Antigenicity of purified glutaraldehyde-treated cholera toxoid administered orally

Abstract

The antigenicity of orally administered glutaraldehyde-treated cholera toxoid was investigated in healthy volunteers. Fourteen volunteers ingested two or three 2-mg doses of toxoid with saline, with the doses spaced at 28-day intervals. Thirteen other volunteers received comparable toxoid doses with NaHCO3 and milk to neutralize gastric acid. Increments in circulating antitoxin levels were used to assay the antigenicity of oral toxoid. Antitoxin was measured by adrenal cell, rabbit skin permeability factor, and passive hemagglutination assays in sera collected on days 0, 28, 35, 56, 63, and 84 after primary immunization. Adrenal cell and rabbit skin assays exhibited identical sensitivity in detecting antitoxin rises in the 27 vaccinees (19/27) and were significantly more sensitive than passive hemagglutination (11/27) (P less than 0.03). Volunteers who ingested toxoid with NaHCO3 and milk had a higher rate of seroconversion (77%) than those who received toxoid with saline (64%); they also had earlier rises in antitoxin titer and consistently higher geometric mean titers on all days tested. These studies demonstrate that purified cholera toxoid is antigenic in humans after oral administration. The possible role of oral toxoid in enhancing the protective effect of killed whole-cell vaccines can now be investigated.

Microtiter enzyme-linked immunosorbent assay for immunoglobulin G cholera antitoxin in humans: method and correlation with rabbit skin vascular permeability factor technique

“…Sera were collected from 49 volunteers who were challenged with the classical biotype of V. cholerae, and from 43 volunteers who were challenged with the El Tor biotype of V. cholerae, as a part of studies designed to assess the protective value of cholera vaccines. All challenge studies were carried out under quarantine in the Isolation Ward of the Center for Vaccine Development (16,17). Sera were obtained before and 10, 21, and 28 days after challenge.…”

“…The diarrhea-producing enterotoxin of Vibrio cholerae is immunogenic, and the majority of individuals with clinical or subclinical V. cholerae infection develop significant rises in circulating antitoxin (1,2,10,17,19). Current assays for cholera antitoxin include the rabbit skin vascular permeability factor (PF) assay (5,16), Y-1 adrenal cell assay (7,16), rabbit ileal loop assay (6,19), radioimmunoassay (11,13), and passive hemagglutination test (10,14). Each suffers from one or more of the following drawbacks: not readily adaptable to large numbers of specimens; expensive; requires sophisticated tissue culture capability or radioisotopes; does not measure specific immunoglobulin class; requires relatively large volumes of serum.…”

Immunity to Enterotoxigenic Escherichia coli

“…Antitoxin to E. coli LT was assayed by a microtiter adrenal cell neutralization technique (7,41). The reproducibility of this assay for E. coli LT antitoxin is comparable to our adrenal cell assay for measurement of cholera antitoxin (29). Filtered and lyophilized toxin from E. coli 408-3 (lot no.…”

Properties of cross-linked toxoid vaccines made with hyperantigenic forms of synthetic Escherichia coli heat-stable toxin

“…Klipstein and R. F. Engert, unpublished observations). (iii) Unlike carbodiimide, there is a considerable body of experience that attests to the safety of administering GA conjugates to humans (8,26,31). GA toxoids lost favor a decade ago when immunization with GA-treated cholera toxoid provided disappointing results in humans (27,30); however, methods such as ELISA were not then available to determine the actual antigenicity of these toxoids, so that immunization dosages were unknown in terms of the number of cholera AU given.…”