An in silico 3D pharmacophore model of chalcones useful in the design of novel antimalarial agents.

Malaria, the most important of the human parasitic diseases, causes about 500 million infections worldwide and over 1 million deaths every year. The search for novel drug candidates against specific parasitic targets is an important goal for antimalarial drug discovery. Recently the antimalarial activity of chalcones has generated great interest. These compounds are small non-chiral molecules with relative high lipophilicity (clogP approximately 5-7), have molecular weights in the range of 300 to 600 g/mol, and possess in vivo efficacy against both P. berghei and P. yeolii. Preliminary data on our on-going chalcone synthesis project indicate that these compounds are active in vitro against P. falciparum, but are rapidly metabolized in liver microsome assays. Structurally-related compounds not including the enone linker are found to be much more metabolically stable and yet have comparable in vitro efficacy. In this study, we have utilized the efficacy data from an in-house on-going chalcone project to develop a 3D pharmacophore for antimalarial activity and used it to conduct virtual screening (in silico search) of a chemical library which resulted in identification of several potent chalcone-like antimalarials. The pharmacophore is found to contain an aromatic and an aliphatic hydrophobic site, one hydrogen bond donor site, and a ring aromatic feature distributed over a 3D space. The identified compounds were not only found to be potent in vitro against several drug resistant and susceptible strains of P. falciparum and have better metabolic stability, but included one with good in vivo efficacy in a mouse model of malaria.

Utility of alkylaminoquinolinyl methanols as new antimalarial drugs.

Mefloquine has been one of the more valuable antimalarial drugs but has never reached its full clinical potential due to concerns about its neurologic side effects, its greater expense than that of other antimalarials, and the emergence of resistance. The commercial development of mefloquine superseded that of another quinolinyl methanol, WR030090, which was used as an experimental antimalarial drug by the U.S. Army in the 1970s. We evaluated a series of related 2-phenyl-substituted alkylaminoquinolinyl methanols (AAQMs) for their potential as mefloquine replacement drugs based on a series of appropriate in vitro and in vivo efficacy and toxicology screens and the theoretical cost of goods. Generally, the AAQMs were less neurotoxic and exhibited greater antimalarial potency, and they are potentially cheaper than mefloquine, but they showed poorer metabolic stability and pharmacokinetics and the potential for phototoxicity. These differences in physiochemical and biological properties are attributable to the "opening" of the piperidine ring of the 4-position side chain. Modification of the most promising compound, WR069878, by substitution of an appropriate N functionality at the 4 position, optimization of quinoline ring substituents at the 6 and 7 positions, and deconjugation of quinoline and phenyl ring systems is anticipated to yield a valuable new antimalarial drug.

Natural infections of Leishmania peruviana in animals in the Peruvian Andes.

Evidence that domestic dogs may act as reservoir hosts for cutaneous leishmaniasis in the Peruvian Andes is provided by the isolation, for the first time, from naturally infected dogs of parasites identified (by isoenzymes) as Leishmania peruviana. Leishmania parasites were isolated from nasal aspirates or biopsies from 5 (1.8%) of 279 asymptomatic dogs samples in endemic villages of the Peruvian Andes. In addition, Leishmania (Viannia) infections were identified in 15 (5.4%) of 276 nasal samples by the polymerase chain reaction (PCR) using subgenus-specific primers. Further circumstantial evidence for a reservoir role for dogs comes from the finding of a relatively high dog blood index among the sandfly vectors collected inside houses (29% for Lutzomyia peruensis and 17% for Lu. verrucarum). Possible wild mammal reservoir hosts for Andean cutaneous leishmaniasis were also detected in endemic villages. At least 8 species were identified among the 1266 small mammals trapped. Leishmania parasites were isolated from blood or skin biopsies taken from 2 (2.6%) of 78 Didelphis albiventris and 6 (1.2%) of 511 Phyllotis andinum. Three isolates were identified by isoenzymes as L. peruviana, and the other 5 were identified by PCR as Leishmania (Viannia) species. Leishmania (Viannia) infections were also identified by PCR directly on skin biopsies taken from 2 (2.8%) of 72 D. albiventris, 1 (0.2%) of 499 P. andinum, and 4 (2.6%) of 153 Akodon sp.

Short report: detection of Leishmaniavirus in human biopsy samples of leishmaniasis from Peru.

Leishmaniavirus is a double-stranded RNA virus that persistently infects some strains of the protozoan parasite Leishmania. There is considerable interest in the possibility that the presence of this virus alters parasite phenotype and may affect disease pathogenesis. If so, the virus marker could provide a valuable prognostic indicator for human leishmaniasis, particularly in those cases caused by New World parasite strains. The virus has been detected in cultured L. braziliensis, L. b. guyanensis, and L. major. To date there has been no information as to the extent of infection in samples prior to culturing in the laboratory. This study demonstrates, through the reverse transcription-polymerase chain reaction, that Leishmaniavirus exists in human biopsy samples of leishmaniasis prior to manipulation in culture.

Cutaneous leishmaniasis in the Peruvian Andes: factors associated with variability in clinical symptoms, response to treatment, and parasite isolation rate.

The severity of cutaneous leishmaniasis may be determined by host immunity, parasite virulence, and host or vector behavior. We performed a multivariate analysis to identify the main causes of the variability in clinical symptoms, response to treatment, and parasite isolation rate among Peruvian patients. The effect of host immunity was demonstrated first by the finding that secondary infections induced smaller lesions associated with a lower parasite isolation rate than did primary infections and, second, by the finding of fewer lesions in older patients. Phenotypic differences between parasite populations were suggested by the observation that the mean scar size and number varied between villages: patients had more scars in villages where the transmission rates were higher. Human behavior probably determined the site of lesions on the body, since most lesions in the cooler South were on the head, whereas in the North, lesions were equally frequent on the extremities. In addition, older patients, who were more likely infected through occupational exposure, had fewer head lesions. Geographic variation in the pattern of exposure to sandflies indicates that uta control strategies should be region specific.

Lutzomyia verrucarum can transmit Leishmania peruviana, the aetiological agent of Andean cutaneous leishmaniasis.

In much of the endemic area for cutaneous leishmaniasis (uta) in the Peruvian Andes, the only 2 anthropophilic sandfly species present are Lutzomyia peruensis and Lu. verrucarum. On the basis of a single confirmed isolation of Leishmania peruviana (the aetiological agent of uta) from a wild Lu. peruensis, and apparent associations between sandfly abundance and the incidence of uta, it is generally believed that Lu. peruensis is the most important vector. In this paper, a potential role for Lu. verrucarum in the transmission of uta is indicated by laboratory experiments which show that this species is vectorially competent for L. peruviana. Individual or pooled colonized sandflies were permitted to take a second blood meal on 22 susceptible golden hamsters at varying intervals after feeding on hamsters previously infected with L. peruviana. Transmission was achieved by a single infected sandfly (of a total of 59) following a 15 d incubation period. Transmission was recognized by the characteristic clinical response (footpad swelling) associated with hamsters which have been inoculated with L. peruviana, and by the presence of parasites in aspirates made from the swollen footpad, detected by the polymerase chain reaction (PCR) and by parasite isolations in biphasic blood-agar culture medium. The identity of the parasite isolates was also confirmed by PCR (specific for parasites in the L. braziliensis complex). This is the first reported experimental transmission of L. peruviana by any sandfly species.