Protective immunity against Mycobacterium tuberculosis induced by dendritic cells pulsed with both CD8(+)- and CD4(+)-T-cell epitopes from antigen 85A

Abstract

Immunization with DNA followed by modified vaccinia virus Ankara strain, both expressing the antigen 85A, induced both CD4(+)- and CD8(+)-T-cell responses in BALB/c mice. Following challenge with Mycobacterium tuberculosis, this prime-boost regimen produced protection equivalent to that conferred by Mycobacterium bovis BCG. Following immunization with dendritic cells pulsed with an antigen 85A CD4(+)- or CD8(+)-restricted epitope, alone or in combination, copresentation of both epitopes on the same dendritic cell was required for protection, demonstrating that induced CD8(+) T cells can play a protective role against tuberculosis.

Figures

FIG. 1.

Comparative immunogenicity results obtained by ex vivo gamma interferon Elispot assay for homologous and heterologous prime-boost immunization regimens. The bars indicate mean numbers of SFC per 106 splenocytes; the error bars indicate standard errors.

FIG. 2.

Mean log10 number of CFU per organ. The error bars indicate standard errors. In all experiments, BCG immunization conferred significant protection against challenge in the lungs and spleens. There were 10 to 15 mice per group in most experiments; in the experiments whose results are shown in panel B there were only 6 mice in the control group. Mice were challenged with 106 CFU (A) or 5 × 106 CFU (B and C). (C) DCs with no peptide (DC−) and Prime-boost immunization with the DDDM regimen conferred significant protection (P = 0.005) in the lungs, as did immunization with DCs pulsed with both the CD4+-T-cell (p15) and CD8+-T-cell (p11) epitopes from antigen 85A (P = 0.008). (B). DCs pulsed with either the CD4+ epitope alone or the CD8+ epitope alone did not confer protection, whereas DCs pulsed with both epitopes conferred significant protection in the lungs (P = 0.016) and spleens (P < 0.001). (C) DCs with no peptide (DC−) and DCs pulsed with the CD4+ epitope and the CD8+ epitope separately and then mixed prior to immunization [DC(11)+(15)] did not confer protection against challenge. DCs pulsed with both epitopes conferred significant protection in the lungs (P = 0.022).