Optimisation and validation of a new method for antibody dependent cellular phagocytosis in hepatitis C virus infection

Lack of a simple, high throughput antibody-dependent cellular phagocytosis (ADCP) assay has limited our understanding of its potential role of in hepatitis C (HCV) infection. Here, we optimised a flow-cytometry based ADCP assay using HCV envelope (E2)-protein coated microbeads that were opsonised with anti-E2 monoclonal IgG antibody (alpha E2 mAb) and the THP-1 monocyte cell line as effector cells. We found 1.5 x 109/ml microbeads opsonised with 5 mu g/ml alpha E2 mAb and 1.6 x 106/ml THP-1 cells were optimal conditions to distinguish between healthy controls and patients with HCV. This optimised assay was then used to investigate ADCP in plasma obtained from 72 patients with chronic HCV infection and 15 healthy controls. We found that 75% of patients with genotype 1 and 87% of patients with genotype 3 HCV infection had significantly higher levels of ADCP compared to healthy controls. In patients, there was a significant correlation between increase in ADCP and higher concentrations of anti-E2 IgG antibodies in the plasma. Taken together, we established a simple, quick and high throughput ADCP assay for HCV infection that can readily be used for screening of large cohorts of patients and investigation of the role of ADCP in the pathogenesis or protection from this disease.

Automated summary

This study established a flow-cytometry based ADCP assay for HCV infection using E2-protein coated microbeads and found that patients with genotype 1 and genotype 3 HCV infection had significantly higher levels of ADCP compared to healthy controls. There was a significant correlation between increase in ADCP and higher concentrations of anti-E2 IgG antibodies in the plasma of patients.