Biology subjects

Ajendra, J.

Publications and source records attributed to Ajendra, J..

6 recordsLinked to original sources

bioRxiv2023

Eosinophils are an endogenous source of IL-4 during filarial infections and contribute to the development of an optimal T helper 2 response

Interleukin-4 (IL-4) is a central regulator of type 2 immunity, crucial for the defense against multicellular parasites like helminths. This study focuses on its roles and cellular sources during Litomosoides sigmodontis infection, a model for human filarial infections. Our research uncovers eosinophils as a major source of IL-4, especially during the early phase of filarial infection. Using dblGATA mice lacking eosinophil and subsequently eosinophil-derived IL-4, we reveal their profound impact on the Th2 response. Lack of eosinophils impact Th2 polarization and resulted in impaired type 2 cytokine production. Surprisingly, eosinophil deficiency had no impact on macrophage polarization and proliferation as well as on antibody production. These findings shed new light on IL-4 dynamics and eosinophil effector functions in filarial infections. AUTHOR SUMMARYFilarial nematodes can cause severe diseases like onchocerciasis and lymphatic filariasis, posing a significant public health challenge in tropical regions, putting over a billion people at risk. The WHO categorizes these infections as neglected tropical diseases and aims to eliminate onchocerciasis transmission and lymphatic filariasis as a public health issue by 2030. To achieve this goal, we need a better understanding of the protective immune responses involved. Eosinophils have been identified as a key immune cell type in the well-established murine model for filarial infection, Litomosoides sigmodontis. However, their precise roles and interactions with other components of the type 2 immune response remain unclear. Our study reveals that eosinophils play a crucial role as a primary source of interleukin-4, the central cytokine in type 2 immunity. By using dblGATA mice, we found that the absence of eosinophils resulted in a reduced T helper 2 response but did not impact the alternative activation of macrophages or antibody production. In summary, our research uncovers an underappreciated function of eosinophils and their significant influence on type 2 immune responses.

immunology↗

bioRxiv2022

IL-17A promotes epithelial cell IL-33 production during nematode lung migration

The early migratory phase of pulmonary helminth infections is characterized by tissue injury leading to the release of the alarmin IL-33 and subsequent induction of type 2 immune responses. We recently described a role for IL-17A, through regulation of IFN{gamma}, as an important inducer of type 2 responses during infection with the lung-migrating rodent nematode Nippostrongylus brasiliensis. Here, we aimed to investigate the interaction between IL-17A and IL-33 during the early lung migratory stages of N. brasiliensis infection. In this brief report, we demonstrate that deficiency of IL-17A leads to impaired IL-33 expression and secretion early in infection, independent of IL-17A suppression of IFN{gamma}. Impaired IL-33 production was evident in lung epithelial cells, but not innate immune cells. Therefore, our results demonstrate that IL-17A can drive IL-33 during helminth infection, highlighting an additional mechanism through which IL-17A can regulate pulmonary type 2 immunity.

immunology↗

bioRxiv2022

Nucleic acid receptor ligands improve vaccination efficacy against the filarial nematode Litomosoides sigmodontis

Infections with helminths affect more than one billion people worldwide. Despite an urgent need there is no vaccine available that would confer long lasting protection against helminth infections. Previous studies indicated that a vaccination with irradiated infective L3 reduces the worm load. This present study investigated whether the additional activation of cytosolic nucleic acid receptors as adjuvant improves the efficacy of a vaccination with irradiated L3 larvae of the rodent filaria Litomosoides sigmodontis. Subcutaneous injection of irradiated L3 larvae in combination with poly(I:C) or 3pRNA resulted in increased neutrophil recruitment to the skin, accompanied by higher IP-10/CXCL10 and IFN-{beta} RNA levels at the site of injection. To investigate the in vivo impact on parasite clearance, BALB/c mice received 3 subcutaneous injections in 2-week intervals with irradiated L3 larvae in combination with poly(I:C) or 3pRNA prior to the challenge infection. Serum analysis before the challenge infection confirmed the induction of L. sigmodontis-specific antibodies in response to the immunization and serum from immunized mice significantly reduced larval motility in vitro with naive cells. 63 days after the challenge infection, vaccination with irradiated L3 larvae in combination with poly(I:C) or 3pRNA led to a significantly greater reduction in adult worm counts by 73% and 57%, respectively, compared to the immunization with irradiated L3 larvae alone (45%). Further, the treatment of L. sigmodontis infection with 3pRNA alone, but not poly(I:C), resulted in a reduced worm burden, supporting the therapeutic potential for the activation of RIG-I with 3pRNA. In conclusion, our data demonstrate that the additional activation of nucleic acid sensing immune receptors boosts the immune response and provides better protection against L. sigmodontis. Thus, the use of nucleic acid receptor agonists as vaccine adjuvants represents a promising novel strategy to improve the efficacy of vaccines against filariae and potentially of other helminths. Author SummaryFilarial nematodes can cause debilitating diseases such as onchocerciasis and lymphatic filariasis that present a major public health burden in the tropics and subtropics, putting more than a billion people at risk of infection. Filarial diseases are transmitted to humans by insect vectors as they take a blood meal. The WHO classifies both filarial infections as neglected tropical diseases and aims to eliminate the transmission of onchocerciasis and eliminate lymphatic filariasis as public health problem by 2030. However, up to date there is no vaccination available that could support the efforts to eliminate filarial diseases and potentially helminth infections in general. Here, we used the well-established murine model for filarial infection, Litomosoides sigmodontis, to test the use of nucleic acid receptor agonists as vaccine adjuvants to enhance local immune responses. We found that infection with L. sigmodontis induces type I IFN and our vaccine strategy enhances the production of type I IFN resulting in increased parasite-specific immune responses and enhanced worm clearance. In summary, our study provides a promising novel approach for a vaccination strategy using cytosolic RNA receptor agonists.

immunology↗

bioRxiv2021

Genotype and Th2 cells control monocyte to tissue resident macrophage differentiation during nematode infection of the pleural cavity

The recent revolution in tissue-resident macrophage biology has resulted largely from murine studies performed in the C57BL/6 strain. Here, we provide a comprehensive analysis of immune cells in the pleural cavity using both C57BL/6 and BALB/c mice. Unlike C57BL/6 mice, naive tissue-resident Large Cavity Macrophages (LCM) of BALB/c mice failed to fully implement the tissue residency program. Following infection with a pleural-dwelling nematode these pre-existing differences were accentuated with LCM expansion occurring in C57BL/6 but not BALB/c mice. While infection drove monocyte recruitment in both strains, only in C57BL/6 mice were monocytes able to efficiently integrate into the resident pool. Monocyte to macrophage conversion required both T cells and IL-4R signalling. Host genetics are therefore a key influence on tissue resident macrophage biology, and during nematode infection Th2 cells control the differentiation pathway of tissue resident macrophages. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/472661v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@bba5e1org.highwire.dtl.DTLVardef@1876aa4org.highwire.dtl.DTLVardef@16a6b1corg.highwire.dtl.DTLVardef@19e18b6_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2019

IL-17A both initiates (via IFNγ suppression) and limits the pulmonary type 2 immune response to nematode infection

Nippostrongylus brasiliensis is a well-defined model of type-2 immunity but the early lung-migrating phase is dominated by innate IL-17A production and neutrophilia. Using N. brasiliensis infection we confirm previous observations that Il17a-KO mice exhibit an impaired type-2 immune response. Neutrophil depletion and reconstitution studies demonstrated that neutrophils contribute to the subsequent eosinophilia but are not responsible for the ability of IL-17A to promote type-2 cytokine responses. Transcriptional profiling of the lung on day 2 of N. brasiliensis infection revealed an increased Ifn{gamma} signature in the Il17a-KO mice confirmed by enhanced IFN{gamma} protein production. Depletion of early IFN{gamma} rescued type-2 immune responses in the Il17a-KO mice demonstrating that IL-17A-mediated suppression of IFN{gamma} promotes type-2 immunity. Notably, when IL-17A was blocked later in infection, the type-2 response increased. IL-17A regulation of type-2 immunity was lung-specific and infection with Trichuris muris, revealed that IL-17A promotes a type-2 immune response in the lung even when a parasite lifecycle is restricted to the intestine. Together our data reveal IL-17A as a major regulator of pulmonary type-2 immunity which supports the development of a protective type-2 immune response but subsequently limits the magnitude of that response.

immunology↗

bioRxiv2019

Inflammasome-independent role for NLRP3 in controlling innate anti-helminth immunity and tissue repair in the lung

Alternatively activated macrophages are essential effector cells during type 2 immunity and tissue repair following helminth infections. We previously showed that Ym1, an alternative activation marker, can drive innate IL-1R-dependent neutrophil recruitment during infection with the lung-migrating nematode, Nippostrongylus brasiliensis suggesting a potential role for the inflammasome in the IL-1-mediated innate response to infection. While inflammasome proteins such as NLRP3 have important pro-inflammatory functions in macrophages, their role during type 2 responses and repair are less defined. We therefore infected Nlrp3-/- mice with N. brasiliensis. Unexpectedly, compared to WT mice, infected Nlrp3-/- mice had increased neutrophilia and eosinophilia, correlating with enhanced worm killing but at the expense of increased tissue damage and delayed lung repair. Transcriptional profiling showed that infected Nlrp3-/- mice exhibited elevated type 2 gene expression compared to WT mice. Notably, inflammasome activation was not evident early post-infection with N. brasiliensis and in contrast to Nlrp3-/- mice, anti-helminth responses were unaffected in caspase-1/11 deficient or WT mice treated with the NLRP3-specific inhibitor MCC950. Together these data suggest that NLRP3 can constrain lung neutrophilia and helminth killing and negatively regulate type 2 immune responses in an inflammasome-independent manner.

immunology↗