Microbiology and Immunology最新文献

Orthobornaviruses express X and the phosphoprotein (P) from a bicistronic X/P mRNA, and these proteins regulate polymerase activity. In mammalian orthobornaviruses, the 5′ untranslated region (5′ UTR) of the X/P mRNA controls the translational balance between X and P and thereby promotes efficient replication. Avian bornaviruses (ABVs) belong to two clades, clade-2 and -3, that differ in the structure and length of the 5′ UTR of the X/P mRNA. However, the functional consequences of these differences remain unclear. Using reverse genetics, we generated chimeric viruses by reciprocally exchanging the 5′ UTR of the X/P mRNA among clade 2 parrot bornavirus 5 (PaBV-5) and aquatic bird bornavirus 1 (ABBV-1) and clade 3 PaBV-4. In PaBV-5, a long 5′ UTR with a stem–loop and an upstream ORF was required to maintain the X-to-P translational balance. On the other hand, replacing the 5′ UTR of the X/P mRNA from PaBV-5 with that from PaBV-4 reduced X expression and markedly impaired viral growth. However, PaBV-4 tolerated the 5′ UTR of the X/P mRNA from PaBV-5 without detectable effects on translation or replication, which suggests that translation of PaBV-4 X/P mRNA does not depend on the origin of the 5′ UTR. Furthermore, ABBV-1 replicated efficiently with the 5′ UTR of the X/P mRNA from PaBV-5 but was strongly attenuated with that from PaBV-4. Taken together, these results demonstrate a clade-dependent requirement for the 5′ UTR for translation of the X/P mRNA and provide novel insights into the evolution of translational control in orthobornaviruses.

Bordetella has a type III secretion system that secretes virulence proteins crucial to the establishment of infection. The genes encoding components of the Bordetella type III secretion system are located in the bsc region on the chromosome. This region includes the bcrH1 and bcrH2 genes, which respectively encode the proteins BcrH1 and BcrH2. In this study, we analyzed the functions of BcrH1 and BcrH2 in the Bordetella type III secretion system. First, we created a BcrH1-deficient strain and a BcrH2-deficient strain. We analyzed the amounts of the type III secreted proteins BopB and BopD, which make a complex that forms pores in the host membrane, in bacterial cells of each protein-deficient strain. The results showed that the BopB and BopD signals were weakened in the whole cell fraction of the BcrH1-deficient strain and the BcrH2-deficient strain, respectively. The hemolytic activity and cell toxicity of each BcrH protein-deficient strain were significantly lower than those of the wild-type strain. When anti-BcrH1 and anti-BcrH2 antibodies were used for the immunoprecipitation assay, the BopB and BopD signals were detected in the precipitated fractions, respectively. These results strongly suggest that BcrH1 and BcrH2 are specific chaperones for maintaining the stability of BopB and BopD, respectively.

Cover photograph: METTL3 Regulated Skeletal Muscle Atrophy in CKD-Associated Sarcopenia via the TLR4/NF-κB Signaling Pathway. HE staining of kidney and gastrocnemius muscle tissues to assess histopathological changes. Microbiol Immunol: 69:608-618. Article link here

Influenza A and B viruses cause annual epidemics and continue to pose global public health concerns. The most effective approach to preventing or mitigating the severity of influenza is vaccination. Inactivated split influenza HA vaccines are commonly used worldwide due to their strong safety profile and broad range of target groups; however, their efficacy is suboptimal, especially in the elderly. Adjuvants are used to enhance the effectiveness of some influenza vaccines, but few adjuvants have been approved for human vaccines. Previously, we identified hydroxypropyl cellulose as a promising adjuvant for the split influenza HA vaccine for the 2015–2016 and 2016–2017 influenza seasons. Here, we evaluated whether hydroxypropyl cellulose could enhance the efficacy of the quadrivalent split HA vaccine for the 2023–2024 influenza season, which contains the HA proteins of A/Victoria/4897/2022 (H1N1)pdm09 and three other strains. Using a mouse model, we performed immunogenicity studies and assessed protective efficacy against challenges with homologous and heterologous H1N1pdm09 virus strains. We found that hydroxypropyl cellulose in combination with the HA vaccine generated higher virus-specific IgG antibody titers compared to the vaccine alone. The adjuvanted vaccine provided complete protection against homologous challenge and enhanced viral clearance from respiratory organs. Notably, the adjuvanted vaccine demonstrated cross-protective efficacy against heterologous H1N1pdm09 virus challenge, improving survival rates compared to vaccine alone. Our results demonstrate that hydroxypropyl cellulose has potential as an adjuvant for current seasonal influenza vaccines.

The periodontal pathogen Porphyromonas gingivalis secretes gingipains, highly hydrolytic proteases, to the cell surface or external environment via a type IX secretion system (T9SS). PorE is one of the T9SS component proteins essential for gingipain secretion. It consists of four domains: TPR, WD40, CRD, and OmpA_C-like. In this study, we investigated the contribution and function of these PorE domains to gingipain secretion by generating PorE mutants with domain deletions and residue substitutions. We found that (i) the OmpA_C-like domain is essential for gingipain secretion, (ii) the peptidoglycan binding sites (Asp⁵⁷⁶ and Asn⁵⁸⁴) in the OmpA_C-like domain are a necessity for gingipain secretion, (iii) the WD40 domain is likely involved in interaction with PorP, and (iv) the CRD domain is not essential for gingipain secretion. The function of the TPR domain could not be assessed because no PorE protein of the predicted molecular mass was detected in the TPR domain-deleted PorE mutant. We also demonstrated that some T9SS cargo proteins, such as PorA and Hbp35, do not require the PorE-PorP complex for secretion, suggesting that the PorE–PorP complex may occupy a unique position within the T9SS that is distinct from other components.

Nipah virus (NiV) is a highly pathogenic zoonotic virus transmitted from bats to humans through pigs as a crucial intermediate host. NiV outbreaks pose significant public health and economic threats, especially for pig farmers. Although the World Organization for Animal Health recommends African green monkey-derived Vero cells for NiV isolation, pig-derived cell lines could represent an optimal platform for propagating pig-origin NiV, as signs and symptoms of NiV infection differ among different hosts. In this study, we generated and evaluated pig-derived PK-15 cells stably expressing pig-derived ephrin-B2 (PK-15/Ephrin-B2 cells), the primary receptor for NiV. NiV pseudovirus infectivity was increased by > 1000-fold in PK-15/Ephrin-B2 cells compared with that in wild-type PK-15 cells, whereas virus susceptibility was higher in PK-15/Ephrin-B2 cells than in Vero cells (> 30-fold). Furthermore, Stat2-knockout PK-15/Ephrin-B2 cells exhibited stable viral infectivity in the presence of type I interferon, making it particularly suitable for clinical sample testing. Moreover, PK-15/Ephrin-B2 cells proved useful for neutralization tests using anti-NiV hyperimmune ascitic fluid. Therefore, PK-15 cells expressing pig ephrin-B2 could represent an efficient tool for virus isolation, vaccine development, and virological studies of NiV and related henipaviruses.

Yokota, H., Makizaki, Y., Tanaka, Y. and Ohno, H., “Bifidobacterium bifidum G9-1 Survives in the Intestinal Environment and Influences the Gut Microbiota Despite the Presence of Antimicrobials,” Microbiology and Immunology 69 (2025): 447–456, https://doi.org/10.1111/1348-0421.13230.

In the originally published version of this article, the Y-axis unit labels in Figures 1-6 through 7 were incorrectly written as “log₁₀ CFU/mL” or “log₁₀ CFU/g”. This was a typographical error. The correct units should be “CFU/mL” or “CFU/g”, which stand for colony-forming units per milliliter and colony-forming units per gram, respectively, and accurately reflect the microbiological quantification used in the study. The incorrect units may have caused confusion regarding the interpretation of microbial load. All affected figures have been revised to display the correct units. No changes have been made to the main text of the article.

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