A new method to discriminate immunogen-specific heavy-chain homodimer from heterotetramer immunoglobulin G directly in immunized dromedary whole plasma proteins: Western ligand blotting

Ficus sycomorus latex: An efficient alternative Egyptian source for horseradish peroxidase in labeling with antibodies for immunodiagnostic kits

Aim:

In view of various peroxidase applications, the searching for new sources of unique peroxidase properties is highly desirable. The present study aims to evaluate the efficiency of the peroxidase of locally grown sycamore latex (POL) for conjugation with antibodies and to study the conjugate optimal conditions, storage stability, and affinity toward different substrates as compared with commercial horseradish peroxidase (HRP).

Materials and Methods:

Anti-mouse antibodies were prepared in rabbits and purified by protein A sepharose affinity column chromatography. The POL and HRP conjugates were prepared by one-step glutaraldehyde coupling method. The reactivity of the prepared conjugates was examined using the enzyme-linked immunosorbent assay (ELISA). The optimal enzymatic conditions, storage stability, and affinity toward substrates were also determined for both the conjugates.

Results:

The POL showed higher percent recovery (98%) than HRP (78%) over the initial activity after conjugation process. The POL and HRP conjugates showed ELISA titers of 1:120 and 1:80, respectively, demonstrating high binding affinity of POL-conjugate. The POL-conjugate showed high thermal stability up to 70°C compared with HRP-conjugate up to 40°C. After conjugation, POL had wide pH stability (5.0-8.0) compared with HPR (4.5-6.0). Both of the prepared conjugates had a high affinity toward the substrates used in immunoassays with lower K_m values. The POL-conjugate showed high storage stability for its enzymatic activity and ELISA titer compared with HRP-conjugate after 1 year at −20°C.

Conclusion:

The POL of Ficus sycomorus latex is an efficient source for labeling antibodies and could be utilized in immunodiagnostic kits.

Preparation of goat and rabbit anti-camel immunoglobulin G whole molecule labeled with horseradish peroxidase

Aim:

As the labeled anti-camel immunoglobulins (Igs) with enzymes for enzyme-linked immunosorbent assay (ELISA) are unavailable in the Egyptian market, the present investigation was directed for developing local labeled anti-camel IgG with horseradish peroxidase (HRP) to save hard curacy.

Materials and Methods:

For purification of camel IgG whole molecule, camel sera was preliminary precipitated with 50% saturated ammonium sulfate and dialyzed against 15 mM phosphate-buffered saline pH 7.2 then concentrated. This preparation was further purified by protein A sepharose affinity column chromatography. The purity of the eluted camel IgG was tested by sodium dodecyl sulfate polyacrylamide gel electrophoresi. Anti-camel IgG was prepared by immunization of goats and rabbits separately, with purified camel IgG. The anti-camel IgG was purified by protein A sepharose affinity column chromatography. Whole molecule anti-camel IgG was conjugated with HRP using glutraldehyde based assay. Sensitivity and specificity of prepared conjugated secondary antibodies were detected using positive and negative camel serum samples reacted with different antigens in ELISA, respectively. The potency of prepared conjugated antibodies was evaluated compared with protein A HRP. The stability of the conjugate at −20°C during 1 year was assessed by ELISA.

Results:

The electrophoretic profile of camel IgG showed four bands of molecular weight 63, 52, 40 and 33 kDa. The recorded sensitivity and specificity of the product are 100%. Its potency is also 100% compared to 58-75% of commercial protein A HRP. The conjugates are stable for 1 year at −20°C as proved by ELISA.

Conclusion:

Collectively, this study introduces goat and rabbit anti-camel IgG whole molecules with simple, inexpensive method, with 100% sensitivity, 100% specificity and stability up to 1 year at −20°C. The important facet of the current study is saving hard curacy. Future investigations are necessary for preparation of IgG subclasses.

A one-step exclusion-binding procedure for the purification of functional heavy-chain and mammalian-type gamma-globulins from camelid sera

A new approach has recently been proposed for the purification of 'mammalian-type' IgG, consisting of exclusion binding. The technique uses a gel ('Melon gel'; Pierce) that binds to all plasma proteins, but not to IgGs, thus allowing IgGs to be recovered in the FT (flow-through) fraction. Here, the technique was applied to camelid IgGs, which are known to be composed of not only classic mammalian-type IgGs (IgG1) but also HC-IgGs (heavy chain IgGs). Both mammalian type and HC-IgGs can be purified in the FT fraction of dromedary (Camelus dromedarius) plasma samples with less than 8.5% contamination, by making minor improvements to the conditions recommended by the manufacturer. The contaminant proteins, as determined by LC-MS/MS (liquid chromatography-tandem MS), are mainly transferrin and albumin. The recovery rate is elevated for both types of IgGs (95+/-14% and 88+/-25% for IgG1 and HC-IgGs respectively). IgGs thus purified maintain their ability to bind to their antigen, as measured by surface plasmon resonance and Western ligand blotting. Furthermore, IgGs can be purified from plasma samples of all camelid species in a similar manner, although the ratio of HC-IgGs to total IgGs was lower for Lama (llama) and Vicugna (vicuña) than for Camelus species. The 'Melon gel' technique can thus be used to satisfactorily purify IgG1 and HC-IgGs from all camelid species.