E2/nonstructural protein 1, the putative envelope glycoprotein (gp72) of HCV, possesses an N-terminal hypervariable (E2 HV) domain from amino acids 384 to 414 of unknown sinificance. The high degree of amino acid sequence variation in the E2 HV domain appears to be comparable to that observed in the human immunodeficiency virus type 1 gp120 V3 domain. This observation and the observation that the HCV E2 HV domain lacks conserved secondary structure imply that, like the V3 loop of human immunodeficiency virus 1 gpl20, the N-terminal E2 region may encode protective epitopes that are subject to immune selection. Antibodyepitope binding studies revealed five isolate-specific linear epitopes located in the E2 HV region. These results suggest that the E2 HV domain is a target for the human immune response and that, in addition to the three major groups ofHCV, defined by nucleotide and amino acid sequence identity among HCV isolates, E2 HV-specific subgroups also exist. Analysis of the partial or complete E2 sequences of two individuals indicated that E2 HV variants can either coexist simultaneously in a single individual or that a particular variant may predominate during different episodes of disease. In the latter situation, we found one individual who developed antibodies to a subregion ofthe E2 HV domain (amino acids 396-407) specific to a variant that was predominant during one major episode ofhepatitis but who lacked detectable antibodies to the corresponding region of a second variant that was predominant during a later episode of disease. The data suggest that the variability in the E2 HV domain may result from immune selection. The fings of this report could impact vaccine strategies and drug therapy programs designed to control and eliminate HCV.HCV is the major etiologic agent oftransfusion-associated and community-acquired non-A, non-B hepatitis on several continents (1-3). A high rate ofchronic hepatitis is associated with HCV infections (4, 5). Two patterns of HCV-associated chronic liver disease have been described in humans and chimpanzees (4 tTo whom reprint requests should be addressed. 3468The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

We constructed recombinant vaccinia virus vectors for expression of the structural region of hepatitis C virus (HCV). Infection of mammalian cells with a vector (w/HCVI 906) encoding C-El-E2-NS2 generated major protein species of 22 kDa (C), 33 to 35 kDa (El), and 70 to 72 kDa (E2), as observed previously with other mammalian expression systems. The bulk of the El and E2 expressed by w/HCV1 906 was found integrated into endoplasmic reticulum membranes as core-glycosylated species, suggesting that these El and E2 species represent intracellular forms of the HCV envelope proteins. HCV El and E2 formed El-E2 complexes which were precipitated by either anti-El or anti-E2 serum and which sedimented at approximately 15 S on glycerol density gradients. No evidence of intermolecular disulfide bonding between El and E2 was detected. El and E2 were copurified to approximately 90% purity by mild detergent extraction followed by chromatography on Galanthus nivalus lectin-agarose and DEAE-Fractogel. Immunization of chimpanzees with purified El-E2 generated high titers of anti-El and anti-E2 antibodies. Further studies, to be reported separately, demonstrated that purified El-E2 complexes were recognized at high frequency by HCV+ human sera (D.

Broad, multispecific CD4؉ and CD8 ؉ T-cell responses to the hepatitis C virus (HCV), as well as viruscross-neutralizing antibodies, are associated with recovery from acute infection and may also be associated in chronic HCV patients with a favorable response to antiviral treatment. and CD8؉ T-cell responses to E1E2 and NS345 was obtained by first priming with Th1-adjuvanted proteins and then boosting with chimeric, defective alphaviruses expressing these HCV genes. In addition, this prime/ boost regimen resulted in the induction of anti-E1E2 antibodies capable of cross-neutralizing heterologous HCV isolates in vitro. This vaccine formulation and regimen may therefore be optimal in humans for protection against this highly heterogeneous global pathogen.

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To demonstrate vertical transmission of hepatitis C virus (HCV) from an HCV-infected, non-human immunodeficiency virus type 1-infected mother to her infant and to assess the distribution of viral species in the mother and infant, the hypervariable region of the gene encoding the putative envelope glycoprotein E2 (E2HV) was sequenced in three mothers and one mother-infant pair. The data indicate that (i) quasispecies distributions of HCV E2HV variants were found in all four mothers, (ii) a single predominant HCV E2HV variant was found in the infant of a mother shown to have nine predominant E2HV variants, and (iii) the infant's E2HV variant was highly related to, but not identical with, the nine variants identified in the mother at the time of birth. These findings indicate that HCV is transmitted from mother to infant and raise the