Biology subjects

Swan, J.

Publications and source records attributed to Swan, J..

3 recordsLinked to original sources

bioRxiv2025

Reduced efficacy of an anti-toxin vaccine from senescence-driven attenuation of toxin virulence

It remains unclear why vaccines targeting prominent microbial virulence factors often fail in clinical trials. Because microbial virulence depends on interaction with the host immune system, we investigated how changes in host immune function alter vaccine efficacy. Using a vaccine against Staphylococcus aureus alpha toxin (Hla), which targets host metalloprotease ADAM10 on myeloid cells, we show that Hla virulence is reduced in aged mice due to diminished ADAM10 activity and impaired myeloid cell function. Depletion of myeloid cells with cyclophosphamide in young mice similarly reduced toxin virulence. Immunization against Hla conferred strong protection against Staphylococcus aureus infection in young but not aged mice. These findings indicate that pathogenic functions of microbial factors characterized in immunocompetent young animals may not predict virulence or vaccine efficacy in immunocompromised hosts. These findings underscore the need to account for host immune status in the development and evaluation of vaccines targeting microbial virulence factors.

microbiology↗

bioRxiv2025

The sialome of the retina, alteration in age-related macular degeneration (AMD) pathology and potential impacts on Complement Factor H

PurposeLittle is known about sialic acids of the human retina, despite their integral role in self/non-self-discrimination by complement factor H (CFH), the alternative complement pathway inhibitor. MethodsA custom sialoglycan microarray was used to characterize the sialic acid-binding specificity of native CFH or recombinant molecules where IgG Fc was fused to CFH domains 16-20 (contains a sialic acid-binding site), domains 6-7 (contains a glycosaminoglycan-binding site) or the CFH-related proteins (CFHRs) 1 and 3. We analyzed macular and peripheral retinal tissue from post-mortem ocular globes for amount, type, and presentation (glycosidic linkage type) of sialic acid in individuals with age-related macular degeneration (AMD) and age-matched controls using fluorescent lectins and antibodies to detect sialic acid and endogenous CFH. Released sialic acids from neural retina, retinal pigmented epithelium (RPE) cells and the Bruchs membrane (BrM) were labelled with 1,2-diamino-4,5-methylenedioxybenzene-2HCl (DMB), separated and quantified by high-performance liquid chromatography (DMB-HPLC). ResultsBoth native CFH and the recombinant CFH domains 16-20 recognized Neu5Ac and Neu5Gc that is 2-3-linked to the underlying galactose. 4-O-Actylation of sialic acid and sulfation of GlcNAc did not inhibit binding. Different linkage types of sialic acid were localized at different layers of the retina. The greatest density of 2-3-sialic acid, which is the preferred ligand of CFH, did not colocalize with endogenous CFH. The level of sialic acids at the BrM/choroid interface of macula and peripheral retina of individuals with AMD were significantly reduced. ConclusionsThe sialome of the human retina is altered in AMD. This can affect CFH binding and consequently, alternative complement pathway regulation.

biochemistry↗

bioRxiv2021

Hidden conformations differentiate day and night in a circadian pacemaker

The AAA+ protein KaiC is the central pacemaker for cyanobacterial circadian rhythms. Composed of two hexameric rings with tightly coupled activities, KaiC undergoes changes in autophosphorylation on its C-terminal (CII) domain that restrict binding of of clock proteins on its N-terminal (CI) domain to the evening. Here, we use cryo-electron microscopy to investigate how daytime and nighttime states of CII regulate KaiB binding to CI. We find that the CII hexamer is destabilized during the day but takes on a rigidified C2-symmetric state at night,concomitant with ring-ring compression. Residues at the CI-CII interface are required for phospho-dependent KaiB association, coupling ATPase activity on CI to cooperative KaiB recruitment. Together these studies reveal how daily changes in KaiC phosphorylation regulate cyanobacterial circadian rhythms. One-Sentence SummaryCryo-EM structures of KaiC in its day and night states reveal the structural basis for assembly of clock regulatory complexes.

biochemistry↗