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Updated: May 26, 2026

A Protocol for Analyzing Hepatitis C Virus Replication

A Protocol for Analyzing Hepatitis C Virus Replication

Published on: June 26, 2014

Hepatitis C virus proteins inhibit C3 complement production.

Budhaditya Mazumdar¹, Hangeun Kim, Keith Meyer

¹Departments of Internal Medicine, Saint Louis University, Saint Louis, Missouri, USA.

Journal of Virology

|December 16, 2011

Summary

Hepatitis C virus (HCV) infection significantly lowers complement component 3 (C3) levels and impairs innate immunity. The NS5A protein strongly downregulates C3 production by inhibiting key transcription factors.

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Area of Science:

Immunology
Virology
Hepatology

Background:

The third component of human complement (C3) is crucial for innate immune responses, activating both classical and alternative complement pathways.
Chronic hepatitis C virus (HCV) infection can lead to immune dysregulation, but its specific impact on complement pathways remains incompletely understood.

Purpose of the Study:

To investigate the effect of chronic hepatitis C virus (HCV) infection on complement component 3 (C3) levels and expression.
To elucidate the mechanisms by which HCV proteins influence C3 production and innate immune function.

Main Methods:

Quantification of C3 levels in sera from HCV patients and healthy individuals.
Measurement of C3 mRNA expression in liver biopsy specimens and cultured hepatocytes.
Analysis of C3 promoter activity and transcription factor regulation by HCV core and NS5A proteins in vitro.

Main Results:

HCV-infected patients exhibited significantly lower serum C3 levels and reduced C3 mRNA expression in liver tissues compared to healthy controls.
HCV infection in hepatocytes in vitro led to decreased C3 mRNA levels.
HCV core protein weakly repressed C3 promoter activity via downregulation of FXR, while NS5A protein strongly inhibited C3 promoter activity, irrespective of IL-1β induction.
Expression of C/EBP-β, a key transcription factor for C3, was reduced in HCV-infected liver tissues and hepatocytes.

Conclusions:

Chronic HCV infection impairs innate immune function by significantly reducing complement component 3 (C3) levels.
The HCV NS5A protein plays a critical role in this immune impairment by strongly downregulating C3 production through inhibition of transcription factors like C/EBP-β.