Kinetics and sensitivity of ELISA IgG pertussis antitoxin after infection and vaccination with Bordetella pertussis in young children

Abstract

Sera from 96 young children in a vaccine trial were analysed for kinetics of ELISA IgG anti-pertussis toxin (anti-PT) after a laboratory-verified pertussis infection. The antibody decay curves after infection were biphasic and similar in shape to those after vaccination. The change from a rapid to a slower decay after the peak occurred about 4-5 months from the first day of cough. In a group of children given a two- or a five-component acellular pertussis vaccine the proportion of sera above the tentative cut-off values for anti-PT of 20, 50 or 100 EU/ml 12 months after onset of the infection were 19%, 0% and 0% respectively. Corresponding figures for a whole-cell or placebo vaccine group of infected children were significantly higher, 73%, 39% and 30%, i.e. the antibody decay after infection in young children depends on vaccination status as well as on the pertussis vaccine given. In a large group of non-infected children vaccinated with the same five-component acellular vaccine 13%, 0% and 0% had sera above 20, 50 and 100 EU/ml at 12 months after the third vaccine dose and all were below the minimum level of detection 2 years after vaccination. In conclusion, knowledge about anti-PT kinetics is essential for the interpretation of seroepidemiological data but hardly offers the possibility to establish valid cut-off values for anti-PT in single sample serology. An option would be to identify a grey zone between the positive and negative ends of the distribution for follow-up testing by a second serum.

Prospective Evaluation of an Australian Pertussis Toxin IgG and IgA Enzyme Immunoassay

“…In contrast to the case for anti-PT IgA, we found no significant age-related differences in seroconversion of anti-PT IgG. Since repeat serum collections were not performed at fixed time intervals, the time to seropositivity represents the maximum time interval to seroconversion, but the data are consistent with previous literature describing the longitudinal dynamics of anti-PT IgG measurement following infection (5,10,21).…”

“…Kaplan-Meier (KM) analysis was used to determine median times to seropositivity/seronegativity, and stratum-specific outcomes were compared using log rank statistics. Kinetics of anti-PT IgG and anti-PT IgA postinfection in PCR-positive patients were analyzed on a per-sample basis, using median antibody values at different time intervals per the methods of Hallander and colleagues (10). The sensitivity and specificity of anti-PT IgG and anti-PT IgA EIAs were calculated from 2 ϫ 2 contingency tables for a range of possible cutoff values and plotted as receiver operating characteristic (ROC) curves.…”

Duration of Protection After First Dose of Acellular Pertussis Vaccine in Infants

“…10 Second, it is consistent with antibody persistence data showing that pertussis toxin immunoglobulin G antibody decreases to close to baseline levels by 18 months after the last dose at 6 months. 33,34 Third, Australian population-based seroepidemiologic data have demonstrated similar findings, with a significant increase in the prevalence of undetectable pertussis toxin immunoglobulin G antibody 3 years after discontinuation of the 18-month booster. 35 …”

Laboratory Diagnosis of Pertussis

“…High levels of IgG-Ptx antibodies induced by infection start to decrease again within a few months, in a biphasic manner, initially quickly and later, gradually, more slowly (196,242,245,247,248). The decline of IgG-Ptx is faster than that of other antibodies induced by infection with B. pertussis (182,202,211).…”