Presence of Leishmania braziliensis in blood samples from cured patients or at different stages of immunotherapy

Leishmania braziliensis is the cause for cutaneous leishmaniasis that afflicts thousands of people in South America. Patients suffering from this disease can get treatment, but after clinical treatment many patients show recurrent lesions a few years later. This is thought to happen because of reactivation of a persistent infection or reinfection. Reactivation of a persistent infection can occur by failure of the initial treatment or weak host immune response. Recurrent lesions could also be occurring because of L. braziliensis being a well adapting parasite that, unless a metabolic or an immunological imbalance occurs, can develop an equilibrium with its host. In order to test if leishmaniasis relapses are due to a persistent infection or because of L. braziliensis being adaptive, a study using blood PCR assays of patients who were in different stages of immunotherapy was conducted (Guevara et al. 1994).

Patients in this study were positively diagnosed for cutaneous leishmaniasis by microscopic observation of macrophages that contained L. braziliensis amastigotes in skin biopsies. Patients were at different stages of immunotherapy during the time of this experiment. Blood samples from each patient were extracted and centrifuged. The blood was then pipetted into an agrose PCR gel and electrophoresis was performed (Guevara et al. 1994).

            The results of this study showed that the presence of L. braziliensis found in cured patients is due either to a persistent infection or reinfection. The results support a persistent infection more, but reinfection could not be ruled out because patients still live in the same endemic area. An adaptive quality was ruled out because treatment is still effective in eliminating a large portion of the disease even after multiple treatments, so the parasite was not adapting to immunity against the treatment. In a previous work by Guevara et al. (1994), asymptomatic subjects were found harboring Leishmania DNA and the patients were immunoresponsive. These observations support the view that L. braziliensis is a difficult parasite to eliminate and that the infection is persistent (Guevara et al. 1994). 

This article relates to the study by Samuelson et al. (1991) “A Mouse Model of Leishmania braziliensis braziliensis Infection Produced by Coinjection with Sand Sly Saliva” because Samuelson et al. (1991) studied the transmission and intensity of Leishmania braziliensis infections while Guevara et al. (1994) studied the resilience and persistence of this infection. Both studies focused on specific aspects of L. braziliensis infections and are useful in studying this parasite’s ability to infect people and remain in the human body.

Citation

P. Guevara, E. Rojas, N. Gonzalez, J. Scorza, N. Anez, M. Valera, J. Ramirez, 1994, Presence of Leishmania braziliensis in blood samples from cured patients or at different stages of immunotherapy, Clinical and Diagnostic Laboratory Immunology, 1 (4): 385-389

-Kaitlin Smith