SARS coronavirus nucleocapsid immunodominant T-cell epitope cluster is common to both exogenous recombinant and endogenous DNA-encoded immunogens

Abstract

Correspondence between the T-cell epitope responses of vaccine immunogens and those of pathogen antigens is critical to vaccine efficacy. In the present study, we analyzed the spectrum of immune responses of mice to three different forms of the SARS coronavirus nucleocapsid (N): (1) exogenous recombinant protein (N-GST) with Freund's adjuvant; (2) DNA encoding unmodified N as an endogenous cytoplasmic protein (pN); and (3) DNA encoding N as a LAMP-1 chimera targeted to the lysosomal MHC II compartment (p-LAMP-N). Lysosomal trafficking of the LAMP/N chimera in transfected cells was documented by both confocal and immunoelectron microscopy. The responses of the immunized mice differed markedly. The strongest T-cell IFN-gamma and CTL responses were to the LAMP-N chimera followed by the pN immunogen. In contrast, N-GST elicited strong T cell IL-4 but minimal IFN-gamma responses and a much greater antibody response. Despite these differences, however, the immunodominant T-cell ELISpot responses to each of the three immunogens were elicited by the same N peptides, with the greatest responses being generated by a cluster of five overlapping peptides, N76-114, each of which contained nonameric H2d binding domains with high binding scores for both class I and, except for N76-93, class II alleles. These results demonstrate that processing and presentation of N, whether exogenously or endogenously derived, resulted in common immunodominant epitopes, supporting the usefulness of modified antigen delivery and trafficking forms and, in particular, LAMP chimeras as vaccine candidates. Nevertheless, the profiles of T-cell responses were distinctly different. The pronounced Th-2 and humoral response to N protein plus adjuvant are in contrast to the balanced IFN-gamma and IL-4 responses and strong memory CTL responses to the LAMP-N chimera.

Rabies DNA vaccine: No impact of MHC Class I and Class II targeting sequences on immune response and protection against lethal challenge

“…In an effort to develop an optimal DNA vaccine against rabies virus, this study was aimed at evaluating the immune enhancement potential of different antigen targeting strategies to selectively improve responses mediated by CD8 + and CD4 + T lymphocytes and by antibodies, induced after intramuscular immunization with DNA plasmids. Addition of target sequences like TPA, LAMP-1, UQ have been employed for vaccination against various pathogens including SARS coronavirus [35]; Dengue virus [36]; Orthopox virus Fig. 7.…”

“…They inferred that TM domain is critical for proper folding of protein otherwise the critical epitopes may get disrupted [30]. Gupta et al also reported that DNA vaccine encoding rabies virus glycoprotein lacking transmembrane domain though enhances antibody response but does not confer protection [35]. Therefore, we retained the TM domain in our DNA vaccine constructs and utilized full gene for targeting strategies.…”

Immune responses to T-cell epitopes of SARS CoV-N protein are enhanced by N immunization with a chimera of lysosome-associated membrane protein

“…The luminal domain of LAMP is then integrated into the lysosome. [10][11][12][13][14][15][16][17] Consequently, one strategy commonly adopted by our group [18][19][20][21][22][23][24][25] is to insert the target DNA into LAMP as a LAMP/ antigen chimera. In addition, many other laboratories have reported that LAMP targeting could greatly enhance the immune response against a number of antigens.…”

A systematic bioinformatics approach for selection of epitope-based vaccine targets

“…promiscuous T-cell epitopes may be localized in clusters, as reported in studies of HIV-1 [29][30][31][32] and the outer membrane of Chlamydia trachomatis [33], among others [34,35]. The clusters are also ideal for developing epitopebased vaccines because they contain multiple promiscuous epitopes.…”