Gn protein expressed in plants for diagnosis of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) causes the highly fatal disease in humans. To facilitate diagnosis, the native form of subunit glycoprotein (Gn), a prime target for potential vaccines and therapies, was produced in Nicotiana benthamiana using a Bamboo mosaic virus-based vector system. By fusion with secretory signal tags, SSExt, derived from the extension protein, and the (SP)10 motif, the yield of the recombinant Gn (rGn) was remarkably increased to approximately 7 mg/kg infiltrated leaves. Ultimately, an rGn-based ELISA was successfully established for the detection of SFTSV-specific antibodies in serum samples from naturally infected monkeys. As validated with the reference method, the specificity and sensitivity of rGn-ELISA were 94% and 96%, respectively. In conclusion, utilizing well-suited fusion tags facilitates rGn production and purification in substantial quantities while preserving its antigenic properties. The rGn-ELISA, characterized by its commendable sensitivity and specificity could serve as a viable alternative diagnostic method for assessing SFTSV seroprevalence. KEY POINTS: • SFTSV Gn, fused with secretory signal tags, was expressed by the BaMV-based vector. • The plant fusion tags increased expression levels and eased the purification of rGn. • The rGn-ELISA was established and validated; its specificity and sensitivity > 94%.

Draft genome sequence of Yersinia pseudotuberculosis isolated from a wild rat in Japan

We report a draft genome sequence of Yersinia pseudotuberculosis isolated from the spleen of a wild rat from Mikura-shima Island, Japan. The bacterium was identified as serotype O:4b using PCR-based O-genotyping. These genomic data provide insights into the pathogenic potential of this strain in spontaneous outbreaks among wild animals.

Characterization of Omicron BA.4.6, XBB, and BQ.1.1 subvariants in hamsters

During the Omicron wave, previous variants such as BA.2, BA.4, and BA.5 were replaced by newer variants with additional mutations in the spike protein. These variants, BA.4.6, BQ.1.1, and XBB, have spread in different countries with different degrees of success. Here, we evaluated the replicative ability and pathogenicity of BA.4.6, BQ1.1, and XBB clinical isolates in male Syrian hamsters. Although we found no substantial differences in weight change among hamsters infected with these Omicron subvariants, the replicative ability of BQ.1.1 and XBB in lung tissue was higher than that of BA.4.6 and BA.5. Of note, BQ.1.1 was lethal in both male and female transgenic human ACE2 hamsters. In competition assays, XBB replicated better than BQ.1.1 in the nasal turbinate tissues of female hamsters previously infected with Omicron BA.2. These results suggest that newer Omicron subvariants in the XBB family are still evolving and should be closely monitored.

Mpox Neutralizing Antibody Response to LC16m8 Vaccine in Healthy Adults

Mpox Neutralizing Antibody Response to LC16m8 VaccineIn this study of 50 healthy volunteers in Japan, a smallpox vaccine (LC16m8) exhibited a robust neutralizing antibody response against two strains of the mpox virus. With a 94% "take" rate by day 14, seroconversion rates on day 28 were 72 and 70% against the Zr599 and Liberia strains, respectively, decreasing to 30% for both on day 168; no serious adverse events occurred.

Draft genome sequence including the capsule operon of a Bacillus cereus strain isolated from a patient with bacteremia in Japan

Bacillus cereus, which causes opportunistic infections in hospitals as well as food poisoning, is genetically similar to Bacillus anthracis. We herein report the draft genome including the capsule operon of B. cereus BCER1 isolated from the blood of a hospital patient in Japan.

Establishment of serological neutralizing tests using pseudotyped viruses for comprehensive detection of antibodies against all 18 lyssaviruses

Rabies is a fatal zoonotic, neurological disease caused by rabies lyssavirus (RABV) and other lyssaviruses. In this study, we established novel serological neutralizing tests (NT) based on vesicular stomatitis virus pseudotypes possessing all 18 known lyssavirus glycoproteins. Applying this system to comparative NT against rabbit sera immunized with current RABV vaccines, we showed that the current RABV vaccines fail to elicit sufficient neutralizing antibodies against lyssaviruses other than to those in phylogroup I. Furthermore, comparative NT against rabbit antisera for 18 lyssavirus glycoproteins showed glycoproteins of some lyssaviruses elicited neutralizing antibodies against a broad range of lyssaviruses. This novel testing system will be useful to comprehensively detect antibodies against lyssaviruses and evaluate their cross-reactivities for developing a future broad-protective vaccine.

Lethal severe fever with thrombocytopenia syndrome virus infection causes systemic germinal centre failure and massive T cell apoptosis in cats

Introduction

Severe fever with thrombocytopenia syndrome (SFTS) is a fatal viral disease characterized by high fever, thrombocytopenia, leukopenia, and multi-organ haemorrhage. Disruption of the humoral immune response and decreased lymphocyte numbers are thought to contribute to the disease severity. These findings have been obtained through the analysis of peripheral blood leukocytes in human patients, whereas analysis of lymph nodes has been limited. Thus, in this study, we characterized the germinal centre response and apoptosis in the lymph nodes of cats with fatal SFTS, because SFTS in cats well mimics the pathology of human SFTS.

Methods

Lymph node tissue sections collected during necropsy from seven fatal SFTS patients and five non-SFTS cases were used for histopathological analysis. Additionally, lymph node tissue sections collected from cats with experimental infection of SFTS virus (SFTSV) were also analysed.

Results

In the lymphoid follicles of cats with SFTS, a drastic decrease in Bcl6- and Ki67-positive germinal centre B cells was observed. Together, the number of T cells in the follicles was also decreased in SFTS cases. In the paracortex, a marked increase in cleaved-caspase3 positivity was observed in T cells. These changes were independent of the number of local SFTS virus-positive cell. Furthermore, the analysis of cats with experimental SFTSV infection revealed that the intrafollicular Bcl6- and CD3-positive cell numbers in cats with low anti-SFTSV antibody production were significantly lower than those in cats with high anti-SFTSV antibody production.

Discussion

These results suggest that dysfunction of the humoral response in severe SFTS was caused by the loss of germinal centre formation and massive apoptosis of T cells in the lymph nodes due to systemically circulating viruses.

Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Establishment and characterization of a novel lung cell line derived from the common bottlenose dolphin

Cetaceans are specialized marine mammals with a unique respiratory system adapted for diving behavior. Furthermore, respiratory diseases are commonly observed in these mammals. Nevertheless, much of their respiratory physiology remains unknown due to the limited supply and poor quality of their biological samples for research. In this study, we established a novel lung cell line, dLu, derived from the common bottlenose dolphin (Tursiops truncatus), which can prove useful in cetacean research, including for understanding the pathogenesis of respiratory diseases in cetaceans. The cells were cultured in a simple medium consisting of Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum. The morphology of the cells was fibroblast-like. dLu was produced by transfecting the simian virus 40 large T antigen into primary cultured cells. Although dLu exhibited approximately 80 cell divisions, it was unable to achieve complete immortalization, as the cells stopped proliferating beyond this number. dLu cells expressed toll-like receptor 3 but not toll-like receptor 4. Immunostimulation with poly(I:C) altered the gene expressions of interferon beta 1 and tumor necrosis factor alpha in dLu cells. In summary, dLu established in this study is a novel cetacean cell resource that can be easily cultured and is a useful in vitro tool in cetacean research, particularly for studying host immune responses in the lungs.

Macacine alphaherpesvirus 1 (B Virus) Infection in Humans, Japan, 2019

Two human patients with Macacine alphaherpesvirus 1 infection were identified in Japan in 2019. Both patients had worked at the same company, which had a macaque facility. The rhesus-genotype B virus genome was detected in cerebrospinal fluid samples from both patients.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Cross-neutralization activities of antibodies against 18 lyssavirus glycoproteins

Some lyssaviruses, including the rabies virus (RABV), induce lethal neurological symptoms in humans. However, commercial vaccines have only been evaluated for their efficacy against RABV and not against other lyssaviruses. To assess cross-reactivity among lyssaviruses, including RABV, sera from rabbits inoculated with human and animal RABV vaccines and polyclonal antibodies from rabbits immunized with expression plasmids of the glycoproteins of all 18 lyssaviruses were prepared, and cross-reactivity was evaluated via virus-neutralization tests using RABV, European bat lyssavirus-1 (EBLV-1), Duvenhage virus (DUVV), Mokola virus (MOKV), and Lagos bat virus (LBV). The sera against RABV vaccines showed cross-reactivity with EBLV-1 and DUVV, which both belong to phylogroup I. However, the reactivity with MOKV and LBV in phylogroup II was notably limited or below the detection level. Next, we compared the cross-reactivity of the polyclonal antibodies against all the lyssavirus glycoproteins. Polyclonal antibodies had high virus-neutralization titers against the same phylogroup, but not against different phylogroups. Our findings indicate that a new vaccine should be developed for pre- and post-exposure prophylaxis against lyssavirus infections.

High Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus Infection among the Dog Population in Thailand

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne zoonotic disease caused by the SFTS virus (SFTSV). In Thailand, three human cases of SFTS were reported in 2019 and 2020, but there was no report of SFTSV infection in animals. Our study revealed that at least 16.6% of dogs in Thailand were seropositive for SFTSV infection, and the SFTSV-positive dogs were found in several districts in Thailand. Additionally, more than 70% of the serum samples collected at one shelter possessed virus-neutralization antibodies against SFTSV and the near-complete genome sequences of the SFTSV were determined from one dog in the shelter. The dog SFTSV was genetically close to those from Thailand and Chinese patients and belonged to genotype J3. These results indicated that SFTSV has already spread among animals in Thailand.

Seroprevalence of SARS-CoV-2 antibodies in dogs and cats during the early and mid-pandemic periods in Japan

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has continued to circulate in humans since its emergence in 2019. While infection in humans continues, numerous spillover events to at least 32 animal species, including companion and zoo animals, have been reported. Since dogs and cats are highly susceptible to SARS-CoV-2 and have direct contact with their owners and other household members, it is important to know the prevalence of SARS-CoV-2 in dogs and cats. Here, we established an ELISA to detect serum antibodies against the receptor-binding domain and the ectodomain of the SARS-CoV-2 spike and nucleocapsid proteins. Using this ELISA, we assessed seroprevalence in 488 dog serum samples and 355 cat serum samples that were collected during the early pandemic period (between May and June of 2020) and 312 dog serum samples and 251 cat serum samples that were collected during the mid-pandemic period (between October 2021 and January 2022). We found that two dog serum samples (0.41%) collected in 2020, one cat serum sample (0.28%) collected in 2020, and four cat serum samples (1.6%) collected in 2021 were positive for antibodies against SARS-CoV-2. No dog serum samples collected in 2021 were positive for these antibodies. We conclude that the seroprevalence of SARS-CoV-2 antibodies in dogs and cats in Japan is low, suggesting that these animals are not a major SARS-CoV-2 reservoir.

Construction of a recombinant vaccine expressing Nipah virus glycoprotein using the replicative and highly attenuated vaccinia virus strain LC16m8

Nipah virus (NiV) is a highly pathogenic zoonotic virus that causes severe encephalitis and respiratory diseases and has a high mortality rate in humans (>40%). Epidemiological studies on various fruit bat species, which are natural reservoirs of the virus, have shown that NiV is widely distributed throughout Southeast Asia. Therefore, there is an urgent need to develop effective NiV vaccines. In this study, we generated recombinant vaccinia viruses expressing the NiV glycoprotein (G) or fusion (F) protein using the LC16m8 strain, and examined their antigenicity and ability to induce immunity. Neutralizing antibodies against NiV were successfully induced in hamsters inoculated with LC16m8 expressing NiV G or F, and the antibody titers were higher than those induced by other vaccinia virus vectors previously reported to prevent lethal NiV infection. These findings indicate that the LC16m8-based vaccine format has superior features as a proliferative vaccine compared with other poxvirus-based vaccines. Moreover, the data collected over the course of antibody elevation during three rounds of vaccination in hamsters provide an important basis for the clinical use of vaccinia virus-based vaccines against NiV disease. Trial Registration: NCT05398796.

Epidemiology of Severe Fever with Thrombocytopenia Syndrome in Dogs and Cats in Taiwan

Severe Fever with Thrombocytopenia Syndrome (SFTS), caused by the SFTS Virus (SFTSV), is a global health threat. SFTSV in Taiwan has only been reported in ruminants and wild animals. Thus, we aimed to investigate the infection statuses of dogs and cats, the animals with closer human interactions. Overall, the SFTSV RNA prevalence was 23% (170/735), with dogs showing a 25.9% (111/429) prevalence and cats at 19.3% (59/306) prevalence. Noticeably, the prevalence in stray animals (39.8% 77/193) was significantly higher than in domesticated ones (17.2%, 93/542). Among the four categories analyzed, the highest SFTSV prevalence was found in the stray dogs at 53.9% (120/193), significantly higher than the 24.2% prevalence noted in stray cats. In contrast, domesticated animals exhibited similar prevalence rates, with 17.1% for dogs and 17.2% for cats. It is noteworthy that in the domesticated animal groups, a significantly elevated prevalence (45%, 9/20) was observed among cats exhibiting thrombocytopenia compared to those platelet counts in the reference range (4.8%, 1/21). The high infection rate in stray animals, especially stray dogs, indicated that exposure to various outdoor environments influences the prevalence of infections. Given the higher human interaction with dogs and cats, there is a need for proactive measures to reduce the risk associated with the infection of SFTSV in both animals and humans.

Antiviral efficacy against and replicative fitness of an XBB.1.9.1 clinical isolate

The emergence and spread of new SARS-CoV-2 variants with mutations in the spike protein, such as the XBB.1.5 and XBB.1.9.1 sublineages, raise concerns about the efficacy of current COVID-19 vaccines and therapeutic monoclonal antibodies (mAbs). In this study, none of the mAbs we tested neutralized XBB.1.9.1 or XBB.1.5, even at the highest concentration used. We also found that the bivalent mRNA vaccine could enhance humoral immunity against XBB.1.9.1, but that XBB.1.9.1 and XBB.1.5 still evaded humoral immunity induced by vaccination or infection. Moreover, the susceptibility of XBB.1.9.1 to remdesivir, molnupiravir, nirmatrelvir, and ensitrelvir was similar to that of the ancestral strain and the XBB.1.5 isolate in vitro. Finally, we found the replicative fitness of XBB.1.9.1 to be similar to that of XBB.1.5 in hamsters. Our results suggest that XBB.1.9.1 and XBB.1.5 have similar antigenicity and replicative ability, and that the currently available COVID-19 antivirals remain effective against XBB.1.9.1.

A new subtropical species of goby of the genus Luciogobius (Gobiidae) from southwestern Japan

Luciogobius griseus n. sp., belonging to the Luciogobius platycephalus complex, is described on the basis of 40 specimens from the Nansei Islands, southwestern Japan (subtropical area). The new species is generally found in intertidal gravel sediments subjected to freshwater runoff from springs on coastal lines or river mouths and is characterized by the following combination of characters: total second dorsal-fin rays 912 (modally 11); total anal-fin rays usually 1214 (modally 13); pectoral-fin rays 1215 (modally 13); vertebrae 17 or 18 + 23 or 24 = 4042 (18 + 23 = 41); uppermost 24 (23) rays on pectoral fin free; 812 pectoral-fin rays branched (uppermost free rays and sometimes lowermost ray unbranched); pectoral-fin membrane not strongly concave anteriorly (except for free rays); pelvic fins united, forming a disk; head relatively short, 13.920.8% of standard length (SL); relatively short pre-pelvic fin, length 14.422.1% of SL; relatively long pre-dorsal fin, length 68.972.9% of SL; relatively long pre-anal fin, length 63.567.7% of SL; relatively short pelvic fin, length 2.84.7% of SL; distance between posterior end of pelvic fin and anus relatively long, 32.036.4% of SL (aforementioned morphometrics each distinguishing L. griseus n. sp. from other species in the L. platycephalus complex); and fresh specimens with greenish dark brown or gray body. A key to the L. platycephalus complex is provided, together with limited descriptions and remarks on the other two members of the complex.

Pet Animals Were Infected with SARS-CoV-2 from Their Owners Who Developed COVID-19: Case Series Study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among pets owned by coronavirus disease 2019 (COVID-19) patients has been reported around the world. However, how often the animals are exposed to SARS-CoV-2 by their owners is still unclear. We have collected swab samples from COVID-19 patients' pets and performed real-time RT-PCR to detect the viral genome. In total, 8 of 53 dogs (15.1%) and 5 of 34 cats (14.7%) tested positive for the SARS-CoV-2 N gene. The result of a virus neutralization (VN) test also showed VN antibodies in four cats and six dogs. Our results indicate that the virus often passed from infected owners to their pets, which then excreted the virus despite having no or mild clinical signs.

Potential Anti-Mpox Virus Activity of Atovaquone, Mefloquine, and Molnupiravir, and Their Potential Use as Treatments

BACKGROUND

Mpox virus (MPXV) is a zoonotic orthopoxvirus and caused an outbreak in 2022. Although tecovirimat and brincidofovir are approved as anti-smallpox drugs, their effects in mpox patients have not been well documented. In this study, by a drug repurposing approach, we identified potential drug candidates for treating mpox and predicted their clinical impacts by mathematical modeling.

METHODS

We screened 132 approved drugs using an MPXV infection cell system. We quantified antiviral activities of potential drug candidates by measuring intracellular viral DNA and analyzed the modes of action by time-of-addition assay and electron microscopic analysis. We further predicted the efficacy of drugs under clinical concentrations by mathematical simulation and examined combination treatment.

RESULTS

Atovaquone, mefloquine, and molnupiravir exhibited anti-MPXV activity, with 50% inhibitory concentrations of 0.51-5.2 μM, which was more potent than cidofovir. Whereas mefloquine was suggested to inhibit viral entry, atovaquone and molnupiravir targeted postentry processes. Atovaquone was suggested to exert its activity through inhibiting dihydroorotate dehydrogenase. Combining atovaquone with tecovirimat enhanced the anti-MPXV effect of tecovirimat. Quantitative mathematical simulations predicted that atovaquone can promote viral clearance in patients by 7 days at clinically relevant drug concentrations.

CONCLUSIONS

These data suggest that atovaquone would be a potential candidate for treating mpox.

Identification of IMP Dehydrogenase as a Potential Target for Anti-Mpox Virus Agents

Mpox virus (formerly monkeypox virus [MPXV]) is a neglected zoonotic pathogen that caused a worldwide outbreak in May 2022. Given the lack of an established therapy, the development of an anti-MPXV strategy is of vital importance. To identify drug targets for the development of anti-MPXV agents, we screened a chemical library using an MPXV infection cell assay and found that gemcitabine, trifluridine, and mycophenolic acid (MPA) inhibited MPXV propagation. These compounds showed broad-spectrum anti-orthopoxvirus activities and presented lower 90% inhibitory concentrations (0.026 to 0.89 μM) than brincidofovir, an approved anti-smallpox agent. These three compounds have been suggested to target the postentry step to reduce the intracellular production of virions. Knockdown of IMP dehydrogenase (IMPDH), the rate-limiting enzyme of guanosine biosynthesis and a target of MPA, dramatically reduced MPXV DNA production. Moreover, supplementation with guanosine recovered the anti-MPXV effect of MPA, suggesting that IMPDH and its guanosine biosynthetic pathway regulate MPXV replication. By targeting IMPDH, we identified a series of compounds with stronger anti-MPXV activity than MPA. This evidence shows that IMPDH is a potential target for the development of anti-MPXV agents. IMPORTANCE Mpox is a zoonotic disease caused by infection with the mpox virus, and a worldwide outbreak occurred in May 2022. The smallpox vaccine has recently been approved for clinical use against mpox in the United States. Although brincidofovir and tecovirimat are drugs approved for the treatment of smallpox by the U.S. Food and Drug Administration, their efficacy against mpox has not been established. Moreover, these drugs may present negative side effects. Therefore, new anti-mpox virus agents are needed. This study revealed that gemcitabine, trifluridine, and mycophenolic acid inhibited mpox virus propagation and exhibited broad-spectrum anti-orthopoxvirus activities. We also suggested IMP dehydrogenase as a potential target for the development of anti-mpox virus agents. By targeting this molecule, we identified a series of compounds with stronger anti-mpox virus activity than mycophenolic acid.

Structural delineation and computational design of SARS-CoV-2-neutralizing antibodies against Omicron subvariants

SARS-CoV-2 Omicron subvariants have evolved to evade receptor-binding site (RBS) antibodies that exist in diverse individuals as public antibody clones. We rationally selected RBS antibodies resilient to mutations in emerging Omicron subvariants. Y489 was identified as a site of virus vulnerability and a common footprint of broadly neutralizing antibodies against the subvariants. Multiple Y489-binding antibodies were encoded by public clonotypes and additionally recognized F486, potentially accounting for the emergence of Omicron subvariants harboring the F486V mutation. However, a subclass of antibodies broadly neutralized BA.4/BA.5 variants via hydrophobic binding sites of rare clonotypes along with high mutation-resilience under escape mutation screening. A computationally designed antibody based on one of the Y489-binding antibodies, NIV-10/FD03, was able to bind XBB with any 486 mutation and neutralized XBB.1.5. The structural basis for the mutation-resilience of this Y489-binding antibody group may provide important insights into the design of therapeutics resistant to viral escape.

Low Replication Efficiency of a Japanese Rabbit Hepatitis E Virus Strain in the Human Hepatocarcinoma Cell Line PLC/PRF/5

A Japanese rabbit hepatitis E virus (HEV) strain, JP-59, has been identified in a feral rabbit. When this virus was transmitted to a Japanese white rabbit, it caused persistent HEV infection. The JP-59 strain shares an <87.5% nucleotide sequence identity with other rabbit HEV strains. Herein, to isolate JP-59 by cell culture, we used a 10% stool suspension recovered from a JP-59-infected Japanese white rabbit and contained 1.1 × 10⁷ copies/mL of the viral RNA and using it to infect a human hepatocarcinoma cell line, PLC/PRF/5. No sign of virus replication was observed. Although long-term virus replication was observed in PLC/PRF/5 cells inoculated with the concentrated and purified JP-59 containing a high titer of viral RNA (5.1 × 10⁸ copies/mL), the viral RNA of JP-59c that was recovered from the cell culture supernatants was <7.1 × 10⁴ copies/mL during the experiment. The JP-59c strain did not infect PLC/PRF/5 cells, but its intravenous inoculation caused persistent infection in rabbits. The nucleotide sequence analyses of the virus genomes demonstrated that a total of 18 nucleotide changes accompanying three amino acid mutations occurred in the strain JP-59c compared to the original strain JP-59. These results indicate that a high viral RNA titer was required for JP-59 to infect PLC/PRF/5 cells, but its replication capability was extremely low. In addition, the ability of rabbit HEVs to multiply in PLC/PRF/5 cells varied depending on the rabbit HEV strains. The investigations of cell lines that are broadly susceptible to rabbit HEV and that allow the efficient propagation of the virus are thus needed.

Saturation time of exposure interval for cross-neutralization response to SARS-CoV-2: Implications for vaccine dose interval

Evaluating the serum cross-neutralization responses after breakthrough infection with various SARS-CoV-2 variants provides valuable insight for developing variant-proof COVID-19 booster vaccines. However, fairly comparing the impact of breakthrough infections with distinct epidemic timing on cross-neutralization responses, influenced by the exposure interval between vaccination and infection, is challenging. To compare the impact of pre-Omicron to Omicron breakthrough infection, we estimated the effects on cross-neutralizing responses by the exposure interval using Bayesian hierarchical modeling. The saturation time required to generate saturated cross-neutralization responses differed by variant, with variants more antigenically distant from the ancestral strain requiring longer intervals of 2-4 months. The breadths of saturated cross-neutralization responses to Omicron lineages were comparable in pre-Omicron and Omicron breakthrough infections. Our results highlight the importance of vaccine dosage intervals of 4 months or longer, regardless of the antigenicity of the exposed antigen, to maximize the breadth of serum cross-neutralization covering SARS-CoV-2 Omicron lineages.

Morphogenesis of Bullet-Shaped Rabies Virus Particles Regulated by TSG101

Viral protein assembly and virion budding are tightly regulated to enable the proper formation of progeny virions. At this late stage in the virus life cycle, some enveloped viruses take advantage of the host endosomal sorting complex required for transport (ESCRT) machinery, which contributes to the physiological functions of membrane modulation and abscission. Bullet-shaped viral particles are unique morphological characteristics of rhabdoviruses; however, the involvement of host factors in rhabdovirus infection and, specifically, the molecular mechanisms underlying virion formation are not fully understood. In the present study, we used a small interfering RNA (siRNA) screening approach and found that the ESCRT-I component TSG101 contributes to the propagation of rabies virus (RABV). We demonstrated that the matrix protein (M) of RABV interacts with TSG101 via the late domain containing the PY and YL motifs, which are conserved in various viral proteins. Loss of the YL motif in the RABV M or the downregulation of host TSG101 expression resulted in the intracellular aggregation of viral proteins and abnormal virus particle formation, indicating a defect in the RABV assembly and budding processes. These results indicate that the interaction of the RABV M and TSG101 is pivotal for not only the efficient budding of progeny RABV from infected cells but also for the bullet-shaped virion morphology. IMPORTANCE Enveloped viruses bud from cells with the host lipid bilayer. Generally, the membrane modulation and abscission are mediated by host ESCRT complexes. Some enveloped viruses utilize their late (L-) domain to interact with ESCRTs, which promotes viral budding. Rhabdoviruses form characteristic bullet-shaped enveloped virions, but the underlying molecular mechanisms involved remain elusive. Here, we showed that TSG101, one of the ESCRT components, supports rabies virus (RABV) budding and proliferation. TSG101 interacted with RABV matrix protein via the L-domain, and the absence of this interaction resulted in intracellular virion accumulation and distortion of the morphology of progeny virions. Our study reveals that virion formation of RABV is highly regulated by TSG101 and the virus matrix protein.

Characterization of SARS-CoV-2 Omicron BA.2.75 clinical isolates

The prevalence of the Omicron subvariant BA.2.75 rapidly increased in India and Nepal during the summer of 2022, and spread globally. However, the virological features of BA.2.75 are largely unknown. Here, we evaluated the replicative ability and pathogenicity of BA.2.75 clinical isolates in Syrian hamsters. Although we found no substantial differences in weight change among hamsters infected with BA.2, BA.5, or BA.2.75, the replicative ability of BA.2.75 in the lungs is higher than that of BA.2 and BA.5. Of note, BA.2.75 causes focal viral pneumonia in hamsters, characterized by patchy inflammation interspersed in alveolar regions, which is not observed in BA.5-infected hamsters. Moreover, in competition assays, BA.2.75 replicates better than BA.5 in the lungs of hamsters. These results suggest that BA.2.75 can cause more severe respiratory disease than BA.5 and BA.2 in a hamster model and should be closely monitored.

Capnocytophaga catalasegens sp. nov., isolated from feline oral cavities

Three bacterial strains, KC07075, KC07079 and KC07084^T, were isolated from the oral cavity of cats in 2007 in Japan. These strains were Gram-negative rods, exhibited gliding motility, grew in air with 5 % CO₂, and showed oxidase activity, but not catalase activity. The 16S rRNA gene sequences of the three strains were 100 % identical. The 16S rRNA gene sequence of strain KC07084^T showed 92.1 and 91.9% identity to the type strains of Capnocytophaga canis and Capnocytophaga felis, respectively, and showed 89.3-91.6% identity to other Capnocytophaga species. The major cellular fatty acids of strain KC07084^T were iso-C_15 : 0 (58.4 %) and summed feature 11 (13.1 %). The G+C content of DNA from strain KC07084^T was 33.7 mol%, and the genome size was 2.92 Mbp. Strains KC07075, KC07079 and KC07084^T showed digital DNA-DNA hybridization values (dDDH) values of 99.9 % and average nucleotide identity (ANI) values of 99.98 % with each other, strain KC07084^T had dDDH values of 18.7-28.2 % and ANI values of 67.12-72.30 % to the type strains of other Capnocytophaga species. All known species of the genus Capnocytophaga inhabiting the oral cavity of dogs and cats have catalase activity, but the three strains, including type strain KC07084^T, lacked catalase activity. These results of the phylogenetic analysis of the 16S rRNA gene sequence, biochemical characteristics, and dDDH and ANI values suggest that strain KC07084^T represents a novel species. We propose the name Capnocytophaga catalasegens sp. nov., with KC07084^T as the type strain (=JCM 32682^T=DSM 107252^T).

Simple and rapid detection of severe fever with thrombocytopenia syndrome virus in cats by reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay using a dried reagent

Severe fever with thrombocytopenia syndrome virus (SFTSV) causes lethal hemorrhagic diseases in human, cats, and dogs. Several human cases involving direct transmission of SFTSV from diseased animals have been reported. Therefore, rapid diagnosis in veterinary clinics is important for preventing animal-to-human transmission. Previously, we developed a simplified reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for human that does not require RNA extraction for detecting the SFTSV genome. In this study, we improved the simplified RT-LAMP assay for cats by introducing a dried reaction reagent and investigated the applicability of this method for diagnosing SFTS in cats. SFTSV RNA was detected in 11 of 12 cats naturally infected with SFTSV by RT-LAMP assay using both liquid and dried reagents. The RT-LAMP assay using liquid and dried reagents was also applicable to the detection of SFTSV genes 3-4 days after challenge in cats experimentally infected with SFTSV. The minimum copy number of SFTSV genes for 100% detection using the RT-LAMP assay with liquid and dried reagents was 4.3 × 10⁴ and 9.6 × 10⁴ copies/mL, respectively. Although the RT-LAMP assay using the dried reagent was less sensitive than that using the liquid reagent, it was sufficiently sensitive to detect SFTSV genes in cats with acute-phase SFTS. As the simplified RT-LAMP assay using a dried reagent enables detection of SFTSV genes more readily than the assay using a liquid reagent, it is applicable for use in veterinary clinics.

Specific COVID-19 risk behaviors and the preventive effect of personal protective equipment among healthcare workers in Japan

As coronavirus disease 2019 (COVID-19) outbreaks in healthcare facilities are a serious public health concern, we performed a case-control study to investigate the risk of COVID-19 infection in healthcare workers. We collected data on participants' sociodemographic characteristics, contact behaviors, installation status of personal protective equipment, and polymerase chain reaction testing results. We also collected whole blood and assessed seropositivity using the electrochemiluminescence immunoassay and microneutralization assay. In total, 161 (8.5%) of 1,899 participants were seropositive between August 3 and November 13, 2020. Physical contact (adjusted odds ratio 2.4, 95% confidence interval 1.1-5.6) and aerosol-generating procedures (1.9, 1.1-3.2) were associated with seropositivity. Using goggles (0.2, 0.1-0.5) and N95 masks (0.3, 0.1-0.8) had a preventive effect. Seroprevalence was higher in the outbreak ward (18.6%) than in the COVID-19 dedicated ward (1.4%). Results showed certain specific risk behaviors of COVID-19; proper infection prevention practices reduced these risks.

Epidemiological Associations between Rabies Vaccination and Dog Owner Characteristics

BACKGROUND

The annual rabies vaccination coverage in dogs among 47 prefectures in Japan has been reported to range from 42.3% to 92.4%, and the overall coverage has been steadily declining. Given the presence of unregistered dogs and the small number of stray dogs, the true vaccination coverage is likely to be even lower.

METHODS

We conducted a cross-sectional survey of dog owners to identify the owner characteristics associated with dog rabies vaccination. People in Japan who currently own dogs were recruited and answered a questionnaire consisting of four sections: (i) demographic characteristics, (ii) education history associated with medicine, (iii) factors related to veterinary services, and (iv) dog characteristics.

RESULTS

A total of 534 dog owners covering 629 dogs were surveyed. Vaccination within the prior 12 months was the major outcome (56.1%). The associated variables were (a) owner education level, (b) knowledge about mandatory vaccination, (c) having a family veterinary clinic, (d) frequency of visiting a veterinary clinic, and (e) having ever been advised to vaccinate their dog.

CONCLUSIONS

Although causality cannot be implied, our findings indicate improving owners' knowledge about mandatory vaccination, facilitating attachment to a veterinary clinic, and veterinarians providing vaccination advice might increase the uptake of dog rabies vaccination. The finding in Japan did not deviate from Asian and African countries with rabies, and the sample estimate of annual vaccination coverage was lower than the reported estimate among registered dogs.

Transition of dominant canine parvovirus genotype from 2b to 2c in Vietnamese dogs

Canine parvovirus (CPV) is one of the most important pathogens causing enteritis in dogs. Although there have been a few reports of CPV in Vietnam, recent information on CPV infection in domestic dogs in Vietnam is limited. Faecal samples collected from 30 diarrheic and 50 healthy dogs were examined by PCR for detection of CPV DNA. The prevalence of CPV in diarrheic dogs (43.3%, 13/30) was significantly higher than in healthy dogs (4.0%, 2/50), indicating that CPV was a major cause of diarrhoea in domestic dogs. Genotyping of 15 CPV strains showed that both CPV‑2a and CPV‑2c were circulating and that CPV‑2c was a dominant CPV variant in Vietnam. Virus isolation was performed from faecal samples using A72/cSLAM cells, and nine CPV strains were successfully isolated. The dominant genotype spreading among Vietnamese dogs has changed from CPV‑2b to CPV‑2c.

Characterization of SARS-CoV-2 Omicron BA.4 and BA.5 isolates in rodents

The BA.2 sublineage of the SARS-CoV-2 Omicron variant has become dominant in most countries around the world; however, the prevalence of BA.4 and BA.5 is increasing rapidly in several regions. BA.2 is less pathogenic in animal models than previously circulating variants of concern^1-4. Compared with BA.2, however, BA.4 and BA.5 possess additional substitutions in the spike protein, which play a key role in viral entry, raising concerns that the replication capacity and pathogenicity of BA.4 and BA.5 are higher than those of BA.2. Here we have evaluated the replicative ability and pathogenicity of BA.4 and BA.5 isolates in wild-type Syrian hamsters, human ACE2 (hACE2) transgenic hamsters and hACE2 transgenic mice. We have observed no obvious differences among BA.2, BA.4 and BA.5 isolates in growth ability or pathogenicity in rodent models, and less pathogenicity compared to a previously circulating Delta (B.1.617.2 lineage) isolate. In addition, in vivo competition experiments revealed that BA.5 outcompeted BA.2 in hamsters, whereas BA.4 and BA.2 exhibited similar fitness. These findings suggest that BA.4 and BA.5 clinical isolates have similar pathogenicity to BA.2 in rodents and that BA.5 possesses viral fitness superior to that of BA.2.

Larval study revealed diversity and life-history traits of crypto-benthic eel gobies

Because adult and juvenile eel gobies usually hide within the burrows of muddy substrates, their diversity and life history have not yet been fully elucidated. We investigated larval specimens of the eel gobies collected on Okinawa Island in southern Japan. The genus Trypauchenopsis was previously thought to consist of only one species, but our larval collection identified two species, Trypauchenopsis limicola and Trypauchenopsis intermedia, distinguished by their species-specific melanophore arrangements and differences in their fin-ray counts. Taenioides kentalleni were previously known from only two specimens worldwide. A third specimen of this species has now been added from the larval collection. In addition to the three species above, Taenioides gracilis and Caragobius urolepis were identified and the larval morphologies of the five species were described for the first time. All the larvae collected in the present study were at late postflexion stage. T. limicola, T. intermedia and T. gracilis were presumably collected in the estuaries and beaches when approaching their adult habitats at the end of pelagic life. They were 8.5-10.3 mm in standard length, and otolith analysis suggests that their pelagic larval durations are a little longer than 1 month (average 34-37 days). The larval occurrence suggested that the spawning season of T. limicola is May-December, when the water temperature is warmer than approximately 20°C. Our work reveals that studying the larval stage can provide new information on the taxonomy and life history of the elusive cryptobenthic fish.

Increased Risk of Infection with Severe Fever with Thrombocytopenia Virus among Animal Populations on Tsushima Island, Japan, Including an Endangered Species, Tsushima Leopard Cats

To investigate the seroprevalence of severe fever with thrombocytopenia syndrome (SFTS) among wild and companion animals on Tsushima Island, Japan, SFTS virus (SFTSV)-specific ELISA and virus-neutralizing tests were conducted on 50 wild boars, 71 Sika deer, 84 dogs, 323 domestic cats, and 6 Tsushima leopard cats. In total, 1 wild boar (1.8%), 2 dogs (2.4%), 7 domestic cats (2.2%), and 1 Tsushima leopard cat (16.7%) were positive for anti-SFTSV antibodies. Among the 11 positive animals, 10 were collected after 2019, and all were found on the southern part of the island. SFTSV, thus far, seems to be circulating within a limited area of Tsushima Island. To protect humans and animals, including endangered Tsushima leopard cats, from SFTSV infection, countermeasures are needed to prevent the spread of SFTSV on Tsushima Island.

Detection of current-sheet and bipolar ion flows in a self-generated antiparallel magnetic field of laser-produced plasmas for magnetic reconnection research

Magnetic reconnection in laser-produced magnetized plasma is investigated by using optical diagnostics. The magnetic field is generated via the Biermann battery effect, and the inversely directed magnetic field lines interact with each other. It is shown by self-emission measurement that two colliding plasmas stagnate on a midplane, forming two planar dense regions, and that they interact later in time. Laser Thomson scattering spectra are distorted in the direction of the self-generated magnetic field, indicating asymmetric ion velocity distribution and plasma acceleration. In addition, the spectra perpendicular to the magnetic field show different peak intensity, suggesting an electron current formation. These results are interpreted as magnetic field dissipation, reconnection, and outflow acceleration. Two-directional laser Thomson scattering is, as discussed here, a powerful tool for the investigation of microphysics in the reconnection region.

Essential role of TMPRSS2 in SARS-CoV-2 infection in murine airways

In cultured cells, SARS-CoV-2 infects cells via multiple pathways using different host proteases. Recent studies have shown that the furin and TMPRSS2 (furin/TMPRSS2)-dependent pathway plays a minor role in infection of the Omicron variant. Here, we confirm that Omicron uses the furin/TMPRSS2-dependent pathway inefficiently and enters cells mainly using the cathepsin-dependent endocytosis pathway in TMPRSS2-expressing VeroE6/TMPRSS2 and Calu-3 cells. This is the case despite efficient cleavage of the spike protein of Omicron. However, in the airways of TMPRSS2-knockout mice, Omicron infection is significantly reduced. We furthermore show that propagation of the mouse-adapted SARS-CoV-2 QHmusX strain and human clinical isolates of Beta and Gamma is reduced in TMPRSS2-knockout mice. Therefore, the Omicron variant isn't an exception in using TMPRSS2 in vivo, and analysis with TMPRSS2-knockout mice is important when evaluating SARS-CoV-2 variants. In conclusion, this study shows that TMPRSS2 is critically important for SARS-CoV-2 infection of murine airways, including the Omicron variant.

Lethal Disease in Dogs Naturally Infected with Severe Fever with Thrombocytopenia Syndrome Virus

Severe fever with the thrombocytopenia syndrome virus (SFTSV) causes fatal disease in humans, cats, and cheetahs. In this study, the information on seven dogs with SFTS was summarized. All dogs showed anorexia, high fever, leukopenia, and thrombocytopenia, two dogs showed vomiting and loose stool, and five dogs had tick parasites. All dogs also had a history of outdoor activity. The SFTSV gene was detected in all dogs. Remarkably, three dogs (43%) died. SFTSV was isolated from six dogs and the complete genomes were determined. A significant increase in anti-SFTSV-IgG antibodies was observed in two dogs after recovery, and anti-SFTSV-IgM antibodies were detected in four dogs in the acute phase. Using an ELISA cut-off value of 0.410 to discriminate between SFTSV-negative and positive dogs, the detection of anti-SFTSV-IgM antibodies was useful for the diagnosis of dogs with acute-phase SFTS. Four out of the ninety-eight SFTSV-negative dogs possessed high anti-SFTSV IgG antibody titers, indicating that some dogs can recover from SFTSV infection. In conclusion, SFTSV is lethal in some dogs, but many dogs recover from SFTSV infection.

WO3 Photocatalyst Containing Copper Inactivates SARS-CoV-2 Pango Lineage A and Omicron BA.2 Variant in Visible Light and in Darkness

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019, which has been a global pandemic. Since SARS-CoV-2 is transmitted through contaminated surfaces and aerosols, environmental disinfection is important to block the spread of the virus. Photocatalysts are attractive tools for virus inactivation and are widely used as air purifiers and coating materials. However, photocatalysts are inactive in the dark, and some of them need to be excited with light of a specific wavelength. Therefore, photocatalysts that can effectively inactivate SARS-CoV-2 in indoor environments are needed. Here, we show that a WO3 photocatalyst containing copper inactivated the SARS-CoV-2 WK-521 strain (Pango lineage A) upon irradiation with white light in a time- and concentration-dependent manner. Additionally, this photocatalyst also inactivated SARS-CoV-2 in dark conditions due to the antiviral effect of copper. Furthermore, this photocatalyst inactivated not only the WK-521 strain but also the Omicron variant BA.2. These results indicate that the WO3 photocatalyst containing copper can inactivate indoor SARS-CoV-2 regardless of the variant, in visible light or darkness, making it an effective tool for controlling the spread of SARS-CoV-2.

Characterization and antiviral susceptibility of SARS-CoV-2 Omicron BA.2

The recent emergence of SARS-CoV-2 Omicron (B.1.1.529 lineage) variants possessing numerous mutations has raised concerns of decreased effectiveness of current vaccines, therapeutic monoclonal antibodies and antiviral drugs for COVID-19 against these variants1,2. The original Omicron lineage, BA.1, prevailed in many countries, but more recently, BA.2 has become dominant in at least 68 countries3. Here we evaluated the replicative ability and pathogenicity of authentic infectious BA.2 isolates in immunocompetent and human ACE2-expressing mice and hamsters. In contrast to recent data with chimeric, recombinant SARS-CoV-2 strains expressing the spike proteins of BA.1 and BA.2 on an ancestral WK-521 backbone4, we observed similar infectivity and pathogenicity in mice and hamsters for BA.2 and BA.1, and less pathogenicity compared with early SARS-CoV-2 strains. We also observed a marked and significant reduction in the neutralizing activity of plasma from individuals who had recovered from COVID-19 and vaccine recipients against BA.2 compared to ancestral and Delta variant strains. In addition, we found that some therapeutic monoclonal antibodies (REGN10987 plus REGN10933, COV2-2196 plus COV2-2130, and S309) and antiviral drugs (molnupiravir, nirmatrelvir and S-217622) can restrict viral infection in the respiratory organs of BA.2-infected hamsters. These findings suggest that the replication and pathogenicity of BA.2 is similar to that of BA.1 in rodents and that several therapeutic monoclonal antibodies and antiviral compounds are effective against Omicron BA.2 variants.

Roles of raccoons in the transmission cycle of severe fever with thrombocytopenia syndrome virus

The present study investigated severe fever with thrombocytopenia syndrome virus (SFTSV) infection in raccoons in Wakayama Prefecture from 2007 to 2019. To perform surveillance, an enzyme-linked immunosorbent assay (ELISA) was established, and the sensitivity and specificity of the ELISA were 100% in comparison with a 50% focus-reduction neutralization assay. Using the established ELISA, we performed serosurveillance of SFTSV infection in 2,299 raccoons in Tanabe region, Wakayama Prefecture from 2007 to 2019. The first anti-SFTSV-positive raccoon was captured in October 2009. The seroprevalence of SFTSV infection was <10% between April 2009 and March 2013, 23.9% between April 2013 and March 2014, 37.5% between April, 2014 and March 2015, and over 50% from April 2015. Next, we performed detection of SFTSV genes in sera of raccoons captured in Wakayama Prefecture after April 2013. The results indicated that 2.4% of raccoons were positive for SFTSV genes and that the frequency of SFTSV infection among raccoons between January and March (0.7%) was lower than that between April and June (3.4%). In addition, virus genes were detected from many specimens, including sera and feces of two raccoons, and viral antigens were detected in lymphoid cells in lymphoid follicles in the colon by immunohistochemical staining. In conclusion, SFTSV had recently invaded the area and had rapidly spread among wild animals. The first patient in this area was reported in June 2014, indicating that raccoons are good sentinels for assessing the risk of SFTSV in humans.

Safety and immunogenicity of the Pfizer/BioNTech SARS-CoV-2 mRNA third booster vaccine dose against the SARS-CoV-2 BA.1 and BA.2 Omicron variants

Background

The Omicron variant of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) was identified in Japan in November 2021. This variant contains up to 36 mutations in the spike protein, the target of neutralizing antibodies, and can escape vaccine-induced immunity. A booster vaccination campaign began with healthcare workers and high-risk groups. The safety and immunogenicity of the three-dose vaccination against Omicron remain unknown.

Methods

A total of 272 healthcare workers were initially evaluated for long-term vaccine safety and immunogenicity. We further established a vaccinee panel to evaluate the safety and immunogenicity against variants of concern (VOCs), including the Omicron variants, using a live virus microneutralization assay.

Findings

Two-dose vaccination induced robust anti-spike antibodies and neutralization titers (NTs) against the ancestral strain WK-521, whereas NTs against VOCs were significantly lower. Within 93–247 days of the second vaccine dose, NTs against Omicron were completely abolished in up to 80% of individuals in the vaccinee panel. Booster dose induced a robust increase in anti-spike antibodies and NTs against the WK-521, Delta, and Omicron variants. There were no significant differences in the neutralization ability of sera from boosted individuals among the Omicron subvariants BA.1, BA.1.1, and BA.2. Boosting increased the breadth of humoral immunity and cross-reactivity with Omicron without changes in cytokine signatures and adverse event rate.

Conclusions

The third vaccination dose is safe and increases neutralization against Omicron variants.

Funding

This study was supported by grants from AMED (grants JP21fk0108104 and JP21mk0102146).

The SARS-CoV-2 Omicron variant, later named BA.1, has emerged as a highly transmissible variant due to the 36 mutations in its spike protein, which is the target of neutralizing antibodies; it can therefore escape vaccine-induced immunity. The Omicron subvariant, BA.2, was recently identified and has rapidly become a major variant of concern in many countries, including Japan. This study found that anti-spike antibody levels and neutralization ability decreased gradually 6–9 months after the second vaccination. A third dose dramatically increased the response against multiple Omicron variants. These results show that a booster shot increases neutralization antibodies against SARS-CoV-2 variants.