Seed viruses containing novel avian HA and NA antigens for prevention against potential influenza pandemic.

An influenza pandemic could arise unexpectedly with rapid spread across the world. The efficiency of production of a vaccine and the ability to administer it widely will be among the most important factors in the ability to protect public health. The current process for producing inactivated or live attenuated influenza vaccines requires six to nine months. That reduces considerably the likelihood that the vaccine will be available during the first wave of the pandemic. Therefore, a key element of preparedness is to optimize the production process and to reduce the vaccine development time. During the 1997 H5N1 outbreak in Hong Kong, seed viruses were prepared for production of inactivated and live-attenuated vaccines. We used the cold-adapted A/Ann Arbor/6/60 as the donor virus to generate live attenuated vaccines containing genetically modified HA and NA genes from H5N1 influenza viruses. These reassortants were shown to be safe and protective in animal models. This study indicates that production of live attenuated avian influenza vaccines is feasible and that development of a library of reassortants containing different subtype HA and NA genes may reduce the vaccine preparation time for future influenza pandemics.

Antibody raised against soluble CD4-rgp120 complex recognizes the CD4 moiety and blocks membrane fusion without inhibiting CD4-gp120 binding.

We studied the humoral response of mice immunized with soluble CD4-rgp120 complex, testing polyclonal and monoclonal antibodies (mAbs) with the aim of identifying molecular changes that take place after the first interaction between human immunodeficiency virus and the cell surface. The antisera had a paradoxically high syncytia-blocking titer associated with anti-CD4 specificity, while their capacity to inhibit CD4-gp120 binding was relatively modest. One of the mAbs produced from these responders blocks syncytia formation but does not inhibit CD4 interaction with gp120. Apparently, this mAb interacts with the CD4 moiety of CD4-gp120 complex and prevents a post-binding event necessary for membrane fusion and viral infection.

The autocrine production of transforming growth factor-beta 1 during lymphocyte activation. A study with a monoclonal antibody-based ELISA.

We describe the production and characterization of three mAb to transforming growth factor-beta (TGF-beta) and the use of two of them for the development of a TGF-beta 1-specific ELISA and for the study of the regulation of immune function in vitro. All three mAb bound recombinant human TGF-beta 1 (rHuTGF-beta 1) with high affinity and recognized the dimer form of this molecule in immunoblots. mAb 2G7 immunoprecipitated rHuTGF-beta 1, TGF-beta 2, and rHuTGF-beta 3 and neutralized the growth inhibitory activity of all three molecules in vitro on mink lung epithelial-like cells, Mv1Lu, indicating a shared neutralization epitope. mAb 4A11 neutralized and immunoprecipitated only rHuTGF-beta 1, and mAb 12H5 immunoprecipitated rHuTGF-beta 1 but had no effect on the bioactivity of either rHuTGF-beta 1, TGF-beta 2, or rHuTGF-beta 3. These results suggest that a second neutralization epitope may be unique to TGF-beta 1. The ELISA was developed with mAb 4A11 and 12H5, with a range of 0.63 to 40 ng/ml, i.e., a sensitivity of 0.63 ng/ml or 63 pg/sample. The assay is accurate, precise, and specific for the active but not the inactive or latent TGF-beta 1 complex and fails to react with TGF-beta 2, rHuTGF-beta 3, inhibin A, and activin A. Supernatants obtained from serum-free cultures of human PBMC from multiple donors contained significant quantities of TGF-beta 1 (3 to 15 ng/ml), which was detected in the ELISA only after pH 2 treatment to convert latent TGF-beta to the active form. Treatment of the PBMC with either recombinant human IL-2 (rHuIL-2) or PHA-P/PMA enhanced the production of latent TGF-beta 1. mAb 4A11 and 2G7, but not mAb 12H5 enhanced both the proliferative response of PBMC to rHuIL-2/rHuTNF-alpha and PHA-P and the development of the rHuIL-2/rHuTNF-alpha treated PBMC into LAK cells with cytotoxic activity against COLO target cells. These findings suggest that although PBMC secrete latent TGF-beta 1, mechanisms that convert the latent TGF-beta complex into an active form exist in vitro and that the endogenously produced TGF-beta can regulate immune functions in an autocrine fashion.

Polyionic compounds selectively alter availability of CD4 receptors for HIV coat protein rgp120.

We studied the ability of several polyionic compounds, previously shown to have activity in vitro against human immunodeficiency virus (anti-HIV) to block binding of anti-CD4 and recombinant HIV gp120 to the CD4 receptor on human lymphocytes. We found that Evans blue and aurin tricarboxylic acid could completely inhibit binding of anti-CD4 (Leu3a) and rgp120 and have selectivity for the CD4 receptor. A number of other compounds, including dextran sulfate and heparin had no effect on binding of rgp120 and were shown to be nonspecific for inhibition of binding of monoclonal antibodies to different T-cell receptors. Studies using a number of membrane-active drugs showed that changes in membrane potential or ion fluxes were not involved in the inhibition of binding of rgp120 by Evans blue or aurin tricarboxylic acid.

Preparation and characterization of conjugates of recombinant CD4 and deglycosylated ricin A chain using different cross-linkers.

In a previous study, we have demonstrated that conjugates containing soluble, recombinant human CD4 (rCD4) and the deglycosylated form of ricin A chain (dgA) (rCD4-dgA) effectively kill a human T cell line infected with the human immunodeficiency virus (HIV) in vitro. In contrast, such conjugates are 100-1000-fold less toxic to uninfected cells. In order to use a rCD4-dgA conjugate effectively in vivo, it was important to demonstrate that (1) it binds to and kills HIV-infected, but not uninfected, human cells, (2) it is stable in the circulation, and (3) it has an optimal therapeutic index (toxicity to animals versus toxicity to target cells). A major factor affecting the efficacy of such conjugates in vitro and in vivo is the nature of the cross-linker between the ligand (rCD4) and the toxin (dgA). In this report, we have prepared rCD4-dgA conjugates using three different cross-linkers. Different methods of purification have been compared by determining the optimal yield, purity, and retention of biological activity (i.e., binding to gp120 and dgA chain activity). The structure of these conjugates as well as their cytotoxicity to target cells in vitro has been analyzed. Finally, we have compared their pharmacokinetics, tissue localization, and toxicity in mice.

HIV-infected cells are killed by rCD4-ricin A chain.

The gp120 envelope glycoprotein of the human immunodeficiency virus (HIV), which is expressed on the surface of many HIV-infected cells, binds to the cell surface molecule CD4. Soluble derivatives of recombinant CD4 (rCD4) that bind gp120 with high affinity are attractive vehicles for targeting a cytotoxic reagent to HIV-infected cells. Soluble rCD4 was conjugated to the active subunit of the toxin ricin. This conjugate killed HIV-infected H9 cells but was 1/1000 as toxic to uninfected H9 cells (which do not express gp120) and was not toxic to Daudi cells (which express major histocompatibility class II antigens, the putative natural ligand for cell surface CD4). Specific killing of infected cells can be blocked by rgp120, rCD4, or a monoclonal antibody to the gp120 binding site on CD4.

Delineation of a region of the human immunodeficiency virus type 1 gp120 glycoprotein critical for interaction with the CD4 receptor.

The primary event in the infection of cells by HIV is the interaction between the viral envelope glycoprotein, gp120, and its cellular receptor, CD4. A recombinant form of gp120 was found to bind to a recombinant CD4 antigen with high affinity. Two gp120-specific murine monoclonal antibodies were able to block the interaction between gp120 and CD4. The gp120 epitope of one of these antibodies was isolated by immunoaffinity chromatography of acid-cleaved gp120 and shown to be contained within amino acids 397-439. Using in vitro mutagenesis, we have found that deletion of 12 amino acids from this region of gp120 leads to a complete loss of binding. In addition, a single amino acid substitution in this region results in significantly decreased binding, suggesting that sequences within this region are directly involved in the binding of gp120 to the CD4 receptor.

Intracellular assembly and packaging of hepatitis B surface antigen particles occur in the endoplasmic reticulum.

Hepatitis B surface antigen (HBsAg) particles are secreted by Chinese hamster ovary cells that are stably transfected with the S gene of hepatitis B virus. The assembly of HBsAg into cylindrical and spherical particles occurred intracellularly within the endoplasmic reticulum. HBsAg particles accumulated within large dilated areas of the endoplasmic reticulum and remained within these structures for most of the time prior to secretion from the cells. Once the particles were formed, the HBsAg polypeptides did not appear to become associated with subsequent intracellular organelle membranes or the plasma membrane. HBsAg within the dilated structures did not bind wheat germ agglutinin, indicating that its oligosaccharide chains had not yet been processed to the complex form (containing terminal sialic acid-N-acetylglucosamine residues). The oligosaccharide chains of HBsAg are processed to the complex form and can be detected on the HBsAg after secretion, but this event was not detected within cells. In addition, HBsAg was not observed on the cell surface by indirect immunofluorescence or immunoprecipitation, although immunoelectron microscopy revealed some staining at or near the cell surface. These results suggested that HBsAg was either secreted from cells without being incorporated into the plasma membrane, or that the levels of HBsAg in the plasma membrane were below the limits of detection.

Radioimmunoassay for detection of VP1 specific neutralizing antibodies of foot and mouth disease virus.

A solid-phase radioimmunoassay was developed for the detection of antibodies against a specific region of the VP1 protein of the A24 and 01 serotypes of foot and mouth disease virus. The antibody titers from the radioimmunoassay showed a positive correlation with neutralizing antibody titers determined by a mouse protection assay. The specificity of the assay resides in the peptide used as antigen. The assay is rapid, reproducible and does not require the use of whole virions.

Use of recombinant mammalian cell lines for vaccine production.

Antiviral vaccines classically were composed of attenuated or inactivated whole virions produced by infection of eukaryotic cells. With the advent of recombinant DNA (rDNA) technology, the strategy for vaccine production has changed dramatically. The gene(s) encoding a specific protein(s) containing the virus neutralizing site(s) can be isolated and transfected into bacteria, yeast or mammalian cells in culture. These transfected or recombinant organisms or cells can be exploited to produce large quantities of the specific protein which subsequently can be developed in a highly purified form for use as a subunit vaccine. The issue which we would like to discuss is the selection of the host used for the expression of recombinant subunit vaccines.

Intracellular transport and secretion of hepatitis B surface antigen in mammalian cells.

The oligosaccharide processing and secretion of hepatitis B surface antigen (HBsAg) was studied in Chinese hamster ovary cells stably transfected with the gene coding HBsAg. HBsAg was secreted from cells with a relatively long half time (ca. 5 h). This appeared to be a characteristic of HBsAg itself, since HBsAg-producing cells infected with vesicular stomatitis virus transported the viral envelope glycoprotein to the cell surface with normal kinetics (half time of ca. 30 min). The secreted HBsAg was comprised of both the unglycosylated (P20) and the glycosylated (G25) polypeptides, characteristic of HBsAg isolated from human serum or secreted from other cell lines (C. W. Crowley, C.-C. Liu, and A. D. Levinson, Mol. Cell. Biol. 3:44-55, 1983; M. F. Dubois, C. Pourcel, S. Rousset, C. Chang, and P. Tiollais, Proc. Natl. Acad. Sci. U.S.A. 77:4549-4553, 1980; C.-C. Liu, D. Yansura, and A. D. Levinson, DNA, 1:213-221, 1982; G. M. Macnab, J. J. Alexander, G. Lecatsas, E. M. Bey, and J. M. Urbanocvicz, Br. J. Cancer, 24:509-515, 1976; A. M. Moriarity, B. H. Hoyer, J. W.-K. Shih, J. L. Gerin, and D. H. Hamer, Proc. Natl. Acad. Sci. U.S.A. 78:2606-2610, 1981; D. L. Peterson, J. Biol. Chem., 256:6975-6983, 1981). The glycosylated polypeptide (GP25) contained complex oligosaccharide chains. Cell-associated HBsAg also was comprised of both an unglycosylated and a glycosylated polypeptide; however, the glycosylated form (GP23) contained only high-mannose oligosaccharide chains. No oligosaccharide processing of the high-mannose chains could be detected within the cells. Thus, most of the time before secretion of HBsAg from cells must have been spent in a pre-Golgi or early Golgi compartment. Glycosylation was inhibited completely by tunicamycin, although unglycosylated particles were still secreted from cells and were antigenic. The secretion and oligosaccharide processing of HBsAg were inhibited with high concentrations of monensin, but at lower concentrations of monensin HBsAg was still secreted, although only half of the oligosaccharide chains were processed to the complex form.

Expression of hepatitis B virus surface antigen in yeast.

The structural gene of Hepatitis B virus surface protein (HBsAg) was introduced into a plasmid capable of autonomous replication and selection in both the yeast Saccharomyces cerevisiae and E. coli. In this plasmid transcription of the HBsAg is initiated by the 5'-flanking sequence of the yeast 3-phosphoglycerate kinase (PGK) gene and terminated by the 3'-flanking region of the yeast TRP1 gene. Yeast cells containing this plasmid produce a new major species of mRNA of 1200 nucleotides in length coding for HBsAg. Viral surface antigen is made in nonglycosylated form at a level of about 1-2 percent of total yeast protein. A small fraction of this polypeptide (2-5 percent) is found in aggregated form upon yeast cell disruption by glass beads. This material is similar in size, density, and shape to the 22nm particle, isolated from the plasma of human hepatitis carriers, and induced comparable levels of HBsAg antibodies in mice when compared with the natural particle.

Release of clathrin from coated vesicles dependent upon a nucleoside triphosphate and a cytosol fraction.

Calf-brain coated vesicles were incubated with ATP and a cytosol fraction. As much as 90% of the clathrin was selectively released within 10 min at 37 degrees C without detectable proteolysis. This uncoating process required the presence of both ATP and cytosol. Empty cages of clathrin could also be dissociated in a similar manner. A nonhydrolyzable analogue, 5'-adenylylimidodiphosphate (AMP-PNP), would not substitute for ATP. Clathrin was dissociated from coats in a form unable to reassemble into cages under standard conditions. These reactions may reflect a segment of a clathrin-coated vesicle cycle in which coats are removed from vesicles after budding.

Effect of truncal vagotomy and pyloroplasty on hepatic bile composition in the rhesus monkey.

Changes in gallbladder motility and alteration of bile composition have been implicated in the formation of gallstones after truncal vagotomy. Hepatic bile composition was found to be unchanged after truncal vagotomy with Heineke-Mikulicz pyloroplasty in our long-term study. . The data suggest that the alleged increase in the incidence of cholelithiasis after vagotomy and pyloroplasty can be isolated from an effect on the liver. These results may have implications for the preferred course of surgical intervention in certain patients.

Retained biliary tract stones. Nonsurgical treatment with capmul 8210, a new cholesterol gallstone dissolution agent.

The ability of Capmul 8210, a commercial solvent that predominantly consists of glyceryl 1-mono-octanoate, to dissolve retained common duct stones by direct infusion into the T-tube was tested in 20 patients with a total of 43 stones. Of 19 patients who completed their infusion, stone disappearance was observed in 15, giving a success rate of 79%. The dissolution time for a single stone averaged four days. A slight rise in serum alkaline phosphatase and amylase levels occurred in some patients, and rapidly returned to normal when treatment was concluded. Other side effects, such as nausea and vomiting epigastric discomfort, or diarrhea, occurred occasionally but were easily controlled medically. We believe that this agent is a useful adjunct in the management of postoperative choledocholithiasis in the patient with an indwelling T-tube.

Antibody development in garter snakes (Thamnophis spp.) experimentally infected with western equine encephalitis virus.

Garter snakes (Thamnophis spp.) have been considered to possibly play an important role in the ecology of western equine encephalitis (WEE) virus. Serological tests (hemagglutination-inhibition, complement-fixation, neutralization test in mice, and plaque neutralization) to detect antibody in these reptiles following laboratory exposure t this virus have, in our experience, been unsatisfactory. A new test, the snake globulin precipitation (SGP) test, has been developed and we consider it to be reliable in detecting antibody in WEE virus-infected garter snakes. Antibody has been detected in these snakes over 4.5 years following inoculation with WEE virus. The SGP test should be a valuable tool in obtaining further information regarding the possible role of these cold-blooded vertebrates in the ecology of this important arbovirus.

Transmembrane movement and distribution of cholesterol in the membrane of vesicular stomatitis virus.

The transmembrane movement and distribution of cholesterol in the vesicular stomatitis virus membrane were studied by following the depletion of cholesterol from virions to interacting phospholipid vesicles and by exchange of radiolabeled cholesterol between virions and phospholipid-cholesterol vesicles. The kinetics of the cholesterol exchange or depletion reactions revealed the presence of two exponential rates: a rapid rate, dependent on the vesicle to virus ratio, and a slower rate, independent of the vesicle to virus ratio. The kinetics of cholesterol movement could be best interpreted by a model of the virion membrane considered as a two pool system in which approximately 30% of the cholesterol resides in the outer monolayer and approximately 70% in the inner monolayer. The half-time for equilibration of the two pools was calculated to be 4--6 h and was assumed to represent the time required for transmembrane movement of cholesterol across the bilayer. The initial rate of transfer of cholesterol from virus into vesicles increased when vesicle phospholipids contained more unsaturated and shorter chain fatty acids. Furthermore, the transfer of cholesterol appeared to occur by a collisional mechanism requiring membrane-membrane contact. Interaction with lipid vesicles did not significantly affect the integrity of the virion membrane as assessed by the relative inaccessibility of internal proteins to lactoperoxidase-catalyzed iodination and by the small loss of [3H]amino acid labeled protein from the virus.