Rediscovery and redefinition of Malcolm Smith's Trimeresurus kanburiensis in Thailand, with a report of envenoming.

Three specimens of an apparently rare pit viper, Trimeresurus kanburiensis, previously known only from the holotype collected in 1928, were found near Kanchanaburi in western Thailand. One of the snakes had bitten a young woman on the foot. She experienced severe local pain, swelling that involved the whole of the bitten limb and beyond, local bruising, recurrent shock, peripheral leucocytosis and a mild coagulopathy, but she recovered despite the lack of specific treatment. The severity of envenoming augurs ill for a young or debilitated patient bitten by this species. During the last 20 years, the name T. kanburiensis has been used incorrectly for the medically more important species, T. purpureomaculatus. Conversely, the name T. purpureomaculatus has been misapplied to specimens of a species of viper from southern Thailand which we consider very similar to T. kanburiensis, but for which a new specific name, 'T. venustus', has been suggested recently. The rediscovery and redefinition of T. kanburiensis should prevent further confusion.     

Levels of stem cell factor and interleukin-3 in serum in acute Plasmodium falciparum malaria.

The purpose of the present study was to measure serum concentrations of stem cell factor (SCF) and interleukin-3 (IL-3) in patients with acute Plasmodium falciparum malaria. Serum samples from 15 patients were taken on day of admission and days 7, 14, 21, and 28. Anemia developed in 80% of patients. A transient increase in IL-3 could be observed at the beginning of the disease. It remains controversial whether the measured concentrations of IL-3 and SCF correlate with the grade of anemia. The possibly suppressed IL-3 and SCF production may contribute to the prolonged anemia in P. falciparum malaria, as has been shown for erythropoietin.     

An Immunohistochemical Study of the Pathology of Fatal Malaria: Evidence for Widespread Endothelial Activation and a Potential Role for Intercellular Adhesion Molecule-1 in Cerebral Sequestration

The sequestration of parasitized erythrocytes in the microvasculature of vital organs is central to the pathogenesis of severe Plasmodium falciparum malaria. This process is mediated by specific interactions between parasite adherence ligands and host receptors on vascular endothelium such as intercellular adhesion molecule-1 (ICAM-1) and CD36. Using immunohistochemistry we have examined the distribution of putative sequestration receptors in different organs from fatal cases of P.falciparum malaria and noninfected controls. Receptor expression and parasite sequestration in the brain were quantified and correlated. Fatal malaria was associated with widespread induction of endothelial activation markers, with significantly higher levels of ICAM-1 and E-selectin expression on vessels in the brain. In contrast, cerebral endothelial CD36 and thrombospondin staining were sparse, with no evidence for increased expression in malaria. There was highly significant co-localization of sequestration with the expression of ICAM-1, CD36, and E-selectin in cerebral vessels but no cellular inflammatory response. These results suggest that these receptors have a role in sequestration in vivo and indicate that systemic endothelial activation is a feature of fatal malaria.     

Strong linkage disequilibrium of a HbE variant with the (AT)9(T)5 repeat in the BP1 binding site upstream of the β-globin gene in the Thai population

A binding site for the repressor protein BP1, which contains a tandem (AT)_x(T)_y repeat, is located approximately 530 bp 5 to the human -globin gene (HBB). There is accumulating evidence that BP1 binds to the (AT)₉(T)₅ allele more strongly than to other alleles, thereby reducing the expression of HBB. In this study, we investigated polymorphisms in the (AT)_x(T)_y repeat in 57 individuals living in Thailand, including three homozygotes for the hemoglobin E variant (HbE; 26Glu->Lys), 22 heterozygotes, and 32 normal homozygotes. We found that (AT)₉(T)₅ and (AT)₇(T)₇ alleles were predominant in the studied population and that the HbE variant is in strong linkage disequilibrium with the (AT)₉(T)₅ allele, which can explain why the ^E chain is inefficiently synthesized compared to the normal ^A chain. Moreover, the mildness of the HbE disease compared to other hemoglobinopathies in Thai may be due, in part, to the presence of the (AT)₉(T)₅ repeat on the HbE chromosome. In addition, a novel (AC)_n polymorphism adjacent to the (AT)_x(T)_y repeat (i.e., (AC)₃(AT)₇(T)₅) was found through the variation screening in this study.MIM and accession numbers and URLs for data presented herein are as follows: Online Mendelian Inheritance of Man (OMIM), (for HBB [MIM 141900]). GenBank, (accession number [NG_000007.2] reference sequence information).     

Reduced levels of transforming growth factor-beta1, interleukin-12 and increased migration inhibitory factor are associated with severe malaria

In the present study, we investigated plasma levels of interleukin (IL)-12 and transforming growth factor (TGF-beta1) in malaria patients as these two cytokines regulate the balance between pro- and anti-inflammatory cytokines. We compared plasma IL-12 and TGF-beta1 levels in groups of malaria patients categorized as uncomplicated, severe, cerebral and placental malaria. Both TGF-beta1 and IL-12 levels were significantly reduced in peripheral plasma of adults with severe and cerebral malaria as well as in plasma of Tanzanian children with cerebral malaria (P<0.05). Similar results were observed with both placental and peripheral plasma of pregnant women who were infected with Plasmodium falciparum. IL-18, a cytokine known to be critical for the induction of IFN-gamma along with IL-1, was produced more in uncomplicated adult patients than in aparasitimic healthy controls (P<0.05). However, IL-18 response rate declined as the symptoms of the disease became more severe suggesting that the IL-18 response may be impaired with increased malaria severity. Together, the results of the three cytokines support the notion that imbalance between pro- and anti-inflammatory cytokines may contribute to the development of severe malaria infection. With malaria infection during pregnancy, we demonstrated that macrophage migration inhibitory factor (MIF) levels in infected placental plasma were significantly higher than those in the paired peripheral plasma (P<0.05). MIF, therefore, may play an important role in the local immune response to placental P. falciparum infection.     

Low CD8+ T lymphocyte response to P. falciparum circumsporozoite protein in naturally-exposed malaria endemic populations in Thailand

Cytotoxic T lymphocytes (CTLs) specific for epitope(s) within the circumsporozoite (CS) protein of malaria sporozoite have been shown to play an important role in protective immunity against malaria. Human CTLs against the potential epitope at the carboxy terminal region of CS protein of Plasmodium falciparum 7G8 strain (Pf7G8CS 368-390) were determined in thirty-six falciparum malaria patients and ten healthy controls. Four of 36 individuals and none of the healthy controls developed Pf7G8CS 368-390 specific CTL activity. The CTL activity was antigen specific and CD8+ T cell dependent. Although low CTL response has been determined, the study suggested that there was a correlation between initial parasitemia and the specific Pf7G8CS 368-390 CTL activity. A correlation between such CTL activity and anti-R32tet32 antibody levels among individuals with previous malaria experience was found, which was in contrast to those among individuals with recent malaria infection. All these 4 CTL positive individuals had at least two episodes of clinical malaria experience while all 25 individuals who were exposed to malaria for the first time did not have such a specific CTL response. These results showed that individuals with a history of natural endemic exposure to P. falciparum sporozoite developed low specific CTL responses to Pf7G8CS 368-390, so that previous but recent sporozoite exposure might be a prerequisite for generation of such CS protein specific CTL response.     

An open randomized clinical trial of Artekin vs artesunate-mefloquine in the treatment of acute uncomplicated falciparum malaria

Malaria remains a major cause of morbidity and mortality in tropical countries and subtropical regions in the world. Southeast Asia has the most resistant malaria parasites in the world, which has limited treatment options in this region. In response to this situation, short-course artemisinin-based combination therapies (ACTs) have been developed. The combination of dihydroartemisinin (DHA) and piperaquine (PQP) in the form of Artekin has been developed as an alternative to established combinations, such as artesunate-mefloquine, primarily to reduce treatment costs and toxicity. We conducted a study comparing a standard treatment for acute uncomplicated falciparum malaria (artesunate 4 mg/kg/day together with mefloquine 8 mg/kg/day oral route once a day for 3 days) (Group A) and a combination of dihydroartemisinin 40 mg and piperaquine 320 mg in the form of Artekin given once a day for 3 days (Group B) to determine safety, efficacy, and tolerability. One hundred and eighty patients were randomly enrolled at the ratio of 1:2 into groups A:B. All patients had rapid initial clinical and parasitological responses. There were no significant differences in fever clearance time or parasite clearance time between both groups. The 28-day cure rates were high, at 100% and 99%, in groups A and B, respectively. We conclude that Artekin was as effective and well-tolerated as artesunate-mefloquine, and can be used alternatively as the current treatment for multidrug-resistant P. falciparum malaria.     

An open, randomized trial of three-day treatment with artesunate combined with a standard dose of mefloquine divided over either two or three days, for acute, uncomplicated falciparum malaria

The combination of artesunate and mefloquine is currently one of the most effective treatments for multidrug-resistant Plasmodium falciparum malaria. Simultaneous, rather than sequential treatment with the two drugs, would allow better patient compliance. We therefore evaluated three-day treatment with artesunate combined with either 2 or 3 days of mefloquine co-administered once a day with artesunate. The study was an open, randomized trial for acute, uncomplicated falciparum malaria and was conducted at the Bangkok Hospital for Tropical Diseases. One hundred and twenty adult patients were randomized to two treatment groups. Group 1 patients received 4 mg/kg/day of artesunate for 3 days and 3 daily doses of 8.0 mg/kg/day mefloquine given with artesunate. Group 2 patients received the same dose of artesunate and the same total dose of mefloquine (25 mg/kg). However, the mefloquine was given as 15 mg/kg on the first day and 10 mg/kg/ on the second day, again with artesunate. The baseline demographic and clinical characteristics of the patients in the two groups were similar. The cure rates for the 3-day and 2-day mefloquine regimens were 100% and 99%, respectively. There were no significant differences in either median fever clearance times (group 1=32 hours; group 2=33 hours) or mean parasite clearance times (group 1=42.3 hours; group 2=43.3 hours). Both regimens were well tolerated and there were no significant differences in the incidence of adverse effects. Nausea or vomiting occurred in 3.8% of patients in both groups and transient dizziness occurred in 4% of group 1 and 9% of group 2 patients. These results suggest that a 3-day regimen of mefloquine administered with artesunate is effective and well tolerated. This practical regimen could improve patient compliance.     

Erythrocyte survival in severe falciparum malaria.

Erythrocyte survival was studied in 17 Thai patients (10 males, 7 females; aged 13-57 years) with severe falciparum malaria. To ensure radioisotopic labelling of cells before bone marrow recovery and survival analysis under near-steady state conditions, 51Cr labelling of autologous erythrocytes was performed at the time of admission (0 h) and calculation of mean cell lifespan (MCL) was based on semilogarithmic plots of corrected counts from 60 h onwards. Five patients received blood transfusions, all within 48 h of admission. The overall mean (+/- S.D.) MCL was short (44.1 +/- 21.7 days). Nontransfused patients had similar MCL values (43.6 +/- 20.4) to those of transfused patients (45.5 +/- 27.3 days, p greater than 0.8). Patients with and without palpable splenomegaly had MCL values which were not significantly different (54.1 +/- 28.8 vs. 37.2 +/- 12.3 days respectively, p greater than 0.1). There was no association between admission haematocrit or peripheral parasitaemia and MCL (p greater than 0.2 in each case), but there was an inverse correlation between total serum bilirubin and MCL (r = -0.49, p less than 0.025). There is accelerated destruction of non-parasitised erythrocytes in severe malaria resulting in a mean MCL that is half that found previously in healthy Thai volunteers (89.6 +/- 13.1 days, p less than 0.001) and significantly shorter than that reported previously in Thai patients with uncomplicated P. falciparum infections studied after parasite clearance (56.8 +/- 10.2 days, p less than 0.05).