We would like to respond to the letter by Zhang and others regarding our study published in the American Journal of Tropical Medicine and Hygiene.1 Our serum samples were all stored in annually calibrated –80°C freezers. The samples were only thawed once. In general, antibodies are known to remain stable in frozen storage over lengthy periods. There are numerous publications regarding antibody stability during storage,2–6 and we believe that all antibodies, including antibodies against Zika virus, will remain stable during storage.
Our study also re-assayed the presence of anti-dengue IgG antibodies in the samples. In our previous study,7 we measured dengue IgG antibody using indirect ELISA, and in the current study1 we tested for antibodies in the same samples using a plaque reduction neutralization test. Overall good concordance of results between the two methods was observed (not shown), supporting the stability of antibodies in our samples.
The characterization of anti-Zika virus antibody stability during storage may be useful, but this was not the focus of our study.
Sasmono RT et al., 2021. Spatiotemporal heterogeneity of Zika virus transmission in Indonesia: serosurveillance data from a pediatric population. Am J Trop Med Hyg 104: 2220–2223.
Castejon MJ, Yamashiro R, de Oliveira CC, Oliveira CFA, Ueda M, 2014. Stability of anti-HIV antibodies in serum samples stored for two to eighteen years periods. J Bras Patol Med Lab 50: 272–277.
Woodrum D, French C, Shamel LB, 1996. Stability of free prostate-specific antigen in serum samples under a variety of sample collection and sample storage conditions. Urology 48: 33–39.
Han Q, Li S, Fu B, Liu D, Wu M, Yang X, Cai G, Liu Z, Chen X, Zhu H, 2018. Stability of important antibodies for kidney disease: pre-analytic methodological considerations. PeerJ 6: e5178.
Prayitno A et al., 2017. Dengue seroprevalence and force of primary infection in a representative population of urban dwelling Indonesian children. PLoS Negl Trop Dis 11: e0005621.