Decreased Frequency and Secretion of CD26 Promotes Disease Progression in Indian Post Kala-azar Dermal Leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) drug efficacy study landscape: A systematic scoping review of clinical trials and observational studies to assess the feasibility of establishing an individual participant-level data (IPD) platform

BACKGROUND

Post-kala-azar dermal leishmaniasis (PKDL) is a dermatosis which can occur after successful treatment of visceral leishmaniasis (VL) and is a public health problem in VL endemic areas. We conducted a systematic scoping review to assess the characteristics of published PKDL clinical studies, understand the scope of research and explore the feasibility and value of developing a PKDL individual patient data (IPD) platform.

METHODS

A systematic review of published literature was conducted to identify PKDL clinical studies by searching the following databases: PubMed, Scopus, Ovid Embase, Web of Science Core Collection, WHO Global Index Medicus, PASCAL, Clinicaltrials.gov, Ovid Global Health, Cochrane Database and CENTRAL, and the WHO International Clinical Trials Registry Platform. Only prospective studies in humans with PKDL diagnosis, treatment, and follow-up measurements between January 1973 and March 2023 were included. Extracted data includes variables on patient characteristics, treatment regimens, diagnostic methods, geographical locations, efficacy endpoints, adverse events and statistical methodology.

RESULTS

A total of 3,418 records were screened, of which 56 unique studies (n = 2,486 patients) were included in this review. Out of the 56 studies, 36 (64.3%) were from India (1983-2022), 12 (21.4%) from Sudan (1992-2021), 6 (10.7%) were from Bangladesh (1991-2019), and 2 (3.6%) from Nepal (2001-2007). Five (8.9%) studies were published between 1981-1990 (n = 193 patients), 10 (17.9%) between 1991-2000 (n = 230 patients), 10 (17.9%) between 2001-2010 (n = 198 patients), and 31 (55.4%) from 2011 onwards (n = 1,865 patients). Eight (14.3%) were randomised clinical trials, and 48 (85.7%) were non-randomised studies. The median post-treatment follow-up duration was 365 days (range: 90-540 days) in 8 RCTs and 360 days (range: 28-2,373 days) in 48 non-randomised studies. Disease diagnosis was based on clinical criterion in 3 (5.4%) studies, a mixture of clinical and parasitological methods in 47 (83.9%) and was unclear in 6 (10.7%) studies. Major drugs used for treatment were miltefosine (n = 636 patients), liposomal amphotericin B (L-AmB) (n = 508 patients), and antinomy regimens (n = 454 patients). Ten other drug regimens were tested in 270 patients with less than 60 patients per regimen.

CONCLUSIONS

Our review identified studies with very limited sample size for the three major drugs (miltefosine, L-AmB, and pentavalent antimony), while the number of patients combined across studies suggest that the IPD platform would be valuable. With the support of relevant stakeholders, the global PKDL community and sufficient financing, a PKDL IPD platform can be realised. This will allow for exploration of different aspects of treatment safety and efficacy, which can potentially guide future healthcare decisions and clinical practices.

Post kala-azar dermal leishmaniasis in the Indian sub-continent: challenges and strategies for elimination

Visceral leishmaniasis (VL) is a severe and often fatal form of leishmaniasis caused by Leishmania donovani in the Indian sub-continent. Post Kala-azar Dermal Leishmaniasis (PKDL) is a late cutaneous manifestation of VL, typically occurring after apparent cure of VL, but sometimes even without a prior history of VL in India. PKDL serves as a significant yet neglected reservoir of infection and plays a crucial role in the transmission of the disease, posing a serious threat to the VL elimination program in the Indian sub-continent. Therefore, the eradication of PKDL should be a priority within the current VL elimination program aimed at achieving a goal of less than 1 case per 10,000 in the population at the district or sub-district levels of VL endemic areas. To accomplish this, a comprehensive understanding of the pathogenesis of PKDL is essential, as well as developing strategies for disease management. This review provides an overview of the current status of diagnosis and treatment options for PKDL, highlighting our current knowledge of the immune responses underlying disease development and progression. Additionally, the review discusses the impact of PKDL on elimination programs and propose strategies to overcome this challenge and achieve the goal of elimination. By addressing the diagnostic and therapeutic gaps, optimizing surveillance and control measures, and implementing effective intervention strategies, it is possible to mitigate the burden of PKDL and facilitate the successful elimination of VL in the Indian sub-continent.

Cellular response to chemicals present in air pollution in occupationally exposed workers and its potential cancer susceptibility

The study aimed to evaluate the potential effects of the chronic exposure to chemical agents from air pollution on phenotypic and genotypic expressions of peripheral biomarkers and tumor-related proteins in mononuclear cells. This study evaluates 85 taxi drivers (outdoor workers) and 55 non-occupationally exposed persons (NOE) to air pollution (indoor workers). The biomarkers were urinary 1-hydroxypyrene (1-OHP), for organic agents, and blood As and Ni, for inorganic agents. Oxidative stress biomarkers; protein expression of ICAM-1 (CD54), β2-integrin, L-selectin (CD62-L), and MCP1; gene expression of ICAM-1, p53 and CD26 were performed. Urinary 1-OHP and blood As and Ni levels were increased in taxi drivers and were associated with inflammatory and oxidative stress biomarkers. These exposure biomarkers were also associated with each other, suggesting a common source of exposure. The gene expression of p53, CD26 and ICAM-1 were decreased in taxi drivers and were strongly associated between them, indicating a commom regulation point. The antioxidant non-protein thiols and lycopene were negatively associated with inflammatory biomarkers, maybe regulating the immune-response. We demonstrated, for the first time, that in occupational exposure to air pollution chemicals, oxidative and inflammatory processes are involved in the immune-regulatory process, and indirectly contribute to suppressing the p53 and CD26 expressions, increasing the risk of cancer development. On the other hand, antioxidants could contribute to improving the immune-regulation, but more studies are needed.

The role of Dipeptidyl Peptidase-4 in cutaneous disease

Dipeptidyl peptidase-4 (DPP4) is a multifunctional, transmembrane glycoprotein present on the cell surface of various tissues. It is present in multiple molecular forms including cell surface and soluble. The role of DPP4 and its inhibition in cutaneous dermatoses have been a recent point of investigation. DPP4 exerts a notable influence on T-cell biology, the induction of skin-specific lymphocytes, and the homeostasis between regulatory and effector T cells. Moreover, DPP4 interacts with a broad range of molecules, including adenosine deaminase, caveolin-1, CXCR4 receptor, M6P/insulin-like growth factor II-receptor and fibroblast activation protein-α, triggering downstream effects that modulate the immune response, cell adhesion and chemokine activity. DPP4 expression on melanocytes, keratinocytes and fibroblasts further alters cell function and, thus, has crucial implications in cutaneous pathology. As a result, DPP4 plays a significant role in bullous pemphigoid, T helper type 1-like reactions, cutaneous lymphoma, melanoma, wound healing and fibrotic disorders. This review illustrates the multifactorial role of DPP4 expression, regulation, and inhibition in cutaneous diseases.

Post kala-azar dermal leishmaniasis: A threat to elimination program

Leishmaniasis remains a public health concern around the world that primarily affects poor folks of the developing world spanning across 98 countries with mortality of 0.2 million to 0.4 million annually. Post kala-azar dermal leishmaniasis (PKDL) is the late skin manifestation of visceral leishmaniasis (VL). It has been reported that about 2.5% to 20% of patients recovered from VL develop PKDL having stilted macular or nodular lesions with parasites. In the Indian subcontinent (ISC), it manifests a few months after recovery from VL, though in Africa it can occur simultaneously with VL or a little later. New cases of PKDL are also observed without prior VL in the ISC. These individuals with PKDL represent an important but largely neglected reservoir of infection that perpetuates anthroponotic Leishmania donovani transmission in the ISC and can jeopardize the VL elimination program as these cases can infect the sand flies and spread the endemic. Therefore, it becomes imperative to eradicate PKDL as a part of the VL elimination program. With the limited treatment options besides little knowledge on PKDL, this review stands out in focusing on different aspects that should be dealt for sustained VL elimination.

SLC11A1 (rs3731865) polymorphism and susceptibility to visceral leishmaniasis in HIV-coinfected patients from Northeastern Brazil

Following the emergence of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS), the number of visceral leishmaniasis-HIV (VL-HIV) coinfections has increased worldwide, mainly in Brazil. The development of clinical forms of VL can be influenced by nutritional status, age, and host genetic factors, which are important variables determining susceptibility to disease. There are no studies with a candidate gene approach assayed directly in the VL-HIV-coinfected population. Herein, we determined and analyzed the associations of SLC11A1, LECT2, CCL1, CCL16, and IL4 genetic polymorphisms with susceptibility to VL-HIV coinfection in Northeastern Brazil. We analyzed 309 DNA samples extracted from the peripheral blood of HIV patients, and clinical and hematological data were collected from medical records. The diagnosis of VL was confirmed in 110 out of 309 patients; genotyping was carried out by TaqMan assays afterwards. Our results confirmed the association between the SLC11A1 polymorphism (rs3731865) and VL-HIV coinfection (p = 0.0206, OR 1.8126, 95% CI 1.1050-2.9727). In addition, the SLC11A1 genotype GG (p = 0.0050, OR 3.0395, 95% CI 1.4065-6.5789) and CD4+ T lymphocyte count (p = 0.0030, OR 0.9980, 95% CI 0.9970-0.9990) were associated with VL-HIV coinfection in a multivariate model. The polymorphism of the SLC11A1 gene (rs3731865) was associated with VL-HIV coinfection, suggesting a possible genetic mechanism involved in the susceptibility to VL in HIV patients. This finding can suggest new therapeutic targets and genetic markers for the VL-HIV-coinfected population.

Impaired activation of lesional CD8+ T-cells is associated with enhanced expression of Programmed Death-1 in Indian Post Kala-azar Dermal Leishmaniasis

Post Kala-azar dermal leishmaniasis (PKDL), caused by Leishmania donovani is the dermal sequel of Visceral Leishmaniasis and importantly, is the proposed disease reservoir. The survival of Leishmania parasites within monocytes/macrophages hinges on its ability to effectively nullify immune activation mechanisms. Thus, delineating the disease-promoting immune mechanisms can facilitate development of immunotherapeutic strategies. Accordingly, in the absence of an animal model, this study aimed to delineate the status of CD8⁺ T-cells in patients with PKDL. At disease presentation, the absence of CD4⁺ T-cells at lesional sites was concomitant with an overwhelming infiltration of CD8⁺ T-cells that demonstrated an absence of Perforin, Granzyme and Zap-70, along with an enhanced expression of Programmed Death-1 (PD-1) and the skin-homing CCL17. Additionally, the lesional CCR4⁺CD8⁺ population was associated with an enhanced expression of IL-10 and IL-5. In circulation, the enhanced CD8⁺CCR4⁺ T-cell population and raised levels of CCL17/22 was associated with an increased frequency of PD-1, while CD127 was decreased. Taken together, in PKDL, the enhanced plasma and lesional CCL17 accounted for the dermal homing of CD8⁺CCR4⁺ T-cells, that along with a concomitant upregulation of PD-1 and IL-10 mediated immune inactivation, emphasizing the need for designing immunotherapies capable of reinvigorating T-cell potency.

A third generation vaccine for human visceral leishmaniasis and post kala azar dermal leishmaniasis: First-in-human trial of ChAd63-KH

BACKGROUND

Visceral leishmaniasis (VL or kala azar) is the most serious form of human leishmaniasis, responsible for over 20,000 deaths annually, and post kala azar dermal leishmaniasis (PKDL) is a stigmatizing skin condition that often occurs in patients after successful treatment for VL. Lack of effective or appropriately targeted cell mediated immunity, including CD8+ T cell responses, underlies the progression of VL and progression to PKDL, and can limit the therapeutic efficacy of anti-leishmanial drugs. Hence, in addition to the need for prophylactic vaccines against leishmaniasis, the development of therapeutic vaccines for use alone or in combined immuno-chemotherapy has been identified as an unmet clinical need. Here, we report the first clinical trial of a third-generation leishmaniasis vaccine, developed intentionally to induce Leishmania-specific CD8+ T cells.

METHODS

We conducted a first-in-human dose escalation Phase I trial in 20 healthy volunteers to assess the safety, tolerability and immunogenicity of a prime-only adenoviral vaccine for human VL and PKDL. ChAd63-KH is a replication defective simian adenovirus expressing a novel synthetic gene (KH) encoding two Leishmania proteins KMP-11 and HASPB. Uniquely, the latter was engineered to reflect repeat domain polymorphisms and arrangements identified from clinical isolates. We monitored innate immune responses by whole blood RNA-Seq and antigen specific CD8+ T cell responses by IFNγ ELISPOT and intracellular flow cytometry.

FINDINGS

ChAd63-KH was safe at intramuscular doses of 1x1010 and 7.5x1010 vp. Whole blood transcriptomic profiling indicated that ChAd63-KH induced innate immune responses characterized by an interferon signature and the presence of activated dendritic cells. Broad and quantitatively robust CD8+ T cell responses were induced by vaccination in 100% (20/20) of vaccinated subjects.

CONCLUSION

The results of this study support the further development of ChAd63-KH as a novel third generation vaccine for VL and PKDL.

TRIAL REGISTRATION

This clinical trial (LEISH1) was registered at EudraCT (2012-005596-14) and ISRCTN (07766359).

Possibilities and challenges for developing a successful vaccine for leishmaniasis

Leishmaniasis is a vector-borne disease caused by different species of protozoan parasites of the genus Leishmania. It is a major health problem yet neglected tropical diseases, with approximately 350 million people worldwide at risk and more than 1.5 million infections occurring each year. Leishmaniasis has different clinical manifestations, including visceral (VL or kala-azar), cutaneous (CL), mucocutaneous (MCL), diffuse cutaneous (DCL) and post kala-azar dermal leishmaniasis (PKDL). Currently, the only mean to treat and control leishmaniasis is by rational medications and vector control. However, the number of available drugs is limited and even these are either exorbitantly priced, have toxic side effects or prove ineffective due to the emergence of resistant strains. On the other hand, the vector control methods are not so efficient. Therefore, there is an urgent need for developing a safe, effective, and affordable vaccine for the prevention of leishmaniasis. Although in recent years a large body of researchers has concentrated their efforts on this issue, yet only three vaccine candidates have gone for clinical trial, until date. These are: (i) killed vaccine in Brazil for human immunotherapy; (ii) live attenuated vaccine for humans in Uzbekistan; and (iii) second-generation vaccine for dog prophylaxis in Brazil. Nevertheless, there are at least half a dozen vaccine candidates in the pipeline. One can expect that, in the near future, the understanding of the whole genome of Leishmania spp. will expand the vaccine discovery and strategies that may provide novel vaccines. The present review focuses on the development and the status of various vaccines and potential vaccine candidates against leishmaniasis.