Background: Zika virus (ZIKV) was introduced in the Caribbean island of Curacao in January 2016. A commercially available ZIKV IgM and IgG ELISA was evaluated on patients that were PCR-positive for ZIKV.
Methods: ZIKV infection was established by PCR in urine samples. Samples from PCR-positive patients were selected for validation of a ZIKV NS1 IgG and IgM ELISA. Patients with a follow-up sample ≥ 2 weeks after initial presentation were used to assess the sensitivity of the assay. Samples of 15 historical controls with serological evidence of Dengue, Chikungunya or an unrelated viral infection were included to establish specificity and cross-reactivity.
Results: Fourteen patients with positive ZIKV PCR diagnosis had repeated serum samples drawn ≥ 2 weeks after the initial sample. The combined results of these repeated IgM and IgG tests resulted in a sensitivity of 92%. One pregnant female showed no presence of IgG or IgM in any of the two samples. Testing of the panel of historical ZIKV-negative controls resulted in a specificity of 100% in both the quantitative and semi-quantitative setting of the ELISA. One patient with known high-titers of antibodies against Chikungunya virus in the respective panel displayed borderline reactive results for ZIKV IgG in both quantitative and semi-quantitative setting of the assay.
In this PCR-positive ZIKV cohort of patients, the newly available ZIKV NS1
ELISA displayed excellent performance characteristics. Cross-reactivity was indicated
for Chikungunya in one case. No cross-reactivity was found for Dengue virus
infection. One pregnant female showed no signs of developing anti-ZIKV IgM or IgG
in this study. In the light of intrauterine pathogenesis, the lack of
development of maternal IgG during ZIKV infection is a concern.
Figure 1. Plot of anti-ZIKV IgG levels in distinct groups of patients. Left (diamonds) are ZIKV-negative historic controls. Right (connected circles) are ZIKV PCR-positive patients tested on separate times. One patient has a concentration above 400 RU/ml in the second sample. The single PCR positive patient who remains below the cutoff is a pregnant female.
L. Joseph, None
C. Roggeveen, None
R. Steingrover, None