M. Zeeshan Chaudhry

Microfold (M) cells transcytose luminal antigens to initiate mucosal adaptive immunity, but their role in organizing innate responses in Peyer’s patches is unclear. Here we showed that Peyer’s patch M cells organized an epithelial–group 3 innate lymphoid cell (ILC3) axis, establishing a spatial niche within the dome epithelium that drove ILC3 localization, proliferation and IL-22 production. We found that epithelial, but not hematopoietic, SPI-B was required for intestinal IgA responses to establish this niche. Single-cell profiling of intestinal SPI-B ⁺ epithelial cells revealed that M cells were highly heterogeneous, displaying tissue- and pathogen-specific transcriptional programs. Using subset-specific genetic perturbation and whole-mount imaging, we found that this circuit relied on CCR6-dependent positioning cues and RANK–RANKL signaling to ILC3 to regulate Peyer’s patch ILC3 homeostasis. Together, these findings identified Peyer’s patch M cells as organizers that spatially coordinated innate cell localization, proliferation and cytokine production to maintain mucosal barrier defense.

Natural killer cells defend against malignancies and viral infections through a tightly controlled program of differentiation and maturation. However, the transcriptional mechanisms guiding this process remain incompletely defined. Using paired single-cell multiomic profiling, we identify GFI1 as an epigenetic regulator of NK cell differentiation, coordinating EOMES and T-BET transcriptional balance to promote NK cell proliferation and the transition from immature to terminally differentiated NK cell states. GFI1 represses FOXO1 chromatin accessibility in mature NK cells, which normally limits NK cell proliferation and maturation. Co-deletion of both GFI1 and FOXO1 largely rescues NK cell differentiation, identifying a critical GFI1–FOXO1 axis required for protection against tumour metastasis. These findings position GFI1 as a key transcriptional node integrating NK cell differentiation, activation and effector programs.

Long-lived memory CD8⁺ T cells are essential for the control of persistent viral infections. The mechanisms that preserve memory cells are poorly understood. Fate mapping of the transcriptional repressor GFI1 identified that GFI1 was differentially regulated in virus-specific CD8⁺ T cells and was selectively expressed in stem cell memory and central memory cells. Deletion of GFI1 led to reduced proliferation and progressive loss of memory T cells, which in turn resulted in failure to maintain antigen-specific CD8⁺ T cell populations following infection with chronic lymphocytic choriomeningitis virus or murine cytomegalovirus. Ablation of GFI1 resulted in downregulation of the transcription factors EOMES and BCL-2 in memory CD8⁺ T cells. Ectopic expression of EOMES rescued the expression of BCL-2, but the persistence of memory CD8⁺ T cells was only partially rescued. These findings highlight the critical role of GFI1 in the long-term maintenance of memory CD8⁺ T cells in persistent infections by sustaining their proliferative potential.

Current vaccines against COVID-19 elicit immune responses that are overall strong but wane rapidly. As a consequence, the necessary booster shots have contributed to vaccine fatigue. Hence, vaccines that would provide lasting protection against COVID-19 are needed, but are still unavailable. Cytomegaloviruses (CMVs) elicit lasting and uniquely strong immune responses. Used as vaccine vectors, they may be attractive tools that obviate the need for boosters. Therefore, we tested the murine CMV (MCMV) as a vaccine vector against COVID-19 in relevant preclinical models of immunization and challenge. We have previously developed a recombinant MCMV vaccine vector expressing the spike protein of the ancestral SARS-CoV-2 (MCMV^S). In this study, we show that the MCMV^S elicits a robust and lasting protection in young and aged mice. Notably, spike-specific humoral and cellular immunity was not only maintained but also even increased over a period of at least 6 months. During that time, antibody avidity continuously increased and expanded in breadth, resulting in neutralization of genetically distant variants, like Omicron BA.1. A single dose of MCMV^S conferred rapid virus clearance upon challenge. Moreover, MCMV^S vaccination controlled two variants of concern (VOCs), the Beta (B.1.135) and the Omicron (BA.1) variants. Thus, CMV vectors provide unique advantages over other vaccine technologies, eliciting broadly reactive and long-lasting immune responses against COVID-19.

Tissue-resident innate lymphoid cells (ILCs) play a vital role in the frontline defense of various tissues, including the lung. The development of type 2 ILCs (ILC2s) depends on transcription factors such as GATA3, RORα, GFI1, and Bcl11b; however, the factors regulating lung-resident ILC2s remain unclear. Through fate mapping analysis of the paralog transcription factors GFI1 and GFI1B, we show that GFI1 is consistently expressed during the transition from progenitor to mature ILC2s. In contrast, GFI1B expression is limited to specific subsets of bone marrow progenitors and lung-resident ILC progenitors. We found that GFI1B ⁺ lung ILC progenitors represent a multi-lineage subset with tissue-resident characteristics and the potential to form lung-derived ILC subsets and liver-resident ILC1s. Loss of GFI1B in bone marrow progenitors led to the selective loss of lung-resident IL-18R ⁺ ILCs and mature ILC2, subsequently preventing the emergence of effector ILCs that could protect the lung against inflammatory or tumor challenge.

Cytomegalovirus (CMV) induces a unique T cell response, where antigen-specific populations do not contract, but rather inflate during viral latency. It has been proposed that subclinical episodes of virus reactivation feed the inflation of CMV-specific memory cells by intermittently engaging T cell receptors (TCRs), but evidence of TCR engagement has remained lacking. Nuclear factor of activated T cells (NFAT) is a family of transcription factors, where NFATc1 and NFATc2 signal downstream of TCR in mature T lymphocytes. We show selective impacts of NFATc1 and/or NFATc2 genetic ablations on the long-term inflation of MCMV-specific CD8⁺ T cell responses despite largely maintained responses to acute infection. NFATc1 ablation elicited robust phenotypes in isolation, but the strongest effects were observed when both NFAT genes were missing. CMV control was impaired only when both NFATs were deleted in CD8⁺ T cells used in adoptive immunotherapy of immunodeficient mice. Transcriptome analyses revealed that T cell intrinsic NFAT is not necessary for CD8⁺ T cell priming, but rather for their maturation towards effector-memory and in particular the effector cells, which dominate the pool of inflationary cells.