The NLRP3 Inflammasome and IL-1β Accelerate Immunologically Mediated Pathology in Experimental Viral Fulminant Hepatitis

Viral fulminant hepatitis (FH) is a severe disease with high mortality resulting from excessive inflammation in the infected liver. Clinical interventions have been inefficient due to the lack of knowledge for inflammatory pathogenesis in the virus-infected liver. We show that wild-type mice infected with murine hepatitis virus strain-3 (MHV-3), a model for viral FH, manifest with severe disease and high mortality in association with a significant elevation in IL-1β expression in the serum and liver. Whereas, the viral infection in IL-1β receptor-I deficient (IL-1R1^-/-) or IL-1R antagonist (IL-1Ra) treated mice, show reductions in virus replication, disease progress and mortality. IL-1R1 deficiency appears to debilitate the virus-induced fibrinogen-like protein-2 (FGL2) production in macrophages and CD45⁺Gr-1^high neutrophil infiltration in the liver. The quick release of reactive oxygen species (ROS) by the infected macrophages suggests a plausible viral initiation of NLRP3 inflammasome activation. Further experiments show that mice deficient of p47^phox, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit that controls acute ROS production, present with reductions in NLRP3 inflammasome activation and subsequent IL-1β secretion during viral infection, which appears to be responsible for acquiring resilience to viral FH. Moreover, viral infected animals in deficiencies of NLRP3 and Caspase-1, two essential components of the inflammasome complex, also have reduced IL-1β induction along with ameliorated hepatitis. Our results demonstrate that the ROS/NLRP3/IL-1β axis institutes an essential signaling pathway, which is over activated and directly causes the severe liver disease during viral infection, which sheds light on development of efficient treatments for human viral FH and other severe inflammatory diseases.     

International Conference on Viral Hepatitis:Past Accomplishments and Unfulfilled Quests

15-17 April 2008, Xiamen, Fujian, China, http://nidvd.xmu.edu.cn/icvh2008.asp Abstract: The International Conference on Viral Hepatitis: Past Accomplishments and Unfulfilled Quests (ICVH2008) will be held from 15 to 17 April 2008 in Xiamen, China. This co…     

A Function Essential to Viral Entry Underlies the Hepatitis B Virus “a” Determinant

The hepatitis B virus (HBV) particles bear a receptor-binding site located in the pre-S1 domain of the large HBV envelope protein. Using the hepatitis delta virus (HDV) as a surrogate of HBV, a second infectivity determinant was recently identified in the envelope proteins antigenic loop (AGL), and its activity was shown to depend upon cysteine residues that are essential for the structure of the HBV immunodominant “a” determinant. Here, an alanine-scanning mutagenesis approach was used to precisely map the AGL infectivity determinant to a set of conserved residues, which are predicted to cluster together with cysteines in the AGL disulfide bridges network. Several substitutions suppressed both infectivity and the “a” determinant, whereas others were infectivity deficient with only a partial impact on antigenicity. Interestingly, G145R, a substitution often arising under immune pressure selection and detrimental to the “a” determinant, had no effect on infectivity. Altogether, these findings indicate that the AGL infectivity determinant is closely related to, yet separable from, the “a” determinant. Finally, a selection of HDV entry-deficient mutations were introduced at the surface of HBV virions and shown to also abrogate infection in the HBV model. Therefore, a function can at last be assigned to the orphan “a” determinant, the first-discovered marker of HBV infection. The characterization of the AGL functions at viral entry may lead to novel approaches in the development of antivirals against HBV.Hepatitis B virus (HBV) causes acute and chronic infections in humans; such infections are often associated with severe liver diseases, including cirrhosis and hepatocellular carcinoma (10). To date, it is estimated that approximately 350 millions individuals worldwide suffer from chronic infection despite the availability of an effective vaccine for more than 25 years. Remarkably, the development of a vaccine soon after the HBV discovery was, at least in part, the consequence of a very peculiar feature that is unique to members of the Hepadnaviridae family: viral envelope proteins are produced in quantities far exceeding the amounts required for assembly of HBV virions (6) and, owing to their capacity for autoassembly, the vast majority are secreted as subviral particles. Besides the practical consequences in the original vaccine development, in nature, the phenomenon of HBV envelope protein overexpression has provided a helper function to the hepatitis delta virus (HDV) (29). The HBV envelope proteins assist in packaging the HDV ribonucleoprotein (RNP) in case of HBV-HDV coinfection, thereby ensuring spreading of the satellite HDV. As a result, the coats of HBV and HDV particles are similar, consisting of cell-derived lipids and the HBV envelope proteins—large, middle, and small—bearing the HBV surface antigen (HBsAg) and referred to as L-HBsAg, M-HBsAg, and S-HBsAg, respectively (4, 14).The HBsAg includes an immunodominant determinant common to all HBV strains, referred to as “a,” and several mutually exclusive subtype-specific determinants referred to as “d”/“y” and “w”/“r” (21). The “a” determinant is defined by a specific conformation of the antigenic loop (AGL) polypeptide present at the surface of subviral, HBV, or HDV particles. The AGL itself resides between the transmembrane domain II (residues 80 to 100) and the hydrophobic carboxyl terminus (residues 165 to 226) of the envelope proteins S domain (see Fig. ​Fig.1).1). It is the “a” determinant that elicits the most effective neutralizing antibody response upon vaccination or infection (32). Surprisingly, a function in the HBV life cycle had never been assigned to the “a” determinant, the first identified HBV marker, until the recent demonstration of its involvement in HDV entry (2, 15). More precisely, it was shown that the AGL cysteine residues were critical for both the structure of the “a” determinant and HDV infectivity (2).Open in a separate windowFIG. 1.Schematic representation of the HBV envelope protein AGL. (A) The topology of the L-, M-, and S-HBsAg proteins (L, M, and S, respectively) is represented. The determinants of viral entry, pre-S1 and AGL, are indicated in red. The M-HBsAg protein, represented in gray, is dispensable for infectivity. Open boxes represent transmembrane regions in the S domain. (B) Alignment of the AGL amino acids sequences (positions 101 to 172 in the S domain) of HBV (genotype D, ayw3 phenotype), WMHBV, and WHV. The GenBank sequence numbers of the isolates are as follows: {"type":"entrez-nucleotide","attrs":{"text":"J02203","term_id":"329640","term_text":"J02203"}}J02203 (HBV), {"type":"entrez-nucleotide","attrs":{"text":"AY226578","term_id":"29501369","term_text":"AY226578"}}AY226578 (WMHBV), and {"type":"entrez-nucleotide","attrs":{"text":"NC_004107","term_id":"22256030","term_text":"NC_004107"}}NC_004107 (WHV). HBV amino acid residues important for infectivity (the present study) are indicated in blue. A hyphen denotes amino acid identity with the HBV sequence.It is now well established that both HBV and HDV entry rely on the pre-S1 domain of L-HBsAg as the primary infectivity determinant that is likely to promote attachment to a specific receptor at the surface of human hepatocytes (11). The AGL determinant could thus fulfill complementary functions for attachment, uptake, or particle disassembly after entry (2, 15).In the present study, the AGL infectivity determinant was mapped and confirmed to be closely related to the “a” determinant. Moreover, its essential function at viral entry was demonstrated in the HBV model.     

Both Functional LTβ Receptor and TNF Receptor 2 Are Required for the Development of Experimental Cerebral Malaria

Background

TNF-related lymphotoxin α (LTα) is essential for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The pathway involved has been attributed to TNFR2. Here we show a second arm of LTα-signaling essential for ECM development through LTβ-R, receptor of LTα1β2 heterotrimer.

Methodology/Principal Findings

LTβR deficient mice did not develop the neurological signs seen in PbA induced ECM but died at three weeks with high parasitaemia and severe anemia like LTαβ deficient mice. Resistance of LTαβ or LTβR deficient mice correlated with unaltered cerebral microcirculation and absence of ischemia, as documented by magnetic resonance imaging and angiography, associated with lack of microvascular obstruction, while wild-type mice developed distinct microvascular pathology. Recruitment and activation of perforin⁺ CD8⁺ T cells, and their ICAM-1 expression were clearly attenuated in the brain of resistant mice. An essential contribution of LIGHT, another LTβR ligand, could be excluded, as LIGHT deficient mice rapidly succumbed to ECM.

Conclusions/Significance

LTβR expressed on radioresistant resident stromal, probably endothelial cells, rather than hematopoietic cells, are essential for the development of ECM, as assessed by hematopoietic reconstitution experiment. Therefore, the data suggest that both functional LTβR and TNFR2 signaling are required and non-redundant for the development of microvascular pathology resulting in fatal ECM.     

L—缬氨酸

<正> 缬氨酸是人和动物营养所必需的氨基酸之一,它是脂肪族的中性氨基酸。1856年 Gorup-Besanty 从胰脏的提取液中首先发现。但直到1901年才被 E.Fischer 从蛋白质水解物分离成功。并证明它是蛋白质中的组成成份。同时,缬氨酸还是多种抗菌素如青霉素,短杆菌肽,     

L—酪氨酸

<正> 酪氨酸是芳香族含酚基的氨基酸,它在1847年首先被李比格(Libig)发现和分离出来。最早来沅于干酪素,因而取称为酪氨酸。De、La、Rue.W.第一个提出它的分析正确数据,指出其实验式为 C_8H_(11)NO_3,②1947-1957年期间及有博普(Bopp)等人。进一步多种蛋套质酸水解物中分出酪氨酸来。酪氨酸以蚕丝、蚕蛹、猪毛等含量较为丰富。除了为蛋白质组成存在外,尚有以溴代酪氨酸或碘代酪氨酸及 L—多巴等,酪氨酸的衍生物形存在于自然界。此外,还有作为新陈代谢调节剂的动物激素(催产素、释放素等)及某些菌素(放线菌素等)的组成而存在。酪氨酸是一种重要的生化试剂,也是合成二碘酪氨酸、L—多巴及含酪氨酸的多肽素,抗菌素等药物的原料。其用途正逐步扩大,需要量也日益增加。最近,我们用它进行小猪生长影响的试验。发现它能起促进小猪生长和节约蛋白质饲料的作用。③添加千分之一至千分之二的酪氨酸,就能比对照增27-65%。     

L—缬氨酸

缬氨酸是人和动物营养所必需的氨基酸之一,它是脂肪族的中性氨基酸。1856年 Gorup-Besanty 从胰脏的提取液中首先发现。但直到1901年才被 E.Fischer 从蛋白质水解物分离成功。并证明它是蛋白质中的组成成份。同时,缬氨酸还是多种抗菌素如青霉素,短杆菌肽,