Differentiation of serological responses to Yersinia enterocolitica serotype O9 and Brucella species by immunoblot or enzyme-linked immunosorbent assay using whole bacteria and Yersinia outer membrane proteins

A review of serological tests to assist diagnosis of reactive arthritis: critical appraisal on methodologies

On a population-based level, the incidence of reactive arthritis (ReA) is 0.6–27/100,000. The definition of ReA varies and its pathogenesis is not yet clear. Attempts in basic immunology to suggest hypotheses for proliferation of forbidden B cell clones, molecular mimicry, and involvement of cross-reactive antibodies are helpful but not sufficient. Importantly, for the clinical diagnosis of the preceding infection, serology is widely used. Unfortunately, the accuracy of associations between serologic findings and clinical conclusions is plagued by poor standardization of methods. So far, few attempts have been done to examine the pitfalls of different approaches. Here, we review several serologic techniques, their performance and limitations. We will focus on serology for Yersinia, Campylobacter, Salmonella, Shigella, and Chlamydia trachomatis because these bacteria have a longer history of being associated with ReA. We also address controversies regarding the role of serology for some other bacteria linked to autoimmune disorders.

Evaluation of the recombinant 10-kilodalton immunodominant region of the BP26 protein of Brucella abortus for specific diagnosis of bovine brucellosis

Brucellosis is a disease with worldwide distribution affecting animals and human beings. Brucella abortus is the causative agent of bovine brucellosis. The cross-reactions of currently available diagnostic procedures for B. abortus infection result in false-positive reactions, which make the procedures unreliable. These tests are also unable to differentiate Brucella-infected and -vaccinated animals. The present work is focused on the use of a nonlipopolysaccharide (LPS) diagnostic antigen, a recombinant 10-kDa (r10-kDa) protein of B. abortus, for specific diagnosis of brucellosis. The purified recombinant protein was used as a diagnostic antigen in plate enzyme-linked immunosorbent assay (p-ELISA) format to screen 408 bovine serum samples (70 presumptively negative, 308 random, and 30 vaccinated), and the results were compared with those of the Rose Bengal plate agglutination test (RBPT) and the standard tube agglutination test (STAT). Statistical analysis in presumptive negative samples revealed 100 and 98.41% specificity of p-ELISA with RBPT and STAT, and an agreement of 91.43% with the tests using Cohen's kappa statistics. In random samples, the agreement of p-ELISA was 77.92% and 80.52% with RBPT and STAT, respectively. p-ELISA investigation of vaccinated samples reported no false-positive results, whereas RBPT and STAT reported 30% and 96.6% false-positive results, respectively. The data suggest that p-ELISA with r10-kDa protein may be a useful method for diagnosis of bovine brucellosis. Furthermore, p-ELISA may also be used as a tool for differentiating Brucella-vaccinated and naturally infected animals.

Development and Validation of a Competitive ELISA Kit for the Serological Diagnosis of Ovine, Caprine and Bovine Brucellosis

A competitive ELISA (Brucella-Ab c-ELISA) was standardized and validated for the detection of Brucella antibodies in cattle, sheep and goat sera using a monoclonal antibody (MAb 4B5A) produced against Brucella melitensis biotype 2. The specificity and sensitivity of the assay were 100% to a 67.5% cut-off point (B/Bo%). When compared with an indirect ELISA, the Brucella-Ab c-ELISA did not demonstrate cross-reactions when testing positive sera for antibodies to some Enterobacteriaceae. A comparison was made between the Brucella-Ab c-ELISA and the complement fixation and Rose Bengal tests. Results demonstrated that the Brucella-Ab c-ELISA is a valuable tool for the serological diagnosis of bovine and ovine/caprine brucellosis.

Serological discrimination by indirect enzyme immunoassay between the antibody response to Brucella sp. and Yersinia enterocolitica O:9 in cattle and pigs

A rapid, inexpensive and rugged serological test that distinguishes cattle and swine infected with Brucella sp. or Yersinia enterocolitica O:9 is described. The test protocol, which is an indirect enzyme immunoassay uses a high concentration of divalent cation chelating agents to minimize binding of Y. enterocolitica O:9 antibody to rough lipopolysaccharide antigen derived from B. abortus RB51. No false positive reactions were observed when testing 100 Canadian cattle and swine without any evidence of brucellosis. The assay detected 91.6% of cattle (n=155) and 93.5% (n=31) of swine infected with Brucella sp. Sera from 58 cattle and 38 swine exposed to Y. enterocolitica O:9 were negative while only 20 sera from 121 'false positive' reactors of unspecified origin gave low level positive reactions, eliminating 84% of the false positive reactions.

La brucellose à l’aube du 21e siècle

Human brucellosis is now a rare disease in countries where eradication programs (especially vaccination) against brucellosis in cattle, sheep, and goats have been successfully implemented. In France, fewer than 50 brucellosis cases are annually notified to the National Institute for Infection Surveillance. Human brucellosis, however, remains endemic in the Mediterranean basin, Middle East, Western Asia, Africa, and South America. Shortcomings of standard diagnostic methods for brucellosis (variable sensitivity of culture, frequent serological cross reactions) have been only partially resolved by modern molecular biology techniques. There are now 3 new challenges to be faced by the medical and veterinarian community: the expanding wildlife reservoir of brucellosis, with a possible impact on domestic animals; the emergence of Brucella. melitensis infections in cattle, for which prophylactic efficacy of available vaccines has not been established; and recent recognition of a huge animal reservoir of Brucella species in marine mammals, for which the potential virulence in humans remains unknown.

Epidemiological and serological survey of brucellosis in Mongolia by ELISA using sarcosine extracts

Brucellosis is an important zoonosis, and serological surveillance is essential to its control. However, cross-reactions of attenuated live cells of Brucella abortus strain S-19 and B. melitensis strain Rev-1 with Yersinia enterocolitica O9 or vaccinated animal sera interfere with accurate serological diagnosis by the Rose Bengal test (RBT). Therefore, we used ELISA with sarcosine extracts from the virulent B. abortus strain 544 to eliminate false-positives among RBT positive-sera. A total of 697 serum samples were collected in Mongolia from humans and animals in 23 nomadic herds. The herds were classified into three groups as brucellosis-endemic (BE), brucellosis-suspected (BS), or Brucella-vaccinated (BV). The number of 295 animals (43.0%) was positive by RBT, but 206 (69.8%) of these were positive according to ELISA; therefore, 30.2% of the RBT-positive sera were found to be false positives. The false positive samples for RTB represent 4.1%, 27.4%, and 68.2% of the animals from the BE, BS, and BV herds, respectively. In addition, 32% of RBT-positive human sera were also false positives. Thus, our ELISA would be more specific than RTB and useful for epidemiological surveillance for brucellosis.

Enzyme-linked immunosorbent assay to differentiate the antibody responses of animals infected with Brucella species from those of animals infected with Yersinia enterocolitica O9

Enzyme-linked immunosorbent assays using antigens extracted from Brucella abortus with n-lauroylsarcosine differentiated natural Brucella-infected animals from Brucella-vaccinated or Yersinia enterocolitica O9-infected animals. A field trial in Mongolia showed cattle, sheep, goat, reindeer, camel, and human sera without infection could be distinguished from Brucella-infected animals by conventional serological tests.

Prevalence of yersinia plasmid-encoded outer protein (Yop) class-specific antibodies in multitransfused Greek patients with thalassemic syndromes

OBJECTIVE: To evaluate the prevalence of class-specific antibodies (G, A, M) to Yersinia enterocolitica plasmid-encoded outer proteins (Yops), in a closely followed multitransfused population of patients with thalassemia. METHODS: Sera from 408 beta-thalassemic patients and 386 healthy blood donors used as controls were analyzed with the enzyme-linked immunosorbent assay (ELISA) for IgG, IgA and IgM antibodies to yersinia outer proteins. The Yop antigen for the ELISA was prepared using a plasmid-bearing wild-type strain of Y. enterocolitica of serotype O:8. RESULTS: Anti-Yop IgG antibodies were detected in 84 out of 408 beta-thalassemic patients (20.6%) compared with only eight out of 386 (2.1%) healthy blood donors. None of the sera of either group was positive for anti-Yop IgA or IgM antibodies. On evaluating patients with registered clinical and laboratory signs of a previous yersinia infection in the period from 1978 to 1996, we found that those with a positive agglutination test for Y. enterocolitica infection at the time of manifestation showed a higher rate of persisting IgG seropositivity to Yops than those with positive culture and clinical signs only. A significant percentage (9.49%) of the seropositive patients had no registered data of a past Y. enterocolitica infection. There was remarkable persistence of anti-Yop IgG antibodies in the thalassemic population, even in patients infected during the early years of our study period (1978--80). CONCLUSIONS: The results suggest that the determination of class-specific antibodies to Yops, which are specific antigens for the pathogenic yersiniae (Y. enterocolitica, Y. pseudotuberculosis and Y. pestis), in addition to its usefulness in the diagnosis of infection, will be a very sensitive and specific index for epidemiologic studies.

Aortoabdominal aneurysm infected by Yersinia enterocolitica serotype O:9

A 78-year-old-man was hospitalized for surgical treatment of a Yersinia enterocolitica serotype O:9 infected primary aortoabdominal aneurysm which ruptured soon after admission. Infection of aneurysm is an unusual manifestation of yersiniosis, especially in patients with no predisposing underlying condition. This case, and review of the literature, highlights that serotype O:9 has a predilection for vascular tissue. Cross reaction with Brucella spp. may be responsible for misdiagnosis of Y. enterocolitica O:9 infected aneurysms.

Infection of cattle with Yersinia enterocolitica O:9 a cause of the false positive serological reactions in bovine brucellosis diagnostic tests

During the last four years, an increasing number of cattle herds were classified positive by brucellosis screening tests in areas of Belgium and France free of the disease. No clinical symptom of brucellosis was reported in these animals and no Brucella abortus strains were isolated. After two years, no brucellosis outbreak was registered in all of the herds concerned. On this basis, all the serological reactions observed were classified as false positive. An ELISA using Yersinia Outer membrane Proteins (YOPs) as antigens was developed in order to discriminate between a Yersinia enterocolitica O:9 infection and a Brucella abortus infection. Antibodies against YOPs were detected in sera from Y. enterocolitica O:9 experimentally infected cattle (n = 4) but not in sera from B. abortus experimentally infected cattle (n = 4). In a field study, 66.7% of the 174 serum samples from cattle presenting false positive serological reactions showed anti-YOPs antibodies whereas only 10% of 454 sera, classified negative by the brucellosis screening tests, showed anti-YOPs antibodies. Our results suggest that infections with Y. enterocolitica O:9 may cause false positive reactions in brucellosis testing.

Cloning of Brucella abortus gene and characterization of expressed 26-kilodalton periplasmic protein: potential use for diagnosis

Brucella spp. are the causative agents of brucellosis in many different hosts, including humans. Most of the serological methods of diagnosis are based on the detection of antilipopolysaccharide antibodies, which makes the differentiation of vaccinated animals from infected animals difficult. By using molecular biology techniques, a gene that encodes a 26-kDa protein (BP26) was isolated from a Brucella abortus S19 genome lambda gt11 library. This protein is in the periplasm of B. abortus and in transformed Escherichia coli. It is exported to the periplasm via a preprotein of 29 kDa with a signal sequence of 28 amino acids. The nucleotide and amino acid sequences of this gene and protein did not show any similarity with those of previously sequenced genes. The use of this protein in Western blotting allowed the differentiation between vaccinated bovines from infected bovines and the detection of infected rams: on the other hand, sera from human patients with active brucellosis were positive, while sera from human patients with chronic brucellosis or without clinical signs were nonreactive. BP26 might be of value as an antigen for serological diagnosis of brucellosis in different mammals.

Serological crossreactivity between Brucella abortus and Yersinia enterocolitica 0:9 II the use of Yersinia outer proteins for the specific detection of Yersinia enterocolitica infections in ruminants

Yersinia outer protein (YOP) preparations from Y. enterocolitica and Y. pseudotuberculosis were used as antigens in immunoblots for the detection of Yersinia infections in experimentally and naturally infected ruminants. Sera from 9 groups of animals were used: (1) 51 sera from cattle which were false-positive in the standard brucellosis serological tests, (2) 52 sera from brucellosis-negative cattle, (3) 51 sera from a deer herd in which 16 animals were positive in the brucellosis tests and Yersina species were isolated from 5 animals, (4) 50 sera from a deer herd in which sera from all animals were negative in the brucellosis tests, (5) 107 sera from brucellosis-negative cattle which were received from throughout New Zealand, (6) 30 sera from cattle naturally infected with B. abortus and from which B. abortus was isolated, (7) 55 sera from cattle naturally infected with B. abortus, (8) 26 sera from cattle experimentally infected with B. abortus, with mostly high titres in the conventional brucellosis tests, and (9) sera taken weekly from 3 cattle experimentally infected with Y. enterocolitica 0:9. In all 3 Y. enterocolitica 0:9 experimentally infected animals the antibody reactivity against major YOPs in the Y. enterocolitica and in the Y. pseudotuberculosis YOP preparation correlated well with the strength in the classical brucellosis tests and with the staining of smooth lipopolysaccharides (SLPS) in blots, thus confirming the usefulness of YOPs for the detection of Yersinia infections. Sera from naturally infected cattle and deer herds, regardless of whether they were false positive or negative in the brucellosis tests, showed high frequencies of staining in YOP blots (53-58% in cattle and 80-100% in deer), indicating a high prevalence of field infections with Yersinia species in New Zealand. In two of the three sera groups from B. abortus infected animals, antibodies against YOPs were detected with high frequency, showing that dual infections may be common and may interfere with differential serological testing.

Cloning and sequence analysis of a newly identified Brucella abortus gene and serological evaluation of the 17-kilodalton antigen that it encodes

A thus far unknown gene encoding a Brucella abortus protein has been isolated from a lambda gt11 expression library probed with sera from Brucella-infected sheep. Sequence analysis of the cloned gene revealed the presence of an open reading frame of 158 amino acids encoding a protein of 17.3 kDa (calculated molecular mass). The recombinant B. abortus protein, expressed in Escherichia coli, and the corresponding Brucella melitensis protein migrated at the same apparent molecular masses as shown by Western blotting (immunoblotting). Among a series of serum samples from B. melitensis- or B. abortus-infected sheep and cows, 51 and 39%, respectively, showed a signal at 17 kDa on Western blot analysis of total protein extract from Brucella bacteria. These figures amount to 70 and 61% for sheep and cattle, respectively, in a competitive enzyme-linked immunosorbent assay with a specific monoclonal antibody. These data indicate that the 17-kDa antigen may be useful for serological diagnosis of Brucella infection.

Analysis of the immune response to Yersinia enterocolitica serotype-O:9-released proteins by immunoblot and ELISA

The immune response towards the released Yersinia enterocolitica outer membrane proteins (Yop) was analysed by immunoblotting and ELISA using a rabbit experimental model. Rabbits orogastrically or intravenously infected with the virulent (plasmid-bearing) Y. enterocolitica O:9 W836 strain developed a significant response by (IgG) antibodies to the released proteins having molecular weights of 51 (YopH) and 41 (LcrV) kDa, respectively. However, only in animals infected via the orogastric route were specific antibodies of the IgG class found against plasmid-encoded polypeptides of 35 (YopN) and 20 (YopQ) kDa. These results suggest that the expression of Yop in vivo may be conditioned by the route of infection used. Using ELISA, a significant response by IgG-class antibodies to YopH protein was evident in the sera from rabbits both orogastrically and intravenously infected with the virulent (pYV+) Y. enterocolitica O:9 W836 strain. By contrast, no specific antibodies to this antigen were detected in sera of rabbit infected with an avirulent (plasmid-cured) derivative (pYV-) strain. Accordingly, this protein could be very useful as an antigen in ELISA for serological diagnosis of infections caused by enteropathogenic strains of Yersinia spp.

Immunoblot studies in the differential diagnosis of porcine brucellosis: an immunodominant 62 kDa protein is related to the mycobacterial 65 kDa heat shock protein (HSP-65)

Smooth Brucella spp. share certain lipopolysaccharide antigens with other bacteria, resulting in serological cross-reactions which can prevent the definitive diagnosis of brucellosis. To identify other antigens with serodiagnostic potential, immunoblot studies following sodium dodecyl sulphate-polyacrylamide gel electrophoresis were carried out. Sera from pigs experimentally infected with Brucella suis and naturally infected feral pigs, sera from pigs from a farm with a known history of Yersinia enterocolitica 0:9 infection, Brucella Complement Fixation Test (CFT) reactor pigs (aetiology unknown) and pigs from consistently Brucella CFT negative farms were examined. Although B. suis infected pigs recognized a total of nine B. melitensis antigens, individual pigs rarely recognized more than three antigens in the range. A 62 kDa antigen was recognized by the majority (73%) of the Brucella infected pigs, but only by 10 to 23% of pigs from the other groups. This antigen was shown to be the Brucella homologue of the ubiquitous 65 kDa heat shock protein (HSP-65) family by immunoblot studies with 14 monoclonal antibodies to the Mycobacterium leprae HSP-65. Only four of these monoclones (Y1.2, ML-30, D7C and IIIC8) identified the B. melitensis 62 kDa protein suggesting that unshared, potentially Brucella specific, regions exist. Sera from Y. enterocolitica 0:9 infected pigs, CFT reactor pigs (aetiology unknown), CFT negative pigs and hyperimmune pig serum raised to Y. enterocolitica 0:9 also recognized B. melitensis antigens, most notably a 17 kDa protein. This antigen appears to be a common cross-reactive protein.

Immunoblotting of Yersinia plasmid-encoded released proteins: a tool for serodiagnosis

The plasmid-encoded, released proteins (RPs) of Yersinia enterocolitica serotypes 09 and 03 were separated by sodium dodecyl sulfate (SDS)-pore gradient gel electrophoresis. The RP-patterns of both serotypes proved to be identical. Five major proteins of M(r) 27,000, 34,700, 35,600, 45,800, and 46,800 were detected. Spontaneously plasmid-cured derivatives of the two serotypes lost the feature of protein release. By immunoblotting of RP with sera from patients suffering from acute Yersinia infections, specific and reproducible band patterns were obtained. Laser scan densitometry was applied to record the immunoreactions quantitatively. Predominant bands were detected at an M(r) of 34,700 and 35,600. IgA and IgM antibodies appeared as acute-phase markers rapidly decreasing in the reconvalescent phase. In contrast, immunoblots of patients with supposed chronic yersiniosis were characterized by a persisting IgA and elevated IgG reactivity. The application of RP as diagnostic antigens proved to be advantageous because they are naturally separated from cross-reacting proteins, common to pathogenic and nonpathogenic strains of Yersinia enterocolitica and Y. pseudotuberculosis.

Immunoblotting as a valuable tool to differentiate human visceral leishmaniasis from lymphoproliferative disorders and other clinically similar diseases

Diseases presenting with splenomegaly, fever and pancytopenia require intensive differential diagnostic considerations. These diseases include lymphoproliferative and autoimmune diseases, but also chronic infections like mansonian schistosomiasis or visceral leishmaniasis (kala-azar). Diagnosis for the latter is usually performed by testing for the presence of antileishmanial antibodies using the immunofluorescence test (IFT) or the enzyme-linked immunosorbent assay (ELISA) technique. Here, we report on patients who displayed positive antileishmanial antibody titres in the IFT and/or ELISA, but did not develop kala-azar and were eventually diagnosed as having one of the non-kala-azar diseases listed above. These false-positive sera proved to be seronegative when tested on a Leishmania immunoblot. Our studies lead us to recommend the immunoblot technique as a confirmatory test in cases with doubtful IFT or ELISA antibody titres.

Comparison of crossed immunoelectrophoresis, enzyme-linked immunosorbent assays, and tube agglutination for serodiagnosis of Yersinia enterocolitica serotype O:3 infection

Antibodies against Yersinia enterocolitica serotype O:3 were measured by crossed immunoelectrophoresis (XIE) using whole-cell sonic extract as antigen and by enzyme-linked immunosorbent assays (ELISAs) using either purified lipopolysaccharide or whole formalinized cells expressing virulence plasmid-encoded surface antigens (pYV+ cells). The results were compared with those obtained with the standard tube agglutination method. Sera from three groups of people were examined by using these assays. The first group consisted of healthy blood donors, the second consisted of patients with recent infection due to microorganisms other than Y. enterocolitica O:3, and the third consisted of patients with recent Y. enterocolitica O:3 infection. Sera from the last group were also obtained at regular intervals for 12 months postinfection. Results obtained with XIE and the ELISAs were in good agreement with those obtained with tube agglutination. Variation, diagnostic sensitivity, and diagnostic specificity were satisfactory for all the assays studied. However, the lipopolysaccharide ELISA was less laborious than tube agglutination and XIE and carried a somewhat greater diagnostic specificity than the pYV+ ELISA. XIE and the pYV+ ELISA, on the other hand, also had advantages. XIE enabled simultaneous examination of the individual antibody response against a wide range of chromosome-encoded antigens, and the pYV+ ELISA enabled detection of specific pYV antibodies when sera were adsorbed with formalinized pYV-cured Y. enterocolitica O:3 cells prior to the assay.