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Abstract

Hepatitis B virus (HBV) infects human being and at present about 2 billion people of the world has been infected by HBV at some point of their life and about 240-370 million are chronically infected with HBV. The natural course of HBV infection exhibits considerable variability. In one hand, the majority of HBV-infected persons control HBV replication and liver damages after initial infection. On the other hand, considerable numbers of HBV-infected patients develop chronic hepatitis B (CHB) and complications like cirrhosis of liver (LC) and hepatocellular carcinoma (HCC). The mechanisms underlying these dichotomies have not been properly explored and accordingly evidence-based therapeutic approaches for chronic HBV infection could not be developed. HBV is a non-cytopathic virus with no direct role on liver damage in HBV-infected patients. In one hand, host immunity of HBV-infected patients has important roles in control of HBV and containment of liver damages. On the other hand, recent evidences have unmasked that host immunity is also responsible for ongoing viral replication and progressive liver damages. Thus, host immunity in HBV infection may be categorized in two broad headings; (1) pathogenic immunity and (2) protective immunity.  In this review, a comprehensive discussion will be made about the nature of ‘pathogenic immunity’ and ‘protective immunity’ during chronic HBV infection and their implications for developing new and innovative therapy.