Latent syphilis: immunoglobulins reactive in immunofluorescence and other serological tests.

Study of sera from 69 patients with untreated or inadequately treated latent syphilis revealed that immunoglobulin (Ig)G antibodies made up the bulk of the fluorescent treponemal antibody-absorption (FTA-ABS)-test reactivity found in the sera. IgM and IgA antibodies also contributed in some cases. Venereal Disease Research Laboratory slide-test reactivity was found in both 19 and 7S serum fractions, whereas Treponema pallidum immobilization-test reactivity was found mainly in the 7S fraction.

Reactivity of two gonococcal antigens in an automated microhemagglutination procedure.

In studies of several hundred sera, a passive-hemagglutination technique with soluble antigen of sonically treated gonococci as the sensitizing material for tanned erythrocytes and Neisseria sicca sonically treated material as an absorbent detected gonococcal antibodies in 77% of males and 88% of females infected with uncomplicated gonorrhea. However, 6% of the sera from individuals in celibate religious orders and 18% of the sera from a group of females having cervical cultures negative for gonococci were also reactive with this procedure. Erythrocytes sensitized with an alkaline extract of gonococci reacted with 23% of the sera from infected males, 49% of the sera from infected females, and 2% of the sera from celibate females.

Immunoglobulin Class of Natural Human Antibodies Reactive with Treponema pallidum.

To aid the development of serological tests for incubating syphilis, a characterization was made of the background of natural anti-Treponema pallidum antibodies against which the initial immune response to syphilis takes place. Sera from presumed normal persons were studied with monospecific antisera in an indirect fluorescent-antibody procedure. Of 36 sera tested at a 1:5 dilution, all showed IgG reactivity with T. pallidum (Nichols strain), 58% showed IgM reactivity, and 20% showed IgA reactivity. The titer of IgG reactivity was considerably higher than that of the other two immunoglobulins. Heating the sera for 1 hr at 65 C abolished IgA and IgM anti-T. pallidum reactivity, but one-third of the sera retained IgG reactivity. Human Cohn fractions II and III(1) from three commercial sources contained mostly IgG antibodies reactive with T. pallidum, but IgM and IgA antibodies were also present. IgG reactivity was found in a pool of presumably normal maternal sera from 20 mothers and in a corresponding pool of umbilical cord serum from their infants. IgM and IgA reactivities were present only in the maternal serum pool.

Automated, quantitative microhemagglutination assay for Treponema pallidum antibodies.

An automated, quantitative microhemagglutination assay for antibodies to Treponema pallidum was developed by using T. pallidum-sensitized erythrocytes and an automatic serial-dilution instrument. Reactivity was found in sera from 54 rabbits and 6 chimpanzees infected with T. pallidum. Reactivity was also found in sera from animals infected with T. pertenue, T. carateum, and T. cuniculi. No reactivity was found in sera from 75 normal rabbits or from 129 rabbits immunized with cultivatable treponemes or a variety of other bacteria. In approximately 3 min, 13 twofold serial dilutions of each of 8 preabsorbed sera and the addition of sensitized erythrocytes to each dilution were accomplished automatically. The automated assay can serve as a research tool in quantitating antibodies to pathogenic treponemes, and evaluation of its clinical usefulness seems warranted.

Neisseria gonorrhoeae. II. Colonial variation and pathogenicity during 35 months in vitro.

During 35 months of selective in vitro cultivation, Neisseria gonorrhoeae cells retained their virulence for humans and were shown to be closely related to a particular colonial morphology. Saline-autoagglutinability was the only other characteristic distinguishing virulent from avirulent cells. Human responses to challenge with cells of the different colonial types were studied for their relationships to virulence or avirulence.

Antibiodies of the IgG, IgM, and IgA classes in newborn and adult sera reactive with gram-negative bacteria.

Umbilical cord serum and adult serum antibodies reactive with heat-stable somatic antigens of Gram-negative bacteria (Neisseria gonorrhoeae, Escherichia coli, and Salmonella typhosa) were assayed by using an indirect fluorescent antibody test. Reactive IgG, IgM, and IgA antibodies were identified by using fluoresceinconjugated antisera specific for these immunoglobulin classes.IgG antibody titers in cord serum approximated those found in the corresponding maternal sera. IgM and IgA antibodies were present in adult sera but were not demonstrable or were present only in small amounts in cord sera. The presence of IgG and IgM antibodies reactive with Gram-negative bacteria was confirmed by the testing of purified 7S and 19S fractions. In addition, both IgG and IgM reactivities were inhibited by the prior incubation of serum with purified specific lipopolysaccharide preparations. The ubiquity and magnitude of these natural IgG antibodies in the sera of both adults and neonates have apparently eluded detection in previous studies. The use of bactericidal and agglutination tests, which are apparently more sensitive to the presence of IgM than to IgG antibodies, may account for the failure of previous studies to detect adult and cord IgG antibodies reactive with somatic antigens of Gram-negative bacteria. The presence of these IgG antibodies may be correlated with the resistance to infection demonstrated by most newborns as they are challenged by the septic extrauterine environment.

The fluorescent treponemal antibody-absorption (FTA-ABS) test. Development, use and present status.

For testing problem sera, the fluorescent treponemal antibody-absorption test (FTA-ABS) is increasingly replacing other treponemal tests for syphilis (including the TPI test) in the USA. The authors review its development as a result of experience with other immunofluorescent techniques and discuss its advantages and disadvantages. Although it is a more sensitive indicator of past or present syphilitic infection than many other widely evaluated techniques, several aspects of the test are still not fully understood; in particular its specificity is not yet established and more information is needed on its reactivity in a variety of clinical diseases and in treponemal diseases other than syphilis. It is a relatively expensive technique in terms of technicians' time, reagents and equipment but there are grounds for hope that research now under way into automation of the procedure may improve the situation.