Debsikréo Nalda, Leye Nafissatou, Lo Gora, Dehainsala Maire, Debsikréo Odan, Diaw Ndeye Aminata, Ba Diao, Diagne Diabou, Souare Abdoulaye, Diouf Ndeye Dieynaba, Kouadio N'da Kouamé Nazaire, Otchere Isaac Darko, Moussa Ali Mahamat, Toure-Kane Ndèye Coumba, Lunel-Fabiani Françoise
Cheikh Anta Diop University, Dakar, Senegal.
Institut de Recherche en Santé, de Surveillance Épidémiologique et de Formation, Dakar, Sénégal.
BMC Infect Dis. 2025 Jul 1;25(1):863. doi: 10.1186/s12879-025-11226-5.
Hepatitis B virus (HBV) infection remains a global public health problem claiming about 1, 1 million lives among the several hundred million people infected with the virus globally. However, low- and middle-income countries including those in sub-Saharan Africa carry the highest burden but limited knowledge of the pathogen. This calls for studies to characterise the circulating genotypes of the virus in Sub-Saharan Africa. This study, sought to determine the molecular characteristics of HBV circulating among pregnant women and students in Chad.
Venous blood samples were collected from pregnant women and students in the capital of Chad between April and August 2021. Whole blood samples were spun at 2500xg at 4 °C for 10 min to separate the cellular parts from the sera. The resulting sera were tested for Hepatitis B surface antigen (HBsAg) using enzyme-linked immunosorbent assay (ELISA). HBsAg positivity was confirmed using the Abbott Architect i1000SR analyser. HBV-DNA viral load detection was performed for HBsAg positive sera. HBV-DNA viral load was determined in HBsAg positive sera samples. The S gene was amplified by nested PCR followed by visualisation of the resulting amplicons under UV transillumination after gel electrophoresis. The amplicons were sequenced using the Sanger technique and subjected to phylogenetic and mutational analyses.
A total of 101 HBsAg-positive participants (recruited among students and pregnant women) were included in the study. The mean age was 25 years and 51.49% were males. Viral load was measured in 53 participants, among whom 27 (50.94%) had a viremia higher than 2000 IU/ml. The constructed phylogeny using 31 samples based of the HBV S gene showed that all strains belonged to the E genotype and evolutionary related to HBV from Cameroon, Central African Republic, Burkina Faso, Sudan and Ghana. The comparative mutational analysis identified low intragroup genetic diversity (0.004%) between Chadian strains with only two loci (codon positions 126 and 141) having nonsynonymous mutations including (Y126H, Y126N, Y126C, L140I, Y141S, Y141R, Y141H, Y141F).
The study shows the presence and circulation of HBV genotype E in Chad. The Chadian strains, compared to other genotype E strains from surrounding countries have very low genetic variability. The presence of immune escape mutations in the HBV S gene could be responsible for escape vaccine strains and thus reduce the efficacy of vaccination. Additionally, the presence of the transmembrane domain in the HBV S gene could alter the antigenicity of HBsAg, contributing to screening failure by standard tests (HBsAg negative despite active infection) or reduce the efficacy of drugs that target HBsAg. These results highlight the need to evaluate hepatitis B vaccination coverage and efficiency in Chad.
乙型肝炎病毒（HBV）感染仍然是一个全球性的公共卫生问题，在全球数亿感染该病毒的人群中，每年约有110万人死亡。然而，包括撒哈拉以南非洲国家在内的低收入和中等收入国家负担最重，但对该病原体的了解有限。这就需要开展研究来确定撒哈拉以南非洲地区该病毒的流行基因型。本研究旨在确定在乍得孕妇和学生中流行的HBV的分子特征。
2021年4月至8月期间，从乍得首都的孕妇和学生中采集静脉血样本。全血样本在4℃下以2500xg离心10分钟，以分离细胞成分和血清。使用酶联免疫吸附测定（ELISA）检测所得血清中的乙型肝炎表面抗原（HBsAg）。使用雅培Architect i1000SR分析仪确认HBsAg阳性。对HBsAg阳性血清进行HBV-DNA病毒载量检测。在HBsAg阳性血清样本中测定HBV-DNA病毒载量。通过巢式PCR扩增S基因，然后在凝胶电泳后于紫外透射光下观察所得扩增子。使用桑格技术对扩增子进行测序，并进行系统发育和突变分析。
本研究共纳入101名HBsAg阳性参与者（从学生和孕妇中招募）。平均年龄为25岁，男性占51.49%。对53名参与者进行了病毒载量检测，其中27名（50.94%）病毒血症高于2000 IU/ml。基于HBV S基因使用31个样本构建的系统发育树表明，所有菌株均属于E基因型，且与来自喀麦隆、中非共和国、布基纳法索、苏丹和加纳的HBV在进化上相关。比较突变分析发现，乍得菌株之间的组内遗传多样性较低（0.004%），只有两个位点（密码子位置126和141）存在非同义突变，包括（Y126H、Y126N、Y126C、L140I、Y141S、Y141R、Y141H、Y141F）。
该研究表明乍得存在HBV基因型E且在流行。与周边国家的其他E基因型菌株相比，乍得菌株的遗传变异性非常低。HBV S基因中免疫逃逸突变的存在可能导致疫苗株逃逸，从而降低疫苗接种效果。此外，HBV S基因中跨膜结构域的存在可能会改变HBsAg的抗原性，导致标准检测筛查失败（尽管有活动性感染但HBsAg阴性）或降低靶向HBsAg药物的疗效。这些结果凸显了评估乍得乙型肝炎疫苗接种覆盖率和效果的必要性。
