Antigen protein sequences

Polyclonal antisera are usually prepared either from isolated antigens, such as proteins or from synthetic peptides derived from the protein sequence. The antisera derived from small synthetic peptides are regio-specific with respect to the cognate protein and resemble in some way the monoclonal antibodies, but they are much easier to prepare. 

Geng, T., Hahm, B. K., and Bhunia, A. K. (2006a). Selective enrichment media affect the antibody-based detection of stress-exposed Listeria monocytogenes due to differential expression of antibody-reactive antigens identified by protein sequencing. /. Food Prot. 69,1879-1886. 

Outside the remit of this present chapter, it might be noted that a significant number of DNA sequences have had no identifiable function and were initially labeled as junk. However, gradually some functions for this so-called junk DNA have been identified, especially those of a regulatory nature. This has resulted in a greater interest in the possibility of providing DNA sequences that synthesize antigenic proteins. 

Pohlner, K., Portig, I., Pankuweit, S., Lottspeich, F., Maisch, B. (1997). Identification of mitochondrial antigens recognized by antibodies in sera of patients with idiopathic dilated cardiomyopathy by two- dimensional gel electrophoresis and protein sequencing. Am.]. Cardiol. 80, 1040-1045. 

Synthetic peptides can serve as antigens to stimulate the formation of specific antibodies. For instance, as discussed earlier, it is often more efficient to obtain a protein sequence from a nucleic acid sequence than by sequencing the protein itself (see also Chapter 6). Peptides can be synthesized on the basis of the nucleic acid sequence, and antibodies can be raised that target these peptides. These antibodies can then be used to isolate the intact protein from the cell. 

Recombinant a,-PI produced in yeast has also been clinically evaluated. This material is essentially identical to a -PI purified from human serum with respect to its protein sequence and its ability to inhibit neutrophil elastase however, it contains no carbohydrates. As such, one would suspect that the elimination rate following intravenous administration would be similar to that described for desialylated a -PI as described above [225]. In monkeys r-a,-PI disappeared from circulation with a half-life of 69 3 min. compared to a half-life of 2.4 0.2 days for a,-PI isolated from human serum [230], Rapid elimination following parenteral administration does not, however, preclude aerosol administration of the recombinant material. Aerosol administration of yeast-produced r-a,-PI, in doses ranging from 10 to 200 mg, resulted in a dose-dependent elevation of both antigenic recombinant a,-PI and EIC of BALF from apPI deficient individuals. Four hours after administration of a 200 mg dose of recombinant aj-PI, EIC was increased 40-fold over pre-treatment levels. Twenty-four hours post-dose, levels had declined to a 5-fold elevation relative to base-line levels. Modest increases of serum a,-PI levels were observed 24 h post-inhalation of the 200 mg dose [231], In this study, no adverse clinical reactions or evidence of sensitization to recombinant a,-PI were reported. 

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