Humoral and cellular immune responses to the GB virus C/hepatitis G virus envelope 2 protein

Abstract

Immune responses to two recombinant envelope 2 (E2) proteins, representing genotypes 1 and 2 of the GB virus C, or the hepatitis G virus (GBV-C/HGV), were studied in mice and in 48 individuals with, or without, chronic, or past GBV-C/HGV infection. Immunised mice developed E2-specific antibodies (mean titres, 1:1,167 to 1:9,360), recognising linear antigenic regions and proliferative and IL-2, IL-6 and gammaIFN cytokine responses regardless of the viral genotype. Individuals with past GBV-C infection had E2 antibody titres from 1:1,500 to 1:7,500 that did not recognise the E. coli derived E2 protein or linear antigenic regions. Proliferative E2-specific responses were detected in peripheral blood mononuclear cells from 6/22 (27%) persons with, and in none without GBV-C markers (P<0.05). Thus, E2-specific immune responses are mainly crossreactive between different variants of GBV-C/HGV, although proliferative responses appear to be rare.

GB Virus C/Hepatitis G Virus

“…It seems that proliferative responses in peripheral blood mononuclear cells are rare during GBV-C:HGV infections, which may be consistent with their mainly asymptomatic nature (39).…”

“…A possible explanation for this might be that GBV-C:HGV has adopted strategies to replicate in human hepatocytes without priming a host immune response, or possibly that GBV-C:HGV can counteract such a response. However, we have recently found that the GBV-C E2 protein behaves as a normal immunogen when given to mice as an exogenous or endogenous immunogen (39). Also, no evidence is at hand for the existence of a hypervariable region of E2 (97) which would suggest immune evasion.…”

“…The cell-mediated immune responses during chronic GBV-C infections have been studied (39). It seems that proliferative responses in peripheral blood mononuclear cells are rare during GBV-C:HGV infections, which may be consistent with their mainly asymptomatic nature (39).…”