Leishmaniasis in the immunocompromised population: evaluation of strategies for screening and monitoring

Leishmaniasis is a vector-borne disease caused by an intracellular parasite of the genus Leishmania. The clinical features of leishmaniasis include a wide range of manifestation from asymptomatic infections to different levels of disease severity. In most cases individuals do not develop clinical symptoms, but Leishmania parasites can persist lifelong in the host after an acute infection and easily reactivate under immunosuppressive conditions, causing severe disease with high mortality rate. The aim of this study was to identify Leishmania infection in selected groups of immunocompromised (IC) patients, including newly diagnosed HIV infected individuals, patients receiving kidney transplant (KT) and patients undergoing immunosuppressive therapies for immune-mediated diseases (IMD). Our study focused on the validation of a combination of methods to be used for the screening of asymptomatic Leishmania infection. The selected methods included high sensitive Real-Time PCR for detection of parasitic kinetoplast (k)DNA in peripheral blood, Western Blot (WB) for detection of specific IgG and Whole Blood Assay (WBA) to evaluate the anti-leishmanial T-cell response by quantifying the production of IFN-γ, IL-2 and IP-10 after stimulation of patients’ blood with Leishmania specific antigens. The methods have been validated on a cohort of immunocompetent individuals living in an endemic area of the Bologna province. Among 145 individuals recruited and screened with WB, Real-Time PCR and WBA, 24 subjects tested positive (17%) to one or more methods, thus confirming the high circulation of the parasite in the selected area. Given the high prevalence of asymptomatic infection in immunocompromised patients in endemic regions such as Italy, it seems essential to develop a plan for screening and follow-up of Leishmania infection. The screening algorithm that we tested in this study appears to be effective to identify accurately quiescent parasitic infection.