Immunogenic determinants

Some drugs such as penicillin have been shown to induce autoimmunity as well as anaphylaxis (Gleichman et al., 1989). The carbonyl of the /1-lactam ring of penicillin can form a covalent penicilloyl conjugate with nucleophilic sites on proteins, particularly the amino groups of lysine residues. This conjugate, which acts as the major immunogenic determinant, may become biotransformed to other isomeric forms of clinical relevance (Batchelor et al., 1965). 

LPSs carry the major immunogenic determinants on the cell surface of Gram-negative bacteria and, in many instances, serve as the basis for their serological classification. In this section, contribution of LPSs that contain 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids to the immunospecificity and serological classification of two human pathogens, viz. L. pneumophila and P. aeruginosa, are reviewed. 

Figure 5 shows the results of a competitive ELISA with Ala-D-iso-Glu-Lys-D-Ala-D-Ala (pentapeptide), Lys-D-Ala-D-Ala, Ala-D-Ala-D-Ala, Ala-D-iso-Glu, Ala-D-iso-Glu-Lys, D-Ala-D-Ala, and Lys-D-Ala-D-Lac. The antibody reacted strongly with pentapeptide and Lys-D-Ala-D-Ala but weakly with Ala-D-Ala-D-Ala, suggesting that the immunogenic determinant of the pentapeptide to this antibody resides in the last three residues, Lys-D-Ala-D-Ala. Figure 6 shows that the cross-reactivities of the pentapeptide and stem peptide in the competitive ELISA were virtually identical. 

DEC is known to produce morphological changes on the surface of microfilariae. However, this change is not enough to cause death of the parasite [112]. It has also been shown that DEC enhances the specific IgG-mediated cell adherance on B.malayi microfilariae, which may be achieved by exposing the "hidden" antigenic determinant sites [119]. Martinez-Paloma [120] have shown that the immunogenic determinants of microfilariae of Onchocerca sp. are covered by an acellular cuticle. 

It has been shown (for review see Du Pasquier, 1973) in studies with tadpoles, that the first antibody response could be detected in spleens containing 10 cells. A small larvae of Xenopus laevis at 4 weeks of larval life may have about half a million lymphocytes, from which (if thymus cells, immature cells and T cells are subtracted) not more than 100000 lymphocytes might be presursors of antibody-forming cells. Are these 100000 cells able to cope with the whole spectrum of immunogenic determinants which an animal of this size may encounter ... 

Standardization and Testing". RequHemeats are geaerally specified within Hceases Hi the United States, and include a variety of Hi-process tests to assess purity, safety, and potency of the iadividual components and potency and safety of the final product. Potency is standardized by determining the size of the conjugate and the quantitative amount of saccharide that is bound to the carrier protein. General safety and immunogenicity is assessed Hi animals. 

Position of spacer arm. The position of the linker group on the target analyte that connects it to the immunogen has a profound influence on the selectivity and sensitivity of the subsequent assays. The handle should be attached as far as possible from the unique determinant groups, allowing maximum exposure of the important... 

Moudgil, K. D., Sercarz, E. E. and Grewal, I. S. (1998), Modulation of the immunogenicity of antigenic determinants by their flanking residues , Immunol. Today, 19, 217-220. 

Add peptide hapten to the carrier solution to obtain a concentration of about 2mg/ml. Alternatively, determine the molar ratio of peptide to carrier. Ratios of 20 1 to 40 1 (peptide carrier) usually result in good immunogens. 

Chamberlain, N.R., Deogny, L., Slaughter C., Radolf, J.D., and Norgard, M.V. (1989) Acylation of the 47-kilodalton major membrane immunogen of Treponema pallidum determines its hydrophobicity. Infect. Immun. 57, 2878-2885. 

Dintzis, R.Z., Okajima, M., Middleton, M.H., Greene, G., and Dintzis, H.M. (1989) The immunogenic-ity of soluble hapenated polymers is determined by molecular mass and hapten valence. J. Immunol. 143,1239-1244. 

Several plant vims coat proteins, including those of TMV, CPMV, AlMV and Tomato bushy stunt vims (TBSV), have been used to produce and deliver antigenic determinants from a variety of viral and bacterial pathogens. These data have been summarized in numerous publications and several reviews [12,13]. The ease of virus purification coupled with enhanced peptide immunogenicity when fused to carrier molecules makes this approach very attractive for vaccine development. 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (RIA). Analyses by this method employ substoichiometric amounts of specific binding immuno-chemical reagents for the determination of a wide range of materials (immunogens) which can be made to produce immunological responses in animals such as sheep or rabbits. It is possible to combine the specificity of an immunochemical reaction with the extreme sensitivity of radiotracer detection. Analytical methods based upon these principles have achieved wide applicability in the determination of organic compounds at trace levels. 

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