Breaking the Non-Responsiveness of C57BL/6 Mice to the Malarial Antigen EB200 - The Role of Carrier and Adjuvant Molecules

Eimeria tenella heat shock protein 70 enhances protection of recombinant microneme protein MIC2 subunit antigen vaccination against E. tenella challenge

Heat shock proteins have been reported to stimulate the immune system via innate receptors. Our study found that the novel immunopotentiator, Eimeria tenella (E. tenella) heat shock protein 70 (HSP70), enhanced protective immunity elicited by E. tenella antigen microneme protein 2 (EtMIC2) against avian coccidiosis. It demonstrated that the expression of TLR2 and TLR4 were strongly upregulated in EtHSP70 and EtMIC2 plus EtHSP70 stimulated chicken embryo fibroblasts (CEF) compared with untreated controls and EtMIC2 alone. In addition, the same treatment induced high levels of interleukin (IL)-12 and interferon (IFN)-γ that are critical cytokines of innate immunity. In vivo experiments involved using broiler chickens subcutaneously immunized with EtMIC2 alone or EtMIC2 plus EtHSP70 at 7 and 14 days post-hatch, which were then orally challenged with live E. tenella at 7 days following secondary immunization. Body weight gains, cecal lesion scores, fecal oocyst shedding, serum antibody responses against MIC2, and intestinal cytokine transcript levels were assessed as measures of protective immunity. Chickens immunized with EtMIC2 plus EtHSP70 showed increased body weight gains, decreased oocyst shedding, increased serum antibody responses, and high levels of IL-12, IFN-γ, and IL-17 compared with the EtMIC2 only or control groups. Moreover, chickens immunized with EtHSP70 alone showed significantly protective effect against E. tenella infection. In summary, this study provides the first evidence of the immunoenhancing activities of EtHSP70 in poultry.

Monocyte-derived dendritic cells from chagasic patients vs healthy donors secrete differential levels of IL-10 and IL-12 when stimulated with a protein fragment of Trypanosoma cruzi heat-shock protein-70

We analyzed the effect of the truncated heat-shock protein 70 from Trypanosoma cruzi on maturation of human dendritic cells (DCs) derived from monocytes of peripheral blood mononuclear cells from healthy donors and chagasic patients. The results show that the T-HSP70 is capable of maturing human DCs inducing an increase in the expression level of the CD83, CD86 and human leukocyte antigen-DR surface markers, as well as in the secretion of interleukin (IL)-12, tumor necrosis factor-alpha (TNF-alpha) and IL-6 cytokines. Results also show the existence of a differential functional activity of matured DCs from chagasic patients vs healthy donors in response to T-HSP70 protein and to HSP-70-derived A72 peptide, as only T-HSP70-matured DCs from chagasic patients have an enhanced secretion of IL-10 and a reduced secretion of IL-12. Moreover, the addition of A72 peptide to immature DCs from chagasic patients induced an increase in the percentage of cells expressing CD83 and CD86 molecules regarding to the expression level observed by cells from healthy donors. These findings suggest that T. cruzi HSP70 protein may induce a specific maturation profile on chagasic patients' DCs, which would favor the persistence of the parasite in the human host.

Microbial heat shock protein 70 stimulatory properties have different TLR requirements

Members of the HSP70 family have acquired special significance in immunity. Among other receptors, toll like receptor (TLR)-2 and TLR-4 have been suggested to be involved in HSP70-mediated signalling. We have previously shown that recombinant HSP70 from Trypanosoma cruzi and from Plasmodium falciparum function as adjuvants. In the present study, we have extended the study with other microbial HSPs (mHSPs) and considered of interest to assess the influence of TLR-2 and TLR-4 in mHSP-promoted responses. To test this, we evaluated the adjuvant effect of various mHSP molecules in TLR-2(-/-), TLR-4(-/-) and MyD88(-/-) mice. We show that all the mHSPs tested are strong adjuvants and induced IL-12 production by bone marrow macrophages. However, even within the same family, mHSPs induced different types of immune responses. Furthermore, the mHSPs tested, possess different requirements for signaling through TLRs. Interestingly, Tc70 was found to induce in vivo and in vitro responses in both TLR-2(-/-) and TLR-4(-/-) mice. Possible implications of our findings are taken up in the discussion section.

Enhancement of DNA vaccine potency by linkage of Plasmodium falciparum malarial antigen gene fused with a fragment of HSP70 gene

Finding an appropriate adjuvant for human vaccination is crucial. HSPs have been shown to act as adjuvants when coadministered with peptide antigens or given as fusion proteins. However, there is a potential risk of autoimmunity when using the complete molecules because HSPs are evolutionary conserved. To overcome this, we first evaluated the adjuvant effect of a less conserved fragment of Plasmodium falciparum HSP70 (Pf70C) as compared it to that of the whole HSP70 molecule from Trypanosoma cruzi (TcHSP70). We found that Pf70C exhibited similar adjuvant properties as the whole molecule. We then evaluated the adjuvant potential of Pf70C for the malarial antigen EB200 in a chimeric DNA construct. No appreciable levels of EB200 specific antibodies were detected in mice immunized with the DNA constructs only. However, the DNA immunization efficiently primed the immune system, as indicated by the strong Th-1 antibody response elicited by a subsequent boosting with the corresponding recombinant fusion proteins. In contrast, while no such priming effect was observed for ex vivo IFN-gamma production, stimulation with the HSP chimeric fusion protein induced an enhanced secretion of IFN-gamma in vitro as compared to other proteins used. Our results emphasize the potential of HSPs as adjuvants in subunit vaccines.