Lange, J. L. | Search bioRxiv

bioRxiv2022

MAIT cells activate dendritic cells to promote T follicular helper cell differentiation and humoral immunity

Protective immune responses against respiratory pathogens, including influenza virus are initiated by the mucosal immune system. However, most licensed vaccines are administered parenterally and are largely ineffective at inducing mucosal immunity. The development of safe and effective mucosal vaccines has largely been hampered by the lack of a suitable mucosal adjuvant. In this study we explore a novel class of adjuvant that harness mucosal-associated invariant T (MAIT) cells. We show evidence that intranasal immunisation of MAIT cell agonists co-administered with protein, including haemagglutinin from influenza A virus induced potent humoral immunity and immunoglobulin (Ig)A production, which protected mice against infection. MAIT cell adjuvant activity was mediated by CD40L-dependent activation of dendritic cells and subsequent priming of CD4+ T follicular helper cells. In summary, we show that MAIT cells are promising vaccine targets that can be utilised as cellular adjuvants in mucosal vaccines.

immunology↗

bioRxiv2021

The polyglutamine amyloid nucleus in living cells is monomeric and has competing dimensions of order

A long-standing goal of the study of amyloids has been to characterize the structural basis of the rate-determining nucleating event. However, the ephemeral nature of that event has made it inaccessible to classical biochemistry, structural biology, and computational approaches. Here, we addressed that limitation by measuring the dependence of amyloid formation on concentration and conformational templates in living cells, whose volumes are sufficiently small to resolve the outcomes of independent nucleation events. We characterized numerous rationally designed sequence variants of polyglutamine (polyQ), a polypeptide that precipitates Huntingtons and other amyloid-associated neurodegenerative diseases when its length exceeds a characteristic threshold. This effort uncovered a pattern of approximately twelve Qs, only for polypeptides exceeding the clinical length threshold, that allow for amyloid nucleation to occur spontaneously within single polypeptides. Nucleation was inhibited by intermolecular phase separation. Using atomistic molecular dynamics simulations, we found that the pattern encodes a minimal steric zipper of interdigitated side chains. Lateral growth of the steric zipper competed with axial growth to produce "pre-amyloid" oligomers. By illuminating the structural mechanism of polyQ amyloid formation in cells, our findings reveal a potential molecular etiology for polyQ diseases, and may provide a roadmap for the design of new therapies.

biophysics↗