Leishmanial Strains Research Articles

Experimental murine infection with the diffuse cutaneous leishmaniasis strain, Isabel.

Infection with the Isabel strain of Leishmania has been followed in several inbred strains of mice over an extended period. The mouse strains segregate into three major types with respect to susceptibility to infection: BALB/c, BALB.B and SWR/J are susceptible; DBA/1J is intermediate; and C57BL/6, C57BL/10, DBA/2J and B10.D2 are resistant. Infections with other leishmanial strains have been well-characterized in the BALB/c mice. Therefore, BALB/c mice were selected for extended studies. Progression of the disease was assessed by the following parameters: (1) numbers of parasites isolated from various tissues including footpad lesions, spleens, and lymph nodes and (2) the presence of metastatic lesions. This model should prove valuable in the study of the early immunological events in leishmaniasis.

A spectrum in the susceptibility of leishmanial strains to intracellular killing by murine macrophages.

The susceptibility of 26 strains and clones of Leishmania to in vitro killing by lymphokine (LK)-activated macrophages was determined. A spectrum in the susceptibility of Leishmania to macrophage killing was observed. Some leishmanias were completely resistant to killing, including some but not all of the L. mexicana strains studied. This resistance was expressed in amastigotes and stationary growth-phase promastigotes, but not in logarithmic promastigotes. In contrast, some L. braziliensis parasites failed to survive within either activated or nonactivated macrophages. Between these two extremes were strains that survived within nonactivated macrophages, but were readily killed within activated macrophages. These included L. donovani, L. major, and some L. mexicana strains. Finally, one L. mexicana strain (WR357) was found to be susceptible to killing at high LK concentrations, but was relatively resistant at lower LK concentrations or at cutaneous temperatures. The observed differences in susceptibility to macrophage-mediated microbicidal activity may explain, in part, the variable pathogenesis of leishmanial infections.

Leishmaniasis in Israel: reservoir hosts, sandfly vectors and leishmanial strains in the Negev, Central Arava and along the Dead Sea

The reservoir animals, sandfly vectors and strains of Leishmania from foci in the southern region of Israel were studied. The rodent host species are: Psammomys obesus, Meriones crassus and probably Nesokia indica. The vector species are Phlebotomus papatasi, which were caught at all collecting sites and Ph. sergenti, which were collected in the area of the Dead Sea and in the Central Arava. Strains of Leishmania major isolated from rodents, vectors and man were serologically and enzymologically identical with regard to their excreted factor (EF) serotypes, their malate dehydrogenase (MDH), glucose-phosphate isomerase (GPI) and glucose-6-phosphate dehydrogenase (G6PDH) enzyme variant types, but exhibited three variant subtypes of 6-phosphogluconate dehydrogenase (6PGDH). The distribution of the 6PGDH subtypes correlates with three different geographical locations. Scarcity of water is the main factor limiting the biotopes of the sandflies and the spread of leishmaniasis. The subjects discussed are the dependence of sandfly distribution on rodent-burrow depth in arid areas and the inter-relationship between the leishmanial subtypes, vectors and hosts.

Surface reaction ofLeishmania

Eukaryotic parasites, including species of Leishmania, acquire or synthesize carbohydrate moieties similar to human blood group antigens. Leishmanial strains separate into three serotypes: A, B and AB. All strains containing the A component are agglutinated by Ulex europaeus lectin. Inhibition by haptene sugar suggests that a Ulex II-like receptor is involved. Organic solvents, but not protease treatment, remove its reactivity, suggesting that the receptor is a glycolipid.

Resistance to macrophage-mediated killing as a factor influencing the pathogenesis of chronic cutaneous leishmaniasis.

Cutaneous leishmaniasis can be either a spontaneously healing or chronic disease, depending upon the strain of parasite and the immunological status of the host. We have investigated parasite factors responsible for the variable pathogenesis observed in leishmanial infections by testing the sensitivity of several leishmanial strains to intracellular killing in lymphokine (LK) activated mouse macrophages. Significant microbicidal activity against Leishmania tropica, a strain which heals in C57BL/6 (B6) mice, was found. In contrast, a strain (Maria) which has previously been shown to induce chronic nonhealing cutaneous lesions in B6 mice was resistant to killing in activated macrophages. This resistance to killing was observed in macrophages activated by LK obtained from either Bacille Calmette-Guérin-, L. tropica, or the Maria strain infected mice. The inability of LK activated macrophages to kill the Maria strain was shown not to be due to parasite induced inhibition of killing mechanisms, since Maria strain infected, LK treated macrophages exhibited tumoricidial activity similar to uninfected macrophages. Furthermore, LK activated macrophages simultaneously infected with the Maria strain and another intracellular pathogen, Toxoplasma gondii, killed Toxoplasma, but not the Maria strain. Temperature was also found to significantly influence the multiplication and killing of Leishmania parasites. As would be expected from their cutaneous nature, L. tropica and Maria strain parasites multiplied better at 35 degrees C than at 37 degrees C. Also consistent with the failure of cutaneous strains to visceralize in immunocompetent mice was the observation that the killing of leishmanial parasites was enhanced at the higher temperature. Thus, the temperature dependent growth capacity and sensitivity to killing of a given leishmanial strain in macrophages may be important factors influencing the pathogenesis of cutaneous leishmaniasis.

Host and parasite factors influencing the expression of cutaneous leishmaniasis.

Host and parasite factors influencing the expression of cutaneous leishmaniasis were investigated in two murine models of different leishmanial diseases. The role of B lymphocytes in the uncontrolled disease manifested by BALB/c mice infected with cutaneous leishmaniasis was investigated in animals of this inbred strain depleted of B cells by neonatal administration of anti-mouse mu-chain antisera. Whereas non-depleted control mice developed chronic metastatic infections with both Leishmania tropica and Leishmania mexicana and showed depressed delayed-type hypersensitivity when skin-tested with leishmanial antigens, the mu-suppressed mice controlled their initial lesions while displaying strong antigen-specific delayed-type hypersensitivity. These findings reveal an inverse relationship between humoral and cell-mediated immunity in the expression of chronic leishmaniasis and suggest that B lymphocytes or their products regulate the delayed-type hypersensitivity response to leishmanial infection. In a separate study, healing and chronic strains of Leishmania were compared for their susceptibility to killing by lymphokine-activated mouse peritoneal macrophages. Whereas amastigotes of the healing strains were readily destroyed by these macrophages, amastigotes of two Leishmania strains, previously shown to produce chronic infections in mice, were resistant to killing by the same cells. These findings suggest that the ability of certain leishmanial strains to induce chronic disease may result from their capacity to evade intracellular destruction by activated macrophages.

Surface reaction ofLeishmania

Leishmanial strains of mixed AB serotypes were tested by immunofluorescent techniques to determine if they comprise mixed populations of A and B organisms or whether each parasite carries both antigenic determinants. The strains used were classified as A1B2, A2B2, A3B2 and A4B2 by the behaviour of their excreted factor (EF) in double gel diffusion tests against standard A and B rabbit antisera. The results showed that all organisms of an AB strain were labelled with both fluorescent anti-A and anti-B sera and that such a population could be differentiated from an artificial mixture of A and B strains.

Leishmania spp.: Cellular levels and synthesis of polyamines during growth cycles

Polyamines were extracted from five different leishmanial strains ( Leishmania sp., L. tropica major, L. mexicana, and two L. donovani isolates) and identified as pulrescine, spermidine, and spermine by thin-layer chromatography and mass spectrometry. These sensitive methods were also used to demonstrate the conversion of radioactive putrescine into spermidine and spermine. As in other types of cells, polyamine levels fluctuated during the growth cycle, maximal levels being attained during the logarithmic growth phase. In the five leishmanial strains, which were members of four different serotypes, the spermidine—putrescine ratios also varied, and in two strains of the same serotype, polyamine ratios were practically identical, suggesting that polyamine characteristics might serve as a further criterion for strain identification and classification.

Epidemiological patterns of cutaneous leishmaniasis in Panama. I. Epidemics among small groups of settlers.

Epidemic of cutaneous leishmanniasis among a small group of people established in a Panamanian forested area was studied. The first settlers arrived in June 1971, and by June 1973 there were 37 persons, 33 of whom had no previous history of the disease. Epidemiological surveys were made in June 1973 and March 1974. The disease developed in 14 (42.4%) of the 33 susceptible persons by June 1973, with an exposure time ranging from one to 14 months. The last case occurred in April 1973, and no new cases were observed during the ensuing 11 months. Two (15.4%) of 13 dogs examined were found with cutaneous leishmaniasis, but none of 41 feral mammals studied, mainly terrestrial rodents, was infected. Four leishmanial strains characterized, three from patients and one from a dog, were identified as Leishmania braziliensis. Phlebotomine sandfly population composition was studied and the probable vectors involved in the transmission to man were determined.