Affiliation:
1. Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
Abstract
ABSTRACT
Neisseria meningitidis
and
Neisseria gonorrhoeae
modify the terminal lacto-
N
-neotetraose moiety of their lipooligosaccharide (LOS) with sialic acid. N. gonorrhoeae LOS sialylation blocks killing by complement, which is mediated at least in part by enhanced binding of the complement inhibitor factor H (FH). The role of LOS sialylation in resistance of N. meningitidis to serum killing is less well defined. Sialylation in each species is catalyzed by the enzyme LOS α-2,3-sialyltransferase (Lst). Previous studies have shown increased Lst activity in N. gonorrhoeae compared to N. meningitidis due to an ~5-fold increase in
lst
transcription. Using isogenic N. gonorrhoeae strains engineered to express gonococcal
lst
from either the N. gonorrhoeae or N. meningitidis
lst
promoter, we show that decreased expression of
lst
(driven by the N. meningitidis promoter) reduced LOS sialylation as determined by less incorporation of tritium-labeled cytidine monophospho-
N
-acetylneuraminic acid (CMP-NANA; the donor molecule for sialic acid). Diminished LOS sialylation resulted in reduced rates of FH binding and increased pathway activation compared to N. gonorrhoeae promoter-driven
lst
expression. The N. meningitidis
lst
promoter generated sufficient Lst to sialylate N. gonorrhoeae LOS
in vivo
, and the level of sialylation after 24 h in the mouse genital tract was sufficient to mediate resistance to human serum
ex vivo
. Despite demonstrable LOS sialylation
in vivo
, gonococci harboring the N. meningitidis
lst
promoter were outcompeted by those with the N. gonorrhoeae
lst
promoter during coinfection of the vaginal tract of estradiol-treated mice. These data highlight the importance of high
lst
expression levels for gonococcal pathogenesis.
IMPORTANCE
Neisseria gonorrhoeae
has become resistant to nearly every therapeutic antibiotic used and is listed as an “urgent threat” by the Centers for Disease Control and Prevention. Novel therapies are needed to combat drug-resistant N. gonorrhoeae. Gonococci express an α-2,3-sialyltransferase (Lst) that can scavenge sialic acid from the host and use it to modify lipooligosaccharide (LOS). Sialylation of gonococcal LOS converts serum-sensitive strains to serum resistance, decreases antibody binding, and combats killing by neutrophils and antimicrobial peptides. Mutant N. gonorrhoeae that lack Lst (cannot sialylate LOS) are attenuated in a mouse model. Lst expression levels differ among N. gonorrhoeae strains, and N. gonorrhoeae typically expresses more Lst than
Neisseria meningitidis
. Here we examined the significance of differential
lst
expression levels and determined that the level of LOS sialylation is critical to the ability of N. gonorrhoeae to combat the immune system and survive in an animal model. LOS sialylation may be an ideal target for novel therapies.
Publisher
American Society for Microbiology
Cited by
33 articles.
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