Microbiology and Immunology最新文献

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.

We apologize for this error.

Porphyromonas gingivalis is a typical periodontal pathogen, and one of its key virulence factors is the powerful protease gingipains. Gingipains are secreted via the type IX secretion system (T9SS) and are associated with the assembly and insertion machinery (Aim) operon (PGN_0296 to PGN_0301), which encodes both T9SS components and non-T9SS proteins. In this study, we investigated PGN_0298, a gene of unknown function within this operon, to elucidate its role in P. gingivalis and to gain insights into its potential function through bioinformatics analyses. Our results demonstrated that PGN_0298 is essential for the viability of P. gingivalis, despite having limited direct association with T9SS. Sequence homology and structure predictions indicate that PGN_0298 encodes a putative isoprenyl transferase. The essentiality of PGN_0298 underscores its potential as a novel drug target for the treatment of periodontal disease.

Cover photograph: White-tailed deer ACE2 (marked as K31) in complex with prototype SARS-CoV-2 spike protein receptor-binding domain (RBD) (PDB ID:8HG0) and Omicron RBD (PDB ID:8IFZ). ACE2 is shown in yellow and RBD in green. WTD ACE2 (K31) with introduced K31N mutation to mimic sika deer ACE2 structure is marked as K31N. K31 and K31N are highlighted in red. The key amino acids in the SARS-CoV-2 RBD that are important for binding with K31 and K31N are marked with one-letter codes and colored. Sites where interaction with the K31N mutation creates weaker binding are highlighted in magenta, and those where binding increases - in blue. K31 and K31N van der Waals and hydrogen bond interaction rates with RBD predicted with molecular dynamics simulations for prototype and Omicron are shown. A positive value in ‘difference’ indicates decreased interaction with K31N mutation (red arrows) and negative – increased (green arrow). Microbiol Immunol: 69:533-543. Article link here

Seasonal influenza is prevalent every winter, and influenza vaccines are used to safeguard public health. As the influenza vaccines are produced in embryonated hen eggs using vaccine viruses recommended by the World Health Organization each year based on the epidemic situation, it is important, from the perspective of public health, to evaluate the reactivity of the vaccines against circulating viruses in humans. This study was designed to determine whether evaluating influenza vaccine efficacy using mouse sera could help predict efficacy in humans. The split hemagglutinin (HA) vaccines, produced using vaccine viruses for the 2023/2024 season, were inoculated into ddY and BALB/c mice, and their neutralizing reactivity to circulating influenza viruses was evaluated using their antisera. The titers of antibodies against these viruses in the antisera from humans immunized with the split HA vaccine were also measured. The vaccines induced the production of functional vaccine-specific antibodies dose-dependently. In the case of circulating viruses, the neutralizing antibodies in the sera of immunized individuals were able to react to most the test viruses, but they were less reactive to some viruses. The titers of neutralizing antibodies against these circulating strains in the antisera from humans immunized with the split HA vaccine for the 2023/2024 season were similar to those in the mouse antisera. Furthermore, intraperitoneal inoculation in ddY mice induced antibody production with higher neutralizing titers than subcutaneous inoculation in BALB/c mice. Taken together, the immunization protocol using naive mice could be a suitable method for predicting vaccine efficacy in humans.