Determination and Characterization of Occult Hepatitis B in High-Risk Populations in Kenya
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Date
2023
Authors
Kiptoon, Beatrice Jepkemei
Journal Title
Journal ISSN
Volume Title
Publisher
kenyatta university
Abstract
Occult hepatitis B virus (OBI) refers to the detection of HBV DNA in the serum or liver of individuals lacking the HBV surface antigen (HBsAg). It is often described among individuals having antibody to the core antigen as the sole serological marker of infection ("anti-HBc only"). However, it has also been observed in the absence of any serological markers ("seronegative OBI"). In cases of "seropositive" OBI, the presence and quantity of anti-HBs may provide an indication of putative risk for OBI, as isolated studies have shown absent or low levels (≤100 mIU/mL) of anti-HBs are more frequently associated with OBI. This has important consequences for blood donation screening and vaccination policy. The lack of HBsAg detection maybe attributed to the window period during acute infection, the virus's low replication phenotype, or a flaw in the expression or release of HBsAg. Mutations within the surface antigen-coding region have also been associated with loss of immunoassay detection for HBsAg. OBI often results in a non-symptomatic or benign infection, although it has been allied to serious hepatic disease, particularly in those co-infected with HCV or HIV, in which occult HBV is more frequently detected. The prevalence and characteristics of OBI in high-risk groups remain unknown in Kenya. Relying solely detection of HBV surface antigen (HBsAg) may lead to under-diagnosis of OBI cases, emphasizing the need for a comprehensive investigation to inform targeted public health interventions and strategic policies to combat HBV in Kenya. This study aimed at investigating the prevalence and molecular characterization of OBI in high-risk Kenyan populations. Sera from 65 HBsAg-negative patients presenting with jaundice at Kenyan medical facilities and 99 male sex workers (MSM-SW), along with 13 non-MSM men having HIV-positive partners were analyzed. Testing included HBV serological markers and additional hepatitis C virus (HCV) screening for MSM-SW patients. HBV DNA was extracted and analyzed using real-time polymerase chain reaction (rt-PCR). Of the 166 HBsAg-negative samples, 31 (18.7%; 95% CI 13.5 – 25.3) tested positive for HBV DNA, classifying them as OBI positive with an overall prevalence of 18.7%. Notably, 64.5% (20/31) of these cases were found to have HBV core protein antibody (anti-HBc positive). Among the MSM-SW cohort, a 10.1% (10/99; 95% CI 5.6 – 17.6) HBsAg positivity rate was observed. All samples tested negative for HCV. HBV genotype A predominated, with distinct genetic clustering patterns observed among the study cases, indicating potential common networks or non-African sources. The high prevalence of OBI across examined cohorts, along with the occurrence of chronic HBV infection in the MSM-SW population, highlights the necessity for targeted screening programs to enable preventive measures, including HBV vaccination, and ensure access to treatment and care.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Masters of Science in Infectious Diseases in the School of Health Sciences, Kenyatta University
Keywords
Occult Hepatitis B, Kenya