M. L. Chance

The biochemical and serological taxonomy of Leishmania from the Aethiopian zoogeographical region of Africa.

The electrophoretic variation of the enzymes MDH, GPI, G6PGH, 6PGDH were determined for 68 strains of Leishmania isolated in the Aethiopian zoogeographical region. Other characters determined were the DNA buoyant density of nuclear and kinetoplast DNA and the excreted factor serotype. The strains could be readily identified on the basis of these characters thus assisting in the elucidation of epidemiological problems. On the basis of these characters the strains could be divided into six groups. Three of the groups corresponded to L. donovani s.l., L. major and L. aethiopica. The three other groups identified at present have no specific name associated with them.

The biochemical and serological taxonomy of visceralizing Leishmania.

Some intrinsic biochemical and serological characters of 84 leishmanial stocks isolated in the Old and New World from human visceral cases, dogs and wild animals thought to be reservoirs of human visceral leishmaniasis were determined, in an attempt to resolve some of the outstanding taxonomical and epidemiological problems associated with these parasites. The characters measured were nuclear and kinetoplast DNA buoyant densities, excreted factor (EF) serotypes and electrophoretic mobilities of the enzymes: malate dehydrogenase (MDH), glucose phosphate isomerase (GPI), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH), in most cases, and phosphoglucomutase (PGM), alkaline phosphatase (ALP) and nonspecific esterase (NSE) in selected representatives from each major geographical region considered.All but eight of the strains tested were biochemically and serologically similar; with some variation seen in single enzymes in a few cases and a serological difference seen in s...

New developments in the chemotherapy of leishmaniasis.

Several significant advances in the chemotherapy of leishmaniasis have occurred in the last 10 years. Some of these advances have arisen due to the greater awareness of the pharmacokinetic properties of drugs, such as the pentavalent antimonials, while others have resulted from the introduction of drugs new to the treatment of leishmaniasis, such as aminosidine which can be used both systemically and topically against cutaneous leishmaniasis. The most encouraging advance is the use of lipid-associated amphotericin B; very short treatments with these preparations have been shown to be effective. Other studies have shown the usefulness of combination therapy and the use of immune modulators. A number of biochemical pathways in Leishmania, such as those associated with purine and sterol metabolism, are known to be distinct from those of the mammalian hosts. These have been exploited in the search for the rational choice of anti-leishmanial agents.

Isolation of Leishmania major from Mastomys erythroleucus and Tatera gambiana in Senegal (West Africa)

Region Studied The region consisted of a large, enclosed, cultivated area belonging to the Monastery of Keur Moussa, near the city of Thies, in the Cap-verdienne region, where cutaneous leishmaniasis is endemic. This region was chosen because of the numerous cases of cutaneous leishmaniasis in the monastery and the neighbouring villages, and because of the presence of numerous rodent burrows. Twenty human strains were isolated between December 1976 and October 1977. By J.-P. DEDET AND F. DEROUIN Isolation of Leishmania major from Mastomys erythroleucus and Tatera gambiana in Senegal (West Africa)

Effects of long-term in vitro cultivation on the virulence of cloned lines of Leishmania major promastigotes

The virulences of several clones from a single Leishmania major strain were studied in BALB/c mice. Clones showed the same pattern of infectivity and virulence two months after cloning as the parental population. After prolonged in vitro culture, however, it was apparent that two types of virulent clones existed: although the level of virulence remained stable in some clones, in others, such as C-11, it progressively decreased, as in the parental population. The progressive loss in virulence in a continuously cultured mixed population was probably due to selection, as the initial mixture of a stable virulent clone and a stable avirulent clone eventually yielded a totally avirulent promastigote population. After cultivation for 12 months, neither clone C-11 nor the parental population produced lesions in inoculated mice but virulent parasites were recovered from the inguinal nodes of the mice, possibly as a result of selection in vivo for virulent parasites.

Species differentiation in the genus Leishmania by morphometric studies with the electron microscope.

Morphometric comparison of some ultrastructural features of leishmanial amastigotes demonstrated species-characteristic differences. These occurred in parameters relating to size, such as diameter and microtubule number; statistical analysis resolved four groups from the seven isolates studied. The results were not inconsistent with previous measurements, mostly with the light microscope, by other workers. The unqualified assertion that Leishmania species are morphologically identical is therefore no longer valid.

The isolation and identification of leishmanial parasites from domestic dogs in the Machakos District of Kenya, and the possible role of dogs as reservoirs of kala-azar in East Africa.

Two out of 288 sick and emaciated dogs from homesteads in the Machakos District of Kenya, where human kala-azar cases existed, were found to be infected with leishmaniasis. The leishmanial strain isolated from one of the dogs was characterized enzymologically and serologically and found to be identical with strains isolated from human kala-azar cases and Phlebotomus martini. The significance of these findings is discussed in terms of the general epidemiology of visceral leishmaniasis in Kenya.

Ultrastructural and biochemical characterization of stocks of Endotrypanum.

Using biochemical and ultrastructural parameters, seven strains of Endotrypanum were divided into two taxonomic units. However, this separation does not agree with the original identification of the stocks as either E. schaudinni or E. monterogeii. Clusters of discrete particles, 40–80 nm diameter, variable in shape and with a 14–18 nm thick electron-dense wall were observed in four of the stocks. One stock, isolated from a sandfly, Lutzomyia trapidoi, was identified as an Endotrypanum sp.

A time-course study of circulating antigen and parasite-specific antibody in cotton rats infected with Leishmania donovani

Levels of circulating antigen in a group of cotton rats infected with Leishmania donovani were followed over a 28-week period, using a modified, polyethylene-glycol (PEG) ELISA. Circulating antigen could be detected from 1 week post-infection and gradually increased over time. In infected cotton rats treated with a curative dose of Pentostam at 12 weeks post-infection, antigen levels peaked and then declined. Antigen was still detected in some of the treated animals at 28 weeks post-infection. The antibodies used in the PEG-ELISA were also used in a capture ELISA to detect parasite antigens in urine. Urine samples which were positive by capture ELISA were also analysed by western blotting, in an attempt to identify the parasite antigens present. Three components, of 45, 47 and 58 kDa, were detected.

Cutaneous leishmaniasis in the Libyan Arab Republic: distribution of the disease and identity of the parasite.

The endemicity of cutaneous leishmaniasis in northwest Libya was confirmed. Although the strains isolated from man had variable biological properties they were all biochemically similar according to the tests used. The Libyan strains resemble those of zoonotic cutaneous leishmaniasis in parts of the Middle East, but can be differentiated from urban or highland strains. It is suggested that the recent discovery of the disease is due partly to the improvement in medical services, and partly to the development of new areas of land for agriculture and housing.