Priming Biologically Active Antibody Responses Against an Isolated, Conformational Viral Epitope by DNA Vaccination

Abstract

The immunodominant, conformational “a” determinant of hepatitis B surface Ag (HBsAg) elicits Ab responses. We selectively expressed the Ab-binding, glycosylated, native a determinant (residue 120–147) of HBsAg in a fusion protein containing C-terminally the HBsAg fragment SII (residue 80–180) fused to a SV40 T-Ag-derived hsp73-binding 77 aa (T77) or non-hsp-binding 60 aa (T60) N terminus. A DNA vaccine encoding non-hsp-binding secreted T60-SII fusion protein-stimulated murine Ab responses with a similar efficacy as a DNA vaccine encoding the secreted, native, small HBsAg. A DNA vaccine encoding hsp73-binding, intracellular T77-SII fusion protein-stimulated murine Ab responses less efficiently but comparable to a DNA vaccine encoding the intracellular, native, large HBsAg. HBsAg-specific Abs elicited by either the T60-SII-expressing or the T77-SII-expressing DNA vaccine suppressed HBsAg antigenemia in transgenic mice that produce HBsAg from a transgene in the liver; hence, a biologically active B cell response cross-reacting with the native, viral envelope epitope was primed by both DNA vaccine constructs. HBsAg-specific Ab and CTL responses were coprimed when an S20–50 fragment (containing the immunodominant, Ld-binding epitope S28–39) of HBsAg was fused C-terminally to the pCI/T77-SII sequence (pCI/T77-SII-Ld DNA vaccine). Chimeric, polyepitope DNA vaccines encoding conformational, Ab-binding epitopes and MHC class I-binding epitopes can thus efficiently deliver antigenic information to different compartments of the immune system in an immunogenic way.

Enhanced Priming of Multispecific, Murine CD8+ T Cell Responses by DNA Vaccines Expressing Stress Protein-Binding Polytope Peptides

“…4). This confirms that the tight, noncovalent association between hsp73 and the viral DnaJ domain requires the intact 77-residue domain as described by us in other Ag systems (10,11,13,15,16). Hence, we have constructed DNA vaccines carrying the immunogenic pt10 domain, but differing in the level of expression and the association with hsp73.…”

“…The N-terminal domain of T-Ag required for hsp73 association is located within the T 77 (but not the T 60 ) fragment that hence contains the intact J domain (15). From this observation we derived a vector system for the efficient expression of hsp73-associated, chimeric proteins (12,13,(15)(16)(17). In this system the T-Ag-derived J domain is fused N-terminally to different sequences from heterologous viral Ags of different origins and lengths.…”

IL-20 Receptor 2 Signaling Down-Regulates Antigen-Specific T Cell Responses

“…The regulation of Ag-specific CD8 responses is therefore of major therapeutic interest (41)(42)(43)(44). In summary, we could show that IL-20R2 regulates T cell activation directly and attenuates Ag-specific CD8 responses.…”

Novel Protein and Poxvirus-Based Vaccine Combinations for Simultaneous Induction of Humoral and Cell-Mediated Immunity

“…MVA may achieve this adjuvant capability through induction of TNF-␣ and IL-6 (25) both of which have been shown to support plasma cell survival (30). It is unclear exactly how intracellular Ag expression is able to enhance Ab responses, although it is possible that HBsAg may be secreted from the infected cell (31). Alternatively, endogenous production of Ag may allow it to access an alternative route of processing and presentation, such as using nascent as well as recycling MHC class II molecules, which may enhance CD4 ϩ T cell responses.…”