Spontaneous point mutations in the capsule synthesis locus leading to structural and functional changes of the capsule in serogroup A meningococcal populations

Abstract

Whole genome sequencing analysis of 100 Neisseria meningitidis serogroup A isolates has revealed that the csaABCD-ctrABCD-ctrEF capsule polysaccharide synthesis locus represents a spontaneous point mutation hotspot. Structural and functional properties of the capsule of 11 carriage and two disease isolates with non-synonymous point mutations or stop codons in capsule synthesis genes were analyzed for their capsular polysaccharide expression, recognition by antibodies and sensitivity to bactericidal killing. Eight of eleven carriage isolates presenting capsule locus mutations expressed no or reduced amounts of capsule. One isolate with a stop codon in the O-acetyltransferase gene expressed non-O-acetylated polysaccharide, and was not recognized by anti-capsule antibodies. Capsule and O-acetylation deficient mutants were resistant to complement deposition and killing mediated by anti-capsular antibodies, but not by anti-lipopolysaccharide antibodies. Two capsule polymerase mutants, one carriage and one case isolate, showed capsule over-expression and increased resistance against bactericidal activity of both capsule- and lipopolysaccharide-specific antibodies. Meningococci have developed multiple strategies for changing capsule expression and structure, which is relevant both for colonization and virulence. Here we show that point mutations in the capsule synthesis genes substantially contribute to the repertoire of genetic mechanisms in natural populations leading to variability in capsule expression.

GMMA Is a Versatile Platform to Design Effective Multivalent Combination Vaccines

“…To quantify the amount of linked protein antigen, amino acid quantification was used. Amount of saccharide antigen linked was determined by HPAEC-PAD after performing acid hydrolysis directly on GMMA, as previously described [ 22 , 23 , 24 , 25 , 26 , 27 ]. It was verified that there was no interference from GMMA in the quantification of each saccharide.…”

“…Absence of free proteins was estimated by analysis of the purified conjugates by HPLC-SEC by using a TSK gel 4000–6000 PW columns (Tosoh Bioscience LCC, King of Prussia, PA, USA) in series and eluting with PBS for 60 min at a flow rate of 0.5 mL/min [ 19 ]. Percentage of free saccharide was calculated by solid phase extraction (SPE) using a C4 cartridge (BGB Analytik, Böckten, Switzerland) followed by HPAEC-PAD analysis [ 25 , 26 ].…”

Generalized Modules for Membrane Antigens as Carrier for Polysaccharides: Impact of Sugar Length, Density, and Attachment Site on the Immune Response Elicited in Animal Models

“…Conjugates were characterized by micro BCA for total protein recovery (21), while amount of saccharide antigen linked was determined by HPAEC-PAD after performing acid hydrolysis directly on GMMA as previously described (24,(32)(33)(34)(35)(36). It was verified that there was no interference from GMMA in the quantification of each saccharide.…”

Metabolic modulation of redox state confounds fish survival against Vibrio alginolyticus infection

“…However, the development of effective vaccines is time and labour consuming. More importantly, the immunogens of microorganisms are always subject to mutations, making vaccine less effective (Ispasanie et al , 2018; Li et al , 2018). Thus, it is necessary to develop novel antibiotic‐free approach for managing V. alginolyticus infection.…”