An Insight Into Systemic Immune Response in Leishmania donovani Mediated Atypical Cutaneous Leishmaniasis in the New Endemic State of Himachal Pradesh, India

Leishmaniasis continues to afflict known and newer endemic sites despite global efforts towards its control and elimination. In this regard, the emergence of newer endemic sites with unusual disease formats is recognized wherein Leishmania donovani complex classically known to cause visceral disease is demonstrated to cause cutaneous manifestation. In this context, atypical cutaneous leishmaniasis (CL) cases caused by L. donovani genetic variants from the newer endemic state of Himachal Pradesh (HP) in India are beginning to be understood in terms of parasite determinants. The atypical CL manifestation further needs to be explored to define host immune correlates with a possible role in driving the unusual disease progression. In the given study, we performed comprehensive systemic-immune profiling of the atypical CL patients from the study area in HP, India, in comparison with the classical visceral leishmaniasis (VL) patients from the northeast region of India. The systemic immune response was studied using ELISA-based assessment of Th1, Th2, Th17, Treg, and Th22 specific plasma cytokine expression pattern and parasite-specific total serum IgG/IgG subclasses. The specified immune correlates are known to exhibit heterogeneous association with the different infecting parasite species, infection load, and co-lateral host immunopathology in classical CL and VL. In the atypical CL patient group, altered expression of IL-10 emerged as the key finding that could potentially fine-tune the Th1/Th17/Th22 effector cytokine axis towards a localized cutaneous manifestation. A reduced expression of IL-10 along with a high IFN-γ/IL-10 ratio as a readout of effective parasite killing defined atypical cutaneous outcome. In contrast, high circulatory IL-10 levels and a depressed IFN-γ/IL-10 ratio were seen in classical VL patients in line with an ineffective parasite-killing cytokine response. Overall, the study highlights new knowledge on host immune correlates in terms of cytokine expression pattern and IgG subclasses that underline atypical disease manifestation such that L. donovani, a generally visceralizing parasite species cause skin localized cutaneous lesions.

Molecular Characterization and Functional Analysis of the Nattectin-like Toxin from the Venomous Fish Thalassophryne maculosa

TmC4-47.2 is a toxin with myotoxic activity found in the venom of Thalassophryne maculosa, a venomous fish commonly found in Latin America whose envenomation produces an injury characterized by delayed neutrophil migration, production of major pro-inflammatory cytokines, and necrosis at the wound site, as well as a specific systemic immune response. However, there are few studies on the protein structure and functions associated with it. Here, the toxin was identified from the crude venom by chromatography and protein purification systems. TmC4-47.2 shows high homology with the Nattectin from Thalassophryne nattereri venom, with 6 cysteines and QPD domain for binding to galactose. We confirm its hemagglutinating and microbicide abilities independent of carbohydrate binding, supporting its classification as a nattectin-like lectin. After performing the characterization of TmC4-47.2, we verified its ability to induce an increase in the rolling and adherence of leukocytes in cremaster post-capillary venules dependent on the α5β1 integrin. Finally, we could observe the inflammatory activity of TmC4-47.2 through the production of IL-6 and eotaxin in the peritoneal cavity with sustained recruitment of eosinophils and neutrophils up to 24 h. Together, our study characterized a nattectin-like protein from T. maculosa, pointing to its role as a molecule involved in the carbohydrate-independent agglutination response and modulation of eosinophilic and neutrophilic inflammation.

Cecropins contribute to Drosophila host defense against a subset of fungal and Gram-negative bacterial infection

Cecropins are small helical secreted peptides with antimicrobial activity that are widely distributed among insects. Genes encoding cecropins are strongly induced upon infection, pointing to their role in host-defense. In Drosophila, four cecropin genes clustered in the genome (CecA1, CecA2, CecB and CecC) are expressed upon infection downstream of the Toll and Imd pathways. In this study, we generated a short deletion ΔCecA-C removing the whole cecropin locus. Using the ΔCecA-C deficiency alone or in combination with other antimicrobial peptide (AMP) mutations, we addressed the function of cecropins in the systemic immune response. ΔCecA-C flies were viable and resisted challenge with various microbes as wild-type. However, removing ΔCecA-C in flies already lacking ten other AMP genes revealed a role for cecropins in defense against Gram-negative bacteria and fungi. Measurements of pathogen loads confirm that cecropins contribute to the control of certain Gram-negative bacteria, notably Enterobacter cloacae and Providencia heimbachae. Collectively, our work provides the first genetic demonstration of a role for cecropins in insect host defense, and confirms their in vivo activity primarily against Gram-negative bacteria and fungi. Generation of a fly line (ΔAMP14) that lacks fourteen immune inducible AMPs provides a powerful tool to address the function of these immune effectors in host-pathogen interactions and beyond.

869 Locally administered immunotherapy self-delivering RNAi PH-762 results in abscopal clearance of untreated distal tumors, suggesting systemic immune response, in a murine hepatocarcinoma model

BackgroundThe development of locally administered immune checkpoint inhibition (ICI) holds potential promise for enhanced activity and decreased systemic toxicity, but such an approach is challenging with the available ICI antibodies. We have previously shown that the intratumoral (IT) delivery of PH-762, a self-delivering RNAi compound targeting PD-1 based on proprietary INTASYL™ technology, can significantly inhibit tumor growth associated with changes in the immune cell population in the tumor microenvironment towards an anti-tumor phenotype. We present data showing that IT administration of PH-762 not only inhibits local tumor growth but can also elicit an abscopal effect in distal untreated tumors. The in vivo efficacy and in vitro mechanism of action support the generation of a PH-762 driven systemic anti-tumor immune response. Therefore, ICI using INTASYL is an alternative to antibody drugs for immunotherapy.MethodsTo assess in vivo efficacy, Hepa1–6 cells were implanted subcutaneously into the flanks of C57BL/6J mice. Vehicle (PBS) or murine targeting PH-762 (mPH-762) were administered IT on Days 1, 4, 7, 10 and 14. To determine an abscopal effect cells were also implanted into the opposite flank but left untreated. Tumor volumes and body weights were recorded. In addition, in vitro mechanism of action studies were performed with CD3-stimulated human pan T cells. PD-1 mRNA knockdown was assessed by qRT-PCR; PD-1 protein expression by flow cytometry; and T cell function by cytokine release.ResultsTreatment with IT administered mPH-762 significantly inhibited tumor growth compared with vehicle treated control tumors. Furthermore, the growth of the untreated bilateral tumor was significantly reduced with 80% of these tumors showing complete regression. Mechanism of action studies showed potent and durable silencing of PD-1. Increased release of IFN-γ, CXCL10, and IL-6 and suppression of IL-10 release were indicators of an enhanced immune response.ConclusionsThese data show that silencing PD-1 with IT administration of mPH-762 not only inhibits growth of treated tumors but elicits an abscopal effect leading to cure of distal tumors. This data and other recently published data showing evidence of a specific antitumor immune response in a tumor rechallenge model after prior treatment with INTASYL compounds, demonstrate the desired systemic immune response can be obtained with local administration of PH-762. INTASYL represent an alternative to antibody therapy for IT checkpoint blockade with potential for improved efficacy and reduced systemic toxicity which will be investigated in an upcoming clinical trial.

Immersion Vaccination by a Biomimetic-Mucoadhesive Nanovaccine Induces Humoral Immune Response of Red Tilapia (Oreochromis sp.) against Flavobacterium columnare Challenge

Immersion vaccination with a biomimetic mucoadhesive nanovaccine has been shown to induce a strong mucosal immune response against columnaris disease, a serious bacterial disease in farmed red tilapia caused by Flavobacterium columnare. However, the induction of a systemic immune response by the vaccine is yet to be investigated. Here, we examine if a specific humoral immune response is stimulated in tilapia by a biomimetic-mucoadhesive nanovaccine against Flavobacterium columnare using an indirect-enzyme-linked immunosorbent assay (ELISA), serum bactericidal activity (SBA) and the expression of immune-related genes within the head-kidney and spleen, together with assessing the relative percent survival of vaccinated fish after experimentally infecting them with F. columnare. The anti-IgM antibody titer of fish at 14 and 21 days post-vaccination was significantly higher in chitosan complex nanoemulsion (CS-NE) vaccinated fish compared to fish vaccinated with the formalin-killed vaccine or control fish, supporting the serum bactericidal activity results at these time points. The cumulative mortality of the unvaccinated control fish was 87% after challenging fish with the pathogen, while the cumulative mortality of the CS-NE vaccinated group was 24%, which was significantly lower than the formalin-killed vaccinated and control fish. There was a significant upregulation of IgM, IgT, TNF α, and IL1-β genes in the spleen and kidney of vaccinated fish. Significant upregulation of IgM and IgT genes was observed in the spleen of CS-NE vaccinated fish. The study confirmed the charged-chitosan-based mucoadhesive nanovaccine to be an effective platform for immersion vaccination of tilapia, with fish generating a humoral systemic immune response against columnaris disease in vaccinated fish.

A mucosal antibody response is induced by intra-muscular SARS-CoV-2 mRNA vaccination

Vaccines against SARS-CoV-2 administered via the parenteral route (intra-muscular = i.m.) are effective at preventing COVID-19 in part by inducing neutralizing antibodies in the blood. The first line of defense against SARS-CoV-2 is in the upper respiratory tract, yet we know very little about whether COVID-19 vaccines induce immunity in this compartment, if at all. We analysed salivary antibodies against the SARS-CoV-2 Spike protein and its receptor binding domain (RBD) following 2 i.m. injections of either BNT162b2 or mRNA-1273 vaccines. Salivary anti-Spike/RBD IgG was detected after 1 dose and increased further after dose 2, reflecting the systemic immune response. Interestingly, salivary anti-Spike/RBD IgA associated with the secretory component (sIgA) was detected in nearly all vaccinated participants after one dose of mRNA vaccine, with anti-Spike sIgA diminishing after dose 2. Vaccination with ChAdOx1-S (Ad) followed by mRNA induced similar levels of salivary anti-Spike/RBD IgG and IgA, and both mRNA/mRNA and Ad/mRNA regimes provoked modest neutralizing capacity in this biofluid. Our results demonstrate that SARS-CoV-2 mRNA/mRNA and Ad/mRNA vaccination induces antibodies in the saliva, and in response to one dose of mRNA, a compartmentalized and transient antigen-specific sIgA response is generated that does not correlate with systemic immunity.

Overview of implantable and injectable biomaterials in immunotherapy

Immunotherapy has shown promising applications in cancer treatment as it boosts the systemic immune response. Existing immunotherapy strategies have certain drawbacks which can be addressed by engineered biomaterials. In this review, we focused on advanced immunotherapy methods involving implantable and injectable biomaterials for the treatment of cancer. Engineered biomaterials as carriers for immunomodulatory agents aid in the local drug delivery, thus reducing the frequency of off-target side effects. Also, biomaterial-based cancer vaccines have the potential to target specific tissues by finely altering the physical properties of the drug to achieve desired drug release kinetics.