Biomedical subjects

D R Milich

Publications and source records attributed to D R Milich.

At least 55 records · Page 3Linked to original sources

PubMed1994

Distinguishing between acute and symptomatic chronic hepatitis B virus infection.

BACKGROUND/AIMS: Differentiating between an acute hepatitis B (AH-B) infection and an acute exacerbation of a chronic hepatitis B (CH-B) infection can present a problem for the clinician. The only current serological method of distinguishing between acute and symptomatic chronic hepatitis B virus (HBV) infection is the immunoglobulin M antibody to hepatitis B core antigen (anti-HBc) assay, which can be problematic. Therefore, in an attempt to better distinguish between acute and chronic HBV infection, sera from 26 patients with AH-B and 53 patients with CH-B were compared in a variety of experimental immunoassays. METHODS: Experimental assays have been designed to detect free antibody to hepatitis B e antigen (anti-HBe), hepatitis B e antigen (HBeAg)/anti-HBe immune complexes (ICs), and hepatitis B surface antigens (HBsAg)/antibody to hepatitis B surface antigen (anti-HBs) in the presence of excess antigen. An additional assay was developed to detect a novel anti-HBc specificity, designated antibody to woodchuck hepatitis virus (anti-HBcW), which cross-reacts with the core antigen of the woodchuck hepatitis virus. RESULTS: Sera from patients with CH-B showed significantly higher levels of free anti-HBe, HBeAg/anti-HBe ICs, and HBsAg/anti-HBs ICs compared with AH-B patient sera. Furthermore, patients with CH-B consistently produced high titer anti-HBcW, whereas patients with AH-B produced little or no anti-HBcW antibody. CONCLUSIONS: The serology of AH-B infection and symptomatic CH-B infection can be distinguished using a variety of experimental immunoassays in addition to the immunoglobulin M anti-HBc assay.

Acute Disease↗

PubMed1994

Hybrid hepatitis B virus core-pre-S proteins synthesized in avirulent Salmonella typhimurium and Salmonella typhi for oral vaccination.

Avirulent salmonellae expressing foreign genes are attractive for use as oral vaccine carriers. To facilitate the stable expression of heterologous genes without conferring antibiotic resistance, a deletion of the asdA1 gene was introduced into Salmonella typhimurium and S. typhi delta cya delta crp mutant vaccine strains. An asd-complementing plasmid expressing hybrid hepatitis B virus nucleocapsid-pre-S (HBcAg-pre-S) particles was constructed. These hybrid HBcAg-pre-S particle genes were stably expressed in S. typhimurium and S. typhi delta cya delta crp mutant vaccine strains in this balanced, lethal host-vector combination. A single oral immunization of BALB/c mice with a recombinant S. typhimurium delta cya delta crp mutant synthesizing hybrid HBcAg-pre-S elicited potentially virus-neutralizing anti-pre-S serum immunoglobulin G antibodies. In addition, serum immunoglobulin G recognizing S. typhimurium lipopolysaccharide was induced. Distribution in tissue after oral immunization was analyzed in one plasmid-strain combination. The recombinant S. typhimurium colonized the gut-associated lymphoid tissue and the spleen and persisted for over 4 weeks, retaining the HBcAg-pre-S expression plasmid. An isogenic virulence plasmid-cured S. typhimurium delta cya delta crp strain expressing the same HBcAg-pre-S gene had reduced immunogenicity for the carried antigen after oral immunization.

Administration, Oral↗

PubMed1993

Structure of hepatitis B virus core and e-antigen. A single precore amino acid prevents nucleocapsid assembly.

The hepatitis B virus core gene codes for two polypeptides: the core protein, which assembles to form particles (HBcAg), and the secreted precore protein (HBeAg). Expression vectors directing the synthesis in Escherichia coli of a recombinant HBeAg corresponding in sequence to serum-derived HBeAg encompassing the 10 precore amino acids remaining after cleavage of the precursor and residues 1-149 of HBcAg (PC-HBeAg) were constructed. Recombinant PC-HBeAg, HBcAg, and C-terminally truncated HBcAg were isolated from E. coli and analyzed by sucrose velocity sedimentation, electron microscopy, anti-HBc/e specific monoclonal antibody analysis, and for immunogenicity. HBcAg and truncated HBcAg formed 27-nm particles and displayed HBc antigenicity. In contrast, PC-HBeAg was nonparticulate and did not band in sucrose gradients. PC-HBeAg was recognized efficiently by HBeAg-specific antibodies and displayed little HBc antigenicity. Immunogenicity studies including T and B cell recognition confirmed that PC-HBeAg demonstrates HBe antigenicity. The presence of the 10 precore amino acids therefore prevented particle formation. To analyze which precore amino acids might be responsible for the prevention of particle formation a cysteine to glutamine substitution at amino acid position -7 was introduced into PC-HBeAg (-7C-->Q)PC-HBeAg. This single amino acid change at position -7 restored particle formation and HBc antigenicity. The evolutionarily conserved cysteine at position -7 thus appears responsible for the prevention of particle assembly in the HBeAg biosynthesis pathway.

Animals↗

PubMed1993

Serology of acute exacerbation in chronic hepatitis B virus infection.

BACKGROUND: Liver injury in many patients with chronic hepatitis B is sporadic and is often characterized by acute exacerbations alternating with relatively normal liver function. The aim of this study was to perform detailed serological and biochemical analysis during periods of active liver disease to better understand the mechanisms responsible for the cyclic nature of liver injury. METHODS: A series of serum samples from 19 hepatitis B e antigen (HBeAg)-positive patients were analyzed for alterations in serum hepatitis B virus (HBV) DNA, HBeAg, anti-HBe production, and HBeAg-specific immune complex formation before, during, and after spontaneous acute exacerbations of liver injury. RESULTS: This analysis revealed significant correlations between increasing levels of serum HBV DNA, HBeAg, HBeAg-specific immune complexes, and liver injury. These results suggest that increases in viral replication and accumulation of viral proteins in the serum and intracellularly and the subsequent immune response play an important role in initiating acute exacerbations of liver injury in chronic hepatitis B infection. CONCLUSIONS: We propose that production of the secreted and cellular forms of the nucleoprotein reaches a threshold level and elicits specific immune responses, which mediate liver injury.

Antibodies, Monoclonal↗

PubMed1993

A virulent Salmonella expressing hybrid hepatitis B virus core/pre-S genes for oral vaccination.

This report reviews and extends data on the use of hepatitis B virus (HBV) core (HBcAg) particles as a carrier moiety for B-cell epitopes of the HBV envelope proteins. Virus-neutralizing epitopes of the HBV pre-S region were inserted at the N-terminus, the N-terminus through a precore linker sequence, the C-terminus and an internal position of HBcAg by genetic engineering in Escherichia coli. The hybrid HBc/pre-S proteins were purified and their antigenicity and immunogenicity analysed. All purified HBc/pre-S particles were particulate. Pre-S epitopes inserted at the N-terminus through a precore polylinker, the truncated C-terminus and at the internal position between HBcAg amino acids 75 and 81 were accessible on the particle surface. N-terminal fusions required the presence of the linker sequence to become surface accessible and immunogenic. Fusions to the N- and C-termini of HBcAg did not interfere with HBcAg antigenicity and immunogenicity. In contrast, insertion at the internal site abrogated recognition of HBcAg by five out of six monoclonal antibodies and diminished recognition by human polyclonal anti-HBc antibodies as well as HBcAg immunogenicity. A pre-S(2) sequence fused to the C-terminus of HBcAg was surface accessible and weakly immunogenic. Pre-S(1) sequences fused to the N-terminus through a precore linker were surface accessible and highly immunogenic. The same sequence fused to the core methionine was not surface accessible or immunogenic. Insertion of the same pre-S(1) sequence at an internal position of HBcAg resulted in the most efficient anti-pre-S(1) antibody response.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1993

Role of T-cell tolerance in the persistence of hepatitis B virus infection.

Infants born to hepatitis B e antigen (HBeAg)-positive hepatitis B virus (HBV) carrier mothers invariably become persistently infected. To investigate the role of immunologic tolerance mechanisms in chronic infection of the newborn, we have generated HBeAg-expressing transgenic mice (B10.S-Tg31e). These mice were tolerant to both HBeAg and the nonsecreted HBcAg at the T-cell level. Furthermore, nontransgenic littermates born to HBeAg-expressing mothers showed lowered T-cell responses to HBc/HBe antigens, suggesting that tolerogenic HBeAg may cross the placenta. Tg mice did not produce antibody to HBeAg but did produce immunoglobulin M (IgM) antibodies to HBcAg via a T cell-independent pathway. The coexistence of tolerance to HBc/HBe T-cell determinants and production of antibody to HBcAg in vivo parallels the immunologic status of neonates born to carrier mothers. These observations suggest that expression of HBeAg may represent a viral strategy to guarantee persistence after perinatal infection. Further studies in F1 hybrid Tg mice (B10 x B10.S-Tg31e) illustrated that "self" tolerance to HBeAg is variable, depending on the major histocompatibility complex (MHC) genotype. A proportion of T cells recognizing e129-140 in the context of I-Ab evade induction of tolerance, persist in the periphery, and can be activated in vivo by a single injection of the 12 residue T-cell self-peptide. Furthermore, the self-reactive T cells can cooperate with self-reactive, HBeAg-specific B cells to mediate in vivo production of autoantibody sufficient to neutralize detection of the autoantigen in serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

The serology of chronic hepatitis B infection revisited.

The serology of chronic hepatitis B infection has been established through the use of commercial immunoassays to measure the structural antigens of the hepatitis B virus and their respective antibodies in serum. However, the commercial assays have not been designed to detect serum antibodies in the presence of an excess of circulating antigens. A series of serum samples from 200 HBeAg-positive, chronically infected hepatitis B patients with varying degrees of liver disease were analyzed using novel immunoassays designed to detect antibodies in the presence of circulating viral antigens. All patients, regardless of their liver disease, were seronegative for antibodies specific for the envelope antigens or the secreted nucleoprotein antigen (HBeAg) when the commercial assays were used. In contrast, virtually all chronically infected patients with liver disease and approximately 50% of patients without liver disease demonstrated anti-HBe and anti-envelope antibodies when sera were tested in the more sensitive immunoassays. Furthermore, asymptomatic patients could be serologically distinguished from symptomatic patients based on antibody fine specificity, titer, and IgG subclass. This study revealed that the majority of chronically infected hepatitis B patients produce a variety of antibodies for many years, and are not immunologically unresponsive, as suggested by the current assays.

Antibody Formation↗

PubMed1992

Use of anti-peptide antibodies for the design of antigen-specific immune complex assays.

A simple and sensitive method is described for the detection of circulating immune complexes (ICs) in an antigen-specific manner. The method is based on the use of anti-peptide antibodies as solid-phase capture reagents to bind antigen which is complexed to serum antibodies. The bound serum antibody is detected with a labelled second antibody. The method requires that the anti-peptide antibodies bind native protein efficiently, and that the anti-peptide antibodies do not compete with antibodies raised against the native protein which are involved in IC formation. Two anti-peptide antibodies specific for the hepatitis B surface antigen (HBsAg) and the hepatitis B e antigen (HBeAg), which possessed the requisite characteristics, were chosen as models for IC assay development. The solid-phase, anti-peptide based assays efficiently detected HBsAg and HBeAg-containing ICs in preformed antigen/antibody mixtures and in the serum of chronically infected hepatitis B patients.

Amino Acid Sequence↗

PubMed1992

The position of heterologous epitopes inserted in hepatitis B virus core particles determines their immunogenicity.

The nucleocapsid (HBcAg) of the hepatitis B virus (HBV) has been suggested as a carrier moiety for vaccine purposes. We investigated the influence of the position of the inserted epitope within hybrid HBcAg particles on antigenicity and immunogenicity. For this purpose, genes coding for neutralizing epitopes of the pre-S region of the HBV envelope proteins were inserted at the amino terminus, the amino terminus through a precore linker sequence, the truncated carboxy terminus, or an internal site of HBcAg by genetic engineering and were expressed in Escherichia coli. All purified hybrid HBc/pre-S polyproteins were particulate. Amino- and carboxy-terminal-modified hybrid HBc particles retained HBcAg antigenicity and immunogenicity. In contrast, insertion of a pre-S(1) sequence between HBcAg residues 75 and 83 abrogated recognition of HBcAg by 5 of 6 anti-HBc monoclonal antibodies and diminished recognition by human polyclonal anti-HBc. Predictably, HBcAg-specific immunogenicity was also reduced. With respect to the inserted epitopes, a pre-S(1) epitope linked to the amino terminus of HBcAg was not surface accessible and not immunogenic. A pre-S(1) epitope fused to the amino terminus through a precore linker sequence was surface accessible and highly immunogenic. A carboxy-terminal-fused pre-S(2) sequence was also surface accessible but weakly immunogenic. Insertion of a pre-S(1) epitope at the internal site resulted in the most efficient anti-pre-S(1) antibody response. Furthermore, immunization with hybrid HBc/pre-S particles exclusively primed T-helper cells specific for HBcAg and not the inserted epitope. These results indicate that the position of the inserted B-cell epitope within HBcAg is critical to its immunogenicity.

Animals↗

PubMed1991

Autoantibody production in hepatitis B e antigen transgenic mice elicited with a self T-cell peptide and inhibited with nonself peptides.

Studies in hepatitis B e antigen (HBeAg)-expressing transgenic mice indicate that self tolerance to two T-cell determinants on the same transgenic self molecule can differ markedly. The dominant T-cell site on HBeAg is tolerogenic, whereas a proportion of T cells recognizing a second T-cell site evade tolerance induction, persist in the periphery, and can be activated in vivo by a single injection of a 12-residue T-cell self peptide. The self-reactive T cells mediate in vivo autoantibody production sufficient to neutralize detection of the autoantigen in serum. Furthermore, autoantibody production can be inhibited by nonself peptides that compete with the self peptide for binding to major histocompatibility complex molecules. This model illustrates that T cells specific for an immunogenic T-cell site on a nonsequestered autoantigen can escape tolerance induction and, more importantly, can mediate autoreactivity in vivo. Furthermore, these results suggest that synthetic T-cell sites may be useful as immunotherapeutic agents for the purpose of circumventing nonresponse to HBeAg during persistent hepatitis B virus infection.

Amino Acid Sequence↗

PubMed1991

Immune response to hepatitis B virus proteins: relevance of the murine model.

The experimental murine models offer unique opportunities to study the genetic, cellular, and molecular basis for variable immune responsiveness to HBV-encoded antigens. The mouse has provided a means of studying the immunogenicity of the pre-S regions of HBsAg and has elucidated the independent H-2-linked genes regulating antibody production to pre-S and S region determinants. The ability to circumvent genetic nonresponsiveness has implications for the design of future HBV vaccines. Mice also afforded the opportunity to examine the ability of HBcAg to activate B cells directly, and to prime Th cells capable of eliciting antibody to envelope proteins. These observations have potential clinical relevance, implications for vaccine design, and may explain the ability of HBcAg vaccination to protect against HBV infection. The murine system ha also facilitated the mapping of T-cell and B-cell recognition sites within HBV proteins, which at least conceptually enhances the prospects for development of a synthetic HBV vaccine. Antibody-binding sites appear to be similar in humans and mice; the extent to which their T-cell repertoires overlap is not known. However, the chemical and structural constraints imposed on T-cell antigenicity, and the fact that MHC-encoded class II molecules and the cellular mechanisms mediating T-cell recognition are conserved across species, make such overlaps appear likely. Furthermore, the ability to generate transgenic mice that express the various HBV proteins has yielded important insights into possible immunopathogenic mechanism and immunologic tolerance mechanisms that may predispose to chronic infection.

Animals↗

PubMed1991

Promoter-specific transactivation of hepatitis B virus transcription by a glutamine- and proline-rich domain of hepatocyte nuclear factor 1.

The cloned transcription factor hepatocyte nuclear factor 1 (HNF1) transactivates transcription from the hepatitis B virus (HBV) large surface antigen promoter but does not influence the transcriptional activities of the other three HBV promoters. This indicates that this transcription factor can differentially influence the activities of the HBV promoter. By using a transient-transfection system, the major domain of the HNF1 polypeptide involved in transcriptional activation of the large surface antigen promoter in the human hepatoma cell line HepG2.1 has been mapped to a region that is rich in glutamine and proline residues (9 of 18) and is different from the previously identified regions of this factor responsible for in vitro transcriptional activation of a promoter containing human albumin promoter HNF1 binding sites. The human albumin promoter HNF1 binding site mediates transcriptional activation through the same HNF1 polypeptide domain as the HBV large surface antigen promoter HNF1 binding site in transient-transfection assays with HepG2.1 cells, suggesting that HNF1 may possess multiple transcriptional activation domains.

Animals↗

PubMed1991

Hepatitis B virus core antigen has two nuclear localization sequences in the arginine-rich carboxyl terminus.

Expression of the hepatitis B virus core antigen (HBcAg) in mouse NIH 3T3 fibroblasts has been shown previously (A. McLachlan et al., J. Virol. 61:683-692, 1987) to result in the nuclear localization of this polypeptide. Since the carboxyl terminus of HBcAg contains four clusters of arginine residues which resemble nuclear localization sequences identified in other nuclear proteins, a series of carboxyl-terminus-truncated HBcAg polypeptides were expressed in mouse fibroblasts to examine the role of these sequences in the cellular localization of HBcAg. By immunofluorescence and cell fractionation analysis, it was demonstrated that regions of the HBcAg polypeptide including the most carboxyl-terminal (cluster 1) and amino-terminal (cluster 4) clusters of arginine residues represent distinct and independent nuclear localization sequences for this polypeptide. Substitution of a threonine residue for the second arginine residue in cluster 4 inactivates the nuclear localization signal in this region of the HBcAg polypeptide, demonstrating the importance of this residue to this signal sequence. However, HBcAg fails to accumulate in the nucleus only when both nuclear localization signal sequences are simultaneously deleted or disrupted by mutation. The possible significance of the nuclear localization sequences identified in the HBcAg polypeptide is discussed in the context of the role of the nucleocapsid in the hepatitis B virus life cycle.

Amino Acid Sequence↗

PubMed1991

Complex regulation of transcription from the hepatitis B virus major surface antigen promoter in human hepatoma cell lines.

A detailed mutational analysis of the regulatory DNA sequence elements that control expression of the hepatitis B virus major surface antigen gene was performed in the human hepatoma cell lines HepG2.1 and Huh7, using transient transfection assays. Seven regions (A to G) of the major surface antigen promoter located within 200 nucleotides of the RNA initiation site have been identified which influence the level of transcription from this promoter. The three distal regions (A to C), located between -188 and -68, appear to possess a level of redundancy in their ability to influence the transcriptional activity from the major surface antigen promoter. The simultaneous deletion of regions A, B, and C resulted in an approximately fourfold reduction in transcription from the major surface antigen promoter. Region D, located between -67 and -49, is an essential element of the major surface antigen promoter. The three proximal regions (E to G) are located within 45 nucleotides of the major transcription initiation site. Region E prevents the negative influence of region F and can compensate for the effect of mutation of region G on transcription from the major surface antigen promoter. Region G can compensate for the effect of the loss of a functional region E sequence on the transcriptional activity of the major surface antigen promoter only in the absence of a functional region F sequence. These results imply that the level of expression of the major surface antigen gene is controlled by the complex interplay between a minimum of six transcription factors which activate and one transcription factor which represses transcription from this gene.

Base Sequence↗

PubMed1990

Hepatitis B virus nucleocapsid/pre-S2 fusion proteins expressed in attenuated Salmonella for oral vaccination.

Hybrid HBV nucleocapsid-pre-S(2) fusion proteins were stably expressed in several aromatic-dependent attenuated Salmonella typhimurium and Salmonella dublin strains. When these live recombinant bacteria were administered i.p. to BALB/c mice they induced high titer anti-hepatitis B virus core Ag (HBc) and detectable anti-pre-S2 serum antibodies. Upon oral feeding of the recombinant salmonellae to mice, the rate of seroconversion to anti-HBc was dependent on the salmonella strain used. With the best carrier strain high titer anti-HBc antibodies and lower titer anti-pre-S2 serum IgG antibodies were observed two weeks after a single oral immunization. The Ig class and IgG subclass distribution of anti-HBc antibodies after i.p. and oral immunization is consistent with the induction of functional T cell help.

Administration, Oral↗

PubMed1990

Importance of subtype in the immune response to the pre-S(2) region of the hepatitis B surface antigen. I. T cell fine specificity.

Previous studies of murine T cell recognition of the pre-S(2) region of the hepatitis B surface Ag (HBsAg) identified high (H-2b,d,q), intermediate (H-2s,k), and low to nonresponder (H-2f) haplotypes. However, these studies utilized the y subtype of HBsAg. The purpose of this study was to examine the influence of viral subtype on T cell recognition of the pre-S(2) region and to identify specific T cell recognition sites in a panel of H-2 congenic strains. Immunization with pre-S(2) containing HBsAg particles of the d and y subtypes indicated that T cell recognition of the pre-S(2) region is predominantly subtype-specific in murine strains of eight different H-2 haplotypes. Furthermore, the B10.M strain (H-2f) classified as a T cell nonresponder to the y subtype of the pre-S(2) region responds efficiently to the d subtype, indicating that pre-S(2) responder status can be subtype-dependent as well as subtype-specific. Studies using a truncated pre-S(2) polypeptide and synthetic peptides illustrated that the C-terminal sequence (p148-174) of the pre-S(2) region is the dominant focus of T cell recognition in multiple murine strains. Specifically, 17 distinct T cell recognition sites were defined within the C-terminal half of the pre-S(2) region. The fine specificity of T cell recognition of the pre-S(2) region was dependent on the H-2 haplotype of the responding strain. T cell recognition of all 17 sites was subtype specific, which is consistent with the fact that the C-terminal sequence is highly polymorphic between the d and y subtypes of the pre-S(2) region. Lastly, it was shown that the ability of synthetic peptides to elicit T cells cross-reactive with the native pre-S(2) region was variable and depended on the nature of the immunizing peptide. The pre-S(2)-containing HBsAg vaccines currently in clinical trials are composed of ra single subtype, either d or y. The results of this study suggest that both subtypes should be incorporated to increase the frequency of T cell responders to the pre-S(2) region, and to insure Th cell memory relevant to infection with hepatitis B virus of either the d or y subtypes.

Amino Acid Sequence↗

PubMed1990

Importance of subtype in the immune response to the pre-S(2) region of the hepatitis B surface antigen. II. Synthetic Pre-S(2) immunogen.

One purpose of this study was to examine the influence of viral subtype on in vivo antibody production to the pre-S(2) region of the hepatitis B surface Ag. Immunization with hepatitis B surface Ag particles containing the pre-S(2) region of the d or y subtypes identified the B10.M (H-2f) strain as an antibody nonresponder to the pre-S(2) and S regions after immunization with the y subtype, but as an antibody responder to the pre-S(2) and S regions after immunization with the d subtype. Both the S region and pre-S(2) region-specific antibody responses emanated from pre-S(2)/d-specific Th cell function because B10.M mice are T cell nonresponsive to the S region of both subtypes. Although responder/nonresponder status of the B10.M strain was dependent on the pre-S(2) subtype used for immunization, the anti-pre-S(2) antibody produced was totally cross-reactive on both subtypes. This is consistent with the conserved nature of the dominant pre-S(2) antibody-binding site and the highly polymorphic nature of the pre-S(2) sequence that represents the focus of T cell recognition. These data suggest that, to fully benefit from the inclusion of pre-S(2) region sequences, third generation hepatitis B virus vaccines should contain both the d and y subtype sequences of the pre-S(2) region to increase the frequency of pre-S(2) and S-specific antibody responses and to insure Th cell memory relevant to both viral subtypes. A second purpose of this study was to "design" a synthetic pre-S(2) immunogen based on combining the dominant B and T cell recognition sites into a single peptide. A composite peptide consisting of the dominant T cell recognition sequence p151-174 positioned N-terminal to the dominant B cell site p133-143 (i.e., p151-174(133-143] yielded an effective pre-S(2) synthetic immunogen. Interestingly, the orientation of the T and B cell determinants and the context of the T cell site within the larger composite peptide influenced both antibody fine specificity and T cell fine specificity.

Amino Acid Sequence↗

PubMed1990

Is a function of the secreted hepatitis B e antigen to induce immunologic tolerance in utero?

Infants born to hepatitis B virus carrier mothers, who express a secreted form of the nucleocapsid antigen designated HBeAg, invariably become persistently infected. To investigate the role of immunologic tolerance mechanisms in chronic infection of the newborn, we have generated HBeAg-expressing transgenic mice. HBeAg-expressing transgenic mice were tolerant to both HBeAg and the nonsecreted nucleocapsid (hepatitis B cor antigen/HBcAg) at the T-cell level. Transgenic mice did not produce antibody to HBeAg but did produce anti-HBc antibody in vivo and in vitro. The coexistence of tolerance to HBc/HBe T-cell determinants and anti-HBc antibody production in vivo parallels the immunologic status of neonates born to carrier mothers. It was also demonstrated that the maintenance of T-cell tolerance to HBcAg/HBeAg required the continued presence of the tolerogen and in its absence persisted for less than 16 weeks. The reversibility of T-cell tolerance to HBcAg/HBeAg may explain the inverse correlation between age of infection and rates of viral persistence. These observations suggest that a function of the HBeAg may be to induce immunologic tolerance in utero. Expression of HBeAg may represent a viral strategy to guarantee persistence after perinatal infection.

Animals↗