Complete development of the liver stage of Plasmodium falciparum in a human hepatoma cell line.

Plasmodium falciparum parasites develop in the liver before being released into the bloodstream, where they exert the potentially lethal effects characteristic of malaria. Our understanding of the hepatic phase of the life cycle is limited by the parasite's requirement for fresh human liver cells in which to mature. In this work, liver parasites completed their development within a Thai human hepatoma cell line (HHS-102), and the presence of ring-form parasites in erythrocytes overlying the liver cell culture confirmed that an entire liver cycle was completed, culminating in the production of viable blood-stage parasites.

Quinine with tetracycline for the treatment of drug-resistant falciparum malaria in Thailand.

Reports of deteriorating quinine efficacy prompted us to investigate the ability of quinine-tetracycline to clear parasites and fever from patients with multiple drug-resistant Plasmodium falciparum infections. Past and present treatment results were compared at two study sites along the Thai-Cambodian border. In northeastern Thailand, quinine-tetracycline cleared parasites more quickly in 1990 than in 1987 (mean 3.

Ciprofloxacin treatment of drug-resistant falciparum malaria.

A randomized, open study of high-dose ciprofloxacin (750 mg every 12 h) in uncomplicated falciparum malaria was conducted in Thailand. No patient completed the planned 1-week treatment course. Because of rising parasitemia (threefold higher at 36 h than on admission) and deterioration of clinical status, three individuals required quinine treatment 36 h after commencing ciprofloxacin; a fourth was given quinine at 54 h.

Malaria: treatment efficacy of halofantrine (WR 171,669) in initial field trials in Thailand.

Halofantrine (WR 171,669) hydrochloride was administered orally to 82 patients infected with Plasmodium falciparum malaria on the Thai-Kampuchean border between June 1982 and December 1983 in a randomized double-blind treatment trial which compared the efficacy of halofantrine with that of mefloquine. Halofantrine was curative with oral treatment on a single day in 65% of patients (13/20) who received 1000 mg followed 6 hours later by an additional 500 mg, and in 88% of patients (53/60) who received 500 mg every 6 hours for 3 doses. Mefloquine was curative in 88% of patients (22/25) given a single oral dose of 1000 mg and in 97% of patients (38/39) given a single oral dose of 1500 mg.

Lymphocyte responsiveness to a candidate malaria sporozoite vaccine (R32tet32) of individuals with naturally acquired Plasmodium falciparum malaria.

Lymphocyte proliferative responses to the candidate malaria sporozoite vaccine antigen R32tet32 were evaluated in 29 patients with acute Plasmodium falciparum malaria, 20 convalescent patients, 11 nonimmune individuals, and 22 healthy residents of two endemic malarious areas in Thailand. The results indicate that 14 of 20 (70%) convalescent patients and 14 of 22 (64%) residents of endemic areas responded to the R32tet32 antigen. However, only 8 of 29 (28%) patients with acute P.

Polymorphism of proteins in malaria parasites following mefloquine treatment.

Proteins in malaria parasites (Plasmodium falciparum) isolated from a patient in Thailand before treatment, and after recrudescence of infection subsequent to mefloquine treatment, were compared by two dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis. Nine 'pre-treatment' and six 'recrudescent' clones were studied. Variants of the enzyme glucose phosphate isomerase were also noted and mefloquine susceptibility of each clone was measured by in vitro tests.

Cloning and characterization of mefloquine-resistant Plasmodium falciparum from Thailand.

Resistance to mefloquine in Plasmodium falciparum has begun to occur along the border of Thailand and Kampuchea. As a means of assessing the natural occurrence of mefloquine resistance, the admission and post-treatment parasite isolates from a mefloquine treatment failure were cloned and characterized. Clones from the admission isolate were susceptible to mefloquine in vitro (ID50 of 3.

Antimalarial drug susceptibility testing of Plasmodium falciparum in Thailand using a microdilution radioisotope method.

Antimalarial activity of chloroquine, quinine, mefloquine and halofantrine against 33 strains of P. falciparum isolated from naturally acquired malaria infections in Thailand was determined using a radioisotope microdilution method. A microtitration procedure was used to test isolates of P.

Deficiency of Con A-induced suppressor cell activity in peripheral blood mononuclear cells from Thai adults naturally infected with Plasmodium falciparum and Plasmodium vivax.

Con A-pretreated mononuclear (MNC) cells from Thai adults with naturally acquired P. falciparum or P. vivax malaria were significantly less effective in suppressing the responsiveness of autologous or normal allogeneic responder cells to mitogenic lectins or allogenic stimulator cells than pretreated cells from healthy donors.

Cold-reactive immunoglobulin M antilymphocyte antibodies directed against B cells in Thai children with dengue hemorrhagic fever.

Antilymphocyte antibodies were found in 51 of 83 serum specimens from Thai children with dengue hemorrhagic fever (DHF). The lymphocytotoxic activity was complement dependent, and cytotoxicity was detected in the 19S immunoglobulin M-associated serum fractions at a temperature optimum of 15 degrees C. Sera with lymphocytotoxic activity were cytotoxic to autologous as well as allogeneic lymphocytes from patients and healthy adult donors and were directed primarily against B cells, with some T cell cross-reactivity.

Subpopulations of T cells (Tg and Tm) in patients with malaria.

In the present study we utilized rosetting techniques to enumerate the putative suppressor (Tg) and helper (Tm) T-cell subpopulations in the peripheral blood of adult Thais with malaria. A lower percentage of both Tg and Tm subpopulations and a lower number and percentage of total T cells was found in these patients during the acute period of infection than in the peripheral blood of healthy donors. However, the percentages of total T, Tg and Tm cells were higher during the convalescent period and were comparable to the values found in the peripheral blood of healthy donors.

Characterization of cold reactive lymphocytotoxic antibodies in malaria.

Characterization of cold reactive lymphocytotoxic antibodies present in sera from Thai adults with malaria revealed that the antibodies are predominantly 19S (IgM), directed against both autologous and allogeneic mononuclear cells, complement-dependent, present in titres ranging from 1:2 to 1:16, and exhibit greater lymphocytotoxic activity during the acute stage of malarial infection than during the convalescent stage. The lymphocytotoxic antibodies were primarily directed against B cell targets or both B as well as T cell targets. In addition some sera were reactive with enriched monocyte/macrophage indicator cells at 15 degrees C, but not 37 degrees C.

Deficient spontaneous cell-mediated cytotoxicity and lectin-induced cellular cytotoxicity by peripheral blood mononuclear cells from Thai adults naturally infected with malaria.

To assess general cytotoxic effector cell capabilities by peripheral blood mononuclear cells from patients with active malaria infections, we examined antibody-dependent cellular cytotoxicity, spontaneous cell-mediated cytotoxicity, and lectin-induced cellular cytotoxicity by using human and chicken erythrocyte, Chang cell line, and K562 cell line targets. By using human erythrocyte and Change cell line targets, we found that Thai adults naturally infected with malaria had significantly impaired lectin-induced cellular cytotoxicity. In addition, spontaneous cell-mediated cytotoxicity was deficient with K562 but not with Chang cell line targets.

Effect of anti-coagulants on cold-reactive anti-lymphocyte activity in the blood of patients with malaria.

The effect of three different anti-coagulants on the level of cold-reactive anti-lymphocyte activity (ALA) in the peripheral blood (PB) of malarious individuals was assessed to determine if plasma could be substituted for serum in assays designed to characterize ALA. Results show that plasma obtained by treating PB with acid-citrate dextrose or ethylenediamine tetraacetic acid can be used instead of serum in these assays but that plasma obtained from heparin-treated blood cannot.

Inhibition of mitogenic lectin induced blast transformation in human peripheral blood mononuclear cells by mefloquine.

The effect of mefloquine-HCL, a new 4-quinoline methanol anti-malarial compound, on in vitro blast transformation of human peripheral blood mononuclear cells (MNC) was studied. Mefloquine significantly suppressed lectin-induced blast transformation of MNC from healthy Thai adults but MNC responsiveness in the mixed leucocyte reaction (MLR) and cellular viability were not reduced by the concentrations of mefloquine studied. Both T and non-T MNC responsiveness was lower in cultures containing the drug than in normal control cultures.

Suppression of mitogenic lectin-induced blast transformation of human peripheral blood mononuclear cells by pyrimethamine.

The anti-malarial drug pyrimethamine suppresses in vitro mitogenic lectin-induced blast transformation by human peripheral blood mononuclear cells (MNC) when the drug is added to cells (1 X 10(-5) M/culture). Sulphadoxine, a second widely used anti-malarial drug has no suppressive effect on the MNC. MNC responsiveness in the mixed leucocyte reaction and cellular viability are not altered by either pyrimethamine or sulphadoxine.

Kinetics of peripheral blood leukocyte alterations in Thai children with dengue hemorrhagic fever.

Peripheral leukocytes from 16 Thai children with dengue hemorrhagic fever were examined to determine the leukocyte composition on the day of presentation and on convalescent days 15 and 30. Mononuclear cells were isolated each time, and the concentrations of T, B, Fc receptor-bearing, and "null" cells were determined. On the day of hospitalization, in comparison to convalescent values, there was a significant increase in total lymphocytes, primarily due to concentrations of atypical lymphocytes.

Anti-lymphocytotoxic antibodies in sera of Thai adults infected with Plasmodium falciparum or Plasmodium vivax.

Because of the potential for the elimination of lymphocytes through anti-lymphocytotoxic antibodies we examined individual sera of patients infected with falciparum or vivax malaria for the presence of antibodies against normal peripheral blood mononuclear cells. In assays done at 15 degrees C, 95% of the P. falciparum patients and 98% of the P.

Loss of circulating T lymphocytes with normal levels of B and 'null' lymphocytes in Thai adults with malaria.

Peripheral blood mononuclear cells from forty-nine Thai adults infected with either Plasmodium falciparum or Plasmodium vivax were examined in order to determine the percentage of T, B, and Fc-receptor-bearing cells present. In comparison to healthy controls, both the percentage and concentration of peripheral T cells were decreased in the malaria-infected individuals as assessed by formation of rosettes with sheep red blood cells. The percentage of peripheral B cells was increased but their concentration was unchanged, as assessed by two techniques: the presence of surface immunoglobulin and the presence of a complement receptor.