SARS-CoV2 pneumonia recovery is linked to expansion of innate lymphoid cells type 2 expressing CCR10

Accelerate lung repair in SARS‐CoV‐2 pneumonia is essential for pandemic handling. Innate lymphoid cells (ILCs) are likely players, given their role in mucosal protection and tissue homeostasis. We studied ILC subpopulations at two time points in a cohort of patients admitted in the hospital due to SARS‐CoV‐2 infection. COVID‐19 patients with moderate/severe respiratory failure featured profound depletion of circulating ILCs at hospital admission, in agreement with overall lymphocyte depletion. However, ILCs recovered in direct correlation with lung function improvement as measured by oxygenation index and in negative association with inflammatory and lung/endothelial damage markers like RAGE. While both ILC1 and ILC2 expanded, ILC2 showed the most striking phenotype changes, with CCR10 upregulation in strong correlation with these parameters. Overall, CCR10⁺ ILC2 emerge as relevant contributors to SARS‐CoV‐2 pneumonia recovery.

Severe COVID-19 Recovery Is Associated with Timely Acquisition of a Myeloid Cell Immune-Regulatory Phenotype

After more than one year since the COVID-19 outbreak, patients with severe disease still constitute the bottleneck of the pandemic management. Aberrant inflammatory responses, ranging from cytokine storm to immune-suppression, were described in COVID-19 and no treatment was demonstrated to change the prognosis significantly. Therefore, there is an urgent need for understanding the underlying pathogenic mechanisms to guide therapeutic interventions. This study was designed to assess myeloid cell activation and phenotype leading to recovery in patients surviving severe COVID-19. We evaluated longitudinally patients with COVID-19 related respiratory insufficiency, stratified according to the need of intensive care unit admission (ICU, n = 11, and No-ICU, n = 9), and age and sex matched healthy controls (HCs, n = 11), by flow cytometry and a wide array of serum inflammatory/immune-regulatory mediators. All patients featured systemic immune-regulatory myeloid cell phenotype as assessed by both unsupervised and supervised analysis of circulating monocyte and dendritic cell subsets. Specifically, we observed a reduction of CD14lowCD16+ monocytes, and reduced expression of CD80, CD86, and Slan. Moreover, mDCs, pDCs, and basophils were significantly reduced, in comparison to healthy subjects. Contemporaneously, both monocytes and DCs showed increased expression of CD163, CD204, CD206, and PD-L1 immune-regulatory markers. The expansion of M2-like monocytes was significantly higher at admission in patients featuring detectable SARS-CoV-2 plasma viral load and it was positively correlated with the levels of specific antibodies. In No-ICU patients, we observed a peak of the alterations at admission and a progressive regression to a phenotype similar to HCs at discharge. Interestingly, in ICU patients, the expression of immuno-suppressive markers progressively increased until discharge. Notably, an increase of M2-like HLA-DRhighPD-L1+ cells in CD14++CD16− monocytes and in dendritic cell subsets was observed at ICU discharge. Furthermore, IFN-γ and IL-12p40 showed a decline over time in ICU patients, while high values of IL1RA and IL-10 were maintained. In conclusion, these results support that timely acquisition of a myeloid cell immune-regulatory phenotype might contribute to recovery in severe systemic SARS-CoV-2 infection and suggest that therapeutic agents favoring an innate immune system regulatory shift may represent the best strategy to be implemented at this stage.

SARS-CoV-2 plasma viral load polarizes the systemic myeloid cell compartment towards an immunosuppressive/regulatory phenotype in severe COVID-19 patients

Severe COVID-19 determines high death rates and health resources overwhelming. Aim of the present study was to shed light on the immune-pathogenesis of severe COVID-19, evaluating the effects of detectable plasma viral load on circulating myeloid cell phenotype and activation. Adult COVID-19 patients with pneumonia stratified according to the degree of respiratory insufficiency were longitudinally followed. Flow cytometry data of monocytes (Mo) and dendritic cells (DCs) subsets were analysed by supervised and unsupervised approaches, in parallel with SARS-CoV-2 plasma viral load by digital droplet PCR and serum cytokines and chemokines. All patients featured systemic immune-suppressive myeloid cell responses, characterized by a reduction of CD14lowCD16+ Mo and reduced expression of CD80, CD86, and SLAN. All DC subset were significantly reduced and both Mo and DC showed increased expression of CD163, CD204, CD206 and PD-L1 immune-regulatory markers. These changes correlated with an unbalanced cytokine/chemokine response, in which G-CSF, M-CSF, IL-6 increased similarly in all patient groups, while low levels of IFN-alpha, beta, IL-1a and IL-1b persisted, associated with increased concentrations of immune-regulatory cytokines as IL-1RA and IL-10. A significantly greater expansion of a PD-L1 positive M2-like population was seen in classical monocytes from viremic patients. Our data favour the conclusion that massive replication of SARS-CoV-2, leading to release in blood, polarize the systemic myeloid cell compartment response towards a more differentiated immunosuppressive/regulatory phenotype.

The identification of the Rosa S-locus and implications on the evolution of the Rosaceae gametophytic self-incompatibility systems

In Rosaceae species, two gametophytic self-incompatibility (GSI) mechanisms are described, the Prunus self-recognition system and the Maleae (Malus/Pyrus/Sorbus) non-self- recognition system. In both systems the pistil component is a S-RNase gene, but from two distinct phylogenetic lineages. The pollen component, always a F-box gene(s), in the case of Prunus is a single gene, and in Maleae there are multiple genes. Previously, the Rosa S-locus was mapped on chromosome 3, and three putative S-RNase genes were identified in the R. chinensis ‘Old Blush’ genome. Here, we show that these genes do not belong to the S-locus region. Using R. chinensis and R. multiflora genomes and a phylogenetic approach, we identified the S-RNase gene, that belongs to the Prunus S-lineage. Expression patterns support this gene as being the S-pistil. This gene is here also identified in R. moschata, R. arvensis, and R. minutifolia low coverage genomes, allowing the identification of positively selected amino acid sites, and thus, further supporting this gene as the S-RNase. Furthermore, genotype–phenotype association experiments also support this gene as the S-RNase. For the S-pollen GSI component we find evidence for multiple F-box genes, that show the expected expression pattern, and evidence for diversifying selection at the F-box genes within an S-haplotype. Thus, Rosa has a non-self-recognition system, like in Maleae species, despite the S-pistil gene belonging to the Prunus S-RNase lineage. These findings are discussed in the context of the Rosaceae GSI evolution. Knowledge on the Rosa S-locus has practical implications since genes controlling floral and other ornamental traits are in linkage disequilibrium with the S-locus.