Bacterial exo-α-sialidases subvert the complement system through desialylation.
Kurni Kurniyati1, Nicholas D Clark2, Qin Fu3
1Philips Institute for Oral Health Research, Virginia Commonwealth University, Richmond, VA, USA.
Biorxiv : the Preprint Server for Biology
|February 12, 2026
Summary
Bacterial sialidases disable complement immunity by removing sialic acids from immune proteins. This desialylation prevents complement activation, allowing pathogens to evade immune responses.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- The complement system is crucial for innate immunity.
- Bacterial sialidases modify host sialoglycans, but their effect on complement is unclear.
Purpose of the Study:
- Investigate how bacterial sialidases impact complement immunity.
- Elucidate the mechanism of complement evasion by bacterial sialidases.
Main Methods:
- Utilized genetics, biochemistry, glycobiology, mass spectrometry, and structural biology.
- Analyzed six sialidases from five human pathogens.
- Examined interactions with complement components and regulators.
Main Results:
- Demonstrated that complement components (IgG, C1q, C4, C5) and regulators (Factor I, Factor H, C4bp) are sialylated.
- Showed bacterial sialidase-mediated desialylation suppresses complement activation and deposition.
- Identified a conserved catalytic domain across diverse sialidases.
Conclusions:
- Bacterial sialidases enable complement evasion through desialylation.
- Diverse bacterial pathogens employ a conserved mechanism to disable complement immunity.
Related Concept Videos
01:27Complement System
10.9K
The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a...
10.9K
00:49Complementation Tests
6.3K
A complementation test is a simple cross to identify whether the two mutations are located on the same gene or different genes. It was first performed by Edward Lewis in the 1940s while working on fruit flies. He developed the test to identify the location and arrangement of different mutations on chromosomes.
Organisms heterozygous for different mutations are crossed pairwise in all combinations. If present on different genes, the mutations can complement each other by providing the missing...
Organisms heterozygous for different mutations are crossed pairwise in all combinations. If present on different genes, the mutations can complement each other by providing the missing...
6.3K
01:33Bacterial Transformation
60.2K
In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
60.2K
01:30Bacterial Signaling
41.3K
Bacterial signaling can occur within bacteria (intracellular) or between bacteria (intercellular). At times, a group of bacteria behaves like a community. To achieve this, they engage in quorum sensing, the perception of higher cell density that causes changes in gene expression. Quorum sensing involves both extracellular and intracellular signaling. The signaling cascade starts with a molecule called an autoinducer (AI). Individual bacteria produce AIs that move out of the bacterial cell...
41.3K
01:10α-Alkylation of Ketones via Enolate Ions
3.9K
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
3.9K
01:10Factors Affecting α-Alkylation of Ketones: Choice of Base
3.6K
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed by nucleophilic substitution. The choice of base employed is essential as it is the key factor in determining the reaction outcome.
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...
The reaction involving bases like EtO− whose conjugate acid EtOH (pKa = 15.9) is stronger than the ketone (pKa = 19.2) results in an equilibrium mixture with higher ketone concentration. As a consequence,...
3.6K