Multispecific T cell response and negative HCV RNA tests during acute HCV infection are early prognostic factors of spontaneous clearance

Abstract

Background/aims: Hepatitis C virus (HCV) infection results in a high frequency of chronic disease. The aim of this study was to identify early prognostic markers of disease resolution by performing a comprehensive analysis of viral and host factors during the natural course of acute HCV infection.

Methods: The clinical course of acute hepatitis C was determined in 34 consecutive patients. Epidemiological and virological parameters, as well as cell mediated immunity (CMI) and distribution of human leukocyte antigens (HLA) alleles were analysed.

Results: Ten out of 34 patients experienced self-limiting infection, with most resolving patients showing fast kinetics of viral clearance: at least one negative HCV RNA test during this phase predicted a favourable outcome. Among other clinical epidemiological parameters measured, the self-limiting course was significantly associated with higher median peak bilirubin levels at the onset of disease, and with the female sex, but only the latter parameter was independently associated after multivariate analysis. No significant differences between self-limiting or chronic course were observed for the distribution of DRB1 and DQB1 alleles. HCV specific T cell response was more frequently detected during acute HCV infection, than in patients with chronic HCV disease. A significantly broader T cell response was found in patients with self-limiting infection than in those with chronic evolving acute hepatitis C.

Conclusion: The results suggest that host related factors, in particular sex and CMI, play a crucial role in the spontaneous clearance of this virus. Most importantly, a negative HCV RNA test and broad CMI within the first month after onset of the symptoms represent very efficacious predictors of viral clearance and could thus be used as criteria in selecting candidates for early antiviral treatment.

Figure 1

Follow up of HCV RNA and ALT level in patients with self-limiting HCV acute infection. (A) Viral load. Different symbols represent data points for each individual subject. Viral loads are indicated on the vertical axis. The shaded area represents the range of values below the threshold of sensitivity of the employed HCV RNA determination method. The time scale is shown on the horizontal axis. (B) ALT levels. Different symbols represent data points for each individual subject. ALT values are indicated on the vertical axis. The shaded area represents the normal range of values. The time scale is shown on the horizontal axis.

Figure 2

Magnitude and breadth of the T cell response during the early phase of HCV infection in subjects with (A) acute self-limiting infection (n = 7) and with (B) a chronic evolution (n = 12). PBMC samples collected at the time of enrollment (T = 0) and one month after (T = 1), were tested by IFN-γ ELIspot assay against seven peptide pools corresponding to Core, NS3 protease (NS3p), NS3 helicase (NS3h), NS4, NS5a, and NS5b (split in two pools NS5b-I and NS5b-II). For each patient, results from the time point showing the highest frequency of HCV specific CMI were reported. It was T = 0 for patients A26, A45, A50, A1, A9, A12, A16, A18, A34, and A35 and T = 1 for patients A24, A25, A43, A46, A5, A6, A14, A37, and A49. To simplify, only responses above the threshold defined using seronegative subjects (see Materials and Methods) are shown. For all the remaining subjects ELIspot responses were negative at both time points tested. Numbers represent spot forming cells (SFC)/10⁶ PBMCs. In subjects A26 the response against NS3p and NS3h exceed the upper value of the scale.

Figure 3

Breadth of anti-HCV T cell response during acute and chronic infection: the number of HCV antigens recognised by each individual is shown as a single dot. Breadth of the response was compared between individuals with self-limited acute hepatitis, or acute hepatitis C and chronic evolution and the patients with late chronic infection. For each patient with acute infection we have plotted the higher response measured at either T = 0 or T = 1. Horizontal lines indicate median numbers of recognised peptide pools for each group. Statistically significant difference between groups was calculated by Mann Whitney test.

Figure 4

Magnitude and breadth of the T cell response in chronically infected patients. PBMC samples were tested by IFN-γ ELIspot assay against the seven HCV peptide pools. Only responses above the threshold defined using seronegative subjects (see Materials and Methods) are shown.