Spontaneous control of primary hepatitis C virus infection and immunity against persistent reinfection

Abstract

Background & aims: We followed patients with ongoing hepatitis C virus (HCV) exposure following control of an initial HCV infection to determine whether primary control conferred protection against future persistent infections.

Methods: Twenty-two active injection drug users (IDU) who had cleared a primary hepatitis C viremia for at least 60 days were monitored monthly. Reinfection was defined as the detection of a new HCV infection. Protection was assessed based on the magnitude and duration of viremia following reinfection and generation of T-cell and neutralizing antibody (nAb) responses.

Results: Reinfection occurred in 11 IDU (50%) who previously spontaneously controlled primary HCV infection. Although viral clearance occurs in approximately 25% of patients with primary infections, spontaneous viral clearance was observed in 83% of reinfected patients. The duration and maximum level of viremia during subsequent episodes of reinfection were significantly decreased compared with those of the primary infection in the same subjects. In contrast to chronic infection, reinfection was associated with a significant increase in the breadth of T-cell responses. During acute infection, nAbs against heterologous viral pseudoparticles were detected in 60% of reinfected subjects; cross-reactive nAbs are rarely detected in patients who progress to chronic infection.

Conclusions: HCV reinfection is associated with a reduction in the magnitude and duration of viremia (compared with the initial infection), broadened cellular immune responses, and generation of cross-reactive humoral responses. These findings are consistent with development of adaptive immunity that is not sterilizing but protects against chronic disease.

Figure 1

Flow of participants in the study. The ratio of cleared to persistent subjects during reinfection was significantly greater than during primary infection (P=0.001).

Figure 2

Representative graphs demonstrating the history of viremia and plasma ALT levels in A) No reinfection, B) Reinfection-cleared and C) Reinfection-persistent groups. HCV genotype of primary infection and reinfection is indicated and the time over which a unique virus is detected is denoted by a horizontal black line. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Black triangles denote ALT activity (IU/ml) detected in plasma samples obtained at given time points from date of first detection of viremia.

Figure 2

Representative graphs demonstrating the history of viremia and plasma ALT levels in A) No reinfection, B) Reinfection-cleared and C) Reinfection-persistent groups. HCV genotype of primary infection and reinfection is indicated and the time over which a unique virus is detected is denoted by a horizontal black line. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Black triangles denote ALT activity (IU/ml) detected in plasma samples obtained at given time points from date of first detection of viremia.

Figure 2

Representative graphs demonstrating the history of viremia and plasma ALT levels in A) No reinfection, B) Reinfection-cleared and C) Reinfection-persistent groups. HCV genotype of primary infection and reinfection is indicated and the time over which a unique virus is detected is denoted by a horizontal black line. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Black triangles denote ALT activity (IU/ml) detected in plasma samples obtained at given time points from date of first detection of viremia.

Figure 3

Clearance of a primary infection attenuates the infection kinetics of subsequent infections. A) Maximum HCV RNA concentrations (IU/ml) detected in serum samples obtained during primary and subsequent infections in subjects with sufficient follow-up following the detection of a reinfection. Triangles represent maximum viremia detected in Reinfection – persistent subjects. The maximum viremia in each subject during initial infection and reinfection is connected by a line. Median maximum HCV RNA concentration of reinfections was significantly lower than primary infections (P < 0.001). B) Duration of viremia (days) during primary infections and subsequent infections in Reinfection – cleared subjects. The duration of initial and reinfection viremia in each subject is connected by a line. The duration of viremia during reinfection was significantly lower than in primary infection (P = 0.019).

Figure 3

Clearance of a primary infection attenuates the infection kinetics of subsequent infections. A) Maximum HCV RNA concentrations (IU/ml) detected in serum samples obtained during primary and subsequent infections in subjects with sufficient follow-up following the detection of a reinfection. Triangles represent maximum viremia detected in Reinfection – persistent subjects. The maximum viremia in each subject during initial infection and reinfection is connected by a line. Median maximum HCV RNA concentration of reinfections was significantly lower than primary infections (P < 0.001). B) Duration of viremia (days) during primary infections and subsequent infections in Reinfection – cleared subjects. The duration of initial and reinfection viremia in each subject is connected by a line. The duration of viremia during reinfection was significantly lower than in primary infection (P = 0.019).

Figure 4

Significantly greater numbers of new T cell responses are detected during reinfection than during chronic infection. Values represent new T cell responses in chronically-infected subjects in whom the same virus is detected during chronic infection, chronically-infected subjects in whom more than one genetically-distinct virus is detected during chronic infection, and reinfected subjects. A new T cell response was defined as a peptide that was recognized, in an IFN-γ ELISpot, by PBMCs obtained greater than 200 days following the first detection of viremia but not by PBMCs collected at earlier time points in reinfected subjects and chronically-infected individuals. P > 0.05 compared to both chronically-infected groups.

Figure 5

Reinfection is associated with generation of cross-reactive nAb. Representative graphs demonstrating nAb titers in A) a subject who controls reinfection and B) a persistently-reinfected subject. Solid line represents reciprocal ID50 nAb titer against a genotype 1a HCVpp (H77). Undetectable nAb titers were assigned a value of 25. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Viral E2 protein sequence divergence from H77 E2 protein sequences of viruses obtained during C)reinfection and D) initial infection from subjects in whom nAb were and were not detected during reinfection. No significant difference in the E2 protein sequence divergence between groups was observed during reinfection and initial infection.

Figure 5

Reinfection is associated with generation of cross-reactive nAb. Representative graphs demonstrating nAb titers in A) a subject who controls reinfection and B) a persistently-reinfected subject. Solid line represents reciprocal ID50 nAb titer against a genotype 1a HCVpp (H77). Undetectable nAb titers were assigned a value of 25. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Viral E2 protein sequence divergence from H77 E2 protein sequences of viruses obtained during C)reinfection and D) initial infection from subjects in whom nAb were and were not detected during reinfection. No significant difference in the E2 protein sequence divergence between groups was observed during reinfection and initial infection.

Figure 5

Reinfection is associated with generation of cross-reactive nAb. Representative graphs demonstrating nAb titers in A) a subject who controls reinfection and B) a persistently-reinfected subject. Solid line represents reciprocal ID50 nAb titer against a genotype 1a HCVpp (H77). Undetectable nAb titers were assigned a value of 25. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Viral E2 protein sequence divergence from H77 E2 protein sequences of viruses obtained during C)reinfection and D) initial infection from subjects in whom nAb were and were not detected during reinfection. No significant difference in the E2 protein sequence divergence between groups was observed during reinfection and initial infection.

Figure 5

Reinfection is associated with generation of cross-reactive nAb. Representative graphs demonstrating nAb titers in A) a subject who controls reinfection and B) a persistently-reinfected subject. Solid line represents reciprocal ID50 nAb titer against a genotype 1a HCVpp (H77). Undetectable nAb titers were assigned a value of 25. Black circles represent HCV RNA concentrations (IU/ml) detected in serum or plasma samples obtained at given time points from date of first detection of viremia. Dotted-line denotes the HCV RNA limit of detection. Samples below the HCV RNA limit of detection were assigned a value of 25 IU/ml. Viral E2 protein sequence divergence from H77 E2 protein sequences of viruses obtained during C)reinfection and D) initial infection from subjects in whom nAb were and were not detected during reinfection. No significant difference in the E2 protein sequence divergence between groups was observed during reinfection and initial infection.