer (p < 0.0001) in the groups affected with malaria, with the CD56(dim) NK cell exhibiting the highest potential of TNF production after stimulus in the acute malaria group.

CONCLUSIONS

The results confirm the important role of not only CD56(bright) but also of CD56(dim) NK cell populations as producers of the two cytokines in malaria patients in Colombia.

Multiple independent introductions of Plasmodium falciparum in South America

The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence--archeological and genetic--suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade.

Real-time PCR detection of Plasmodium directly from whole blood and filter paper samples

Background

Real-time PCR is a sensitive and specific method for the analysis of Plasmodium DNA. However, prior purification of genomic DNA from blood is necessary since PCR inhibitors and quenching of fluorophores from blood prevent efficient amplification and detection of PCR products.

Methods

Reagents designed to specifically overcome PCR inhibition and quenching of fluorescence were evaluated for real-time PCR amplification of Plasmodium DNA directly from blood. Whole blood from clinical samples and dried blood spots collected in the field in Colombia were tested.

Results

Amplification and fluorescence detection by real-time PCR were optimal with 40× SYBR^® Green dye and 5% blood volume in the PCR reaction. Plasmodium DNA was detected directly from both whole blood and dried blood spots from clinical samples. The sensitivity and specificity ranged from 93-100% compared with PCR performed on purified Plasmodium DNA.

Conclusions

The methodology described facilitates high-throughput testing of blood samples collected in the field by fluorescence-based real-time PCR. This method can be applied to a broad range of clinical studies with the advantages of immediate sample testing, lower experimental costs and time-savings.

Diagnosis of gestational, congenital, and placental malaria in Colombia: comparison of the efficacy of microscopy, nested polymerase chain reaction, and histopathology

The technical capability of different methods to diagnose Plasmodium in maternal peripheral blood, placenta, and umbilical cord blood has not been assessed in Colombia and seldom explored in other malaria-endemic regions. We designed a study to compare the technical and the operational-economical performances of light microscopy (LM), nested polymerase chain reaction (nPCR), and histopathology (HP). In maternal blood, LM had 41% sensitivity and 100% specificity and in placental blood, 35% and 100%, respectively, compared with nPCR. In placental tissue, LM had 33% sensitivity and 95% specificity; and nPCR 47% and 77%, respectively; compared with HP. Light microscopy had the best operational-economical qualification. We concluded that nPCR and HP performed better compared with LM, but field implementation of these two techniques remains a problem. Therefore, LM is recommended as the gold standard for diagnosis of gestational malaria and placental blood infection in the field.

High genetic polymorphism of relapsing P. vivax isolates in northwest Colombia

Genetic diversity of Plasmodium populations has been more extensively documented in Colombia for Plasmodium falciparum than for Plasmodium vivax. Recently, highly variable microsatellite markers have been described and used in population-level studies of genetic variation of P. vivax throughout the world. We applied this approach to understand the genetic structure of P. vivax populations and to identify recurrence-associated haplotypes. In this, three microsatellite markers of P. vivax were amplified and the combined size of the fragments was used to establish genotypes. Patients from an ongoing treatment efficacy trial who were kept either in endemic or non-endemic regions in the northwest of Colombia were included in the study. In total 58 paired clinical isolates, were amplified. A total of 54 haplotypes were observed among the two regions. Some haplotypes were exclusive to the endemic region where the highest degree of polymorphism was detected. In addition, we confirmed the different genotypes of recurrent-relapsing and primary infection isolates suggesting the activation of heterologous hypnozoite populations. We conclude that analysis of the three microsatellites is a valuable tool to establish the genetic characteristics of P. vivax populations in Colombia.

[Effect of submicroscopic or polyclonal Plasmodium falciparum infection on mother and gestation product: systematic review]

BACKGROUND

Malaria in pregnancy causes substantial maternal and infant morbidity-mortality, even at submicroscopic parasite levels. In addition, the presence of polyclonal infections secondary to high parasite genetic diversity is a common finding.

OBJECTIVES

To determine the frequency of submicroscopic and/or polyclonal plasmodial infection during pregnancy and to establish their impact on clinical presentation, immunity acquisition, and consequences on mother and gestation product.

METHODS

A search on Medline was performed using key words (MeSH): pregnancy, malaria, PCR, microscopy, genotype, and clones. Studies on plasmodial infection diagnosed by microscopy and PCR were selected.

RESULTS

A total of 16 studies were included, all carried out in Africa. The weighted mean (WM) of submicroscopic infection was 36%. According to type of infection (microscopic, submicroscopic or negative), the WM of maternal anemia and low birth weight (LBW) were 51%, 42%, 33%, and 19%, 16%, 11%, respectively. Risks (OR), using the negative group as reference, were: a) for maternal anemia 2.12 in microscopic infection and 1.48 in submicroscopic; b) for LBW 1.89 in microscopic and 1.56 in submicroscopic infection. The WM of polyclonal infection was 75% and the mean number of clones by sample was three.

CONCLUSIONS

Submicroscopic and polyclonal P. falciparum infections during pregnancy are very common, but have been little studied and their impact must be assessed in each specific region because they depend on malaria transmission intensity and stability, maternal age and parity, among other variables, which are influenced by environmental and socio-economic conditions of each region.

Acquired antibody responses against Plasmodium vivax infection vary with host genotype for duffy antigen receptor for chemokines (DARC)

Background

Polymorphism of the Duffy Antigen Receptor for Chemokines (DARC) is associated with susceptibility to and the severity of Plasmodium vivax malaria in humans. P. vivax uses DARC to invade erythrocytes. Individuals lacking DARC are ‘resistant’ to P. vivax erythrocytic infection. However, susceptibility to P. vivax in DARC+ individuals is reported to vary between specific DARC genotypes. We hypothesized that the natural acquisition of antibodies to P. vivax blood stages may vary with the host genotype and the level of DARC expression. Furthermore, high parasitemia has been reported to effect the acquisition of immunity against pre-erythrocytic parasites. We investigated the correlation between host DARC genotypes and the frequency and magnitude of antibodies against P. vivax erythrocytic stage antigens.

Methodology/Findings

We assessed the frequencies and magnitudes of antibody responses against P. vivax and P. falciparum sporozoite and erythrocytic antigens in Colombian donors from malaria-endemic regions. The frequency and level of naturally-acquired antibodies against the P. vivax erythrocytic antigens merozoite surface protein 1 (PvMSP1) and Duffy binding protein (PvDBP) varied with the host DARC genotypes. Donors with one negative allele (FY*B/FY*Bnull and FY*A/FY*Bnull) were more likely to have anti-PvMSP1 and anti-PvDBP antibodies than those with two positive alleles (FY*B/FY*B and FY*A/FY*B). The lower IgG3 and IgG1 components of the total IgG response may account for the decreased responses to P. vivax erythrocytic antigens with FY*A/FY*B and FY*B/FY*B genotypes. No such association was detected with P. falciparum erythrocytic antigens, which does not use DARC for erythrocyte invasion.

Conclusion/Significance

Individuals with higher DARC expression, which is associated with higher susceptibility to P. vivax infection, exhibited low frequencies and magnitudes of P. vivax blood-stage specific antibody responses. This may indicate that one of the primary mechanisms by which P. vivax evades host immunity is through DARC indirectly down-regulating humoral responses against erythrocytic invasion and development.

Prevention of Plasmodium vivax malaria recurrence: efficacy of the standard total dose of primaquine administered over 3 days

BACKGROUND

The standard total dose (STD) of primaquine to prevent Plasmodium vivax recurrence is 0.25mg/kg day administered over 14 days (STD-14). We evaluated, in an endemic zone of Colombia, the anti-recurrence efficacy of the STD dose administered over 3 and 14 days, and of sub-STD dose administered over 3 days (71%STD-3, 50%STD-3).

METHODS

A controlled clinical trial was carried out with 188 subjects allocated into one of four treatment groups: STD-14, STD-3, 71%STD-3, 50%STD-3.

RESULTS

Recurrences during the 120 days of follow-up were 15% in STD-14, and 57% in STD-3. Treatment with 71%STD-3 and 50%STD-3 resulted in recurrence in >48% subjects within 120 days after the primary episode. High daily doses (1.17 mg/kg day) were well tolerated.

CONCLUSIONS

(a) The standard dose and regimen (STD-14) of primaquine to prevent P. vivax relapse is recommended. The administration of the same dose over 3 days (STD-3) should be avoided; (b) doses lower than the STD doses administered over 3 days are ineffective in preventing relapse.

Clinical pathways as a healthcare tool: design, implementation and assessment of a clinical pathway for lower-extremity deep venous thrombosis

OBJECTIVE

To design, implement and assess a clinical pathway for lower-extremity deep venous thrombosis, and to compare the length of hospital stay in two different periods.

DESIGN

Development of the care pathway by a multidisciplinary team, followed by a controlled intervention study to compare two non-concomitant cohorts of patients corresponding to the years 2002 (before the implementation of the critical pathway) and 2004 (year of the implementation).

SETTING

Academic tertiary care hospital.

PARTICIPANTS

90 patients, 42 corresponding to the year 2004 and 48 to 2002, admitted to hospital with a diagnosis of lower-extremity deep venous thrombosis (DVT).

MAIN OUTCOME MEASURES

Length of hospital stay, hospitalisation costs and care indicators.

RESULTS

The mean length of hospital stay was 6.78 days in 2002 and 4.72 days in 2004. This means a reduction of 2.06 days (p<0.012). The reduction in the length of hospital stay in 2004 situates the hospital 1.98 days below the mean stay of our community (6.7 days) for the same diagnosis and year. The impact of the clinical pathway was assessed using the following indicators: implementation indicator 92.2%, compliance indicator 65%, adverse events indicator 2.5% and satisfaction indicator 67%. In comparison with costs incurred in year 2002, implementation of the clinical pathway resulted in a saving of euro427.33 per patient and a total saving of euro17,093.20.

CONCLUSIONS

The implementation of a lower-extremity DVT clinical pathway in our institution has help to reduce hospitalisation costs, due to a decreased length of hospital stay.

Assessment of the origins and spread of putative resistance-conferring mutations in Plasmodium vivax dihydropteroate synthase

Infection with Plasmodium vivax is usually treated with chloroquine, but parasites are often exposed inadvertently to sulfadoxine-pyrimethamine. To infer patterns of selection and spread of resistant parasites in natural populations, we determined haplotypes of P. vivax dihydropteroate synthase ( dhps ) alleles that could confer resistance to sulfadoxine. We amplified the P. vivax pyrophosphokinase ( pppk )- dhps region and its flanking intergenic regions from 92 contemporary global isolates. Introns and exons of pppk-dhps were highly polymorphic, as were the flanking intergenic regions. Eighteen haplotypes were associated with wild-type alleles, but several different putatively sulfadoxine-resistant alleles have arisen in areas of intensive sulfadoxine-pyrimethamine use. Even when they encoded changes to the same amino acid, these mutant alleles were associated with multiple different haplotypes. Two main conclusions can be drawn from these data. First, dhps alleles resistant to sulfadoxine have arisen multiple times under drug pressure. Second, there has been convergent evolution of a variety of alleles that could confer resistance to sulfa drugs.

Respuesta terapéutica a mefloquina, estado nutricional y variantes alélicas del gen CYP3A4 en pacientes con malaria falciparum no complicada; Antioquia (Colombia)

Introducción: hay poca información sobre las relaciones entre la falla de la terapia antimalárica y algunos factores del hospedero (estado nutricional, fenotipo y genotipo del citocromo CYP450 que metaboliza el medicamento antipalúdico). Objetivo: explorar si la falla terapéutica de la mefloquina dada a pacientes con malaria falciparum no complicada se puede explicar por la influencia del estado nutricional del enfermo y del fenotipo y genotipo de su citocromo CYP3A4. Materiales y métodos: estudio de casos y controles no pareado. Pacientes: hombres y mujeres adultos, de Turbo y El Bagre (Antioquia, Colombia). Resultados: se evaluó la respuesta terapéutica en 46 enfermos; hubo solo tres fallas (6,5%); por la muy baja ocurrencia de falla terapéutica (n = 3/46), los resultados se presentan en forma descriptiva para los 46 pacientes. La relación dextrometorfano/3metoximorfinano fue 0,39 (mediana); 20% fueron metabolizadores lentos. Las concentraciones sanguíneas medianas de mefloquina a las 24 horas (C24h) y al día 14 (Cd14) fueron 1.363 + 397 ng/mL y 978 + 106 ng/mL, respectivamente. Los 46 pacientes presentaron el alelo CYP3A4*2 (silvestre). Conclusión: no se pudo evaluar con profundidad la relación entre la respuesta a la terapia antimalárica, por una parte y, por otra, la actividad del CYP450 y el estado nutricional, pero hubo hallazgos que justifican la evaluación y control de las características del hospedero en estudios posteriores de farmacocinética antimalárica.

Methemoglobinemia and adverse events in Plasmodium vivax malaria patients associated with high doses of primaquine treatment

Primaquine (PQ) is recommended to prevent relapses in patients with Plasmodium vivax malaria infection. However, treatment with PQ causes methemoglobinemia. In this study, we measured the methemoglobin (MetHB) levels in three groups of subjects who received PQ treatment at 0.58, 0.83, or 1.17 mg/kg/d. A total of 112 subjects were studied. MetHB levels were detected at > or = 4% in 46-50% 1 day after PQ treatment in all three groups and 4-9% of subjects had MetHB levels > or = 4% 15 days after treatment. Only subjects receiving the highest doses of PQ had mild and brief adverse events, and 17% of them were associated with treatment. We conclude that when PQ is administered under certain conditions (i.e., normal glucose-6-phosphate dehydrogenase activity, in non-pregnant subjects and with a light meal), daily doses as high as 1.17 mg/kg do not represent a serious risk of high MetHB levels to patients.

Plasmodium falciparum: high frequency of pfcrt point mutations and emergence of new mutant haplotypes in Colombia

INTRODUCTION

Studies on the molecular epidemiology of antimalarial resistance constitute a useful tool to understand the events underlying treatment failure and resistance in falciparum malaria in Colombia. Several authors have reported on the efficacy of some molecular markers to predict drug resistance in Plasmodium falciparum. The P. falciparum pfcrt gene has been widely characterized in this context.

OBJECTIVE

The frequency of pfcrt gene mutations in P. falciparum were associated with treatment failure to the antimalarials chloroquine, mefloquine, amodiaquine and sulfadoxine/pyrimethamine.

MATERIALS AND METHODS

A representative sample of 172 patients with non-complicated falciparum malaria was selected from two highly malaria-endemic areas of northeastern Colombia, the Turbo and Bajo Cauca regions. These patients were assessed for treatment response together with the status of codons 72, 74, 75 and 76 in the pfcrt gene using a PCR-RFLP approach.

RESULTS

A high frequency of treatment failure to chloroquine (82%) and to amodiaquine (29%) was confirmed, whereas mefloquine and combined therapy remained effective. The presence of the T76 mutation in pfcrt was confirmed in all samples. The most common haplotype was CMNT (67%).

CONCLUSIONS

No significant association was confirmed between specific haplotypes and the treatment response in any of the treatment groups. Two haplotypes, SMET and SMNT, were reported for the first time in Colombia. Twelve percent of the samples carried both mixed mutant and wild-type alleles.

[Renal cell carcinoma presenting as paraneoplastic neurological dysfunction]

INTRODUCTION

Malignant tumors sometimes initiate as paraneoplastic syndromes even years before the most common symptoms appear. These first manifestations could be the key for the diagnosis of "occult" malignancy.

METHODS

We report the case of a 66 year old man with a renal cell carcinoma. The first symptom was a paraneoplastic cerebellar degeneration appeared 6 years before the first urologic manifestations.

CONCLUSIONS

A progressive cerebellar syndrome could be the first manifestation of a renal cell carcinoma, even years before the first urologic symptoms. We must suspect an occult neoplasia in such patients.

Multiple origins of resistance-conferring mutations in Plasmodium vivax dihydrofolate reductase

Background

In order to maximize the useful therapeutic life of antimalarial drugs, it is crucial to understand the mechanisms by which parasites resistant to antimalarial drugs are selected and spread in natural populations. Recent work has demonstrated that pyrimethamine-resistance conferring mutations in Plasmodium falciparum dihydrofolate reductase (dhfr) have arisen rarely de novo, but spread widely in Asia and Africa. The origin and spread of mutations in Plasmodium vivax dhfr were assessed by constructing haplotypes based on sequencing dhfr and its flanking regions.

Methods

The P. vivax dhfr coding region, 792 bp upstream and 683 bp downstream were amplified and sequenced from 137 contemporary patient isolates from Colombia, India, Indonesia, Papua New Guinea, Sri Lanka, Thailand, and Vanuatu. A repeat motif located 2.6 kb upstream of dhfr was also sequenced from 75 of 137 patient isolates, and mutational relationships among the haplotypes were visualized using the programme Network.

Results

Synonymous and non-synonymous single nucleotide polymorphisms (SNPs) within the dhfr coding region were identified, as was the well-documented in-frame insertion/deletion (indel). SNPs were also identified upstream and downstream of dhfr, with an indel and a highly polymorphic repeat region identified upstream of dhfr. The regions flanking dhfr were highly variable. The double mutant (58R/117N) dhfr allele has evolved from several origins, because the 58R is encoded by at least 3 different codons. The triple (58R/61M/117T) and quadruple (57L/61M/117T/173F, 57I/58R/61M/117T and 57L/58R/61M/117T) mutant alleles had at least three independent origins in Thailand, Indonesia, and Papua New Guinea/Vanuatu.

Conclusion

It was found that the P. vivax dhfr coding region and its flanking intergenic regions are highly polymorphic and that mutations in P. vivax dhfr that confer antifolate resistance have arisen several times in the Asian region. This contrasts sharply with the selective sweep of rare antifolate resistant alleles observed in the P. falciparum populations in Asia and Africa. The finding of multiple origins of resistance-conferring mutations has important implications for drug policy.

[Polymorphisms of the pfmdr1 gene in field samples of Plasmodium falciparum and their association with therapeutic response to antimalarial drugs and severe malaria in Colombia]

INTRODUCTION

The pfmdr1 gene of Plasmodium falciparum has been described as a gene conferring resistance to several antimalarial drugs. In particular, polymorphisms on specific codons have been associated with resistance and treatment failure with cloroquine, amodiaquine and mefloquine. However, the role of these polymorphisms in treatment response to antimalarials remains unexplored in Colombia. Furthermore, the relationship of these polymorphisms to severe malaria is unknown.

OBJECTIVE

This work studied the association of the Asn 86Tyr and Asp1246Tyr pfmdr1 polymorphisms with response to cloroquine, amodiaquine and mefloquine treatment in three municipalities of Antioquia, and severe malaria cases from the municipality Tumaco.

MATERIALS AND METHODS

The polymorphisms were assessed by nucleic acid amplification followed by restriction length polymorphism analysis.

RESULTS

The wild-type codon Asn 86 was detected in 97% of the clinical samples from the treatment response study. No association was detected between this polymorphism and treatment failure to the three antimalarials administered. The 1246Tyr polymorphism was detected with a higher frequency in the samples from Antioquia 92% (130/141) than in those from Tumaco 22% (20/89). However, again, no association was found between the presence of a specific polymorphism and the presence of severe malaria in the municipality of Tumaco.

CONCLUSIONS

The 86Tyr and 1246Tyr polymorphisms of the pfmdr1 gene are not useful as predictors of treatment failure or severe malaria in the municipalities studied. In addition, we report for the first time, the presence of the mutant codon 86Tyr in field samples in South America.

Efficacy of three chloroquine-primaquine regimens for treatment of Plasmodium vivax malaria in Colombia

Plasmodium vivax malaria is an important cause of morbidity in Central and South America. In Colombia, this is the most prevalent malaria infection, representing 75% of the reported cases. To define the efficacy of the chloroquine and primaquine regimen to eliminate hypnozoites and prevent relapses, we conducted a random controlled clinical trial of three primaquine regimens in an open-label study. We evaluated the anti-relapse efficacy of total primaquine doses of 45, 105, and 210 mg administered at a dosage of 15 mg/day in 210 adults with P. vivax infection from the northwestern region of Colombia. Cure rates for blood-stage P. vivax malaria by day 28 of follow-up were 100% in all groups. Post-treatment reappearance of parasitemia during the six months of follow-up was 45%, 36.6% and 17.6%, respectively, for each group. When compared with other groups, administration of 210 mg was a significant protection factor for reappearance of parasitemia in a malaria-endemic area.

Antibody response to Plasmodium vivax antigens in Fy-negative individuals from the Colombian Pacific coast

The Duffy antigen (Fy) is necessary for Plasmodium vivax invasion of human erythrocytes. Some populations have a highly prevalent Fy-negative phenotype; such persons are naturally protected from P. vivax blood infection but are expected to completely support the P. vivax pre-erythrocytic cycle, representing a valuable model for studying the immune response during these parasitic stages. We typed 214 individuals, mostly Afro-Colombians, from a P. vivax-endemic area for Fy expression and determined the antibody response to P. vivax pre-erythrocytic (sporozoites and CS) and blood-stage antigens (blood forms, P. vivax merozoite surface protein 1, and P. vivax Duffy binding protein [PvDBP]). Antibody titers to P. vivax circumsporozoite protein, P11, and N-terminal peptides and the number of responders were similar in Fy-negative and Fy-positive individuals. The number of responders to sporozoites, blood forms, and PvDBP were different between these groups. Thus, Fy-negative individuals from malaria-endemic areas can be used to study the immune response to the P. vivax liver phase without interference of the erythrocytic cycle.