Antiviral response elicited by a completely synthetic antigen with built-in adjuvanticity.

Abstract

In a previous study we demonstrated that antiviral response against the coliphage MS-2 can be elicited by immunization with a synthetic antigen consisting of a conjugate (P2-A --L) of a synthetic fragment (P2) of the virus coat protein attached to a synthetic polymeric carrier. The antiviral response was induced when the antigen was administered in complete Freund's adjuvant or when it was administered in incomplete adjuvant, provided that a peptidoglycan was covalently attached to it. In the present study we demonstrate the adjuvant effect of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) in this system. Immunization with a mixture of MDP and P2-A --L brought about only slight enhancement in the titer of neutralizing antibodies, as compared to the immunization with P2-A --L in saline. The best results were achieved when the MDP was chemically conjugated to P2-A --L. This completely synthetic material, when administered in aqueous solution, yielded highly inactivating antiserum with a titer similar to that obtained with complete Freund's adjuvant in the absence of MDP. MDP-P2-A --L elicited also a humoral immune response to MDP, but with much lower titer than that induced by complete Freund's adjuvant containing PrA --L only. It was also observed that the capacity of MDP-P2-A --L to increase resistance against infection was more than a 100-fold greater than that of unconjugated MDP. In the last few years progress has been made, and new approaches have been employed, in the field of vaccine preparation. This included the introduction of the concept of genetic engineering for production of viral components (1), in parallel with the chemical synthesis of viral fragments (2), for the purpose of replacing vaccines now used. If found successful, these approaches might show several advantages. (i) The fragments should contain only the unique antigenic determinant(s) required for eliciting neutralizing antibodies, thus eliminating undesired side effects caused by the presence of contaminating components or irrelevant determinants. (ii) The carrier to be used in a synthetic material could be chosen according to the genetic background of the immunized individual, taking advantage of the recent knowledge about the often-occurring correlations between an efficient immune response and the type of histocompatibility antigens of the host (3, 4). (iii) In a synthetic antigen the problem of adjuvanticity and choice of the desirable adjuvant might be solved by introduction into the macromolecule of groups to enhance immunogenicity.A prerequisite for this approach is the feasibility of synthesis of antigens that contain immunoreactive region(s) of protein molecules, including viral proteins, that will induce immune response toward the intact protein. Indeed, during the last few years this has been demonstrated for several proteins. For example, antibodies provoked by a synthetic peptide comprising the "loop" region of the enzyme lysozyme attached to a synthetic carrier were reactive with native lysozyme (5). Similarly, anti...

Immunological castration of male mice by a totally synthetic vaccine administered in saline.

“…We have shown (29,30) that, under certain conditions, synthetic haptens and the synthetic adjuvant MDP could be usefully coupled to a polymeric carrier. More recently, we have shown that active immunization could be obtained by a totally synthetic bacterial vaccine (22).…”

Prediction of protein antigenic determinants from amino acid sequences.

“…However, once an antigenic determinant has been predicted, it should be possible to verify its existence by synthesizing the indicated region chemically and testing its activity in an appropriate immune assay, such as inhibition of cytotoxicity or precipitation inhibition. Furthermore, it should be possible to raise antisera against such synthetic determinants, as Arnon et al have done for a bacteriophage (37). Ultimately, predicted antigenic determinants from proteins of pathogenic organisms might be useful in the production of synthetic vaccines.…”

A Peripatetic And Personal View Of Molecular Immunology For One Third Of The Century

“…When the muramyl dipeptide was bound covalently, it was much more efficient than when it was first mixed with the antigen. We prepared, with Ruth Arnon, such totally synthetic antigens, and these led to neutralization of a virus, MS2 (22), as well as to protection against diphtheria and cholera. Ruth Arnon also did it fo r influenza.…”