The utility of pathogen inactivation technology: a real-life example of Leishmania infantum inactivation in platelets from a donor with an asymptomatic infection.

Visceral leishmaniasis is typically caused by Leishmania infantum (L. infantum) in the Mediterranean littoral. The majority of infections with L. infantum are asymptomatic and resolve spontaneously in individuals with normal immune systems. A minority progress to classic, full-blown visceral leishmaniasis, known in many areas as kalaazar1,2. Leishmania infection is most often transmitted to humans via the bite of the phlebotomine female sand fly, however transmission of Leishmania by transfusion has also been reported3–13. Populations at risk of clinically apparent disease caused by L. infantum after insect bites or transfusion include infants and immunosuppressed patients. Most cases of transfusion-transmitted leishmaniasis have been reported in endemic areas and, because the infection is often asymptomatic in healthy individuals, it is difficult to calculate the transmission risk precisely. The existence of cryptic Leishmania infections, associated with intermittent low density circulation of the parasite 1,14, has been the main cause of transmission by blood. In the Balearic Islands, our region, the prevalence of asymptomatic L. infantum infection in blood donors is high (11% of blood donors tested had a positive reaction to the delayed-type hypersensitivity test, 3.1% had specific antibodies and L. infantum DNA was detected in the blood of 5.9% of donors studied)15 which is in agreement with other findings regarding asymptomatic individuals from the Mediterranean region1,16,17. Although some research studies have investigated Leishmania infection in blood donors1,14–17, currently there is no suitable Leishmania donor screening test that meets Blood Bank requirements with respect to aspects such as speed, automation and standardisation. At present, the only measure applied to prevent transmission-transfusion leishmaniasis is based on donor selection criteria. According to the “Guide to Preparation, Use and Quality Assurance of Blood Components” from the European Committee on Blood Transfusion, as well as the Spanish Regulation on Blood Donation, the strategy adopted in Europe is based on permanent deferral for donors who have had or currently have visceral leishmaniasis. In other countries, such as the USA, donors are deferred for a period of 1 year from the date of their last departure from an endemic country. Since there is currently no adequate donor screening test for Leishmania, several methods have been used to inactivate Leishmania in blood products18–20 and to eliminate the parasites through filtration using whole blood, fresh plasma and red blood cell (RBC) leucodepletion systems15,21–23. As an approach to reducing the risk of transfusion-related transmission in our area, we investigated the ability of pathogen inactivation technology using riboflavin and ultraviolet light to eliminate L. infantum in apheresis platelet units obtained from an asymptomatic infected blood donor. This is the first report on the utility of pathogen inactivation technology in the elimination of a parasite from a blood component collected from an asymptomatic infected blood donor.