Occult Infection with Hepatitis C Virus: Looking for Clear-Cut Boundaries and Methodological Consensus

Area of Science:

• Hepatology
• Virology
• Immunology

Background:

• Chronic hepatitis C (HCV) cure is defined by sustained virologic response, leading to liver damage amelioration.
• The existence and clinical significance of occult HCV infection (OCI), where serum HCV-RNA is undetectable, remain controversial.
• OCI is characterized by extrahepatic HCV replication and continuous immune stimulation by low-level HCV antigens.

Purpose of the Study:

• To review recent data on the molecular, clinical, and epidemiological aspects of OCI.
• To identify methodological pitfalls causing inconsistencies in OCI research.
• To discuss the implications of OCI for understanding HCV persistence and disease progression.

Main Methods:

• Review of recently published data on occult HCV infection.
• Analysis of molecular and clinical evidence for extrahepatic HCV replication.
• Identification and discussion of methodological challenges in OCI detection and interpretation.

Main Results:

• Accumulated data strongly support extrahepatic HCV replication in individuals with undetectable serum HCV-RNA.
• OCI involves incomplete viral clearance and continuous immune stimulation, potentially driving liver pathology.
• Extrahepatic HCV replication may contribute to HCV-related complications beyond the liver.

Conclusions:

• Occult HCV infection is supported by evidence of extrahepatic viral replication.
• OCI represents a state of persistent immune stimulation, contributing to liver disease progression and complications.
• Clear definitions and standardized detection protocols are essential for advancing OCI research and clinical management.