IL-17 and IL-22 elicited by a DNA vaccine encoding ROP13 associated with protection against Toxoplasma gondii in BALB/c mice

Toxoplasma gondii, an intracellular parasitic protozoan, is capable of infecting man and all warm-blooded animals. Cell-mediated immunity is vital in mounting protective responses against T. gondii infection. Recent studies have shown that T-helper (Th) 17 responses may play a key role in parasite control. In this current study, we constructed a DNA vaccine encoding T. gondii ROP13 in a pcDNA vector. Groups of BALB/c mice were immunized intramuscularly with pcROP13 or controls and challenged with the RH strain of T. gondii. The results showed that immunization with pcROP13 could elicit an antibody response against T. gondii. The expression of the canonical Th17 cytokines, interleukin (IL)-17 and IL-22, were significantly increased after immunization with pcROP13 compared with control groups ( p < 0.05). Furthermore, vaccination resulted in a significant decrease in parasite load ( p < 0.05). The induction of Th17 related cytokines, using a ROP13 DNA vaccine, against T. gondii should be considered as a potential vaccine approach for the control of toxoplasmosis.

Wuchereria bancrofti filaria activates human dendritic cells and polarizes T helper 1 and regulatory T cells via toll-like receptor 4

Interaction between innate immune cells and parasite plays a key role in the immunopathogenesis of lymphatic filariasis. Despite being professional antigen presenting cells critical for the pathogen recognition, processing and presenting the antigens for mounting T cell responses, the dendritic cell response and its role in initiating CD4+ T cell response to filaria, in particular Wuchereria bancrofti, the most prevalent microfilaria is still not clear. Herein, we demonstrate that a 70 kDa phosphorylcholine-binding W. bancrofti sheath antigen induces human dendritic cell maturation and secretion of several pro-inflammatory cytokines. Further, microfilarial sheath antigen-stimulated dendritic cells drive predominantly Th1 and regulatory T cell responses while Th17 and Th2 responses are marginal. Mechanistically, sheath antigen-induced dendritic cell maturation, and Th1 and regulatory T cell responses are mediated via toll-like receptor 4 signaling. Our data suggest that W. bancrofti sheath antigen exploits dendritic cells to mediate distinct CD4+ T cell responses and immunopathogenesis of lymphatic filariasis.

TGFβ-activation by dendritic cells drives Th17 induction and intestinal contractility and augments the expulsion of the parasite Trichinella spiralis in mice

Helminths are highly prevalent metazoan parasites that infect over a billion of the world's population. Hosts have evolved numerous mechanisms to drive the expulsion of these parasites via Th2-driven immunity, but these responses must be tightly controlled to prevent equally devastating immunopathology. However, mechanisms that regulate this balance are still unclear. Here we show that the vigorous Th2 immune response driven by the small intestinal helminth Trichinella spiralis, is associated with increased TGFβ signalling responses in CD4+ T-cells. Mechanistically, enhanced TGFβ signalling in CD4+ T-cells is dependent on dendritic cell-mediated TGFβ activation which requires expression of the integrin αvβ8. Importantly, mice lacking integrin αvβ8 on DCs had a delayed ability to expel a T. spiralis infection, indicating an important functional role for integrin αvβ8-mediated TGFβ activation in promoting parasite expulsion. In addition to maintaining regulatory T-cell responses, the CD4+ T-cell signalling of this pleiotropic cytokine induces a Th17 response which is crucial in promoting the intestinal muscle hypercontractility that drives worm expulsion. Collectively, these results provide novel insights into intestinal helminth expulsion beyond that of classical Th2 driven immunity, and highlight the importance of IL-17 in intestinal contraction which may aid therapeutics to numerous diseases of the intestine.

Modulation of CD4+ and CD8+ T Cell Function and Cytokine Responses in Strongyloides stercoralis Infection by Interleukin-27 (IL-27) and IL-37

Strongyloides stercoralis infection is associated with diminished antigen-specific Th1- and Th17-associated responses and enhanced Th2-associated responses. Interleukin-27 (IL-27) and IL-37 are two known anti-inflammatory cytokines that are highly expressed in S. stercoralis infection. We therefore wanted to examine the role of IL-27 and IL-37 in regulating CD4+ and CD8+ T cell responses in S. stercoralis infection. To this end, we examined the frequency of Th1/Tc1, Th2/Tc2, Th9/Tc9, Th17/Tc17, and Th22/Tc22 cells in 15 S. stercoralis-infected individuals and 10 uninfected individuals stimulated with parasite antigen following IL-27 or IL-37 neutralization. We also examined the production of prototypical type 1, type 2, type 9, type 17, and type 22 cytokines in the whole-blood supernatants. Our data reveal that IL-27 or IL-37 neutralization resulted in significantly enhanced frequencies of Th1/Tc1, Th2/Tc2, Th17/Tc17, Th9, and Th22 cells with parasite antigen stimulation. There was no induction of any T cell response in uninfected individuals following parasite antigen stimulation and IL-27 or IL-37 neutralization. Moreover, we also observed increased production of gamma interferon (IFN-γ), IL-5, IL-9, IL-17, and IL-22 and decreased production of IL-10 following IL-27 and IL-37 neutralization and parasite antigen stimulation in whole-blood cultures. Thus, we demonstrate that IL-27 and IL-37 limit the induction of particular T cell subsets along with cytokine responses in S. stercoralis infections, which suggest the importance of IL-27 and IL-37 in immune modulation in a chronic helminth infection.

IL-22 mediates host defense against an intestinal intracellular parasite in the absence of IFN-γ at the cost of Th17-driven immunopathology

The roles of Th1 and Th17 responses as mediators of host protection and pathology in the intestine are the subjects of intense research. In this study, we investigated a model of intestinal inflammation driven by the intracellular apicomplexan parasite Eimeria falciformis. Although IFN-γ was the predominant cytokine during E. falciformis infection in wild-type mice, it was found to be dispensable for host defense and the development of intestinal inflammation. E. falciformis-infected IFN-γR(-/-) and IFN-γ(-/-) mice developed dramatically exacerbated body weight loss and intestinal pathology, but they surprisingly harbored fewer parasites. This was associated with a striking increase in parasite-specific IL-17A and IL-22 production in the mesenteric lymph nodes and intestine. CD4(+) T cells were found to be the source of IL-17A and IL-22, which drove the recruitment of neutrophils and increased tissue expression of anti-microbial peptides (RegIIIβ, RegIIIγ) and matrix metalloproteinase 9. Concurrent neutralization of IL-17A and IL-22 in E. falciformis-infected IFN-γR(-/-) mice resulted in a reduction in infection-induced body weight loss and inflammation and significantly increased parasite shedding. In contrast, neutralization of IL-22 alone was sufficient to increase parasite burden, but it had no effect on body weight loss. Treatment of an E. falciformis-infected intestinal epithelial cell line with IFN-γ, IL-17A, or IL-22 significantly reduced parasite development in vitro. Taken together, to our knowledge these data demonstrate for the first time an antiparasite effect of IL-22 during an intestinal infection, and they suggest that IL-17A and IL-22 have redundant roles in driving intestinal pathology in the absence of IFN-γ signaling.

Alteration of helper T-cell related cytokine production in splenocytes during Trichinella spiralis infection

Infection by Trichinella spiralis takes place in two distinct phases: one is the intestinal phase and the other is the muscle phase. To evaluate alterations in cytokine production during a T. spiralis infection, we periodically assessed the cytokine production of splenocytes in mice after infection (AI). The levels of Th2-related cytokines immediately increased after the initiation of T. spiralis larval intestinal invasion (1 week AI). These early elevations in the Th2 response might be associated with the innate immune responses of intestine epithelial cells against T. spiralis larval invasion. IL-4 and IL-13 levels reached a peak prior to the initiation of nurse cell formation (2 weeks AI). Additionally, all Th17-related cytokines, except for IL-17, increased slightly until 2 weeks AI. However, expression levels for all of the Th2 and Th17-related cytokines began to decrease after the initiation of nurse cell formation and reached basal levels at 4 weeks AI, except for IL-5. At the same time, the CD4(+)CD25(+)Foxp3(+) T (regulatory T, T(reg)) cell population increased significantly in the spleen. Additionally, the number of cells in the peripheral lymph nodes increased. In conclusion, T. spiralis larva intestinal invasion induced the production of Th2 and Th17 cell-related cytokines, and the cytokines decreased with T(reg) cell-related cytokine.