Delayed maturation of immunoglobulin G avidity: implication for the diagnosis of toxoplasmosis in pregnant women

Abstract

The low avidity of immunoglobulin G has been reported to be a useful marker of recent infection with Toxoplasma. Several investigators, however, have published discrepant result on the maturation of avidity over time. The aim of this study was to analyse persistent low avidity of immunoglobulin G in immunocompetent individuals and in pregnant women and how it could interfere in the flowchart of antenatal diagnosis of toxoplasmosis in the latter group. An international literature search was conducted together with a retrospective study of a hospital database. Eleven publications that met the inclusion criteria reported delayed maturation of avidity at a frequency ranging from 0 to 66.6% of the patients. Examination of those publications demonstrated an important heterogeneity in the type of assay used, the calculation of avidity, the cutoff above which avidity was considered to be elevated, and the delay since infection after which indices are expected to be high. In the hospital database, persistent low avidity was found even after a median follow-up period of 6 years. Different factors could interfere with maturation of avidity, such as variations between individuals, the assay system used, and, possibly, the treatment administered. The results of this study clearly demonstrate that, in a pregnant woman, an acute infection cannot be reliably diagnosed solely on the basis of low avidity of immunoglobulin G. Further investigations and standardization of assays are urgently needed. Estimation of the time of infection remains difficult, especially in cases in which the samples are drawn late in pregnancy; the final estimate must be based on several tests repeated at intervals of weeks.

Toxoplasma Seroconversion with Negative or Transient Immunoglobulin M in Pregnant Women: Myth or Reality? A French Multicenter Retrospective Study

“…Consequently, serological tests other than those for IgG and IgM detection have been developed to facilitate the diagnosis of seroconversion. The measurement of IgG avidity was developed almost 20 years ago to exclude any infection acquired in the preceding 3 or 4 months using most commercial tests (16,17,18,19,20,21,22,23,24). Immunoblot analysis (Toxo II IgG test; LDBio, Lyon, France) may promptly confirm the seroconversion when IgG concentrations detected with routine tests are negative or equivocal (25,26,27).…”

Spiramycin Treatment of Toxoplasma gondii Infection in Pregnant Women Impairs the Production and the Avidity Maturation of T. gondii -Specific Immunoglobulin G Antibodies

“…One problem with different findings in different studies is the lack of standardization of the T. gondii-specific IgG AI assay (12).…”

Serology using rROP2 antigen in the diagnostic of toxoplasmosis in pregnant women

“…This is the main effect in avidity evolution, as the selection of high avidity B cell clones is dependent on antigen prevalence and the numbers of clones initially produced (TARLINGTON, 2008). Conflicting reports on avidity evolution in human toxoplasmosis has been attributed both to individual variations and to therapy (LEFEVRE-PETTAZZONI et al, 2006). Diagnosis of recent T. gondii infection in pregnant women remains a difficult task despite scientific efforts to solve this problem.…”