Different pH requirements for entry of the two picornaviruses,human rhinovirus 2 and murine encephalomyocarditis virus

The entry into cells of human rhinovirus 2 (HRV 2) and murine encephalomyocarditis (EMC) virus was studied by the use of light-sensitive virus grown in the presence of acridine orange (HRV 2) and neutral red (EMC). HeLa cells were protected against infection with HRV 2 by NH₄Cl, monensin, and other compounds known to increase the pH of intracellular vesicles. Preincubation of the cells with the same compounds reduced the ability of the cells to bind [³⁵S]methionine-labeled HRV 2, apparently due to inhibition of recycling of endocytosed receptors back to the cell surface. The cells were also protected against infection when HRV 2 was bound to cells on ice and the cells were then incubated at 37° with the different compounds. This indicates that low pH is also necessary for some event in the entry process taking place after the virus is bound to the cells. In contrast, compounds which increase the pH in acidic intracellular compartments did not protect mouse L-cells against infection with EMC-virus, and the entry of the virus was inhibited by low pH in the medium. This inhibition was partly overcome by the presence of the ionophore monensin, which elevates the pH in endosomes and lysosomes. Possibly, EMC virus enters the cytosol from vesicles with neutral or slightly alkaline pH.     

c-Myc is essential for vasculogenesis and angiogenesis during development and tumor progression

c-Myc promotes cell growth and transformation by ill-defined mechanisms. c-myc(-/-) mice die by embryonic day 10.5 (E10.5) with defects in growth and in cardiac and neural development. Here we report that the lethality of c-myc(-/-) embryos is also associated with profound defects in vasculogenesis and primitive erythropoiesis. Furthermore, c-myc(-/-) embryonic stem (ES) and yolk sac cells are compromised in their differentiative and growth potential. These defects are intrinsic to c-Myc, and are in part associated with a requirement for c-Myc for the expression of vascular endothelial growth factor (VEGF), as VEGF can partially rescue these defects. However, c-Myc is also required for the proper expression of other angiogenic factors in ES and yolk sac cells, including angiopoietin-2, and the angiogenic inhibitors thrombospondin-1 and angiopoietin-1. Finally, c-myc(-/-) ES cells are dramatically impaired in their ability to form tumors in immune-compromised mice, and the small tumors that sometimes develop are poorly vascularized. Therefore, c-Myc function is also necessary for the angiogenic switch that is indispensable for the progression and metastasis of tumors. These findings support the model wherein c-Myc promotes cell growth and transformation, as well as vascular and hematopoietic development, by functioning as a master regulator of angiogenic factors.     

Clade analysis and surface antigen polymorphism of hepatitis B virus American genotypes

Eight genotypes (A-H) of hepatitis B virus (HBV) have been described, HBV genotypes F and H being autochthonous to America. HBV genotype F has been classified in four clusters. The objective of this study was to gain insight into the molecular epidemiology of HBV American genotypes, as well as to analyze the genotype-related polymorphism in some functional domains of the surface proteins. The sequences of the S region of 106 isolates genotype F and H were analyzed, out of which 47 isolates genotype F circulated in different Venezuelan populations. Most of the Venezuelan isolates genotype F were grouped in cluster III (n = 39) and 7 in cluster II. One isolate obtained from a blood donor could not be classified in any clade and harbored amino acid substitutions characteristic of a vaccine escape mutant (G145R) and a stop codon in the surface antigen. Amino acid analysis of the PreS and S gene products showed unique genetic characteristics in genotype F and H sequences in some important domains involved in the early steps of infection. Out of 30 available sequences, two complete genome sequences of HBV genotype F from Venezuela were obtained. Phylogenetic analysis of these complete genomes confirmed the presence of four clusters inside genotype F, differing in more than 4% nucleotide divergence. Our extended analysis showed that genotype F clades Ia, III, and IV exhibit a restricted geographic distribution (Central America, the North and the South of South America, respectively) while clades Ib and II are found in all the Americas except in the Northern South America and North America respectively.     

Comparison of class and subclass distribution of antibodies to the hepatitis B core and B e antigens in chronic hepatitis B

The IgG subclasses IgM and IgA1 of antibodies to hepatitis B core antigen (anti-HBc) and hepatitis B e antigen (anti-HBe) were assayed in sera from 82 patients with chronic hepatitis B utilising class/subclass-specific enzyme immunoassays (EIA). The solid-phase was either recombinant hepatitis B core antigen (rHBcAg) or rHBcAg converted to HBeAg by addition of 0.1% SDS with remaining HBcAg antigenicity blocked with monoclonal anti-HBc. Anti-HBc IgG1 was detected in 81 sera at a geometrical mean titre (GMT) of 296,110 x divided by 2.9. Anti-HBc IgG2 was not detected in any of the sera, and anti-HBc IgG3 and IgG4 were detected in 50 and 37 sera, respectively. Anti-HBc IgM and IgA1 were both significantly correlated to the presence of HBV DNA. The predominant antibody to HBeAg was found to be IgG1, being detected in 45 sera with a GMT of 1,035 x divided by 3.3. Anti-HBe IgG2 was not detected in any serum, while anti-HBe IgG3 and IgG4 were found in 8 and 23 sera, respectively. Anti-HBe IgG1, IgG3, and IgG4 were mainly detected in sera positive for anti-HBe in RIA (Abbott). No patient was found positive for anti-HBe IgA1 or IgM. Thus, in contrast to HBcAg, HBeAg does not trigger a persistent IgM and IgA1 response in chronic hepatitis B. The levels of anti-HBe IgG1 and IgG3 were much lower than the levels of anti-HBc IgG1 and IgG3. The presence of anti-HBe IgG4 was significantly correlated to that of anti-HBc IgG4.(ABSTRACT TRUNCATED AT 250 WORDS)     

MR microscopy and high resolution small animal MRI: applications in neuroscience research

The application of magnetic resonance (MR) imaging in the study of human disease using small animals has steadily evolved over the past two decades and strongly established the fields of "small animal MR imaging" and "MR microscopy." An increasing number of neuroscience related investigations now implement MR microscopy in their experiments. Research areas of growth pertaining to MR microscopy studies are focused on (1). phenotyping of genetically engineered mice models of human neurological diseases and (2). rodent brain atlases. MR microscopy can be performed in vitro on tissue specimens, ex vivo on brain slice preparations and in vivo (typically on rodents). Like most new imaging technologies, MR microscopy is technologically demanding and requires broad expertise. Uniform guidelines or "standards" of a given MR microscopy experiment are non-existent. The main focus therefore of this review will be on biological applications of MR microscopy and the experimental requirements. We also take a critical look at the biological information that small animal (rodent) MR imaging has provided in neuroscience research.     

Distinct immunological signatures discriminate severe COVID-19 from non-SARS-CoV-2-driven critical pneumonia

1. Download : Download high-res image (233KB)
2. Download : Download full-size image

     

HLA Antigens in 16 Families with Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disease. HLA-A and -B typing was performed on peripheral blood lymphocytes and platelets. Sixteen Tunisian families were typed with 37 patients and 108 relatives. Genetic transmission of the disease and of the HLA system seemed to be independent in this study. Comparison of HLA gene frequencies between (unrelated) parents of patients and a control population showed no difference, proving that there is no clear association in populations between deleterious XP genes and a particular HLA gene. However, an excess of identical HLA among pairs of diseased siblings would suggest that the disease is polymorphic and a form of the XP could be linked to HLA.