Stability of Zika Virus Antibodies in Specimens from a Retrospective Serological Study.

Dear Sir,

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 study[1] 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.