Quantitative microcomplement fixation tests using chicken anti-viral antibody extracted from egg yolk

Potent Inhibition of CD4/TCR-Mediated T Cell Apoptosis by a CD4-Binding Glycoprotein Secreted from Breast Tumor and Seminal Vesicle Cells

We previously isolated a CD4 ligand glycoprotein, gp17, from human seminal plasma; this glycoprotein is identical with gross cystic disease fluid protein-15 (GCDFP-15), a factor specifically secreted from primary and secondary breast tumors. The function of gp17/GCDFP-15 in physiological as well as in pathological conditions has remained elusive thus far. As a follow up to our previous findings that gp17 binds to CD4 with high affinity and interferes with both HIV-1 gp120 binding to CD4 and syncytium formation, we investigated whether gp17 could affect the T lymphocyte apoptosis induced by a separate ligation of CD4 and TCR. We show here that gp17/GCDFP-15 is in fact a strong and specific inhibitor of the T lymphocyte programmed cell death induced by CD4 cross-linking and subsequent TCR activation. The antiapoptotic effect observed in the presence of gp17 correlates with a moderate up-regulation of Bcl-2 expression in treated cells. The presence of gp17 also prevents the down-modulation of Bcl-2 expression in Bcl-2bright CD4+ T cells that is caused by the triggering of apoptosis. Our results suggest that gp17 may represent a new immunomodulatory CD4 binding factor playing a role in host defense against infections and tumors.

Differential antibody reactivity and CD4 binding of the mammary tumor marker protein GCDFP-15 from breast cyst and its counterparts from exocrine epithelia

Analysis of biopsies from breast cancer patients demonstrated that GCDFP-15 (gross cystic disease fluid protein-15) is a specific immunocytochemical marker of primary and secondary apocrine breast tumors. The protein has an amino acid sequence identical to SABP (secretory actin-binding protein), to PIP (prolactin-inducible protein) and to gp17, a protein isolated from human seminal plasma. The latter was found to bind to CD4, a T-cell co-receptor involved in antigen recognition, thereby inhibiting the ability of the receptor to interact with the HIV-1 envelope protein gp120. We compare here the ability of independently purified GCDFP-15, SABP and gp17 and of recombinant PIP both to cross-react with a panel of monoclonal antibodies (MAbs) raised against GCDFP-15 or gp17, respectively, and to bind to CD4. We show that, although the various factors share the ability to bind to the panel of antibodies used, differences in the pattern of MAb recognition can be demonstrated. By comparing the kinetic constants for binding of GCDFP-5 and gp17 to CD4 by biosensor technology, significant differences in binding affinities were observed between the 2 factors, thus reflecting structural differences. Surface plasmon resonance analysis also showed that anti-GCDFP-15 and anti-gp17 antibodies inhibit the binding of CD4 to GCDFP-15 and gp17, respectively, to different extents. Our data thus indicate that, while the various forms of the protein are encoded by the same cDNA, tissue specificities due to post-translational modifications exist. This information may be relevant for developing more sensitive and accurate tests for the use of GCDFP-15 as a diagnostic mammary tumor marker and, most importantly, raises the possibility that GCDFP-15 may constitute a breast tumor-specific antigen.

Antibody production in rabbits and chickens immunized with human IgG. A comparison of titre and avidity development in rabbit serum, chicken serum and egg yolk using three different adjuvants

The antibody response in rabbits and chickens (serum and egg yolk) immunized with human immunoglobulin G was studied during a 1-year immunisation period comparing the efficacy of three adjuvants: Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA) and Hunter's TiterMax adjuvant (HTM). Monthly boosters of the antigen in saline were administered. Adjuvants were used in the initial immunisation and in a booster at week 26. FCA was found to result in the highest titre in both species. FIA was more efficient than HTM in mediating an antibody response in rabbits. In chickens, FIA resulted in similar antibody titres in serum and egg yolk. The effect of HTM was similar to FIA in chicken serum but lower in egg yolk. The titres obtained in rabbits were approximately a factor 1.5-2.0 higher than in the corresponding chicken groups. However, the antibody productivity of the chicken, when using the egg yolk as the antibody source, was a factor 5-10 higher than that of the rabbit depending on the adjuvant used. FCA and FIA resulted in similar antibody avidity in rabbits whereas HTM had a lesser effect. In chickens FCA initially resulted in the highest antibody avidity in both serum and egg yolk, but after the booster with adjuvant the antibody avidity became similar for all three adjuvants.

Use of egg-yolk antibody for detection of respiratory syncytial virus in nasal secretions by ELISA

Egg-yolk immunoglobulins extracted from the eggs of hens immunized with respiratory syncytial virus (RSV) have been used as a reagent in double sandwich ELISA for detecting RSV in nasal secretions. The sensitivity of virus detection was the same in indirect ELISA, using rabbit anti chicken globulin conjugate, as when biotinylated yolk globulin and labeled avidin were used for detection. The specificity of ELISA for detecting RSV using yolk antibody was similar to that achieved by indirect immunofluorescence using commercial reagents of mammalian origin. Purified immunoglobulin was easily extracted from egg yolk; the amount of globulin present in a single preparation obtained from a batch of ten eggs was sufficient to carry out 10(6) ELISA tests for RSV detection.