Immunoturbidimetric assay of beta 2 microglobulin using latex particles in microplates.

A latex particle immunoturbidimetric assay in microplates has been developed for the quantitation of beta 2 microglobulin. The assay which involves three pipetting steps and one incubation, has a clinically useful range of 0.4-16 mg/l. A comparison of the method with a commercial radioimmunoassay in the analysis of 125 sera revealed a high degree of correlation. Although the assay was performed manually, it showed considerable potential for full automation.

A quantitative C-reactive protein assay using latex agglutination in microtiter plates.

In this quantitative assay, latex particles coated with anti-C-reactive protein (CRP) are agglutinated by CRP following vortex agitation in microtiter plates. A decrease in absorbance at 405 nm is directly proportional to CRP concentration. This 30 min assay is simple and necessitates only two pipetting steps after serum dilution. The linear part of the standard curve ranges from 5 to 150 mg/l and CRP concentrations up to 300 mg/l can be determined without additional dilution of sera. Within-assay reproducibility varies from 4.4% to 7.5% while between-assay reproducibility ranges from 9.3% to 12.2%. Correlation studies performed with 104 sera assayed by automated nephelometer and turbidimeter gave correlation coefficients of 0.96 and 0.97 respectively.

[Brucella vaccination in professionally exposed subjects. Prospective study]. / Vaccination brucellique en milieu professionnel exposé. Etude prospective.

This prospective phase IV study on cohort concerns a vaccine made of the phenol-insoluble fraction of Brucella abortus biotype 1 (B19 strain). Three hundred and three professionally exposed subjects entered the study; 161 out of 182 subjects (88.5 percent) with negative response to an intradermal test for detection of previous contamination accepted to be vaccinated. Booster injections were given 18 and 36 months after vaccination. Local pain was observed after 45.2 percent of injections and moderate systemic reactions after 5 percent of injections. Seropositivity after primary vaccination reached 80 percent. The booster injection, justified by a major decrease of this rate after 18 months, gave exactly the same response of the thymo-independent type. This vaccinal schedule did not result in detectable hypersensitivity. The clinical effectiveness of the vaccine could not be evaluated accurately because of the insufficient number of subjects. The possibility of subclinical infection in vaccinated subjects calls for wider comparative studies of vaccinated versus non-vaccinated subjects.

Immune responses elicited by a fourth dose of the HPV-16/18 AS04-adjuvanted vaccine in previously vaccinated adult women.

BACKGROUND: Vaccines are now available for the prevention of HPV-16/18-related cervical infections and pre-cancers, primarily targeting adolescent girls. Since the risk of HPV exposure potentially persists throughout a woman's sexual life, vaccine-derived immunity should be long-term. The current study, HPV-024 (NCT00546078, http://clinicaltrials.gov), assessed the immune memory in North American women who received three doses of HPV-16/18 AS04-adjuvanted vaccine 7 years earlier in HPV-001 (NCT00689741). METHODS: Women vaccinated in HPV-001 received a 4th-dose of the HPV-16/18 vaccine (024-4DV group, N=65). Post 4th-dose immune responses were compared with post 1st-dose immune responses in cross-vaccination controls (024-3DV group, N=50). Reactogenicity was compared between the 4th-dose and the 1st-dose administration. RESULTS: Pre 4th-dose, 100% of subjects in the 024-4DV group remained seropositive for anti-HPV-16/18 antibodies (ELISA). Compared to pre 4th-dose, GMTs for anti-HPV-16 and anti-HPV-18 antibodies were respectively 9.3-fold and 8.7-fold higher at day 7, and 22.7-fold and 17.2-fold higher at month 1. Compared to post 1st-dose, GMTs for anti-HPV-16 and anti-HPV-18 were respectively 80.5-fold and 205.4-fold higher at day 7, and 11.8-fold and 20.5-fold higher at month 1. Furthermore, 68.2% and 77.3% of women had HPV-16/18 specific memory B-cells, respectively, pre 4th-dose, rising to 100% one month post 4th-dose vaccination. The 4th-dose was generally well tolerated. CONCLUSION: A 4th-dose of HPV-16/18 AS04-adjuvanted vaccine triggered a rapid and strong anamnestic response in previously vaccinated women, demonstrating vaccine-induced immune memory.

Immunoassay by particle counting for coagulation testing: application to the determination of protein C.

Latex particles coated with F(ab)'2 fragments of anti-protein C IgG antibodies are agglutinated by protein C, and the quantity of particles agglutinated is proportional to the concentration of protein C. The reaction can be quantitated by optical particle counting. Based on this system, we designed an immunoassay for protein C. Precision measured at low, medium and high levels of protein C varied from 3.3% to 13.7%. Specificity was evaluated by dilution recovery. A correlation coefficient of r = 0.959 was found when the new method was compared with a chromogenic technique on 131 plasmas.

Immunoassay of theophylline by latex particle counting.

We set up an immunoassay by particle counting for theophylline. Theophylline concentration is assayed by its capacity to inhibit the agglutination of theophylline coated latex particles by a specific monoclonal antibody, the agglutination being enhanced by a rabbit anti-mouse IgG antiserum. The dose range is 2-64 mg/L. The cross-reactions observed with caffeine (0.3%), theobromine (0.2%), 3-methylxanthine (0.7%) and 8-chlorotheophylline (2%) are very good when compared with other published methods. Within and between-run precisions measured at low, medium and high level of the calibration curve show coefficients of variation ranging from 3.9% to 9.5%. Our assay was correlated with the Fluorescence Polarization Immunoassay (FPIA) and a correlation coefficient of 0.96 was determined for 89 samples.

[Brucellosis among occupationally exposed people: evaluation of immunological tests after vaccination]. / Brucellose en milieu professionnel exposé: évaluation des tests immunologiques après vaccination.

For the evaluation of immunological tests during an epidemiological survey and of vaccination with the PI brucellin vaccine, in an occupationally exposed environment, a sample group of 354 subjects was studied. The vaccinal strategy was based on the outcome of a skin test for hypersensitivity: the PS brucellin test. In this framework, the serological status and evolution of individuals with positive or negative reactions to this test were analysed. Sera were studied using the buffered antigen test, indirect fluorescence immunoassay and Wright's agglutination test, as well as by PACIA and ELISA techniques with assay of IgG, IgA and IgM antibodies. The PS test, which was pivotal in this study, was compared with the lymphoblastic transformation test. One prominent aspect of this evaluation was the establishment of conventional prognostic indices for the PS and serology. The PS is definitely shown to be a convenient, reliable tool for screening. Although it does not generate sensitivity it may modify the serological status of both positive and negative individuals.