Virulence Diversity of Leishmania Tropica Strains Isolated from Human Lesions in Syria

Virulence variability was investigated by analyzing the experimental pathogenicity of seven Leishmania tropica strains isolated from human lesions in Syria, through the evaluation of the infective ability, growth pattern and pathogenicity. Two of the strains presented higher levels of macrophage infection, increased promastigote replication in culture medium and as well as amastigote multiplication within macrophages were classified as the most virulent. The other strains exhibited either low virulence, with reduced infective capability and low replication levels, or an intermediate virulent phenotype showing mixed features similar to low and high virulent phenotypes. A correlation between the infectivity and growth dynamics of each strain and NO production was demonstrated. Strains with accentuated virulent phenotype induced lower levels of NO production and parasite killing. These results suggest that L. tropica isolates from human lesions may differ in Virulence phenotype which seems to be a characteristic of each strain.