Effects of heterogeneity of Leishmania tropica isolates in infected human macrophages

Leishmaniasis is a disease caused by protozoan parasites of the genus Leishmania. The significance of Leishmania tropica (late ulcerative) in human cutaneous leishmaniasis has been recognized only recently, whereas can visceralize and cause systemic illness. Virulence variability was investigated by analyzing the experimental pathogenicity of nine Leishmania tropica strains. BALB/c mice were injected in the hind footpad with metacyclic promastigotes and lesion progression was recorded weekly intervals. Parasite burden, in tissue or draining lymph nodes, was determined by impression smears and limiting-dilution assay. Furthermore, human macrophages were infected with metacyclic promastigotes for 48 and 72 h, afterwards the percentage of infected macrophages and the average numbers of amastigotes per one infected macrophage were determined. A great variety of infection profiles between strains were observed; five strains showed a progressive infection about 5 weeks prior to being controlled (parasite loads in footpads swelling and lymph nodes were 10-10 and 10-10 parasites/mg, respectively). One strain produced only moderate and transient swelling, three strains never produced lesions, after which time, nonhealing and nonulcerative lesions persisted for over 6 months. The relationship was observed between profile and growth characterization in vitro. The high virulence strain was characterized by a significantly higher ability to infect human macrophages and to survive with higher replication levels within the infected macrophages. These results suggest that L. tropica isolates from the field may differ in virulence. The characterization of parasite virulence appears to be related to intrinsic parasitic factors that can affect the pathology of leishmaniasis. [Narges Shahmohamma, Lame Akhlaghi, Reza Ranjbar, Ramtin Hadighi. Effects of heterogeneity of Leishmania tropica isolates in infected human macrophages. Life Sci J 2014;11(11s):762-767]. (ISSN:1097-8135). http://www.lifesciencesite.com. 165