Hepatitis B virus and human immunodeficiency virus co-infection: impact on transmission and natural history of disease

Abstract

There is overwhelming evidence of a strong association between human immunodeficiency virus (HIV) and hepatitis B virus (HBV) infections in areas of low endemicity for both viruses, due to shared risk factors. There is also much evidence that HIV modifies the natural history of HBV infection in these areas: co-infected individuals are more likely to be HBV chronic carriers, with higher levels of HBV infectivity, than HIV-negative individuals. Also, immunosuppression brought about by HIV infection reduces persistence of anti-HBs in previously immune and vaccinated individuals, and can cause HBV reactivation or re-infection in those previously exposed to HBV. Furthermore, HIV infection increases the risk of death from liver disease in HBV co-infected individuals, and this risk increases when these patients are treated with highly active anti-retroviral therapy. However, extensive research has found no convincing evidence that HBV impacts on the transmission and natural history of HIV infection. However, the growing body of literature from sub-Saharan Africa (where both HIV and HBV are endemic, and where the majority of the population have been exposed to HBV long before the time of reaching sexual maturity and being exposed to HIV) stands in sharp contrast with the above findings. In this region, it is clear that the prevalence of HBV in HIV-positive individuals is seldom significantly increased, especially in healthy individuals; and when it is significantly increased, it is not increased to the same extent as in HBV-naïve populations. Also, it is expected that these increases will be caused mainly by reactivation or re-infection.