Hasan, M. Z. | bioRxiv Science

bioRxiv2024

SARS-CoV-2 modulates NK cell responses via induction of HLA-E and triggers expansion of adaptive NK cells during acute infection

HLA-E expression plays a central role for modulation of NK cell function by interaction with inhibitory NKG2A and stimulatory NKG2C receptors on canonical and adaptive NK cells, respectively. Here, we demonstrate that infection of human primary lung tissue with SARS-CoV-2 leads to increased HLA-E expression and show that processing of the peptide YLQPRTFLL from the spike protein is primarily responsible for the strong, dose-dependent increase of HLA-E. Targeting the peptide site within the spike protein revealed that a single point mutation was sufficient to abrogate the increase in HLA-E expression. Spike-mediated induction of HLA-E differentially affected NK cell function: whereas degranulation, IFN-{gamma} production, and target cell cytotoxicity were enhanced in NKG2C+ adaptive NK cells, effector functions were inhibited in NKG2A+ canonical NK cells. Analysis of a cohort of COVID-19 patients in the acute phase of infection revealed that adaptive NK cells were induced irrespective of the HCMV status, challenging the paradigm that adaptive NK cells are only generated during HCMV infection. During the first week of hospitalization, patients exhibited a selective increase of early NKG2C+CD57- adaptive NK cells whereas mature NKG2C+CD57+ cells remained unchanged. Further analysis of recovered patients suggested that the adaptive NK cell response is primarily driven by a wave of early adaptive NK cells during acute infection that wanes once the infection is cleared. Together, this study suggests that NK cell responses to SARS-CoV-2 infection are majorly influenced by the balance between canonical and adaptive NK cells via the HLA-E/NKG2A/C axis.

immunology↗

bioRxiv2021

Mfsd2b and Spns2 are essential for maintenance of blood vessels during development and protection of anaphylaxis

Sphingosine-1-phosphate (S1P) is a potent lipid mediator that is secreted by several cell types to induce signaling. We recently showed that Mfsd2b is an S1P transporter from hematopoietic cells, which contributes approximately 50% plasma S1P. To further determine the sources of plasma S1P, here, we report the characterizations of compound deletions of Mfsd2b and Spns2, another S1P transporter from endothelial cells. Global deletion of Mfsd2b and Spns2 (gDKO) resulted in embryonic lethality between E13.5 and E14.5 with severe hemorrhage that largely recapitulated the phenotypes from global S1P1 knockout mice, indicating that together with Mfsd2b, Spns2 also provides embryonic source of S1P for S1P1 stimulation. The hemorrhagic phenotypes in gDKO embryos were accompanied by increased angiogenesis and defects of tight junction proteins, indicating that S1P from Mfsd2b and Spns2 is essential for blood vessel integrity and maturation. The various sources of S1P in postnatal stages are yet to be fully understood. Postnatal ablation of S1P synthesis enzymes using Mx1Cre shows that Mx1Cre-sensitive cells provide most of plasma S1P. Interestingly, we showed that compound postnatal deletion of Mfsd2b and Spns2 using Mx1Cre (ctDKO-Mx1Cre) resulted in maximal reduction of 80% plasma S1P. Thus, a small amount of plasma S1P is supplied from other sources independent of Mfsd2b and Spns2. Nevertheless, the vasculature in the lung of ctDKO-Mx1Cre mice was compromised. Furthermore, ctDKO-Mx1Cre mice also exhibited severe susceptibility to anaphylaxis, indicating that S1P from Mfsd2b and Spns2 is indispensable during vascular stress. Together, our results show that Mfsd2b and Spns2 provide a critical source of S1P for embryonic development and they also provide a majority of plasma S1P for vascular homeostasis.

molecular biology↗