Abstract
Abrin, a toxin isolated from the seeds of Abrus precatorius (jequirity pea) is considered a biological threat agent by the Center for Disease Control and Prevention. To date, there is no effective postexposure treatment for abrin poisoning, and efforts are being made to develop an efficient vaccine and measures for postexposure therapy. Epitope mapping is widely applied as an efficient tool for discovering the antigenic moieties of toxins, thus providing invaluable information needed for the development of vaccines and therapies. Aiming to identify the immunodominant epitopes of abrin, several neutralizing antiabrin polyclonal antibodies were screened using a set of 15-mer peptides spanning the amino acid sequence of either the A or B subunits of abrin. Analysis of the antibody-binding pattern revealed 11 linear epitopes for the A subunit and 14 epitopes for the B subunit that are located on the surface of the toxin and thus accessible for antibody interactions. Moreover, the spatial location of several of these epitopes suggests they may block the galactose-binding pockets or the catalytic domain, thus neutralizing the toxin. These findings provide useful information and suggest a possible strategy for the development and design of an improved abrin-based vaccine and therapeutic antibodies.
Highlights
A toxin isolated from the seeds of Abrus precatorius, belongs to the family of Type 2 ribosome inactivating glycoproteins (RIP) [1]
We analyzed the binding properties of several polyclonal antiabrin-antibody preparations. These included ascitic fluid derived from mice immunized with purified abrin adsorbed on alum hydroxide (M1) and hyperimmune serum from rabbits immunized with abrin with Freund’s adjuvant (R1), abrin adsorbed on alum hydroxide (R2), or abrin adsorbed on alum hydroxide, followed by Freund’s incomplete adjuvant (R3)
Follow that differences between B:N ratios reflect differences in the fraction of antisugar antibodies in various antiabrin preparations, an issue that we intend to assess in the future. These results indicate that antiabrin preparations represent diverse sets of antibodies and are suitable for fingerprinting the immunodominant epitopes of abrin
Summary
A toxin isolated from the seeds of Abrus precatorius (jequirity pea), belongs to the family of Type 2 ribosome inactivating glycoproteins (RIP) [1]. Abrin consists of two subunits, the enzymatic A-chain (ATA) that depurinates a specific adenine residue of the 28S ribosomal RNA of the 60S subunit, thereby arresting protein synthesis; and the B-chain (ATB), a lectin that binds galactose residues at the cell surface, thereby mediating toxin internalization into the cells [2,3]. Abrin and ricin toxin share a marked homology in their sequence (42% for their A-chain and 59% for the B-chain) [6], and there is well-established body of knowledge on the immunodominant epitopes of ricin. Only two neutralizing epitopes of antiabrin monoclonal antibodies were identified, both located on the surface of ATA [8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
