Implications of Glutathione Levels in the Plasmodium berghei Response to Chloroquine and Artemisinin.

Malaria is one of the most devastating parasitic diseases worldwide. Plasmodium drug resistance remains a major challenge to malaria control and has led to the re-emergence of the disease. Chloroquine (CQ) and artemisinin (ART) are thought to exert their anti-malarial activity inducing cytotoxicity in the parasite by blocking heme degradation (for CQ) and increasing oxidative stress. Besides the contribution of the CQ resistance transporter (PfCRT) and the multidrug resistant gene (pfmdr), CQ resistance has also been associated with increased parasite glutathione (GSH) levels. ART resistance was recently shown to be associated with mutations in the K13-propeller protein. To analyze the role of GSH levels in CQ and ART resistance, we generated transgenic Plasmodium berghei parasites either deficient in or overexpressing the gamma-glutamylcysteine synthetase gene (pbggcs) encoding the rate-limiting enzyme in GSH biosynthesis. These lines produce either lower (pbggcs-ko) or higher (pbggcs-oe) levels of GSH than wild type parasites. In addition, GSH levels were determined in P. berghei parasites resistant to CQ and mefloquine (MQ). Increased GSH levels were detected in both, CQ and MQ resistant parasites, when compared to the parental sensitive clone. Sensitivity to CQ and ART remained unaltered in both pgggcs-ko and pbggcs-oe parasites when tested in a 4 days drug suppressive assay. However, recrudescence assays after the parasites have been exposed to a sub-lethal dose of ART showed that parasites with low levels of GSH are more sensitive to ART treatment. These results suggest that GSH levels influence Plasmodium berghei response to ART treatment.

Abnormal Trichuris trichiura eggs detected during an epidemiological survey.

Abnormal eggs of Trichuris trichiura were found in the stools of one of the patients during a study on the prevalence of intestinal parasitoses among an institutionalized population. The abnormalities observed included great variation in shape, size, and color. Similar atypical whipworm eggs have been reported in patients after treatment with mebendazole, thiabendazole, tetracloroethylene, and dithiazanine. Apparently some anthelminthics have an effect on the reproductive system of female T. trichiura, resulting in production of abnormal eggs, which could lead to misdiagnosis of the infection, since they can be mistaken as eggs of other parasites or artifacts.

Plasmodium yoelii: identification and partial characterization of an MDR1 gene in an artemisinin-resistant line.

The molecular mechanisms by which the malarial parasite has managed to develop resistance to many antimalarial drugs remain to be completely elucidated. Mutations in the pfmdr1 gene of Plasmodium falciparum, as well as an increase in pfmdr1 copy number, have been associated with resistance to the quinoline-containing antimalarial drugs. We investigated the mechanisms of drug resistance in Plasmodium using a collection of P. yoelii lines with different drug resistance profiles. The mdr1 gene of P. yoelii (pymdr1) was identified and characterized. A 2- to 3-fold increase in the pymdr1 gene copy number was observed in the P. yoelii ART line (artemisinin resistant) when compared with the NS parental line. The pymdr1 gene was mapped to a chromosome of 2.1 Mb in all lines analyzed. Reverse transcriptase-polymerase chain reaction and Western blot experiments confirmed the expression of the gene at the RNA and protein levels.

Plasmodium berghei: analysis of the gamma-glutamylcysteine synthetase gene in drug-resistant lines.

The rapid emergence of multidrug-resistant Plasmodium falciparum is a worldwide concern. Despite the magnitude of the problem, the mechanisms involved in this phenomenon are not well understood. One current proposal suggests that toxic heme molecules are degraded by glutathione (GSH), and that anti-malarial drugs, such as chloroquine (CQ), inhibit this degradation, thus implicating GSH in drug resistance. Furthermore, in some strains of Plasmodium berghei and P. falciparum, chloroquine resistance is accompanied by an increase in glutathione levels and increased activity in GSH-related enzymes. We are investigating the relationship between the gamma-glutamylcysteine synthetase (ggcs) gene, the rate-limiting enzyme in de novo synthesis of GSH, and drug resistance in P. berghei at the molecular level. In this report, we have demonstrated an increase in pbggcs mRNA levels associated with CQ and mefloquine (MFQ) resistance. In addition, the pbggcs gene locus structure was shown to be similar and localized to chromosome 8 in four parasite lines of P. berghei with different drug resistance profiles. This work suggests a link between increased GSH levels and drug resistance in Plasmodium.

Diagnosis of Malaria by polymerase chain reaction

Malaria is no longer endemic in Puerto Rico, however, imported cases of the disease are occasionally reported to the Health Department of the Island. This is a report of a 45-year-old female patient who traveled to Kenya and Niger and was admitted to a San Juan area hospital with an 8 day history of daily chills and fever, myalgia, nausea and vomiting. Upon admission, peripheral blood displayed multiple intra-erythrocytic ring-shape trophozoites, highly suggestive of Plasmodium falciparum. The polymerase chain reaction was used as a complementary method for the detection of malaria parasites and confirmation of post-treatment parasite clearance. This report presents an imported case of malaria in Puerto Rico and showed the use of a molecular technique to diagnose Plasmodium