Comparative Analysis of the Vertical Risk of Transmission of Some Blood-Borne Infections in the Republic of Guinea

Vertical transmission of hepatitis B virus in the WHO African region: a systematic review and meta-analysis

BACKGROUND

More new infections with hepatitis B virus (HBV) occur annually in the WHO African region than in the rest of the world combined. We did a systematic review and meta-analysis to estimate the prevalence of hepatitis B surface antigen (HBsAg) in pregnant women and vertical transmission events in the region.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Embase, Scopus, Africa Index Medicus, and Africa Journals Online for publications between Jan 1, 1992, and Jan 7, 2024, with no language restrictions. HBsAg prevalence and vertical transmission (HBsAg positivity in children aged 6-12 months) were estimated with the use of binomial mixed models with logit links, stratified by infant vaccination status. We estimated HBsAg prevalence for subregions of Africa and for the WHO African region by weighting by estimated livebirths for each subregion. We estimated transmission events using WHO and UNICEF vaccine coverage data and UN population estimates.

FINDINGS

We included 113 studies reporting on HBsAg prevalence from 190 983 pregnant women and 11 studies reporting on vertical transmission. HBsAg prevalence in women receiving antenatal care in the WHO African region (based on 2014-23 data) was 6·2% (95% CI 5·3-7·2). No relationship between risk of bias and HBsAg prevalence was observed. In 2022, an estimated 172 000 vertical transmission events (95% CI 82 000-383 000) occurred (0·4% of livebirths), a fall from a peak of 339 000 (149 000-634 000; 1·2% of all livebirths) in 2001. Increasing birth dose vaccination coverage to the WHO target of 90% could reduce vertical transmission by 43·7% (95% CI 11·6-78·0) to 97 000 events per year (95% CI 58 000-160 000). Adding maternal antiviral prophylaxis with 90% coverage could reduce transmission by 86·3% (95% CI 78·4-94·6) to 24 000 events per year (95% CI 14 000-39 000; 0·06% of livebirths) and achieve WHO elimination targets.

INTERPRETATION

Vertical transmission is an important contributor to HBV transmission in the WHO African region. Scaling up of hepatitis B birth dose vaccination and antiviral prophylaxis is urgently needed, which could achieve elimination of vertical transmission.

FUNDING

Wellcome Trust.

Hepatitis B virus preCore/Core region variability in pregnant women in the Republic of Guinea

Introduction. The vertical route of hepatitis B virus (HBV) transmission is a significant problem in African countries, which is characterized by late diagnosis of the disease and high mortality. The high prevalence of hepatocellular carcinoma (HCC) in Africa may be due to variability in the HBV preCore/Core region, mutations in which contribute to disease progression. Molecular genetic characterization of strains circulating among pregnant women may reflect the overall mutational profile of the pathogen in the population. The objective of this study was to analyze the variability of the HBV preCore/Core region circulating among pregnant women in the Republic of Guinea. Materials and methods. The study material included 480 plasma samples obtained from HBV-positive pregnant women from the Republic of Guinea. For all samples, the nucleotide sequences of the preCore/Core region of the HBV genome were sequenced and analyzed. Results. Amino acid variability in the preCore region was determined in 211 (43.96%), and in the Core region in 473 (98.54%) patients. 12 polymorphic sites of the preCore region were identified in which amino acid substitutions occurred, including 8, 2 and 5 positions identified for genotypes E, A and D, respectively. In the Core region, 67 substitution positions were identified, including 46 in samples of genotype E, 23 in HBV genotype A and 26 in genotype D. It was shown that the distribution of substitutions in the preCore and Core regions in HBV genotypes E, A and D differs significantly with a predominance in mutations among HBV genotype E — p 0.0001. Individual characteristic mutations have been identified for each genotype. The most common clinically significant mutations in the preCore/Core region in the study group were identified, including pc-H5D (27,08%), pc-W28* (35,21%), c-E64D (33,54%), c-L116I/V/G (91,46 %), c-T146N (73,13%). The double mutation A1762T/G1764A in the basal core promoter was shown in 74 samples of HBV genotype E, which accounted for 15.42% of the total group and 16.59% of patients with HBV genotype E. Conclusion. The frequency of clinically significant preCore/Core mutations among pregnant women in the Republic of Guinea was determined. The data obtained reflect their prevalence in the general population and can be used to predict the progression of chronic HBV among the region's population.

[Frequency of drug resistance and immune escape mutations in the hepatitis B virus genome detected in pregnant women in the Republic of Guinea]

The aim of the work is to assess the prevalence of hepatitis B virus drug resistance mutations and immune escape mutations in pregnant women in the Republic of Guinea.

MATERIALS AND METHODS

Blood plasma samples obtained from 480 pregnant women from different regions of the Republic of Guinea with laboratory-confirmed viral hepatitis B were studied. Nucleotide sequences for genotype identification and mutation detection were obtained using nested-PCR followed by Sanger sequencing, based on overlapping pairs of primers spanning the complete genome of the virus.

RESULTS AND DISCUSSION

In the examined group, the viral genotype E was the most prevalent (92.92%) compared with subgenotypes A1 (1.67%), A3 (1.46%), D1 (0.63%), D2 (1.04%) and D3 (2.29%). Among the examined HBV-infected pregnant women, 188 (39.17%) had undetectable HBsAg. Drug resistance mutations were detected in 33 individuals, which amounted to 6.88%. The following mutations were found: S78T (27.27%), L80I (24.24%), S202I (15.15%), M204I/V (42.42%). The presence of polymorphic variants not described as drug resistant has also been shown in positions associated with the development of drug resistance to tenofovir, lamivudine, telbivudine and entecavir (L80F, S202I, M204R). When analyzing the MHR and the region of a determinant, mutations were detected in 318 (66.25%) of pregnant women. In 172 of them, which amounted to 54.09%, multiple mutations were found. The amino acid substitutions in 13 positions associated with HBsAg-negative hepatitis B and/or potentially affecting HBsAg antigenicity were identified.

CONCLUSION

The high prevalence of immune escape and drug resistance mutations potentially associated with false-negative result of HBsAg screening, prophylaxis failure, and virological failure of therapy that has been identified among treatment naive pregnant women imposes a serious problem.

Method for hepatitis B virus DNA detecting in biological material at low viral load based on nested PCR with detection on three viral targets in real-time mode

A method has been developed for HBV DNA finding in biological material at low viral load based on nested PCR with real-time detection of three viral targets. When developing the method, blood plasma samples were used from 128 CHB patients living in the regions of the Russian Federation and countries of Central Asia and 173 hemodialysis center patients living in the North-West Federal District. Analytical sensitivity was tested using the stepwise dilution method. HBV was detected by nested PCR. According to the method developed by us, at the first stage, the HBV DNA is amplified using at the first stage oligonucleotides complementary to the greatest similarity regions of the various HBV isolates genomes flanking the entire virus genome. At the second stage, when using the amplification product of the first stage as a template, PCR was performed using three pairs of oligonucleotides and the corresponding oligonucleotide fluorescently labeled probes to three virus genome regions (Core gene, S gene and X gene), as well as one pair of primers and the corresponding probe complementary to a human HPRT gene region. The method sensitivity for DNA extraction from plasma with a 100 μl volume was 10 IU/ml. Obtaining a threshold Ct cycle for only one fluorophore may indicate the presence of HBV DNA in the sample at a load of less than 10 IU/ml, HBV detection in this case is possible with a repeated PCR study of the corresponding sample with HBV DNA extraction from an increased plasma volume (200-1000 μl). The developed method makes it possible to identify the disease in various HBV subgenotypes and can be used to diagnose CHB in the population and risk groups, including those with the HBsAg-negative form of the disease.

[Prevalence of viral hepatitis B markers among blood donors in the Republic of Guinea]

INTRODUCTION

The problem of transfusion safety in relation to parenteral viral hepatitis still remains relevant. Viral hepatitis B (HB) remains the most common viral infection transmitted through transfusion procedures. One of the natural phases of chronic hepatitis B (CHB) is occult hepatitis B infection (OBI), characterized by an undetectable HBsAg (regardless of the other serological markers content) in the presence of hepatitis B virus (HBV) DNA in the liver tissue and an extremely low, up to undetectable, level of viral load in the blood. In the Republic of Guinea, as in most countries on the continent, the prevention of HBV transmission through transfusion is still based on HBsAg serological testing of donors only. In this connection, OBI remains as a potential threat to blood transfusion safety. Detection of HBV DNA is a reliable preventive measure against transmission of the virus from donors with HBsAg-negative HBV infection, especially in highly endemic regions. In this regard, the study was conducted to substantiate recommendations for improving blood safety against the background of significant HBV prevalence in the Republic of Guinea.The aim of the work was the evaluation of serological and molecular markers of HBV infection in blood donors in the Republic of Guinea.

MATERIAL AND METHODS

We examined 250 blood samples obtained from donors living in Conakry, Republic of Guinea. Samples were tested for the presence of serological (surface antigen, HBsAg; antibodies (ABs) to surface (anti-HBs IgG) and core (anti-HBc IgG) antigens) and molecular (DNA) markers of HBV infection.

RESULTS AND DISCUSSION

The overall detection rate of hepatitis B markers was 83.2%; HBsAg was detected in 16.4% of all individuals. The high incidence of HBsAg in men (19.55%) compared to women (8.45%) was shown, the relative risk of HBV infection with the formation of HBsAg-positive chronic hepatitis B in males was also significantly higher. The prevalence of the HBV DNA in the study group was 30.4%, the OBI cases accounted for 15.6%. The prevalence of this form of the disease was shown in donors aged 30-49 years (24.78%), in the group of people younger than 30 years, the incidence was lower (8.73%), and at the age of over 50 years, OBI was not detected. Based on the phylogenetic analysis of 76 virus isolates, it was shown that genotype E prevails in the examined group (85.53%).Cases of pathogen DNA detection occurred in HBsAg-negative blood donors in the presence of anti-HBs IgG (n = 4), as well as in the simultaneous presence of ABs anti-HBs IgG and anti-HBc IgG (n = 7). The viral load exceeded 200 IU/ml in OBI samples. Escape mutations were detected by sequencing in each OBI sample, contributing to the virus escaping from diagnostic based on screening for HBsAg.

CONCLUSION

Assessment of the prevalence viral hepatitis B markers in blood donors, determination of genotypes and clinically significant mutations of virus variants are necessary to ensure safe medical manipulations, control and prevention of the spread of this infectious agent.