Microsphere-Based IgM and IgG Avidity Assays for Human Parvovirus B19, Human Cytomegalovirus, and Toxoplasma gondii

Human parvovirus B19 (here B19), human cytomegalovirus (HCMV), and Toxoplasma gondii infections during pregnancy can lead to severe complications. While traditional diagnosis of infections is mostly confined to one pathogen at a time, a multiplex array is a feasible alternative to improve diagnostic management and cost-efficiency. In the present study, for these three pathogens, we developed microsphere-based suspension immunoassays (SIAs) in multiplex and monoplex formats for the detection of antimicrobial IgM antibodies as well as corresponding chaotrope-based IgG avidity SIAs. We determined the diagnostic performances of the SIAs versus in-house and commercial reference assays using a panel of 318 serum samples from well-characterized clinical cohorts. All the newly developed assays exhibited excellent performance compared to the corresponding high-quality reference methods. The positive and negative percent agreements of the IgM SIAs in comparison with reference methods were 95 to 100% and 98 to 100%, and those of the IgG avidity SIAs were 92 to 100% and 95 to 100%, respectively. Kappa efficiency values between the SIAs and the corresponding reference assays were 0.91 to 1. Furthermore, with another panel comprising 391 clinical samples from individuals with primary infection by B19, HCMV, or T. gondii, the IgM SIAs were highly sensitive for the detection of acute infections, and the IgG avidity SIAs were highly specific for the separation of primary infections from past immunity. Altogether, the strategy of IgM multiplex screening followed by IgG avidity reflex testing can provide high-throughput and accurate means for the detection and stage determination of B19, HCMV, and T. gondii infections. IMPORTANCE Human parvovirus B19, human cytomegalovirus, and Toxoplasma gondii are ubiquitous pathogens. Their infections are often asymptomatic or mild in the general population yet may be transmitted from mother to fetus during pregnancy. Maternal infections by these pathogens can cause severe complications to the fetus or congenital abnormalities. As a rule, the risk of maternal transmission is critically related to the infection time; hence, it is important to determine when a pregnant woman has acquired the infection. In this study, we developed new diagnostic approaches for the timing of infections by three pathogens. All the new assays appeared to be highly sensitive and specific, providing powerful tools for medical diagnosis.