NLRP3 inflammasome activation by Foot-and-mouth disease virus infection mainly induced by viral RNA and non-structural protein 2B.

Foot-and-mouth disease virus (FMDV) is a positive-strand RNA virus of the family Picornaviridae. Early studies show that some viruses of Picornaviridae, such as EMCV and EV71, induce NLRP3 inflammasome activation. Our current study demonstrates that FMDV induces the secretion of caspase-1 and interleukin 1 beta (IL-1ß), as well as activates the NLRP3 inflammasome in a dose- and time-dependent manner. Meanwhile, NLRP3 inflammasome can suppress FMDV replication during virus infection. Both FMDV RNA and viroporin 2B stimulate NLRP3 inflammasome activation. FMDV RNA triggers NLRP3 inflammasome through p-NF-κB/p65 pathway not dependent on RIG-I inflammasome. FMDV 2B activates NLRP3 inflammasome through elevation of intracellular ion, but not dependent on mitochondrial reactive oxygen species (ROS) and lysosomal cathepsin B. It further demonstrates that 2B viroporin activates NLRP3 inflammasome and induces IL-1ß in mice, which enhances the specific immune response against FMDV as an ideal self-adjuvant for FMD VLPs vaccine in guinea pigs. The results reveal a series of regulations between NLRP3 inflammasome complex and FMDV. Amino acids 140-145 of 2B is essential for forming an ion channel. By mutating the amino acid and changing the hydrophobic properties, the helical transmembrane region of the viroporin 2B is altered, so that the 2B is insufficient to trigger the activation of NLRP3 inflammasome. This study demonstrates the functions of FMDV RNA and 2B viroporin activate NLRP3 inflammasome and provides some useful information for the development of FMD vaccine self-adjuvant, which is also helpful for the establishment of effective prevention strategies by targeting NLRP3 inflammasome.

Characterization of humoral and cellular immune features of gamma-irradiated influenza vaccine.

The most widely used influenza vaccines are prepared by chemical inactivation. However, chemical, especially formalin, treatment-induced modifications of the antigenic structure of the virus are frequently associated with adverse effects including low efficacy of protection, unexpected immune responses, or exacerbation of disease. Gamma-irradiation was suggested as an alternative influenza virus inactivation method due to its great features of completely inactivating virus while not damaging the structures of protein antigens, and cross-protective ability against heterologous strains. However, immunological features of gamma radiation-inactivated influenza vaccine have not been fully understood. In this study, we aimed to investigate the humoral and cellular immune responses of gamma radiation-inactivated influenza vaccine. The gamma irradiation-inactivated influenza vaccine (RADVAXFluA) showed complete viral inactivation but retained normal viral structure with functional activities of viral protein antigens. Intranasal immunization of RADVAXFluA provided better protection against influenza virus infection than formalin-inactivated influenza virus (FIV) in mice. RADVAXFluA greatly enhanced the production of virus-specific serum IgG and alveolar mucosal IgA, which effectively neutralized HA (hemagglutinin) and NA (neuraminidase) activities, and blocked viral binding to the cells, respectively. Further analysis of IgG subclasses showed RADVAXFluA-immunized sera had higher levels of IgG1 and IgG2a than those of FIV-immunized sera. In addition, analysis of cellular immunity found RADVAXFluA induced strong dendritic cells (DC) activation resulting in higher DC-mediated activation of CD8+ T cells than FIV. The results support improved immunogenicity by RADVAXFluA.

Enhanced biofilm formation of Streptococcus gordonii with lipoprotein deficiency.

Streptococcus gordonii is a commensal Gram-positive bacterium that acts as an opportunistic pathogen that can cause apical periodontitis, endocarditis, and pneumonia. Biofilm formation of bacteria is important for the initiation and progression of such diseases. Although lipoproteins play key roles in physiological functions, the role of lipoproteins of S. gordonii in its biofilm formation has not been clearly understood. In this study, we investigated the role of lipoproteins of S. gordonii in the bacterial biofilm formation using its lipoprotein-deficient strain (Δlgt). The S. gordonii Δlgt exhibited increased biofilm formation on the human dentin slices or on the polystyrene surfaces compared to the wild-type strain, while its growth rate did not differ from that of the wild-type. In addition, the S. gordonii Δlgt strain exhibited the enhanced LuxS mRNA expression and AI-2 production, which is known to be a positive regulator of biofilm formation, compared to the wild-type. Concordantly, the augmented biofilm formation of S. gordonii Δlgt was attenuated by an AI-2 inhibitor, D-ribose. In addition, lipoproteins from purified S. gordonii inhibited the biofilm formation of S. gordonii wild-type and Δlgt. Taken together, these results suggest that lipoprotein-deficient S. gordonii form biofilms more effectively than the wild-type strain, which might be related to the AI-2 quorum-sensing system.