Transplacental transfer of maternal binding and neutralizing antibodies against respiratory syncytial virus - An assay specific comparison.

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in young children. Maternal antibodies can protect infants against RSV in the first months of life. Assessing antibody transfer efficiency by comparing infant to maternal antibody titers (C/M) is important for determining timing for maternal vaccination.

METHODS

We used 5 IgG antibody enzyme immunoassays with the RSV F (Fwt) or prefusion-stabilized F (FPre) proteins, G (subgroup A (Ga) or B (Gb)) proteins, or RSV lysate antigens and 2 neutralization assays, one for each RSV subgroup, and compared C/M ratios across different assays. We tested 164 mother-child specimen pairs, including 124 preterm and 40 full-term infants.

RESULTS

Matched-pair analysis of all specimen pairs indicated that the median C/M ratio and interquartile range (IQR) for anti-Fwt (1.064; IQR 0.739, 1.555) and anti-Lysate (1.062, IQR 0.710, 1.519) antibodies were significantly higher (p < 0.001) than anti-Ga (1.009, IQR 0.585, 1.295), anti-Gb (0.977, IQR 0.607, 1.350) antibodies and higher than RSV-A (1.000, IQR 0.567, 1.437) and RSV-B (1.000, IQR 0.688, 1.437) neutralizing antibodies, and anti-FPre (1.023, IQR 0.635, 1.367) antibodies. Differences in transfer efficiencies between assays were affected by gestational age - preterm infants had higher C/M ratios for neutralizing compared to binding antibodies, while full-term infants had higher C/M ratios for binding than neutralizing antibodies.

CONCLUSION

There are assay differences in C/M ratios, and this study provides insights into the effect of assay choice on determining transfer patterns and guides selection of study assays and comparison of results among studies.