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Ohki, S.

Publications and source records attributed to Ohki, S..

3 recordsLinked to original sources

Germinal center-derived broadly neutralizing antibodies adapt to SARS-CoV-2 antigenic drift

The outbreak of SARS-CoV-2 variant Omicron which harbors a striking number of mutations in the spike protein has been raising concerns about the effectiveness of vaccines and antibody treatment1. Here, we confirmed a substantial reduction in neutralizing potency against Omicron in all convalescent and vaccinated sera. However, we found that some people infected by the early strain show relatively higher neutralization to Omicron. From those B cells, we developed neutralizing antibodies inhibiting broad variants including Delta and Omicron. Unlike reported antibodies, one had an extremely large interface and widely covered receptor binding motif of spike, thereby interfering with diversified variants. Somatic mutations introduced by long-term germinal center reaction contributed to the key structure of antibodies and the universal interaction with spike variants. Recalling such rare B cells may confer sustainable protection against SARS-CoV-2 variants emerging one after another.

immunology↗

Fungal effector SIB1 of Colletotrichum orbiculare has unique structural features and can suppress plant immunity in Nicotiana benthamiana

Functional screening of effector candidates using a transient expression assay in Nicotiana benthamiana identified two virulence-related effectors, named SIB1 and SIB2 (Suppression of Immunity in N. benthamiana), of an anthracnose fungus Colletotrichum orbiculare, which infects both cucurbits and N. benthamiana. Agrobacterium-mediated transient expression of SIB1 or SIB2 increased the susceptibility of N. benthamiana to C. orbiculare, which suggested these effectors can suppress immune responses in N. benthamiana. The presence of SIB1 and SIB2 homologs was found to be limited to the genus Colletotrichum. SIB1 suppressed both the generation of reactive oxygen species (ROS) triggered by the bacterial pathogen-associated molecular pattern (PAMP), flg22, and the cell death response triggered by the Phytophthora infestans INF1 elicitin in N. benthamiana. We determined the NMR-based structure of SIB1 to obtain its structural insights. The three-dimensional structure of SIB1 comprises five {beta}-strands, each containing three disulfide bonds. The overall conformation was found to be a cylindrical shape, such as the well-known antiparallel {beta}-barrel structure. However, the {beta}-strands were found to display a unique topology, one pair of these {beta}-strands formed a parallel {beta}-sheet. These results suggest that the effector SIB1 present in Colletotrichum fungi has unique structural features and can suppress PAMP-triggered immunity (PTI) in N. benthamiana.

microbiology↗

Production of ORF8 protein from SARS-CoV-2 using an inducible virus-mediated expression-system in suspension-cultured tobacco BY-2 cells

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which spread worldwide in 2020, is an urgent problem to be overcome. The ORF8 of SARS-CoV-2 has been suggested to be associated with the symptoms of COVID-19, according to reports of clinical studies. However, little is known about the function of ORF8. As one of the ways to advance the functional analysis of ORF8, mass production of ORF8 with the correct three-dimensional structure is necessary. In this study, we attempted to produce ORF8 protein by chemically inducible protein production system using tobacco BY-2 cells. An ORF8-producing line was generated by the Agrobacterium method. As a result, the production of ORF8 of 8.8 {+/-} 1.4 mg/L of culture medium was confirmed. SDS-PAGE and nuclear magnetic resonance (NMR) analysis confirmed that the ORF8 produced by this system is a dimeric form with a single structure, unlike that produced in Escherichia coli. Furthermore, it was suggested that the ORF8 produced by this system was glycosylated. Through this study, we succeeded in producing ORF8 folded into a single structure in a chemically inducible protein production system using tobacco BY-2 cells. It is expected that the functional analysis of ORF8 will be advanced using the ORF8 produced by this system and that it will greatly contribute to the development of antibodies and therapeutic agents targeting ORF8.

plant biology↗