Iloneoside, an antimalarial pregnane glycoside isolated from Gongronema latifolium leaf, potentiates the activity of chloroquine against multidrug resistant Plasmodium falciparum.

The rapid spread of drug resistant malaria parasites has necessitated the search for novel antimalarials and chemosensitizers capable of reversing drug resistance in the parasites. A number of studies have revealed the resistance reversal activities of pregnane glycosides and the antimalarial activity of a pregnane glycoside obtained from Gongronema species. However, the pregnane (2) and pregnane glycosides (1, 3-4) isolated from Gongronema latifolium leaf have not been evaluated for these activities. This study was therefore carried out to evaluate the antiplasmodial and chloroquine resistance reversal activities of a pregnane and three pregnane glycosides isolated from G. latifolium leaf in vitro. The compounds were evaluated for their inhibitory activities against P. falciparum 3D7 (a chloroquine-sensitive strain) and P. falciparum W2 (a chloroquine-resistant clone) in vitro. The activities of chloroquine in separate combination with each of the compounds against P. falciparum W2 were also evaluated. Moreover, the interaction of the active compounds (1 and 4) with selected P. falciparum proteins (PfProteins) were evaluated in silico. The results revealed that only 1 and 4 were active against P. falciparum 3D7 and P. falciparum W2. Also, 2 and 3 did not exhibit chloroquine resistance reversal activity. Activity of chloroquine against P. falciparum W2 was potentiated by 1 by 3200% at concentrations higher than 0.625 µg/mL. Also, 1 and 4 demonstrated similar binding patterns and higher binding tendencies to the selected PfProteins compared to chloroquine. Thus, 1 (iloneoside) is an antimalarial pregnane glycoside which can potentiate the activity of chloroquine against multidrug resistant P. falciparum.

Antimalarial Activity of Cocos nucifera Husk Fibre: Further Studies.

In this study, the antimalarial and toxicity potentials of husk fibre extracts of five Nigerian varieties of Cocos nucifera were evaluated in vitro. The only active extract fraction, West African Tall (WAT) ethyl acetate extract fraction, was then evaluated for its phytochemical constituents, antimalarial and toxicity potentials at varying doses (31.25-500 mg/kg body weight) using various organ function indices. The results revealed that WAT ethyl acetate extract fraction (WATEAEF) contained alkaloids, tannins, and flavonoids and was active against Plasmodium falciparum W2 strain maintained in continuous culture, with a selectivity index of 30.3. The same extract fraction was active in vivo against Plasmodium berghei NK65, causing more than 50% reduction in parasitaemia on days 4 and 6 after inoculation at various doses administered. WATEAEF did not significantly alter (P > 0.05) function indices of the liver and cardiovascular system at all doses administered but significantly increased (P < 0.05) plasma creatinine concentration at 250 and 500 mg/Kg body weight compared to controls. The results of this study suggest that WATEAEF possesses antimalarial activity and may not adversely affect normal liver function nor predispose subjects to cardiovascular diseases but may impair normal kidney function at higher doses. Further studies are underway to isolate the active principles.

Evaluation of the antiplasmodial and cytotoxicity potentials of husk fiber extracts from Cocos nucifera, a medicinal plant used in Nigeria to treat human malaria.

Nigeria is an African country where transmission of malaria occurs all year round and where most inhabitants use plants as remedies against parasitic diseases, including malaria. Some of such medicinal plants have their antimalarial efficacies already demonstrated experimentally, active compounds isolated and the mechanism of drug action suggested. Decoction of Cocos nucifera husk is used in the middle belt region of Nigeria as an antimalarial remedy. In our current studies, we tested extracts from husks of four varieties of C. nucifera, all collected in Brazil, where the plant fruit is popularly named 'coco'. The husks of coco mestiço, amarelo, anão and gigante collected in the Northeast of Brazil were used to prepare extracts at the Chemistry Department, Federal University of Alagoas (UFAL), which were then tested for their antiplasmodial activities, cytotoxicities and hemolytic activities in vitro. Only the hexane extract of coco mestiço was active against the blood forms of Plasmodium falciparum human malaria parasite maintained in continuous culture. Most extracts presented selectivity indices of <10, while hexane extract of coco mestiço had a selectivity index of 35, meaning that the extract is not toxic. The isolation of the active compounds from coco mestiço husks has not yet been done.

Potential antimalarials from Nigerian plants: a review.

Malaria, caused by parasites of the genus Plasmodium, is one of the leading infectious diseases in many tropical regions, including Nigeria, a West African country where transmission occurs all year round. Many of the inhabitants use plants as remedies against fever and other symptoms of acute malaria, as reported herein. Some of these plants have their antimalarial efficacies scientifically demonstrated and the active compounds isolated with their probable mechanisms of action studied. Medicinal plants are used to treat diseases also where the biodiversity of plants occur in parallel with endemic transmission of malaria. This review focuses on medicinal plants which are used to treat malaria in Nigeria, and on antimalarial testing of extracts and purified compounds from plants. Some show intense activity against malaria parasites in vitro and in experimentally infected mice. The search for new drugs based on plants is important due to the emergence and widespread of chloroquine-resistant and multiple drug-resistant malaria parasites, which require the development of new antimalarials. An acquaintance with antimalarial plants may be a springboard for new phytotherapies that could be affordable to treat malaria, especially among the less privileged native people living in endemic areas of the tropics, mostly at risk of this devastating disease.

Ampelozyziphus amazonicus Ducke (Rhamnaceae), a medicinal plant used to prevent malaria in the Amazon Region, hampers the development of Plasmodium berghei sporozoites.

Most medicinal plants used against malaria in endemic areas aim to treat the acute symptoms of the disease such as high temperature fevers with periodicity and chills. In some endemic areas of the Brazilian Amazon region one medicinal plant seems to be an exception: Ampelozyziphus amazonicus, locally named "Indian beer" or "Saracura-mira", used to prevent the disease when taken daily as a cold suspension of powdered dried roots. In previous work we found no activity of the plant extracts against malaria blood parasites in experimentally infected animals (mice and chickens) or in cultures of Plasmodium falciparum. However, in infections induced by sporozoites, chickens treated with plant extracts were partially protected against Plasmodium gallinaceum and showed reduced numbers of exoerythrocytic forms in the brain. We now present stronger evidence that the ethanolic extract of "Indian beer" roots hampers in vitro and in vivo development of Plasmodium berghei sporozoites, a rodent malaria parasite. Some mice treated with high doses of the plant extract did not become infected after sporozoite inoculation, whereas others had a delayed prepatent period and lower parasitemia. Our data validates the use of "Indian beer" as a remedy for malaria prophylaxis in the Amazon, where the plant exists and the disease represents an important problem which is difficult to control. Studies aiming to identify the active compounds responsible for the herein described causal prophylactic activity are needed and may lead to a new antimalarial prophylactic.

Inhibitory properties of the antibody response to Plasmodium vivax Duffy binding protein in an area with unstable malaria transmission.

The function of the Plasmodium vivax Duffy binding protein (DBP) during the erythrocyte invasion process is critical for successful parasite growth and pathogenesis in human infections. Although DBP is the subject of intensive malaria vaccine research, investigations on the functional proprieties of anti-DBP antibodies in the human population have been limited [Infect Immun68 (2000) 3164]. In the present study, we examined the ability of sera from different populations of the Brazilian Amazon--an area of markedly unstable malaria transmission--to inhibit the erythrocyte-binding function of the DBP ligand domain (region II, DBP(II)). We found that long-term exposure to malaria in the Amazon area elicits DBP-specific antibodies that inhibit the binding of different DBP(II) variants to erythrocytes. Despite the great variability of inhibitory antibody responses observed among study participants, we observed a positive correlation between erythrocyte binding-inhibitory activity and enzyme-linked immunosorbent assay anti-DBP antibodies. Of importance, there was a non-significant tendency towards increased levels of anti-DBP antibodies among individuals with asymptomatic P. vivax infections.

New evidences of antimalarial activity of Bidens pilosa roots extract correlated with polyacetylene and flavonoids.

Bidens pilosa is among the several plants used in Brazil to treat malaria. It was demonstrated that crude extracts from roots prepared with 80% ethanol by percolation are active in vitro against Plasmodium falciparum and the activity is correlated with the presence of polyacetylene and flavonoids. This extract was submitted to column chromatography with ether and ether methanol (1:1) and two fractions, enriched in polyacetylene and flavonoids, respectively, were obtained. The extract and the fractions were assessed by HPLC/DAD analysis and antimalarial tests in vivo. Ethanol extract showed by HPLC the presence of several peaks for polyacetylene and flavonoids, compounds corresponding to quercetin-3,3'-dimethoxy-7-0-rhamnoglucopyranose and the acetylene 1-phenyl-1,3-diyn-5-en-7-ol-acetate, previously identified in this extract. The peaks for flavonoids were absent in ether fraction and those ones for polyacetylene in ether:methanol. In in vivo tests, ethanol extract caused 36% of reduction of parasitaemia at fifth day, and 29% at seventh day. Ether:methanol fraction caused 38% of reduction at fifth day but was inactive at day 7. The survival of the animals treated with 80% ethanol extract was higher than in the fractions. The results showed that the in vivo activity of ethanol extract depends on the presence of polyacetylene and flavonoids.

Antimalarial activity of Cinchona-like plants used to treat fever and malaria in Brazil.

For centuries, malaria was treated with the bark of Cinchona calisaya and Cinchona succirubra plants named "quinas" in Brazil, from which the quinine molecule was isolated. Other plant species known also as "quinas" are used to treat fever and malaria, like Deianira erubescens (roots and leaves), Strychnos pseudoquina (bark), and Remijia ferruginea (bark). Based on this popular knowledge, we evaluated the in vivo antimalarial activity of the ethanol crude extracts of these plant species in mice infected with Plasmodium berghei. Only Remijia ferruginea showed antimalarial activity, reducing parasitaemia and mortality at the highest dose tested. Its phytochemical analysis showed the presence of alkaloids but not quinine. The other two plant species were inactive.

[Cutaneous leishmaniasis in the Metropolitan Region of Belo Horizonte: clinical, laboratorial, therapeutic and prognosis features (1989-1995)]. / Leishmaniose tegumentar na Região Metropolitana de Belo Horizonte: aspectos clínicos, laboratoriais, terapêuticos e evolutivos (1989-1995).

This study investigated clinical, laboratorial, therapeutic and prognostic aspects of American cutaneous leishmaniasis in Belo Horizonte in 358 patients with cutaneous leishmaniasis (CL) and 25 with mucocutaneous leishmaniasis (MCL). Compared to CL patients, the MCL patients reported longer duration of disease and higher frequency of other diseases, suggesting that debilitation caused by leishmaniasis or other conditions might contribute to activation and/or mucous dissemination of the parasite. The sensitivity of skin test, indirect immunofluorescence reactions and direct detection of parasites was 78.4, 79.3 and 68.3%, respectively. The treatment with meglumine antimoniate presented 100% efficacy, but 59% patients had side-effects. During two years of follow-up, there were 32/318 relapses after successful treatment. Most relapses (31/32) were of CL patients treated with 15 mg Sb5+/kg/day. The negative response to skin test was the only factor associated with a significant threefold increased risk of relapse. Higher dose or longer duration of treatment might improve the prognosis in these patients.

Malaria: a sporozoite runs through it.

A recent study reveals new insights into the development of Plasmodium sporozoites, the infectious agents of malaria. These findings may lead to changes in the approach to malaria vaccines and novel interpretations of the mechanisms of immunity to malaria.

Leishmaniose tegumentar na Região Metropolitana de Belo Horizonte: aspectos clínicos, laboratoriais, terapêuticos e evolutivos (1989-1995) / Cutaneous leishmaniasis in the Metropolitan Region of Belo Horizonte: clinical, laboratorial, therapeutic and prognosis features (1989-1995)

This study investigated clinical, laboratorial, therapeutic and prognostic aspects of American cutaneous leishmaniasis in Belo Horizonte in 358 patients with cutaneous leishmaniasis (CL) and 25 with mucocutaneous leishmaniasis (MCL). Compared to CL patients, the MCL patients reported longer duration of disease and higher frequency of other diseases, suggesting that debilitation caused by leishmaniasis or other conditions might contribute to activation and/or mucous dissemination of the parasite. The sensitivity of skin test, indirect immunofluorescence reactions and direct detection of parasites was 78.4, 79.3 and 68.3%, respectively. The treatment with meglumine antimoniate presented 100% efficacy, but 59% patients had side-effects. During two years of follow-up, there were 32/318 relapses after successful treatment. Most relapses (31/32) were of CL patients treated with 15 mg Sb5+/kg/day. The negative response to skin test was the only factor associated with a significant threefold increased risk of relapse. Higher dose or longer duration of treatment might improve the prognosis in these patients.

Foram investigados aspectos clínicos, laboratoriais, terapêuticos e evolutivos da leishmaniose tegumentar americana em Belo Horizonte. O estudo incluiu 358 pacientes com leishmaniose cutânea (LC) e 25 com leishmaniose mucosa (LM). Comparados aos pacientes com LC, aqueles com LM apresentaram maior tempo de doença e relato de outras doenças concomitantes, sugerindo que a debilitação pela leishmaniose e/ou outras doenças podem contribuir para a ativação e/ou disseminação mucosa do parasito. As sensibilidades das reações intradérmica, de imunofluorescência indireta e da pesquisa direta do parasito foram de 78,4, 79,3 e 68,3%, respectivamente. O tratamento com antimoniato de meglumina foi 100% eficaz, com 59% de efeitos colaterais ao longo do tratamento. A recidiva após tratamento ocorreu em 32 (10,1%) dos 318 casos seguidos por até dois anos. A maioria das recidivas (31 dos 32 casos) ocorreu em pacientes com LC tratados com 15mg Sb5+/kg/dia. Na investigação de critérios de cura, a reação intradérmica negativa foi o único fator associado a um risco três vezes maior de recidiva. Um aumento da dose ou do tempo de tratamento talvez melhore o prognóstico nestes pacientes.

The search for new antimalarial drugs from plants used to treat fever and malaria or plants ramdomly selected: a review.

In this review we discuss the ongoing situation of human malaria in the Brazilian Amazon, where it is endemic causing over 610,000 new acute cases yearly, a number which is on the increase. This is partly a result of drug resistant parasites and new antimalarial drugs are urgently needed. The approaches we have used in the search of new drugs during decades are now reviewed and include ethnopharmocology, plants randomly selected, extracts or isolated substances from plants shown to be active against the blood stage parasites in our previous studies. Emphasis is given on the medicinal plant Bidens pilosa, proven to be active against the parasite blood stages in tests using freshly prepared plant extracts. The anti-sporozoite activity of one plant used in the Brazilian endemic area to prevent malaria is also described, the so called "Indian beer" (Ampelozizyphus amazonicus, Rhamnaceae). Freshly prepared extracts from the roots of this plant were totally inactive against blood stage parasites, but active against sporozoites of Plasmodium gallinaceum or the primary exoerythrocytic stages reducing tissue parasitism in inoculated chickens. This result will be of practical importance if confirmed in mammalian malaria. Problems and perspectives in the search for antimalarial drugs are discussed as well as the toxicological and clinical trials to validate some of the active plants for public health use in Brazil.

American cutaneous leishmaniasis: use of a skin test as a predictor of relapse after treatment.

While relapses following clinical cure of American cutaneous leishmaniasis are frequent, no test has been described until now to predict such relapses. A cohort of 318 American cutaneous leishmaniasis patients was followed up for two years after treatment with meglumine antimoniate, during which time 32 relapses occurred, 30 in the first year and two in the second (accumulated risk: 10.5%). No association was found between these relapses and the parasite-specific antibody response before and after treatment, or between the relapses and stratification by sociodemographic and clinical characteristics. However when Leishmania was used as antigen, patients with a negative skin test at the time of diagnosis presented a 3.4-fold higher risk (hazard risk = 3.4; 95% confidence interval, 1.7-7.0) of American cutaneous leishmaniasis relapse, compared with patients with a positive response. This result shows that the skin test can be a predictor of American cutaneous leishmaniasis relapse after treatment.

The targets of the lytic antibody response against Trypanosoma cruzi.

Trypanosoma cruzi trypomastigotes, but not epimastigotes, are normally resistant to the lytic effects of complement from vertebrate hosts susceptible to infection. This resistance facilitates parasite survival and infectivity. During the course of chronic infections, however, the vertebrate hosts produce antibodies that render the trypomastigotes sensitive to lysis, primarily via the alternative complement cascade and amplified by the classical pathway. Here, Greice Krautz, Jessica Kissinger and Antoniana Krettli summarize research on lytic antibodies, and on their respective target(s) on the T. cruzi surface. These targets are useful in tests aimed at the diagnosis of chronic Chagas disease for control of cure after specific treatment and for vaccine development.

Virus-expressed, recombinant single-chain antibody blocks sporozoite infection of salivary glands in Plasmodium gallinaceum-infected Aedes aegypti.

Transgenic mosquitoes resistant to malaria parasites are being developed to test the hypothesis that they may be used to control disease transmission. We have developed an effector portion of an antiparasite gene that can be used to test malaria resistance in transgenic mosquitoes. Mouse monoclonal antibodies that recognize the circumsporozoite protein of Plasmodium gallinaceum can block sporozoite invasion of Aedes aegypti salivary glands. An anti-circumsporozoite monoclonal antibody, N2H6D5, whose corresponding heavy- and light-chain gene variable regions were engineered as a single-chain antibody construct, binds to P. gallinaceum sporozoites and prevents infection of Ae. aegypti salivary glands when expressed from a Sindbis virus. Mean intensities of sporozoite infections of salivary glands in mosquitoes expressing N2scFv were reduced as much as 99.9% when compared to controls.

Multiepitope synthetic peptide and recombinant protein for the detection of antibodies to Trypanosoma cruzi in patients with treated or untreated Chagas' disease.

A tetrapeptide and a recombinant protein, each representing 4 immunodominant epitopes of Trypanosoma cruzi, were tested by use of ELISA for the detection of serum antibodies. Sera from individuals with Chagas' disease, including persons untreated and successfully or unsuccessfully treated, were tested. These assays detected antibody in 100% of the parasitemias. The antibody reactivity decreased based on the success of treatment. Higher sensitivity was observed for tetrapeptide/recombinant protein assays than for lysate-based ELISA, and specificity was improved, particularly with Leishmania sera. The results indicate that multiepitope antigens provide a more sensitive and specific alternative to lysate for detection of anti-T. cruzi antibodies, as required for developing blood screening assays.