巨细胞病毒中性红斑定量试验与高滴度病毒的制备

在巨细胞病毒(CMV)的研究中常需对病毒定量。CMV需低滴度传代,否则会产生没有感染性的缺损病毒颗粒;CMV的抗原性受其感染量的影响;检测CMV中和抗体或纯化病毒都需具备病毒空斑定量基础。另外,制备高感染滴度的无细胞病毒(游离病毒)是对CMV进行分子生物学研究的前提。本文建立了CMV微量板法中性红斑定量技术并比较了几种制备无细胞CMV的方法。     

Human immunodeficiency virus-like, nonreplicating, gag-env particles assemble in a recombinant vaccinia virus expression system.

We report the assembly of human immunodeficiency virus (HIV)-like particles in African green monkey kidney cells coinfected with two recombinant vaccinia viruses, one carrying the HIV-1 gag and protease genes and the other the env gene. Biochemical analysis of particles sedimented from culture supernatants of doubly infected cells revealed that they were composed of gag proteins, primarily p24, as well as the env proteins gp120 and gp41. Thin-section immunoelectron microscopy showed that these particles were 100 to 120 nm in diameter, were characterized by the presence of cylindrical core structures, and displayed the mature gp120-gp41 complexes on their surfaces. Furthermore, thin-section immunoelectron microscopy analysis of infected cells showed that particle assembly and budding occurred at the plasma membrane. Nucleic acid hybridization suggested that the particles packaged only the gag mRNA but not the env mRNA. Therefore, the system we present is well suited for studies of HIV virion maturation. In addition, the HIV-like particles provide a novel and attractive approach for vaccine development.     

沙门氏菌Ⅱ的三个新血清型

Eight cultures isolated from intestinal contents of reptiles were belonged to 3 new serotypes of Salmonella. They were all ducitol fermented, malonate utilized, but not attack lactose and salicin, no growth in KCN broth, ONPG negative. Therefore, they would be included in Salmonella II. They were all attacked by Felix phage O-I. Three represented strains were selected for antigen analysis. Their antigenic formula were identified as follows: S3194 Salmonella II 6,7:1,v:e,n,z15 S3196 Salmonella II 6, 7:y: e, n, z(1)5 S3195 Salmonella II 6, 8: e, h: 1,2 Among them, S3196 was indole positive belonging to a rare biotype. In addition, there were two other cultures as well as the formula of S3194, and three other cultures as well as the formula of S3196 (one of indole positive, two of indole negative).     

Fragment A of diphtheria toxin causes pH-dependent lesions in model membranes

Fragment A of diphtheria toxin has been shown to insert into lipid bilayers at low pH (Montecucco, C., Schiavo, G., and Tomasi, M. (1985) Biochem. J. 231, 123-128; Zhao, J.-M., and London, E. (1988) J. Biol. Chem. 263, 15369-15377). In this report, evidence is provided which demonstrates that fragment A, like diphtheria toxin, can also cause the release of a fluorescent dye (calcein) from vesicles under acidic conditions and that this release parallels fragment A insertion into the membrane. Although the permeability changes are not as large as those obtained with whole toxin (Jiang, G.-S., Solow, R., and Hu, V. W. (1989) J. Biol. Chem. 264, 13424-13429), molecular sieving experiments indicate that the lesion induced by fragment A increases in size with decreasing pH and reaches an upper limit of 30 A at pH 4.0. In addition to size differences, the lesion induced by fragment A releases calcein in a graded manner, whereas diphtheria toxin causes an all-or-none release. One possible interpretation of this result is that the fragment A lesion is transient in comparison to that induced by whole toxin. Although the molecular bases for the observed differences are not understood, these data suggest that fragment A interaction with the lipid bilayer may play a significant role in mediating its own translocation across membranes and that fragment B may aid this process by initiating, enlarging, and stabilizing the lesion formed.     

Insulin suppresses hepatitis B surface antigen expression in human hepatoma cells

The human hepatoma Hep3B cells contain integrated hepatitis B viral genome and continually secret hepatitis B surface antigen (HBsAg). The production of HBsAg (but not alpha-fetoprotein) was suppressed by addition of low concentrations (0.1-1 nM) of insulin into serum-free medium. In addition, the suppression of HBsAg production by insulin was paralleled with the decrease in HBsAg mRNA abundance. Insulin also cause a rapid rate of disappearance of HBsAg mRNA (t 1/2, 2 h) in Hep3B cells. The Hep3B cells carry specific receptor with high affinity for insulin (Kd = 1.8 nM). The receptor showed an insulin-dependent protein tyrosine kinase activity. The half-maximal insulin concentration for the activation of the receptor kinase was about 5 nM. Only very high concentrations of insulin-like growth factor I and human proinsulin can compete for the insulin receptor binding and suppress HBsAg production, this suggests that insulin may act through its receptor binding to suppress HBsAg expression in human hepatoma Hep3B cells.