Three-dimensional structure of fimbriae determines specificity of immune response

Abstract

We recently described how a fraction of isolated fimbriae from a multifimbriated strain of Escherichia coli 07:K1:H6 (WF96) could be subdivided by sequential disaggregation in disrupting agents into individual subunits with different molecular weights. In this study, antibodies were raised in rabbits against these isolated fimbrial subunits and against purified intact WF96 fimbriae. These sera were tested by Western blot analysis or by enzyme-linked immunosorbent assays for reactivity against the following antigens: intact WF96 fimbriae, dissociated WF96 fimbriae, dissociated and reaggregated WF96 fimbriae, the WF96 21K fimbrial subunit, reaggregated WF96 21K subunits, the WF96 16K subunits, reaggregated WF96 16K subunits, intact fimbriae from four other E. coli strains, and deaggregated fimbriae from these strains. We found that antibody against intact WF96 fimbriae only reacted strongly with intact WF96 fimbriae, depolymerized and reaggregated WF96 fimbriae, or reaggregated fimbrial subunits; no reactions were evident with intact fimbriae from four other E. coli strains. Conversely, antisera prepared against the WF96 16K subunit and against the WF96 21K subunit did not react with intact WF96 fimbriae or with depolymerized and reaggregated WF96 fimbriae, but did react with homologous isolated subunits. One cross-reaction between fimbrial subunits was apparent: anti-WF96 16K subunit bound to a 21K subunit of deaggregated fimbriae, from another E. coli strain. Taken together, the findings indicate that the three-dimensional structure of the fimbrial preparation used to immunize animals determines the specificity of the immune response.

Analysis of Escherichia coli colonization factor antigen I linear B-cell epitopes, as determined by primate responses, following protein sequence verification

“…This same phenomenon has also been shown with AF/Rl pili (5). These results are in contrast to those of Karch et al (20), who found by using IEM that antisubunit antibodies did not adhere to intact E. coli WF96 pili. With CFA/I and AF/Rl, the population of antibodies binding to the intact pili may not necessarily be the same population of antibodies binding to the linear epitopes, but it has been demonstrated that peptide-specific antibodies can bind to native pili, such as E. coli P pili (39), or to native multisubunit toxins, as has been demonstrated with the S3 subunit of pertussis toxin (38).…”

Conserved and nonconserved epitopes among Haemophilus influenzae type b pili

“…The antibodies generated by native pili reacted with many more strains on immunodot assays than on Western blot assay, suggesting that they recognized primarily structural epitopes that are lost on denaturation of the pili. These results are similar to those of recent work in which other bacterial pili show the dependence of pilus epitopes on the tertiary or quaternary structure of the pili (1,2,8,18,23,27,28). Conversely, antibodies against pilins and the 13-amino-acid pilin peptide did not recognize native pili from any of the strains, including the homologous strain, suggesting that, although these epitopes are conserved on native pili, they may exist in a different conformation or be otherwise inaccessible for antibody binding.…”

Engineering upstream transcriptional and translational signals of Bordetella pertussis serotype 2 fimbrial subunit protein for efficient expression in Escherichia coli: in vitro autoassembly of the expressed product into filamentous structures

“…It has been previously shown by Western blotting under partially denaturing conditions that the serotype 2 fimbrial subunit protein is immunologically distinct from whole fimbriae (Li et al, 1988). This is in agreement with results obtained for several E. coli fimbrial types (Karch et al, 1985). Such E. coli fimbrial subunits that had been dissociated with guanidine HCI were found to reassociate into native fimbriae under appropriate conditions (Eshdat etai, 1981;Karch etal., 1985).…”