Quantitative determination of antibody to gonococcal pili. Changes in antibody levels with gonococcal infection

Bacterial pili, with emphasis on Mycobacterium tuberculosis curli pili: potential biomarkers for point-of care tests and therapeutics

CONTEXT

Novel biomarkers are essential for developing rapid diagnostics and therapeutic interventions Objective: This review aimed to highlight biomarker characterisation and assessment of unique bacterial pili.

METHODS

A PubMed search for bacterial pili, diagnostics, vaccine and therapeutics was performed, with emphasis on the well characterised pili.

RESULTS

In total, 46 papers were identified and reviewed.

CONCLUSION

Extensive analyses of pili enabled by advanced nanotechnology and whole genome sequencing provide evidence that they are strong biomarker candidates. Mycobacterium tuberculosis curli pili are emphasised as important epitopes for the development of much needed point-of-care diagnostics and therapeutics.

STD sensor based on nucleic acid functionalized nanostructured polyaniline

STD (sexually transmitted disease, Gonorrhoea) sensor based on nucleic acid probe (from Opa, a multi-copy gene of Neisseria gonorrhoeae) functionalized nanostructured-polyaniline coated onto indium-tin-oxide-coated glass plate has been fabricated using avidin-biotin as cross-linking agent. This DNA functionalized electrode can specifically detect upto 0.5 x 10(-15)M of complementary target within 60s of hybridization time at 25 degrees C by differential pulse voltammetry (DPV) using methylene blue as electro-active DNA hybridization indicator. This highly sensitive and specific nucleic acid functionalized nanostructured-polyaniline electrode can distinguish presence of N. gonorrhoeae from Neisseria meningitidis and Escherichia coli culture and spiked samples from the urethral swabs of the patients.

Questions about gonococcal pilus phase- and antigenic variation

Pathogenic organisms inhabit one of several defined locations within a host where temperature, pH, and nutrients are relatively constant. While the microorganism must adapt to different environments within the host, the host immune system is the most formidable predator that can limit the growth of a pathogen. Neisseria gonorrhoeae (the gonococcus, Gc) is the causative agent of gonorrhoea, and has evolved several systems for varying the antigenicity of different surface antigens, presumably to help evade the effects of the human immune system. The On/Off/On phase variation of surface structure expression also alters the antigenic characteristics of the bacterial cell surface. Antigenic variation of the major subunit of the pilus, pilin, occurs by unidirectional, homologous recombination between a silent locus and the expression locus. The silent loci lie from 1 to 900 kb from the expression locus in the chromosome yet all can donate their sequences to the expression locus. The genetic composition of the pilin loci of two Gc strains has been elucidated, and the types of changes that lead to altered forms of the pilus have been extensively characterized. However, little is known about the precise molecular mechanisms used to allow high-frequency, non-reciprocal, chromosomal recombination between pilin loci or about what regulates the process of maintaining chromosome fidelity.

Serovar specific immunity to Neisseria gonorrhoeae: does it exist?

OBJECTIVE

To determine whether the host immune response to gonorrhoea provides limited serovar specific protection from reinfection.

SUBJECTS

508 episodes of gonorrhoea diagnosed at a city centre genitourinary medicine clinic including 22 patients with multiple infections over a 4 year period.

METHODS

Patients with recurrent gonococcal infection were analysed with respect to the initial and subsequent serovars isolated.

RESULTS

No significant difference was seen in the prevalence of serovars isolated following a repeat infection compared with those without repeat infections. The site of the initial infection did not appear to influence the subsequent serovar isolated.

CONCLUSION

We found no evidence of serovar specific immunity in our population. It remains possible that populations with a higher prevalence of gonorrhoea and more frequent infections may have a quantitatively greater immune response.

Class specific antibody response to gonococcal infection

An enzyme immunoassay was used to determine IgM, IgG, and IgA antibodies to gonococcal pili in 68 patients with uncomplicated gonorrhoea, 35 women with pelvic inflammatory disease, and in 115 normal controls. A clear difference in response rate in all three antibody classes between patients with gonorrhoea and healthy controls was evident. Among women with gonorrhoea, the magnitude of antibody response was higher than among men with gonorrhoea, especially in the IgM class. No major differences were found in the overall distribution of serological findings between women with uncomplicated gonorrhoea and those with gonococcal pelvic inflammatory disease. Among this last group, however, high IgM antibody levels in acute phase sera were significantly associated with the isolation of Neisseria gonorrhoeae in the upper genital tract.

Indirect haemagglutination test using gonococcal pilus antigen: how useful to diagnose gonorrhoea?

In 1979 an indirect haemagglutination test (gonococcal antibody test) using gonococcal pilus antigen replaced the gonococcal complement fixation test as our routine procedure to show gonococcal antibodies. In the diagnosis of current gonorrhoea the sensitivity of the gonococcal antibody test was far superior to that of the gonococcal complement fixation test (about 55% versus 9% for first episode gonorrhoea). To evaluate the usefulness of the test result the following population groups were studied: 1376 patients undergoing medical examination for gonorrhoea (386 had gonorrhoea), 1384 healthy people aged 15-65, 54 patients with meningococcal disease, 30 children with respiratory tract infection, and 254 patients with evidence of various diseases other than neisserial infections that might be associated with symptoms of arthritis. These investigations showed that (1) non-specific positive gonococcal antibody test results occur rarely, (2) at least half the people who have had gonorrhoea remain seropositive (with titres of 1/40 to 1/160), and (3) a positive test result is more significant the younger the patient and the higher the titre. For younger people a positive test result should always be followed up by bacteriological examination; in all age groups titres of 1/320 or more should indicate medical examination for current gonorrhoea.

A common neisserial antigen evidenced by immunization of mice with live Neisseria meningitidis

Mice immunized with live meningococci developed antibodies directed against various antigens of Neisseria gonorrhoeae and Neisseria meningitidis, as demonstrated by immunoblotting. An antigen of 70 kilodaltons appeared to be common and stable in all gonococcal strains tested and highly immunogenic in mice infected with N. meningitidis.

The specificity of serum and local antibodies in female gonorrhoea

Immunoblotting has been used to compare the specificity of serum and local IgG and IgA antibodies in 13 women with gonorrhoea and in 13 controls. The technique allowed the simultaneous detection of antibodies to the major outer membrane proteins I, II, and III, pili and lipopolysaccharide; antibodies to another antigen which is probably a 'carbohydrate' were also detected. Serum and local IgG and IgA were found to be produced to several antigens during gonococcal infections, although the quantity of antibody was greater in serum. There was little change in the specificity of serum antibodies whereas the local response to LPS and pili increased over the two week study period. Serum antibody to LPS was more often IgG than IgA. Sera contained antibodies to 'carbohydrate', pili and lipopolysaccharide (LPS) whilst the local response was largely to the latter two antigens. Antibody to the outer membrane proteins was rarely detected. Control sera, but not vaginal washings, contained IgG and IgA to the major antigens but the staining of the immunoblots was less intense than those from patient's sera suggesting quantitative differences.

Evaluation of a serum gonococcal antibody test

The authors evaluated the Gonosticon Dri-Dot system as a tool for the determination of the prevalence of gonococcal serum antibody in two female populations. This paper discusses their findings.

Pilus- gonococcal variants. Evidence for multiple forms of piliation control

Pilus+ to pilus- transitions of gonococci (Gc) that involve rearrangement of pilin gene DNA yield the P-n phenotype, which is incapable of reversion (to pilus+). Reversion to pilus+ is found for nonpiliated Gc that have undergone no apparent pilin gene rearrangement. Among the reverting, nonpiliated Gc, two distinct phenotypes (P-rp- and P-rp+) occur and are differentiated according to their synthesis (or lack) of pilin subunits; both P-rp- and P-rp+ Gc contain pilin-specific mRNA. The occurrence of these different pilus- phenotypes strongly suggests that several mechanisms can account for changes in the piliation status of Gc; one of these involves pilin gene rearrangement but the others apparently operate at posttranscriptional levels. Reverting pilus- Gc may have a pathogenic advantage in being able to reversibly alter their host cell adherence-promoting surface properties through high frequency transitions in piliation status.

Structural and antigenic analysis of meningococcal piliation

Pilin with an Mr of 16,500 was purified to homogeneity from Neisseria meningitidis SP3428. Procedures which provided useful separation during purification included high-pressure liquid chromatography with a TSK size exclusion column, Sephacryl S-200 column chromatography, ion-exchange chromatography with SP-Sephadex, and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid composition of this pilin was similar to that previously reported for this species. The sequence of N-terminal 51 amino acids was also determined. The protein lacked a modified phenylalanine at the amino terminus and displayed six residues which were different from Neisseria gonorrhoeae in that region of the molecule determined to be the lectin-binding domain. Monoclonal antibody raised to this pilin was employed, along with a monoclonal antibody to an epitope common to all gonococcal pilins, to analyze the intra- and interstrain heterogeneity of meningococcal piliation. The results indicate that N. meningitidis displays considerable intra- and interstrain heterogeneity with respect to both pilus subunit size and antigenicity. The Mr of subunits ranged from 13,000 to 20,000.

Arrangement of pili in colonies of Neisseria gonorrhoeae

The morphology and arrangement of pili in the P++ colony phenotype of Neisseria gonorrhoeae were examined by a variety of electron microscopic techniques. The apparent structure and organization of gonococcal pili varied depending upon the method of specimen preparation. Pili as thin, individual, unbranched structures were demonstrated by negative staining and in sections of epoxy-embedded specimens. Pili forming thick structures which branch, subdivide, and rejoin to form an irregular lattice were demonstrated in specimens processed by the critical-point drying method and by rapid freezing and low temperature sublimination. We propose that in gonococcal colonies of the P++ phenotype, pili exist as individual threadlike structures only on the bacterial surfaces; as the pili leave the bacterial surfaces, they form thick bundles which branch, subdivide, and rejoin to form a supporting framework interconnecting the colony members. This arrangement of pili is usually disrupted by the commonly used method of negative staining and cannot be clearly detected within epoxy-embedded specimens. These data are summarized in a model depicting the organization of pili in the P++ colony phenotype of N. gonorrhoeae.

Application of immuno-blotting to the differentiation of specific antibodies in gonorrhoea

The technique of immuno-blotting was used to examine the specificity of serum antibodies in patients with gonorrhoea and to define the significant antigenic determinant present in the desoxycholate extracts of gonococcal cell walls used previously for serological diagnosis. IgG but not IgA antibody was directed predominantly against lipopolysaccharide. Antibodies to outer membrane proteins were not found as frequently as expected. There was a suggestion from the results that antibodies to antigen PI was more common in systemic than in local infections.

Analysis of the antigen specificity of the human serum immunoglobulin G immune response to complicated gonococcal infection

The antigen-specific basis of human serum immunoglobulin G antibody response to complicated gonococcal infection was studied in 13 patients by using the Western blot technique for transfer of proteins from sodium dodecyl sulfate-polyacrylamide gels to nitrocellulose paper. Of 13 patients (8 with disseminated gonococcal infection, 4 with pelvic inflammatory disease, 1 with gonococcal epididymitis), 12 reacted with protein I antigens and 9 with lipopolysaccharide (LPS). Sera from eight patients reacted with both protein I and LPS, whereas sera from four reacted only with protein I, and one sera reacted with LPS alone. One serum with antibody to both protein I and LPS by Western blot analysis was tested for bactericidal activity before and after adsorption of antibody to LPS. Removal of antibody to LPS reduced the bactericidal titer of this serum from 1:100 to 1:50, indicating that antibody to both antigens may be bactericidal for Neisseria gonorrhoeae.

Antibodies to gonococcal pili in women with asymptomatic gonorrhoea. Diagnostic value of the ELISA for testing women attending an STD clinic

The diagnostic efficacy of an enzyme-linked immunosorbent assay (ELISA) using gonococcal pili 6650 as antigen was studied in asymptomatic women attending an STD clinic. Of the 182 women studied, gonorrhoea was diagnosed in 29%. The value of the ELISA was calculated on the basis of four arbitrary cut-off points in the test. The best predictive values for a positive result (PV(+)) were obtained at an absorbance value of A greater than or equal to 1.15 and A greater than or equal to 1.30 and that for a negative result at A greater than or equal to 0.85. When patients with a history of gonorrhoea were excluded, the PV(+) rose only at A greater than or equal to 1.15 (not at A greater than or equal to 1.30) and the PV(-) rose slightly. To be of use in the diagnosis of gonorrhoea in asymptomatic patients the ELISA should be used as follows: the result is positive at A greater than or equal to 1.15 and negative at A less than 0.85, the PV(+) then being 0.52 and the PV(-) 0.85. Whenever sera give a result between A = 0.85 and A = 1.15, the test should be repeated.

Enzyme-linked immunosorbent assay for detecting gonococcal antibodies using two antigenically different gonococcal pili as antigen

Antibodies to pilar antigens of two gonococcal strains isolated in Rotterdam (6650 and 1443) were detected using enzyme-linked immunosorbent assays (ELISA). Paired sera (the first sample taken at the first examination (D1) and the second 11-22 days later (D2)) from women with and without gonorrhoea attending a sexually transmitted disease (STD) clinic were studied. The sensitivity of the ELISA using gonococcal pili 6650 as antigen (ELISA 6650) was significantly higher than that using gonococcal pili 1443 as antigen (ELISA 1443). The specificity of the two tests differed little. On D1 the sensitivity in women with uncomplicated gonorrhoea was 69% in the ELISA 6650 and 45% in the ELISA 1443; the corresponding values in asymptomatic infected women were 75% and 57% respectively. The agreement (both in positive and in negative results) between the two tests was less than might have been expected (kappa = 0.41).

Chemical and immunological comparison of surface fibrils of strains representing six taxonomic groups of Actinomyces viscosus and Actinomyces naeslundii

Human isolates of Actinomyces viscosus and Actinomyces naeslundii have been divided into six clusters in a numerical taxonomy study. Surface fibrils of strains representing these clusters were isolated and purified. Chemical analyses revealed that the major component of all fibrils was protein and that although differences in percentages of specific amino acid residues were found, the relative proportions of basic, acidic, polar uncharged, and nonpolar amino acids were rather similar among clusters. All of the fibrils except those from strain B236 (cluster 2) either failed to migrate or penetrated only slightly into gels during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, even after boiling, reduction, or alkylation. Immunological studies by electron microscopic examination of fibril-antibody immunocomplexes, whole bacterial cell agglutination, inhibition of hemagglutination, and immunofluorescence by using antifibril antisera and antibodies demonstrated that strains of typical A. naeslundii (cluster 5) have a specific fibril-associated antigen(s) distinct from those of strains of other clusters. Cross-reactions for atypical A. naeslundii (cluster 3) were few. The fibrils from A. viscosus clusters 1, 2, 4, and 6 demonstrated several cross-reactions. By absorbing antifibril antibodies with cross-reactive strains it was possible to obtain cluster-specific antibodies, as determined by whole cell agglutination, only for cluster 5. Absorbed antifibril antisera for both A. naeslundii clusters 3 and 5 were specific by indirect immunofluorescence, whereas anti-cluster 1 fibril antisera cross-reacted only with other A. viscosus cluster representatives. Purification of Actinomyces fibrils by methods used for appendages of other species yields preparations containing common antigens among taxonomic groups. However, absorbing antifibril antisera, gamma globulin, or both has promise for producing cluster-specific reagents useful in identification.

Gonococcal serology. A comparison of three different tests

Three serological tests for the detection of gonococcal antibodies were compared: an enzyme-linked immunosorbent assay (ELISA), an indirect haemagglutination reaction (IHA), and a gonococcal complement-fixation test (GCFT). The ELISA was performed with gonococcal pili of a Rotterdam strain (1443) as antigen, the IHA with pilus antigen of an American strain (2686, Buchanan), and the GCFT with whole gonococci of a single strain (46695, Oliver) as antigen. The tests were performed on sera from the same groups of Dutch patients; samples of sera were taken at the first examination and generally 11-22 days later. The ELISA and the IHA were more sensitive than the GCFT. The specificity of the tests was equal in low-risk groups, but the GCFT was slightly more specific in high-risk groups. The ELISA and the IHA did not differ in sensitivity and specificity. The agreement between the ELISA and IHA for patients with uncomplicated gonorrhoea was low (chi = 0.44), but the agreement between the GCFT and the two pilus assays was less (chi = 0.26 and 0.20). The sensitivities were highest for sera from patients with oropharyngeal gonorrhoea or with gonococcal complications; again the ELISA and the IHA were more sensitive than the GCFT.

Passive hemagglutination test for detection of antibody to gonococcal ribosomal antigen in sera from patients with asymptomatic gonorrhea

Ribosomal fractions were obtained from a culture of type 2 Neisseria gonorrhoeae strain P-17 which was isolated from a patient with an acute gonococcal infection; these fractions were purified to eliminate the components of the outer membrane complex by affinity chromatography (Sepharose-anti-outer membrane complex antibody conjugates were used as the solid immunosorbent), and the resulting preparation was designated the purified ribosomal fraction, The purified ribosomal fraction was used to detect antibody activity in sera obtained from culture-positive asymptomatic carriers and healthy controls by a passive hemagglutination test. This passive hemagglutination test had a specificity of 100% for both sexes and sensitivities of 99.4 and 88.2% for female and male carriers, respectively, when an antibody titer of more than 1:3 was defined as abnormal. Absorption of the sera with nongonococcal organisms did not affect the antibody activity, and no significant difference in antigenicity among various N. gonorrhoeae strains was observed in ribosomal fractions. An enzyme-linked immunosorbent assay was also used to measure the relative amounts of specific antibodies to the purified ribosomal fraction, and this assay revealed that the anti-purified ribosomal fraction antibodies were immunoglobulin G.

Demonstration of antigenic heterogeneity of Neisseria gonorrhoeae pili antigens using human sera in the test system

Antigenic heterogeneity of gonococcal pili using human sera in the test system was demonstrated by means of indirect haemagglutination (IHA) inhibition studies. The reactivities of sera from 104 females with current gonococcal infection were compared by the IHA test using different pili preparations as antigens. Sera and gonococcal strains were collected from 365 patients. Pili were purified from strains infecting patients who met the following three requirements: 1) no history of previous gonococcal infection(s), 2) an infection that had lasted a week or more, 3) a seronegative result when tested by the IHA test using pili from Buchanan's strain 2686 as antigen. Each patient's serum was tested against pili produced by the gonococcal strain infecting this particular patient. A seropositive reaction obtained by using pili antigen from the strain infecting the seronegative (strain 2686) patient indicates an antigenically heterogeneous pili preparation. Two such strains, antigenically different from one another and from strain 2686, were found among 22 pili preparations investigated.

Enzyme-linked immunosorbent assay (ELISA) to detect antibodies in gonorrhea using whole cells

The choice of an antigen that will adequately differentiate between infected and non-infected patients has been a problem in detecting gonococcal antibodies for diagnosis. We have used the sensitive technique of ELISA to test various serotypes of Neisseria gonorrhoeae for their suitability as antigens. Whole cells of each serotype were attached to polystyrene plates using poly-L-lysine, N gonorrhoeae, strain H1 type 1 was used to detect antibodies in patients with known clinical history and then as a standard to evaluate the ability of different serotypes to differentiate between infected and non-infected groups.

Purification and characterization of surface fibrils from taxonomically typical Actinomyces viscosus WVU627

Fibrils of Actinomyces viscosus WVU627 (numerical taxonomy cluster 1) were obtained by homogenization and purified by ultrafiltration, ammonium sulfate precipitations, gel filtration, and ion-exchange chromatography. Electron microscopy and resolution of a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis attested to the purity of the preparation. Purified fibrils were composed mainly of protein; small quantities of carbohydrate and phosphorus were detected. Immunoelectrophoresis revealed only a single precipitable antigen, which migrated slightly toward the anode, in reactions between purified fibrils and antiserum raised against either whole bacterial cells or the purified fibrils themselves. Immunoelectron microscopy with ferritin-conjugated antifibril antibody hemagglutination inhibition, and bacterial agglutination tests demonstrated that fibrils of Actinomyces viscosus cluster 1 strains shared some common antigens with clusters 2, 3, 4 and 6, but did not cross-react with typical Actinomyces naeslundii of cluster 5. Stability tests revealed that after heat or alkali treatment, the fibrils lost their antigenicity and disappeared from electron micrographs. They were affected less by sodium dodecyl sulfate, sonic, or acid treatments.

Disseminated gonococcal infection (DGI) and gonococcal arthritis (GCA): II. Clinical manifestations, diagnosis, complications, treatment, and prevention

This is the second part of an integrated review of disseminated gonococcal infection (DGI) and gonococcal arthritis (GCA). It covers clinical manifestations, spectrum of GCA, diagnosis and treatment. These disorders are important since DGI may be the most frequent form of acute arthritis in sexually active younger females, and other selected groups. Although the spectrum of disease is varied, it may be classified into stages and clinical subgroups. N. gonorrhoeae strains causing DGI in the U.S. have been highly sensitive to penicillin. Such findings require revision in beliefs that high-dose intravenous penicillin is needed for effective initial therapy of GCA. Recommended treatment protocols for localized gonorrhea and DGI are reviewed as well as the occurrence and implications for treatment of penicillinase-producing N. gonorrhoeae (PPNG) infection in the U.S.

Local immune response to Escherichia coli pili in experimental pyelonephritis

The local immune response to pili of Escherichia coli O6:K13:H1 was determined in experimental hematogenous pyelonephritis in rabbits. Pili purified from sheared cells by ammonium sulfate precipitation were found to be pure by electron microscopy and negative for lipopolysaccharide by limulus lysate assay. Antipilus antibody was detected in serum and newly synthesized protein from infected animals with enzyme-linked immunosorbent assay. Serum and local (intrarenal) antibodies were of the immunoglobulin G class, were detectable by day 20 of infection, and persisted though 250 days of infection. These data suggest that pili are present on the organism at the site of infection, since they induce the local synthesis of antipilus antibody in experimental pyelonephritis.

Gonococcal salpingitis is less likely to recur with Neisseria gonorrhoeae of the same principal outer membrane protein antigenic type

If protective immunity were to develop following an episode of gonococcal pelvic inflammatory disease (salpingitis), PID should recur with organisms bearing antigens that do not react with these immune mechanisms. To test this hypothesis, gonococci from 15 women with gonococcal PID, who experienced 19 subsequent episodes of gonococcal infection, were serotyped for their principal outer membrane protein (Protein I) antigens. Of nine cases in which the initial and subsequent infections involved the same Protein I serotype, none was associated with recurrence of PID. Of 10 cases in which the initial and subsequent infections involved different Protein I types, five were associated with recurrent PID (p = 0.02). These data suggest that an episode of gonococcal PID produces some immunity to repeated episodes of salpingitis with the same Protein I serotype, while not preventing reinfection with the same Protein I serotype. The immune response to Protein I antigen may thus provide serotype-specific protection against gonococcal salpingitis.

An indirect haemagglutination test for demonstration of gonococcal antibodies using gonococcal pili as antigen. II. Serological investigation of patients attending a dermato-venereological outpatients clinic in Copenhagen

A total of 1223 serum specimens were obtained from 649 consecutive patients attending a dermatovenereological out-patient clinic in Copenhagen with a request for venereal disease control. The sera were examined for gonococcal antibodies by both a gonococcal complement fixation test (GCF) and an indirect haemagglutination test using gonococcal pili as antigens (IHA). The diagnosis of current gonococcal infection in 28 per cent of the patients was based on positive culture for Neisseria gonorrhoeae from one or more of the following sites: urethra, rectum and fauces in all patients, and/or cervix in female patients. The specificity, sensitivity and predictive values of positive and negative test results were calculated for the various groups of patients on the assumption that all positive results, both in patients without gonorrhoea but with a previous gonococcal infection and in patients without known current or previous infection, were false positives. The following values were found: Sensitivity: IHA 45-100%, GCF 6-29%. Specificity: IHA 65-89%, GCF 97-100%. Predictive value of positive test result: IHA 43-74%, GCF 69-100%. Predictive value of negative test result: IHA 78-100%, GCF 61-85%.

High-molecular-weight antigenic protein complex in the outer membrane of Neisseria gonorrhoeae

The outer membrane of Neisseria gonorrhoeae contains approximately 15 proteins, with 2 or 3 accounting for over 75% of the total protein mass. Samples of outer membrane from strain 2686 T4 analyzed by electrophoresis in 2% polyacrylamide gels revealed a band with an apparent molecular weight of 800,000. The band was protein material, as indicated by trypsin and pronase sensitivity and by L-[3H]proline incorporation. Peptidoglycan, nucleic acids, and carbohydrate were not detected in the band. Dye binding, L-[3H]proline incorporation, and labeling of solubilized outer-membrane proteins with 125I-labeled Bolton-Hunter reagent indicated that the band made up 10 to 13% of the total protein mass of isolated outer membranes. The material in the band was purified by gel filtration and, after reduction and alkylation, quantitatively recovered as subunits with an apparent molecular weight of 76,000. The protein in complex form was exposed at the cell surface, as evidenced by labeling whole cells with 125I by using a lactoperoxidase-catalyzed reaction and with CNBr-activated dextran. Rabbit serum raised against whole 2686 T4 gonococci contained antibody which reacted with the protein complex. The protein complex was detected in all gonococcal strains tested, but its presence could not be demonstrated in several other gram-negative species.

Serologic diagnosis of gonococcal infection

Infection with N. gonorrhoeae stimulates the production of antibodies to many common, species-specific, and type-specific antigens. The L-antigen is an envelop antigen and antibodies to it could be demonstrated by various methods in more than 90% of the patients after the first 10 days of infection. Serologic tests are not yet available in the United States. If and when they become available, they may be recommended for: (1) Screening asymptomatic men and women, (2) Use as an adjunct diagnostic tool in cases of prostatitis, arthritis, disseminated gonococcal infection, and pelvic inflammatory disease, (3) Use (alone or in conjunction with culture) when specimens must be mailed to a central laboratory, when mailing conditions do not allow for incubation within 24-48 hr, or when proper media and qualified bacteriologists are not available.

Gonococcal urethritis--diagnosis and treatment

For men with urethral discharge, a simple gram stained smear is 98% sensitive and over 99% specific in detecting gonococcal infection when compared to a single Thayer-Martin culture. The smear is less than 50% sensitive in asymptomatic urethritis. Neither Fluorescent antibody nor various serologic tests offer any diagnostic advantages over smears and/or cultures and they are not cost-effective. Treatment of gonococcal urethritis may be successfully accomplished with a variety of antibiotic regimens. Tetracycline hydrochloride (500 mg four times a day for 5 days) is highly effective, inexpensive, and is active against Chlamydia trachomatis; post gonococcal urethritis (PGU) is therefore uncommon. Aqueous Procaine Penicillin G (4.8 million units IM with 1 g of probenecid) has become the standard in the United States but suffers from higher cost, the need for refrigeration, occasional alarming toxic procaine reactions, and a high incidence of PGU. Spectinomycin 2 g IM remains expensive but is the regimen of choice for treatment failures and for Neisseria gonorrhoeae that produce penicillinase (PPNG). Other antibiotics active against PPNG are cotrimoxozole, cefoxitin, and cefuroxime. PNNG have now been reported from 27 countries throughout the world, but have attained significant prevalence in only a few areas of East Asia and West Africa. Because gonococcal patterns of antibiotic resistance are constantly changing, each region of the world needs to monitor treatment results and maintain some surveillance over sensitivity to antibiotics.

Attachment of Neisseria gonorrhoeae to human sperm. Microscopical study of trypsin and iron

Pilated Neisseria gonorrhoeae of colony type 1 (T1) and non-pilated bacteria of colony type 4 (T4) were observed by transmission (TEM) and scanning electron microscopy (SEM). No pili were observed on T4 gonogocci, but two types of pili--straight, type a, and bent, type b--were seen on T1 by TEM. When incubated with human sperum and examined by either TEM or SEM, T1 gonococci were seen to attach by individual pili, by several pili wound together as a rope, or by direct contact. Gonococci from T4 colonies attached only by direct contact. Treatment with typsin (1 mg/ml) damaged or removed pili from gonococci. After incubation with trypsin, attachment of pilated gonococci to sperm was decreased significantly, but such treatment did not affect attachment of non-pilated gonococci. Incubation of gonococci from either colony type in 0.1 mmol/l ferric nitrate, followed by incubation with sperm, significantly increased attachment of only T4 bacteria. No pili were seen on T4 gonococci treated with ferric nitrate; thus, it appears that factors other than pili alone are concerned in attachment of these gonococci to sperm.

Antigenic polypeptide complex from the Melvin strain of Neisseria gonorrhoeae: isolation and properties

An antigenic complex has been isolated in a highly purified from from the Melvin strain of Neisseria gonorrhoeae. The complex has a molecular weight of 9.3 x 10(6) and on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was found to consist of several subunits; the most predominant had the following molecular weights: 110,000, 94,000, 68,000, a smear containing (52,000, 48,000, and 44,000), 42,000, 36,000, 29,000, 28,000, 26,000, and 12,000 comprising 89% of the total protein. With the exception of the subunit of molecular weight 110,000, no change in the content or the mobility of other subunits was observed when beta-mercaptoethanol was omitted from the denaturation solution of sodium dodecyl sulfate electrophoresis. Amino acid analysis of the complex showed a predominance of hydrophobic amino acids. These data implicated noncovalent interactions between the subunits. When the cells were labeled with fluorescamine it was possible to obtain a fluorescent complex with identical properties. Among several buffers used for the isolation of the complex, 0.2 M tris(hydroxymethyl)aminomethane buffer (pH 7.5) gave maximum yield with low amounts of lipopolysaccharide and phospholipid; the choice of the buffer for column chromatography did not seem to make any difference. The high protein content and low amounts of lipopolysaccharide and phospholipid are characteristic properties of the complex.

Dual-isotope separation technique for radioassay. Precision of calculated results affected by degree of separation

The dual-isotope separation technique for radioassay is reviewed. An expression is derived describing the effect of counting errors on the precision of the calculated bound count rate in the dual-isotope technique. This mathematic model is tested in experiments using sodium iothalamate (I-125) as a marker in the Phadebas radiosorbent assay of cobalamin (Co-57). The coefficient of variation of results calculated on the basis of the dual-isotope technique is shown to be dependent on the amount of supernatant removed. The conclusion is that relatively large amounts of the supernatant must be removed before counting if the dual-isotope technique is to give acceptable results. The experimental model is proposed as a simple test of the suitability of a projected dual-isotope system.

The biology of the gonococcus

Gonorrhea has been known since antiquity. Today, this disease is the most commonly reported infectious disease in the U.S. The natural environment of the etiological agent, Neisseria gonorrhoeae, is man. In this host, the organism usually parasitizes mucosal surfaces populated by columnar epithelial cells. Under certain conditions, the gonococcus may disseminate or spread to adjacent organs. The gonococcus is well adapted to its environment and is a successful parasite. Until recently, gonococci were uniformly sensitive to penicilin. However, a plasmid encoding beta-lactamase has been identified in some isolates. Most strains exhibit specific requirements for various amino acids, vitamins, purines, and pyrimidines. Only glucose, pyruvate, and lactate are utilized as sources of energy. Glucose is dissimilated by a combination of the Entner-Doudoroff and pentose phosphate pathways. A tricarboxylic acid cycle is also present and active under certain conditions. Structurally, the cell envelope of the gonococcus resembles that of a typical Gram-negative bacterium. Gonococci are highly autolytic, especially in older cultures or after depletion of the energy source. Autolysis is not due solely to peptidoglycan hydrolysis, but appears to involve a destabilization of the outer membrane as well. Cell surface components such as pili, lipopolysaccharide, outer membrane proteins, and a capsule are associated with the virulence and pathogenicity of this organism.

Studies on gonococcus infection. XVI. Purification of Neisseria gonorrhoeae immunoglobulin A1 protease

A protease which cleaves human immunoglobulin A1 (IgA1) has been purified from broth cultures of Neisseria gonorrhoeae. This IgA1 protease is produced by pilated and nonpilated gonococci throughout their growth cycles. A combination of ammonium sulfate precipitation, column chromatography, and either isoelectric focusing or affinity chromatography was utilized to obtain an enzyme preparation that showed approximately 3,800-fold purification and exhibited two bands (65,000 and 70,000 daltons) by analytical polyacrylamide electrophoresis in the presence of sodium dodecyl sulfate and reducing conditions. IgA1 protease activity is dependent on divalent cations and is heat labile. Detection and quantitation of IgA protease activity utilized an assay in which [125I]IgA1 is incubated with protease preparations and the cleavage products are analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Antigenic characterisitcs of Moraxella nonliquefaciens fimbriae in double immunodiffusion

Rabbit antisera against purified fimbriae (pili) from Moraxella nonliquefaciens detected three fimbrial antigenic components, one or two of which appeared to be present in other fimbriated strains of M. nonliquefaciens and the closely related M. bovis. Maximal precipitation with the antisera required some denaturation of the antigen. Ultrasonication, repeated freeze-thawing, heating, and agents like KBr, NaSCN and urea were effective in liberating the antigen in diffusible forms. The morphology of the fimbriae was altered by heat treatment in 1 M KBr.

Benign meningococcemia in childhood. A report of five cases with clinical and diagnostic remarks

Five children aged 1/2--10 years with benign meningococcemia are reported. The clinical picture was quite uniform: good general condition, spikes of fever, skin eruptions as maculopapules--sometimes haemorrhagic, appearing in association with febrile periods, and arthralgia (big joints). The diagnosis involves either isolation of meningococci (MC) from blood, demonstration of MC with immunofluorescence in skin eruptions, or a significant elevation of MC antibody titre in connection with typical clinical signs and symptoms. Important differential diagnoses are Henoch-Schönlein syndrome, disseminated gonococcal infection, septicemia of other origins, subacute bacterial endocarditis, viral infections, hypersensitivity reactions and subsepsis allergica. By co-agglutination technique, the causative agent of meningococcemia in 4 of the 5 children was shown to be MC group B. These have some features in common with gonococci, whereby an incorrect diagnosis might be suggested as demonstrated in one of our patients. The question is raised whether MC group B is the main causative agent in benign meningococcemia.

Serological diagnosis of gonorrhoea by an enzyme-linked immunosorbent assay (Elisa)

IgG antibody to an outer membrane protein extracted from Neisseria gonorrhoeae was measured in patients with gonorrhoea. The level in such patients was significantly higher than in normal controls or in patients with other conditions who were attending the clinic for sexually transmitted diseases. Significantly higher antibody levels were detectable in half the patients within a few days of infection and in a similar proportion of carriers--both male and female. Men with rectal gonorrhoea had particularly high antibody levels. Sixteen per cent of presumptively normal men and 11% of normal women gave positive results but the actual false positive rate could be lower.

Attachment role of gonococcal pili. Optimum conditions and quantitation of adherence of isolated pili to human cells in vitro

Gonoccocal pili facilitate attachment of virulent Neisseria gonorrhoeae to human cells. To characterize this attachment function, purified gonococcal pili isolated from four strains possessing antigenically distinct pili were radiolabeled with 125I and used to measure the attachment of pili to various human cells in vitro. Human buccal and cervical-vaginal mucosal epithealial cells, fallopian tube mucosa, and sperm bound pili in greater numbers per micrometer2 of surface area (1--10) than fetal tonsil fibroblasts, HeLa M cells, erythrocytes, or polymorphonuclear leukocytes. This cell specificity of attachment suggests a greater density of membrane pili binding sites on cells similar or identical to cells from natural sites of infection. The pili binding sites were quantitated as 1 X 10(4) per cervical-vaginal squamous cell. Pili of all antigenic types attached equally to a given cell type, implying that the attachment moiety of each pilus was similar. Attachement of gonoccocal pili to human cells occurred quickly with saturation of presumed receptor sites within 20--60 min. Attachment was temperature dependent (37 degrees greater than 20 degrees greater than 4 degrees C), and pH dependent (3.5 less than 4.5 less than 5.5 less than 7.5). Attachment was inhibited by antibody to pili (homologous pili Ab greater than heterologous Ab). The extent of possible protection against gonococcal infection due to inhibition of pili-mediated attachment might prove limited as a result of the considerable antigenic heterogeneity among pili and the observation that blockage of pili attachment is maximal only with antibody to pili of the infecting strain.

Inhibition of Neisseria gonorrhoeae by aerobic and facultatively anaerobic components of the endocervical flora: evidence for a protective effect against infection

The ability of aerobic and facultatively anaerobic endocervical flora to inhibit the growth of Neisseria gonorrhoeae in vitro was assayed. Factors influencing the occurrence of inhibitory components of the flora in vivo were evaluated. Endocervical swabs were obtained from 229 women at a local venereal disease clinic. Endocervical flora and N. gonorrhoeae were isolated and identified, and the ability of the flora to inhibit the growth of N. gonorrhoeae was determined by an agar overlay assay. Results revealed the most active inhibitors to be streptococci, staphylococci, and lactobacilli, in that order. Among only those women harboring inhibitory endocervical flora, inhibitory lactobacilli were recovered from fewer women infected with N. gonorrhoeae than uninfected women (P less than 0.05). Among women having contact with an infected partner, those who subsequently developed gonorrhea were less likely to have inhibitory lactobacilli than those who did not become infected (P less than 0.05). No other significant differences in the composition of the inhibitory flora were noted between infected and uninfected women. During the 2 weeks following menses, recovery of inhibitory lactobacilli on culture was highest, whereas recovery of N. gonorrhoeae was lowest. These observations suggest that the presence of certain lactobacilli may reduce risk of acquisition of N. gonorrhoeae following exposure to infected partners and that the potential protective effect may be greatest during the 2 weeks after menses.

Genetic transformation of pilation and virulence into Neisseria gonorrhoeae T4

Genetic transformation of nonpilated strains of Neisserai gonorrhoeae to pilated forms is described. The transformants displayed phenotypic T1 and T2 colonial morphology on agar and possessed pili visualized by electron microscopy. When T1 or T2 transformant cells were injected into 11-day-old chicken embryos, they exhibited virulence characteristics only slightly less than the parental donor strains, though the parental recipient strains were avirulent. Competence was maximal in the late log phase of growth, and the frequency of transformation of clonal T4s to pilation and virulence approached 2%. DNA extracted from transformants could be used to transform other T4 cells. In the course of this work, a shift to a novel colonial type, designated T2-T3 wrinkled, was observed as a consequence of growth of T4 in presence of enzymatic digests of either DNA or RNA, nucleases or individual deoxy- or ribonucleosides. In sharp distinction to the parental T4, these novel organisms were very pilated; however, they were only minimally virulent. Various nucleic acid analogs could neither induce nor inhibit this population shift. Additionally, DNA extracted from this T2-T3 wrinkled variant could be used to transform genetically both T1 and T4 gonococci to the new morphology.