Biomarkers for intracellular pathogens: establishing tools as vaccine and therapeutic endpoints for visceral leishmaniasis

Abstract

Visceral leishmaniasis (VL) in South Asia is a serious disease affecting children and adults. Acute VL develops in only a fraction of those infected individuals, the majority being asymptomatic with the potential to transmit infection and develop disease. We followed 56 individuals characterized as being asymptomatic by sero-positivity with rk39 RDT in a hyper endemic district of Bangladesh to define the utility of Leishmania-specific antibodies and DNA in identifying infection. At baseline, 54 of the individuals were sero-positive with one or more quantitative antibody assays and antibody levels persisted at follow-up. Most sero-positive individuals (47/54) tested positive by qPCR at baseline, but only 16 tested positive at follow-up. The discrepancies among the different tests may shed light on the dynamics of asymptomatic infections of L. donovani, as well as underscore the need for standard diagnostic tools for active surveillance as well as assessing the effectiveness of prophylactic and therapeutic interventions.

From mouse to man: safety, immunogenicity and efficacy of a candidate leishmaniasis vaccine LEISH‐F3+GLA‐SE

“…Subjects were defined according to parameters set by the Kala‐Azar Elimination Program as follows: VL, a person with clinical symptoms of VL (fever for more than 2 weeks duration and splenomegaly) and a positive rK39 RDT result; asymptomatic individual, a person from an endemic area with no present or past clinical symptoms of VL but with a DAT titer >600; non‐endemic, healthy individuals living out with endemic regions reporting no history of VL. ELISA was conducted as previously described with the sera at a 1:400 dilution 82 …”

“…ELISA was conducted as previously described with the sera at a 1:400 dilution. 82 Intracellular cytokine staining: PBMCs were isolated from peripheral blood of the subjects following the standard Ficoll procedure. PBMCs were stimulated with NH and SMT, phosphate-buffered saline, with costimulatory antibodies CD28 and CD49d (BD Biosciences, San Jose, CA, USA), in complete RPMI at 37°C.…”

Systematic Review of Biomarkers To Monitor Therapeutic Response in Leishmaniasis

“…Besides the drawback of the long half-lives of antibodies, antibody detection tests tend to be positive in a significant proportion of noninfected or otherwise asymptomatic individuals living in areas where VL is endemic (135,155,156). Due to these crucial limitations in the use of antibodies to monitor therapies, these markers are excluded from Table 3.…”

Leishmania vaccine development: exploiting the host–vector–parasite interface

“…Demonstrating prevention of infection may be possible in areas with high rates of transmission, but will require surveillance with sensitive and specific tools to monitor asymptomatic infection and progression from negative to positive during one or more transmission seasons (69, 70). Although effective VL diagnostics for detecting disease have been widely available for years (71–76), only recently has the promise of sensitive and specific tools for monitoring early and low level infection been demonstrated (77). …”