Biomarkers of Safety and Immune Protection for Genetically Modified Live Attenuated Leishmania Vaccines Against Visceral Leishmaniasis – Discovery and Implications

Despite intense efforts there is no safe and efficacious vaccine against visceral leishmaniasis, which is fatal and endemic in many tropical countries. A major shortcoming in the vaccine development against blood borne parasitic agents such as Leishmania is the inadequate predictive power of the early immune responses mounted in the host against the experimental vaccines. Often immune correlates derived from in-bred animal models do not yield immune markers of protection that can be readily extrapolated to humans. The limited efficacy of vaccines based on DNA, sub-unit, heat killed parasites has led to the realization that acquisition of durable immunity against the protozoan parasites requires a controlled infection with a live attenuated organism. Recent success of irradiated malaria parasites as a vaccine candidate further strengthens this approach to vaccination. We developed several gene deletion mutants in L. donovani as potential live attenuated vaccines and reported extensively on the immunogenicity of LdCentrin1 deleted mutant in mice, hamsters and dogs. Additional limited studies using genetically modified live attenuated Leishmania parasites as vaccine candidates have been reported. However, for the live attenuated parasite vaccines, the primary barrier against widespread use remains the absence of clear biomarkers associated with protection and safety. Recent studies in evaluation of vaccines e.g., influenza and yellow fever vaccines, using systems biology tools demonstrated the power of such strategies in understanding the immunological mechanisms that underpin a protective phenotype. Applying similar tools in isolated human tissues such as PBMCs from healthy individuals infected with live attenuated parasites such as LdCen1-/- in vitro followed by human microarray hybridization experiments will enable us to understand how early vaccine-induced gene expression profiles and the associated immune responses are coordinately regulated in normal individuals

Identification and Characterization of Genes Involved in Leishmania Pathogenesis: The Potential for Drug Target Selection

Identifying and characterizing Leishmania donovani genes and the proteins they encode for their role in pathogenesis can reveal the value of this approach for finding new drug targets. Effective drug targets are likely to be proteins differentially expressed or required in the amastigote life cycle stage found in the patient. Several examples and their potential for chemotherapeutic disruption are presented. A pathway nearly ubiquitous in living cells targeted by anticancer drugs, the ubiquitin system, is examined. New findings in ubiquitin and ubiquitin-like modifiers in Leishmania show how disruption of those pathways could point to additional drug targets. The programmed cell death pathway, now recognized among protozoan parasites, is reviewed for some of its components and evidence that suggests they could be targeted for antiparasitic drug therapy. Finally, the endoplasmic reticulum quality control system is involved in secretion of many virulence factors. How disruptions in this pathway reduce virulence as evidence for potential drug targets is presented

Leptin Functions in Infectious Diseases

Leptin, a pleiotropic protein has long been recognized to play an important role in the regulation of energy homeostasis, metabolism, neuroendocrine function, and other physiological functions through its effects on the central nervous system (CNS) and peripheral tissues. Leptin is secreted by adipose tissue and encoded by the obese (ob) gene. Leptin acts as a central mediator which regulates immunity as well as nutrition. Importantly, leptin can modulate both innate and adaptive immune responses. Leptin deficiency/resistance is associated with dysregulation of cytokine production, increased susceptibility toward infectious diseases, autoimmune disorders, malnutrition and inflammatory responses. Malnutrition induces a state of immunodeficiency and an inclination to death from communicable diseases. Infectious diseases are the disease of poor who invariably suffer from malnutrition that could result from reduced serum leptin levels. Thus, leptin has been placed at the center of many interrelated functions in various pathogenic conditions, such as bacterial, viruses and parasitic infections. We review herein, the recent advances on the role of leptin in malnutrition in pathogenesis of infectious diseases with a particular emphasis on parasitic diseases such as Leishmaniasis, Trypanosomiasis, Amoebiasis, and Malaria

Immunity to Visceral Leishmaniasis Using Genetically Defined Live-Attenuated Parasites

Leishmaniasis is a protozoan parasitic disease endemic to the tropical and subtropical regions of the world, with three major clinical forms, self-healing cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL). Drug treatments are expensive and often result in the development of drug resistance. No vaccine is available against leishmaniasis. Subunit Leishmania vaccine immunization in animal models has shown some efficacy but little or none in humans. However, individuals who recover from natural infection are protected from reinfection and develop life-long protection, suggesting that infection may be a prerequisite for immunological memory. Thus, genetically altered live-attenuated parasites with controlled infectivity could achieve such memory. In this paper, we discuss development and characteristics of genetically altered, live-attenuated Leishmania donovani parasites and their possible use as vaccine candidates against VL. In addition, we discuss the challenges and other considerations in the use of live-attenuated parasites

A novel functional approach toward identifying definitive drug targets

The process of developing drugs dates to antiquity. The herbal formulations during the old days were more traditional than with any scientific rationale. As different branches of physics, chemistry and biology started revealing the physiological processes in molecular details and as the sophisticated methods for probing into these phenomena were innovated, the processes of drug development changed significantly. However, the very first step in the process which is defining a drug target remains a major hurdle. The classical methods that predate the functional genomics and proteomics involve a cumbersome, painstaking detailing of a given enzyme or a receptor, followed by its validation as a target. The sophisticated methods in the post-genomic and proteomic era reduced the time taken to define targets, but the speed of drug discovery is not necessarily as quick as it promised. This is primarily due to prolific predictions pressing validation too hard, although both non-robotic and robotic high throughput screenings match with the requirement. Since these drugs target pathogens, a serious disadvantage with these methodologies is the emergence of drug resistance. Therefore, we propose a functional approach whereby the host-pathogen interaction is studied to find out the alterations in immune responses, the profile of host gene expression and activation of cell signaling molecules, the kinases in particular. Such interactions often induce the expression of those genes and activation of those proteins which are required for their survival. We demonstrate that reversal of such profiles of gene expression and protein activation ameliorates the infection. Therefore, those gene products and the kinases with pro-parasitic functions can serve as targets

CONTROL SYSTEM OF CRYOGENIC PLANT FOR SUPERCONDUCTING CYCLOTRON AT VECC

Cryogenic Plant of Variable Energy Cyclotron Centre<br />consists of two Helium refrigerators (250W and 415W @<br />4.5K), valve box with sub-cooler and associated sub<br />systems like pure gas storage, helium purifier and impure<br />gas recovery etc. The system also consists of 3.1K liters<br />of liquid Nitrogen (LN2) storage and delivery system. The<br />plant is designed to cater the cryogenic requirements of<br />the Superconducting Cyclotron. The control system is<br />fully automated and does not require any human<br />intervention once it is started. EPICS (Experimental<br />Physics and Industrial Control System) architecture has<br />been adopted to design the Supervisory control and data<br />acquisition (SCADA) module. The EPICS Input Output<br />Controller (IOC) communicates with four Programmable<br />Logic Controllers (PLCs) over Ethernet based control<br />LAN to control/monitor 618 numbers of field Inputs/<br />Outputs(I/O). The plant is running very reliably round the<br />clock, however, the historical data trending of important<br />parameters during plant operation has been integrated to<br />the system for plant maintenance and easy diagnosis. The<br />400 KVA UPS with 10 minutes back up time have been<br />installed to keep the cryogenic system running with one<br />160KW cycle compressor during utility power<br />interruptions

Functional paradox in host-pathogen interaction dictates the fate of parasites

The interactions between the protozoan parasite Leishmania and host macrophages are complex and involve several paradoxical functions that are meant for protection of the host but exploited by the parasite for its survival. The initial interaction of the parasite surface molecules with the host-cell receptors plays a major role in the final outcome of the disease state. While the interactions between macrophages and a virulent strain of Leishmania trigger a cascade of cell-signaling events leading to immunosuppression, the interaction with an avirulent strain triggers host-protective immune effector functions. Thus, an incisive study on Leishmania-macrophage interactions reveals functional paradoxes that highlight the concept of 'relativity in parasite virulence'. Using Leishmania infection as a model, we propose that virulence of a pathogen and the resistance (or susceptibility) of a host to the pathogen are relative properties that equate to combinatorial functions of several sets of molecular processes