J.P. Dedet

Epidemiological aspects of human cutaneous leishmaniasis in French Guiana

A follow-up study of 219 patients infected with parasitologically confirmed cutaneous leishmaniasis in French Guiana was made between 1981 and 1987. Cutaneous leishmaniasis appeared to be common in young male adults entering the forest for professional activities (84.2% of the cases). The lesions were generally of the classical ulcerative type. They were limited to the skin and preferentially located on the legs and forearms (20.7% and 19.8% respectively). Most of the cases (86.6%) represented primary infections, but 6.8% had a recurrent lesion at the site of an old, previously cured lesion.

Cell populations in the lesion of human cutaneous leishmaniasis: a light microscopical, immunohistochemical and ultrastructural study.

To characterize the in situ cellular immune response in localized cutaneous leishmaniasis (LCL), the authors studied frozen skin biopsies from 50 patients with LCL due toLeishmania braziliensis guyanensis. A panel of 31 monoclonal antibodies was used, which defined the number and distribution of inflammatory cell subsets. Skin inflammatory infiltrates were composed of T cells (with a local CD4/CD8 ratio of 1.05±0.7 vs 1.48±0.3 in peripheral blood), macrophages and a smaller number of B cells, natural killer cells and granulocytes. Most of the T cells expressed activation markers (interleukin-2 and transferrin receptors, HLA-DR+) and an increase in T-cell-receptorγδ expression was noted. Analysis of the CD4+ subpopulations with newly available reagents showed that helper T cells (CD4+CD45RO+) exceeded the suppressor/inducer subset (CD4+CD45RA+) by 1.4∶1. There were no differences between local immune variables from patients with primary infection (45 patients) and those with recurrence (5). In 7 patients, biopsies were analysed before and 1 month after specific treatment, and did not show significant differences except for a small increase of dermal CD1a+ (Langerhans) cells/mm2. The observed pattern of cellular skin infiltration suggests an immune-mediated tissue injury including T-cell-mediated cytotoxicity and delayed hypersensitivity reactions in addition to direct parasitic action.

Fifteen years of cutaneous and mucocutaneous leishmaniasis in Bolivia: a retrospective study

This paper present the results of a retrospective study of cases of cutaneous and mucocutaneous leishmaniasis in Bolivia between 1975 and 1991. The total number of cases reported was 4058, 739 of which were mucous. Three different areas of endemic leishmaniasis are defined in Bolivia.

Isoenzyme characterization of 112 Leishmania isolates from French Guiana

112 Leishmania isolates, obtained in French Guiana from human lesions, phlebotomine sandflies and wild mammals, were characterized by isoenzyme electrophoresis. Leishmania braziliensis guyanensis and L. mexicana amazonensis were found parasitizing different natural hosts. L.b. guyanensis was the dominant species (103 isolates) responsible for most of the human lesions (96.7%). Based on variations observed in 2 enzymes, 3 distinct zymodemes were distinguished within the L.b. guyanensis taxon.

Opsonic activity of ascitic fluids from Plasmodium falciparum-infected Saimiri monkey: Positive correlation with protection in passive transfer assay

An investigation into the protective activity of ascitic fluids from Saimiri monkeys infected with Plasmodium falciparum and the role played by opsonins in that activity was undertaken. P. falciparum-parasitized blood was collected from splenectomized Saimiri (when parasitaemia reached at least 20% or more) and used in an in vitro phagocytic assay including ascitic fluid and cultures of peripheral blood monocytes from normal Saimiri. Under the conditions of this in vitro assay, we found that ascitic fluid phagocytosis-promoting factors were opsonic rather than cytophilic. The opsonic activity was highly specific for parasitized red blood cells and was effective against all stages of development of the parasite. A highly positive relationship between in vitro opsonizing activity and in vivo protective capacity of immune ascitic fluid was found.

Isolation of Leishmania species from wild mammals in French Guiana

Between 1981 and 1987, 486 wild mammals collected from 13 sites in French Guiana were examined for Leishmania. Eleven of 31 two-toed sloths, Choloepus didactylus, were infected, 4 of the isolates being identified as L. braziliensis guyanensis. This species was also found in 2 Didelphis marsupialis and 2 Proechimys sp. L. mexicana amazonensis was isolated from 3 Proechimys sp., 2 of which were P. cuvieri. The role of these mammals in the life cycles of the 2 anthropotropic species of Leishmania encountered in French Guiana is discussed.

Isoenzyme characterization of Leishmania braziliensis braziliensis isolates obtained from Bolivian and Peruvian patients

Thirty-four Leishmania isolates obtained from Bolivian and Peruvian patients infected with mucocutaneous leishmaniasis were characterized by isoenzyme electrophoresis using 10 enzymatic markers; all belonged to the subspecies L.b. braziliensis. Three isolates showed marked variation compared with the reference strain with respect to 5 or 6 enzymes. These variant isolates originated from patients with forms of the disease which were unresponsive to treatment.

Killer cells in human cutaneous leishmaniasis

In French Guiana, American cutaneous leishmaniasis is localized in the skin. The host response appears to be effective since few extra- or intracellular organisms can be found in tissue lesions, and we never observed any cutaneous dissemination or visceral involvement. However, this response is not fully effective since lesions may last for months. By using immunoperoxidase techniques and monoclonal antibodies directed against various cell populations, we examined the local immune response in skin biopsies. We found a high percentage of cells with the K/NK phenotype, a variable but usually high percentage of cells with the T cell phenotype bearing TAC receptors, and moderate numbers of monocytes and B cells. These results suggest that K/NK cells could play a role in the local control of parasite dissemination.

Parasitological diagnosis of mucocutaneous leishmaniasis due to Leishmania b. braziliensis in Bolivia

Parasitological diagnosis, using stained smears, culture and pathological examination of biopsy, was studied in 146 patients infected with mucocutaneous leishmaniasis, in Bolivia and Peru. The most efficient parasite detecting technique appeared to be the smear examination in cutaneous lesions (33% positive) and the pathology in case of mucous lesions (28% positive). In both, cutaneous and mucous lesions, the parasites were found most frequently in old lesions.

Long-term protection of squirrel monkeys (Saimiri sciureus) againstPlasmodium falciparum challenge inoculations after various time intervals

When used as an experimental host forPlasmodium falciparum, the squirrel monkeySaimiri sciureus, intact or splenectomized, develops a significant, long-lasting, protective immunity against the blood stages of this parasite. In the present study, this length of protection after a single initial infection was determined by test infections carried out at varying intervals of time in 26 splenectomized animals. An initial period of about 7 months was observed, which was characterized by a marked resistance to trial reinfestations by a homologous as well as a heterologous strain. A second period was observed during which the primates became sensitive to the parasite in varying degrees. These observations single out the squirrel monkey in comparison with other experimental hosts tested under similar conditions and underline the value of research on antimalarial vaccinations, because when confronted with parasite antigens, the organism can produce the immunological response necessary to control a test infection.