Tumor targeted delivery of mycobacterial adjuvant encapsulated chitosan nanoparticles showed potential anti-cancer activity and immune cell activation in tumor microenvironment.

Targeting immunotherapeutics inside the tumor microenvironment (TME) with intact biological activity remains a pressing issue. Mycobacterium indicus pranii (MIP), an approved adjuvant therapy for leprosy has exhibited promising results in clinical trials of lung (NSCLC) and bladder cancer. Whole MIP as well as its cell wall fraction have shown tumor growth suppression and enhanced survival in mice model of melanoma, when administered peritumorally. Clinically, peritumoral delivery remains a procedural limitation. In this study, a tumor targeted delivery system was designed, where chitosan nanoparticles loaded with MIP adjuvants, when administered intravenously showed preferential accumulation within the TME, exploiting the principle of enhanced permeability and retention effect. Bio-distribution studies revealed their highest concentration inside the tumor after 6 h of administration. Interestingly, MIP adjuvant nano-formulations significantly reduced the tumor volume in the treated groups and increased the frequency of activated immune cells inside the TME. For chemoimmunotherapeutics studies, MIP nano-formulation was combined with standard dosage regimen of Paclitaxel. Combined therapy exhibited a further reduction in tumor volume relative to either of the MIP nano formulations. From this study a three-pronged strategy emerged as the underlying mechanism; chitosan and Paclitaxel have shown direct role in tumor cell death and the MIP nano-formulation activates the tumor residing immune cells which ultimately leads to the reduced tumor growth.

Lipoarabinomannan from Mycobacterium indicus pranii shows immunostimulatory activity and induces autophagy in macrophages.

Mycobacterium indicus pranii (MIP) known for its immunotherapeutic potential against leprosy and tuberculosis is undergoing various clinical trials and also simultaneously being studied in animal models to get insight into the mechanistic details contributing to its protective efficacy as a vaccine candidate. Studies have shown potential immunomodulatory properties of MIP, the most significant being the ability to induce strong Th1 type of response, enhanced expression of pro-inflammatory cytokines, activation of APCs and lymphocytes, elicitation of M.tb specific poly-functional T cells. All of these form crucial components of host-immune response during M.tb infection. Also, MIP was found to be potent inducer of autophagy in macrophages which resulted in enhanced clearance of M.tb from MIP and M.tb co-infected cells. Hence, we further examined the component/s of MIP responsible for autophagy induction. Interestingly, we found that MIP lipids and DNA were able to induce autophagy but not the protein fraction. LAM being one of the crucial components of mycobacterial cell-wall lipids and possessing the ability of immunomodulation; we isolated LAM from MIP and did a comparative study with M.tb-LAM. Stimulation with MIP-LAM resulted in significantly high secretion of pro-inflammatory cytokines and displayed high autophagy inducing potential in macrophages as compared to M.tb-LAM. Treatment with MIP-LAM enhanced the co-localization of M.tb within the phago-lysosomes and increased the clearance of M.tb from the infected macrophages. This study describes LAM to be a crucial component of MIP which has significant contribution to its immunotherapeutic efficacy against TB.

Cell wall fraction of Mycobacterium indicus pranii shows potential Th1 adjuvant activity.

Very few adjuvants inducing Th1 immune response have been developed and are under clinical investigation. Hence, there is the need to find an adjuvant that elicits strong Th1 immune response which should be safe when injected in the host along with vaccines. Mycobacterium indicus pranii (MIP), a non-pathogenic vaccine candidate, has shown strong immunomodulatory activity in leprosy/tuberculosis/cancer and in genital warts patients where its administration shifted the host immune response towards Th1 type. These findings prompted us to study the components of MIP in detail for their Th1 inducing property. Since mycobacterial cell wall is very rich in immunostimulatory components and is known to play important role in immune modulation, we investigated the activity of MIP cell wall using Ovalbumin antigen (OVA) as model antigen. 'Whole cell wall' (CW) and 'aqueous soluble cell wall fractions' (ACW) induced significant Th1 immune response while 'cell wall skeleton' (CWS) induced strong Th2 type of immune response. Finally, functional activity of fractions having Th1 inducing activity was evaluated in mouse model of melanoma. CW demonstrated significant anti-tumor activity similar to whole MIP. Anti-tumor activity of CW could be correlated with enhanced tumor antigen specific Th1 immune response observed in tumor draining lymph nodes.

Mycobacterium indicus pranii protein MIP_05962 induces Th1 cell mediated immune response in mice.

Utility of Mycobacterium indicus pranii (MIP) as a multistage vaccine against mycobacterial infections demands identification of its protective antigens. We explored antigenicity and immunogenicity of a candidate protein MIP_05962 that depicts homology to HSP18 of M. leprae and antigen1 of Mycobacterium tuberculosis. This protein elicited substantial antibody response in immunized mice along with modulation of cellular immune response towards protective Th1 type. Both CD4+ and CD8+ subsets from immunized mice produced hallmark protective cytokines, IFN-γ, TNF-α and IL-2. This protein also enhanced the CD4+ effector memory that could act as first line of defence during infections. These results point to MIP_05962 as a protective antigen that contributes, in conjunction with others, to the protective immunity of this live vaccine candidate.

Immunogenicity and protective efficacy of "Mycobacterium w" against Mycobacterium tuberculosis in mice immunized with live versus heat-killed M. w by the aerosol or parenteral route.

As the disease caused by Mycobacterium tuberculosis continues to be a burden, there is a concerted effort to find new vaccines to combat this problem. One of the important vaccine strategies is whole bacterial vaccines. This approach relies on multiple antigens and built-in adjuvanticity. Other mycobacterial strains which share cross-reactive antigens with M. tuberculosis have been considered as alternatives to M. bovis for vaccine use. One such strain, "Mycobacterium w", had been evaluated for its immunomodulatory properties in leprosy. A vaccine against leprosy based on killed M. w is approved for human use, where it has resulted in clinical improvement, accelerated bacterial clearance, and increased immune responses to Mycobacterium leprae antigens. M. w shares antigens not only with M. leprae but also with M. tuberculosis, and initial studies have shown that vaccination with killed M. w induces protection against tuberculosis in Mycobacterium bovis BCG responder, as well as BCG nonresponder, strains of mice. Hence, we further studied the protective potential of M. w and the underlying immune responses in the mouse model of tuberculosis. We analyzed the protective efficacy of M. w immunization in both live and killed forms through the parenteral route and by aerosol immunization, compared with that of BCG. Our findings provide evidence that M. w has potential protective efficacy against M. tuberculosis. M. w activates macrophage activity, as well as lymphocytes. M. w immunization by both the parenteral route and aerosol administration gives higher protection than BCG given by the parenteral route in the mouse model of tuberculosis.