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- RFP Year2018
- Awarded Amount$558,315
- DiseaseNTD (Leishmaniasis)
- Development StagePreclinical Development
- Collaboration PartnersUniversity of Tokyo, International Center for Diarrheal Disease Research Bangladesh, Infectious Disease Research Institute
Introduction and Background of the Project
Caused by L. donovani infection, visceral leishmaniasis (VL; Kala-azar) is endemic in large areas of the Indian subcontinent. Primary symptoms include splenomegaly, weight loss and anemia and VL has the highest mortality rate among neglected tropical diseases. Improved treatment regimen are being sought to reduce toxicity and drug resistance. Resistance to antimonials has resulted in their replacement with Amphotericin B, paromomycin and miltefosine. Treatment failure occurs in 3-30% of treated cases in VL endemic populations and can be as high as 50-60% for patients co-infected with HIV. Extended observation periods are required to detect relapse and progression to post-Kala azar dermal leishmaniasis (PKDL).
Intervention in VL patients at greatest risk of treatment failure, relapse or subsequent development of PKDL is critical for effective disease management. Our published data has identified vaccine candidates that are effective as a prophylaxis in advanced animal models. In this proposal we will build upon this data to determine the candidate antigen best suited for use in the Indian subcontinent (Bangladesh) and use a long term preclinical model of L. donovani infection to develop immune/chemotherapeutic approaches to prevent complications of VL.
To develop an effective therapeutic vaccine for VL, selection of good antigen(s) and adjuvant is important. Besides, the vaccine, when used a component of the immune/chemotherapeutics, is not supposed to compromise the effect of chemotherapy. Therefore, this project will comprise three major activities; 1) Patient-instructed selection of vaccine antigen for prevention of PKDL, 2) Evaluation of compatibility of vaccines with Ambisome treatment, 3) Evaluation of efficacy of immune therapy in long term VL model. Based on the success in these activities, all the partners will start preparation for clinical trial of the therapeutic vaccine in combination with AmBisome.
How can your partnership (project) address global health challenges?
VL is endemic in large areas of the tropics, subtropics and the Mediterranean Basin. VL in East Africa and the Indian subcontinent is caused by L. donovani infection. Elimination programs have reduced active VL case numbers in the past few years, but eradication is impeded by: individuals who are asymptomatically infected with L. donovani; the increase of relapsed VL cases, and; the development of PKDL. Recurrence of VL occurs in 3.7% of treated patients within 24 months after treatment, while PKDL occurs in >50% of VL patients in East Africa and 10-20% in the Indian sub-continent within months of completing treatment. Despite being considered a research priority, validated strategies to prevent relapse or PKDL development are lacking. In addition, the use of a single drug (AmBisome) for treatment presents risk of developing resistance. This proposal aims to develop an immune/chemotherapeutic regimen to provide short and long-term protection against the complications, and potential transmission, of L. donovani infection.
What sort of innovation are you bringing in your project?
Novel treatment regimen involving chemoimmunotherapy to reduce or prevent typical post-treatment sequelae of VL.
Role and Responsibility of Each Partner
icddr,b researchers will address patient-instructed selection of vaccine antigen for prevention of PKDL, which will guarantee the wide coverage by the vaccine of people having distinct immunological background. IDRI scientists will determine compatibility of vaccines with Ambisome treatment by evaluating the antigen-specific CD4 T cell responses induced by immunization and determine the impact of AmBisome on these. University of Tokyo scientists will address the efficacy of immune therapy in long term VL model by evaluating the impact of chemo-immunotherapeutic regimen on various pathologies induced by long-term L. donovani infection.
1. Project objective
Recurrence of VL occurs in 3.7% of treated patients within 24 months, while PKDL occurs in >50% of VL patients in East Africa and 10-20% in the Indian sub-continent. Safe and highly effective treatment for PKDL currently is not available, with the cure rate with miltefosine monotherapy varying from 60% to 80% and 16% relapsing with PKDL after treatment. In addition, the use of a single drug (AmBisome) for treatment presents risk of developing resistance. This proposal will develop an immune/chemotherapeutic regimen to provide short and long-term protection against the complications, and potential transmission, of L. donovani infection.
2. Project design
Three integrated specific objectives aimed to select between advanced vaccine antigens (LEISH-F3, LEISH-F3+) and demonstrate their efficacy when used with adjuvant formulations, with or without AmBisome, for therapeutic intervention in a long term VL model. Our objectives determined:
a. preferred antigen for the Indian subcontinent, indicated by patient responses.
b. compatibility of defined subunit vaccine and AmBisome schedules, identifying regimen with immune enhancement (or non-interference), determined by contrasting T cell responses to each individual component of the vaccine fusion antigens.
c. immunochemotherapy schedules that provide the best preclinical outcome, identified by both disease parameters and parasite burden.
3. Results, lessons learned
The research activities identified that the individual N, S and DC, along with trifusion LEISH-F3+ (N, S and DC) and difusion LEISH-F3 (N and S), proteins were detected by circulating antibodies in the sera of virtually all VL and relapsed VL patients evaluated in the study. LEISH-F3+ was, however, recognized by a greater proportion of, and at higher levels in, PKDL patients than LEISH-F3. Assessment of responses following immunization of mice with either the LEISH-F3 or LEISH-F3+ protein delivered in TLR4L-containing stable emulsion, in the presence or absence of AmBisome, indicated that drug had no impact on antigen-specific antibody and cellular responses induced against either fusion antigen. Further evaluation indicated that TLR4L-SE adjuvanted LEISH-F3+ induced responses equivalent or enhanced over those observed when either TLR7L-SE or TLR4L/TLR7L-SE were used to deliver antigen. Finally, in a long term disease model, mice treated with high-dose Ambisome 3 months after L. donovani infection demonstrated resolved ‘clinical’ outcome, whereas animals treated with low-dose Ambisome demonstrated improved, but not fully resolved, ‘clinical’ outcome. Inclusion TLR4L-SE adjuvanted LEISH-F3+ did not interfere with low-dose AmBisome efficacy and provided a slight improvement in some, but not all, of the measured parameters (hemoglobin). Together, these results indicate the preferred use of the LEISH-F3+ protein for immune recognition among a greater proportion of L. donovani-impacted individuals and demonstrate the suitability of providing immunization coincident with AmBisome treatment. Although our preclinical data did not indicate any clear or strong benefit in terms of clinical improvement in a suboptimal chemotherapy setting it also did not rule out the use of immunochemotherapeutic regimen. The model does not consider impact on VL sequelae such as relapse and PKDL and it remains to be determined if immunization at the time of chemotherapy can reduce these.