Two-year Decay of Zika Virus Neutralizing Antibodies in People Living in an Endemic Region in Brazil

Abstract

It is currently not clear whether humoral immunity to Zika virus (ZIKV) elicited upon natural ZIKV infection is long-lasting. In addition, cross-reactivity of anti-ZIKV antibodies with antigenically related dengue viruses (DENV) may have biological implications in nonnaive individuals who subsequently acquire a heterotypic infection. Cross-reactive humoral immunity between ZIKV and DENV also complicates the interpretation of serological tests to evaluate previous exposure to either virus. Here, we have measured the 2-year decay of ZIKV neutralizing antibodies in people living in a ZIKV/DENV endemic area in Brazil who were identified as having an acute infection (group 1) or past (but recent) infection (group 2) with ZIKV in 2015-16. The titers of neutralizing antibodies to ZIKV decreased 9.1 and 2.3 times in groups 1 and 2, respectively. We also show that the plaque reduction neutralization assay (PRNT) is a reliable method to measure past exposure to ZIKV in coendemic areas.

Figure 1.

Zika virus (ZIKV) neutralizing antibody titers in 2015–16 and 2017 from acutely infected participants or those with a past/recent ZIKV infection in 2015–16. Titers are shown as the reciprocal dilution of serum (log₁₀-transformed) inhibiting 50% of ZIKV plaque formation (PRNT₅₀). (A) Titers from adults (≥ 18 years of age) acutely infected with ZIKV in 2015–16. (B) Titers from adults who had a past/recent ZIKV infection in 2015–16. (C) Titers from adolescents/children (≤ 16 years of age) who had a past/recent ZIKV infection in 2015–16. Lines going through the Y axis represent three cutoff values (≥ 2 log₁₀ or ≥ 100 [solid], ≥ 1.8 log₁₀ or ≥ 80 [dashed] and ≥ 1.3 log₁₀ or ≥ 20 [dotted]). Asterisks represent the significance (P value) of PRNT₅₀ titer difference between the two time points, calculated through paired t tests in GraphPad Prism 9.3.1. ****P < 0.0001. ***P = 0.0004. ns = nonsignificant or > 0.05.