Lymphocyte immunophenotype reference ranges in healthy Thai adults: implications for management of HIV/AIDS in Thailand.

Lymphocyte immunophenotype reference ranges for T, B, and NK subsets were determined for healthy adult Thais in a multi-center study in Bangkok. Immunophenotyping was by flow cytometry using lysed whole blood. A standard protocol for flow cytometry instrumentation, reagents and quality control was used to minimize site differences and to facilitate comparison of the Thai reference values to those found for Caucasians in previous studies. Major differences were determined for CD3(T), CD4 (T helper/inducer) and CD16+56 (NK) lymphocyte percentages and CD4 lymphocyte absolute counts. Age trends and sex differences were also observed. Compared to Caucasians, Thais, particularly Thai males, had lower CD3 and CD4 T lymphocyte percentages and absolute numbers whereas the percentage of NK lymphocytes was higher. Heterogeneity attributed to biological variation of CD4 T lymphocyte but not other immunophenotype subset distributions was also observed in a well defined geographic population. This study demonstrates the importance of ethnicity, age, sex and possibly environment as factors that influence distribution characteristics of normal lymphocyte immunophenotype reference values. These observations have important implications for the use of lymphocyte subsets-particularly CD3+ CD4+ T lymphocyte measurements as applied to HIV disease staging, AIDS definition and the overall clinical management of HIV/AIDS in Thailand.

Prevention of Plasmodium falciparum malaria by Fansimef and Lariam in the northeastern part of Thailand.

Two studies were conduct in Thailand in order to find appropriate falciparum malaria prophylactic drug regimens. The first study was done during June - September 1987 with 363 soldiers who received Fansimef (MSP) 1 tab/week (group 1), 337 soldiers who received MSP 1 tab/2 week (group 2) and 165 soldiers who received chloroquine 300 mg base weekly plus Fansidar 1 tab/week (group 3). At the end of the study there were 9 and 13 falciparum malaria episodes in groups 1 and 2, respectively, with incidence rates of 0.8 and 1.8 cases/100 person-months (P-M). In group 3, the corresponding values were 30 episodes and an incidence of 7.2/100 P-M. For the second study which lasted from October 1987 - January 1988 in the same area, 498 soldiers were given Fansimef 1/2 tab/week (group 4), 499 soldiers were given Lariam 1/2 tab/week (group 5) and 247 soldiers were given chloroquine plus Fansidar (group 6). Thirty malaria episodes were found in group 4, for an incidence of 2.0/100 P-M. In group 5, 23 episodes were found, for an incidence of 1.6/100 P-M. In group 6, 74 episodes occurred, ie an incidence of 12.2/100 P-M. The incidence rates of malaria among Fansimef 1 tab weekly, Fansimef half dose weekly or Lariam half dose weekly were not significantly different but were different from chloroquine plus Fansidar groups. Adverse events in each group were mild.

Practical uses of acridine orange fluorescence microscopy of centrifuged blood (QBC Malaria Test) and the QBCII Hematology System in patients attending malaria clinics in Thailand.

We evaluated the detection of malaria parasites using acridine orange fluorescence microscopy of centrifuged blood (AOFM/CB or "QBC Malaria Test") at two government malaria clinics in rural Thailand. In a subgroup of the patients, a QBC Hematology System for the determination of complete blood counts was also utilized. A Giemsa-stained thick smear (GTS) reading of 100 (1,000x) microscopic fields was used as standard. The AOFM/CB sensitivities were 97% overall and 95% for P. falciparum (Pf). Sensitivity was lower for P. vivax (Pv) (76%). Pv sensitivity depended largely on ameboid form density. A threshold for AOFM/CB to consistently detect Pv ameboid forms was estimated to be 10/100 WBC (700/microliters blood). AOFM/CB was capable of detecting Pf gametocytes and schizonts more frequently than GTS. The total Pf rings per microliter blood estimated from GTS was highly correlated with the number of Pf rings per Paralens microscopic field (PMF) suggesting that AOFM/CB could be used quantitatively. From a technical standpoint, the rural tropical settings of Thailand in this study were not an obstacle to the use of QBC Hematology. The system was found to be useful in conjunction with AOFM/CB. However, in patients heavily infected with Pf gametocytes of Pv ameboid forms, their total WBC and lymphocyte counts needed to be appropriately corrected. Overall, AOFM/CB appears to be a promising tool for field diagnosis of malaria if it is affordable to developing countries.

Lymphocyte subpopulations during acute and convalescence phases of malaria.

Lymphocytes of normal healthy persons were separated from blood by Ficoll-Hypaque gradient centrifugation and iron-magnet application. peripheral blood lymphocytes (PBL) were stained by various dye-labeled monoclonal antibodies. Cells positive for specific surface markers were enumerated by a fluorescence activated cell sorter (FACS) and fluorescence microscope (FM). The results revealed that the percentages of cells positive with one monoclonal antibody counted by these two techniques were similar while the percentages of cells with double staining were higher when counted by FACS than by FM. Lymphocyte subpopulations of 18 patients infected with Plasmodium falciparum during acute and convalescence period were studied. Lymphocytopenia occurred during the acute infection while total white blood cell counts were normal. PBL of the patients were stained with OKT3, OKT4, OKT8, Leu-11 and a combination of Leu-7, Leu-1 monoclonal antibodies. The absolute numbers of all lymphocyte subpopulations were decreased during the acute infection while T8 positive cells were decreased in both percentage and absolute number. Thus T4:T8 ratio (1.7:1) became higher than normal (1.3:1) at this period. During convalescence phase, absolute numbers and percentages of Leu-7+, Leu-1+ and perhaps Leu-7+, Leu-11- cells which had low NK cell activity were significantly higher than during acute illness. The finding might explain why the NK cell activity was low during the convalescence period.

In vitro mefloquine resistance of Plasmodium falciparum isolated from the Burmese border region of Thailand.

The in vitro susceptibility of twenty isolates of Plasmodium falciparum from Tha Song Yang, Tak province, Thailand were determined. The isolates were resistant to chloroquine (IC50 = 220 nM; MIC = 762 nM), quinine (IC50 = 252 nM; MIC = 1010 nM), and pyrimethamine (IC50 = 16400 nM; MIC = 43100 nM) but generally sensitive to mefloquine (IC50 = 6.90 nM; MIC = 20.9 nM) and halofantrine (IC50 = 8.73 nM; MIC = 2.71 nM). Two isolates were identified which appeared resistant to mefloquine (IC50 = 23.1 nM; MIC = 56.6 nM). These isolates may represent an extension of a population of parasites from eastern Thailand.