Antigenic variation of gonococcal pilin expression in vivo: analysis of the strain FA1090 pilin repertoire and identification of the pilS gene copies recombining with pilE during experimental human infection The GenBank accession numbers for the sequences reported in this paper are U58840–U58851, U61269, L28978, L28980, L28987 and L28990–L28992.

Abstract

Antigenic variation of gonococcal pilin involves a family of variable genes that undergo homologous recombination, resulting in transfer of variant sequences from the pilS silent gene copies into the complete pilE expression locus. Little is known about the specific recombination events that are involved in assembling new variant pilin genes in vivo. One approach to understanding pilin variation in vivo is to carry out experimental human infections with a gonococcal strain having a fully characterized repertoire of pilin genes, so that the specific recombination events occurring in vivo can be determined. To this end, the authors cloned, sequenced and mapped the pilin genes of strain FA1090 of Neisseria gonorrhoeae. This strain contains one pilE locus and 19 silent gene copies that are arranged in five pilS loci ; the pilE locus and four of the pilS loci are clustered in a 35 kb region of the chromosome. The general features of the pilin loci in FA1090 are similar to those in strain MS11, in which the mechanism of pilin variation has been extensively studied. However, none of the silent copy sequences are identical in the two strains, which emphasizes the extreme variability in this gene family among gonococci. Three male volunteers were inoculated with the same variant of strain FA1090 and developed urethritis within 2-4 d. The pilE gene sequences from a total of 23 colonies cultured from the subjects were analysed, determining which pilS silent copy donated each portion of the expressed pilE genes. There were 12 different pilin variants, one of which was the original inoculum variant, among the in vivo-expressed pilE gene sequences. The pilE of the inoculum variant was derived entirely from a single silent copy (pilS6c1). However, the pilE genes in the majority of the colonies cultured from the infected subjects were chimeras of sequence derived from two or three silent copies. Recombination to generate new pilE sequences involved exchange of single variable minicassettes, multiple minicassettes, entire silent gene copies, or (rarely) recombination within a minicassette.

Type IV Pilin Proteins: Versatile Molecular Modules

“…The number of pilS alleles varies between strains, as 17 silent copies were identified in N. gonorrhoeae strain MS11, while 19 different pilS loci at 6 distinct chromosomal locations were identified in N. gonorrhoeae strain FA1090 (161,165). Each pilS allele lacks a promoter, a ribosome binding site, and an approximately 150-bp region from the 5= end of pilE (116,161).…”

Reconstructing immune phylogeny: new perspectives

“…In various pathogens, including bacteria and protozoan parasites, several fundamental mechanisms of DNA change are used during invasion of the host. DNA recombination [148][149][150][151] , gene conversion [152][153][154] and gene hypermutation can lead to the evasion of host detection and to the subsequent clonal selection of the pathogenic variant. For example, in trypanosomes, DNA recombination and gene conversion rapidly modify variant surface glycoproteins and allow evasion of host detection 155,156 .…”

Neisseria gonorrhoeae MutS Affects Pilin Antigenic Variation through Mismatch Correction and Not by pilE Guanine Quartet Binding

“…1A and B). There are four to six pilS loci in each gonococcal isolate, with 19 silent copies located in six separate loci in strain FA1090 (16). These silent pilS copies share significant sequence similarity to the expressed pilE gene and act as reservoirs of variant genetic information.…”