Human Single-Chain Antibodies That Neutralize Elastolytic Activity of Pseudomonas aeruginosa LasB

LasB (elastase/pseudolysin) is an injurious zinc-metalloprotease secreted by the infecting Pseudomonas aeruginosa. LasB is recognized as the bacterial key virulence factor for establishment of successful infection, acquisition of nutrients, dissemination, tissue invasion, and immune modulation and evasion. LasB digests a variety of the host tissue proteins, extracellular matrices, as well as components of both innate and adaptive immune systems, including immunoglobulins, complement proteins, and cytokines. Thus, this enzyme is an attractive target for disarming the P. aeruginosa. This study generated human single-chain antibodies (HuscFvs) that can neutralize the elastolytic activity of native LasB by using phage display technology. Gene sequences coding HuscFvs (huscfvs) isolated from HuscFv-displaying phage clones that bound to enzymatically active LasB were sub-cloned to expression plasmids for large scale production of the recombinant HuscFvs by the huscfv-plasmid transformed Escherichia coli. HuscFvs of two transformed E. coli clones, i.e., HuscFv-N42 and HuscFv-N45, neutralized the LasB elastolytic activities in vitro. Computer simulation by homology modeling and molecular docking demonstrated that antibodies presumptively formed contact interfaces with the LasB residues critical for the catalytic activity. Although the LasB neutralizing mechanisms await elucidation by laboratory experiments, the HuscFvs should be tested further towards the clinical application as a novel adjunctive therapeutics to mitigate severity of the diseases caused by P. aeruginosa.

Human Single-chain Variable Fragments Neutralize Pseudomonas aeruginosa Quorum Sensing Molecule, 3O-C12-HSL, and Prevent Cells From the HSL-mediated Apoptosis

The quorum sensing (QS) signaling molecule, N-(3-oxododecanoyl)-L-homoserine lactone (3O-C12-HSL), contributes to the pathogenesis of Pseudomonas aeruginosa by regulating expression of the bacterial virulence factors that cause intense inflammation and toxicity in the infected host. As such, the QS molecule is an attractive therapeutic target for direct-acting inhibitors. Several substances, both synthetic and naturally derived products, have shown effectiveness against detrimental 3O-C12-HSL activity. Unfortunately, these compounds are relatively toxic to mammalian cells, which limits their clinical application. In this study, fully human single-chain variable fragments (HuscFvs) that bind to P. aeruginosa haptenic 3O-C12-HSL were generated based on the principle of antibody polyspecificity and molecular mimicry of antigenic molecules. The HuscFvs neutralized 3O-C12-HSL activity and prevented mammalian cells from the HSL-mediated apoptosis, as observed by Annexin V/PI staining assay, sub-G1 arrest population investigation, transmission electron microscopy for ultrastructural morphology of mitochondria, and confocal microscopy for nuclear condensation and DNA fragmentation. Computerized homology modeling and intermolecular docking predicted that the effective HuscFvs interacted with several regions of the bacterially derived ligand that possibly conferred neutralizing activity. The effective HuscFvs should be tested further in vitro on P. aeruginosa phenotypes as well as in vivo as a sole or adjunctive therapeutic agent against P. aeruginosa infections, especially in antibiotic-resistant cases.

Altered proteome of a Burkholderia pseudomallei mutant defective in short-chain dehydrogenase affects cell adhesion, biofilm formation and heat stress tolerance

Burkholderia pseudomallei is a Gram-negative bacillus that causes melioidosis and is recognized as an important public health problem in southeast Asia and northeast Australia. The treatment of B. pseudomallei infection is hampered by resistance to a wide range of antimicrobial agents and no vaccine is currently available. At present, the underlying mechanisms of B. pseudomallei pathogenesis are poorly understood. In our previous study, we reported that a B. pseudomallei short-chain dehydrogenase (SDO; BPSS2242) mutant constructed by deletion mutagenesis showed reduced B. pseudomallei invasion and initial intracellular survival. This indicated that SDO is associated with the pathogenesis of melioidosis. In the present study, the role of B. pseudomallei SDO was further investigated using the SDO deletion mutant by a proteomic approach. The protein profiles of the SDO mutant and wild-type K96243 were investigated through gel-based proteomic analysis. Quantitative intensity analysis of three individual cultures of the B. pseudomallei SDO mutant revealed significant down-regulation of five protein spots compared with the wild-type. Q-TOF MS/MS identified the protein spots as a glutamate/aspartate ABC transporter, prolyl-tRNA synthetase, Hsp70 family protein, quinone oxidoreductase and a putative carboxypeptidase. Functional assays were performed to investigate the role of these differentially expressed proteins in adhesion to host cells, biofilm induction and survival under heat stress conditions. The SDO deletion mutant showed a decreased ability to adhere to host cells. Moreover, biofilm formation and the survival rate of bacteria under heat stress conditions were also reduced in the mutant strain. Our findings provide insight into the role of SDO in the survival and pathogenesis of B. pseudomallei at the molecular level, which may be applied to the prevention and control of B. pseudomallei infection.

Monoclonal antibodies to LipL32 protect against heterologous Leptospira spp. challenge

A non-culture-based leptospirosis vaccine that cross-protects against infection caused by heterologous Leptospira spp. should replace the currently available products, which are qualitatively and quantitatively inadequate. With that in mind, two murine hybridomas secreting monoclonal antibodies (MAb) binding only to homogenates of pathogenic Leptospira spp., and not of the saprophytic L. biflexa, serogroup Patoc, serovar Patoc, were produced. The MAbs of both clones neutralized Leptospira-mediated human red blood cell lysis in vitro and rescued hamsters from lethal infection with heterologous Leptospira spp. The orthologous Leptospira spp. protein carrying the MAb epitope(s) was identified by two-dimensional gel electrophoresis (2DE)-based proteomics and database search. The epitopes of the MAbs were located on the major outer membrane protein LipL32 of the pathogenic Leptospira spp. The MAbs in their humanized version are potential leptospirosis immunotherapeutics. They are also suitable as detection reagents in antigen-based assays for the rapid diagnosis of leptospirosis. Recombinant LipL32 is a good candidate for a broad spectrum, non-culture-based leptospirosis vaccine.

Murine monoclonal antibodies neutralizing the cytotoxic activity of diphtheria toxin

In this study, murine monoclonal antibodies that specifically bound to the A and B subunits of diphtheria toxin (DT) were produced by conventional hybridoma technology using the spleens of BALB/c mice immunized with diphtheria DTP vaccine and CRM197. Monoclonal antibodies specific to the A subunit, i.e. clone AC5, as well as those specific to the B subunit, i.e. clone BB7, could neutralize the DT-mediated cytotoxicity to Vero cells in microcultures. The DT neutralizing mechanisms have yet to be determined. The MAbBB7 is hypothesized to either interfere with the DT receptor binding or with the pore forming function of the T domain of the B subunit. The MAbAC5 could neutralize the DT mediated cytotoxicity when mixed with the DT before adding to the Vero cell culture thus suggesting that the antibody interfered with the translocation of the A subunit. The A subunit-antibody complex might be too large to pass through the membrane channel formed by the T domain and thus prevent the accessibility of the A subunit to the cytosolic target. It is also possible that the MAb AC5 blocked the enzymatic active site of the enzyme catalytic subunit. While further experiments are needed to localize the epitopes of the two MAbs on the holo-DT in order to reveal the DT neutralizing mechanisms, both MAbs in their humanized forms have a high potential as human therapeutic antibodies for diphtheria.

Molecular typing of Vibrio cholerae O1 isolates from Thailand by pulsed-field gel electrophoresis

The aim of the present study was to genotypically characterize Vibrio cholerae strains isolated from cholera patients in various provinces of Thailand. Two hundred and forty V. cholerae O1 strains, isolated from patients with cholera during two outbreaks, i.e. March 1999-April 2000 and December 2001-February 2002, in Thailand, were genotypically characterized by NotI digestion and pulsed-field gel electrophoresis (PFGE). In total, 17 PFGE banding patterns were found and grouped into four Dice-coefficient clusters (PF-I to PF-IV). The patterns of V. cholerae O1, El Tor reference strains from Australia, Peru, Romania, and the United States were different from the patterns of reference isolates from Asian countries, such as Bangladesh, India, and Thailand, indicating a close genetic relationship or clonal origin of the isolates in the same geographical region. The Asian reference strains, regardless of their biotypes and serogroups (classical O1, El Tor O1, O139, or O151), showed a genetic resemblance, but had different patterns from the strains collected during the two outbreaks in Thailand. Of 200 Ogawa strains collected during the first outbreak in Thailand, two patterns (clones)--PF-I and PF-II--predominated, while other isolates caused sporadic cases and were grouped together as pattern PF-III. PF-II also predominated during the second outbreak, but none of the 40 isolates (39 Inaba and 1 Ogawa) of the second outbreak had the pattern PF-I; a minority showed a new pattern--PF-IV, and others caused single cases, but were not groupable. In summary, this study documented the sustained appearance of the pathogenic V. cholerae O1 clone PF-II, the disappearance of clones PF-I and PF-III, and the emergence of new pathogenic clones during the two outbreaks of cholera. Data of the study on molecular characteristics of indigenous V. cholerae clinical isolates have public-health implications, not only for epidemic tracing of existing strains but also for the recognition of strains with new genotypes that may emerge in the future.

Virulence genes of clinical Vibrio cholerae O1 isolates in Thailand and their ribotypes

OBJECTIVE

To determine virulence associated-genes and ribotypes of Vibrio cholerae epidemic strains isolated from cholera patients in Thailand.

METHOD

A total of 240 V. cholerae El Tor, O1 strains, isolated from patients with cholera in Thailand during two different periods, i.e. 1999-2000 (200 strains; 193 Ogawa and 7 Inaba) and 2001-2002 (40 strains; all Inaba), were analyzed for the presence of virulence genes, namely ctxA, ctxB, zot, ace, toxR, tcpA, hlyA, nanH and ninT by PCR. For ribotyping, genomic DNA segments of the 240 strains and 10 reference V. cholerae strains isolated before 1999 from Thailand and elsewhere were digested with BglI endonuclease, subjected to a 0.8% agarose gel electrophoresis, blotted onto a nylon membrane and probed with enzyme-labeled Escherichia coli rRNA. The DNA bands were visualized by autoradiography.

RESULTS

Genes encoding the A and B subunits of CT, Zot, Ace, ToxR, TcpA, HlyA, NanH and NinT could be amplified from all of the 10 V. cholerae O1 reference strains and from 239 of the 240 studied isolates. One Inaba isolate of 2001-2002 gave only amplicons of toxR and hlyA. For ribotyping, the 10 reference strains revealed six different patterns designated A to F. None of the 240 strains isolated in Thailand during the two periods had the A-C, E and F ribotypes. The isolates of 1999-2000 revealed ribotype D and three other ribotypes, designated G, H and I. The majority of the isolates of 2001-2002 showed ribotype G. The remaining showed other new ribotypes, J and K.

CONCLUSIONS

The clinical V. cholerae isolates of two epidemics from Thailand showed a sustained appearance of one epidemic V. cholerae clone, and a constant, but gradual and minor change in the genetic constituent of the other V. cholerae strains as indicated by the change of the ribotypes of the strains in the two study periods. Moreover, we found that a V. cholerae strain which cannot produce CT, Zot, Ace, TcpA, NanH and NinT can still cause symptomatic cholera.

Diagnosis of human leptospirosis by monoclonal antibody-based antigen detection in urine

Hybridomas secreting specific monoclonal antibodies (MAb) to all members of the genus Leptospira (clone LF9) and those that are specific only to the pathogenic species (clones LD5 and LE1) were produced. MAb LF9, which was immunoglobulin G1 (IgG1), reacted to a 38-kDa component of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated whole-cell lysates of all Leptospira spp., while MAb LD5 and MAb LE1, which were IgG1 and IgG2a, respectively, reacted to the 35- to 36-kDa components of all serogroups of the pathogenic species of LEPTOSPIRA: The MAb LD5 was used in a dot blot-enzyme-linked immunosorbent assay (dot-ELISA) for detecting Leptospira antigen in urine samples serially collected from two groups of patients diagnosed with leptospirosis, i.e., 36 clinically diagnosed patients and 25 Leptospira culture confirmed patients. Their serum samples were tested serologically by IgM Dipstick assay, indirect immunofluorescence assay (IFA), and/or microscopic agglutination test (MAT). Urine samples of 26 patients diagnosed with other illnesses and 120 healthy individuals served as controls. For the first group of patients, who had been ill for an average of 3.4 days before hospitalization, the IgM Dipstick test, IFA, and MAT were positive for 69.4, 70.0, and 85.7% of patients, while the Leptospira antigenuria tested by the MAb-based dot-ELISA was positive for 75.0, 88.9, 97.2, 97.2, and 100% of patients on days 1, 2, 3, 7, and 14 of hospitalization, respectively. All but 1 of 11 patients whose serum samples collected on the first day of hospitalization were IgM seronegative, were positive by urine antigen test on day 1. This is strong evidence that detection of antigen in urine can provide diagnostic information that could be useful in directing early therapeutic intervention. The MAT was positive in 10 of 12 patients (83.3%) of the 25 culture-positive Leptospira patients who had been ill for an average of 5.04 days before hospitalization, and the Leptospira antigen was found in 64.0, 84.0, 96.0, 100, 100, 100, and 100% of the patients' urine samples collected on days 1, 2, 3, 4, 5, 6, and 7 of hospitalization, respectively. Leptospira antigenuria was found in 3 of the 26 patients diagnosed with other illnesses and 1 of the 120 healthy controls. The reasons for this positivity are discussed. The detection of antigen in urine by the monoclonal antibody-based dot-ELISA has high potential for rapid, sensitive, and specific diagnosis of leptospirosis at a low cost.

Clonal dissemination of Vibrio parahaemolyticus displaying similar DNA fingerprint but belonging to two different serovars (O3:K6 and O4:K68) in Thailand and India

Active surveillance of Vibrio parahaemolyticus infection among hospitalized patients in Calcutta, India, showed the appearance of the O4:K68 serovar for the first time in March 1998 alongside the continued predominant incidence of the O3:K6 serovar. Strains belonging to both these serovars have been reported to possess pandemic potential. The genomes of O3:K6 and O4:K68 strains and for comparison, non-O3:K6 and non-O4:K68 strains isolated from two different countries, India and Thailand, were examined by different molecular techniques to determine their relatedness. The O3:K6 and O4:K68 strains from Calcutta and Bangkok carried the tdh gene but not the trh gene. Characterization of representative strains of these two serovars by ribotyping and by arbitrarily primed-polymerase chain reaction (AP-PCR) showed that the isolates had identical ribotype and DNA fingerprint. Pulsed-field gel electrophoresis (PFGE) performed with the same set of strains yielded nearly similar restriction fragment length polymorphism (RFLP) patterns for the O3:K6 and O4:K68 isolates from Calcutta and Thailand. Phylogenetic analysis of the NotI RFLP showed that the O3:K6 and O4:K68 strains formed a cluster with 78-91% similarity thus indicating close genetic relationship between the two different serovars isolated during the same time-frame but from widely separated geographical regions. The non-O3:K6 and non-O4:K68, in contrast, showed different ribotype, AP-PCR and PFGE patterns.

Rapid diagnosis of cholera caused by Vibrio cholerae O139

Hybridomas secreting specific monoclonal antibodies (MAbs) to Vibrio cholerae serogroup O139 were produced. Six monoclones (hybridomas) secreting MAbs specific only to lipopolysaccharide of V. cholerae O139 strains and which did not cross-react to 137 strains of other enteric microorganisms were obtained. These clones were designated 12F5-G11, 12F5-G2, 15F5-H5, 5B9-F8, 14C9-D2, and 6D2-D8. The immunoglobulin (Ig) heavy chain isotypes secreted by these clones were IgG2b, IgG2b, IgG2b, IgM, IgG2b, and IgG3, respectively. Clone 12F5-G11 was selected for mass production of MAb, which was used as a detection reagent in the antigen detection assay for diagnosis of cholera caused by V. cholerae O139, and this assay was compared to the conventional bacterial isolation method. Five batches of rectal swab cultures in alkaline-peptone water were collected from 6,497 patients with watery diarrhea. These were 6,310 patients admitted to Bamrasnaradura Infectious Diseases Hospital, 16 patients from Krung Thon Hospital, 78 patients from Bangkok Children's Hospital, 19 patients from Karen refugee camps, and 74 Indian patients from the National Institute of Cholera and Enteric Diseases, Calcutta, India. The V. cholerae O139 isolations from the rectal swab cultures and the antigen detection assays (i.e., the MAb-based dot-blot ELISA) were performed by different persons of different laboratories, and the results were revealed after all specimens had been tested. Of the 6,497 samples tested, the dot-blot ELISA correctly identified 42 of 42 V. cholerae O139-positive samples and gave a result of positive for three samples which were culture negative for V. cholerae O139. The diagnostic sensitivity, specificity, and efficacy of the dot-blot ELISA were 100, 99.95, and 99.26%, respectively. The ELISA is easy to perform and relatively inexpensive. It can test multiple samples at a single time, does not require special equipment, and does not produce great quantities of contaminated waste. Most of all, it reduces the diagnostic time from at least 2 days for the bacterial isolation to less than 90 min. The assay is recommended as a rapid screening test of cholera cases caused by V. cholerae O139.

Diagnosis of typhoid fever by detection of Salmonella typhi antigen in urine

A monoclonal antibody specific for group D Salmonella antigen 9 was used in an indirect enzyme-linked immunosorbent assay (ELISA) for detecting the antigen in urine specimens collected from patients with clinical typhoid fever in Jakarta, Indonesia. The ELISA had a sensitivity of 95% in identifying patients in whom Salmonella typhi was isolated from hemocultures, 73% in patients in whom S. typhi was isolated from stool specimens, and 40% in patients in whom the organism was isolated from bone marrow cultures. Among patients in whom S. typhi was isolated from blood cultures, the ELISA had a sensitivity of 65% when a single urine specimen was examined and 95% when serially collected urine specimens were examined. A dot blot immunoassay performed on a nitrocellulose filter in parallel had a sensitivity of 85%, versus 83% for the plate ELISA in which S. typhi was isolated from blood, bone marrow, and/or stool specimens. Since S. typhi antigen is intermittently excreted in the urine of patients with typhoid fever, serially collected urine from patients with typhoid should be tested for antigen 9.

Monoclonal antibody to a diagnostic Mr 24,000 antigen of Gnathostoma spinigerum

Crude water extract (CA) was prepared from the advanced third-stage larvae of Gnathostoma spinigerum collected from livers of naturally infected eels. The extract was partially purified by chromatofocussing column chromatography and the fraction which contained specific antigen of G. spinigerum which was an Mr 24,000 glycoprotein was used to immunize five Balb/c mice for preparing immune splenocytes. Spleen cells were collected from one mouse which showed high serum titre by indirect enzyme-linked immunosorbent assay and contained specific antibody to the Mr 24,000 antigen as checked by Western blot analysis. The spleen cells were fused with myeloma Sp2/0 cells at a ratio of 10 spleen cells per one myeloma cell using polyethylene glycol 3350 as a fusogen. Thirteen out of 174 growing polyclones (7.5%) produced antibodies to the partially purified CA fraction. Among them, two polyclones produced antibody directed to the Mr 24,000 protein. These two polyclones were subjected to monocloning by limiting dilution and a monoclone GN6/24 which produced monoclonal antibody to the specific Mr 24,000 protein of G. spinigerum was obtained.

Detection with monoclonal antibody of Salmonella typhi antigen 9 in specimens from patients

Monoclonal antibodies were raised against Barber antigen (Ba) of Salmonella typhi 0901. Antibodies produced to antigen 9 of group D salmonellae were used in double- and triple-sandwich antibody enzyme-linked immunosorbent assays (ELISAs) for detecting antigen 9 in urine and plasma specimens from three groups of patients and 49 controls. The triple-antibody ELISA detected the antigen in urine samples from 11 of 18 (65%) patients with hemoculture-proven typhoid (group 1) and 12 of 39 (31%) patients with clinical features compatible with typhoid but whose hemocultures were negative (group 2). This ELISA was negative in three patients from whom Salmonella paratyphi A, Escherichia coli, and Klebsiella pneumoniae (group 3) were isolated by hemoculture and in all healthy controls. The double-antibody sandwich ELISA was positive in 41 and 15% of urine samples from patients in groups 1 and 2, respectively, and was negative with samples from two patients from group 3 and all controls. The sensitivity and specificity compared with those for healthy controls were 65 and 100%, respectively, for the triple-antibody ELISA. Although as little as 7.8 ng of homologous lipopolysaccharide could be detected, background in clinical specimens prevented accurate interpretation of the detection of this antigen in serum. Results were best with urine specimens.

Simple serological tests for detecting classical heat labile enterotoxin (LT-I) of Escherichia coli

Diarrhoea caused by enterotoxigenic Escherichia coli (ETEC) remains a problem in Southeast Asia. At present, no routine laboratories as yet are available for ETEC detection. In this study, attempts were made to produce reagents for use in simple serological tests for detecting LT. The serological methods were the Biken, the staphylococcal coagglutination and the reverse passive hemagglutination tests. For the Biken test, medium was prepared locally by mixing constituents as described previously by Honda et al., (1981). Anti-CT-B subunit was prepared by immunizing a rabbit with commercial CT-B subunits (Sigma). Other chemical reagents e.g. colistin, lincomycin etc. were obtained from the local supplies. Using the locally made reagents to detect LT from 100 WHO reference strains of E. coli by the Biken test, it was found that the test had 100%, 92%, 96%, 100% and 92.5% of specificity, sensitivity, accuracy, positive predictive value and negative predictive value, respectively. Protein A rich Staphylococcus aureus from the stock culture of the Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University were grown in suitable medium i.e. blood agar containing lincomycin (BA-Lin). Suitable amount of the rabbit anti CT-B subunit (0.1 ml) was used to sensitize each ml of the formalinized, heat-fixed bacteria. The sensitized bacteria were used for detecting LT in the lysates of the 100 E. coli reference strains. The lysates were prepared by growing the E. coli strains on BA-Lin medium for 8 hours, then a loopful of each strain was inoculated into colistin solution (20,000 unit/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Oral vaccine against cholera prepared from Vibrio cholerae antigen(s)

Albino rats aged 7-8 weeks old purchased from the National Laboratory Animal Centre, Salaya, Nakhon Pathom, were found to be a good animal model for the study on immunogenicity of V. cholerae antigens. Seventy-two rats were fasted for 15 hours before feeding each one with 1 ml of 5% NaHCO3 to reduce gastric acidity prior to immunization. They were divided into 9 groups of 8 rats and immunized orally with 2 ml, each, of the V. cholerae antigens dissolved or suspended in Cassamino acid as follows: group 1 (control): Cassamino acid (Ca) alone; group 2 (control): 2.5% formalinized sheep red blood cells (F-SRBC); group 3: 1,000 micrograms of lipopolysaccharide (LPS); group 4: 100 micrograms of procholeragenoid (P); group 5: 80 haemagglutinating units of cell-bound haemagglutinin (CHA) adsorbed onto the surface of F-SRBC (CH-SRBC); group 6: 500 micrograms of LPS + 50 micrograms of P; group 7: CH-SRBC + 50 micrograms of P; group 8: combined vaccine formula 1 consisted of 500 micrograms of LPS, CH-SRBC and 50 micrograms of P and group 9: combined vaccine formula 2 consisted of 1,000 micrograms of LPS, CH-SRBC and 100 micrograms of P. The immunization was repeated once more 14 days later. Five days, thereafter, the rats were killed and their jejuni were removed for cryostat sectioning. Antibody producing cells against LPS (anti-LPS cells), P (anti-CT cells) and CHA (anti-CHA cells) in the intestinal lamina propria were enumerated by double antibody sandwich method of immunofluorescence using pure LPS, cholera toxin (CT) and pure CHA as the antigens in the assay, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies against Vibrio cholerae lipopolysaccharide, cell-bound haemagglutinin and toxin in the intestinal fluid during convalescence

Specific antibodies to V. cholerae lipopolysaccharide (LPS), cell-bound haemagglutinin (CHA) and toxin (CT) in the intestinal lavages of healthy Thais and Thai cholera patients during the convalescence period were determined by enzyme-linked immunosorbent assay. Only IgM and IgA specific antibodies were detectable in the specimens. All of the persons who were just recovered from cholera had IgA anti-CT and IgA anti-LPS and 82.4% had IgA anti-CHA. The IgA anti-CT, anti-LPS and anti-CHA were detected also in the gut fluids of 70.6%, 94.1% and 88.2%, respectively, of the healthy controls. The mean levels of the IgA antibodies of all specificities between the two groups of individuals were not different. However, the IgM anti-CT and IgM anti-LPS of the cholera patients increased during the convalescence period. The levels, therefore, were significantly higher than those of the controls. The ratios of IgA anti-CT: IgM anti-CT and IgA anti-LPS: IgM anti-LPS among the patients were 2.93:1 and 2.02:1, respectively while those of the controls were 10:1 and 34:1, respectively. IgA antibodies predominated in the lavages of both groups of the individuals.

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)

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)

Factors contributing to the development of cerebral malaria. I. Humoral immune responses

Humoral immune responses to malaria were studied in 100 patients with cerebral malaria of whom 53 had added complications, 108 patients with acute malaria, and 100 blood donors. The methods employed were indirect hemagglutination (IHA), indirect fluorescent antibody (IFA), enzyme-linked immunosorbent assay (ELISA), and parasite growth inhibition (PGI) tests. Patients with cerebral malaria, especially those with complications, had histories of fewer attacks of malaria in the previous 5 years than did those with acute malaria, suggesting that the cerebral malaria patients were less immune. The combined cerebral malaria group (complicated and uncomplicated) did not show defective humoral immune responses, since the initial seronegative rate and the mean initial IHA and IFA antibody titers were not significantly different from those of acute malaria patients and the mean initial ELISA titer was even higher than that of the acute malaria group. Reduced humoral responses were found only in complicated cerebral malaria patients, as their mean initial IHA titer was lower and their IHA seronegative rate was higher than those in acute malaria patients and in the uncomplicated cerebral malaria group. The combined cerebral malaria group had greater PGI activity than that of acute malaria patients, but this increased activity was entirely due to the higher results obtained in the complicated cerebral malaria group. The increased PGI activity returned to normal after recovery. An IgG preparation from seven of eight of these sera failed to exert the growth inhibition effect. Factors other than IgG were therefore responsible for the inhibition of parasite growth.

Comparison of various serological test results using antigens from different strains of Plasmodium falciparum

Suitability of different strains of Plasmodium falciparum grown continuously in vitro was compared using the indirect haemagglutination (IHA) the indirect immunofluorescent (IFA) tests and ELISA. In the tests employing soluble antigens (IHA and ELISA), there was a significant higher mean log titer of the same sera tested against different strains. Ranking of the strains in term of sensitivity for the detection of malaria antibody in people in the endemic area were G-112 = SO = CC greater than SU greater than PS in the IHA test and G-112 = SO greater than CC greater than SU greater than PS in the ELISA. The difference in the mean log titers appear to relate neither to the geographical location not the isoenzyme markers tested. There was also an apparent correlation between the results of the IHA and the IFA test but not between these two tests and ELISA.