Functional Antibody Activity Elicited by Fractional Doses ofHaemophilus influenzaeType b Conjugate Vaccine (Polyribosylribitol Phosphate–Tetanus Toxoid Conjugate)

Abstract

. Sixty serum samples, collected at age 7 months, with >2.0 g of anti-PRP IgG per ml were randomly selected for avidity determinations. Geometric mean IgG concentrations were 13, 14, and 17 g/ml for infants who received the full-dose (n ‫؍‬ 19), one-half-dose (n ‫؍‬ 19), and one-third-dose (n ‫؍‬ 22) regimens, respectively. SBA geometric mean titers (1/dilution) were 85.0, 82.0, and 76.1 in sera from infants receiving the full-, one-half-, and one-third-dose regimens, respectively. Avidity indices (mean ؎ standard error weighted average of NaSCN molar concentration ؋ serum dilution factor) were 71.9 ؎ 9.4, 123.6 ؎ 26.8, and 150.9 ؎ 24.9 for the full-, one-half-, and one-third-dose regimens, respectively. Upon comparison, the only significant difference (P ‫؍‬ 0.024) found was a greater avidity index for sera from infants receiving the one-third-dose regimen than for sera from infants receiving the the full-dose regimen. We conclude that fractional doses elicit similar functional antibody activities in infants with >2 g of anti-PRP IgG per ml, corresponding to 89, 90, and 97% of infants receiving three doses of either the full concentration or one-half or one-third of the labeled concentration, respectively. This approach offers an alternative strategy for the prevention of H. influenzae type b disease in countries with limited resources.

Immunologic Response toHaemophilus influenzaeType b (Hib) Conjugate Vaccine and Risk Factors for Carriage among Hib Carriers and Noncarriers in Southwestern Alaska

“…IgG and IgM antibody concentrations were determined by an enzyme-linked immunosorbent assay (ELISA) modification (12) of the method published by Madore et al (21). The minimum level of detection of the semiautomated ELISA was estimated to be 0.11 g/ml at a 1:45 serum dilution, which is similar to those previously reported (29). IgM concentration was determined only at the baseline assessment.…”

Risk of Invasive Haemophilus influenzae Type b (Hib) Disease in Adults with Secondary Immunodeficiency in the Post-Hib Vaccine Era

“…Antibodies detected by ELISA may have different functional capabilities due to their specific chemical and genetic characteristics. To assess the functional activity of the anti-PRP antibody, we employed a serum bactericidal assay, which measures the killing of bacteria by anti-Hib specific antibody mediated by the complement activation (37). Among healthy controls, 56% of serum samples were able to kill Ͼ50% of Hib bacteria in the presence of baby rabbit complement in contrast to only 30% of sera from myeloma patients (P ϭ 0.032) ( Table 2).…”

“…Bacteria were grown on brain heart infusion agar supplemented with 10 g/ml hemin chloride (factor X) and 1 g/ml NAD (factor V) in a humidified incubator at 37°C and 5% CO 2 overnight. The SBA was essentially performed as previously described (10,37). Briefly, Hib was cultured, harvested, and diluted to a concentration of approximately 10 4 CFU/ml in SBA buffer, which consisted of Hank's buffered salt solution supplemented with 10 g/ml factor X and 1 g/ml factor V. Serum samples were incubated in a water bath at 56°C for 30 min to inactivate complement and serially diluted 2-fold 11 times beginning at a ratio of 1:8.…”

Comparison of Antibody Repertoires against Staphylococcus aureus in Healthy Individuals and in Acutely Infected Patients

“…Avidity measurements were performed by including Na-isothiocyanate (in 1, 2, 3, or 4 M final concentrations) during the incubation of the antigens with serum samples in the 1,000-to 25,000ϫ dilution range according to the method of Romero-Steiner et al (46). Serum IgG and IgA concentrations were determined by ELISA.…”