Induction of neutralizing antibodies to transmissible gastroenteritis virus by anti-idiotypic antibodies

Evidence that two distinct populations of rabbit anti-idiotypic antibodies are induced by three monoclonal antibodies specific for bluetongue virus core protein VP7

Three groups of anti-idiotypic antibodies (anti-Id or Ab2), designated RAb2-A, RAb2-B1, and RAb2-B2, were isolated from rabbit antiserum raised against three monoclonal antibodies (mAbs) (M1875, M1877, and M1886) specific for the bluetongue virus core protein, VP7. RAb2-A was specific for the idiotype of M1875. RAb2-B1 and RAb2-B2, isolated through the M1877 and M1886 affinity columns, respectively, were directed against the common idiotype that is shared by M1877 and M1886 and therefore classified in the same population (RAb2-B). Further characterization revealed that the two anti-Id populations, RAb2-A and RAb2-B, were significantly different. RAb2-A was an Ab2 beta type of anti-Id since (i) its reaction with M1875 was inhibited by the antigen; (ii) it inhibited the M1875-VP7 interaction; and (iii) it elicited anti-VP7 antibody response in Balb/c mice. In contrast, RAb2-B may represent an Ab2 alpha type of anti-Id since its reactions with M1877 or M1886 were not inhibited by the antigen, even though it inhibited mAbs from binding to the antigen. These results indicated that RAb2-A and RAb2-B represent two distinct populations of anti-Ids to anti-VP7 mAbs with similar epitope specificity.

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.

Bovine viral diarrhea virus-specific neutralizing antibodies induced by anti-idiotypic antibodies

Two murine neutralizing monoclonal antibodies (MAbs), 4D8 and 6D11, recognizing epitopes on gp53, a surface glycoprotein of bovine viral diarrhea virus (BVDV), were used to generate anti-idiotypic antibodies (anti-ids) in a calf. The polyclonal anti-ids were isolated from serum by affinity chromatography on their respective Ab-1-Sepharose columns, followed by repeated adsorption on isotype-matched antibody-Sepharose columns. The anti-ids reacted specifically with their respective Ab-1, but not with isotype-matched controls. They also inhibited the binding of their Ab-1 to BVDV in a concentration-dependent manner. Mice immunized with the two anti-id preparations developed antibodies to BVDV, which neutralized the virus in vitro.

A conserved coronavirus epitope, critical in virus neutralization, mimicked by internal-image monoclonal anti-idiotypic antibodies

Monoclonal antibody (MAb) 6A.C3 neutralizes transmissible gastroenteritis coronavirus (TGEV) and is specific for a conserved epitope within subsite Ac of the spike (S) glycoprotein of TGEV. Six hybridomas secreting anti-idiotypic (Ab2) MAbs specific for MAb 6A.C3 (Ab1) have been selected. All six MAbs inhibited the binding of Ab1 to TGEV and specifically cross-linked MAb1-6A.C3. Four of these hybridomas secreted gamma-type anti-idiotypic MAbs. The other two Ab2s (MAbs 9A.G3 and 9C.E11) were recognized by TGEV-specific antiserum induced in two species. This binding was inhibited by viruses of the TGEV group but not by serologically unrelated coronaviruses. These results indicate that MAb2-9A.G3 and MAb2-9C.E11 mimic an antigenic determinant present on the TGEV surface, and they were classified as beta-type ("internal-image") MAbs. TGEV-binding Ab3 antiserum was induced in 100% of mice immunized with the two beta-type MAb2s and in 25 to 50% of mice immunized with gamma-type MAb2. Both beta- and gamma-type Ab2s induced neutralizing Ab3 antibodies in mice that were mainly directed to antigenic subsite Ac of the S protein.

Anti-idiotypic antibodies mimic bovine viral diarrhea virus antigen

Polyclonal rabbit anti-idiotypic antibodies (anti-ids) against two neutralizing murine monoclonal antibodies (mAbs) specific to a bovine viral diarrhea virus (BVDV) glycoprotein, 53 kDa, were produced, purified, and characterized. Each anti-id inhibited the binding of its respective mAb to BVDV antigen in a competitive ELISA and blocked the immunoprecipitation of the 53 kDa protein by the mAb. The anti-ids also inhibited the virus-neutralizing activity of their homologous mAbs. These results suggest that the anti-ids bear an internal image of a BVDV antigen and mimic neutralizing epitopes on the 53 kDa protein. Treatment of MDBK cells with the anti-ids inhibited BVDV infection, indicating that they block a cellular component, such as a virus receptor, required for virus adsorption or entry. Inhibition of the homologous mAb and lack of inhibition of the heterologous mAb indicate that the anti-ids are specific for the unique antigen-binding sites on the mAbs.

Interfaces of the yeast killer phenomenon

A new prophylactic and therapeutic antimicrobial strategy based on a specific physiological target that is effectively used by killer yeasts in their natural ecological competition is theorized. The natural system exploited is the yeast killer phenomenon previously adopted as an epidemiological marker for intraspecific differentiation of opportunistic yeasts, hyphomycetes, and bacteria. Pathogenic microorganisms (Candida albicans) may be susceptible to the activity of yeast killer toxins due to the presence of specific cell wall receptors. On the basis of the idiotypic network, we report that antiidiotypic antibodies, produced against a monoclonal antibody bearing the receptor-like idiotype, are in vivo protecting animals immunized through idiotypic vaccination and in vitro mimicking the antimicrobial activity of yeast killer toxins, thus acting as antibiotics.

Induction of immune response to bovine herpesvirus-1 with anti-idiotypic antibodies

Previously, we prepared rabbit anti-idiotypic (anti-Id) antibodies against murine monoclonal antibodies (MAbs) specific for the major bovine herpesvirus-1 (BHV-1) envelope glycoproteins. Glycoprotein III (gIII) contains neutralization epitopes and may be the virus attachment protein. Anti-Id antibodies to a neutralizing MAb that reacts with gIII were purified by sequential immunoaffinity chromatography. Immune responses to the purified anti-Id reagent and BHV-1 were compared in mice. Both groups of mice produced BHV-1-specific neutralizing antibodies. However, lymphocyte proliferative responses and interferon and interleukin-2 production were specific for the respective immunizing antigens. These results suggest that the anti-Id reagent may bear an internal image of a B-cell-stimulating epitope of glycoprotein gIII; however, this epitope does not stimulate a virus-specific cellular immune response in mice.