Potential Biomarkers for Asymptomatic Visceral Leishmaniasis among Iraq-Deployed U.S. Military Personnel

Visceral leishmaniasis (VL) is a chronic infection caused by Leishmania (L.) donovani or L. infantum parasites. Despite having the infection, most individuals never develop the clinical disease and are able to control the parasite and remain asymptomatic. However, some progress to symptomatic VL, leading to death if untreated. The host immune response has a major role in determining the progression and severity of the clinical manifestations in VL; several immune biomarkers of symptomatic VL have been described with interferon-gamma release as a surrogate biomarker of host cellular immunity. However, new biomarkers to identify asymptomatic VL (AVL) are needed for the identification of people at risk for VL activation. In our study, levels of chemokine/cytokine in the supernatants of peripheral mononuclear blood cells (PBMC) from 35 AVL(+) Iraq-deployed participants, stimulated in vitro with soluble Leishmania antigen for 72 h, were assessed by a bead-based assay that allows the measurement of multiple analytes. PBMC of AVL-negative military beneficiaries were used as controls. Monocyte Chemoattractant Protein-1, Monokine Induced by Gamma Interferon and Interleukin-8, were detected at high levels in AVL(+) stimulated cultures from Iraq deployers compared to uninfected controls. Measurement of chemokine/cytokine levels can identify cellular immune responses in AVL(+) asymptomatic individuals.

Automated summary

Visceral leishmaniasis (VL) is a chronic infection caused by Leishmania parasites. Most individuals are asymptomatic, but some progress to symptomatic VL. The host immune response plays a major role in determining the progression and severity of VL. New biomarkers are needed to identify asymptomatic individuals at risk of developing VL. In this study, chemokine/cytokine levels were measured in peripheral mononuclear blood cells (PBMC) from AVL(+) individuals, and high levels of certain chemokines were detected compared to controls. Measurement of chemokine/cytokine levels can help identify cellular immune responses in asymptomatic VL individuals.