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

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.

SARS-CoV-2 B.1.214.1, B.1.214.2 and B.1.620 are predominant lineages between December 2020 and July 2021 in the Republic of Congo.

Background: : SARS-CoV-2 variants have been emerging and are shown to increase transmissibility, pathogenicity, and decreased vaccine efficacies. The objective of this study was to determine the distribution, prevalence, and dynamics of SARS-CoV-2 variants circulating in Brazzaville, the Republic of Congo (ROC). Methods: : Between December 2020 and July 2021, a total of n=600 oropharyngeal specimens collected in the community were tested for COVID-19. Of the samples tested, 317 (53%) were SARS-CoV-2 positive. All samples that had a threshold of Ct <30 (n=182) were sequenced by next-generation sequencing (NGS), and all complete sequenced genomes were submitted to GISAID; lineages were assigned using pangolin nomenclature and a phylogenetic tree was reconstructed. In addition, the global prevalence of the predominant lineages was analysed using data from GISAID and Outbreak databases. Results: : A total of 15 lineages circulated with B.1.214.2 (26%), B.1.214.1 (19%) and B.1.620 (18%) being predominant. The variants of concern (VOC) alpha (B.1.1.7) (6%) and for the first time in June delta (B.1.617.2) (4%) were observed. In addition, the B.1.214.1 lineage first reported from ROC was observed to be spreading locally and regionally. Phylogenetic analysis suggests that the B.1.620 variant (VUM) under observation may have originated from either Cameroon or the Central African Republic. SARS-CoV-2 lineages were heterogeneous, with the densely populated districts of Poto-Poto and Moungali likely the epicenter of spread. Conclusion: : Longitudinal monitoring and molecular surveillance across time and space are critical to understanding viral phylodynamics, which could have important implications for transmissibility and impact infection prevention and control measures.

Seroprevalence of anti-SARS-CoV-2 antibodies in a population living in Bomassa village, Republic of Congo.

Objectives: With limited data available from Central Africa, the aim of our study was to evaluate the anti-SARS-CoV-2 Ab prevalence in indigenous residents of Bomassa, a village located in the Sangha region in the Republic of Congo. Methods: Plasma and oropharyngeal swab samples were collected from 304 healthy adult individuals, randomly recruited in May 2021 before vaccine introduction in the area. In addition, 82 plasma samples from the same area in 2019 were included as controls for the investigation of cross-reactivity against other coronaviruses. The SARS-CoV-2 virus was detected by qRT-PCR and sequenced using next-generation sequencing. ELISA was used for detecting IgG, IgM, and neutralizing Ab against SARS-CoV-2 antigens. Results: Around 4.9% (15/304) of the participants were SARS-CoV-2 positive, with B.1.631 being the only variant identified. Of 109 individuals harboring anti-SARS-CoV-2 IgG and/or IgM Ab, 45.9% (50/109) had anti-SARS-CoV-2 neutralizing Ab. Of the control samples collected before the pandemic, 3.7% (3/82) were positive for IgG, but negative for neutralizing Ab. Conclusions: Seroprevalence against SARS-CoV-2 occurred in 25% of the indigenous population sample, with almost 50% of these seropositive participants possessing neutralizing antibodies. These findings suggest that the spread of SARS-CoV-2 has been underestimated in the Republic of Congo.

Genomic surveillance of SARS-CoV-2 in the Republic of Congo.

OBJECTIVE: The aim of this study was to carry out whole-genome sequencing (WGS) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), using samples collected from Congolese individuals between April and July 2020. METHODS: Ninety-six samples were screened for SARS-CoV-2 using RT-PCR, and 19 samples with Ct values <30 were sequenced using Illumina Next-Generation Sequencing (NGS). The genomes were annotated and screened for mutations using the web tool 'coronapp'. Subsequently, different SARS-CoV-2 lineages were assigned using PANGOLIN and Nextclade. RESULTS: Eleven SARS-CoV-2 genomes were successfully sequenced and submitted to the GSAID database. All genomes carried the spike mutation D614G and were classified as part of the GH clade. The Congolese SARS-CoV-2 sequences were shown to belong to lineage B1 and Nextclade 20A and 20C, which split them into distinct clusters, indicating two separate introductions of the virus into the Republic of Congo. CONCLUSION: This first study provides valuable information on SARS CoV-2 transmission in the central African region, contributing to SARS CoV-2 surveillance on a temporal and spatial scale.

High SARS-CoV-2 IgG/IGM seroprevalence in asymptomatic Congolese in Brazzaville, the Republic of Congo.

INTRODUCTION: The Republic of the Congo detected its first case of coronavirus disease 2019 (COVID-19) on March 14, 2020, and within several weeks, the country had introduced protective measures that were still in force in July 2020. Over the course of time, the progression in the number of clinical cases has appeared to be lower than expected, although reverse transcription polymerase chain reaction (RT-PCR) testing has been somewhat limited. In order to evaluate the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within the Congolese population, a seroprevalence study was conducted on healthy individuals from different districts of Brazzaville who were willing to know their COVID-19 infection status. METHODS: Oropharyngeal swab and blood samples were collected from 754 healthy volunteers between April 2020 and July 2020. The samples were analyzed for SARS-CoV-2 using a qualitative RT-PCR assay, and Immunoglobulin G (IgG) and Immunoglobulin M (IgM) antibodies were detected using two different rapid tests. RESULTS: A total of 56 participants (7.4%) tested positive for SARS-CoV-2. The remaining 698 participants (92.6%) had negative RT-PCR results; of these, 117 were found to have anti-SARS-CoV-2 antibodies using serological tests. For these RT-PCR-negative subjects, the seroprevalence of IgG and IgM was found to increase over time: from 1.7% and 2.5% in April, up to 14.2% and 17.6% in July, respectively. In April 2020, 5% of the women were found to have IgG or IgM antibodies, whereas the antibodies were not detected in any of the men. The seroprevalence in RT-PCR negative subjects was significantly higher in women within IgG (P = 0.012) and IgM (P = 0.045) over the first three months. CONCLUSION: The proportion of the population who seroconvert over the course of the first wave is an important data to predict the risk of future COVID-19 waves and this will facilitate the efficient use of limited resources in a low income country like the Republic of the Congo.

High prevalence of antibiotic-resistant Escherichia coli in Congolese students.

BACKGROUND: Antimicrobial resistance (AMR) is of growing concern worldwide, and the AMR status in sub-Saharan Africa (SSA), including the Republic of the Congo, is largely undetermined due to a lack of real-time monitoring. As the incidence of multi-resistant Escherichia coli has been increasing in recent years, an investigation was performed to determine the antibiotic resistance of E. coli isolated from stool samples of Congolese students. Furthermore, factors associated with the carriage of resistant bacteria were investigated. METHODS: A total of 339 stool samples from 339 high school students living in the Madibou area of Brazzaville, Republic of Congo, were tested for E. coli. Isolates obtained were tested for susceptibility to 10 antibiotics that are widely used in the region. RESULTS: One hundred and seventy-three (51%) individuals were E. coli-positive in stool, with 61% being female students. Antimicrobial resistance was highest for ceftazidime (65%), followed by amoxicillin (57%), piperacillin-tazobactam (51%), ofloxacin (11%), azithromycin (8%), ciprofloxacin (4%), nalidixic acid (2%), and amoxicillin-clavulanic acid (1%). Antibiotic procurement from non-legalized local vendors had a significant impact on E. coli positivity and antibiotic resistance when compared to procurement from state-licensed pharmacies (p < 0.05). CONCLUSIONS: The high prevalence of resistant commensal E. coli in the community justifies further investigation and urges the need for routine monitoring of antimicrobial susceptibility testing in the region.