Archive 21/10/2

A group from The Institute of Medical Science, The University of Tokyo, etc. has reported that Antibody-Dependent Enhancement of SARS-CVoV-2 infection to immune cells is real.
https://journals.asm.org/doi/10.1128/mBio.01987-21

Viruses infect cells mainly via specific receptors at the cell surface. Antibody-dependent enhancement (ADE) of infection is an alternative mechanism of infection for viruses to infect immune cells that is mediated by antibodies and IgG receptors (FcγRs).

Authors generated BHK cells stably expressing human FcγRs (FcγRIA, FcγRIIA, or FcγRIIIA) or human angiotensin-converting enzyme 2 (hACE2) (the entry receptor for SARS-CoV-2). Wild-type BHK cells lack human ACE2 expression and are not susceptible to SARS-CoV-2.

BHK cells were infected with a firefly luciferase-expressing vesicular stomatitis virus (VSV) lacking the VSV-G gene and pseudotyped with SARS-CoV-2 spike (VSV-SARS2-S). Although BHK-hACE2 cells were susceptible to VSV-SARS2-S, the BHK-FcγRIA, BHK-FcγRIIA, and BHK-FcγRIIIA cells were not susceptible due to the lack of hACE2. However, using convalescent-phase plasma from COVID-19 patients and incubated with VSV-SARS2-S, it was found that two types of FcγRs, FcγRIIA and FcγRIIIA, mediate ADE of SARS-CoV-2 infection in the presence of ACE2.

It was also confirmed that SARS-CoV-2 infection is enhanced by convalescent-phase plasma in primary macrophages.

A group from West China Hospital, Sichuan University, Chengdu, China, etc. has reported O-glycosylation of SARS-CoV-2 Spike proteins.
https://www.frontiersin.org/articles/10.3389/fchem.2021.689521/full

Authors have analyzed O-glycosylation of SARS-CoV-2 Spike protein expressed in insect cells and human cells. The numbers of glycosylation sites were different between insect and human ells (23 in insect cells, 30 in human cells), and also most of O-glycans expressed in human cells were sialylated. It is so clear that glycosylation of SARS-CoV-2 Spike changes with host cell types.

A group from Institute of Microbiology, Chinese Academy of Sciences, Beijing, China, has studies bacterial and fungal communities of chili pepper rhizosphere using amplicons (16S and ITS) and investigated how Fusarium wilt disease (FWD) affects its microbiomes.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8444440/

Fusarium wilt disease (FWD) is often caused by the Fusarium oxysporum species complex, a classical soil-borne disease that attacks a wide variety of economically important crops, including banana, watermelon, and Solanaceae plants (e.g., tomato, eggplant, and chili pepper).

The relative abundance of several potential pathogenic fungi from the genera Diaporthe, Fusarium, Phomopsis, Plectosphaerella, Stemphylium, and Cryptococcus was also significantly higher in the diseased plant root, and several potential beneficial bacteria from the genera Pseudomonas, Streptomyces, Klebsiella, Enterobacter, Microbacterium, Bacillus, Chitinophaga, and Citrobacter were significantly enriched in the diseased plants.

Several functional genes involved in plant-microbiome signaling pathways were more abundant in the microbiome of the diseased root endosphere than in the healthy. For instance, the relative abundance of genes associated with methyl-accepting chemotaxis proteins (MCPs) was increased by 33.2–218.2% in the microbiome of the diseased root endosphere, compared with the healthy plant. The relative abundance of the functional genes associated with the downstream of MCPs, such as histidine kinase CheA and purine-binding chemotaxis protein CheW, also increased by 15.0–40.3% in the microbiome of the diseased root endosphere, compared with the healthy plant.

Several genes encoding MCPs associated with plant-microbiome signaling pathways were enriched in the microbiome of diseased root endosphere. MCPs are the predominant chemoreceptors in motile bacteria that alter the activity of CheA histidine kinase and the bacterial swimming behavior upon detection of specific chemicals . MCPs have been identified in typically beneficial bacteria, e.g., Bacillus subtilis and Pseudomonas spp. , which were also significantly enriched in diseased plant in the current study. Under stress conditions, such as pathogen invasion, a plant can attract distant beneficial microbes by actively releasing nonvolatile root exudates, such as amino acids, nucleotides, and long-chain organic acids, or by actively emitting blends of volatile organic compounds. The findings of the current study suggest that the MCP gene enrichment in diseased plants may be related to the response of MCP-producing bacteria to plant-released signal molecules. These bacteria would use MCPs to detect specific concentrations of these signaling molecules in the extracellular matrix, enabling directional accumulation of the bacteria to the plant. Further research will be required.

This study provides evidence on the critical role of bacterial taxa in the “cry for help” strategy of the host plant, in which the plant actively involves its microbial partners to maximize its or its offspring survival and growth under external stress.

A group from Department of Chemical Biology, School of Pharmaceutical Sciences, Peking University, Beijing 100191, China, etc. has reported about enzymatic modulation of Siglec-7 expression on NK cells to enhance NK effector functions for better antitumor therapeutics.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8393205/

The sialic acid-binding immunoglobulin-like lectins (Siglecs) found on immune cells (such as natural killer (NK) and T cells) have been designated as glyco-immune checkpoints.

However, the mechanism of this interaction-dependent suppression of antitumor immunity is not well understood. Authors found that an encounter with NK cells triggered the accumulation of Siglec-7 ligands (sialoglycans) on tumor cells. During the course of monitoring interactions between tumor cells and NK cells, we observed a rapid increase of sialoglycans on tumor cell surface within 2 hours. This remodeling occurs through both the transfer of sialoglycans from NK cells to target tumor cells and the accumulation of de novo synthesized sialoglycans on the tumor cells.

A transplantation of expanded allogeneic NK cells has emerged as a promising strategy for cancer treatment.
By enzymatically creating cis high-affinity sialo glycans on NK cell surfaces with cytidine-5′-monophospho (CMP)-^FTMCNeu5Ac and ST6Gal1, significant release of Siglec-7 from NK cell surface to the medium was observed during an immune activation by target cancer cells resulting in the enhancement of the NK effector functions for a better antitumor immunity.

Rhizobacteria coexist around the roots of plants, and the diverse and complex population of bacteria is called rhizosphere bacteria flora. This symbiotic relationship between the roots and the rhizosphere bacteria flora is often compared to the relationship between the intestines of animals and the gut microbiota. However, biologically speaking, plants do not have an organ called the intestine. Rather, if we consider the roots, rhizosphere bacteria, and soil as a whole, it would be better to think that this corresponds to the organ called the intestine.

Various organ-specific and disease-specific biomarkers are used in health and pathological diagnoses in human to see whether a person is healthy or unhealthy.
If this idea is applied to the roots and rhizobacteria of plants as it is, there might be markers that indicate the degree of intestinal health of plants, that is, rhizosphere markers . By using this idea, isn’t it possible to build a new plant soil monitoring system?

That is, in addition to the conventional indicators used in soil diagnosis, chemical indicators such as pH and water content, and physical indicators such as soil density, biological indicators, called rhizosphere markers is added.

Recent advances in gene analysis technology have made it possible to analyze the composition of rhizosphere bacterial flora without isolating and culturing rhizobacteria from soil. The interactions between individual bacteria have begun to be understand, for instance from a view point of helper bacteria that help Arbuscular mycorrhizal fungi. However, blog admin considers that there will be a limit in understanding such complex systems by reducing methods, and the composition of rhizosphere bacterial flora showing similar characteristics from a macro perspective will not be unique, but various.

Therefore, finding a rhizosphere marker from a macroscopic perspective that accurately represents the intestinal health of a plant and finding a way to control it could be the best way to manage plants. I think.