A sensitive serodiagnosis of hepatitis C virus (HCV) infection with two non-fused peptides: comparison of antibody responses detected with a newly developed assay and a commercial second-generation test

Chronic hepatitis caused by hepatitis C virus showing a discrepancy between serogroup and genotype because of intergenotypic 2b/1b recombination: A pitfall in antiviral therapy with direct-acting antivirals

A 40-year-old male patient with virologic relapse after daclatasvir plus asunaprevir therapy for a serogroup 1 hepatitis C virus (HCV) infection visited our hospital for retreatment. Virologic examinations revealed that a genotype 2b HCV strain carrying both NS3-S122N / D168A and NA5A-R30Q / L31M / Q54H / Y93H mutations had relapsed. The patient received sofosbuvir plus ribavirin therapy, but virologic relapse occurred once again. Sequencing of the HCV genome clarified an intergenotypic recombination of 2b and 1b with an estimated crossover point between nucleotides 3114 and 3115, corresponding to the N-terminal end of the NS3 region (DDBJ/EMBL/GenBank databases accession no. LC273304). The NS5B-S282T mutation was not detected in the HCV strain, and resistance-association substitutions in the NS3 and NS5A regions were similar to those at baseline. Direct sequencing of the core and NS4A regions corresponding to the targeting sites of genotyping and serogrouping, respectively, is useful to determine the combination of direct-acting antivirals when a discrepancy is observed between the serogroup and genotype of HCV strains.

Clustering of rare peptide segments in the HCV immunome

Our previous research and a comprehensive meta-analysis of data from the literature on epitope mapping has revealed that the B cell epitope repertoire is allocated to rare peptide motifs, i.e., antigenic peptide sequences endowed with a low level of similarity to the host proteome. From a clinical point of view, low-similarity peptides able to evoke an immune response appear to be of special interest for the rational design of vaccines for poorly treatable diseases such as hepatitis-C virus (HCV) infection. Indeed, low similarity peptides would guarantee the highest specificity and lowest cross-reactivity, i.e., effectiveness without adverse side-effects. In this study, aimed at gaining further information for the development of effective anti-HCV peptide-based vaccines, the HCV epitopes recognized by human antibodies and currently catalogued in the Immune Epitope Data Base (IEDB) were examined for pentamer sequence similarities to the human proteome. We report that the analyzed HCV determinants are characterized by the presence of fragment absent from (or scarcely represented in) human proteins. These data confirm the low-similarity hypothesis, according to which a low-similarity to the host proteome defines the nonself character of microbial antigens and modulates peptide immunogenicity. Moreover, this study indicates a concrete and safe immunotherapeutic approach which might be used in a universal anti-HCV vaccine.

Quantitation of anti-hepatitic C virus antibodies in interferon-treated patients by S29-1/S4 ELISA

In 23 patients with chronic hepatitis C who have undergone interferon (IFN) treatment, quantitation of anti-hepatitis C virus IgG antibodies by a second-generation assay S29-1/S4 ELISA [Sato et al. (1993): Microbiology and Immunology 37: 295-304]. (anti-S29-1/S4) was compared with that of anti-HCV core IgG antibodies (C22-3, anticore) and the presence of viral RNA confirmed by the reverse transcription-nested polymerase chain reaction (RT-nested PCR). In 12 complete responders with loss of HCV-RNA and normal alanine aminotransferase (ALT) levels at 6 months after therapy, IgG antibodies quantified by a second-generation assay have decreased significantly at the end of treatment (P < 0.05). Further significant reduction of anti-S29-1/S4 titers was observed at 6 months after therapy (P < 0.01) as well as anti-core antibodies (P < 0.01). On the other hand, in 11 non-responders with persistent or intermittent viremia at 6 months after therapy, no significant change in the level of anti-S29-1/S4 titers was observed, whereas anti-core titers have decreased at the end of therapy (P < 0.01). In contrast, both levels of anti-S29-1/S4 and anti-core have increased at 6 months after treatment (P < 0.05). It is concluded that, although it appears difficult to monitor the effect of virus clearance during IFN therapy, changes in anti-S29-1/S4 titers after IFN treatment correlate with virus clearance and with anti-core titers.

Rapid diagnosis of Argentine hemorrhagic fever by reverse transcriptase PCR-based assay

Argentine hemorrhagic fever (AHF) is an endemo-epidemic disease caused by Junín virus. This report demonstrates that a reverse transcriptase (RT) PCR-based assay developed in our laboratory to detect Junín virus in whole blood samples is sensitive and specific. The experiments were conducted in a double-blinded manner using 94 clinical samples collected in the area in which AHF is endemic. The RT-PCR-based assay was compared with traditional methodologies, including enzyme-linked immunosorbent assay, plaque neutralization tests, and occasionally viral isolation. The calculated parameters for RT-PCR diagnosis, with seroconversion as the "gold standard," were 98% sensitivity and 76% specificity. It is noteworthy that 94% of the patients with putative false-positive results (RT-PCR positive and no seroconversion detected) exhibited febrile syndromes of undefined etiology. These results could be interpreted to mean that most of those patients with febrile syndromes were actually infected with Junín virus but did not develop a detectable immune response. Furthermore, 8 laboratory-fabricated samples and 25 blood samples of patients outside the area in which AHF is endemic tested in a similar way were disclosed correctly (100% match). The RT-PCR assay is the only laboratory test available currently for the early and rapid diagnosis of AHF. It is sensitive enough to detect the low viremia found during the period in which immune plasma therapy can be used effectively, reducing mortality rates from 30% to less than 1%.

Immune responses of blood donors to peptides of various lengths and those with genotypic sequence variations corresponding to the N-terminal portion of the core protein of hepatitis C virus

Immune reactivities of blood donor sera with the peptides of various lengths (24, 30, 40 and 50 mer) and those with genotypic sequence variations in the N-terminal portion of the core protein of hepatitis C virus (HCV) were compared by enzyme-linked immunosorbent assays. It was found that a 40-mer oligopeptide (amino acids 2-41) was recognized more frequently than other peptides even in serum samples that did not react with the C22-3 (core) by the recombinant immunoblot assay (RIBA-II). On the other hand, a 30-mer peptide (amino acids 1-30) had good correlation with viremia as confirmed by the polymerase chain reaction (PCR). In addition, four individuals showed the obvious differences in the immune responses to 30-mer oligopeptides representing the 4 genotypic variations. As a result, some samples that were PCR-positive but nonreactive by a commercial assay were found to react with short synthetic peptides in the N-terminal portion of the core protein.

Molecular cloning of HCV and clinical application

Fifty-five clones encoding epitopes of HCV were isolated from Japanese patients. Their amino acid homology (AAH) to the sequence of prototype (HCV-1) ranged from 47% to 94%. These sequences cover 60% of the HCV genome lacking M/E and NS2 regions suggesting a very low or lacking immunogenicity for these regions. Two test kits for detection of anti-HCV antibody were developed using a combination of a synthetic peptide (AR142) containing the epitope of N14 (QRKTKRSTNRR) having a homology to the core of HCV of 8/11AA and a non-fusion recombinant protein Y19 starting from amino acid number (AAN) 1380 to 1507 in the NS3 region showing a AAH to the HCV-1 of 90%, and a combination of a mixture of three synthetic peptides of S29 AAN of 1-30, 38-65 and 47-74 of the core and a non-fused recombinant protein S4 AAN of 1287-1506 having a 93% AAH of the NS3 region. They showed almost the same order of sensitivity and specificity of the second-generation kits when tested with serum from blood donors and patients with non-A, non-B hepatitis. It should also be stressed that in all of the complete responders of a recombinant alpha-interferon therapy, the antibody levels against AR142 gradually decreased during and after the treatment. In 1992, studies performed for 125 patients with hepatocellular carcinoma in our clinic shows that of these 16 patients might developed from either chronic non-B, non-C liver diseases or chronic liver diseases caused by mutant(s) of HCV as their serum were negative for HBsAg and second-generation of anti-HCV.