Genetic diversity of vaccine candidate antigens in Plasmodium falciparum isolates from the Amazon basin of Peru

<p>Abstract</p> <p>Background</p> <p>Several of the intended <it>Plasmodium falciparum </it>vaccine candidate antigens are highly polymorphic and could render a vaccine ineffective if their antigenic sites were not represented in the vaccine. In this study, characterization of genetic variability was performed in major B and T-cell epitopes within vaccine candidate antigens in isolates of <it>P. falciparum </it>from Peru.</p> <p>Methods</p> <p>DNA sequencing analysis was completed on 139 isolates of <it>P. falciparum </it>collected from endemic areas of the Amazon basin in Loreto, Peru from years 1998 to 2006. Genetic diversity was determined in immunological important regions in circumsporozoite protein (CSP), merozoite surface protein-1 (MSP-1), apical membrane antigen-1 (AMA-1), liver stage antigen-1 (LSA-1) and thrombospondin-related anonymous protein (TRAP). Alleles identified by DNA sequencing were aligned with the vaccine strain 3D7 and DNA polymorphism analysis and FST study-year pairwise comparisons were done using the DnaSP software. Multilocus analysis (MLA) was performed and average of expected heterozygosity was calculated for each loci and haplotype over time.</p> <p>Results</p> <p>Three different alleles for CSP, seven for MSP-1 Block 2, one for MSP-1 Block 17, three for AMA-1 and for LSA-1 each and one for TRAP were identified. There were 24 different haplotypes in 125 infections with complete locus typing for each gene.</p> <p>Conclusion</p> <p>Characterization of the genetic diversity in <it>Plasmodium </it>isolates from the Amazon Region of Peru showed that <it>P. falciparum </it>T and B cell epitopes in these antigens have polymorphisms more similar to India than to Africa. These findings are helpful in the formulation of a vaccine considering restricted repertoire populations.</p

Genetic diversity and population structure of genes encoding vaccine candidate antigens of Plasmodium vivax

<p>Abstract</p> <p>Background</p> <p>A major concern in malaria vaccine development is genetic polymorphisms typically observed among <it>Plasmodium </it>isolates in different geographical areas across the world. Highly polymorphic regions have been observed in <it>Plasmodium falciparum </it>and <it>Plasmodium vivax </it>antigenic surface proteins such as Circumsporozoite protein (CSP), Duffy-binding protein (DBP), Merozoite surface protein-1 (MSP-1), Apical membrane antigen-1 (AMA-1) and Thrombospondin related anonymous protein (TRAP).</p> <p>Methods</p> <p>Genetic variability was assessed in important polymorphic regions of various vaccine candidate antigens in <it>P. vivax </it>among 106 isolates from the Amazon Region of Loreto, Peru. In addition, genetic diversity determined in Peruvian isolates was compared to population studies from various geographical locations worldwide.</p> <p>Results</p> <p>The structured diversity found in <it>P. vivax </it>populations did not show a geographic pattern and haplotypes from all gene candidates were distributed worldwide. In addition, evidence of balancing selection was found in polymorphic regions of the <it>trap, dbp </it>and <it>ama-1 </it>genes.</p> <p>Conclusions</p> <p>It is important to have a good representation of the haplotypes circulating worldwide when implementing a vaccine, regardless of the geographic region of deployment since selective pressure plays an important role in structuring antigen diversity.</p

Comparison of artemether-lumefantrine and chloroquine with and without primaquine for the treatment of Plasmodium vivax infection in Ethiopia: A randomized controlled trial

Background: Recent efforts in malaria control have resulted in great gains in reducing the burden of Plasmodium falciparum, but P. vivax has been more refractory. Its ability to form dormant liver stages confounds control and elimination efforts. To compare the efficacy and safety of primaquine regimens for radical cure, we undertook a randomized controlled trial in Ethiopia. Methods and findings: Patients with normal glucose-6-phosphate dehydrogenase status with symptomatic P. vivax mono-infection were enrolled and randomly assigned to receive either chloroquine (CQ) or artemether-lumefantrine (AL), alone or in combination with 14 d of semi-supervised primaquine (PQ) (3.5 mg/kg total). A total of 398 patients (n = 104 in the CQ arm, n = 100 in the AL arm, n = 102 in the CQ+PQ arm, and n = 92 in the AL+PQ arm) were followed for 1 y, and recurrent episodes were treated with the same treatment allocated at enrolment. The primary endpoints were the risk of P. vivax recurrence at day 28 and at day 42. The risk of recurrent P. vivax infection at day 28 was 4.0% (95% CI 1.5%–10.4%) after CQ treatment and 0% (95% CI 0%–4.0%) after CQ+PQ. The corresponding risks were 12.0% (95% CI 6.8%–20.6%) following AL alone and 2.3% (95% CI 0.6%–9.0%) following AL+PQ. On day 42, the risk was 18.7% (95% CI 12.2%–28.0%) after CQ, 1.2% (95% CI 0.2%–8.0%) after CQ+PQ, 29.9% (95% CI 21.6%–40.5%) after AL, and 5.9% (95% CI 2.4%–13.5%) after AL+PQ (overall p < 0.001). In those not prescribed PQ, the risk of recurrence by day 42 appeared greater following AL treatment than CQ treatment (HR = 1.8 [95% CI 1.0–3.2]; p = 0.059). At the end of follow-up, the incidence rate of P. vivax was 2.2 episodes/person-year for patients treated with CQ compared to 0.4 for patients treated with CQ+PQ (rate ratio: 5.1 [95% CI 2.9–9.1]; p < 0.001) and 2.3 episodes/person-year for AL compared to 0.5 for AL+PQ (rate ratio: 6.4 [95% CI 3.6–11.3]; p < 0.001). There was no difference in the occurrence of adverse events between treatment arms. The main limitations of the study were the early termination of the trial and the omission of haemoglobin measurement after day 42, resulting in an inability to estimate the cumulative risk of anaemia. Conclusions: Despite evidence of CQ-resistant P. vivax, the risk of recurrence in this study was greater following treatment with AL unless it was combined with a supervised course of PQ. PQ combined with either CQ or AL was well tolerated and reduced recurrence of vivax malaria by 5-fold at 1 y

Local population structure of <it>Plasmodium</it>: impact on malaria control and elimination

<p>Abstract</p> <p>Background</p> <p>Regardless of the growing interest in detecting population structures in malarial parasites, there have been limited discussions on how to use this concept in control programmes. In such context, the effects of the parasite population structures will depend on interventions’ spatial or temporal scales. This investigation explores the problem of identifying genetic markers, in this case microsatellites, to unveil <it>Plasmodium </it>genetic structures that could affect decisions in the context of elimination. The study was performed in a low-transmission area, which offers a good proxy to better understand problems associated with surveillance at the final stages of malaria elimination.</p> <p>Methods</p> <p><it>Plasmodium vivax</it> samples collected in Tumeremo, Venezuela, between March 2003 and November 2004 were analysed. Since <it>Plasmodium falciparum</it> also circulates in many low endemic areas, <it>P. falciparum</it> samples from the same locality and time period were included for comparison. <it>Plasmodium vivax</it> samples were assayed for an original set of 25 microsatellites and <it>P. falciparum</it> samples were assayed for 12 microsatellites.</p> <p>Results</p> <p>Not all microsatellite loci assayed offered reliable local data. A complex temporal-cluster dynamics is found in both <it>P. vivax </it>and <it>P. falciparum</it>. Such dynamics affect the numbers and the type of microsatellites required for identifying individual parasites or parasite clusters when performing cross-sectional studies. The minimum number of microsatellites required to differentiate circulating <it>P. vivax </it>clusters differs from the minimum number of hyper-variable microsatellites required to distinguish individuals within these clusters. Regardless the extended number of microsatellites used in <it>P. vivax</it>, it was not possible to separate all individual infections.</p> <p>Conclusions</p> <p>Molecular surveillance has great potential; however, it requires preliminary local studies in order to properly interpret the emerging patterns in the context of elimination. Clonal expansions and clusters turnovers need to be taken into account when using molecular markers. Those affect the number and type of microsatellite markers, as well as, the expected genetic patterns in the context of operational investigations. By considering the local dynamics, elimination programmes could cost-effectively use molecular markers. However, population level studies need to consider the local limitations of a given set of loci in terms of providing epidemiologically relevant information.</p

Caracterización molecular del dominio de la hélice del gen K13 de Plasmodium falciparum en muestras de comunidades nativas de Condorcanqui, Amazonas, Perú

Introduction: Resistance of Plasmodium falciparum to different antimalarial drugs is an obstacle to the elimination of the disease. The artemisinin resistant genotype of P. falciparum can be assessed by examining polymorphisms in the helix domain of the PfK13 gene. WHO recommends using these mutations as molecular markers to detect the presence of resistance to artemisinin in countries where P. falciparum malaria is endemic.Objective: Identify artemisinin resistance-related mutations present in the helix domain of the P. falciparum K13 gene.Materials and method: Through passive case detection (PCD), a total of 51 positive samples were collected by microscopy for Plasmodium, from six communities in the district of Río Santiago in Condorcanqui, Amazonas. Molecular species confirmation was performed by real-time PCR and the helix domain of the PfK13 gene was amplified and sequenced by capillary electrophoresis. The obtained sequences were compared with the wild type 3D7 reference strain.Results: A total of 51 positive samples were confirmed for P. falciparum from the communities of Ayambis, Chapiza, Palometa, Muchinguis, Alianza Progreso and Caterpiza. After alignment of the DNA sequences, it was determined that the samples did not present resistance-associated mutations in the K13 gene. Discussion: The results obtained are consistent with similar studies conducted in other South American countries, including Peru, so these data provide a baseline for molecular surveillance of artemisinin resistance in the Amazon region and reinforce the efficacy of artemisinin-based combination therapy in this area.Introducción. La resistencia de P. falciparum a diferentes fármacos antipalúdicos es un obstáculo para la eliminación de la enfermedad. El genotipo resistente de P. falciparum a la artemisinina se puede evaluar examinando polimorfismos en el dominio de la hélice del gen PfK13. La OMS recomienda utilizar estas mutaciones como marcadores moleculares para detectar la presencia de resistencia a la artemisinina en países donde la malaria por P. falciparum es endémica. Objetivo. Identificar mutaciones relacionadas a la resistencia de artemisinina presentes en el dominio de la hélice del gen K13 de P. falciparum.Materiales y métodos. Mediante la detección pasiva de casos (DPC) se colectó un total de 51 muestras positivas por microscopía para Plasmodium, provenientes de seis comunidades del distrito de Río Santiago en Condorcanqui, Amazonas. Se realizó la confirmación molecular de especie mediante PCR en tiempo real y el dominio de la hélice del gen PfK13 se amplificó y secuenció por electroforesis capilar. Las secuencias obtenidas se compararon con la secuencia de la cepa de referencia 3D7 de tipo salvaje.Resultados. Se confirmaron un total de 51 muestras positivas para P. falciparum, provenientes de las comunidades de Ayambis, Chapiza, Palometa, Muchinguis, Alianza Progreso y Caterpiza. Después del alineamiento de las secuencias de ADN, se determinó que las muestras no presentaron mutaciones asociadas a resistencia en el gen K13. Discusión. Los resultados obtenidos son consistentes con estudios similares realizados en otros países de América del Sur, incluyendo Perú, por lo que, estos datos proporcionan una línea base para la vigilancia molecular de resistencia a artemisinina en la región Amazonas y refuerzan la eficacia de la terapia combinada con artemisinina en esta área

Primer reporte de un brote de dengue en Balsas, Amazonas, Perú, durante 2021 y 2022: First report of a Dengue outbreak in Balsas, Amazonas, Peru, during 2021 and 2022.

Introduction: The increase in dengue cases in Amazonas is a risk to public health. In 2021, Balsas reported a dengue outbreak for the first time. Methodology: The population included patients who met the case definition between December 2021 and February 2022. Identification of serotypes will be reduced by multiplex qRT-PCR. Results: 72 patients were identified, of which 53 (74%) were confirmed by serology (Ag NS1). The predominant serotype was DENV-2 (94%), and 6% was DENV-1. Patients between 19 and 45 years old presented the highest percentage of cases (59%). The most frequent symptoms were fever, headache, myalgia and arthralgia; 23% presented severe abdominal pain. Conclusion: This was the first confirmed dengue outbreak in the Balsas district, with DENV-2 being the main cause of the outbreak, highlighting the need to improve surveillance in areas without autochthonous transmission of the disease.Introducción: El aumento de casos de dengue en Amazonas es un riesgo para la salud pública. En el 2021, Balsas reportó por primera vez un brote de dengue. Metodología: La población incluyó a pacientes que cumplían con la definición de caso entre diciembre 2021 y febrero 2022. La identificación de los serotipos se determinó mediante una qRT-PCR múltiplex. Resultados: Se identificaron 72 pacientes de los cuales 53 (74%) se confirmaron por serología (Ag NS1). El serotipo prevalente fue DENV-2 (94%), y el 6% fue DENV-1. Los pacientes de 19 a 45 años presentaron el mayor porcentaje de casos (59%). Los síntomas más frecuentes fueron cefalea, mialgias, fiebre y artralgias; el 23 % presentó dolor abdominal intenso. Conclusión: Este fue el primer brote de dengue confirmado en el distrito de Balsas, siendo DENV-2 el principal causante, destacando la necesidad de mejorar la vigilancia en zonas sin transmisión autóctona de la enfermedad