BackgroundMonogenic autoinflammatory disorders are characterized by dysregulation of the innate immune system, for example by gain-of-function mutations in inflammasome-forming proteins, such as NOD-like receptor family CARD-containing 4 protein (NLRC4).ObjectiveHere we investigate the mechanism by which a novel mutation in the leucine-rich repeat (LRR) domain of NLRC4 (c.G1965C, p.W655C) contributes to autoinflammatory disease. Methods: We studied 2 unrelated patients with early-onset macrophage activation syndrome harboring the same de novo mutation in NLRC4. In vitro inflammasome complex formation was quantified by using flow cytometric analysis of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 techniques and lentiviral transduction were used to generate THP-1 cells with either wild-type or mutant NLRC4 cDNA. Cell death and release of IL-1β/IL-18 were quantified by using flow cytometry and ELISA, respectively.ResultsThe p.W655C NLRC4 mutation caused increased ASC speck formation, caspase-1–dependent cell death, and IL-1β/IL-18 production. ASC contributed to p.W655C NLRC4–mediated cytokine release but not cell death. Mutation of p.W655 activated the NLRC4 inflammasome complex by engaging with 2 interfaces on the opposing LRR domain of the oligomer. One key set of residues (p.D1010, p.D1011, p.L1012, and p.I1015) participated in LRR-LRR oligomerization when triggered by mutant NLRC4 or type 3 secretion system effector (PrgI) stimulation of the NLRC4 inflammasome complex.ConclusionThis is the first report of a mutation in the LRR domain of NLRC4 causing autoinflammatory disease. c.G1965C/p.W655C NLRC4 increased inflammasome activation in vitro. Data generated from various NLRC4 mutations provides evidence that the LRR-LRR interface has an important and previously unrecognized role in oligomerization of the NLRC4 inflammasome complex.

Hepatitis B virus (HBV) infection and its sequelae remain a major health problem for Taiwan. The national hepatitis B (HB) vaccination programme was first launched in 1984 to combat the spread of this infection. This study examined the status of HBV infection amongst students at a Taiwanese university in 2005, 18 years after the implementation of a nation-wide mass HB vaccination programme. In 2005, 5875 new university entrants, who were born during the period 1 July 1976 to 30 June 1988, were subdivided into one of 12 one-year-interval birth-year cohorts. Each student was individually tested for serum hepatitis B surface antigen (HBsAg), Antibody to hepatitis B surface antigen (anti-HBs) and antibody to hepatitis B core antigen (anti-HBc) status. We observed a declining trend of past exposure to HB infection from 48.7% (1976 birth-year cohort) to 5.2% (1987 birth-year cohort). The prevalence of chronic HB infection also declined from 14.5% (1976 birth-year cohort) to 1.9% (1987 birth-year cohort). The prevalence of persistent HB immunity through (earlier) active vaccination declined from 72% (1984 birth-year cohort) to 41.6% (1987 birth-year cohort). The prevalence of HB infection-naïve individuals increased from 18.2% (1984 birth-year cohort) to 53.1% (1987 birth-year cohort). This study demonstrates that as the implementation of the mass HB vaccination programme in 1984, the incidence of HB infection in Taiwan has declined, although a 'waning-off' effect of serum anti-HBs to low or undetectable levels, which may not provide protection, amongst this student population has arisen, 18 years following the implementation of the nation-wide HB vaccination programme. Such a situation may mean that these individuals may not be effectively protected against future HB infection. A booster dose of HB vaccine, given 18 years following HB vaccination, perhaps even earlier, should be considered.

Maitake (Grifola frondosa) is a popular mushroom in Asia for its tasty flavor and immune-stimulating property. The aim of the study is to investigate the innate immunity augmentation effects of different extracts of mycelia and culture filtrate from G. frondosa in submerged cultures. The hot water extract of mycelia showed the strongest cytokine induction effect as a function of its concentration in human whole blood culture. The most potent fractions of hot water extract, Fr. I and II, were mainly composed of polysaccharides with molecular masses of 43-140 and 13-38 kDa, respectively. These fractions (0.025 mg/mL) showed marked activity in enhancing phagocytosis of human polymorphonuclear neutrophils (PMN). In parallel, the expression of CD11b, an early marker of PMN activation, was also up-regulated dose dependently. This result suggested that complement receptor 3 was primed by these fractions. In addition to activation of phagocytes, these bioactive fractions also increased human peripheral blood natural killer cell cytotoxicity. These results imply that the relatively low molecular mass polysaccharides isolated from mycelia of G. frondosa can enhance innate immunity in vitro and therefore may serve as biological response modifiers.

In this study, we have identified 876 polymorphism sites in 145 complete or partial genomes of SARS-CoV available in the NCBI GenBank. One hundred and seventyfour of these sites existed in two or more SARS-CoV genome sequences. According to the sequence polymorphism, all SARS-CoVs can be divided into three groups: (I) group 1, animal-origin viruses (such as SARS-CoV SZ1, SZ3, SZ13 and SZ16); (II) group 2, all viruses with clinical origin during first epidemic; and (III) group 3, SARS-CoV GD03T0013. According to 10 special loci, group 2 again can be divided into genotypes C and T, which can be further divided into subgenotypes C1-C4 and T1-T4. Positive Darwinian selections were identified between any pair of these three groups. Genotype C gives neutral selection. Genotype T, however, shows negative selection. By comparing the death rates of SARS patients in the different regions, it was found that the death rate caused by the viruses of the genotype C was lower than that of the genotype T. SARS-CoVs might originate from an unknown ancestor.

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