PubMed Health⌕ Search

Biomedical subjects

S Tharavanij

Publications and source records attributed to S Tharavanij.

At least 19 recordsLinked to original sources
PubMed1992

Two-site pan-species monoclonal antibody ELISA for detection of blood stage malaria antigen.

A two-site pan-species monoclonal antibody sandwich ELISA (MAb-MAb ELISA) was developed to detect both Plasmodium vivax and P. falciparum antigens in whole blood impregnated on filter paper. In this assay, the plates were coated with pan-species MAb 3F9 and another pan-species MAb M26-32 conjugated with alkaline phosphatase was used for detection of bound antigen. The sensitivity of this assay was 5, 10 and 10 parasites per 10(6) erythrocytes for cultured P. falciparum, patient-derived P. vivax and P. falciparum, respectively. The coincidence rates for this assay were 93% (92/99) with healthy individuals and 93% (42/45) with microscopically confirmed vivax malaria cases. After two weeks treatment, 77.7% (14/18) of vivax malaria were still positive by this assay but with diminished level of reactivities [corrected].

Animals↗
PubMed1992

Two-site sandwich ELISA for detection of Plasmodium vivax blood stage antigens using monoclonal and polyclonal antibodies.

Two systems of sandwich enzyme-linked immunosorbent assay (ELISA), a two-site monoclonal antibody sandwich ELISA MAb-MAb sandwich ELISA) and a two site polyclonal-monoclonal antibody sandwich ELISA (PAb-MAb sandwich ELISA) for the detection of Plasmodium vivax antigens were developed. The assays showed good correlation with the level of parasitemia when tested against serially diluted P. vivax parasites (r = 0.937, and 0.997 for MAb-MAb and PAb-MAb sandwich ELISA, respectively), with the ability to detect as few as 6.68 parasites/10(6) erythrocytes and 2.69 parasites/10(3) erythrocytes, respectively. The MAb-MAb sandwich ELISA was specific, since it was positive only with P. vivax-infected erythrocytes from vivax malaria patients and negative when erythrocytes from 34 healthy individuals and 30 falciparum malaria cases were tested. In contrast, cross-reaction was found in the PAb-MAb sandwich ELISA when the plates were coated with polyclonal IgG and tested against the serially diluted P. falciparum SO strain antigen prepared from in vitro cultures. Comparison between the two systems of two-site sandwich ELISA showed that the MAb-MAb sandwich ELISA was superior to the PAb-MAb sandwich ELISA: (1) it gave a higher sensitivity when tested with serially diluted P. vivax antigen preparations from vivax malaria patients; (2) it gave a higher specificity when tested with the SO strain of P. falciparum from in vitro cultures, (3) it gave a lower absorbance value when tested with erythrocytes from healthy individuals. All 281 cases of vivax malaria already proven by microscopic examination were positive by MAb-MAb sandwich ELISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Competitive antibody binding inhibition ELISA for the detection of Plasmodium falciparum antigen.

A competitive antibody binding inhibition ELISA to detect Plasmodium falciparum-infected cells in clinical specimens was developed. Optimum conditions developed included: 12.5 micrograms/ml of P. falciparum antigen for plate coating, 25 micrograms/ml of polyclonal rabbit anti-P. falciparum IgG, 30 minute incubation of a mixture of infected red blood cell extract with anti-P. falciparum IgG, dilution of 1:500 of alkaline phosphatase-conjugated anti-rabbit IgG, and reading of the absorbance values 60 min after adding the p-nitrophenyl phosphate substrate. Reproducibility of the assay against cultured P. falciparum-infected red blood cells varied according to parasitemia, the higher the parasitemia, the better the reproducibility. The sensitivity of the assay was approximately 110 parasites/10(6) red blood cells. The assay was applied to field conditions involving 103 cases with falciparum malaria, 38 cases with vivax malaria and 30 healthy controls. With the 10% antibody binding inhibition as a cutoff, 87.4% of falciparum cases and 26.3% of vivax cases were positive. After treatment, the majority of cases became parasitologically negative with the corresponding negative assay. Regression analysis showed only weak but statistically significant correlation between the percent inhibition with parasitemia (r = 0.38, p less than 0.001), and this was more clearly shown in patients with high parasitemia.

Animals↗
PubMed1989

Assessment of putative tests for protective immunity to falciparum malaria.

Sera from clinically immune individuals comprising 10 hospitalised patients (Group I), 30 persons residing in a malaria endemic area in Thailand (Group II) and 8 persons from a hyperendemic area in Ivory Coast (Group III) were tested by the parasite growth inhibition (PGI), indirect fluorescent antibody test of ring-infected erythrocyte surface antigen (RESA-IFA), urease-ELISA and Western blot. Paired sera from patients recovering from malaria (Group IV) as well as sera from blood donors were also tested. In the PGI test, sera were tested against three uncloned isolates of P. falciparum comprising SO, I4 and AE9 (PGI-SO, PGI-I4 and PGI-AE9 respectively). When growth inhibition of greater than or equal to 30% against any one of the three isolates was considered positive, the positive rate for the combined Groups I, II and III was 78.7%. Further analysis showed that the positive rates for PGI-SO, PGI-I4 and PGI-AE9 were 63.8%, 59.5% and 59.5% respectively and were not significantly different (p greater than 0.05). Comparison between PGI-SO, PGI-I4 and PGI-AE9 activities of Groups I, II and III sera showed no significant differences in any comparison groups except with PGI-AE9 in which Group III sera were more frequently positive than Group II sera (p = 0.004). Follow-up of PGI-SO and PGI-AE9 activities in Group IV patients showed mostly a decrease or no change in the activities of the convalescent sera taken 63 days later. RESA-IFA positive rate in the combined Groups I, II and III sera was 91.7%. There were no significant differences either in the seropositive rates or in the geometric mean antibody titers (GMT) between Groups I, II and III sera. Follow-up in Group IV patients showed no change in antibody titers in 64% of cases, decrease and increase in titers in 29% and 7% of cases respectively. The urease-ELISA seropositive rate in the combined Groups (I, II and III) was 89.5% which is not significantly different from that of RESA-IFA (p greater than 0.05). Comparison between individual Groups (I, II and III) likewise showed no significant differences in both GMT and seropositive rates. Follow-up in Group IV sera showed either no change or a decrease in antibody titers in 55.6% and 44.4% of cases respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Antibody against a ring-infected erythrocyte surface antigen in cerebral and non-cerebral malaria patients.

An indirect fluorescent antibody test for glutaraldehyde-fixed, ring-infected erythrocyte surface antigen was performed on admission sera from 45 patients with complicated cerebral Plasmodium falciparum malaria, 33 with uncomplicated cerebral malaria, 91 non-cerebral malaria patients, and 53 blood donors from a non-malarious area. 14 (31%), 28 (85%), 64 (70%), and 1 (2%), respectively, had titres greater than or equal to 1/25, considered as positive. The seropositive rate and the geometric mean reciprocal titre of patients with complicated cerebral malaria were significantly lower than those of uncomplicated and non-cerebral patients, particularly in the 6-14 and 15-29 year age groups. Compared with non-cerebral patients, lower seropositive rates for patients with complicated cerebral malaria were demonstrated only in those who had been ill 4 or more days before admission; whereas lower rates for patients with complications, when compared with rates in those with uncomplicated cerebral malaria, occurred irrespective of the duration of illness.

Animals↗
PubMed1988

Field applications of an immunoradiometric assay for the detection of Plasmodium falciparum antigen in a population in a malaria-endemic area in Thailand.

Two surveys were made in people living in a malaria-endemic area in West Thailand in October 1985 (a transmission season) and in May 1986 (a nontransmission season) to detect Plasmodium falciparum antigen using the immunoradiometric assay (IRMA). In the first survey involving 101 people, the IRMA-positive rate was 56.4% and then significantly declined to 16.5% during the second survey involving 79 people of the same group. The parasitological-positive rates were likewise decreased from 11.9% to 1.3% (P = 0.015) during these two seasons. IRMA-positive rates were significantly higher than the corresponding parasitological-positive rates (P less than 0.0001 and 0.002 for the first and the second surveys, respectively). The geometric mean IRMA binding activity of samples collected in the first survey (1,726 cpm) was significantly higher than those collected during the second survey (920 cpm, P = 0.001). Regression analysis showed that IRMA activities were linearly correlated with the parasite counts by microscopic examination (r = 0.629, P = 0.022). IRMA was specific for P. falciparum since all 30 healthy controls and 6 of 7 vivax malaria cases were negative.

Adolescent↗
PubMed1988

Detection of antibodies against Opisthorchis viverrini in patients before and after treatment with praziquantel.

Levels of antibody in sera of 78 patients with opisthorchiasis, 30 patients with other liver diseases, 10 patients with schistosomiasis and 30 healthy individuals were compared using three serodiagnostic tests, namely indirect haemagglutination (IHA), enzyme-linked immunosorbent assay (ELISA) and lectin immuno test (LIT). The geometric mean reciprocal titer in sera of opisthorchiasis patients was significantly higher than patients with other diseases, patients with schistosomiasis and healthy individuals (p less than 0.00001). After treatment with praziquantel, the antibody titers were decreased and became lowest 120 days after treatment. A statistically significant decrease from the pre-treatment sample was observed only at 120 days after infection and not earlier and only with ELISA (p = 0.03) and not with IHA and LIT (p greater than 0.05). Even with ELISA, significant decrease in antibody titer was apparent only when the pre-treatment sera had high enough antibody titer. ELISA was therefore better than the other two tests for the assessment of cure provided that the titer of pre-treatment sera was high.

Animals↗
PubMed1987

Two-site immunoradiometric assay for detection of Plasmodium falciparum antigen in blood using monoclonal and polyclonal antibodies.

Three systems of immunoradiometric assays (IRMAs), a two-site monoclonal antibody sandwich IRMA (MAb-IRMA), two-site polyclonal antibody-monoclonal antibody sandwich IRMA (PAb-MAb-IRMA), and two-site polyclonal antibody sandwich IRMA (PAb-IRMA), were developed to detect low-grade infections with Plasmodium falciparum. The assays showed good correlation with parasitemia when tested against parasites from in vitro cultures (r = 0.996, 0.994, and 0.998 for MAb-, PAb-MAb-, and PAb-IRMA, respectively), with the ability to detect as few as 0.24, 0.67, and 1.82 parasites per 10(7) erythrocytes, respectively. The assays were specific for P. falciparum, since a serially diluted specimen from a patient with vivax malaria with an initial parasitemia of 0.8% and almost all of the undiluted specimens from five other vivax malaria patients were negative. The assays were performed on patients with falciparum malaria before and after treatment with antimalarial drugs. Before treatment, all 24 patients were positive by all three systems of two-site sandwich IRMAs. Two weeks after treatment, 81.8% (18 of 22) of the patients were positive by microscopic examination, but the IRMA positivity rates were 90.9% (20 of 22), 86.4% (19 of 22), and 81.8% (18 of 22) for MAb-, PAb-MAb-, and PAb-IRMA, respectively. Four weeks after treatment, all 19 patients were negative by microscopic examination, but 52.6% (10 of 19) of the patients were still positive with MAb- and PAb-MAb-IRMA and 31.6% (6 of 19) were positive with PAb-IRMA. Comparison between the three systems of IRMA showed that the MAb-IRMA was superior to the other two systems for three reasons. First, it gave a lower count when tested with blood from healthy individuals. Second, it gave a higher count when tested with blood from patients with falciparum malaria. Third, it gave better correlation with parasitemia when blood from falciparum malaria patients was tested. MAb-IRMA is recommended for use for the detection of low-grade P. falciparum infection.

Adult↗
PubMed1987

Human and primate malarial sera inhibit Fc receptor-mediated phagocytosis.

Sera obtained from humans in P. falciparum-endemic regions and from P. vivax-infected Saimiri sciureus were assayed for their ability to inhibit Fc receptor-mediated phagocytosis. Some sera of humans exposed to P. falciparum from The Gambia, Sudan, and Thailand inhibited ingestion via the Fc receptor by normal human monocytes. In addition, sera from infected monkeys and a high molecular weight fraction of infected monkey serum inhibited ingestion of EIgG by normal monkey spleen macrophages. Generally, inhibition was correlated with higher parasitemia and higher IFA titers.

Adolescent↗
PubMed1987

Human monoclonal anti-Plasmodium falciparum antibodies produced by stable EBV-transformed lymphocytes from patients with falciparum malaria.

Peripheral blood lymphocytes (PBL) from 10 persons living in a malaria endemic area and 18 patients recovered from falciparum malaria were studied, nine of whom were admitted to the Hospital for Tropical Diseases and the remaining nine patients were from Trad District Hospital. PBL were divided into two portions, one of which was transformed directly by EBV in the presence of cyclosporin A to eliminate T cell suppression and the other was pre-incubated before transformation with the extract of ultrasonically disrupted, schizont-enriched P. falciparum parasites from in vitro culture. The products of transformed cells were tested for antibodies against blood stages and sporozoites and cells from positive wells were cloned and propagated. With antigen pre-stimulation, cells from 212 of 317 wells (64.5%) were transformed, and this level of transformation was not significantly different from that in the absence of antigen stimulation in which 193 of 311 wells (62.5%) showed transformation (p greater than 0.05). In contrast, 85 of 212 (40.2%) clones from antigen prestimulated wells secreted antibodies whereas 18 of 193 (9.3%) wells without prior antigen stimulation did (p less than 0.0001). Only 44 of 103 antibody-positive clones were subjected to further analysis, of which 42 had activities against blood stages and two against sporozoites. Based on indirect immunofluorescent reactivities, our anti-blood stage monoclonal antibodies (MABs) were conformed to group I (21 clones), III (11 clones) and V (5 clones) and group VI (5 clones).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Intrathecal immunoglobulin synthesis in cerebral malaria.

Local synthesis of immunoglobulin within the central nervous system has been evaluated in 37 patients with acute cerebral malaria; seven patients were also studied in the convalescent phase. There was evidence in the cerebrospinal fluid (CSF) of 21 patients that intrathecal IgG synthesis occurs in the acute phase. There were raised IgG: albumin ratios in 43% of acute patients. Oligoclonal IgG bands or cathodal IgG was seen in the CSF of 43% of patients tested by polyacrylamide electrophoresis. Only eight out of 37 acute patients (22%) had no evidence of intrathecal IgG synthesis by either method. The serial studies showed that most patients had IgG-CSF abnormalities when tested in convalescence. These studies suggest that an immune stimulus (perhaps malarial antigens or mitogens) may be present in the brain in acute cerebral malaria.

Acute Disease↗
PubMed1987

Immunoprecipitating antibodies against blood stage antigens of Plasmodium falciparum in cerebral and non-cerebral malaria patients.

Immunoprecipitating antibodies were determined in paired sera of 31 patients with cerebral malaria (CM), of whom 14 had complicated cerebral malaria (CCM) and 17 had uncomplicated cerebral malaria (UCCM), 15 single specimens of patients with acute uncomplicated (AM) malaria taken on the day of admission and 8 healthy controls. All but one patient were admitted within the first three days of the onset of fever. More than 20 precipitating bands were observed, of which the predominating molecules were the Mr greater than 200, 180, 157, 135, 130, 115, 103, 96, 91, 73, 71, 61, 49, 45, 43, 41 and 14.3 Kd. In general, there were no significant differences in the positive rates among the AM, CCM and UCCM patients except for the pf135 Kd molecule which was more frequently reactive in UCCM patients than the AM and CCM patients. If immunological naiveness in term of protective immunity is the feature in CM patients, the immunoprecipitation test used is inadequate to demonstrate the fundamental differences in immune responses between CM and AM patients.

Animals↗
PubMed1986

Function of the blood-cerebrospinal fluid barrier in human cerebral malaria: rejection of the permeability hypothesis.

We tested the hypothesis that cerebral malaria is caused by blood-brain barrier inflammation and cerebral edema. In a group of 157 Thai patients with strictly defined cerebral malaria, cerebrospinal fluid (CSF) opening pressures were normal in 79% and were lower in fatal cases than in survivors (means +/- 1 SD, 144 +/- 58 and 167 +/- 51 mm CSF, respectively, P = 0.051). CSF: serum albumin ratios (X 10(3)) in 39 of them were significantly higher than in 61 British controls (medians 8.5 and 5.5, respectively, P = 0.04), but were no higher in 7 fatal cases. In a group of 12 patients this ratio was not significantly higher during coma than after full recovery (means +/- 1 SD, 9.0 +/- 6.2 and 6.7 +/- 4.2, respectively, P greater than 0.1). CSF alpha 2-macroglobulin concentrations were always normal. CSF : serum 77Br- ratios were elevated in 11/19 comatose cases but fell to normal 4 to 9 days later in 11/11 cases. Dexamethasone treatment had no significant effect on bromide partition. The percentage of an intravenously administered dose of 125I-human serum albumin detectable per ml of CSF 6 hr after intravenous injection was 2.4 +/- 1.3 X 10(-5) in 14 comatose patients and 4.4 +/- 4.0 X 10(-5) in 9 of them during convalescence (P greater than 0.1). These results demonstrate that the blood-CSF barrier is essentially intact in patients with cerebral malaria and give no support to the idea that cerebral edema is the cause of coma.

Blood-Brain Barrier↗