Monoclonal anti-idiotypes induce neutralizing antibodies to enterovirus 70 conformational epitopes

Enterovirus 70 binds to different glycoconjugates containing alpha2,3-linked sialic acid on different cell lines

Enterovirus 70 (EV70), the causative agent of acute hemorrhagic conjunctivitis, exhibits a restricted tropism for conjunctival and corneal cells in vivo but infects a wide spectrum of mammalian cells in culture. Previously, we demonstrated that human CD55 is a receptor for EV70 on HeLa cells but that EV70 also binds to sialic acid-containing receptors on a variety of other human cell lines. Virus recognition of sialic acid attached to underlying glycans by a particular glycosidic linkage may contribute to host range, tissue tropism, and pathogenesis. Therefore, we tested the possibility that EV70 binds to alpha2,3-linked sialic acid, like other viruses associated with ocular infections. Through the use of linkage-specific sialidases, sialyltransferases, and lectins, we show that EV70 recognizes alpha2,3-linked sialic acid on human corneal epithelial cells and on U-937 cells. Virus attachment to both cell lines is CD55 independent and sensitive to benzyl N-acetyl-alpha-D-galactosaminide, an inhibitor of O-linked glycosylation. Virus binding to corneal cells, but not U-937 cells, is inhibited by proteinase K, but not by phosphatidylinositol-specific phospholipase C treatment. These results are consistent with the idea that a major EV70 receptor on corneal epithelial cells is an O-glycosylated, non-glycosyl phosphatidylinositol-anchored membrane glycoprotein containing alpha2,3-linked sialic acid, while sialylated receptors on U-937 cells are not proteinaceous.

Identification of group I porcine enteroviruses by monoclonal antibodies in cell culture

A panel of monoclonal antibodies (mAb) against porcine enteroviruses (PEV) was established. One of these mAbs reacts group-specifically with PEV of serotype group I in the indirect immunofluorescence assay (IIF). This mAb is very well suited for diagnosis of PEV infections. However, the mAb neither neutralizes virus nor does it react with virus particles in immuno electron microscopy (IEM). Another mAb is PEV-1 specific in IIF, neutralizes virus, and is suited for IEM. Both mAbs presumably recognize conformation-dependent epitopes of the virus.

Heat shock response of Streptococcus pneumoniae: identification of immunoreactive stress proteins

In order to investigate whether pneumococcal heat shock proteins (HSPs) were major immunogens of humoral immune response, we first characterized the heat shock response of S. pneumoniae. Three HSPs, HSP62, HSP72 and HSP80, having an apparent molecular mass of 62, 72, and 80 kDa, respectively, were detected by labelling proteins synthesized with [35S]methionine after a shift from 37 degrees C to 45 degrees C and fluorography of SDS-polyacrylamide gels. Radioimmunoprecipitation and immunoblot analyses with mouse anti-pneumococcal sera revealed that HSP72 was a major immunogen. S. pneumoniae HSP62 was another antigen which was precipitated by some immune sera. Anti-HSP72 antibodies appeared after the first immunization with S. pneumoniae antigens and subsequent immunization elicited a booster response. Monoclonal antibodies (MAbs) to pneumococcal HSP72 were produced and their specificities defined. The epitopes reactive with four MAbs are highly conserved in S. pneumoniae since 20 out of 20 different strains were recognized by each individual MAb. Western blot analysis revealed cross-reactivities with few non-pneumococcal strains. By N-terminal sequence analysis, the S. pneumoniae HSP72 was found to belong to the heat shock protein 70 family. That HSP72 is an important highly conserved antigen in S. pneumoniae should provide a basis for further investigation of its physiological and potential pathogenic role.

Nucleotide sequence analysis of recent epidemic strains of enterovirus 70

Nucleotide sequences of the genome of enterovirus 70 (EV70) isolated in Osaka in 1993 were determined, and compared with those of the past epidemic strains. Nucleotide substitution rates in 332 bp, 174 bp, and 178 bp of the genes encoding viral protein (VP)1, VP2, or VP3 were 9.0, 7.5, and 5.6% between Kumoi-2/93 and J670/71, respectively. Likewise, the putative amino acid substitution rates were 1.8, 0, and 0%. It seems that the epidemic strains of EV70 in Japan have been evolving at a constant high nucleotide substitution rate but almost all the substitutions were synonymous.

Moloney leukemia virus-induced cell surface antigen mimicry by monoclonal antibodies

We have investigated antigen-independent modulation of immune responses by monoclonal antibodies directed against both viral and nonviral antigens. BALB/c mice were immunized with monoclonal IgM (i.e. Ab1) specific for either Moloney murine leukemia virus-induced cell surface antigen (MCSA) or the hapten 2,4-dinitrophenyl (DNP). Injection with either Ab1 activated a functional idiotypic (Id) network as evidenced by production of both anti-Id (Ab2) antibodies and anti-anti-Id (Ab3) antibodies. A subset of induced Ab3 (designated Ab1'), exhibited specificity for antigen (virus or DNP). In mice immunized with anti-Id antibodies (Ab2), production of Ab3 and Ab1' was also observed. In the MCSA system, antibody-induced Ab1' responses were effective in protecting mice from tumor development upon subsequent challenge with live virus. Furthermore, antigen-independent modulation of immunity to both viral and nonviral antigens was found to be thymus-dependent. Similar findings in other viral systems suggest that antibody-induced activation of Id networks may prove a viable alternative vaccine strategy that can elicit antigen-specific responses, and in some cases protection, in the apparent absence of exposure to antigen.

Anti-idiotypic mimicry of a neutralizing epitope on the glycoprotein B complex of human cytomegalovirus

Experiments were carried out to investigate the ability of rabbit anti-idiotype antibodies (Ab2), directed against an anti-human cytomegalovirus monoclonal antibody (Ab1), to induce neutralizing antibodies specific for the immunodominant glycoprotein B viral complex. Mice immunized with Ab2 produced anti-Ab2 (Ab3) that was both antigen and idiotype specific with regard to Ab1. We conclude that the Ab2 antibodies mimicked a neutralizing epitope and acted as a network antigen for inducing a specific anti-human cytomegalovirus antibody response in this experimental system.

A novel approach to the laboratory diagnosis of Chlamydia trachomatis infections using monoclonal anti-idiotypic antibodies

We have developed a novel enzyme immunoassay (EIA) for the specific detection of Chlamydia trachomatis utilizing a monoclonal anti-idiotypic antibody to an antibody directed against a chlamydia specific epitope on 60 kDa heat-shock protein (HSP60). The basis of the assay is the inhibition of the binding of idiotype to anti-idiotype by antigen present in test samples. Two configurations of the assay were developed: a blocking EIA and a competition EIA. Greater sensitivity was observed using the competition EIA, with the assay detecting purified recombinant HSP60 and purified chlamydia in a concentration-dependent manner from 0.01 to 10 micrograms protein and from 0.5 to 12 micrograms total protein, respectively. The assay is highly specific and offers several potential advantages over currently available EIAs for the detection of this pathogen.