Comparative studies of HSV-1 antigens solubilised from infected cells by using non-ionic or zwitterionic detergents

HSV-1 antigen preparations solubilised from Vero cells by using either the non-ionic detergent Nonidet P40 or the zwitterionic detergent Empigen BB, and purified on sucrose density gradients or over a sucrose cushion, were tested by ELISA with anti-HSV-1 glycoprotein monoclonal antibodies and by radioimmunoprecipitation (RIP) with polyclonal HSV-1 antiserum. Amongst several proteins detected in these preparations, the four major HSV-1 glycoproteins, gB, gC, gD, and gE, were found to be present. Differences between NP40 or Empigen-solubilised HSV-1 antigen preparations with respect to two of these glycoproteins, gB and gE, were detected by using a small panel of monoclonal antibodies. Comparative studies in mice showed the Empigen-solubilised HSV-1 antigen preparations elicited greater antibody responses and greater protection against lethal HSV-1 challenge infection than the NP40-solubilised preparation.

Synthesis and applications of 8-azido photoaffinity analogs of P1,P3-bis(5'-adenosyl)triphosphate and P1,P4-bis(5'-adenosyl)tetraphosphate

32P-labeled photoaffinity analogs of bis(5'-adenosyl)-tetraphosphate and bis(5'-adenosyl)triphosphate which contain a single photoreactive 8-azidoadenosine group distal to the radiolabel have been synthesized from commercially available components using a combination of chemical and enzymatic procedures including a water-soluble carbodiimide. The method is simple, rapid, and produces yields of high specific activity products of around 60%. The analog of bis(5'-adenosyl)-tetraphosphate is very similar to the parent compound in its inhibition of rat liver adenosine kinase and its efficiency as a substrate for the bis(5'-nucleosidyl)tetraphosphate pyrophosphohydrolase from Artemia embryos. In the latter case, ATP and 8-azidoAMP are the preferred products. As would be expected, this analog is a much more effective photoprobe for both adenosine and adenylate kinases than the corresponding analog of bis(5'-adenosyl)triphosphate. Both compounds have been used to photoaffinity label crude extracts of Artemia, Vero cells, and Clostridium acetobutylicum and preferential specific labeling of different polypeptides by each analog has been shown. In extracts of C. acetobutylicum, the labeling of a polypeptide of Mr 48,500 by the bis(5'-adenosyl)tetraphosphate analog was totally dependent on the presence of Co2+ ions. These compounds should therefore prove valuable both for the active site labeling of purified binding proteins and for the detection and identification of new target proteins for these nucleotides.

Zwitterionic detergent solubilisation of HSV-1 surface antigens

A preparation was obtained from herpes simplex virus type 1 (HSV-1)-infected cells using a zwitterionic detergent, Empigen BB. The preparation was partially-purified either by ultracentrifugation over a cusion of 20% sucrose or on a sucrose density gradient. Partial characterisation of these materials by ELISA, using both polyclonal and monoclonal antibodies showed them to contain at least four major HSV glycoproteins, gB, gC, gD and gE. Comparison of Empigen-extracted HSV-1 antigen preparations with preparations obtained using the non-ionic detergents Nonidet P40 or Triton-X-100 indicate that, using conventional procedures, separation of glycoproteins, B, C, D, and E from unwanted proteins may be facilitated using the former detergent. Immunization of mice with Empigen-extracted, partially-purified or gradient-purified antigen preparations elicited good levels of antibody detectable by ELISA and a high degree of protection against both HSV-1 and HSV-2 challenge infection. Such protection could be achieved using aqueous antigen preparations, but was augmented using aluminium hydroxide gel as an adjuvant. In general, Empigen-extracted HSV-1 antigen preparations elicited higher ELISA antibody levels and more complete protection against HSV challenge infection than NP40 or Triton-X-100-extracted preparations. The value and usefulness of the detergent Empigen for obtaining HSV surface antigen preparations and the role of these as potential vaccines against HSV infections, is discussed.

Evaluation of ELISA, RPLA, and Vero cell assays for detecting Clostridium perfringens enterotoxin in faecal specimens

Three hundred and ninety two faecal specimens from 70 separate outbreaks of suspected Clostridium perfringens food poisoning were examined by enzyme linked immunosorbent assay (ELISA), reversed passive latex agglutination (RPLA), and Vero cell assays for the presence of enterotoxin. Although the most time consuming method, ELISA was the most specific and reproducible. RPLA was slightly more sensitive than ELISA, but it showed some non-specific reactions. The Vero cell assay was the least sensitive and least reproducible method, being affected by some non-specific cytotoxic and cytotonic reactions. Normal rabbit serum should be included in the Vero cell assay as a control for the neutralisation of cytotoxic effects.

The Vero cell receptor for the hepatitis B virus small S protein is a sialoglycoprotein

The Vero (African green monkey kidney-derived) cell line is capable of binding recombinant hepatitis B surface antigen (rHBsAg) particles containing only the small surface (S) protein of hepatitis B virus (HBV). This binding activity appears to be due to a single major population of receptors (M. E. Peeples et al., Virology 160, 135-142 (1987]. Since infectious HBV particles also contain the small S protein, it is possible that the Vero cell receptor might also function as an HBV receptor. The initial physical characterization of this receptor is reported here. Treatment of Vero cells with each of four proteases reduced their binding activity by 70% or greater, indicating that the receptor is partially protein in nature. Binding activity was also reduced by pretreating cells with neuraminidase or low levels of sodium periodate, indicating that sialic acid also plays a major role in the receptor activity. Consistent with this interpretation, N-acetylneuraminic acid and N-acetylneuraminyl-lactose were able to competitively inhibit rHBsAg particle attachment to Vero cells. The protein nature of the Vero cell receptor was confirmed by the demonstration that chymotrypsin treatment which resulted in 70% loss of binding had little effect on the cell sialic acid content. Therefore, the Vero cell receptor for rHBsAg particles is a sialoglycoprotein.

A cultured cell receptor for the small S protein of hepatitis B virus

Human hepatitis B virus (HBV) has not been passaged in established cell culture systems. To determine whether this inability results from the lack of a receptor, 30 cell lines were examined for their abilities to bind 125I-labeled recombinant hepatitis B virus surface antigen (rHBsAg) particles. These particles contained only the small surface (S) protein, which is also found in the envelope of infectious HBV particles. Only two cells lines, both derived from African green monkey kidney, were able to bind a large portion of the 125I-rHBsAg particles. Binding to one of these cell lines, Vero, was found to be specific by three criteria: it was competitively inhibited by nonradioactive particles, it was saturable, and it could be blocked by chimpanzee antiserum raised against the rHBsAg particles. Analysis of the binding data indicated a single major population of high affinity receptor sites: 2.7 X 10(5) sites/cell, Kd = 2.8 nM. Binding was not due to the covalently linked 125I tracer isotope because unlabeled particles also bound, as detected with a monoclonal antibody. Binding was not unique to this recombinant particle preparation since serum-derived particles also bound to Vero cells. These results indicate that the Vero cell line expresses a receptor for the small S protein of HBV and that the small S protein, alone, may function as the HBV attachment protein.

Glycosylated components induced in African swine fever (ASF) virus-infected Vero cells

African swine fever (ASF) virus production was inhibited more than 100 fold by 5 mM glucosamine, 2 mM 2-deoxyglucose and 3 microM tunicamycin. ASF virus induced in Vero cells the synthesis of 19 glycosylated components of molecular weights ranging from 9K to 220K, the major ones being those of 9K, 13K, 14K, 74K and 220K. At least five of the induced glycosylated components, of molecular weights 13K, 33K, 34K, 38K and 220K, were probably virus-coded glycoproteins, as suggested by a comparative analysis of the time course of synthesis and the antigenicity of these components in extracts from [35S]methionine or [14C]glucosamine-labeled infected cells. The non-protein glycosylated components present in extracellular ASF virus particles had a cellular origin.

Expression of the HSV specified major DNA-binding protein in virus infected RAJI and VERO cells

We studied the expression of the Herpes Simplex virus type-2 (HSV-2) specified major DNA-binding protein (ICSP 11/12) in virus infected RAJI and VERO cells. Immunofluorescence staining by a specific ICSP 11/12 antiserum distinguished between different cell-virus interactions. ICSP 11/12 synthesized in the HSV-2 infected VERO cells showed dense homogenous nuclear staining early in the infection. During virus replication the pattern changed into a less dense, somewhat marginating staining. The corresponding protein synthesized during persistent HSV-2 infection in the RAJI cells showed granular cytoplasmic staining. Late in the infection a whole cell fluorescence was noted. In the absence of virus DNA-synthesis (PFA treated VERO cells) ICSP 11/12 showed dense homogenous or speckled nuclear pattern. The ICSP 11/12 protein extracted from the different virus-cell interactions also showed different elution from double stranded DNA.

Characterization of novel viral polyproteins detected in cells infected by the flavivirus Kunjin and radiolabelled in the presence of the leucine analogue hydroxyleucine

Vero cells were infected by Kunjin virus and radiolabelled in the presence of the leucine analogue, threo-beta-hydroxy-DL-leucine (THL). This analogue is known to prevent preprotein processing in cell-free systems when incorporated into signal peptides. Novel Kunjin virus-specified proteins were detected, namely gp140, p120 and gp92; the designations for the proteins indicate their approximate Mr X 10(-3) and whether they are glycosylated. The glycoproteins gp140 and gp92 were observed in cells labelled with [3H]mannose and bound to concanavalin A. Limited proteolytic digestion of gp140, gp92 and gp66 (related to the envelope protein E), and tryptic peptide mapping of these three glycoproteins and p120 indicated that all four were closely related. The glycoproteins gp140 and gp92 were also detected in cells infected by West Nile virus radiolabelled in the presence of THL. Other effects of THL in Kunjin virus-infected cells were a reduction in the incorporation of radioactive amino acids or mannose, a decrease in the yield of haemagglutinin and infectious virus, an inhibition of processing of gp66 to gp53 and an apparent inhibition of synthesis of P98 and P71. We suggest possible explanations for the THL-induced changes in infected cells based on recent models proposed for the synthesis of the yellow fever and West Nile viral proteins.

Immunolocalization and partial characterization of a nucleolar autoantigen (PM-Scl) associated with polymyositis/scleroderma overlap syndromes

Precipitating anti-PM-Scl antibodies are present in sera from patients with polymyositis, scleroderma, and polymyositis/scleroderma overlap syndromes. By indirect immunofluorescence microscopy, anti-PM-Scl antibodies stained the nucleolus in cells of different tissues and species, suggesting that the antigen is highly conserved. By electron microscopy, anti-PM-Scl antibodies reacted primarily with the granular component of the nucleolus. Drugs that inhibit rRNA synthesis had a marked effect on the expression of PM-Scl antigen. In actinomycin D-treated cells, immunofluorescence staining by anti-PM-Scl was significantly reduced with residual staining restricted to the granular regions of nucleoli. Treatment with 5,6-dichloro-beta-D-ribofuranosylbenzimidazole (DRB) also selectively reduced nucleolar staining. On a molecular level, anti-PM-Scl antibodies precipitated 11 polypeptides with molecular weights (Mr) ranging from 110,000 to 20,000. The Mr 80,000 and 20,000 polypeptides were phosphorylated. Evidence suggests that the PM-Scl antigen complex may be related to a preribosomal particle.