Diagnosis of Leishmania infection in a nonendemic area of South America

Network-Based Approaches Reveal Potential Therapeutic Targets for Host-Directed Antileishmanial Therapy Driving Drug Repurposing

Leishmania parasites are the causal agent of leishmaniasis, an endemic disease in more than 90 countries worldwide. Over the years, traditional approaches focused on the parasite when developing treatments against leishmaniasis. Despite numerous attempts, there is not yet a universal treatment, and those available have allowed for the appearance of resistance. Here, we propose and follow a host-directed approach that aims to overcome the current lack of treatment. Our approach identifies potential therapeutic targets in the host cell and proposes known drug interactions aiming to improve the immune response and to block the host machinery necessary for the survival of the parasite. We started analyzing transcription factor regulatory networks of macrophages infected with Leishmania major. Next, based on the regulatory dynamics of the infection and available gene expression profiles, we selected potential therapeutic target proteins. The function of these proteins was then analyzed following a multilayered network scheme in which we combined information on metabolic pathways with known drugs that have a direct connection with the activity carried out by these proteins. Using our approach, we were able to identify five host protein-coding gene products that are potential therapeutic targets for treating leishmaniasis. Moreover, from the 11 drugs known to interact with the function performed by these proteins, 3 have already been tested against this parasite, verifying in this way our novel methodology. More importantly, the remaining eight drugs previously employed to treat other diseases, remain as promising yet-untested antileishmanial therapies. IMPORTANCE This work opens a new path to fight parasites by targeting host molecular functions by repurposing available and approved drugs. We created a novel approach to identify key proteins involved in any biological process by combining gene regulatory networks and expression profiles. Once proteins have been selected, our approach employs a multilayered network methodology that relates proteins to functions to drugs that alter these functions. By applying our novel approach to macrophages during the Leishmania infection process, we both validated our work and found eight drugs already approved for use in humans that to the best of our knowledge were never employed to treat leishmaniasis, rendering our work as a new tool in the box available to the scientific community fighting parasites.

Cutaneous Leishmaniasis: Contribution of Routine Histopathology in Unexpected Encounters

The ulcerated papules of cutaneous leishmaniasis represent an unusual form of granulomatous dermatitis caused by Leishmania species, a protozoan transmitted by sandfly bites. As the disease is not native to North America, clinical suspicion is partially based on a compatible travel history and may result in a biopsy. The key role of standard morphology is the identification of Leishmania organisms, supplemented by Giemsa and/or CD1a immunostaining. Histologically, the organism may be confused with Histoplasma species, which is resolved by staining with methenamine silver or PAS. Four cases of cutaneous leishmaniasis are presented for which organisms were present in 3; polymerase chain reaction and DNA sequencing for speciation done by the Center for Disease Control and Prevention (CDC) was confirmatory in 3 cases, including the one case without histologically identifiable organisms. Rare unexplained cases of cutaneous leishmaniasis without a travel history have been reported outside endemic areas. The present cases emphasize the importance of diagnostic awareness of unusual infections such as this in the context of political unrest, ease of international travel, climate change and the possible expansion of geographic vector distribution. In the morphologic absence of organisms, the diagnosis may require molecular techniques, currently available on a referral basis to pathologists without charge from CDC.