Serum Enzyme-linked Immunosorbent Assay Research Articles

The contribution of specific immunoglobulin M antibodies to the diagnosis of Helicobacter pylori infection in children

To evaluate the diagnostic value of specific immunoglobulins G and M in the detection of Helicobacter pylori infection. Sera from 68 H. pylori-infected children and 35 H. pylori-negative children (aged 1-15 years) were examined using recent-generation serum enzyme-linked immunosorbent assay (ELISA) tests (Malakit Helicobacter pylori series; Biolab, Limal, Belgium). All of the investigated children had positive values for immunoglobulin G antibodies. However, anti-H. pylori-specific immunoglobulin M could be detected only in 19 (27.9%) of the 68 children. When compared with the 13C-urea breath test, these findings represent sensitivity, specificity and positive and negative predictive values of 27.9, 100, 100 and 41.7%, respectively, for the serum ELISA test for the detection of H. pylori-specific immunoglobulin M compared with 100.0, 97.2, 98.5 and 100.0%, respectively, for the Malakit for the detection of specific immunoglobulin G antibodies. Although H. pylori-specific immunoglobulin G has been established as a reliable indicator of active H. pylori infection, using the Malakit for the detection of H. pylori-specific immunoglobulin M does not seem to be of major value in the diagnosis of H. pylori infection in children.

Validity of serology for American Trypanosomiasis with eluates from filter paper

This study evaluates whether blood collected on filter paper kept at 4 degrees C and tested at different intervals of time (1, 7, 15, 30 and 60 days after collection) would present similar results when compared to the serum samples and whether the type of filter paper influences the results. Eluates from filter paper samples were tested for Trypanosoma cruzi antibodies using indirect immunofluorescence antibody test (IFAT), indirect haemagglutination (IHA) and enzyme-linked immunosorbent assay (ELISA) as reference, the antibody titer in sera. Analysis of data showed that results obtained with IFAT, IHA (cut off point = 1:40) and ELISA in sera had similar sensitivity and good concordance among reactions. The use of a multiple linear regression model indicated that titer fall in eluates occurs up to the 7th day after the collection, and it is more marked for samples with lower antibodies titers. However, no significant differences were observed by IFAT, IHA (cut off point = 1:20) and ELISA in the proportion of positive reactions between sera and eluates. The results also showed that Melitta, Klabin or Whatman (reference) filter papers could be indicated for surveys, since they have shown similar capacity of maintenance of anti-T. cruzi immunoglobulins.

Methodologic problems in establishing normal values for IgG subclass concentrations in a pediatric population; comparison of radial immunodiffusion and ELISA methods

The aim of this study was to establish an enzyme-linked immunosorbent assay (ELISA) to measure IgG subclasses by means of monoclonal antibodies. The distribution of IgG subclass protein concentrations in sera from 227 healthy Danish children and 90 adults was measured. Furthermore, this newly established ELISA was compared with different assay systems for determination of IgG subclasses: two radial immunodiffusion methods (RID), one using polyclonal and one using monoclonal antibodies, as well as a commercially available ELISA kit. There was good agreement of results obtained by the different methods of measuring IgG3 and IgG4 concentrations. There was good correlation between results obtained by both RID methods. Despite good correlation between the assays, the ELISA kit showed higher levels of IgG1 in all investigated sera, and the ELISA kit showed no correlation with the other methods, when IgG2 was measured. Analysis of the normal ranges measured by ELISA developed in our laboratory and by RID with polyclonal antibodies showed that the levels obtained by RID were higher than those obtained by our ELISA in sera with low levels of both IgG1 and IgG2, and lower in sera with high concentrations of these two immunoglobulins. Our results emphasize the importance of establishing age-related normal limits for any novel assay measuring IgG subclass concentrations.

Immunoglobulin G antibody responses to polyvalent pneumococcal vaccine in children in the highlands of Papua New Guinea.

The immunoglobulin G (IgG) antibody responses to a pneumococcal polysaccharide vaccine were examined for 480 children aged 3 months to 5 years and living in Tari, Southern Highlands Province, Papua New Guinea. Antipneumococcal IgG to the seven serotypes most frequently causing invasive disease (types 2, 5, 6B, 7F, 14, 19F, and 23F) was measured by an enzyme-linked immunosorbent assay in serum collected before vaccination and 1 and 6 months after vaccination. Prevaccination antibody levels fell rapidly after 3 months of age and remained low throughout the first 2 years of life. One month after vaccination, geometric mean titers of antipneumococcal IgG to serotypes 2, 7F, 23F, and 5 were at least twice those of antibodies in nonvaccinated children of the same age from the ages of 5, 6, 9, and 12 months onwards, respectively; postvaccination antibody responses to serotypes 6B, 14, and 19F rose gradually during the second year of life. Elevated antibody titers to serotypes 2 and 7F were maintained 6 months after vaccination. Thus, young Papua New Guinean children are capable of mounting a good immune response to some pneumococcal capsular polysaccharides from a young age, and the antibody responses to capsular polysaccharides are consistent with studies in developed countries. However, in Papua New Guinea, the serogroup distribution of invasive disease matches the immunogenic components of the pneumococcal polysaccharide vaccine more closely than in developed countries, a fact which helps to explain the results of controlled trials in Papua New Guinea, in which this vaccine prevented death and severe morbidity from pneumonia in young children.

Evaluation of Urothelial Tamm-Horsfall Protein and Serum Antibody as a Potential Diagnostic Marker for Interstitial Cystitis

Demonstration of adherence of Tamm-Horsfall protein to bladder epithelium has been suggested as a potential diagnostic test for interstitial cystitis. Bladder specimens from 18 interstitial cystitis patients were evaluated by indirect immunoperoxidase techniques using a Tamm-Horsfall protein specific monoclonal antibody to determine the diagnostic value of the staining results. The study population consisted of 7 severely diseased patients who required cystectomy with urinary diversion and 11 other patients meeting National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases criteria for interstitial cystitis. We were unable to detect intraepithelial or surface-bound Tamm-Horsfall protein in any of the biopsy tissues. Human kidney tissue, similarly fixed and processed, consistently demonstrated Tamm-Horsfall protein staining of the kidney tubules. The monoclonal antibody also reacted on Western blots against urinary Tamm-Horsfall protein. Although antibody (α-Tamm-Horsfall protein) reactivity was measured by enzyme-linked immunosorbent assay in sera from interstitial cystitis patients, the titers did not differ statistically from those measured in sera from those without interstitial cystitis. Together, these results make it unlikely that immunohistochemical detection of Tamm-Horsfall protein will have diagnostic value in interstitial cystitis. Whether Tamm-Horsfall protein has a role in the pathogenic processes involved in this disease is not yet known. These findings do not eliminate the possibility that some interstitial cystitis patients will have abnormalities associated with the biochemical and physiological functions of Tamm-Horsfall protein.

Development of mucosal protection against the heat-stable enterotoxin (ST) of Escherichia coli by oral immunization with a genetic fusion delivered by a bacterial vector

An LT-B-ST (LT-B/ST) fusion peptide was constructed by genetically joining the 5' terminus of a synthetic gene coding for the heat-stable enterotoxin (ST) of Escherichia coli to the 3' terminus of the gene coding for the binding subunit of the heat-labile enterotoxin (LT-B) of E. coli. An eight-amino-acid, proline-containing linker was included between the LT-B and ST moieties. An aroA mutant of Salmonella dublin transformed with a plasmid carrying this genetic construct was shown to express a fusion peptide with antigenic determinants of both LT-B and ST. Mice were immunized orally with this strain or with a control strain expressing just LT-B from the same plasmid. Sera and mucosal secretions were obtained and analyzed for the presence of serum immunoglobulin G and mucosal immunoglobulin A that were able to recognize LT-B and ST by enzyme-linked immunosorbent assay (ELISA) and, more importantly, were able to neutralize native ST in the suckling mouse assay. Sera and mucosal secretions from animals immunized with the strain expressing the LT-B/ST fusion exhibited detectable ELISA reactivity against LT-B but not against native ST. However, even in the absence of detectable ELISA reactivity, both sera and mucosal secretions from these animals were able to neutralize the biological activity of native ST in the suckling mouse assay. These findings are important because they demonstrate the development of mucosal protection against ST by oral immunization with a genetic fusion delivered by a bacterial vector.

Increased levels of circulating intercellular adhesion molecule 1 in the sera of patients with rheumatoid arthritis.

We sought to assess whether circulating levels of intercellular adhesion molecule 1 (ICAM-1) in patients with rheumatoid arthritis (RA) are elevated and correlate with clinical measures of disease activity and whether this ICAM-1 originates from the synovium. Circulating ICAM-1 (cICAM-1) levels were determined by sandwich enzyme-linked immunosorbent assay of serum from 61 RA, 18 osteoarthritis (OA), and 11 inflammatory arthritis (IA) patients. In addition, paired serum and synovial fluid samples were collected from 17 RA, 9 OA, and 4 IA patients. The stability of cICAM-1 was assessed by overnight incubation at 37 degrees C. Finally, the potential degradative effects of synovial fluid proteases were assessed by incubation of recombinant soluble ICAM-1 with patient synovial fluid. RA sera contained significantly greater (P < 0.001) levels of cICAM-1 compared with RA synovial fluid and compared with sera or synovial fluid from the OA and IA patients. Circulating ICAM-1 levels were unaffected by overnight incubation at 37 degrees C and were unaffected by exposure to RA, OA, or IA synovial fluid. Serum levels of cICAM-1 demonstrated a weak, but significant (P < 0.05) correlation with the joint score and erythrocyte sedimentation rate in 25 RA patients treated with nonsteroidal antiinflammatory drugs. The greatest elevations of cICAM-1 were seen in RA patient sera. In both RA and OA, synovial fluid cICAM-1 levels were consistently lower than serum levels, suggesting that cICAM-1 did not originate in the synovium. Because the production of cICAM-1 can be increased by cytokines (e.g., interleukin-1, tumor necrosis factor alpha), elevated levels of circulating ICAM-1 in RA may be reflective of systemic exposure to elevated cytokine levels.

Production of polyclonal antibodies to the trichothecene mycotoxin 4,15-diacetylnivalenol with the carrier-adjuvant cholera toxin.

The trichothecene mycotoxin 4,15-diacetylnivalenol (DNIV) was conjugated to cholera toxin (DNIV-CT) for use as an immunogen and as an adjuvant for specific antibody production. Repeated intravenous injection of 7.5 micrograms of the conjugate was effective at generating specific antibodies to DNIV in rabbits as determined by enzyme-linked immunosorbent assay (ELISA). When small amounts (1 to 10 micrograms per animal) of DNIV-CT were used to immunize mice, polyclonal antibodies were observed as early as 4 weeks of immunization. The relative affinity of the antibodies to DNIV increased with the immunogen dose in mice. Antibodies were not detectable in either rabbits or mice that were injected with DNIV conjugated to the carrier protein bovine serum albumin or when DNIV-CT was blocked with glutaraldehyde. Competitive ELISA of mouse and rabbit serum revealed that the antibodies were most specific for DNIV but reacted to a small extent with fusarenone-X, deoxynivalenol, and nivalenol. No reactivity was observed with 3- or 15-acetyldeoxynivalenol. The results suggest that specific polyclonal antibodies can be prepared against a trichothecene when CT is used as an adjuvant and carrier protein. DNIV antibodies will be useful for monitoring the compound in food in conjunction with other trichothecene antibodies, detection of DNIV-producing cultures, and investigation of 8-ketotrichothecene biosynthesis.

Purification of Coxiella burnetii antigen by gel-chromatography for use in enzyme-linked immunosorbent assay (ELISA).

Cell wall antigens from Coxiella burnetti were extracted by heat, ultrasonication, phenol, SDS or sodium deoxycholate. These antigens were subsequently purified by gel-chromatography yielding molecular weights of 700 and 270 KD. Using gel-chromatographical purification of antigens extracted by heat, ultrasonication or phenol Coxiella antigens nearly devoid of contaminations could be obtained. Of these highly purified antigens heat extracted antigen was treated with proteases, lysozyme or metaperiodate exemplarily. These treatments did neither destroy nor change its antigenic activity, except for the treatment with metaperiodate reducing the antigenic activity significantly. In further experiments heat extracted and gel-chromatographically purified Coxiella antigen was used for testing bovine sera in ELISA.

Comparison of saliva and serum for HIV surveillance in developing countries

Saliva has been proposed as a non-invasive alternative to serum for HIV antibody testing. In a field study in Myanmar (formerly Burma), we evaluated such an alternative to identify the frequency of HIV infection in a surveillance programme of high-risk and low-risk sentinel groups. Duplicate vials of saliva and serum were collected from 479 high-risk and 1039 low-risk subjects. One vial of each pair was analysed blind in two laboratories, one in the USA and the other in Myanmar. The US laboratory followed WHO confirmatory strategy III with three different enzymelinked immunosorbent assays (ELISAs), while the laboratory in Myanmar followed strategy I with one ELISA. Serum testing in the US was the gold standard. The Cambridge ELISA with saliva was a more effective surveillance tool (sensitivity 90·5%, specificity 99·5-100%) for describing the frequency of subjects with HIV antibodies than the serum ELISA supplied to Myanmar by WHO (95·9% and 98·3%, respectively). Saliva is recommended as a safe and effective alternative to serum for HIV antibody testing with ELISA in surveillance programmes in developing countries.

Elevated soluble c-erbB-2 antigen levels in the serum and effusions of a proportion of breast cancer patients.

An enzyme-linked immunosorbent assay (ELISA) for the extracellular domain of the c-erbB-2 oncogene product was developed and evaluated to determine if soluble c-erbB-2 could be detected in the serum and effusions of cancer patients. Sera from 208 previously untreated or progressing cancer patients and 69 healthy controls were assayed in a double-antibody sandwich ELISA that used two monoclonal antibodies to the native extracellular domain of the c-erbB-2 receptor. Fisher's exact test was used to analyze the statistical significance of the frequency of elevated serum c-erbB-2 levels. Immunoprecipitation and Western blotting were used to characterize further the c-erbB-2 immunoreactivity in the serum of four breast cancer patients. Sera from 12 of 53 patients (23%) with metastatic or locally advanced breast cancer, zero of 69 controls, one of 31 patients with ovarian cancer (3%), and two of 124 other cancer patients (2%) had soluble c-erbB-2 values greater than or equal to 5 U/mL. The number of breast cancer patients with elevated serum c-erbB-2 levels was significantly greater than that of the control group (P less than .0001), the ovarian cancer group (P less than .03), and the other cancers group (P less than .0001). Also, two of five effusions (40%) from breast cancer patients had an elevated soluble c-erbB-2 antigen level, compared with zero of 17 effusions from patients with benign diseases. Western blotting of four sera from breast cancer patients with elevated serum c-erbB-2 antigen levels produced bands of approximately 105 kD that seemed to correlate in intensity with increasing ELISA serum levels. Serum c-erbB-2 levels are elevated in approximately one fourth of patients with locally advanced or metastatic breast cancer.

Production of human immunoglobulin G reactive against human cancer in tumor-bearing mice with severe combined immunodeficiency reconstituted with human splenic tissues.

Splenic tissues derived from patients with gastric cancer were implanted into mice with severe combined immunodeficiency (SCID) and then the mice were challenged with COLO‐20S, a human colon cancer cell line. Production of human immunoglobulin G (IgG) reactive against the COLO‐205 cells was detected by enzyme‐linked immunosorbent assay in sera from the reconstituted and tumor‐bearing SCID mice. The titers of the reactive IgG relative to total IgG in the sera of SCID mice began to increase from one week after implantation of the tumor cells, and became 10‐ to 100‐fold higher than that in the donor's serum by 3–4 weeks. This model using implantation of human cancer cells in SCID mice reconstituted with human splenic tissues would facilitate further studies of human cancer immunology.

Passive protection of suckling infant mice against F41-positive enterotoxigenic Escherichia coli strains by intravenous inoculation of the dams with monoclonal antibodies against F41.

Ten monoclonal antibodies (MAbs) against five different epitope clusters of adhesion factor F41 (two MAbs per cluster) were tested for protection of infant mice against an oral challenge with F41-positive enterotoxigenic Escherichia coli (ETEC) B2C and B41M. Infant mice suckling dams intravenously inoculated with MAbs were orally challenged, and the survival rates were measured for 12 days after inoculation and challenge. Irrespective of their epitope specificity, all F41 MAbs given in a single dose of 4 mg per dam had a protective effect against both ETEC strains. In contrast, one K99 MAb of the same isotype and given in the same dose as the F41 MAbs did not protect infant mice at all. A reduction in the dose of F41 MAbs to 0.032 mg per dam resulted in a decrease in protection. Two different MAbs against the same epitope cluster were not necessarily equally protective. Combining MAbs two by two, whether the MAbs recognized the same epitope cluster or not, resulted in protective activity essentially similar to that obtained with each MAb separately, without any improvement. Therefore, one MAb against any epitope may be sufficient for protection. Enzyme-linked immunosorbent assay (ELISA) titers of MAbs in the serum of dams were similar, irrespective of the epitope specificity of the MAbs, and gradually decreased from day 1 to day 12 after inoculation. We found a good correlation between colostrum and milk ELISA titers of MAbs and serum ELISA titers of MAbs. Colostrum and milk MAb titers were 10-fold lower than corresponding serum MAb titers and stayed high until day 5 after inoculation. The most protective MAb had the highest ELISA titers in colostrum and milk for the first 5 days after inoculation. ETEC strain B2C colonized the intestines of infant mice suckling MAb-inoculated mothers until day 12 after challenge. Intestinal levels of the challenge strain were high on day 2 but never reached the very high numbers (10(9) to 10(10)) described previously in a diarrheic infant mouse model. MAbs did not eliminate the challenge ETEC strain from the intestines of infant mice.

Diagnostic accuracy of a Mycobacterium phlei-absorbed serum enzyme-linked immunosorbent assay for diagnosis of bovine paratuberculosis in dairy cows.

The purpose of this study was to describe the responses of sera from five groups of cattle to an enzyme-linked immunosorbent assay (ELISA) for paratuberculosis by using serum absorbed with Mycobacterium phlei at a single working dilution. The infection status of the cattle was determined by fecal culture. Cattle with different levels of exposure (high versus low prevalence and test negative) and disease manifestation (clinically suspect infection versus subclinical infection) were examined, as follows: (i) two paratuberculosis-negative herds; (ii) a fecal culture-confirmed, clinically suspect cases of paratuberculosis; (iii) cows from a paratuberculosis-infected herd with a high infection rate, as determined by fecal culture, but with no clinical cases at the time of sampling; (iv) cows from three paratuberculosis-infected herds known to have paratuberculosis diagnosed on the farm (low infection rate determined by fecal culture); and (v) one fecal culture-negative herd with known serologically positive cattle. Results generally showed a decreased ELISA response when absorbed rather than nonabsorbed serum from each animal was used. The results of the fecal culture confirmed clinically suspect cases, which were analyzed in relation to the amount of colonies isolated from the animals on fecal culture (0, +, ++,+++ , ++++, and above). There was a significant increase in the ELISA response for animals with heavy Mycobacterium paratuberculosis shedding ( ++++ or above), when both unabsorbed and absorbed sera were used, compared with the response in animals that were fecal culture negative or that shed M. paratuberculosis at lower levels (less than +) (P less than 0.05). The effects on sensitivity and specificity by using different cutoff points for the five groups of cattle with different levels of exposure is described, since sera were not discretely segregated into distinct groups of positive and negative samples. The specificity of the ELISA in the two fecal culture-negative herds was 100% at an ELISA cutoff of an optical density (OD) of 0.1 and above for absorbed serum. For unabsorbed serum the specificity was 62.9% at a similar cutoff value. Similarly, the specificity of the fecal culture-negative, serologically positive herd increased from 37.5 to 72.2 at an ELISA cutoff value of 0.1 to 0.2 (OD) by using absorbed versus unabsorbed serum from 75.0 to 94.4 at an ELISA cutoff value of 0.2 to 0.3 (OD).

Antibodies against synthetic oligopeptides deduced from the putative core gene for the diagnosis of hepatitis virus infection.

Immunoassays were developed to detect antibodies against oligopeptides deduced from the putative core gene of hepatitis C virus, and their performances were compared with that of the commercial immunoassay for antibodies against the product of nonstructural regions of hepatitis C virus (anti-C100-3). A 19-mer oligopeptide (CP10) and a 36-mer oligopeptide (CP9) were chemically synthesized, which represented hydrophilic regions of the product of the hepatitis C virus core gene. They were used to capture corresponding antibodies, anti-CP10 and anti-CP9, by enzyme-linked immunosorbent assay in sera from patients with acute or chronic non-A, non-B liver disease and in blood donations. At the onset of acute non-A, non-B hepatitis, anti-CP10 was detected in 15 of 20 patients (75%), and anti-CP9 was detected in 14 patients (70%). This was more frequent than anti-C100-3, which was found in only 9 patients (45%). In 186 patients with chronic non-A, non-B liver disease, anti-CP9, anti-CP10 or both were detected in 170 patients (91%). This was more frequent than anti-C100-3, which was found in 138 patients (74%). Blood with anti-CP10 as the single serological marker for hepatitis C virus infection transmitted non-A, non-B hepatitis by needlestick exposure. In sera from 558 apparently healthy blood donors, anti-CP10 was detected in 55 donors (9.9%), anti-CP9 was detected in 26 donors (4.7%) and anti-C100-3 was detected in 7 donors (1.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of tumor necrosis factor in humans undergoing cardiopulmonary resuscitation with return of spontaneous circulation

Tumor necrosis factor-alpha (TNF) was measured in 21 patients who presented to the emergency department in normothermic, nontraumatic cardiopulmonary arrest and who had eventual return of spontaneous circulation (ROSC). Tumor necrosis factor was measured by an enzyme-linked immunosorbent assay in serum collected at various time points after the initiation of cardiopulmonary resuscitation (CPR). Tumor necrosis factor was not detected within 4 hours post-ROSC in any patient, but was detected in all nine patients in whom survival post-ROSC was 6 hours or more. Six of nine patients demonstrated TNF presence at 6 hours. No patient demonstrating TNF at 6 hours survived longer than 27 hours post-ROSC. In patients surviving at least 12 hours, production of 400 pg/mL TNF was associated with a 100% mortality. Tumor necrosis factor is released in cardiopulmonary arrest patients who survive at least 6 hours post-ROSC and may play a role in the global ischemia-reperfusion phenomena of CPR.

Immunoglobulin G subclass values in healthy black and white children

To determine whether IgG subclass concentrations differed between healthy black and white children, we measured IgG1, IgG2, IgG3, and IgG4 immunoglobulins by enzyme-linked immunosorbent assay in sera from 246 black children aged 6 to 42 months. We then compared these values with the normal values established for 664 white children aged 6 to 60 months. The IgG1, IgG2, and IgG4 subclass concentrations of the black children were lower than those for white children; many of the values were below the 95% confidence limits established for white children: 46 (19%) of 246 IgG2 values and 19 (8%) of 246 IgG4 values for black children were below the normal limits. We compared the geometric mean values for black and white children, as determined for each 6-month age grouping between 6 and 42 months of age; 367 of the 664 white children were less than 42 months of age and were included in this analysis. The geometric mean values for IgG1, IgG2, and IgG4 levels were consistently lower for black children than for white children. The differences were significant for IgG1 subclass values of those children older than 24 months and for IgG2 and IgG4 values of those children older than 18 months. No consistent differences were noted for IgG3 subclass values. We conclude that young black children have lower IgG1, IgG2, and IgG4 serum concentrations than are found in white children. If normal IgG values for white children are used, healthy black children may be erroneously classified as IgG subclass deficient. The mechanism and biologic relevance of these population differences need to be evaluated.

Multiple antigen peptides for specific detection of antibodies to a malaria antigen in human sera

Multiple antigen peptides (MAP), consisting of a number of peptide copies synthesized on a branching lysyl core, offer a novel approach for rendering small peptides immunoreactive in solid-phase immunoassays. An octameric MAP, carrying 6 repeats of the sequence -N-A-A-G-, tandem repeated in the immunodominant region of the circumsporozoite (CS) protein of Plasmodium malariae, was used as a model to evaluate the suitability of the MAP system in an indirect enzyme-linked immunosorbent assay (ELISA) for detecting antibodies against a parasite antigen in individuals exposed to natural infection. The reaction of endemic sera in ELISA on MAP8-(NAAG)6 was related to that obtained in immunofluorescence on sporozoites, indicating the specificity of the antibody-MAP interaction. The reactivity of immune sera was found to be directed only against the (NAAG)6 moiety of the MAP and not against the lysyl core, since antibody binding to MAP8-(NAAG)6 was completely inhibited by (NAAG)6-NA monomer, but remained uninfluenced when lysyl core was used as competing ligand. The levels of antibodies to MAP8-(NAAG)6, in two groups of individuals naturally exposed to malaria infection, appeared to be related to their respective exposure to the parasite.

43-kilodalton glycoprotein from Paracoccidioides brasiliensis: immunochemical reactions with sera from patients with paracoccidioidomycosis, histoplasmosis, or Jorge Lobo's disease

Sera from patients with paracoccidioidomycosis (PCM), histoplasmosis (HP), or Jorge Lobo's disease (JL) were titrated against purified gp43 from Paracoccidioides brasiliensis by using both enzyme-linked immunosorbent assay (ELISA) and immunoprecipitation (IPP) reactions with 125I-labeled antigens. In IPP, PCM sera and other sera could be distinguished on the basis of serum titers, whereas in ELISA, 53% of the HP sera and 29% of the JL sera reacted similarly to the PCM sera. To investigate the possible role of the carbohydrate epitopes in these reactions, we compared the reactivities of sera from several patients with native and deglycosylated gp43. Competition experiments were carried out with monosaccharides as inhibitors. The results suggest that greater than 85% of the reactions of the PCM sera with gp43 involved peptide epitopes. Cross-reactions with HP and JL sera in ELISA were predominantly attributed to periodate-sensitive carbohydrate epitopes containing galactosyl residues. HP and JL sera which reacted strongly with gp43 in ELISA were only weakly reactive or did not react in IPP with labeled antigens in solution. Moreover, ELISA reactions could be significantly inhibited either by monosaccharides or by periodate treatment. Apparently, carbohydrate epitopes in gp43 are more accessible to the antibodies when the molecule is bound to a plastic substrate than when it is in solution. Structural changes in the gp43 antigen arising by N deglycosylation abolish reactivity with PCM sera and support the existence of conformational peptide epitopes.

Positive serum antibody and negative tissue staining for Helicobacter pylori in subjects with atrophic body gastritis

Helicobacter pylori is rarely found in gastric biopsy specimens from individuals with atrophic gastritis of the body mucosa. To determine if subjects with atrophic body gastritis have evidence of previous infection with H. pylori, immunoglobulin G antibody to H. pylori was measured by enzyme-linked immunosorbent assay in sera of 399 Finnish subjects. In 124 subjects, multiple biopsy specimens from body and antrum had been evaluated for the presence of H. pylori by Giemsa staining. Antibody correlated well with H. pylori staining except in the subgroup with atrophic body gastritis, in whom the prevalence of seropositivity (86%) was significantly greater than the prevalence of positive staining (33%) (P < 0.001). Twenty-five subjects had positive antibody and negative staining. This group had a significantly higher prevalence of atrophic body gastritis (80%), lower maximal acid output, lower serum pepsinogen I levels, and higher serum gastrin concentrations than did seropositive subjects with H. pylori. These data suggest that most patients with atrophic body gastritis, despite having a low incidence of current overt infection, have been infected with H. pylori at some point in their lives.