Envelope-Specific IgG3 and IgG1 Responses Are Associated with Clearance of Acute Hepatitis C Virus Infection

• Published in: Viruses Vol. 12; no. 1; p. 75
• Main Authors: Walker, Melanie R., Eltahla, Auda A., Mina, Michael M., Li, Hui, Lloyd, Andrew R., Bull, Rowena A.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 08.01.2020; MDPI
• Subjects: Acute Disease; Adult; Antibodies; Antibodies, Neutralizing - immunology; Antibody Formation; antibody isotypes; antibody subclasses; Binding Sites, Antibody; Chronic infection; envelope; Ethics; Female; Genotype & phenotype; Hepacivirus - immunology; Hepatitis C; Hepatitis C - immunology; Hepatitis C Antibodies - immunology; Hepatitis C virus; hepatitis c virus (hcv); HIV; Human immunodeficiency virus; Humans; humoral immunity; Immune clearance; immune response; Immune response (humoral); Immunity, Humoral; Immunoglobulin A; Immunoglobulin G; Immunoglobulin G - classification; Immunoglobulin G - immunology; Immunoglobulin M; Immunoglobulin M - immunology; Infections; Isotypes; Longitudinal Studies; Male; neutralization; neutralizing antibodies; Plasmids; Prospective Studies; Proteins; Vaccines; Viral envelope proteins; Viral Envelope Proteins - immunology; Viral infections; Viruses; West Nile virus; Young Adult; Australia; United States > US; New South Wales Australia; hepatitis C virus (HCV); envelope; humoral immunity; antibody subclasses; antibody isotypes
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v12010075

Hepatitis C virus (HCV) can be cleared naturally in a subset of individuals. However, the asymptomatic nature of acute HCV infection makes the study of the early immune response and defining the correlates of protection challenging. Despite this, there is now strong evidence implicating the humoral immune response, specifically neutralising antibodies, in determining the clearance or chronicity outcomes of primary HCV infection. In general, immunoglobulin G (IgG) plays the major role in viral neutralisation. However, there are limited investigations of anti-HCV envelope protein 2 (E2) isotypes (IgM, IgG, IgA) and IgG subclasses (IgG1–4) in early HCV infection. In this study, using a rare cohort of 14 very recently HCV-infected individuals (4–45 days) with varying disease outcome (n = 7 clearers), the timing and potency of anti-HCV E2 isotypes and IgG subclasses were examined longitudinally, in relation to neutralising antibody activity. Clearance was associated with anti-E2 IgG, specifically IgG1 and IgG3, and appeared essential to prevent the emergence of new HCV variants and the chronic infection outcome. Interestingly, these IgG responses were accompanied by IgM antibodies and were associated with neutralising antibody activity in the subjects who cleared infection. These findings provide novel insights into the early humoral immune response characteristics associated with HCV disease outcome.