HCMV envelope antigens induce both humoral and cellular immunity in guinea pigs

Delayed type hypersensitivity to human cytomegalovirus

A skin test for immunity to human cytomegalovirus (HCMV) is described in which skin induration is measured after intradermal injection of antigen derived from heat-inactivated Towne strain HCMV or of envelope prepared from the virus. Randomly selected healthy young adult males and females were prescreened for evidence of past infection with HCMV using serologic tests. Each individual was inoculated with heat inactivated whole virion HCMV antigen prepared from serum-free supernatants of HCMV-infected MRC-5 cells, non-infected MRC-5 cell lysates, and Candida extract. HCMV seropositive individuals developed positive skin reactions to both the Candida extract and the HCMV test antigen. No response was observed at the MRC-5 cell lysate inoculation site. The envelope antigen also elicited a response in seropositive individuals. Seronegative individuals who were negative to the HCMV intradermal antigen at the start of the study developed a positive response 1 week after subcutaneous immunization with live attenuated Towne strain HCMV. This response also correlated with the onset of in vitro proliferation responses to HCMV antigens by peripheral blood lymphocytes obtained from the immunized individuals. Furthermore, skin test and lymphocyte proliferation responses remained positive when tested up to 93 days post-immunization. In guinea pig experiments with HCMV, those animals immunized with purified HCMV or a virus envelope preparation developed strong skin reactions to intradermal injection of each of those antigens. In contrast, no reaction was observed in immune animals, either to viral capsid antigen or uninfected cell-lysate antigen, and no reactions were observed to any HCMV antigen in non-immune animals.

Human cytomegalovirus induces stage-specific embryonic antigen 1 in differentiating human teratocarcinoma cells and fibroblasts

Cell surface expression of stage specific embryonic antigen 1 (SSEA-1), or Lex (III3 FucnLC4), was induced in differentiated human teratocarcinoma cells and in human diploid fibroblasts 3-6 d after infection with human cytomegalovirus (HCMV). In parallel, fucosylated lactoseries glycolipids bearing the SSEA-1/Lex epitope were readily detected in the infected cells but not in the uninfected cells. HCMV infection also results in altered expression of several glycosyltransferases. SSEA-1/Lex induction is probably a consequence of both increased expression of beta 1----3N-acetylglucosaminyltransferase, which catalyzes the rate-limiting step in lactoseries core chain synthesis, and subtle alterations in the relative competition for common precursor structures at key points in the biosynthetic pathway. Since SSEA-1 has been suggested to play a role in some morphogenetic cell-cell interactions during embryonic development, the induction of this antigen at inappropriate times might provide one mechanism whereby intrauterine infection with HCMV can damage the developing fetal nervous system.

Comparative study with monospecific and monoclonal antibodies against a 65 K human cytomegalovirus protein

Immunofluorescence assay using monospecific and monoclonal antibodies to the 65 K major protein of human cytomegalovirus (HCMV) was carried out to monitor the expression of this protein in infected cells. Regardless of differences in the reactivity of the monoclonal antibodies, as determined by immunoblotting and immunofluorescent staining, all stained cytoplasmic inclusion bodies localized to the site of the HCMV-induced receptor for the Fc portion of IgG, suggesting that most of the 65 K major protein of HCMV colocalizes with the HCMV-induced FcR.

Monoclonal antibodies directed to two groups of viral proteins neutralize human cytomegalovirus in vitro

Monoclonal antibodies (MAbs) that neutralized human cytomegalovirus (HCMV) were produced by ten hybrid cells lines, generated from BALB/c mice immunized with HCMV-infected human fibroblasts. By immunoblot technique six antibodies detected a set of HCMV glycosylated polypeptides which, when separated under reducing conditions, migrated with apparent molecular weights (m.wt.) of 47.5K, 51K, 54K, 58K, and 60-69K. One other antibody reacted only with the 47.5 and 51K polypeptides and the 60-69K broad band. Under nonreducing conditions, these antibodies showed no reactivity with any polypeptide. The three remaining MAbs reacted with two high-m.wt. polypeptides of approximately 200K and greater than 200K when separated under nonreducing conditions. One of these antibodies showed no clear reactivity with the polypeptides, one detected a 58K and 92-94K species and one detected a 58K and 130K species, when separated under reducing conditions.

Analysis by immunoblotting of human cytomegalovirus antibody in sera of renal transplant recipient

Human cytomegalovirus-infected cell polypeptides were immunoreacted by sera of renal transplant recipients and compared with those reactive with sera of healthy adult donors by means of the Western immunoblotting technique. At least 15 polypeptides with molecular weights of 155K, 123K, 102K, 89K, 79K, 71K, 65K, 60K, 55K, 50K, 46K, 42K, 38K, 33K, and 28K were immunoreacted. Sera obtained serially from renal transplant recipients reacted with most of these polypeptides and reacted more frequently and intensely with the smaller polypeptide species such as 38K, 33K, and 28K, compared with sera of healthy seropositive adults. The implications of these findings are discussed.

Inhibition by monensin of human cytomegalovirus DNA replication

Monensin, at concentrations which depended on the multiplicity of infection, was found to prevent DNA replication of human cytomegalovirus (HCMV) as well as production of viral progeny in human foreskin fibroblasts. The drug did not affect DNA replication of herpes simplex virus. Inhibition of consecutive HCMV DNA synthesis was also observed following delayed addition of the drug within 12-24 hours postinfection, but was fully reversible upon its removal. Viral replication proceeded, however, without impairment in cultures treated with monensin prior to infection. Induction of viral DNA polymerase activity was not impeded by the inhibitor. Analysis of protein- and glycoprotein synthesis revealed that monensin interfered with the production of a number of HCMV-specific polypeptides. Furthermore, evidence was obtained that the drug may hinder intracellular transport of a 135 kd glycopolypeptide.

Characterization of monoclonal antibodies reactive to several biochemically distinct human cytomegalovirus glycoprotein complexes

Three monoclonal antibodies were characterized by examining their reactivity to human cytomegalovirus (HCMV) glycoproteins under reducing and nonreducing conditions and their reactivity to glycoproteins and disulfide-linked glycoprotein complexes isolated by ion-exchange high-performance liquid chromatography. One monoclonal antibody, 9E10, reacted with glycoprotein complexes which had molecular weights of 93,000 and 450,000 and eluted from the ion-exchange column at 0.3 and 0.9 M NaCl, respectively. All glycoproteins associated in these complexes could be immunoprecipitated under reducing conditions by 9E10, suggesting that they were related to one another. The most abundant glycoproteins immunoprecipitated by 9E10 had molecular weights of 50,000 to 52,000. In contrast to this antibody, two other monoclonal antibodies, 9B7 and 41C2, reacted with glycoprotein complexes which had molecular weights of 130,000 and greater than 200,000 and eluted from the ion-exchange column at 0.6 M NaCl. All glycoproteins associated in these complexes could be immunoprecipitated by 9B7 or 41C2 under reducing conditions, suggesting that they were also related to one another. The most abundant glycoprotein immunoprecipitated by 41C2 or 9B7 had a molecular weight of 93,000. In addition, it was also determined that a 93,000-molecular-weight glycoprotein which was not associated with other glycoproteins by disulfide bonds could not be precipitated by any of the three antibodies, suggesting that it was different from the other glycoproteins. The monoclonal antibodies were also examined for specificity and neutralizing activity. Monoclonal antibodies 41C2 and 9B7 were specific to HCMV as determined by immunofluorescent staining of skin fibroblast cells infected with several different viruses. However, 41C2 did not neutralize Towne strain HCMV, while 9B7 did. The neutralizing activity of 9B7 did require complement. These results suggested that 41C2 and 9B7 reacted with different antigenic sites on the same glycoproteins. Unlike 41C2 and 9B7, monoclonal antibody 9E10 was found to cross-react with adenovirus and herpes simplex virus as determined by immunofluorescent staining of infected skin fibroblast cells. Furthermore, 9E10 neutralized the Towne and Toledo strains of HCMV in the absence of complement.

Immune responses to isolated human cytomegalovirus envelope proteins

A group of envelope proteins of human cytomegalovirus, gA protein (L. Pereira, M. Hoffman, M. Tatsuno, and D. Dondero, Virology 139:73-86, 1984; L. Pereira, p. 383-404, in B. Roizman, ed., The herpesviruses, vol. 3, 1985), and two protein mixtures (58,000-molecular-weight [58K]-66K and 130K-66K), separated by serial columns prepared with anti-gA immunoglobulin G from sera of immunized guinea pigs, induced neutralizing antibodies and a cellular immune response in the animals. The gA is a disulfide-linked protein complex consisting of high-molecular-weight (greater than 200K), 130K-150K, and 55K-58K proteins.

A murine monoclonal antibody recognising a single glycoprotein within a human cytomegalovirus virion envelope glycoprotein complex

Nonionic detergent solubilised polypeptides from highly purified human cytomegalovirus virions were used as immunogens to produce murine monoclonal antibody secreting hybridomas. One monoclonal antibody was shown, by immunoprecipitation followed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), to precipitate three glycoproteins with molecular weights 52, 95, and 130 (all X 10(3)) and one minor component with a molecular weight of 50 X 10(3). When virion envelope components were first separated by SDS-PAGE and electrophoretically transferred to nitrocellulose membranes, this monoclonal antibody recognised two related components with molecular weights 50 and 52 (both X 10(3)). Immunofluorescence studies suggested that these viral antigens were associated with membrane systems of virus-infected cells and were particularly abundant late in infection.