Host vascular endothelial growth factor is trophic for Plasmodium falciparum-infected red blood cells.

Plasmodium falciparum, the protozoan parasite responsible for severe malaria infection, undergoes a complex life cycle. Infected red blood cells (iRBC) sequester in host cerebral microvessels, which underlies the pathology of cerebral malaria. Using immunohistochemistry on post mortem brain samples, we demonstrated positive staining for vascular endothelial growth factor (VEGF) on iRBC. Confocal microscopy of cultured iRBC revealed accumulation of VEGF within the parasitophorous vacuole, expression of host VEGF-receptor 1 and activated VEGF-receptor 2 on the surface of iRBC, but no accumulation of VEGF receptors within the iRBC. Addition of VEGF to parasite cultures had a trophic effect on parasite growth and also partially rescued growth of drug treated parasites. Both these effects were abrogated when parasites were grown in serum-free medium, suggesting a requirement for soluble VEGF receptor. We conclude that P. falciparum iRBC can bind host VEGF-R on the erythrocyte membrane and accumulate host VEGF within the parasitophorous vacuole, which may have a trophic effect on parasite growth.

Quantitation of cell-derived microparticles in plasma using flow rate based calibration.

Activation of vascular endothelium and blood cells can result in the formation of microparticles (MPs), which are membrane vesicles with a diameter < 1 microm which can play a pathogenetic role in a variety of infectious and other diseases. In this study, we validated a modified quantitative method called "flow rate based calibration", to measure circulating MPs in plasma of healthy subjects and malaria patients using FACSCalibur flow cytometry. MPs counts obtained from "flow rate based calibration" correlated closely with the standard method (R2 = 0.9, p = 0.001). The median (range) number of MPs in healthy subjects was 163/microl (81-375/microl). We demonstrated a flow rate based calibration for the quantitation of MPs in P. falciparum malaria-infected patients. The median (range) number of MPs was 2,051/microl (222-6,432/microl), n = 28 in patients with falciparum malaria. The number of MPs in plasma from patients with severe falciparum malaria was significantly higher than in uncomplicated falciparum malaria (2,567/microl (366-6,432/microl), n = 18 versus [1,947/microl (222-4,107/microl), n = 10, p < 0.01]. Cellular origin of MPs in malaria patients were mainly derived from red blood cells (35%), platelets (10%), and endothelial cells (5%). There was no significant correlation between the total number of MPs and parasitemia. Flow rate based calibration is a simple, reliable, reproducible method and more affordable to quantitate MPs.

A quantitative ultrastructural study of the liver and the spleen in fatal falciparum malaria.

We performed a retrospective study of 25 patients who died of severe falciparum malaria in Thailand and Vietnam using electron microscopy. The aims of the study were: to determine if there was any significant association between parasitized red blood cells (PRBC) sequestered in liver and spleen and particular pre-mortem clinical complications, and to compare the degree of parasite load between the liver and spleen within the same patients. PRBC sequestrations in each organ were compared with the pre-mortem parasitemia, to calculate the sequestration index (S.I.). The S.I. showed that the degree of PRBC sequestration in the spleen was higher than the liver (S.I. median = 3.13, 0.87, respectively) (p < 0.05). The results of quantitative ultrastructural study showed a significantly high parasite load in the liver of patients with jaundice, hepatomegaly and liver enzyme elevation (p < 0.05). We found a significant correlation between PRBC sequestration in the liver and a high serum bilirubin level, a high aspartate aminotransferase (AST) level and an increase in the size of the liver (Spearman's correlation coefficient = 0.688, 0.572, 0.736, respectively). Furthermore, a higher parasite load was found in the liver of patients with acute renal failure (ARF) compared to patients without ARF (p < 0.05). These findings suggest that PRBC sequestration in the liver is quantitatively associated with pre-mortem hepatic dysfunction and renal impairment. There was no significant difference between splenomegaly and PRBC sequestration. The size of a palpable spleen was not correlated with parasite load in the spleen. When ultrastructural features were compared between the two reticuloendothelial organs, we found that the spleen had more PRBC and phagocytes than the liver. The spleen of non-cerebral malaria (NCM) patients had more phagocytes than cerebral malaria (CM) patients. This observation reveals that the spleen plays a major role in malaria parasite clearance, and is associated with host defence mechanisms against malaria.

Clinical and mycological responses to fluconazole and fluconazole MIC in oropharyngeal candidiasis in HIV-infected patients.

INTRODUCTION: OPC is a common opportunistic infection in HIV-infected patients. Although some patients are asymptomatic, progression of the disease may occur leading to esophageal candidiasis. Fluconazole resistant candidiasis has been reported in several international studies. OBJECTIVES: This study aimed to test the MICs (minimal inhibitory concentrations) to fluconazole of Candida species isolated from mouthwash specimens of 54 HIV positive patients with oral candidiasis. Clinical and mycological responses to fluconazole were also assessed in 16 patients. MATERIAL AND METHOD: This was a prospective study. Mouthwash specimens were cultured on sabouraud dextrose agar twice. Candida species identification was performed and MICs for fluconazole were obtained using NCCLS guidelines. Clinical and mycological responses were assessed on day 14 and 42 in 16 patients who received a 14-day course of fluconazole. RESULTS: 48/54 patients (88.89%) were found to carry pure C. albicans. The other 6 patients (11.11%) had mixed Candida species on cultures. Among these 6 patients, 5 patients had mixed C. albicans and C. glabrata, and 1 patient had C. albicans and C. krusei. Fluconazole MICs of C. albicans, C. glabrata, and C. krusei ranged from 0.125-32 (median=0.250), 4-64 (median=2), and 8 g/L respectively. This study showed that the MICs to fluconazole of oropharyngeal Candida was a good predictor of the therapeutic responses.