Development and standardization of methods to evaluate the antibody response to an HIV-1 candidate vaccine in secretions and sera of seronegative vaccine recipients

Enzyme-Linked immunosorbent assays (ELISA) were developed to test, in serum and mucosal samples, total IgG, total IgA, serum albumin, and anti-gp120 M N and anti-p24 LAI IgG and IgA levels. These ELISAs were optimized accordin g to reagents and experimental conditions. Inter- and intra-assay coefficie nts of variation ranged from 3.3% to 18.6%. The ELISA results were linear a nd precise, and for anti-HIV-l IgG and IgA, the analytical recovery was clo se to 100%. For IgG and IgA titration against gp120 MN and p24 LAI, standar ds were made using pooled sera or gammaglobulins with assigned titres in EL ISA units per mi (EU/ml). These standards were used to obtain a linear regr ession curve that could then be used to obtain the titres of experimental s amples. The cut-offs for positivity were determined for sera and mucosal fl uid using healthy controls. Validation conditions were defined for ELISAs, and samples that did not satisfy these conditions were retested, Measuremen t of total IgG and IgA allowed normalization and comparison of the results of specific immunoglobulin levels between different samples. Serum albumin was tested as a marker of transudation from serum to mucosal fluid, allowin g calculation of the relative coefficient of excretion, which is one elemen t required to determine the origin of the immunoglobulin detected in mucosa l samples. These ELISAs were developed with samples from HIV-l-infected and healthy subjects. We now have the tools to study and understand mucosal im munity in seronegative subjects vaccinated with an HN-I candidate vaccine. (C) 1999 Elsevier Science B.V. All rights reserved.