Exploring the genetic diversity pattern of PvEBP/DBP2: A promising candidate for an effective Plasmodium vivax vaccine.

Malaria remains a public health challenge. Since many control strategies have proven ineffective in eradicating this disease, new strategies are required, among which the design of a multivalent vaccine stands out. However, the effectiveness of this strategy has been hindered, among other reasons, by the genetic diversity observed in parasite antigens. In Plasmodium vivax, the Erythrocyte Binding Protein (PvEBP, also known as DBP2) is an alternate ligand to Duffy Binding Protein (DBP); given its structural resemblance to DBP, EBP/DBP2 is proposed as a promising antigen for inclusion in vaccine design. However, the extent of genetic diversity within the locus encoding this protein has not been comprehensively assessed. Thus, this study aimed to characterize the genetic diversity of the locus encoding the P. vivax EBP/DBP2 protein and to determine the evolutionary mechanisms modulating this diversity. Several intrapopulation genetic variation parameters were estimated using 36 gene sequences of PvEBP/DBP2 from Colombian P. vivax clinical isolates and 186 sequences available in databases. The study then evaluated the worldwide genetic structure and the evolutionary forces that may influence the observed patterns of genetic variation. It was found that the PvEBP/DBP2 gene exhibits one of the lowest levels of genetic diversity compared to other vaccine-candidate antigens. Four major haplotypes were shared worldwide. Analysis of the protein's 3D structure and epitope prediction identified five regions with potential antigenic properties. The results suggest that the PvEBP/DBP2 protein possesses ideal characteristics to be considered when designing a multivalent effective antimalarial vaccine against P. vivax.

Evaluating the genetic diversity of the Plasmodium vivax siap2 locus: A promising candidate for an effective malaria vaccine?

Malaria is the deadliest parasitic disease in the world. Traditional control measures have become less effective; hence, there is a need to explore alternative strategies, such as antimalarial vaccines. However, designing an anti-Plasmodium vivax vaccine is considered a challenge due to the complex parasite biology and the antigens' high genetic diversity. Recently, the sporozoite invasion-associated protein 2 (SIAP2) has been suggested as a potential antigen to be considered in vaccine design due to its significance during hepatocyte invasion. However, its use may be limited by the incomplete understanding of gene/protein diversity. Here, the genetic diversity of pvsiap2 using P. vivax DNA samples from Colombia was assessed. Through PCR amplification and sequencing, we compared the Colombian sequences with available worldwide sequences, revealing that pvsiap2 displays low genetic diversity. Molecular evolutionary analyses showed that pvsiap2 appears to be influenced by directional selection. Moreover, the haplotypes found differ by a few mutational steps and several of them were shared between different geographical areas. On the other hand, several conserved regions within PvSIAP2 were predicted as potential B-cell or T-cell epitopes. Considering these characteristics and its role in hepatocyte invasion, the PvSIAP2 protein emerges as a promising antigen to be considered in a multi-antigen-multi-stage (multivalent) fully effective vaccine against P. vivax malaria.

Antigen Discovery in Circulating Extracellular Vesicles From Plasmodium vivax Patients.

Plasmodium vivax is the most widely distributed human malaria parasite with 7 million annual clinical cases and 2.5 billion people living under risk of infection. There is an urgent need to discover new antigens for vaccination as only two vaccine candidates are currently in clinical trials. Extracellular vesicles (EVs) are small membrane-bound vesicles involved in intercellular communication and initially described in reticulocytes, the host cell of P. vivax, as a selective disposal mechanism of the transferrin receptor (CD71) in the maturation of reticulocytes to erythrocytes. We have recently reported the proteomics identification of P. vivax proteins associated to circulating EVs in P. vivax patients using size exclusion chromatography followed by mass spectrometry (MS). Parasite proteins were detected in only two out of ten patients. To increase the MS signal, we have implemented the direct immuno-affinity capture (DIC) technique to enrich in EVs derived from CD71-expressing cells. Remarkably, we identified parasite proteins in all patients totaling 48 proteins and including several previously identified P. vivax vaccine candidate antigens (MSP1, MSP3, MSP7, MSP9, Serine-repeat antigen 1, and HSP70) as well as membrane, cytosolic and exported proteins. Notably, a member of the Plasmodium helical interspersed sub-telomeric (PHIST-c) family and a member of the Plasmodium exported proteins, were detected in five out of six analyzed patients. Humoral immune response analysis using sera from vivax patients confirmed the antigenicity of the PHIST-c protein. Collectively, we showed that enrichment of EVs by CD71-DIC from plasma of patients, allows a robust identification of P. vivax immunogenic proteins. This study represents a significant advance in identifying new antigens for vaccination against this human malaria parasite.

ASSESSMENT OF THE EFFICACY AND SAFETY OF CHLOROQUINE MONOTHERAPY FOR THE TREATMENT OF ACUTE UNCOMPLICATED GESTATIONAL MALARIA CAUSED BY P. VIVAX, CÓRDOBA, COLOMBIA, 2015-2017.

OBJECTIVE: To determine the efficacy of chloroquine monotherapy in Colombian pregnant women with acute uncomplicated malaria vivax (GMV). METHODS: Prospective cohort study in pregnant women who presented of their own accord between February 1, 2015 and December 31, 2017 to malaria or prenatal care centers in two Colombian towns and in whom the diagnosis of Plasmodium vivax was confirmed by means of blood spot test and and quantitative polymerase chain reaction (qPCR). Measured variables included sociodemographics, therapeutic failure (TF) and serious adverse events at 28 days and frequency of recurrence-relap (RR) over a follow-up period of 120 days. The WHO protocol was applied for the assessment of monotherapy with cloroquine (m-CQ) efficacy. RESULTS: Overall, 47 pregnant women were identified. During the 28-day follow-up period there were no losses, and there were two cases of TP (4.2%=2/47). Of the 45 women followed between 29 and 120 days, 11 were lost (24.4%=11/45) and there were 13 cases of RR, with an RR frequency ranging between 29 and 53 % depending on the type of analysis. CONCLUSIONS: Chloroquine is still highly effective as a cure of acute malaria vivax attack in GM in Colombia, and continues to be a good option for the treatment of acute phase GM. The RR frequency is high. Studies are required that evaluate therapeutic alternatives in MG. There is a pressing need for medications and/or procedures that can help reduce this very high risk.

TITULO: EVALUACIÓN DE LA EFICACIA Y SEGURIDAD DE LA MONOTERAPIA CON CLOROQUINA PARA TRATAR MALARIA GESTACIONAL AGUDA NO COMPLICADA DEBIDA P. VIVAX, CÓRDOBA, COLOMBIA, 2015-2017. OBJETIVO: determinar la eficacia y seguridad de la monoterapia con cloroquina en gestantes colombianas con ataque agudo no complicado de malaria vivax (MGV). METODOS: estudio de cohorte prospectiva en pacientes gestantes que consultaron de manera espontánea entre 1 febrero de 2015 y 31 diciembre de 2017 a los puestos de malaria o de control prenatal en dos poblaciones de Colombia, en quienes se confirmó el diagnóstico de Plasmodium vivax mediante gota gruesa y qPCR (quantitative polymerase chain reaction). Se midieron variables sociodemográficas, falla terapéutica (FT) y eventos adversos serios a los 28 días y la frecuencia de recurrencia-recaída (RR) con seguimiento de 120 días. Se aplicó el protocolo de la OMS para evaluar la eficacia de monoterapia con cloroquina (m-CQ). RESULTADOS: se captaron 47 gestantes; en el seguimiento de 28 días no hubo pérdidas y hubo 4,2 % (2/47) de FT. En el seguimiento de 45 mujeres entre los días 29 y 120 hubo 11 pérdidas (24,4 % = 11/45) y 13 RR con frecuencia que varió entre 29 y 53 % según el tipo de análisis. CONCLUSIONES: la cloroquina conserva muy alta eficacia para curar el ataque agudo de malaria vivax en malaria gestacional (MG) en Colombia, y continúa siendo una buena opción para el tratamiento de la fase aguda. La frecuencia de RR es alta. Se requieren estudios que evalúen alternativas terapéuticas en la MG. Hay urgente necesidad de disponer de medicamentos o procedimientos que reduzcan ese altísimo riesgo.

Assessment of the efficacy and safety of chloroquine monotherapy for the treatment of acute uncomplicated gestational malaria caused by P. vivax, Córdoba, Colombia, 2015-2017 / Evaluación de la eficacia y seguridad de la monoterapia con cloroquina para tratar malaria gestacional aguda no complicada debida p. vivax, córdoba, colombia, 2015-2017

RESUMEN Objetivo: determinar la eficacia y seguridad de la monoterapia con cloroquina en gestantes colombianas con ataque agudo no complicado de malaria vivax (MGV). Materiales y métodos: estudio de cohorte prospectiva en pacientes gestantes que consultaron de manera espontánea entre 1 febrero de 2015 y 31 diciembre de 2017 a los puestos de malaria o de control prenatal en dos poblaciones de Colombia, en quienes se confirmó el diagnóstico de Plasmodium vivax mediante gota gruesa y qPCR (quantitative polymerase chain reaction). Se midieron variables sociodemográficas, falla terapéutica (FT) y eventos adversos serios a los 28 días y la frecuencia de recurrencia-recaída (RR) con seguimiento de 120 días. Se aplicó el protocolo de la OMS para evaluar la eficacia de monoterapia con cloroquina (m-CQ). Resultados: se captaron 47 gestantes; en el seguimiento de 28 días no hubo pérdidas y hubo 4,2 % (2/47) de FT. En el seguimiento de 45 mujeres entre los días 29 y 120 hubo 11 pérdidas (24,4 % = 11/45) y 13 RR con frecuencia que varió entre 29 y 53 % según el tipo de análisis. Conclusiones: la cloroquina conserva muy alta eficacia para curar el ataque agudo de malaria vivax en malaria gestacional (MG) en Colombia, y continúa siendo una buena opción para el tratamiento de la fase aguda. La frecuencia de RR es alta. Se requieren estudios que evalúen alternativas terapéuticas en la MG. Hay urgente necesidad de disponer de medicamentos o procedimientos que reduzcan ese altísimo riesgo.

ABSTRACT Objective: To determine the efficacy of chloroquine monotherapy in Colombian pregnant women with acute uncomplicated malaria vivax Materials and methods: Prospective cohort study in pregnant women who presented of their own accord between February 1, 2015 and December 31, 2017 to malaria or prenatal care centers in two Colombian towns and in whom the diagnosis of Plasmodium vivax was confirmed by means of blood spot test and and quantitative polymerase chain reaction (qPCR). Measured variables included sociodemographics, therapeutic failure (TF) and serious adverse events at 28 days and frequency of recurrence-relap (RR) over a follow-up period of 120 days. The WHO protocol was applied for the assessment of monotherapy with cloroquine (m-CQ) efficacy. Results: Overall, 47 pregnant women were identified. During the 28-day follow-up period there were no losses, and there were two cases of TP (4.2%=2/47). Of the 45 women followed between 29 and 120 days, 11 were lost (24.4%=11/45) and there were 13 cases of RR, with an RR frequency ranging between 29 and 53 % depending on the type of analysis. Conclusions: Chloroquine is still highly effective as a cure of acute malaria vivax attack in GM in Colombia, and continues to be a good option for the treatment of acute phase GM. The RR frequency is high. Studies are required that evaluate therapeutic alternatives in MG. There is a pressing need for medications and/or procedures that can help reduce this very high risk.