Mycobacterium indicus pranii (Mw) re-establishes host protective immune response in Leishmania donovani infected macrophages: critical role of IL-12

Adjuvant effects of TLR agonist gardiquimod admixed with Leishmania vaccine in mice model of visceral leishmaniasis

Tropical and subtropical areas of the world are affected by leishmaniasis, which is caused by Leishmania spp. It has been categorized as an NTD (neglected tropical disease) because of its negligence. The sand fly of genus Phlebotomus acts as the vector for the transmission of the promastigote form of this protozoan parasite to the mammalian host where it converts to amastigote form in the macrophages. Visceral form of leishmaniasis (VL) is a deadly infection in the endothelial system of the human and other mammals. Only a few chemotherapeutic agents are available for the treatment of this infectious disease whereas no vaccine is available for the control of leishmanial infection. Therefore in the current study, we have tested the effects of gardiquimod (a TLR agonist) as an adjuvant in combination with the formalin-killed antigen of L. donovani as a vaccine. The mice were vaccinated thrice at an interval of 2 weeks and challenged with L. donovani promastigotes after 2 weeks of the last vaccination. We assessed the parasite load, delayed-type hypersensitivity (DTH) responses, humoral and cell-mediated immune response in BALB/c mice before and after challenge infection with L. donovani. Immunized mice were found to have the least parasite load, high DTH response, elevated levels of Th1 cytokines, IgG2a, and nitric oxide than non-immunized and infected control mice. The efficacy of the vaccine was boosted with the use of adjuvant gardiquimod that depicts its potential as an adjuvant in this study. Our study is reporting the adjuvant effects of gardiquimod for the first time. Further studies using other Leishmania species can be performed to signify its role.

Combination of Mycobacterium indicus pranii and Heat-Induced Promastigotes Cures Drug-Resistant Leishmania Infection: Critical Role of Interleukin-6-Producing Classical Dendritic Cells

The major issues in available therapeutic modalities against leishmaniasis are cost, toxicity, and the emergence of drug resistance. The aim of this work was to develop a successful therapeutic adjuvant against drug-resistant Leishmania donovani infection by means of combining Mycobacterium indicus pranii with heat-induced promastigotes (HIP). One-month postinfected BALB/c mice were administered subcutaneously with M. indicus pranii (10⁸ cells) and HIP (100 μg) for 5 days. Spleens were harvested for flow cytometric and reverse transcriptase PCR analysis. The antileishmanial effect of the combination strategy was associated with induction of a disease-resolving Th1 and Th17 response with simultaneous downregulation of CD4⁺ CD25⁺ Foxp3⁺ (nTreg) cells and CD4⁺ CD25^- Foxp3^- (Tr1) cells in the spleen. The significant expansion of CD4⁺ T_CM (CD4⁺ CD44^hi CD11a^hi CD62L^hi) cells was a further interesting outcome of this therapeutic strategy in the context of long-term protection of hosts against secondary infection. Toll-like receptor 2 (TLR2) was also found instrumental in this antiparasitic therapy. Induced interleukin-6 (IL-6) production from expanded CD11c⁺ CD8α⁺ (cDC1) and CD11c⁺ CD11b⁺ (cDC2) dendritic cells (DCs) but not from the CD11b⁺ Ly6c⁺ inflammatory monocytes (iMOs), was found critical in the protective expansion of Th17 as evidenced by an in vivo IL-6 neutralization assay. It also promoted the hematopoietic conversion toward DC progenitors (pre-DCs) from common dendritic cell progenitors (CDPs), the immediate precursors, in bone marrow. This novel combinational strategy demonstrated that expansion of Th17 by IL-6 released from CD11c⁺ classical DCs is crucial, together with the conventional Th1 response, to control drug-resistant infection.

Anti-Cancer Effects of Synergistic Drug-Bacterium Combinations on Induced Breast Cancer in BALB/c Mice

Cancer development and progression are extremely complex due to the alteration of various genes and pathways. In most cases, multiple agents are required to control cancer progression. The purpose of this study is to investigate, using a mouse model, the synergistic interactions of anti-cancer agents, 1'-S-1'-acetoxychavicol acetate (ACA), Mycobacterium indicus pranii (MIP), and cisplatin (CDDP) in double and triple combinations to treat chemo-sensitize and immune-sensitize breast cancer. Changes in tumor volume and body weight were monitored. Organs were harvested and stained using hematoxylin-eosin for histopathological assessment. Milliplex enzyme-linked immunosorbent assay (ELISA) was performed to determine cytokine levels, while immunohistochemistry (IHC) was conducted on tumor biopsies to verify systemic drug effects. In vivo mouse models showed tumor regression with maintenance of regular body weight for all the different treatment regimens. IHC results provided conclusive evidence indicating that combination regimens were able to down-regulate nuclear factor kappa-B activation and reduce the expression of its regulated pro-inflammatory proteins. Reduction of pro-inflammatory cytokines (e.g., IL-6, TNF-α, and IFN-ɣ) levels were observed when using the triple combination, which indicated that the synergistic drug combination was able to significantly control cancer progression. In conclusion, ACA, MIP, and CDDP together serve as promising candidates for further development and for subsequent clinical trials against estrogen-sensitive breast cancer.

Immunomodulatory effect of Arabinosylated lipoarabinomannan restrict the progression of visceral leishmaniasis through NOD2 inflammatory pathway: Functional regulation of T cell subsets

NOD like receptors (NLR) are essential pathogen associated molecular pattern receptors of cytoplasmic origin. During several intracellular parasitic infections NLR played vital role for host protective immune response against the pathogen. Amongst various classes of NLR, NOD1 and NOD2 had been extensively studied and were found to be the most active member of the NLR family. Therefore, we wanted to study the role of NOD1/NOD2 during Leishmania donovani infection and the mechanism behind the utilization of this pathway as a therapeutic approach. Using the infected model of macrophage and BALB/c mice the expression of NOD1 and NOD2 were analysed. Our study showed that NOD2 but not NOD1 has been exploited during experimental VL, leading to the imbalance between Th-1/Th-2 cytokines profile. Over-expression of NOD2 and stimulation with its ligand muramyl dipeptide leads to successful clearance of parasite. During in vivo experiments we found that arabinosylated lipoarabinomannan helps in the restoration of NOD2 and with MDP in combination leads to effective clearance of parasite which rescued host protective immunity and comparatively more effective than Mw and MDP combination resulting in increase T cell response. Consequently, our study highlighted the significance of NOD2 during infection the immune-modulations of which can be used as a therapeutic target.

Mycobacterium indicus pranii (Mw)-mediated protection against visceral leishmaniasis by reciprocal regulation of host dual-specificity phosphatases

Leishmania donovani resides within the host macrophages by dampening host defence mechanisms and thereby it modulates the host cell functions for its survival. Multiple host cell factors compete during the interplay between the host and the parasite. Roles for dual-specificity phosphatases (DUSPs) are implicated in various pathological conditions. However, the reciprocity of these DUSPs was unknown in L. donovani infection in a susceptible model. Here, we show that Mycobacterium indicus pranii (Mw), an immunomodulator, reciprocally regulates DUSP1 and DUSP6 through the TLR4 pathway. Association of PKC-β with DUSP6 increases after Mw treatment resulting in decreased IL-10, phosphorylation of ERK1/2 and Arginase-1, whereas Mw treatment decreases the association between PKC-ε and DUSP1 resulting in increased IL-12, phosphorylation of p38 and inducible nitric oxide synthase expression. Silencing of DUSP1 or over-expression of DUSP6 in L. donovani-infected BALB/c mice decreases the parasite burden by inducing IL-12 and reducing IL-10 production. Therefore, we identify DUSP1 and DUSP6 as therapeutic targets, functions of which could be favourably modulated by Mw during L. donovani infection.

Acetyl shikonin induces IL-12, nitric oxide and ROS to kill intracellular parasite Leishmania donovani in infected hosts

Acetyl shikonin (AS), a naphthoquinone isolated from Arnebia nobilis, was tested against visceral leishmaniasis in this study, revealing that AS provides a chemo-immunotherapeutic strategy against visceral leishmaniasis.

Mycobacterium indicus pranii (Mw) inhibits invasion by reducing matrix metalloproteinase (MMP-9) via AKT/ERK-1/2 and PKCα signaling: A potential candidate in melanoma cancer therapy

Invasion and metastasis via induction of matrix metalloproteinases are the main causes of death in melanoma cancer. In this study, we investigated the inhibitory effects of heat killed saprophytic bacterium Mycobacterium indicus pranii (Mw) on B16F10 melanoma cell invasion. Mw reported to be an immunomodulator has antitumor activity however, its effect on cancer cell invasion has not been studied. Highly invasive B16F10 melanoma was found sensitive to Mw which downregulated MMP-9 expression. Mw treatment inhibited nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) transcriptional activity and respective DNA binding to MMP-9 promoter. Moreover, Mw also overcame the promoting effects of PMA on B16F10 cell invasion. Mw decreased PMA-induced transcriptional activation of NF-κB and AP-1 by inhibiting phosphorylation of AKT and ERK-1/2. Furthermore, Mw strongly suppressed PMA-induced membrane localization of protein kinase C α (PKCα) since PKCα inhibition caused a marked decrease in PMA-induced MMP-9 secretion as well as AKT/ERK-1/2 activation. These results suggest that Mw may be a promising anti-invasive agent as it blocks tumor growth and inhibits B16F10 cell invasion by reducing MMP-9 activation through inhibition of PKCα/ AKT/ ERK-1/2 phosphorylation and NF-κB/AP-1 activation.

Genetically Modified Live Attenuated Leishmania donovani Parasites Induce Innate Immunity through Classical Activation of Macrophages That Direct the Th1 Response in Mice

Visceral leishmaniasis (VL) causes significant mortality and there is no effective vaccine. Previously, we have shown that genetically modified Leishmania donovani parasites, here described as live attenuated parasites, induce a host protective adaptive immune response in various animal models. In this study, we demonstrate an innate immune response upon infection with live attenuated parasites in macrophages from BALB/c mice both in vitro and in vivo. In vitro infection of macrophages with live attenuated parasites (compared to that with wild-type [WT] L. donovani parasites) induced significantly higher production of proinflammatory cytokines (tumor necrosis factor alpha [TNF-α], interleukin-12 [IL-12], gamma interferon [IFN-γ], and IL-6), chemokines (monocyte chemoattractant protein 1/CCL-2, macrophage inflammatory protein 1α/CCL-3, and IP-10), reactive oxygen species (ROS), and nitric oxide, while concomitantly reducing anti-inflammatory cytokine IL-10 and arginase-1 activities, suggesting a dominant classically activated/M1 macrophage response. The classically activated response in turn helps in presenting antigen to T cells, as observed with robust CD4(+) T cell activation in vitro. Similarly, parasitized splenic macrophages from live attenuated parasite-infected mice also demonstrated induction of an M1 macrophage phenotype, indicated by upregulation of IL-1β, TNF-α, IL-12, and inducible nitric oxide synthase 2 and downregulation of genes associated with the M2 phenotype, i.e., the IL-10, YM1, Arg-1, and MRC-1 genes, compared to WT L. donovani-infected mice. Furthermore, an ex vivo antigen presentation assay showed macrophages from live attenuated parasite-infected mice induced higher IFN-γ and IL-2 but significantly less IL-10 production by ovalbumin-specific CD4(+) T cells, resulting in proliferation of Th1 cells. These data suggest that infection with live attenuated parasites promotes a state of classical activation (M1 dominant) in macrophages that leads to the generation of protective Th1 responses in BALB/c mice.

The combination of a novel immunomodulator with a regulatory T cell suppressing antibody (DTA-1) regress advanced stage B16F10 solid tumor by repolarizing tumor associated macrophages in situ

Tumor associated macrophages and tumor infiltrating regulatory T cells greatly hamper host-protective antitumor responses. Therefore, we utilized a novel immunomodulator, heat-killed Mycobacterium indicus pranii (Mw), to repolarize TAM and an agonistic GITR antibody (DTA-1) to reduce intratumoral regulatory T cell frequency for generation of a host-protective antitumor response. Although, the combination of Mw and DTA-1was found to be effective against advanced stage tumors, however, Mw or DTA-1 failed to do so when administered individually. The presence of high level of regulatory T cells abrogated the only Mw induced antitumor functions, whereas only DTA-1 treatment was found to be ineffective due to its inability to induce TAM repolarization in vivo. The combination therapy was found to be effective since DTA-1 treatment reduced the frequency of regulatory T cells to such an extent where they could not attenuate Mw induced TAM repolarization in vivo. Therefore, the combination therapy involving Mw and DTA-1 may be utilized to the success of advanced stage solid tumor immunotherapies.

Immunomodulation in human dendritic cells leads to induction of interferon-gamma production by Leishmania donovani derived KMP-11 antigen via activation of NF-κB in Indian kala-azar patients

Dendritic cells (DCs) and macrophages (MΦs) are well-known antigen presenting cells with an ability to produce IL-12 which indicates that they have potential of directing acquired immunity toward a Th1-biased response. The aim of this study was to examine the effect of Leishmania specific KMP-11 antigen through comparison of immune responses after presentation by DCs and MΦs to T cells in Indian patients with VL. Patients with DCS and MΦs were directed against a purified Leishmania donovani antigen (KMP-11) and phytohaemagglutinin (PHA). The cytokines (IL-12, IL-10, and TGF-β) producing abilities of the DCs and MΦs against these antigens were determined by flow cytometry. The transcription factor (NF-κB) and T-cell cytokine support (IFN-γ, IL-10), which could be significant in effector immune function, were also determined. Severe hindrance in the immune protection due to Leishmania parasites, as revealed by decreased expression of IL-12 and upregulation of IL-10 and TGF-β expression in the MΦs compared to DCs, occurred in VL patients. The production of IL-12 in response to L. donovani KMP-11 antigen was increased in DCs which was reduced in MΦs of VL patients. In contrast, the presentation of KMP-11 antigen by DCs to T-lymphocytes in VL patients significantly increased the IFN-γ produced by these immune cells, whereas the levels of IL-10 were significantly elevated after presentation of KMP-11antigen by MΦs. The VL patients were observed with severely dysfunctional MΦs in terms of NF-κB activity that could be recovered only after stimulation of DCs with L. donovani KMP-11 antigen. Immunologically the better competitiveness of KMP-11 antigen through a dendritic cell delivery system may be used to revert T-cell anergy, and control strategy can be designed accordingly against kala-azar.

Unresponsiveness of Mycobacterium w vaccine in managing acute and chronic Leishmania donovani infections in mouse and hamster

The role of Mycobacterium w (Mw) vaccine as an immunomodulator and immunoprophylactant in the treatment of mycobacterial diseases (leprosy and pulmonary tuberculosis) is well established. The fact that it shares common antigens with leishmanial parasites prompted its assessment as an immunostimulant and as an adjunct to known anti-leishmanials that may help in stimulating the suppressed immune status of Leishmania donovani-infected individuals. The efficacy of Mw vaccine was assessed as an immunomodulator, prophylactically either alone or in combination with anti-leishmanial vaccine, as well as therapeutically as an adjunct to anti-leishmanial treatment in L. donovani-infected hamsters, representing a chronic human Visceral Leishmaniasis (VL) model. Similarly, its efficacy was also evaluated in L. donovani-infected BALB/c mice, representing an acute VL model. The preliminary studies revealed that Mw was ineffective as an immunostimulant and/or immunoprophylactant in hamsters infected with L. donovani, as estimated by T-cell immunological responses. However, in the BALB/c mice-VL model it appeared as an effective immunostimulant but a futile prophylactic agent. It is therefore inferred that, contrary to its role in managing tuberculosis and leprosy infections, Mw vaccine has not been successful in controlling VL infection, emphasizing the need to find detailed explanations for the failure of this vaccine against the disease.

Evaluation of recombinant E2 protein-based and whole-virus inactivated candidate vaccines against chikungunya virus

OBJECTIVES

With the re-emergence of chikungunya virus (CHIKV) in an explosive form and in the absence of a commercially available vaccine, we aimed to develop candidate vaccines employing recombinant E2 protein or chemically inactivated whole virus.

DESIGN AND METHODS

E2 gene of CHIKV isolate of ECSA genotype was cloned in pET15b vector, expressed and purified (rE2p). The virus was propagated in Vero cell line, purified and inactivated with formalin and BPL individually. Six to eight weeks old female BALB/c mice were immunized intramuscularly with two doses of 10μg, 20μg and 50μg of vaccine formulations with or without adjuvants, 2 weeks apart. The adjuvants evaluated were alum, Mw, CadB (rE2p), alum/Mw (formalin inactivated CHIKV) and alum (BPL-inactivated CHIKV). Humoral immunity was assessed by ELISA and in vitro neutralization test using homologous and heterologous (Asian genotype) strains of CHIKV. Two cohorts of vaccinated mice were challenged separately via intranasal route with homologous virus two and 20 weeks after the 2nd dose. Viral load (CHIKV RNA by real time PCR) was determined in the serum and tissues (muscle, brain, spleen) of the mice challenged with the homologous virus.

RESULTS

Anti-CHIK-antibody titres were dose dependent for all the immunogen formulations. BPL-inactivated vaccines led to the highest ELISA/neutralizing antibody (nAb) titres while alum was the most effective adjuvant. Asian genotype strain could be neutralized by the nAbs. In an adult mouse model, complete protection was offered by the alum-adjuvanted rE2p and both the inactivated vaccines as no virus was detected in the tissues and blood after challenge 2 weeks or 20 weeks-post-2nd dose. However, with rE2p-CadB, very low viremia was recorded on the 2nd day-post-challenge.

CONCLUSION

Both rE2p and BPL/formalin-inactivated virus are promising candidate vaccines deserving further evaluation.