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Biomedical subjects

S Tharavanij

Publications and source records attributed to S Tharavanij.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1986

Occurrence of a common epitope in circumsporozoite proteins of Plasmodium falciparum isolated from different areas in Thailand.

Fifteen isolates of P. falciparum sporozoites obtained from patients with acute falciparum malaria from various malaria endemic areas in Thailand were tested for the presence of a common antigenic determinant in their CS protein molecules. SDS-PAGE and Western blot analysis using MAB or human serum antibodies specific to the CS proteins of the parasites revealed a common epitope shared in the CS proteins of all strains of P. falciparum tested. However, the CS proteins exhibited M.W. variation when different strains of the parasites were compared. A similar result was obtained when the human serum antibodies were used. The present study clearly indicated the occurrence of the common epitope in phenotypically different CS proteins among isolates of P. falciparum sporozoites and supported the notion that antigens containing these repetitive epitopes could be used as the candidates for the sporozoite vaccine against P. falciparum infection.

Animals↗
PubMed1986

Influence of circulating malarial antigens on cell mediated immunity in acute Plasmodium falciparum malaria.

In a group of Thai patients with P. falciparum acute malaria, circulating malarial antigens (CMA) were detected in 27/33 cerebral malaria (CM) cases and 31/43 noncerebral cases. Delayed cutaneous responses to phytohemagglutinin and candidin were found frequently negative in patients with CMA, especially in the CM group. Mean in vitro lymphocyte proliferative responses to lectins were lower in the group of patients with CMA. An inhibitory activity on proliferative responses to phytohemagglutinin of lymphocytes from healthy individuals was exerted by sera containing CMA. Data suggest that CMA from P. falciparum may suppress in vivo and in vitro cell mediated immune reactions.

Acute Disease↗
PubMed1986

Cross-sectional seroepidemiological survey of malaria in endemic areas with different activities of malaria control.

A single cross-sectional seroepidemiological survey of malaria antibody was conducted in 1982 in Klang District, Rayong Province in three villages under different phases of malaria control activity to determine whether a single survey could be used to delineate malaria endemicity in Thailand and to compare the usefulness of ELISA and the indirect haemagglutination test (IHA) in the assessment of malaria endemicity. Village 11 was a control area with high infection rate with an annual slide positive rate of 16.3% in 1981. Village 6 was also a control area but was in the late attack phase in which residual insecticide spraying has been ceased since 1976. Village 7 was a consolidation area. Finger-tipped blood was collected from 189, 191 and 132 individuals from villages 11, 6 and 7 respectively, and the plasma tested for anti-P. falciparum antibody with ELISA and IHA. With ELISA, it was shown that the seropositive rate in population of village 11 (84.6%) was significantly higher than those of other two villages (48.9% in village 6 and 28.8% in village 7). After age stratification, it was shown that the differences were observed in every age group except in the greater than or equal to 45 year age group of village 6. With IHA, a significantly higher seropositive rates in population of village 11 was evident when they were compared with the corresponding age groups of 6-14, 15-29 and 30-44 years in village 7, and the age group of less than or equal to 5 year in village 6.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Endotoxin and dengue haemorrhagic fever.

Limulus amoebocyte lysate test (LALT) was used to detect endotoxin-like substances in the plasma of 57 patients with dengue haemorrhagic fever and dengue shock syndrome (DHF/DSS), four patients with dengue fever and 20 control patients with other diseases. The LALT positivity rates in DHF/DSS and dengue fever patients were 43.9 and 25 per cent respectively, whereas all control patients were negative (p less than 0.0025). LALT positivity was highest on 5th and 6th days of admission with positive rates of 46 and 50 per cent respectively whereas the positive rates in those admitted on fourth and seventh days of admission were 29 and 33 per cent respectively. A follow-up in LALT positive patients showed a decline in the positive rates after admission. LALT positivity was observed in 48.8 per cent of DHF/DSS patients with shock and in 26.6 per cent of patients without shock.

Adolescent↗
PubMed1986

A comparative study of four methods for detecting antibody in asymptomatic giardiasis.

Four immunological methods for diagnosis of giardiasis comprising complement fixation (CF) test, indirect hemagglutination (IHA) test, enzyme-linked immuno sorbent assay (ELISA) and lectin immuno test (LIT) were studied. Fifty sera from asymptomatic giardiasis patients, 40 from patients with other diseases and 50 from healthy controls were evaluated. The seropositive rates in asymptomatic giardiasis were 36% for CF, 58% for LIT, 30% for IHA and 72% for ELISA. The seropositive rates in patients with other diseases were 22.5% for CF, 52.5% for LIT, 12.5% for IHA and 67.5% for ELISA. The results suggest that the test of choice for giardiasis was CF with 88% specificity, nevertheless this test showed low sensitivity (36%). Other two tests, ELISA and LIT were more sensitive than CF with percent sensitivity of 72 and 58 respectively, but these two tests had severe disadvantages in being less specific with percentage specificity of 48 and 60 respectively.

Antibodies↗
PubMed1985

A specific S-antigen of Plasmodium falciparum is expressed in a proportion of primary isolates in Brazil, Thailand and Papua New Guinea.

The expression by Plasmodium falciparum of a specific S-antigen has been examined in primary isolates in different regions of the world using a monoclonal antibody that recognizes an epitope within a known repeated amino acid sequence. The epitope was expressed by a small proportion of primary isolates in each of Brazil, Thailand and Papua New Guinea, demonstrating that this S-antigen gene is widespread. The data are consistent with the possibility that the occurrence of P. falciparum strains expressing a particular S-antigen is periodic, related to the duration of immunity against that antigen in a given human population.

Adult↗
PubMed1985

Antibodies against malaria sporozoites in patients with acute uncomplicated malaria and patients with cerebral malaria.

Serum samples from 95 patients with acute uncomplicated falciparum malaria (AM) and 95 patients with cerebral malaria (CM) were tested by the indirect immunofluorescent assay (IFA) for IgG and IgM antibodies against Plasmodium falciparum and P. vivax sporozoites. Forty-six (48%) CM patients were positive for antibodies against P. falciparum sporozoites whereas only 23 (24%) were positive for antibodies against P. vivax sporozoites (P less than 0.002). A similar result was obtained in AM patients. However, CM patients had significantly lower mean IgG anti-sporozoite titer for P. falciparum than did AM patients (P less than 0.05), especially when only anti-sporozoite antibody-positive CM and AM patients were compared (P less than 0.0005), suggesting that CM patients had relatively less exposure and were probably less immune to malaria than were AM patients. The persistence of anti-sporozoite antibodies also was investigated in paired sera taken 63 days apart from 108 patients with acute falciparum malaria. There were significant decreases in the mean antibody titers in the follow-up sera during the period of stay in the malaria-free area. It was proposed that determination of anti-sporozoite antibody be made as a substitute for, or in addition to, anti-blood stage antibody for seroepidemiological study of malaria, especially in the monitoring of the success of the malaria control program.

Acute Disease↗
PubMed1985

Antibodies against circumsporozoite proteins of Plasmodium falciparum induced by natural infection.

Sera from 10 individuals who lived in a malaria endemic area, 10 patients with acute uncomplicated falciparum malaria and 10 patients with cerebral malaria and hyperimmune mouse serum were tested for their reactivities against Plasmodium falciparum sporozoite antigens by Western blot analysis using 125I-labeled staphylococcal protein A as the detecting reagent. These sera were shown by indirect immunofluorescence and/or circumsporozoite precipitation test to have antibodies reacting against the parasites. It was found that all serum antibodies from the three groups of individuals and the mouse serum reacted in a similar pattern with circumsporozoite (CS) proteins of P. falciparum. Ten sera from normal individuals were negative in all reactions. Monoclonal antibody (MAB) specific against CS proteins of the parasites showed that the proteins exhibited as four different molecular weight (MW) polypeptides, i.e., 67,000, 65,000, 60,000, and 58,000 daltons. These CS proteins of P. falciparum were found to be species and stage specific. Radioimmunoprecipitation using 35S-methionine-labeled parasites and sera of individuals from the various categories or MABs gave a similar result. Another protein antigen of P. falciparum sporozoites had a MW of 80,000 daltons. This antigen was not species specific, probably not membrane associated and was present in a minute quantity in the parasite's extract.

Adolescent↗