Immunochemical characterization of aqueous ether extracted endotoxin from Neisseria gonorrhoeae

The immunochemistry of neisserial LOS

The outer membrane glycolipids of Neisseria lack long polysaccharides and are properly termed lipooligosaccharides (LOS). A Neisseria strain makes from two to six LOS of Mr 3150-7100. Different species commonly make LOS of identical Mr and epitope content. Oligosaccharide (OS) differences account for physical heterogeneity. OS consist of a conserved triantenary basal oligosaccharide, two linear segments of (n) hexose residues that determine OS mass, and terminal sequences similar to those of glycosphyngolipids. Epitope expression is linked to physical heterogeneity and conditioned by the molecular environment of the outer membrane. Serotype epitopes are expressed on Mr-restricted LOS. LOS regulate complement activation onto the bacterial surface and, hence, immune lysis.

Serology of Neisseria gonorrhoeae. Classification by co-agglutination

The co-agglutination (COA) method has been adapted for serological classification of Neisseria gonorrhoeae. COA reagents were prepared with selectively absorbed rabbit hyperimmune antibodies against gonoccal (GC) major outer membrane protein (MOMP) serotype strains. Using these reagents, the 16 MOMP reference strains could be referred to at least three antigen classes, tentatively named W, J and M. The GC antigens of class W were divided into three groups I, II and III, and they were in part sensitive to pronase. The antigens of class J reflected strain specific or serotype reactions, some sensitive and others resistant to proteolytic enzymes. The antigens of class M were sensitive to periodate and resistant to pronase. Strains used in serological studies by other authors were tested. The properties of class W correlated well with those of the so-called micro-immunofluorescence and immunotype systems, and class M with those of the so-called endotoxin and acid polysaccharide systems. Strains from three different laboratories could all be grouped by class W and M reagents. Identical strains obtained independently from different laboratories gave very similar reaction patterns with the reagents available. Repeated GC-isolates from patients infected with beta-lactamase producing strains showed stable reactions with class W and J reagents, while there was a time-related variation of the class M pattern. We have found that the COA method is rapid, easy and reproducible in the serological classification of Neisseria gonorrhoeae and all the 117 GC-strains tested could be classified.

Pneumonia in mice produced by Neisseria gonorrhoeae

Gonococci of colony type 1 were introduced by intranasal inoculation into the lungs of mice in an attempt to produce infection. The organisms were eliminated from the three strains of mice used within 24 hours of challenge. Cyclophosphamide treatment of mice failed to render them susceptible although the organisms disappeared more slowly. The lungs of immunologically normal animals that had received either viable or heat-killed gonococci were acutely inflamed with infiltration of bronchioles and alveoli by polymorphonuclear and mononuclear leucocytes. Most of the changes had resolved after about four days. In cyclophosphamide-treated mice pulmonary infiltration by polymorphonuclear leucocytes was not evident, suggesting that these cells were not primarily responsible for the clearance of the gonococci. Despite the failure to produce a sustained infection, this model may be valuable for studying the local inflammatory effect of gonococcal endotoxin.

Cell envelope of Neisseria gonorrhoeae: outer membrane and peptidoglycan composition of penicillin-sensitive and-resistant strains

The cell envelope of Neisseria gonorrhoeae, colony type 4, was studied. Outer membrane was isolated by lysozyme and ethylenediaminetetraacetic acid treatment of plasmolyzed cells according to Wolf-Watz et al. (1973). The degree of purity of the membrane preparations was checked by electron microscopy. The membrane fraction obtained had a density of 1.25 g/cm(3), was rich in phospholipase A and lysophospholipase, and contained only 10% of the total membrane activity of succinate dehydrogenase and d-lactate dehydrogenase. The outer membrane protein profile after sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed at least six major proteins. The predominating protein showed a molecular weight of 35,000. The lipopolysaccharide component was characterized by gas chromatography. The carbohydrates found were galactose, glucose, and glucosamine. d-Glycero-l-manno-heptose was present in very low amounts. Lipid A contained lauric acid, stearic acid, and beta-hydroxy-myristic acid. About 20% of the fatty acids in the outer membrane was derived from lipid A. The phospholipids were characterized as phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. There was no evidence for a lipoprotein anchored to the peptidoglycan. The peptidoglycan of N. gonorrhoeae was of the chemotype I. The cell envelope of N. gonorrhoeae was found to be highly permeable to gentian violet. Cell envelopes of one penicillin-resistant and two penicillin-sensitive strains were compared. Only moderate differences in fatty acid composition were found.

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

Gonococcal pili, pure by the criteria of electron microscopic examination and polyacrylamide gel electrophoresis in sodium dodecyl sulfate, have been prepared by repeated cycles of precipitation with 0.1 M MgCl(2), followed by dissolution in 0.01 M Tris pH 8, 0.01 M NaN(3). Using a fluorescein-conjugated antibody prepared to pili from a single strain, pilar antigen(s) was found to be present in each of 18 strains of gonococci tested, and absent from strains of pilated meningococci, nonpathogenic Neisseria sp., and Escherichia coli. Purified pili, labeled with (125)I were used in an antigen binding assay to quantitatively measure antibody to pili in rabbit sera and in 561 human sera. The range of antibody activity for 133 persons unlikely to have experienced gonorrhea was 0.1-1.6 mug/ml with a geometric mean of 0.5 mug/ml. This geometric mean antibody activity was significantly lower than the geometric mean for asymptomatically infected males (1.0 mug/ml, P < 0.002), males with symptomatic gonococcal anterior urethritis (1.6 mug/ml, P < 0.001), or asymptomatically infected females (4.2 mug/ml, P < 0.001). Antibody appeared in elevated levels (> 1.6 mug/ml) 2-3 wk after infection and returned toward control levels 1 or more months after treatment. Antibody levels higher than 1.6 mug/ml were found in 26 (50%) of 52 males with gonococcal anterior urethritis, in 10 (33%) of 30 males with asymptomatic urethral infection and in 50 (89%) of 56 asymptomatically infected females. In a high-risk group of 103 females for whom culture results and antibody to pili were compared, 58 (57%) had elevated antibody levels to pili and 86% of the infected females were within this seropositive group. The antigen binding assay may provide a means to detect asymptomatic gonococcal infection in women.

Isolation and characterization of the antigen of Neisseria gonorrhoeae

The beta antigen of Neisseria gonorrhoeae has been isolated from the alkaline-extracted gonococcal endotoxin by ion exchange, molecular sieve, and powder block electrophoretic chromatography. Hemagglutination inhibition studies indicate that the preparation is essentially free of common enterobacterial and gonococcal alpha antigen. Analysis of the isolated antigen by immunodiffusion and acrylamide gel electrophoresis reveal only one detectable component. Chemical studies indicate that the antigen is an acidic glycoprotein composed primarily of four major amino acids: alanine, glutamic acid, glycine, and proline. The antigen has an s(20,w) of 8.55, and spectral analysis in the ultraviolet and visible range reveals a single absorption peak at 217 nm.