Biology subjects

Koma, T.

Publications and source records attributed to Koma, T..

3 recordsLinked to original sources

bioRxiv2022

A comprehensive list of the replication promoters of Bunyavirales reveals a unique promoter structure in Nairoviridae differing from other virus families

Bunyaviruses belong to the order Bunyavirales, the largest group of RNA viruses. They infect a wide variety of host species around the world, including plants, animals and humans, and pose a major threat to public health. Major families in the order Bunyavirales have tri-segmented negative-sense RNA genomes, the 5 and 3 ends of which form complementary strands that serve as a replication promoter. Elucidation of the mechanisms by which viral RNA-dependent RNA polymerase recognizes the promoter to initiates RNA synthesis is important for understanding viral replication and pathogenesis, and for developing antivirals. A list of replication promoter configuration patterns may provide details on the differences in the replication mechanisms among bunyaviruses. Here, by using public sequence data of all known bunyavirus species, we constructed a comprehensive list of the replication promoters comprising 40 nucleotides in both the 5 and 3 ends of the genome that form a specific complementary strand. We showed that among tri-segmented bunyaviruses, viruses belonging to the family Nairoviridae, including the highly pathogenic Crimean-Congo hemorrhagic fever virus, have evolved a GC-rich promoter structure that differs from that of other bunyaviruses. The unique promoter structure might be related to the large genome size of the family Nairoviridae among bunyaviruses. It is possible that the large genome architecture confers a pathogenic advantage. The promoter list provided in this report is expected to be useful for predicting virus family-specific replication mechanisms of segmented negative-sense RNA viruses.

microbiology↗

bioRxiv2022

Frequency of a nucleotide overhang at the 5' end of hemorrhagic fever mammarenavirus genomes in public sequence data

Mammarenaviruses, such as Lassa virus and South American hemorrhagic fever (SAHF) virus, cause severe hemorrhagic fevers in humans, and pose major threats to public health. Mammarenaviruses consist of a bi-segmented negative-sense RNA genome in which the 5 and 3 ends form complementary strands that serve as a replication promoter. Some mammarenaviruses have a nucleotide overhang at the 5 genome end. By examining the complementarity of 5 and 3 genome ends using public mammarenavirus genome sequences, we found that the 5 guanine overhang (5-G overhang) was present more frequently in Lassa and SAHF viruses than in other viruses. The 5-G overhang in the Lassa and SAHF virus sequences was found to be restricted to the L and S segments, respectively. If the genome end sequence data in the public database are accurate, the 5-G overhang may be related to the high pathogenicity of mammarenaviruses in humans.

microbiology↗

bioRxiv2021

Machupo virus with mutations in the transmembrane domain and glycosylation sites is attenuated and immunogenic in animal models of Bolivian Hemorrhagic Fever

Several highly pathogenic mammarenaviruses cause severe hemorrhagic and neurologic disease in humans, for which vaccines and antivirals are limited or unavailable. New World (NW) mammarenavirus Machupo virus (MACV) infection causes Bolivian hemorrhagic fever in humans. We previously reported that the disruption of specific N-linked glycan sites on the glycoprotein (GPC) partially attenuate MACV in an IFN-{beta}/{gamma} receptor knockout mouse model. However, some capability to induce neurological pathology still remained. Highly pathogenic Junin virus (JUNV) is another NW arenavirus closely related to MACV. A F427I substitution in the GPC transmembrane domain (TMD) rendered JUNV attenuated in a lethal mouse model after intracranial inoculation. In this study, we rationally designed and rescued a MACV containing mutations at two glycosylation sites and the corresponding F438I substitution in GPC TMD. The MACV mutant is fully attenuated in IFN-{beta}/{gamma} receptor knockout mice and outbred guinea pigs. Furthermore, inoculation with this mutant MACV fully protected guinea pigs from wild-type MACV lethal challenge. Lastly, we found the GPC TMD F438I substitution greatly impaired MACV growth in neuronal cell lines of mouse and human origins. Our results highlight the critical roles of the glycans and the TMD on the GPC in arenavirus virulence, which informs the rational design of potential vaccine candidates for highly pathogenic arenaviruses. ImportanceFor arenaviruses, the only vaccine available is the live-attenuated Candid#1 vaccine, a JUNV vaccine approved in Argentina. We and others have found that the glycans on GPC and the F427 residue in the GPC TMD are important for virulence of JUNV. Nevertheless, mutating either of them is not sufficient for full and stable attenuation of JUNV. Using reverse genetics, we disrupted specific glycosylation sites on MACV GPC, and also introduced the corresponding F438I substitution in the GPC TMD. This MACV mutant is fully attenuated in two animal models and protects animals from lethal infection. Thus, our studies highlight the feasibility of rational attenuation of highly pathogenic arenaviruses for vaccine development. Another important finding from this study is that the F438I substitution in GPC TMD could substantially affect MACV replication in neurons. Future studies are warranted to elucidate the underlying mechanism and the implication of this mutation in arenavirus neural tropism.

microbiology↗