Modulation of Early β-Defensin-2 Production as a Mechanism Developed by Type I Toxoplasma gondii To Evade Human Intestinal Immunity▿†

We investigated the early innate immune responses induced in human intestinal epithelial cells (IEC) by the three defined Toxoplasma gondii genotype strains. Transcriptome analysis revealed that among differentially expressed genes, β-defensins distinguished the most IEC infected by fast- or slow-replicating T. gondii genotypes. Although β-defensin 1 and 3 genes were not expressed in host cells at early time points postinfection, the slow-replicating type II and III parasites induced high levels of β-defensin 2 gene expression. Notably, no β-defensin 2 gene expression occurred early after infection with the fast-replicating type I parasite. However, activation of this gene in IEC by poly(I:C) treatment prior to infection substantially decreased parasite viability, and pretreatment of parasites with synthetic β-defensin 2 significantly reduced their infectivity of IEC. These findings strongly support the modulation of early β-defensin 2 expression as a mechanism used by type I T. gondii parasites to mediate immune evasion

Partial Reconstitution of the CD4(+)-T-Cell Compartment in CD4 Gene Knockout Mice Restores Responses to Tuberculosis DNA Vaccines

Reactivation tuberculosis (TB) is a serious problem in immunocompromised individuals, especially those with human immunodeficiency virus (HIV) coinfection. The adaptive immune response mediated by CD4(+) and CD8(+) T cells is known to confer protection against TB. Hence, vaccines against TB are designed to activate these two components of the immune system. Anti-TB DNA vaccines encoding the immunodominant proteins Ag85A, Ag85B, and PstS-3 from Mycobacterium tuberculosis are ineffective in mice lacking CD4(+) T cells (CD4(−/−) mice). In this study, we demonstrate that reconstitution of the T-cell compartment in CD4(−/−) mice restores vaccine-specific antibody and gamma interferon (IFN-γ) responses to these DNA vaccines. The magnitude of the immune responses correlated with the extent of reconstitution of the CD4(+)-T-cell compartment. Reconstituted mice vaccinated with DNA encoding PstS-3, known to encode a dominant D(b)-restricted CD8(+)-T-cell epitope, displayed CD8(+)-T-cell responses not observed in CD4(−/−) mice. M. tuberculosis challenge in reconstituted mice led to the extravasation of IFN-γ-producing CD4(+) and CD8(+) T cells into lungs, the primary site of bacterial replication. Importantly, a reconstitution of 12 to 15% of the CD4(+)-T-cell compartment resulted in Ag85B plasmid DNA-mediated protection against a challenge M. tuberculosis infection. Our findings provide evidence that anti-TB DNA vaccines could be effective in immunodeficient individuals after CD4(+)-T-lymphocyte reconstitution, as may occur following antiretroviral therapy in HIV(+) patients

Induction of in vivo functional Db-restricted cytolytic T cell activity against a putative phosphate transport receptor of Mycobacterium tuberculosis

Using plasmid vaccination with DNA encoding the putative phosphate transport receptor PstS-3 from Mycobacterium tuberculosis and 36 overlapping 20-mer peptides spanning the entire PstS-3 sequence, we determined the immunodominant Th1-type CD4+ T cell epitopes in C57BL/10 mice, as measured by spleen cell IL-2 and IFN-γ production. Furthermore, a potent IFN-γ-inducing, Db-restricted CD8+ epitope was identified using MHC class I mutant B6.C-H-2bm13 mice and intracellular IFN-γ and whole blood CD8+ T cell tetramer staining. Using adoptive transfer of CFSE-labeled, peptide-pulsed syngeneic spleen cells from naive animals into DNA vaccinated or M. tuberculosis-infected recipients, we demonstrated a functional in vivo CTL activity against this Db-restricted PstS-3 epitope. IFN-γ ELISPOT responses to this epitope were also detected in tuberculosis-infected mice. The CD4+ and CD8+ T cell epitopes defined for PstS-3 were completely specific and not recognized in mice vaccinated with either PstS-1 or PstS-2 DNA. The H-2 haplotype exerted a strong influence on immune reactivity to the PstS-3 Ag, and mice of the H-2b, p, and f haplotype produced significant Ab and Th1-type cytokine levels, whereas mice of H-2d, k, r, s, and q haplotype were completely unreactive. Low responsiveness against PstS-3 in MHC class II mutant B6.C-H-2bm12 mice could be overcome by DNA vaccination. IFN-γ-producing CD8+ T cells could also be detected against the Db-restricted epitope in H-2p haplotype mice. These results highlight the potential of DNA vaccination for the induction and characterization of CD4+ and particularly CD8 + T cell responses against mycobacterial Ags.SCOPUS: ar.jinfo:eu-repo/semantics/publishe