No abstract

PurposeOccult hepatitis B infection (OBI) among HIV positive patients varies widely in different geographic regions. We undertook a study to determine the prevalence of occult hepatitis B infection among HIV infected individuals visiting a health facility in South West Cameroon and characterized occult HBV strains based on sequence analyses.MethodsPlasma samples (n = 337), which previously tested negative for hepatitis B surface antigen (HBsAg), were screened for antibodies against hepatitis B core (anti-HBc) and surface (anti-HBs) antigens followed by DNA extraction. A 366 bp region covering the overlapping surface/polymerase gene of HBV was then amplified in a nested PCR and the amplicons sequenced using Sanger sequencing. The resulting sequences were then analyzed for genotypes and for escape and drug resistance mutations.ResultsTwenty samples were HBV DNA positive and were classified as OBI giving a prevalence of 5.9%. Out of these, 9 (45%) were anti-HBs positive, while 10 (52.6%) were anti-HBc positive. Additionally, 2 had dual anti-HBs and anti-HBc reactivity, while 6 had no detectable HBV antibodies. Out of the ten samples that were successfully sequenced, nine were classified as genotype E and one as genotype A. Three sequences possessed mutations associated with lamivudine resistance. We detected a number of mutations within the major hydrophilic region of the surface gene where most immune escape mutations occur.ConclusionsFindings from this study show the presence of hepatitis B in patients without any of the HBV serological markers. Further prospective studies are required to determine the risk factors and markers of OBI.Electronic supplementary materialThe online version of this article (doi:10.1186/s12981-017-0136-0) contains supplementary material, which is available to authorized users.

Background Hepatitis B virus (HBV) causes significant morbidity and mortality globally primarily due to its ability to cause hepatitis, liver cirrhosis and hepatocellular carcinoma. The Kenya National Blood Transfusion Services screens for Hepatitis B antibodies using the chemiluminescent microparticle immunoassay method. This test does not inform on the genotypic characteristics of the virus or the actual presence of the virus in blood. This study therefore sought to determine the serologic and genotypic profiles of HBV circulating among the voluntary blood donors in Nairobi. Methods Blood samples were collected in plain and EDTA vacutainers and tested for the Hepatitis B surface antigen (HBsAg). HBV DNA was then extracted from plasma, its overlapping P/S gene amplified and sequenced. The resulting sequences were used to analyze for the circulating genotypes and mutations within the P and S genes. Bivariate statistical analysis was used to determine the association between demographic factors and HBV infection. Results A seroprevalence of 2.3% (n = 7) was reported. The age group 19–28 years was significantly associated with HBV infection. Nine samples were positive for HBV DNA; these included 2 HBsAg positive samples and 7 HBsAg negative samples. Genotype A, sub genotype A1 was found to be exclusively prevalent while a number of mutations were reported in the “a” determinant segment of the major hydrophilic region of the S gene associated with antibody escape. RT mutations including mutation rt181T in the P gene conferring resistance against Lamivudine and other ʟ-nucleoside drugs were detected. Conclusion There is a high prevalence of occult HBV infections among these blood donors and therefore the testing platform currently in use requires revision.

Occult hepatitis B infection (OBI) is defined as the presence of hepatitis B virus (HBV) DNA in the liver or serum in the absence of detectable HBV surface antigen (HBsAg). OBI poses a risk for the development of cirrhosis and hepatocellular carcinoma. The prevalence of OBI in Kenya is unknown, thus a study was undertaken to determine the prevalence and molecular characterization of OBI in Kenyan populations at high risk of HBV infection. Sera from two Nairobi cohorts, 99 male sex workers, primarily having sex with men (MSM-SW), and 13 non-MSM men having HIV-positive partners, as well as 65 HBsAg-negative patients presenting with jaundice at Kenyan medical facilities, were tested for HBV serological markers, including HBV DNA by real-time PCR. Positive DNA samples were sequenced and MSM-SW patients were further tested for hepatitis C virus (HCV) infection. Of the 166 HBsAg-negative samples tested, 31 (18.7%; 95% confidence interval [CI] 13.5-25.3) were HBV DNA positive (i.e., occult), the majority (20/31; 64.5%) of which were HBV core protein antibody positive. HCV infection was not observed in the MSM-SW participants, although the prevalence of HBsAg positivity was 10.1% (10/99; 95% CI 5.6-17.6). HBV genotype A was predominant among study cases, including both HBsAg-positive and OBI participants, although the data suggests a non-African network transmission source among MSM-SW. The high prevalence of HBV infection among MSM-SW in Kenya suggests that screening programmes be instituted among high-risk cohorts to facilitate preventative measures, such as vaccination, and establish entry to treatment and linkage to care.