Genetic polymorphism of merozoite surface protein 2 and prevalence of K76T pfcrt mutation in Plasmodium falciparum field isolates from Congolese children with asymptomatic infections

<p>Abstract</p> <p>Background</p> <p>In order to prepare the field site for future interventions, the prevalence of asymptomatic <it>Plasmodium falciparum </it>infection was evaluated in a cohort of children living in Brazzaville. <it>Plasmodium falciparum </it>merozoite surface protein 2 gene (<it>msp</it>2) was used to characterize the genetic diversity and the multiplicity of infection. The prevalence of mutant <it>P. falciparum </it>chloroquine resistance transporter (<it>pfcrt</it>) allele in isolates was also determined.</p> <p>Methods</p> <p>Between April and June 2010, 313 children below 10 years of age enrolled in the cohort for malaria surveillance were screened for <it>P. falciparum </it>infection using microscopy and polymerase chain reaction (PCR). The children were selected on the basis of being asymptomatic. <it>Plasmodium falciparum msp2 </it>gene was genotyped by allele-specific nested PCR and the <it>pfcrt </it>K76T mutation was detected using nested PCR followed by restriction endonuclease digestion.</p> <p>Results</p> <p>The prevalence of asymptomatic <it>P. falciparum </it>infections was 8.6% and 16% by microscopy and by PCR respectively. Allele typing of the <it>msp2 </it>gene detected 55% and 45% of 3D7 and FC27 allelic families respectively. The overall multiplicity of infections (MOI) was 1.3. A positive correlation between parasite density and multiplicity of infection was found. The prevalence of the mutant <it>pfcrt </it>allele (T76) in the isolates was 92%.</p> <p>Conclusion</p> <p>This is the first molecular characterization of <it>P. falciparum </it>field isolates in Congolese children, four years after changing the malaria treatment policy from chloroquine (CQ) to artemisinin-based combination therapy (ACT). The low prevalence of asymptomatic infections and MOI is discussed in the light of similar studies conducted in Central Africa.</p

Prevalence of non- Plasmodium falciparum species in southern districts of Brazzaville in The Republic of the Congo

Background: Although Plasmodium falciparum infection is largely documented and this parasite is the main target for malaria eradication, other Plasmodium species persist, and these require more attention in Africa. Information on the epidemiological situation of non-P. falciparum species infections is scarce in many countries, including in the Democratic Republic of the Congo (hereafter Republic of the Congo) where malaria is highly endemic. The aim of this study was to determine the prevalence and distribution of non-P. falciparum species infections in the region south of Brazzaville. Methods: A cross-sectional survey was conducted in volunteers living in rural and urban settings during the dry and rainy seasons in 2021. Socio-demographic and clinical parameters were recorded. Plasmodium infection in blood samples was detected by microscopic analysis and nested PCR (sub-microscopic analysis). Results: Of the 773 participants enrolled in the study, 93.7% were from the rural area, of whom 97% were afebrile. The prevalence of microscopic and sub-microscopic Plasmodium spp. infection was 31.2% and 63.7%, respectively. Microscopic Plasmodium malariae infection was found in 1.3% of participants, while sub-microscopic studies detected a prevalence of 14.9% for P. malariae and 5.3% for Plasmodium ovale. The rate of co-infection of P. malariae or P. ovale with P. falciparum was 8.3% and 2.6%, respectively. Higher rates of sub-microscopic infection were reported for the urban area without seasonal fluctuation. In contrast, non-P. falciparum species infection was more pronounced in the rural area, with the associated risk of the prevalence of sub-microscopic P. malariae infection increasing during the dry season. Conclusion: There is a need to include non-P. falciparum species in malaria control programs, surveillance measures and eradication strategies in the Republic of the Congo. Graphical Abstract

Sub-microscopic Plasmodium falciparum infections in matched peripheral, placental and umbilical cord blood samples from asymptomatic Congolese women at delivery

International audienceIn malaria-endemic areas, most pregnant women are susceptible to asymptomatic Plasmodium falciparum infections. We present here the results of a cross-sectional study conducted in Madibou, a southern district of Brazzaville in the Republic of Congo, between March 2014 and April 2015. The main aim was to characterize P. falciparum infections. Blood samples corresponding to peripheral, placental and cord from 370 asymptomatic malaria women at delivery were diagnosed for plasmodium infection by thick blood smears (microscopic infection). Sub-microscopic infection was detected by PCR, using the MSP-2 gene as marker. Microscopic infections were detected in peripheral, placental and cord blood samples with a prevalence of respectively 7.3% (27/370), 2.7% (10/370) and 0%. The negative samples were submitted to sub-microscopic detection, with respective prevalence of 25.4% (87/343), 16.7% (60/360) and 9.4% (35/370) (P < 0.001). We further investigated the genetic diversity of the parasite by characterizing MSP2 allelic families 3D7 (24 distinct alleles) and FC27 (20 distinct alleles). The total number of alleles for these two families were 31, 25 and 19 in peripheral, placental and cord samples respectively. The 3D7 MSP-2 was the predominant allelic family. The multiplicity of infections (MOI) in peripheral (mean 1.4 ± 0.01; range 1–4), placental (mean 1.2 ± 0.01; range 1–3) and cord samples (1.4 ± 0.01; range 1–3) were similar (P = 0.9) and are unaffected by age, gravidity or sulfadoxine-pyrimethamine. These results shown a high prevalence of sub-microscopic infection and a high genetic diversity of Plasmodium falciparum strains in Congo. Age, gravidity and doses of preventive treatment based on sulfadoxine-pyrimethamine do not interfere with the multiplicity of infections

Plasmodium falciparum infection in febrile Congolese children: prevalence of clinical malaria ten years after introduction of Artemisinin-combination therapies

dataset used in the paper

An update on glucose-6-phosphate dehydrogenase deficiency in children from Brazzaville, Republic of Congo

Abstract Background Malaria transmission-blocking anti-malarial drugs, such as primaquine, offers an effective strategy for reducing the incidence of falciparum malaria. However, this drug induces haemolytic anaemia among glucose-6-phosphate dehydrogenase (G6PD) deficient individuals. The distribution of G6PD deficiency in Brazzaville, Republic of Congo and the association of G6PD deficiency with haemoglobin levels and blood cell counts were investigated. Methods A total of 212 febrile children were recruited for this study. Plasmodium falciparum diagnosis was conducted by microscopy and nested PCR. Sanger sequencing was used to assess G6PD deficiency by detecting 202G>A (rs1050828) and 376A>G (rs1050829) single nucleotide polymorphisms. Results Two hundred and twelve children were successfully genotyped for G6PD variants. Overall, 13% (27/212) of the children were G6PD deficient and 25% (25/100) females were heterozygous (11 BA− and 14 A+A−). The remaining 160 children had a normal G6PD genotype. The mean red blood and mean platelet counts were significantly lower in hemizygous male (G6PD A−) participants than in normal male (G6PD A+ or B) participants (p < 0.05). Conclusion This study gives an update on G6PD deficiency among Congolese children. Understanding the distribution of G6PD deficiency in other geographical regions is recommended before primaquine is adopted in the malaria control programme

Cytochrome P450 CYP2B6*6 distribution among Congolese individuals with HIV, Tuberculosis and Malaria infection

Background: The cytochrome P450 CYP2B6*6 (CYP2B6 c.516G>T; rs3745274) is one of the genetic factors that alters the drug metabolism in antimalarial, antiretroviral and TB first-line drugs. In Central African populations, the distribution of the CYP2B6*6 variant is poorly documented. This study investigated the distribution of CYP2B6 c.516G>T variant among Congolese individuals. Methods: A total of 418 patients with HIV-1 mono-infection, HIV-1 and Tuberculosis coinfection and symptomatic P. falciparum malaria were genotyped for the CYP2B6 c.516G>T SNP using Restriction Fragment Length Polymorphism (RFLP). The allele frequencies and genotype distributions were determined. Results: The CYP2B6 c.516G>T was successfully analysed in 69% (288/418) of the study participants. Among the investigated individuals, the distribution of the major allele CYP2B6*G was 45% and the minor CYP2B6*T allele was 55%. Significant differences in genotype distribution were also observed among the studied individuals. The CYP2B6*GG (rapid metabolizer) genotype was observed in 17% (49/288) followed by CYP2B6*GT (intermediate metabolizer) 55% (159/288) and CYP2B6*TT (poor metabolizers) 28% (80/288). Conclusion: This study contributes to increasing understanding on population pharmacogenetics and may help policy makers regulate treatment guidelines in the Congolese population with a high burden of HIV, Malaria and TB. Keywords: CYP2B6, Cytochrome P 450, HIV, Malaria, Tuberculosis, Republic of Cong

Assessment of neutralizing antibody responses after natural SARS-CoV-2 infection and vaccination in congolese individuals

Abstract Background Assessing immune responses after vaccination is part of the evaluation package of vaccine effectiveness in the real world. Regarding SARS-CoV-2, neutralizing antibody levels has been shown to be a good indicator of antibody immune response boosting. So far, limited data have been reported from Africa including in Central Africa. The objective of this study was to provide data on anti-S1 spike total IgG and neutralizing antibodies in vaccinated and non-vaccinated including naturally infected Congolese population during B.1.214.1 and B.1.617.2 variant waves. Methods Recruited patients were divided into 4 groups: (1) Naturally infected by the B.1.214.1 variant on January 2021 and followed up until September 2021. These patients have been vaccinated at month 07 and then followed up for 2 months post vaccination; (2) Naturally infected by the B.1.617.2 variant from June 2021; (3) unvaccinated SARS-CoV-2 individuals with no history of prior SARS-CoV-2 infection; (4) fully vaccinated individuals with sinopharm/BBIP-CorV or Janssen/Ad26.COV2.S. SARS-CoV-2 was detected by qRT-PCR and sequenced using Next-Generation Sequencing. ELISA method was used for detecting IgG, and neutralizing Antibody against SARS-CoV-2 antigens using commercial neutralizing assay. Results Individuals infected by the B.1214.1 variant elicited consistently high IgG titers at 02, 03 and 06 months. Two months post vaccination with BBIP-CorV, participants showed a significant increase by × 2.5 fold (p < 0.0001) of total IgG and X1.5 fold for neutralizing antibody capacity. This study showed that natural infection with B1.617.2 (delta) variant was more immunogenic compared to those being infected with B1.214.2 variant. We found a significantly higher concentration in anti-SARS-CoV-2 IgG (p < 0.0002) and antibodies neutralization capacity (P < 0.0001) in fully vaccinated compared to unvaccinated participants. Two months post vaccination, individuals who received Janssen/Ad26.COV2.S presented higher (p = 0.01) total IgG to spike protein compared to BBIP-CorV. Conclusion Both natural infection and vaccination with BBIP-CorV and Janssen/Ad26.COV2.S induced antibody response in Congolese population. In addition, Janssen/Ad26.COV2.S was more immunogenic than Sinopharm/BBIP-CorV. There is a need to investigate the duration of these antibodies both in previously infected and naive vaccinated Congolese to allow public heath stakeholders to make evidence-based decision on vaccine schedule for the Congolese population

Epidemiological profile of multidrug-resistant and extensively drug-resistant Mycobacterium Tubrculosis among Congolese patients

Background: There is paucity of data on the prevalence and distribution of multidrug- Resistant-Tuberculosis (MDR-TB) in the Republic of Congo. Among the challenges resides the implementation of a robust TB resistance diagnostic program using molecular tools. In resource limited settings there is a need to gather data to enable prioritization of actions. The objective of this study was is to implement molecular tools as a best of diagnosing MDR and XDR-TB among presumptive tuberculosis patients referred to reference hospital of Makelekele in Brazzaville, Republic of the Congo. Methods: We have conducted a cross-sectional study, including a total of 92 presumptive pulmonary tuberculosis patients and who had never received treatment recruited at the reference hospital of Makelekele from October 2018 to October 2019. The socio-demographic and clinical data were collected as well as sputum samples. Rifampicin resistance was investigated using Xpert (Cepheid) and second-line TB drugs Susceptibility testing were performed by the Brucker HAIN Line Probe Assay (GenoType MTBDRsl VER 2.0 assay) method. Results: From the 92 recruited patients, 57 (62%) were found positive for the Mycobacterium tuberculosis complex. The prevalence of rifampicin-resistant tuberculosis (RR-TB) was 9.8% (9/92) and importantly 2.2% were pre-XDR/XDR. Conclusion: This study showed a high rate of rifampicin resistance and the presence of extensively drug-resistant tuberculosis in the study area in new patients. This study highlights the need for further studies of TB drug resistance in the country