Jeffrey C. Hunt

GB Virus C/Hepatitis G Virus Infection: A Favorable Prognostic Factor in Human Immunodeficiency Virus-Infected Patients?

To investigate a possible influence of GB virus C (GBV-C) in immunocompromised patients, the prevalences of GBV-C RNA and anti-E2 antibody in 197 human immunodeficiency virus (HIV)-infected patients and in 120 control blood donors were studied. GBV-C RNA was detected in 33 of 197 HIV-infected patients (16.8%) compared with 1 in 120 blood donors (0.8%) (P < .001). Previous exposure to GBV-C (anti-E2 antibody-positive) was shown in 56.8% of HIV patients and in 9% of blood donors. GBV-C viremia was not associated with hepatitis. Despite approximately equal duration of HIV infection in all subgroups, the CD4 cell counts were significantly higher in GBV-C-viremic patients (344 cells/microL) compared with exposed (259 cells/microL) and unexposed (170 cells/microL) patients (P = .017 and P < .001). Furthermore, Kaplan-Meier analysis demonstrated significantly better cumulative survival in GBV-C RNA-positive HIV-infected patients, suggesting that GBV-C might be a favorable prognostic factor in HIV disease.

Association of Antibody to GB Virus C (Hepatitis G Virus) with Viral Clearance and Protection from Reinfection

GB virus C (GBV-C) RNA and envelope antibody were assessed in a median of 4 samples collected over 6.5 years among injection drug users (IDUs). A marker of GBV-C infection was detected in 110 (94.8%) of 116 IDUs. GBV-C RNA was detected at all visits in 32, was never detected in 70, was acquired in 7, and was cleared in 8. The odds of detecting anti-GBV-C were 103-fold higher in participants without detectable RNA (64 of 70) than in IDUs with persistent RNA (3 of 32; P < 10(-7)). Anti-GBV-C was detected in all 8 instances of RNA clearance. GBV-C RNA never reappeared once it was cleared, and there were no new GBV-C infections among 61 anti-GBV-C-positive IDUs observed for 382 person-years, though all had ongoing drug use. Studies using RNA testing alone may significantly underestimate the occurrence of GBV-C infection. Anti-GBV-C is highly associated with viral clearance and protection from reinfection.

Seven Human Immunodeficiency Virus (HIV) Antigen-Antibody Combination Assays: Evaluation of HIV Seroconversion Sensitivity and Subtype Detection

In this study, we evaluated the performance of two prototype human immunodeficiency virus (HIV) antigen-antibody (Ag-Ab) combination assays, one from Abbott Laboratories (AxSYM HIV Ag-Ab) and the other from bioMerieux (VIDAS HIV Duo Ultra), versus five combination assays commercially available in Europe. The assays were Enzygnost HIV Integral, Genscreen Plus HIV Ag-Ab, Murex HIV Ag-Ab Combination, VIDAS HIV Duo, and Vironostika HIV Uniform II Ag-Ab. All assays were evaluated for the ability to detect p24 antigen from HIV-1 groups M and O, antibody-positive plasma samples from HIV-1 groups M and O, HIV-2, and 19 HIV seroconversion panels. Results indicate that although all combination assays can detect antibodies to HIV-1, group M, subtypes A to G, circulating recombinant form (CRF) A/E, and HIV-1 group O, their sensitivity varied considerably when tested using diluted HIV-1 group O and HIV-2 antibody-positive samples. Among combination assays, the AxSYM, Murex, and VIDAS HIV Duo Ultra assays exhibited the best antigen sensitivity (at approximately 25 pg of HIV Ag/ml) for detection of HIV-1 group M, subtypes A to G and CRF A/E, and HIV-1 group O isolates. However, the VIDAS HIV Duo Ultra assay had a lower sensitivity for HIV-1 group M and subtype C, and was unable to detect subtype C antigen even at 125 pg of HIV Ag/ml. The HIV antigen sensitivity of the VIDAS HIV Duo and Genscreen Plus combination assays was approximately 125 pg of HIV Ag/ml for detection of all HIV-1 group M isolates except HIV-1 group O while the sensitivity of Vironostika HIV Uniform II Ag-Ab and Enzygnost HIV Integral Ag-Ab assays for all the group M subtypes was >125 pg of HIV Ag/ml. Among the combination assays, the AxSYM assay had the best performance for detection of early seroconversion samples, followed by the Murex and VIDAS HIV Duo Ultra assays.

Multicenter trial on mother-to-infant transmission of GBV-C virus

Evidence indicates that the GBV‐C or hepatitis G virus can cause persistent infection in humans, but little is known on the importance of vertical transmission. To assess the risk of mother‐to‐infant transmission and the clinical outcome of infected babies, we investigated 175 anti‐HCV positive mothers and followed‐up their children for 3–33 months. GBV‐C RNA was detected by RT‐PCR and anti‐E2 antibody was assayed by EIA. Thirty‐four (19.4%) women were GBV‐C RNA positive and transmission occurred to 21 (61.8%) babies; 20 (95.2%) acquired GBV‐C alone, and one (4.8%) GBV‐C and HCV. Maternal factors such as intravenous drug use, HIV coinfection, HCV‐RNA positivity, and type of feeding were not correlated with GBV‐C transmission. GBV‐C RNA remained persistently positive in all infected babies but one baby who seroconverted to anti‐E2. Seven (35%) babies with GBV‐C alone developed marginally elevated ALT; the baby with HCV and GBV‐C co‐infection had the highest ALT peak value (664 IU/l). Seven of the 141 (5%) babies born to the GBV‐C RNA negative mothers acquired HCV and six (85.7%) had abnormal ALT. The mean ALT peak value was significantly higher (P < 0.05) for babies with HCV than for those with GBV‐ C. None of the children with GBV‐C or with HCV became icteric. GBV‐C is frequently present in anti‐HCV positive women. The infection is transmitted efficiently from mother to baby and rate of transmission is much higher than that for HCV. GBV‐C can cause persistent infection in babies but usually without clear evidence of liver disease. J. Med. Virol. 54: 107–112, 1998.

Multicenter Evaluation of a New, Automated Enzyme-Linked Immunoassay for Detection of Human Immunodeficiency Virus-Specific Antibodies and Antigen

ABSTRACT A collaborative multicenter study was conducted to evaluate the sensitivity, specificity, and precision of a three-step, fully automated, qualitative microparticle-based enzyme-linked immunoassay (AxSYM HIV Ag/Ab Combo; Abbott Laboratories), designed to simultaneously detect (i) antibodies against human immunodeficiency virus type 1 (HIV-1) and/or type 2 (HIV-2) and (ii) HIV p24 antigen. A significant reduction in the HIV seroconversion window was achieved by combining detection of HIV antibodies and antigen into a single assay format. For 22 selected, commercial HIV seroconversion panels, the mean time of detection with the combined-format HIV antigen-antibody assay was reduced by 6.15 days compared to that with a similar third-generation single-format HIV antibody assay. The quantitative sensitivity of the combination assay for the p24 antigen (17.5 pg/ml by use of the p24 quantitative panel VIH SFTS96′) was nearly equivalent to that of single-format antigen tests. The combination assay demonstrated sensitive (100%) detection of anti-HIV immunoglobulin in specimens from individuals in CDC stages A, B, and C and from individuals infected with different HIV-1 group M subtypes, group O, or HIV-2. The apparent specificity for hospitalized patients (n = 1,938) was 99.90%. In a random population of 7,900 volunteer blood donors, the specificity (99.87%) was comparable to that of a third-generation single-format HIV antibody assay (99.92%) on the same donor specimens. In addition, the combination assay was robust to potential interfering specimens. The precision of the combination was high, with intra- and interrun variances of ≤9.3% for each precision panel specimen or assay control and ≤5.3% for the negative assay control.

Antienvelope antibodies are protective against GBV-C reinfection: Evidence from the liver transplant model

An assay for the detection of antibody against the second envelope (E2) protein of GB virus type C (GBV‐C) has been developed. Early reports suggested that this antibody was a marker of viral clearance, yet it is unknown whether anti‐E2 is protective against further GBV‐C infection. The primary aims were to determine (1) if posttransplantation immunosuppression alters the prevalence of anti‐E2; and (2) if anti‐E2 positivity pretransplantation protects against acquisition of GBV‐C infection posttransplantation. Fifty‐four recipients who underwent orthotopic liver transplantation for end‐stage liver disease of nonviral etiologies were tested for GBV‐C RNA using a PCR‐based assay and anti‐E2 antibodies by an enzyme‐linked immunoassay. Anti‐E2 was present in 35% and in 46% of patients pre‐ and posttransplantation, respectively. Anti‐E2 positivity pretransplantation was strongly associated with anti‐E2 positivity after transplantation (P < 0.001); 83% of patients with anti‐E2 prior to transplantation remained anti‐E2–positive after transplantation. A negative association between presence of GBV‐C viremia and presence of anti‐E2 was found in all patients tested either prior to or following transplantation (P = 0.03). Acquisition of GBV‐C infection was significantly lower in patients who were anti‐E2–positive prior to transplantation (2/13) compared to those who were antiE2–negative (12/26) (P = 0.05). It is concluded that immunosuppression does not reduce the prevalence of anti‐E2 after transplantation in those who are seroreactive prior to transplantation. Anti‐E2 appears to be a neutralizing antibody whose presence at the time of liver transplantation protects against acquisition of GBV‐C infection in the peritransplantation period. J. Med. Virol. 56:253–258, 1998.

Immunoassays to study prevalence of antibody against GB virus C in blood donors

Immunoassays were developed to determine the seroprevalence of antibody against human GB virus C (GBV-C). The antigenic target in each assay was a 44.6-kDa glycosylated protein representing the first 315 amino acids encoded by the GBV-C E2 gene. Sera or plasma were assayed for E2 antibody using an anti-human EIA format in which antigen-coated polystyrene beads were reacted with sample, and bound antibody was detected by addition of enzyme labelled goat anti-human IgG. The presence of anti-E2 antibody was confirmed using a sandwich EIA format in which samples were reacted with antigen coated polystyrene beads, followed by addition of solution phase biotinylated antigen. Detection of antibody captured biotinylated E2 was accomplished by addition of enzyme-conjugated anti-biotin antibody. Antibody against the E2 antigen was detected in 7.4 and 7.8% of 500 sera and 500 plasma, respectively, from US volunteers donating to a Wisconsin blood center, and in approximately 10.7% of hepatitis and retrovirus marker-negative volunteer blood donors from a Missouri blood center. The rate in 1018 sera from US commercial donors at multiple US blood centers was 36.7%. These results indicated a relatively high prevalence of GBV-C exposure in US volunteer donors, and particularly in commercial donors. The clinical implication of the high exposure rate is unclear. These immunoassays are being combined with nucleic acid detection to assess prevalence of GBV-C world wide and to determine if GBV-C plays a role as an etiologic agent.