Search

Melioidosis is a major cause of fatal community-acquired septicemia in highly endemic areas, including northeast Thailand and north Australia (2,2). Melioidosis is now known to be endemic in [greater than [...]

Melioidosis is a neglected tropical disease with an estimated annual global mortality rate of 89,000 (1). Its cause is the gram-negative bacterium Burkholderia pseudomallei, which is found in environmental soil [...]

Abstract Background Apparent emerging artemisinin-resistant Plasmodium falciparum malaria in Southeast Asia requires development of practical tools to monitor for resistant parasites. Although in vitro anti-malarial susceptibility tests are widely used, uncertainties remain regarding interpretation of P. falciparum field isolate values. Methods Performance parameters of the W2 P. falciparum clone (considered artemisinin “sensitive”) were evaluated as a reference for the HRP-2 immediate ex vivo assay. Variability in W2 IC50s was assessed, including intra- and inter-assay variability among and between technicians in multiple experiments, over five freeze-thaw cycles, over five months of continuous culture, and before and after transport of drug-coated plates to remote field sites. Nominal drug plate concentrations of artesunate (AS) and dihydroartemisinin (DHA) were verified by LC-MS analysis. Plasmodium falciparum field isolate IC50s for DHA from subjects in an artemisinin-resistant area in Cambodia were compared with W2 susceptibility. Results Plate drug concentrations and day-to-day technical assay performance among technicians were important sources of variability for W2 IC50s within and between assays. Freeze-thaw cycles, long-term continuous culture, and transport to and from remote sites had less influence. Despite variability in W2 susceptibility, the median IC50s for DHA for Cambodian field isolates were higher (p Conclusion The W2 reference clone improved the interpretability of field isolate susceptibility from the immediate ex vivo HRP-2 assay from areas of artemisinin resistance. Methods to increase the reproducibility of plate coating may improve overall assay interpretability and utility.

Abstract Background In vitro drug susceptibility assay of Plasmodium falciparum field isolates processed “immediate ex vivo” (IEV), without culture adaption, and tested using histidine-rich protein-2 (HRP-2) detection as an assay, is an expedient way to track drug resistance. Methods From 2005 to 2010, a HRP-2 in vitro assay assessed 451 P. falciparum field isolates obtained from subjects with malaria in western and northern Cambodia, and eastern Thailand, processed IEV, for 50% inhibitory concentrations (IC50) against seven anti-malarial drugs, including artesunate (AS), dihydroartemisinin (DHA), and piperaquine. Results In western Cambodia, from 2006 to 2010, geometric mean (GM) IC50 values for chloroquine, mefloquine, quinine, AS, DHA, and lumefantrine increased. In northern Cambodia, from 2009–2010, GM IC50 values for most drugs approximated the highest western Cambodia GM IC50 values in 2009 or 2010. Conclusions Western Cambodia is associated with sustained reductions in anti-malarial drug susceptibility, including the artemisinins, with possible emergence, or spread, to northern Cambodia. This potential public health crisis supports continued in vitro drug IC50 monitoring of P. falciparum isolates at key locations in the region.

Melioidosis is a life-threatening infectious disease caused by the gram-negative bacillus Burkholderia pseudomallei. An effective vaccine is needed, but data on protective immune responses in human melioidosis are lacking. We used ELISA and an antibody-dependent cellular phagocytosis assay to identify the major features of protective antibodies in patients with acute melioidosis in Thailand. We found that high levels of B. pseudomallei-specific IgG2 are associated with protection against death in a multivariable logistic regression analysis adjusting for age, diabetes, renal disease, and neutrophil count. Serum from melioidosis survivors enhanced bacteria uptake into human monocytes expressing FcγRIIa-H/R131, an intermediate-affinity IgG2-receptor, compared with serum from nonsurvivors. We did not find this enhancement when using monocytes carrying the low IgG2-affinity FcγRIIa-R131 allele. The findings indicate the importance of IgG2 in protection against death in human melioidosis, a crucial finding for antibody-based therapeutics and vaccine development. [ABSTRACT FROM AUTHOR]

Melioidosis is a neglected tropical disease with an estimated annual mortality rate of 89,000 in 45 countries across tropical regions. The causative agent is Burkholderia pseudomallei, a gram-negative soil-dwelling bacterium. In Thailand, B. pseudomallei can be found across multiple regions, along with the low-virulence B. thailandensis and the recently discovered B. thailandensis variant (BTCV), which expresses B. pseudomallei-like capsular polysaccharide. Comprehensive studies of human immune responses to B. thailandensis variants and cross-reactivity to B. pseudomallei are not complete. We evaluated human immune responses to B. pseudomallei, B. thailandensis, and BTCV in melioidosis patients and healthy persons in B. pseudomallei-endemic areas using a range of humoral and cellular immune assays. We found immune cross-reactivity to be strong for both humoral and cellular immunity among B. pseudomallei, B. thailandensis, and BTCV. Our findings suggest that environmental exposure to low-virulence strains may build cellular immunity to B. pseudomallei. [ABSTRACT FROM AUTHOR]

Background: Hybridomas that produce human monoclonal antibodies (HuMAbs) against Dengue virus (DV) had been prepared previously using peripheral blood lymphocytes from patients with DV during the acute and convalescent phases of a secondary infection. Anti-DV envelope glycoprotein (E) 99 clones, anti-DV premembrane protein (prM) 8 clones, and anti-DV nonstructural protein 1 (NS1) 4 clones were derived from four acute-phase patients, and anti-DV E 2 clones, anti-DV prM 2 clones, and anti-DV NS1 8 clones were derived from five convalescent-phase patients. Methods and results: In the present study, we examined whether these clones cross-reacted with Japanese encephalitis virus (JEV), which belongs to the same virus family. Forty-six of the above-described 99 (46/99) anti-E, 0/8 anti-prM, and 2/4 anti-NS1 HuMAbs from acute-phase, and 0/2 anti-E, 0/2 anti-prM, and 5/8 anti-NS1 HuMAbs from convalescent-phase showed neutralizing activity against JEV. Thus, most of the anti-E and anti-NS1 (but not the anti-prM) antibodies cross-reacted with JEV and neutralized this virus. Interestingly, 3/46 anti-E HuMAbs derived from acute-phase patients and 3/5 anti-NS1 HuMAbs from convalescent-phase patients showed particularly high neutralizing activity against JEV. Consequently, the HuMAbs showing neutralization against JEV mostly consisted of two populations: one was HuMAbs recognizing DV E and showing neutralization activity against all four DV serotypes (complex-type) and the other was HuMAbs recognizing DV NS1 and showing subcomplex-type cross-reaction with DV. Conclusion: Anti-DV E from acute phase (46/99) and anti-DV NS1 (7/12) indicate neutralizing activity against JEV. In particular, three of 46 anti-DV E clones from acute phase and three of five anti-NS1 clones from convalescent phase showed strong neutralizing activity against JEV. [ABSTRACT FROM AUTHOR]

Background: Hybridomas that produce human monoclonal antibodies (HuMAbs) against Dengue virus (DV) had been prepared previously using peripheral blood lymphocytes from patients with DV during the acute and convalescent phases of a secondary infection. Anti-DV envelope glycoprotein (E) 99 clones, anti-DV premembrane protein (prM) 8 clones, and anti-DV nonstructural protein 1 (NS1) 4 clones were derived from four acute-phase patients, and anti-DV E 2 clones, anti-DV prM 2 clones, and anti-DV NS1 8 clones were derived from five convalescent-phase patients., Methods and Results: In the present study, we examined whether these clones cross-reacted with Japanese encephalitis virus (JEV), which belongs to the same virus family. Forty-six of the above-described 99 (46/99) anti-E, 0/8 anti-prM, and 2/4 anti-NS1 HuMAbs from acute-phase, and 0/2 anti-E, 0/2 anti-prM, and 5/8 anti-NS1 HuMAbs from convalescent-phase showed neutralizing activity against JEV. Thus, most of the anti-E and anti-NS1 (but not the anti-prM) antibodies cross-reacted with JEV and neutralized this virus. Interestingly, 3/46 anti-E HuMAbs derived from acute-phase patients and 3/5 anti-NS1 HuMAbs from convalescent-phase patients showed particularly high neutralizing activity against JEV. Consequently, the HuMAbs showing neutralization against JEV mostly consisted of two populations: one was HuMAbs recognizing DV E and showing neutralization activity against all four DV serotypes (complex-type) and the other was HuMAbs recognizing DV NS1 and showing subcomplex-type cross-reaction with DV., Conclusion: Anti-DV E from acute phase (46/99) and anti-DV NS1 (7/12) indicate neutralizing activity against JEV. In particular, three of 46 anti-DV E clones from acute phase and three of five anti-NS1 clones from convalescent phase showed strong neutralizing activity against JEV.