Comparison of serological tests for the detection of antibodies against Chlamydia trachomatis and Chlamydia pneumoniae in rheumatological patients

In cases of reactive arthritis, a suspected Chlamydia trachomatis infection is often detected by serological methods. However, mostly tests with genus-specific antigens are used, neglecting the fact that antibodies against Chlamydia pneumoniae are highly prevalent in the adult population. Therefore we tested sera of 129 patients with various rheumatological disorders and of 18 healthy persons in parallel with a genus-specific test (IPAZYME) and with the species-specific microimmunofluorescence test for C. trachomatis and C. pneumoniae antibodies. The data showed that 55% of the 64 IPA-positive results were caused by antibodies (IgG) against Chlamydia pneumoniae, only 6% by anti-Chlamydia trachomatis IgG and 20% by both specificities. For IgA antibodies, the percentages were 44%, 12.5% and 12.5% respectively. In 12 IPA-positive cases, the MIF showed no reaction. 58% of all 147 sera tested with MIF had IgG antibodies against C. pneumoniae, 5% had anti-C. trachomatis IgG and 8% IgG against both species. The percentages for IgA were 29%, 2% and 2%, respectively. IgM positivity in MIF disappeared after absorption with rheumatoid factor absorbent. No significant differences were found between the various groups of patients. The data suggest that due to the high prevalence of anti-C. pneumoniae antibody, genus-species tests cannot be used as screening tests for the serological diagnosis of C. trachomatis infections.     

Young Malaysian children with lower respiratory tract infections show low incidence of chlamydial infection

OBJECTIVE: The incidence of Chlamydia pneumoniae and Chlamydia trachomatis infection was studied among infants and young children admitted to hospital for the management of lower respiratory tract infections, over a 12 month period. METHODOLOGY: Respiratory secretions were examined for chlamydiae by cell culture, enzyme-linked immunosorbent assay and polymerase chain reaction-enzyme immunoassay. Sera were tested by micro-immunofluorescence for chlamydial IgG, IgM and IgA. Other bacterial and viral pathogens were also looked for by standard cultural and serological methods. RESULTS: Of 87 patients aged 2 months-3 years, an aetiologic diagnosis was made in 41 (47.1%). C. pneumoniae and C. trachomatis were each detected in 1 (1.2%) of the patients. Among common bacterial pathogens, Haemophilus influenzae (13.8%) and Streptococcus pneumoniae (8.1%) were the most frequently identified. Respiratory viruses and elevated Mycoplasma pneumoniae antibodies were found in 10.3% and 9.1% of patients, respectively. CONCLUSION: Chlamydiae are infrequent causes of community-acquired acute lower respiratory tract infections in infants and very young children in Malaysia.     

Age-dependent Neisseria meningitidis serogroup C class-specific antibody concentrations and bactericidal titers in sera from young children from Montana immunized with a licensed polysaccharide vaccine

Neisseria meningitidis serogroup C bactericidal titers and class-specific enzyme-linked immunosorbent assay (ELISA) antibody concentrations were measured in sera from 173 children (1 to 5 years old) before and 6 weeks and 7 months following vaccination with a quadrivalent (A/C/Y/W-135) polysaccharide vaccine. The immune responses of the children were compared with those of 40 adults 6 weeks postvaccination. Both bactericidal titers and ELISA antibody concentrations were significantly higher in the adults than in the children (P < 0.05). In addition, the ratio of immunoglobulin G (IgG) to IgM was higher in the children than in the adults. With an ELISA total antibody concentration of >/=2 microg/ml used as a measure of seroconversion, >/=84% of the individuals from each age group responded to the serogroup C polysaccharide. However, with a >/=4-fold-increase in bactericidal titer used, only 18% of 1-year-olds, 32% of 2-year-olds, and 50 to 60% of 3-, 4-, and 5-year-olds seroconverted. The ELISA results suggest that >50% of all children retained >/=2 microg of total antibody per ml at 7 months postimmunization. However, the bactericidal titers suggest that <10% of children <4 years old retained a >/=4-fold increase at 7 months following vaccination. Of particular note, 59 of 79 sera (75%) from the 1- and 2-year-olds had high ELISA antibody concentrations (2 to 20 microg/ml) with no associated bactericidal titer (<1:8). Discordant results between bactericidal titers and ELISA antibody concentrations were not explained by the presence of IgA blocking antibody or relative levels of IgG and IgM. The bactericidal results show age-dependent differences in the production and retention of antibody in young children immunized with serogroup C polysaccharide; these differences are not evident with the ELISA data.     

Serodiagnosis of atypical bacterial respiratory infections

Since prevalence of antibodies to bacteria causing atypical respiratory infections in Israel is as yet unknown, a 5-year antibody prevalence study was performed. Seroreactivity to Chlamydia pneumoniae (TWAR), with titers > or = 1:16 by microimmunofluorescence assay (MIF) was detected in 725/1305 (55.5%) of patients. 47/1012 ((4.6%) of adult patients had MIF results indicating recent infection with TWAR, (IgG titers of > or = 1:512, and/or IgM titers of > or = 1:16, and/or seroconversion). Antibody prevalence and titers were low in children aged 1-10 years, increased in teenagers, and peaked in adults and the elderly, in whom prevalence was up to 79% and mean geometric titer up to 1:163. Unlike the consistency in TWAR antibody prevalence and serological evidence of recent infection during the study period, a significant decrease in those variables was observed for Chlamydia trachomatis during the first 3 study years. Antibodies to M. pneumoniae were detected in 53 and to Legionella sp. in 47 out of 763 patients. There was serological evidence of recent infection with M. pneumoniae in 10 (including 7 children) and with Legionellae in 8. Improved diagnosis of atypical respiratory infection might be achieved by the combined use of these proposed serological procedures.     

Serological follow-up of patients with paracoccidioidomycosis treated with itraconazole using Dot-blot, ELISA and western-blot

Twenty-seven mycologically proven cases of paracoccidioidomycosis (PCM) were treated with itraconazole (100-200 mg/day in month 1 and 100 mg/day until month 6-8) and evaluated clinically and serologically, up to 3.5 years post-therapy, using Dot-blot and ELISA for measuring the titers of IgG, IgA and IgM anti-P.brasiliensis antibodies and Western-blot for determining IgG, IgA and IgM antibodies against the antigen components of the fungus. Before treatment, 81.5% (Dot-blot) and 84% (ELISA) of the patients presented elevated IgG anti-P.brasiliensis antibody titers which dropped slightly with treatment. On the other hand, the percentages of pre-treatment high-titered sera for IgA and IgM anti-P.brasiliensis were lower (51.9% and 51.8%: Dot-blot; 16.5 and 36%: ELISA, respectively) but the titers tended to become negative more frequently with treatment. Prior to treatment, the percentages of positivity for IgG, IgA and IgM anti-P.brasiliensis antibodies in Western-blot were 96%, 20.8% and 41.6%, respectively. Antigens with molecular weights varying from 16-78 kDa, from 21-76 kDa and from 27-78 kDa were reactive for IgG, IgA and IgM antibodies, respectively. The most frequently reactive antigenic components had molecular weights of 27, 33 and 43 kDa for IgG, and 70 for IgA and IgM antibodies. During the period of study, the patients responded well to treatment. The present data confirm the diversity and complexity of the humoral response in PCM, and the importance of utilizing different serological tests to detect IgG, IgA and IgM anti-P. brasiliensis antibodies.     

Antibody response to Chlamydia pneumoniae infection in children with respiratory illness

Serologic diagnosis of Chlamydia pneumoniae infection has been based on the microimmunofluorescence test (MIF). However, recent prospective studies in children have found that >50% infected with C. pneumoniae failed to develop any antibodies detectable by MIF. In this study, single sera from 46 culture-positive and 42 culture-negative children with respiratory infection and known MIF status were examined by immunoblotting. Forty-one (89.1%) of the single sera from culture-positive and 27 (64.3%) from culture-negative children reacted to C. pneumoniae antigens in immunoblot. C. pneumoniae proteins most frequently recognized by sera from culture-positive patients were at 101-102, 72-76, 50-52, 48-49, 43-44, 41-42, and 30-31 kDa. However, there did not appear to be a correlation of specific band patterns and culture status.     

Humoral immune response against antigen 60 in BCG-vaccinated infants

An ELISA assay based on the A-60 antigen complex from Mycobacterium bovis BCG cytoplasm was used to detect anti-mycobacterial antibodies of different classes in the sera of 63 BCG-vaccinated infants during the 6-month post-vaccination period. The mean IgM and IgA levels increased, whereas the mean IgG level decreased after BCG vaccination. However, in a minority of cases only Ig levels were above the cut-off line: this was true for IgM in 11/63 (17%) cases and for IgA in 14/63 (22%) of cases but none of the tested infants was anti-A60 IgG ELISA positive. Fifty-two infants (83%) were tuberculin-positive eight weeks after vaccination, and no significant difference in mean antibody levels of tuberculin-positive and negative cases was observed, except for IgG (p < 0.05).     

A new approach to the brachial plexus: clinical results

Chlamydia pneumoniae was isolated from the pharyngeal swab of a 15-year-old patient with acute bronchitis. The serum IgM antibody against C.pneumoniae was elevated up to 160-fold in the acute phase and decreased to 20-fold in the convalescent phase using the microimmunofluorescence (MIF) test. IgG antibody titers in the acute phase and the convalescent phase were 40-fold and 160-fold respectively using the MIF test. The patient recovered from the bronchitis without any effective treatment, indicating spontaneous cure of the disease.     

Anticonvulsant and glutamate release-inhibiting properties of the highly potent metabotropic glutamate receptor agonist (2S,2''R, 3''R)-2-(2'',3''-dicarboxycyclopropyl)glycine (DCG-IV)

IgA has an important function in the gastrointestinal immune system. We investigated IgA anti-ganglioside antibodies in Guillain-Barré syndrome (GBS) and Fisher's syndrome (FS) subsequent to Campylobacter jejuni enteritis. In previous studies, serological diagnosis of C. jejuni infection was based on the detection of IgG, IgA, and IgM anti-C. jejuni antibodies. Our study, however, showed that the detection of IgG anti-C. jejuni antibody alone was sufficient for the serological diagnosis of antecedent C. jejuni enteritis in GBS and FS, when the cut-off level was defined for results of sera from C. jejuni-isolated patients. Serological evidence of C. jejuni infection was found in 62 (31%) of 201 GBS patients and 12 (18%) of 65 FS patients. IgA anti-GMI antibody was detected in sera from 33 (16%) of the GBS patients, 1 (2%) of the FS patients, and none of the 46 normal control subjects. IgA anti-GM1 antibody titers were significantly higher in the GBS patients with positive C. jejuni serology than in those with negative serology (P < 0.0001) or the FS patients with positive C. jejuni serology (P = 0.007). IgA anti-GQ1b antibody was detected in sera from 18 (28%) of the FS patients, 9 (4%) of the GBS patients, and none of the normal control subjects. FS patients with positive C. jejuni serology had significantly higher titers of IgA anti-GQ1b antibody than those with negative serology (P = 0.01) or the GBS patients with positive C. jejuni serology (P < 0.0001). We conclude that anti-GM1 and anti-GQ1b IgA antibodies are closely associated with antecedent C. jejuni enteritis in GBS and FS, respectively.     

Evaluation of a stage-specific proteolytic enzyme of Schistosoma mansoni as a marker of exposure

Cercarial elastase (CE) is one of the first proteins released in the host by invading schistosome cercariae. An enzyme-linked immunosorbent assay (ELISA)-formatted immunoassay has been developed to detect antibodies to the stage-specific CE antigen of Schistosoma mansoni as marker of exposure. We have evaluated this test system as an epidemiologic tool, using well-characterized sera collected from S. mansoni- and S. haematobium-infected subjects residing in endemic areas and from control subjects living in nonendemic areas in Egypt. Urine, stool specimens, and blood samples were collected from a sample of 272 endemic subjects randomly selected to represent different age groups in the range of 2-20 years of age. Of 47 S. mansoni-infected subjects, 41 (87.2%) had anti-CE IgG antibodies. Of 52 S. haematobium-infected cases, 38 (73.0%) had IgM antibodies to CE and 43 (82.7%) had IgG antibodies to CE. Of 173 egg-negative people in the endemic area, 84 (48.6%) were IgM positive and 99 (57.2%) were IgG positive. The mean IgM and IgG antibody levels were similar in the infected groups but were significantly lower in the egg-negative group (P = 0.001). All sera from young children (2-3 years of age) were uniformly ELISA negative. The prevalence of IgM and IgG antibodies to CE in children less than six years of age were significantly lower than in other age groups. There was no significant difference in prevalence rates of IgM and IgG anti-CE antibodies between subjects having other parasites present in the endemic area (Ascaris lumbricoides, Entrobius vermicularis, Hymenolepis nana, H. diminuta, Trichostrongylus spp., and Entamoeba histolytica) and those without any parasitic infection. All nonendemic sera (58), including those with other helminth infections, were uniformly ELISA negative for antibodies to CE. These findings suggest that antibodies to elastase indicate exposure, but not necessarily active schistosome infection.     

Isotypes and opsonophagocytosis of pneumococcus type 6B antibodies elicited in infants and adults by an experimental pneumococcus type 6B-tetanus toxoid vaccine

Streptococcus pneumoniae is a major respiratory pathogen of infants, children, and the elderly. Polysaccharide vaccines have been useful in adult populations but do not elicit protective immunity in infants and young children. To enhance their immunogenicity, vaccines of pneumococcal polysaccharides conjugated to proteins are being developed. In this study antibody levels and opsonic activities were compared in sera of infants and adults injected with pneumococcal polysaccharide type 6B (Pn6B) conjugated to tetanus toxoid (TT) (Pn6B-TT). Healthy infants were injected with Pn6B-TT; group A was injected at 3, 4, and 6 months of age, and group B was injected at 7 and 9 months of age. A booster injection was given at 18 months. Adults were injected once. Antibodies were measured by enzyme-linked immunosorbent assay and radioimmunoassay, and their functional activities were measured by opsonophagocytosis of radiolabelled pneumococci. In adults, increases in immunoglobulin M (IgM), IgG, IgA, IgG1, and IgG2 to Pn6B were observed. Infants reached adult levels of IgG1 anti-Pn6B after the primary injections. After the booster injection the infant groups had total IgG- and IgM-Pn6B antibody levels similar to those of adults. After the booster injection, IgG1 was the dominant infant anti-Pn6B isotype and at a level higher than in vaccinated adults, but IgA and IgG2 antibodies remained at very low levels. Opsonic activity increased significantly after Pn6B-TT injections; the highest infant sera showed opsonic activity comparable to that of vaccinated adults. Overall, opsonic activity correlated best with total and IgG anti-Pn6B antibodies (r = 0.741, r = 0.653, respectively; n = 35) and was highest in sera with high levels of all Pn6B antibody isotypes. The results indicate the protective potential of a pneumococcal 6B polysaccharide protein conjugate vaccine for young infants.     

Comparison of cardiac findings at necropsy in octogenarians, nonagenarians, and centenarians

The Toxoplasma gondii rhoptry protein Rop2 was expressed in Escherichia coli as a fusion protein containing 44 kDa of the 55-kDa mature Rop2, supplied with six histidyl residues at the N-terminal end (Rop2196-561). Humoral response during Toxoplasma infection of humans was analyzed by immunoglobulin G (IgG), IgA, and IgM enzyme-linked immunosorbent assay with Rop2196-561 as the antigen substrate. The analyzed sera were divided according to T. gondii-specific serological tests (IgG, IgA, or IgM indirect immunofluorescence and IgA or IgM immunosorbent agglutination assay) as group A (IgG+ IgA- IgM-; n = 35), group B (IgG+ IgA+ IgM+; n = 21), group C (IgG+ IgA+ IgM-; n = 5), and group D (IgG+ IgA- IgM+; n = 16). Twenty-six T. gondii-seronegative sera from individuals with other infections were also included (group E). Anti-Rop2 IgG antibodies were detected in 82.8% of group A sera and in 97.6% of the sera with acute-phase marker immunoglobulins (groups B, C, and D). The percentage of IgA antibody reactivity against Rop2196-561 was 17.1% in group A, 50% in group D, and 80.8% in groups B and C. The percentage of IgM antibody reactivity was 0% in groups A and C and 62% in groups B and D. Sera from group E failed to show IgA, IgM, or IgG antibody reactivity. Since T. gondii Rop2 elicits a strong humoral response from an early stage of infection, it is suggested that recombinant Rop2196-561 would be suitable for use in diagnostic systems, in combination with other T. gondii antigens, to detect specific IgG, IgA, and IgM antibodies.     

Evaluation of PCR, culture, and serology for diagnosis of Chlamydia pneumoniae respiratory infections

We prospectively studied 156 patients with a diagnosis of community-acquired pneumonia requiring admission. Several respiratory specimens were obtained for the detection of Chlamydia pneumoniae by cell culture and PCR. Three serum samples were obtained from each patient. Serological diagnosis of a C. pneumoniae infection was determined by the microimmunofluorescence (MIF) test, the complement fixation (CF) test, and recombinant lipopolysaccharide (LPS) enzyme-linked immunosorbent assay (ELISA; referred to as the rDNA LPS ELISA). Twenty-three patients (15%) had serological results compatible with acute C. pneumoniae infection; nine (39%) of these subjects were C. pneumoniae PCR positive. Twenty-two patients (14%) had positive PCR results without serological evidence of an acute C. pneumoniae infection. An attempt was made to calculate the sensitivities and specificities of the MIF test, rDNA LPS ELISA, and PCR for the diagnosis of chlamydial community-acquired pneumonia. Several "gold standards" were defined. Generally, the sensitivities of the rDNA LPS ELISA and MIF were comparable, while the sensitivity of the CF test was shown to be very low. Independent of the gold standard used, the best PCR results were obtained with nasopharyngeal specimens. However, the predictive value of a positive C. pneumoniae PCR result for patients with community-acquired pneumonia remains unknown and may be low. Although a widely accepted gold standard is still lacking, the rDNA LPS ELISA may currently be the preferred tool for diagnosing acute respiratory Chlamydia infections in routine clinical practice. However, the MIF test remains the method of choice for determining the prevalence of C. pneumoniae infections in a given community.     

Chlamydia pneumoniae and Helicobacter pylori infections in Sámi and Finnish reindeer herders

The Sámi people in northernmost Finland have lower mortality from cardiovascular diseases than the main population of Finland. Chronic infections caused by Chlamydia pneumoniae and Helicobacter pylori, both quite recently discovered gram-negative bacteria, have been associated with atherosclerosis. We studied the prevalence of these infections in Sámi and Finnish men by analysing the C. pneumoniae and H. pylori specific serum IgG and IgA antibodies using microimmune fluorescence and enzyme linked immunosorbent assay methods, respectively. The frequency of C. pneumoniae IgG antibodies and the age adjusted geometric mean titres differed significantly between these groups. The Finns were more often sero-positive than the Sámi (76% vs. 67%, respectively), the age adjusted geometric mean titre being 71.6 in the Finns and 38.3 in the Sámi; p = 0.001. No significant difference was found in the H. pylori IgG and IgA antibody prevalences, nor in the geometric mean titres between these groups. The difference in cardiovascular mortality between the Sámi and Finns may be partly explained by the lower incidence of chlamydial infections in the Sámi.     

Circulating antibodies to Chlamydia trachomatis in women: relationship to antisperm and antichlamydial antibodies in semen of male partners

The relation between antibodies to Chlamydia trachomatis and spermatozoa in sera of 112 asymptomatic female partners of infertile couples with no history of C.trachomatis infections and antichlamydial antibodies in semen or antisperm antibodies on ejaculated spermatozoa of their male partners was examined. Samples were tested for immunoglobulin (Ig)A and IgG antibodies to C.trachomatis by enzyme-linked immunosorbent assay; antisperm antibodies in sera and on motile spermatozoa were assayed by immunobead binding. IgG antibodies to C.trachomatis were detected in 24 (21.4%) of the women; only five (4.5%) women were positive for antichlamydial IgA. Antichlamydial IgG was detected in sera from 10 (40.0%) of 25 women whose partners had antichlamydial IgA in semen as opposed to 14 (16.1%) of 87 women whose partners' semen were negative for this antibody (P = 0.02). Similarly, antichlamydial IgG was detected in sera from five (50%) of 10 women whose partners had antichlamydial IgG in semen as opposed to 19 (18.6%) of 102 women whose partners' semen lacked this antibody (P = 0.03). There was no relation between antichlamydial antibodies in women and circulating antichlamydial antibodies in men. A strong correlation (P = 0.001) was observed between IgG antichlamydial antibodies in a woman's serum and antisperm antibodies on ejaculated spermatozoa of her partner [8 of 14 (57.1%) versus 16 of 98 (16.3%)]. Conversely, antichlamydial antibodies in a woman's serum was unrelated to the presence of antisperm antibodies in either her own serum or her partner's serum. The data demonstrate that chlamydial infections of the male genital tract, which are associated with antisperm antibody formation on ejaculated spermatozoa, are likely to be transmitted to the female partner. In contrast, the presence of antichlamydial antibodies in sera does not necessarily appear to indicate an infection of the genital tract and is not associated with the heterosexual transmission of C.trachomatis.     

Bovine mastitis caused by Listeria monocytogenes: kinetics of antibody responses in serum and milk after experimental infection

The kinetics of antibodies in serum and milk directed against proteins from Listeria monocytogenes were studied using 4 lactating cows after infection was experimentally induced in the udder with four strains of serotypes 4b or 1/2a. Antibodies (IgG and IgA) in samples of composite quarter milk and serum of the cow were measured by indirect ELISA. Microtiter plates were coated with proteins obtained from the culture supernatant of L. monocytogenes 4b. After challenge, an IgG response in serum and milk to listerial infections in the udder occurred for all cows, although the response varied among cows. In sera, the IgG titers reached a peak at 9 to 13 wk after challenge and remained elevated until 21 to 33 wk after challenge. In milk, the IgG titer increased significantly 3 wk after the challenge for all cows. A weak and nonpersistent increase in IgA antibodies also occurred. These results indicate that IMI by L. monocytogenes induced an increase of antibodies in milk, which could be detected with an ELISA test using our antigenic preparation. Therefore, this antigenic preparation could be used for the evaluation of a new method of diagnosis for bovine mastitis caused by L. monocytogenes.     

Overexpression of c-myc induces apoptosis at the prophase of meiosis of rat primary spermatocytes

Serum samples from 36 cervical carcinoma patients, 33 patients with high-grade squamous intraepithelial lesions, and 31 cytologically normal women were tested by enzyme-linked immunosorbent assay (ELISA) using human papilloma virus type 6 (HPV 6) and HPV 16 virus-like particles as antigens. Forty serum specimens from 1-year-old children were used to assign cutoff points. When serum samples from the subjects infected with HPV 16 were tested in an HPV 16 ELISA detecting immunoglobulin A (IgA), IgG, and IgM binding, 61% showed IgA, 44% showed IgG, and 39% showed IgM reactivity. Of HPV 6- or 11- or HPV 18-infected subjects. fewer than 17% showed IgA or IgG responses and 33% showed IgM reactivity. In contrast, 13% showed IgA, 10% showed IgG, and 16% showed IgM reactivity in the HPV DNA-negative controls. The results suggest that the IgA and IgG responses are HPV 16 specific and the IgM response is cross-reactive to different HPV types. On the other hand, the serological responses to HPV 6 did not differ in the patient and control groups. The percentages of patients positive for both IgA and IgG antibodies were significantly higher in the groups with high-grade squamous intraepithelial lesions (12% [4 of 33]; P = 0.04) and cancer (17% [6 of 36]; P = 0.02) than in the healty women (0% [0 of 31]), and the percentages for either IgA or IgG were higher for the cancer group (47% [17 of 36]; P = 0.01) than in the normal group (19% [6 of 31]). Most sera positive for IgA and IgG in the patient groups showed higher titers than those in the normal group. All these results suggest that high IgA and IgG responses are good indicators for estimating HPV 16 infection.     

Antibodies to Klebsiella pneumoniae lipopolysaccharide in patients with ankylosing spondylitis

The role of microbial lipopolysaccharides (LPS) in the aetiopathogenesis of ankylosing spondylitis (AS) is a matter of continuing debate. In this study, class-specific IgG, IgA and IgM antibodies against Klebsiella pneumoniae, Escherichia coli, Salmonella typhimurium and Salmonella enteritidis LPS were measured by enzyme-linked immunosorbent assay (ELISA) in 100 AS patients, 50 rheumatoid arthritis (RA) patients and 50 healthy control subjects. The AS patients had significantly elevated levels of IgG and IgA antibodies against K. pneumoniae LPS (P < 0.001) and IgA antibodies against E. coli LPS (P < 0.05) compared to healthy controls. There were no significant elevations of antibody levels against S. typhimurium and S. enteritidis in the three study groups. In addition, there was a correlation between IgG and IgA anti-K. pneumoniae LPS antibody levels and the acute-phase reactant C-reactive protein (P < 0.001).     

Survey of antitrypanosome antibodies and studies of their specificity and autoimmunity

As a part of investigations to characterize trypanosome infections in Taiwan, sera collected from patients admitted to Veterans General Hospital, Taipei were tested for antitrypanosome antibodies. A Trypanosoma cruzi extract-based enzyme-linked immunosorbent assay (ELISA) was used to screen and titrate 1,297 patient sera. High antitrypanosome titers were detected in 166 (12.8%) of these sera. Retitration of random samples of the high titer (HT) sera indicated a 5.4% false positive. Thirteen donors with high antitrypanosome ELISA titers were followed up. Twelve of then remained high serum titers also showed high ELISA titers against an extract of Trypanosoma conorhini. Hemocultures conducted on freshly drawn blood specimens of the 13 subjects did not provide any evidence of trypanosome infections. Electrophoretic analyses of sera from HT and low titer (LT) patients suggested differences between serum proteins of the subjects in each of the groups. Atypical reactions were observed in immunodiffusion tests performed with HT and LT sera and trypanosome extracts, while western blot analyses revealed a complex pattern of binding by both sera. The qualitative and quantitative differences in these tests suggested interactions of T. cruzi antigens with donor antibodies against unrelated antigens and/or with autoantibodies. Subsequent analyses did not indicate any association between rheumatoid factor and the reactivities of the HT sera with the parasites. However, antinuclear antibodies were detected with an indirect fluorescent antibody test (IFAT) in 50% of the HT sera and 22% of the LT sera. No differences were found between the levels of antilaminin activity of the two groups. The IFAT employing T. cruzi epimastigotes was positive for 100% of the HT sera and 22% of the LT sera. The data indicate that the high seropositivity recognized in this study is due in part to the activities of cross-reacting antibodies and/or autoantibodies in the sample population.