No abstract

No abstract

No abstract

No abstract

No abstract

Homocysteine thiolactone (2) derivatives in which the nitrogen is acylated with groups containing acidic functionalities have been synthesized. These include the succinyl (3), the carboxymethylglutaryl (4), the 3-phosphonopropionyl (7), and the 3-sulfopropionyl (8) derivatives. These thiolactones can be used to introduce a thiol functionality into proteins such as the outer membrane protein complex of Neisseria meningitidis (OMPC) allowing conjugation with electrophilic ligands. This chemistry is the same as with N-acetylhomocysteine thiolactone (1), but their pKa values are such that at pH 7 concomitant negative charge is introduced into the conjugate. Such negative charge should neutralize some excess positive charge introduced when arginine- and lysine-rich peptides are bonded as ligands. In the case of OMPC, introduction of such positive charge appears to effect irreversible precipitation. The system has been studied using the maleimidopropionyl and bromoacetyltriarginine (9 and 10) derivatives as models. In select instances anionic spacers reduce the degree of precipitation relative to N-acetyl-homocysteine thiolactone derivatives.

In an effort to prepare pneumococcal (Pn) capsular polysaccharide (Ps) vaccines that would be immunogenic in infants, covalent conjugates were prepared for Pn types 6B, 14, 19F, and 23F. Each Ps type was covalently bound to an outer membrane protein complex from Neisseria meningitidis serogroup B and evaluated for immunogenicity in mice and infant monkeys. The conjugates induced specific anti-Ps antibody responses in mice and in infant rhesus and African green monkeys; a coniugate of 6B and outer membrane protein complex was immunogenic at Ps doses as low as 20 ng. Although low levels of the Pn group-common cell wall polysaccharide were present in all type-specific Ps preparations, anti-cell wall polysaccharide responses induced by covalent conjugates were < 1% of the total anti-Ps response after two doses of vaccine. In contrast, the anti-cell wall polysaccharide response of a noncovalent conjugate represented 41% of the anti-Ps response after two doses. Relative T-cell dependence, a requirement for the human target population of infants less than 18 months old, was demonstrated for all four Pn Ps con,jugates in an athymic mouse model. Therefore, these Pn Ps-outer membrane protein complex conjugate vaccines are excellent candidates for evaluation in human infants.

A method for toxoid preparation has been developed in which toxins expressing enzymatic activity can be detoxified by photoaffinity labeling techniques. In the case of Pseudomonas aeruginosa exotoxin A, the method relies on the affinity of azido-substituted analogs of the substrate (NAD) for the proenzyme form of the toxin. Photolysis of the putative toxin-analog complex results in irreversible inactivation of the toxin without loss of antigenic character. It is proposed that this occurs by nitrene insertion into a chemical bond on the toxin molecule. This affinity photoinactivation process should be applicable to other ADP-ribosylating toxins.The use of toxoids has been the basis for vaccination against toxin-mediated diseases for many years (1). 2870The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.