Usefulness of receptor binding domain protein-based serodiagnosis of COVID-19.

Objectives: This study evaluated the performance of recombinant receptor binding domain (RBD) protein-based enzyme-linked immunosorbent assays (RBD-ELISAs) for detecting anti-SARS-CoV-2 immunoglobulin (Ig) G and IgM antibodies. Methods: In this study, 705 sera from SARS-CoV-2-infected individuals and 315 sera from healthy individuals were analyzed. Results: The RBD-ELISA IgG exhibited high specificity (99.1%) and moderate sensitivity (48.0%), with an overall diagnostic accuracy of 73.5%. RBD-ELISA IgM demonstrated specificity at 94.6% and sensitivity at 51.1%, with an accuracy of 72.8%. Both assays displayed improved performance when analyzing samples collected 15-21 days post-symptom onset, achieving sensitivity and accuracy exceeding 88% and 90%, respectively. Combining RBD-ELISA IgG and IgM in parallel analysis enhanced sensitivity to 98.6% and accuracy to 96.2%. Comparing these RBD-ELISAs with commercially available tests, the study found overlapping sensitivity and similar specificity values. Notably, the combined RBD-ELISA IgG and IgM showed superior performance. Cross-reactivity analysis revealed low false-positive rates (4.4% for IgG, 3.7% for IgM), primarily with viral infections. Conclusion: This research underscores the potential of RBD-based ELISAs for COVID-19 diagnosis, especially when assessing samples collected 15-21 days post-symptom onset and utilizing a parallel testing approach. The RBD protein's immunogenicity and specificity make it a valuable tool for serodiagnosis, offering an alternative to polymerase chain reaction-based methods, particularly in resource-limited settings.

Maternal and congenital infections arising from Zika, dengue and Chikungunya arboviruses in Salvador, Brazil.

BACKGROUND: Salvador was one of the Brazilian cities most affected during the 2015 Zika virus (ZIKV) outbreak. METHODS: A cross-sectional study was performed with enrolment of parturients and their newborns. RESULTS: Positive IgM antibodies for ZIKV, dengue (DENV) and Chikungunya (CHIKV) were present in 6.9, 11.9 and 22.8% of the parturients, and IgG antibodies were detected in 72.3, 92.3 and 38.6%, respectively. No cases of DENV congenital infection were identified. ZIKV and CHIKV congenital infections were observed in 16.5 and 13% of newborns, respectively. CONCLUSIONS: High exposure rates to the three arboviruses and the identification of newborns with ZIKV and CHIKV congenital infections reinforces the necessity of ZIKV and CHIKV prenatal and neonatal screening in endemic regions.

Association between seroprevalence of IgG anti-Toxoplasma gondii and risk factors for infection among pregnant women in Climério de Oliveira Maternity, Salvador, Bahia, Brazil.

Maternal Toxoplasma gondii (T. gondii) infection can lead to spontaneous abortion, fetal malformation, and numerous sequelae in the newborn, including visual and hearing impairment. T. gondii serology was determined in pregnant women and their newborns who were referred to Climério de Oliveira Maternity, Federal University of Bahia, and the possible associations with the risk factors for maternal infection were investigated. This cross-sectional study was conducted from January to December 2014 and included 712 pregnant women, aged 15 to 49 years, and 235 newborns. Seroprevalence was determined by the detection of T. gondii-specific immunoglobulin (Ig) M (IgM) and IgG antibodies using enzyme-linked immunoassay. In addition, mothers completed a questionnaire that focused on socioeconomic aspects, and survey data were tabulated using the SPSS statistical software program (version 21.0 for Windows). The seroprevalence rate for specific IgG antibodies was 51% (362) among mothers and 93% (219) among neonates. All the mothers and their newborns were negative for specific-IgM antibodies. Higher age group and lower maternal education were the only risk factors statistically associated with the presence of specific IgG. In summary, high levels of specific IgG antibodies were observed in pregnant women. The knowledge of risk factors for toxoplasmosis can help in the orientation of newly pregnant women.