2 Records out of 22207 Records

Analysis of serovar-specific immunity to Neisseria gonorrhoeae.

Author: Fudyk, Trevor Charles

Awarding University: University of Manitoba, Canada

Level : PhD

Year: 2002

Holding Libraries: University Microfilms International ;

Subject Terms: Immunology ; Neisseria gonorrhoeae ; Neisseria infections ; Gonorrhea ; Pumwani, Nairobi, Kenya ;

Abstract:

Infection with Neisseria gonorrhoeae constitutes an important cause of morbidity in human populations. The Porin protein (Por) is the major outer membrane protein of the gonococcus and displays considerable antigenic diversity among gonococcal strains. Two hypotheses to explain the diversity and dynamics of gonococcal populations is that protective, serovar- specific immunity, mediated by antibody to Por, develops following gonococcal infection, and that the development of protective immune responses within the core group act as a selective force for por antigenic heterogeneity in the gonococcal population. One core group in which gonococcal epidemiology has been studied extensively includes a collection of women working the commercial sex trade in the lower socioeconomic district of Pumwani in Nairobi, Kenya. Two experimental strategies were used to evaluate these hypotheses in a more recent longitudinal study of these female, sex workers in Nairobi, Kenya. The first line of experiments sought to examine the nature and distribution of genetic polymorphism in the Por genes of the gonococcal serovars infecting the Nairobi cohort. Nucleotide substitutions were observed predominantly in surface-exposed encoding segments of the 1a and 1b por genes. The majority of substitutions, particularly those occurring in surface- exposed encoding gene segments, resulted in amino acid change. The second line of experiments sought to determine the effect of the antibody response to por on serovar-specific gonococcal infection. Cohort women were assayed for baseline antibody responses to a recombinant 1b2 porin and a collection of polypeptides corresponding to 1b Por surface-exposed loops and followed longitudinally for gonococcal infection. Overall, antibody to the 1b2 porin appeared to provide limited protection from 1b infection, although this protective effect did not appear to extend to infection with 1a serovars. Women with antibody to 1b2 Por experienced significantly fewer homologous 1b2 and heterologous 1b3 serovar infections, compared to women without antibody. The data observed in this study support the hypothesis that the humoral immune response to Por is an important component in the ecologic interaction of human and gonococcal populations, while the generation of antigenically diverse pathogen populations act a mechanism to ensure endemic infection and pathogen survival in the face of this immune barrier. (Abstract shortened by UMI.)

Molecular epidemiology of Neisseria gonorrhoeae using newer methods.

Author: Xia, Minsheng

Awarding University: University of Washington, USA

Level : PhD

Year: 1997

Holding Libraries: University Microfilms International ;

Subject Terms: Microbiology/Neisseria infections/Gonorrhea/Neisseria gonorrhoeae/Neisseria meningitidis/Kingella denitrificans/Eikenella corrodens/Diagnostic tests/ ;

Abstract:

Gonorrhea is one of the most common human sexually transmitted diseases in the United States and the world. Discriminating and reproducible genotyping methods are needed for typing Neisseria gonorrhoeae for epidemiologic studies. In my dissertation, Pulsed-Field Gel Electrophoresis (PFGE) and Polymerase Chain Reaction (PCR) were used for typing N.Gonorrhoeae. PFGE patterns were stable with both in vitro and in vivo passaged N.Gonorrhoeae. Criteria for interpreting PFGE patterns were established based on examination of isolates from sex partners using three different enzymes. Fourteen pro/ia-6 isolates from Kenya produced 8 nhei and 7 xbai patterns. Using a combination of nhei, spei and xbai patterns, both genetic diversity and genetic relatedness were found among 16 isolates with decreased susceptibility to ciprofloxacin recovered over a two-year time period from various geographic locations. Genomic homogeneity of 68 arginine, hypoxanthine and uracil requiring ia-1,2 isolates from Seattle-King County over the past decade were examined by PFGE using nhei and xbai. Based on the criteria that isolates with $/le$1 band difference belonged to a single group, 5 nhei, 8 xbai and 11 nhei-xbai combination PFGE patterns were found. One nhei, one xbai and one nhei-xbai combination pattern accounted for 74%, 57% and 54% of the isolates respectively. A PCR assay was developed to amplify the downstream region of the incomplete tet m transposon in the 25.2 mda conjugative plasmid in 44 N.Gonorrhoeae, 12 N. Meningitidis, 4 Kingella denitrificans and 1 Eikenella corrodens isolates. One of two different PCR products of approximately 700 or 1600 base pairs was amplified. The difference between the two PCR fragments was a deletion of over 800 base pair in the smaller fragment. The two different sized pcr fragments had $>$90% DNA sequence identity with ureaplasma urealyticum tet m downstream sequences. The PCR assay was useful in differentiating the 25.2 mda plasmid. My dissertation demonstrated that PFGE had better discriminatory power than currently used typing methods for N.Gonorrhoeae. The PFGE method could be used to generate data for longitudinal molecular epidemiologic studies of gonococcal infections. Projects completed in my dissertation have laid the foundation for standardized PFGE.