Hello, HBV community and researchers! I am Margaret Japhet, a mid career researcher at the Obafemi Awolowo University, Nigeria. My Hepatitis B research started when I detected HB core IgM (HBcIgM) as the only serological evidence of HBV infection among blood donors, publish in Virology Journal. Since then, I developed interest in silent Hepatitis B Virus (HBV) infections, and my HBV research has been on Occult Hepatitis B infection (OBI).
OBI is defined as the presence of replication-competent HBV DNA in the live, in the presence or absence of HBV DNA in the blood of individuals testing negative for currently available assays. This means that that there is the possibility of detecting HBV infection in people that are negative for the routinely used serum marker (Hepatitis B surface antigen-HBsAg) tests for diagnosing Hepatitis B infection (HBI).
When HBV is replicating, its viral DNA gets transformed into what is known as covalently closed circular DNA (cccDNA). In this peculiar phase of HBV infection, cccDNA is in a low state of replication. Therefore, detection of HBV DNA in serum/plasma is intermittent, and when detectable, it is usually at a low viremic range, usually lower than 200 International Units (IU)/mL.
The question is: why the need to study OBI? The importance of OBI cannot be overlooked. (1) New HBV infection can be transmitted through blood transfusion or organ transplant, making WHO HBV eradication plan difficult. (2) it may accelerate the progression of chronic liver disease, leading to cirrhosis (3) In OBI individuals, there may be reactivation in the case of immunosuppression, leading to the possibility of developing fulminant hepatitis. The strong suppression of viral replication typical of the OBI status may cease in the case of immunosuppression, with consequent viral reactivation. Cases of OBI reactivation have been reported following chemotherapy. (4) OBI has been shown to favour the development of hepatocellular carcinoma (HCC). Many studies have revealed a strong association also between OBI and HCC
Two major groups of people with OBI exist. One is the seropositive OBI who have antibodies against the HBV core antigen (anti-HBc) and/or antibodies against HBsAg (anti-HBs) detectable in the serum. The other is the seronegative OBI referring to individuals negative for all HBV serum markers including anti-HBc and anti-HBs and the only evidence of HBV infection is detection of HBV DNA in the liver cells (and rarely circulating HBV DNA). HBV genotype is shown to greatly influence HBV clinical presentation, long-term prognosis, and seroconversion profile. Only five of the ten HBV genotypes have been identified as causing OBI, namely genotypes A, B, C, D, and E. Studies conducted in Africa have highlighted that the three most found genotypes in this region are genotypes A, D, and E
Different studies have been carried out in our lab to establish OBI and to understand factors influencing it. In our lab, we found cases of OBI among paid as well as replacement (unpaid) blood donors who are involved in active blood donation. Hence, OBI actually contributes to new HBV infection. Also, all the OBI cases detected in our lab were in the seropositive OBI group, corroborating reports that 80% of OBI are in the seropositive group. With respect to genotypes, out of 19 OBI cases detected in a study among blood donor, 18 were found to have genotype E, either singly or as mixed infection with other genotypes.
Several aspects of OBI are yet to be explored and understood. For instance, it has been suggested that OBI may not just be common among blood/organ donors, but high OBI prevalence has been found in groups of patients with risk factors for HBV infection, such as people who injected drugs, subjects with hepatitis C virus (HCV) co-infection, human immunodeficiency virus (HIV) co-infection, and patients on dialysis. The occurrence of OBI in fully vaccinated individuals, have also been suggested. We hope to carryout further studies to better understand OBI and factors favouring development of OBI in different groups including HBV positive individual on antivirals, fully vaccinated HBV negative individuals and high risk population for a better comprehension of its epidemiology and influence in eradication of HBV infection, which is still one of the major health problems in the world.
Thank you for reading. I will be happy to answer your question.