R. Lainson

Immunopathogenic competences of Leishmania (V.) braziliensis and L. (L.) amazonensis in American cutaneous leishmaniasis

The immunopathogenic competences of Leishmania (V.) braziliensis and L. (L.) amazonensis were reviewed in the light of more recent features found in the clinical and immunopathological spectrum of American cutaneous leishmaniasis. It was shown a dichotomy in the interaction between these Leishmania species and human T‐cell immune response; while L. (V.) braziliensis shows a clear tendency to lead infection from the localized cutaneous leishmaniasis (LCL), a moderate T‐cell hypersensitivity form at the centre of the spectrum, toward to the mucocutaneous leishmaniasis (MCL) at the T‐cell hypersensitivity pole and with a prominent Th1‐type immune response, L. (L.) amazonensis shows an opposite tendency, leading infection to the anergic diffuse cutaneous leishmaniasis (ADCL) at the T‐cell hyposensitivity pole and with a marked Th2‐type immune response. Between the central LCL and the two polar MCL and ADCL, the infection can present an intermediary form known as borderline disseminated cutaneous leishmaniasis, characterized by an incomplete inhibition of T‐cell hypersensitivity but with a evident supremacy of Th1 over Th2 immune response (Th1u2003≥u2003Th2). These are probably the main immunopathogenic competences of L. (V.) braziliensis and L. (L.) amazonensis regarding the immune response dichotomy that modulates human infection outcome by these Leishmania parasites.

Leishmaniasis in Brazil: XVI. Isolation and identification of, Leishmania species from sandflies, wild mammals and man in north Pará State, with particular reference to L. braziliensis guyanensis causative agent of “pian-bois”

A total of 125 wild mammals (14 different species) were examined for evidence of infection with Leishmania in an area of primary forest highly endemic for pian-bois, due to Leishmania braziliensis guyanensis, in north Pará State, Brazil. Parasites isolated were characterized biologically, and biochemically on enzymic profiles. L. b. guyanensis was isolated from the viscera of one lesser anteater (Tamandua tetradactyla) and one opossum (Didelphis marsupialis), and the skin of one rodent (Proechimys guyannensis). The isolates were indistinguishable from 10 others previously made from the sandfly vectors Lutzomyia umbratilis (five) and Lu. whitmani (five), and nine isolates from field-workers who became infected during these studies. Leishmania mexicana amazonensis was obtained from the skin of 21 animals, including three species of opossums (D. marsupialis, Philander opossum and Metachirus nudicaudatus) and two species of rodents (proechimys guyannensis and Dasyprocta sp.). A peripylarian Leishmania isolated from the viscera of two armadillos (Dasypus novemcinctus) was shown to be different, biologically and biochemically, from L. b. guyanensis and L. m. amazonensis. Four other isolates of Leishmania, from the rodents Rhipidomys leucodactylus (one) and P. guyannensis (three) have yet to be characterized owing to their very poor growth in both hamster skin and in vitro culture: they appear closest, however, to L. braziliensis braziliensis. The complexity of Amazonian leishmaniasis is discussed, and attention drawn to the importance of edentates as reservoir hosts of some leishmanias in the New World. Whereas L. mexicana subspecies appear largely restricted to the skin of their natural hosts, subspecies of L. braziliensis are commonly found in the viscera.

Some methods for the enzymic characterization of Latin-American Leishmania with particular reference to Leishmania mexicana amazonensis and subspecies of Leishmania hertigi

30 Brazilian stocks of Leishmania mexicana amazonensis and 13 stocks of subspecies of Leishmania hertigi were characterized by starch-gel electrophoresis, using 18 enzymes selected from a total of 36 investigated. L. m. amazonensis was separable from subspecies of L. hertigi by enzymic profiles of 11 enzymes. The L. m. amazonensis stocks, which were from a wide range of hosts in a large geographical area, were enzymically extremely homogeneous, and could only be subdivided on two enzymes; sub-groups did not relate to each other or to any differences in epidemiological characters, including the clinical form of the human disease. 12 stocks regarded as L. hertigi deanei, that were isolated from Coendou prehensilis prehensilis and Coendou sp. in Pará State, Brazil, were separable into two sub-groups by three enzymes. A single stock of L. hertigi hertigi from Panama was separable from both enzymic sub-groups of L. h. deanei, in each case by three enzymes. The significance of these and other characters of diversity is discussed, together with the use of enzymes for the identification of the leishmaniae.

Chagas's disease in the Amazon Basin. II. The distribution of Trypanosoma cruzi zymodemes 1 and 3 in Para State, north Brazil.

In Pará State, Brazil, 123 Trypanosoma cruzi stocks were isolated from 12 silvatic mammal species, five silvatic triatomine species and individuals with acute Chagass disease. 100 T. cruzi stocks were identified as zymodeme (Z) 1, 17 as Z3 and 6 as Z3 with Z1 ASAT character, but none were T. cruzi Z2. Z1 was predominantly isolated from arboreal mammals, especially Didelphis marsupialis; Z3 was mainly found in terrestrial or burrowing mammals, particularly Dasypus novemcinctus and Monodelphis brevicaudata. It is not clear whether gene exchange occurs between the groups designated as zymodemes but the enzymic distance between T. cruzi Z1, Z2 and Z3, their different geographical distributions, host associations and local transmission cycles support the view that these zymodemes represent taxonomic units of fundamental epidemiological significance. T. cruzi (Z1) was isolated for the first time from the silky anteater (Cyclopes didactylus).

Experimental cutaneous leishmaniasis: IV. The humoral response of Cebus apella (Primates: Cebidae) to infections of Leishmania (Leishmania) amazonensis, L. (Viannia) lainsoni and L. (V.) braziliensis using the direct agglutination test

The direct agglutination test (DAT) was used to evaluate the serological response of 150 serum samples taken from 15 captive-bred capuchin monkeys Cebus apella. These animals had been experimentally infected with either L. (Leishmania) amazonensis, L. (Viannia) lainsoni or L. (V.) braziliensis. Monkeys infected with L. (L.) amazonensis or L. (V.) lainsoni were challenged with the homologous parasite one month after their spontaneous cure. DAT antigens were prepared from L. (L.) donovani, L. (L.) amazonensis and L. (V.) braziliensis. Antigens were difficult to standardise and it was impossible to produce an L. (V.) lainsoni antigen as parasites remained aggregated even after trypsinization. The DAT detected significant humoral responses in all the infected monkeys. Titres were higher when homologous antigens were used, especially in secondary responses. This suggests that homologous antigen should be used to detect antibodies in human cutaneous leishmaniasis.

Leishmaniasis in Brazil. XXI. visceral leishmaniasis in the Amazon Region and further observations on the role of Lutzomyia longipalpis (Lutz & Neiva, 1912) as the vector

Further evidence is presented incriminating the sandfly Lutzomyia longipalpis as the vector of Leishmania chagasi, the causative agent of American visceral leishmaniasis, in the Amazon Region of Brazil. During an outbreak of the disease in Santarém, Pará State, this insect was shown to be the only species of sandfly consistently present in and around the patients homes, where it often occurred in very large numbers. Of 491 specimens dissected, 35 (7.14%) proved to be infected, and isolates of L. chagasi were made from 16 of 27 of these sandflies following the inoculation of the promastigotes into hamsters. Finally, the parasite was transmitted to four other hamsters which had been subjected to the bites of large numbers of wild-caught Lu. longipalpis. Isolates of Leishmania from Lu. longipalpis captures in Santarém, and in another focus of visceral leishmaniasis on the Island of Marajó, Pará, have been shown to be biologically and biochemically indistinguishable from the parasite infecting man, dogs and foxes in Pará, and from stocks obtained from man elsewhere in Brazil (Bahia and Ceará States).

Leishmaniasis in Brazil: XX. Prevalence of “enzootic rodent leishmaniasis” (Leishmania mexicana amazonensis), and apparent absence of “pian bois” (Le. braziliensis guyanensis), in plantations of introduced tree species and in other non-climax forests in eastern Amazônia

In Amazonian Brazil most human leishmaniasis is due to Leishmania braziliensis s.l. and is acquired during the clearing of primary climax forest. One of the largest deforestation projects has taken place on the JARI property where plantations of exotic tree species are grown for paper pulp. The ability of the regional leishmaniasis enzootics to invade plantations was investigated. CDC light-trap catches indicated the phletobomine vectors of Le. b. guyanensis (causing pian bois in man) to be very scarce in JARI plantations compared to native-forest controls. It is concluded (drawing on other observations) that the vectors of pian bois are unlikely to thrive in any secondary forest. In contrast, catches from mammal traps and rodent-baited (Disney) traps demonstrated the presence in JARI plantations of infected Proechimys guyannensis and large populations of Lutzomyia flaviscutellata, respectively the major rodent reservoir and sandfly vector of Le. mexicana amazonensis. Alone amongst the local vectors of human cutaneous leishmaniasis, Lu. flaviscutellata is adapted to non-climax forests (primary or secondary, natural or man-made; synopsis given). It is predicted that the public health importance of Le. m. amazonensis is unlikely to diminish following the development of Amazônia. This is worrying because ca. 30% of Le. m. amazonensis infections in man cause highly-disfiguring, incurable diffuse cutaneous leishmaniasis.

Leishmaniasis in Brazil. XXIV. Natural flagellate infections of sandflies (Diptera: Psychodidae) in Pará State, with particular reference to the rôle of Psychodopygus wellcomei as the vector of Leishmania braziliensis braziliensis in the Serra dos Carajás

Between July 1983 and December 1984 natural flagellate infections were found in 114 (1%) of 11,586 female phlebotomine sandflies (Diptera: Psychodidae) of 21 species. A further 1084 females of 17 other species were not infected. Identification of the organisms on a number of occasions confirms the exclusive parasite/vector relationship of Leishmania mexicana amazonensis/Lutzomyia flaviscutellata and Le. braziliensis braziliensis/Psychodopygus wellcomei. Undescribed or unidentified Leishmania spp. were isolated from Lu. shawi, Lu. ubiquitalis, Lu. whitmani, Ps. hirsutus, Ps. paraensis Ps. wellcomei, and trypanosomes from Lu. nordestina and Lu. trinidadensis. Flagellate infections were recorded in 8 of 21 species examined for the first time, and some were isolated directly from insects into cultures. Le. b. braziliensis was transmitted to a hamster by the bite of a wild-caught, naturally infected Ps. wellcomei. 7 of the 35 infected Ps. wellcomei were allowed to oviposit and the eggs were reared to adults. Four produced Ps. wellcomei males only, confirming the rôle of this species as the major vector of Le. b. braziliensis.

Leishmaniasis in Brazil: XV. Biochemical distinction of Leishmania mexicana amazonensis, L. braziliensis braziliensis and L. braziliensis guyanensis—aetiological agents of cutaneous leishmaniasis in the Amazon Basin of Brazil

Enzymic profiles of the three known agents of human cutaneous leishmaniasis in the lower Amazon region are compared. Of 14 enzymes, 10 (ASAT, ALAT, GPI, G5PD, MDH, ACON, PEP, HK, MPI and ACP) differentiate Leishmania mexicana amazonensis from L. braziliensis braziliensis or L. braziliensis guyanensis: this supports their taxonomic status as distinct species. In contrast, only slight mobility differences of four enzymes (ASAT, ALAT, PGM, MPI) separate L. b. braziliensis and L. b. guyanensis, which are distinguished biochemically for the first time: this indicates that they are closely related. Four stocks of L. b. panamensis correspond with L. b. guyanensis on mobilities of 10 enzymes (ASAT, ALAT, PGM, GPI, G6PD, MDH, PK, HK, MPI, ACP), although these two subspecies are known to be separable by kinetoplast DNA buoyancies and the enzyme 6PGDH. The generation of practical, regional biochemical keys to the medically important leishmanias is discussed.

Cutaneous leishmaniasis due to Leishmania (Leishmania) amazonensis in Amazonian Brazil, and the significance of a negative Montenegro skin-test in human infections

The clinical and epidemiological features of 62 cases of cutaneous leishmaniasis due to Leishmania (Leishmania) amazonensis, from Pará State, Amazonian Brazil, are discussed. The parasite, isolated in hamster skin and/or blood-agar culture medium, was in each case identified by both biological characteristics and a monoclonal antibody specific for promastigotes of L. (L.) amazonensis. Of the 62 patients, 46 (74.2%) presented with a single cutaneous lesion, and on no occasion was evidence found indicating metastatic spread to either the naso-pharyngeal mucosae or the viscera. Recent claims that this parasite may be responsible for both mucocutaneous leishmaniasis and typical visceral leishmaniasis are discussed. Meglumine antimoniate (Glucantime) proved highly efficient in the treatment of all patients. Of the 62 patients examined by the Montenegro skin test, only 32 (51.6%) gave a positive reaction. The significance of this finding is considered and the hypothesis made that the parasite itself may induce an immunoinhibition. Field studies amply confirmed the role of Lutzomyia flaviscutellata as the major sandfly vector of L. (L.) amazonensis in Amazonia.