Targeting TLR4 during vaccination boosts MAdCAM-1+ lymphoid stromal cell activation and promotes the aged germinal center response

The failure to generate enduring humoral immunity after vaccination is a hallmark of advancing age. This can be attributed to a reduction in the germinal center (GC) response, which generates long-lived antibody-secreting cells that protect against (re)infection. Despite intensive investigation, the primary cellular defect underlying impaired GCs in aging has not been identified. Here, we used heterochronic parabiosis to demonstrate that GC formation was dictated by the age of the lymph node (LN) microenvironment rather than the age of the immune cells. Lymphoid stromal cells are a key determinant of the LN microenvironment and are also an essential component underpinning GC structure and function. Using mouse models, we demonstrated that mucosal adressin cell adhesion molecule-1 (MAdCAM-1)-expressing lymphoid stromal cells were among the first cells to respond to NP-KLH + Alum immunization, proliferating and up-regulating cell surface proteins such as podoplanin and cell adhesion molecules. This response was essentially abrogated in aged mice. By targeting TLR4 using adjuvants, we improved the MAdCAM-1+ stromal cell response to immunization. This correlated with improved GC responses in both younger adult and aged mice, suggesting a link between stromal cell responses to immunization and GC initiation. Using bone marrow chimeras, we also found that MAdCAM-1+ stromal cells could respond directly to TLR4 ligands. Thus, the age-associated defect in GC and stromal cell responses to immunization can be targeted to improve vaccines in older people

Ageing promotes early T follicular helper cell differentiation by modulating expression of RBPJ.

Ageing profoundly changes our immune system and is thought to be a driving factor in the morbidity and mortality associated with infectious disease in older people. We have previously shown that the impaired immunity to vaccination that occurs in aged individuals is partly attributed to the effect of age on T follicular helper (Tfh) cell formation. In this study, we examined how age intrinsically affects Tfh cell formation in both mice and humans. We show increased formation of Tfh precursors (pre-Tfh) but no associated increase in germinal centre (GC)-Tfh cells in aged mice, suggesting age-driven promotion of only early Tfh cell differentiation. Mechanistically, we show that ageing alters TCR signalling which drives expression of the Notch-associated transcription factor, RBPJ. Genetic or chemical modulation of RBPJ or Notch rescues this age-associated early Tfh cell differentiation, and increased intrinsic Notch activity recapitulates this phenomenon in younger mice. Our data offer mechanistic insight into the age-induced changes in T-cell activation that affects the differentiation and ultimately the function of effector T cells

Spatial dysregulation of T follicular helper cells impairs vaccine responses in aging.

The magnitude and quality of the germinal center (GC) response decline with age, resulting in poor vaccine-induced immunity in older individuals. A functional GC requires the co-ordination of multiple cell types across time and space, in particular across its two functionally distinct compartments: the light and dark zones. In aged mice, there is CXCR4-mediated mislocalization of T follicular helper (TFH) cells to the dark zone and a compressed network of follicular dendritic cells (FDCs) in the light zone. Here we show that TFH cell localization is critical for the quality of the antibody response and for the expansion of the FDC network upon immunization. The smaller GC and compressed FDC network in aged mice were corrected by provision of TFH cells that colocalize with FDCs using CXCR5. This demonstrates that the age-dependent defects in the GC response are reversible and shows that TFH cells support stromal cell responses to vaccines

Follicular regulatory T cells can access the germinal center independently of CXCR5

The germinal center (GC) response is critical for generating high-affinity humoral immunity and immunological memory, which forms the basis of successful immunization. Control of the GC response is thought to require follicular regulatory T (Tfr) cells, a subset of suppressive Foxp3+ regulatory T cells located within GCs. Relatively little is known about the exact role of Tfr cells within the GC and how they exert their suppressive function. A unique feature of Tfr cells is their reported CXCR5-dependent localization to the GC. Here, we show that the lack of CXCR5 on Foxp3+ regulatory T cells results in a reduced frequency, but not an absence, of GC-localized Tfr cells. This reduction in Tfr cells is not sufficient to alter the magnitude or output of the GC response. This demonstrates that additional, CXCR5-independent mechanisms facilitate Treg cell homing to the GC

Spatial dysregulation of T follicular helper cells impairs vaccine responses in aging.

Acknowledgements: We thank C. Vinuesa and A. Liston for critical feedback on this paper. We thank the Babraham Institute Biological Support Unit staff, who performed in vivo treatments of our animals and took care of animal husbandry. We thank the staff of the Babraham Flow Cytometry and Imaging Facilities for their technical support. The National Institute for Health Research Cambridge Biomedical Research Center is a partnership between Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge, funded by the National Institute for Health Research. We thank the National Institute for Health Research Cambridge Biomedical Research Center volunteers for their participation and thank staff for their contribution in coordinating the vaccinations and venipuncture. This study was supported by funding from the Biotechnology and Biological Sciences Research Council (grant nos. BB/W001578/1, BBS/E/B/000C0407, BBS/E/B/000C0427 to M.A.L.; grant no. BBSRC BB/N011740/1 to A.E.D; and the Campus Capability Core Grant to the Babraham Institute), the European Union’s Horizon 2020 research and innovation program ‘ENLIGHT-TEN’ under the Marie Sklodowska-Curie grant agreement no. 675395 to M.A.L., a grant from IdEx Université de Paris (grant no. ANR-18-IDEX-0001 to M.E.) and by an ANR PRC grant (grant no. ANR-17-CE14-0019 to K.B.). M.A.L. is an EMBO Young Investigator and a Lister Institute Prize Fellow. D.B. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Emmy Noether Programs BA 5132/1-1 and BA 5132/1-2 (grant no. 252623821 to D.B.), SFB 1054 Project B12 (grant no. 210592381 to D.B.) and Germany’s Excellence Strategy EXC2151 (grant no. 390873048 to D.B.). P.A.R. was supported by the Human Frontier Science Program (grant no. RGP0033/2015 to P.A.R.) and a PhD fellowship granted by École Normale Supérieure de Lyon. J.L.L. is supported by a National Science Scholarship (PhD) by the Agency for Science, Technology and Research, Singapore. D.L.H. received a National Health and Medical Research Council Australia Early-Career Fellowship (grant no. APP1139911). A.R.B. received a Sir Henry Wellcome Postdoctoral Fellowship (grant no. 222793/Z/21/Z). J.P.L. was a recipient of the People Program (Marie Curie Actions) of the European Union’s Seventh Framework Program (FP7/2007-2013) under REA grant agreement no. PCOFUND-GA-2013-609102.The magnitude and quality of the germinal center (GC) response decline with age, resulting in poor vaccine-induced immunity in older individuals. A functional GC requires the co-ordination of multiple cell types across time and space, in particular across its two functionally distinct compartments: the light and dark zones. In aged mice, there is CXCR4-mediated mislocalization of T follicular helper (TFH) cells to the dark zone and a compressed network of follicular dendritic cells (FDCs) in the light zone. Here we show that TFH cell localization is critical for the quality of the antibody response and for the expansion of the FDC network upon immunization. The smaller GC and compressed FDC network in aged mice were corrected by provision of TFH cells that colocalize with FDCs using CXCR5. This demonstrates that the age-dependent defects in the GC response are reversible and shows that TFH cells support stromal cell responses to vaccines