Chronicity after infection with the hepatitis B virus (HBV) can occur for a variety of reasons. However, once established, chronicity may be maintained by high levels of viral proteins circulating in the serum. To examine the characteristics of T cells capable of coexisting with the secreted hepatitis B e antigen (HBeAg), T-cell receptor (TCR) transgenic (Tg) mice were produced. To ensure that HBeAg-specific T cells would not be deleted in the presence of serum HBeAg, the TCR ␣-and ␤-chain genes used to produce the TCR-Tg mice were derived from T-cell hybridomas produced from immunizing HBeAg-Tg mice. A TCR-Tg lineage (11/4-12) was produced that possessed a high frequency (ϳ67%) of CD4 ؉ T cells that expressed a Tg TCR specific for the HBeAg. As predicted, when 11/4-12 TCR-Tg mice were bred with HBeAg-Tg mice no deletion of the HBeAgspecific CD4؉ The nucleoprotein of the hepatitis B virus (HBV) exists in two structural forms. The particulate nucleocapsid (hepatitis B c antigen [HBcAg]), which encapsulates the viral genome, and a monomeric secreted form (HBeAg). We have postulated that maternally derived HBeAg traverses the placenta and acts as a tolerogen in utero, thereby predisposing perinatally infected babies to chronic infection (14). Neonatal tolerance studies in mice demonstrated that tolerance to the HBeAg was major histocompatibility complex (MHC) dependent inasmuch as the CD4 ϩ T cells of H-2 s mice were very sensitive to tolerance induction by HBeAg, whereas some proportion of CD4 ϩ T cells of H-2 b mice were resistant to neonatal tolerance induction with HBeAg (15). These studies were extended by the production of HBeAg-expressing transgenic (Tg) mice. The CD4 ϩ T cells of HBeAg-Tg mice on an H-2 s background (B10.S) were highly tolerant, yet CD4 ϩ T cells in HBeAg-Tg mice on an H-2 b background (B10) were incompletely tolerant (16). Incomplete tolerance in H-2 b HBeAg-Tg mice permitted functional studies of the HBeAg-specific CD4 ϩ T-cell repertoire that escaped tolerance and coexisted with circulating HBeAg. These studies revealed that HBeAg-specific CD4 ϩ T cells that evaded tolerance induction in HBeAg-Tg H-2 b mice were of relatively low avidity, possessed a unique fine specificity pattern, and tended to belong to the Th2 subset (17).In order to further examine HBeAg-specific CD4 ϩ T cells that can coexist with circulating HBeAg and remain functional in vivo, we produced mice transgenic for T-cell receptors (TCR) specific for HBeAg. First, T-cell hybridomas were produced by immunizing B10 wild-type (ϩ/ϩ) mice or HBeAg-Tg (B10 e/e) mice with HBeAg. These immunizations yielded 100 T-cell hybridomas from the B10 ϩ/ϩ mice and 13 T-cell hybridomas from the B10 e/e mice (17). The TCR-␣/␤ genes derived from selected HBeAg-specific T-cell hybridomas were sequenced and inserted into T-cell expression shuttle vectors for use in the generation of TCR-␣/␤-Tg mice.The TCR-␣/␤-Tg lineage 11/4-12, derived from HBeAg-Tg (B10 e/e) mice, is the subject of this report. A second TCR-␣/ ␤-Tg lineage, 8/3-11, derived...

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