To evaluate the reactivity of the recombinant proteins expressed in Escherichia coli strain BL21(DE3), a Western blot assay was performed by using a panel of 78 serum samples obtained, respectively, from convalescent-phase patients infected with severe acute respiratory syndrome-associated coronavirus (SARS-CoV) (30 samples) and from healthy donors (48 samples). As antigen for detection of SARS-CoV, the nucleocapsid protein (N) showed high sensitivity and strong reactivity with all samples from SARS-CoV patients and cross-reacted with all serum samples from healthy subjects, with either those obtained from China (10 samples) or those obtained from France (38 serum samples), giving then a significant rate of false positives. Specifically, our data indicated that the two subunits, S1 (residues 14 to 760) and S2 (residues 761 to 1190), resulted from the divided spike reacted with all samples from SARS-CoV patients and without any crossreactivity with any of the healthy serum samples. Consequently, these data revealed the nonspecific nature of N protein in serodiagnosis of SARS-CoV compared with the S1 and S2, where the specificity is of 100%. Moreover, the reported results indicated that the use of one single protein as a detection antigen of SARS-CoV infection may lead to false-positive diagnosis. These may be rectified by using more than one protein for the serodiagnosis of SARS-CoV.

Mixed viral and bacterial infections are widely described in community-acquired pneumonia; however, the clinical implications of co-infection on the associated immunopathology remain poorly studied. In this study, microRNA, mRNA and cytokine/chemokine secretion profiling were investigated for human monocyte-derived macrophages infected in-vitro with Influenza virus A/H1N1 and/or Streptococcus pneumoniae. We observed that the in-vitro co-infection synergistically increased interferon-γ-induced protein-10 (CXCL10, IP-10) expression compared to the singly-infected cells conditions. We demonstrated that endogenous miRNA-200a-3p, whose expression was synergistically induced following co-infection, indirectly regulates CXCL10 expression by targeting suppressor of cytokine signaling-6 (SOCS-6), a well-known regulator of the JAK-STAT signaling pathway. Additionally, in a subsequent clinical pilot study, immunomodulators levels were evaluated in samples from 74 children (≤5 years-old) hospitalized with viral and/or bacterial community-acquired pneumonia. Clinically, among the 74 cases of pneumonia, patients with identified mixed-detection had significantly higher (3.6-fold) serum IP-10 levels than those with a single detection (P = 0.03), and were significantly associated with severe pneumonia (P < 0.01). This study demonstrates that viral and bacterial co-infection modulates the JAK-STAT signaling pathway and leads to exacerbated IP-10 expression, which could play a major role in the pathogenesis of pneumonia.

Previous work on hepatitis C virus (HCV) led to the discovery of a new form of virus particle associating virus and lipoprotein elements. These hybrid particles (LVP for lipo-viro-particles) are enriched in triglycerides and contain at least apolipoprotein B (apoB), HCV RNA and core protein. These findings suggest that LVP synthesis could occur in liver and intestine, the two main organs specialized in the production of apoB-containing lipoprotein. To identify the site of LVP production, the genetic diversity and phylogenetic relationship of HCV quasispecies from purified LVP, whole serum and liver biopsies from chronically infected patients were studied. HCV quasispecies from LVP and liver differed significantly, suggesting that LVP were not predominantly synthesized in the liver but might also originate in the intestine. The authors therefore searched for the presence of HCV in the small intestine. Paraffin-embedded intestinal biopsies from 10 chronically HCV-infected patients and from 12 HCV RNA-negative controls (10 anti-HCV antibody-negative and two anti-HCV antibody-positive patients) were tested for HCV protein expression. HCV NS3 and NS5A proteins were stained in small intestine epithelial cells in four of the 10 chronically infected patients, and not in controls. Cells expressing HCV proteins were apoB-producing enterocytes but not mucus-secreting cells. These data indicate that the small intestine can be infected by HCV, and identify this organ as a potential reservoir and replication site. This further emphasizes the interaction between lipoprotein metabolism and HCV, and offers new insights into hepatitis C infection and pathophysiology. INTRODUCTIONHepatitis C virus (HCV) infects over 170 million people worldwide and is a major cause of chronic liver infection, often leading to chronic liver disease, cirrhosis and hepatocellular carcinoma. HCV possesses a single-stranded, positivesense RNA genome encoding a single polyprotein, and the virus has been classified in the family Flaviviridae with the flaviviruses and pestiviruses (Pringle, 1999). Although the flaviviruses infect many tissues in a large number of hosts from insects to primates, and replicate in numerous cell lines in vitro, HCV replication is extremely limited and occurs mainly in the human liver (Hoofnagle, 2002;Rice, 1996). Studies on the virus replication and biology have been hampered by the lack of an efficient and reliable cell culture system, and because chimpanzee is the only animal model. HCV may be envisioned as a flavivirus whose replication relies on specific cellular functions present in specific organs such as the liver. A recent report on replication of HCV subgenomic replicons, without production of virus particles, in non-hepatic epithelial human and mouse hepatoma cells indicates that the specific cellular factors required for translation and replication of HCV RNA are not restricted to hepatocytes or cells of human origin (Zhu et al., 2003). Therefore, the apparent tropism of HCV for hepatocytes is probably also determi...