Zika Virus

Protocol suggestions for using the bridging method to improve assay sensitivity and specificity: • Conjugate the gold particle to the anti-Zika NS1 Ab (optimization of conjugation chemistry required). • Mix the recombinant Zika NS1 antigen and gold-conjugated anti-Zika NS1 Ab to form a complex. - The ratio of Zika NS1 and gold-conjugated anti-Zika NS1 Ab must be optimized for a particular assay. - Remove any unbound gold-conjugated anti-Zika NS1 (e.g. via centrifugation) prior to deposition on the conjugate pad.

Gold-conjugated MAb or PAb (e.g. PAb to Zika NS1)

- In order to reduce cross-reactivity with Dengue, include a recombinant Dengue NS1 antigen to conjugate mixture (inclusion of one serotype should be sufficient). Optimal dilution must be determined by the end user.

Antigen (e.g. Zika NS1)

Patient’s IgM to Zika

Anti-human IgM (capture antibody)

Model of the ZIKV NS1 hexamer

Zika NS1 shares a high structural similarity with other flavivirus NS1 proteins and NS1 is suspected to be a major genetic factor underlying the diverse clinical consequences of infections caused by flaviviruses. Zika NS1 displays characteristics that are unique among flaviviruses including a loop surface containing both a positively and negatively charged central region and a negative charge toward the two distal ends in its loop surface. This loop-surface interface is thought to play a crucial role in interactions of secreted NS1 hexamers with host factors and antibodies.

The ZIKV NS1 hexamer, modeled by using the full-length Dengue Type 2 NS1 structure. The actual NS1 172–352 structure is colored in orange, and the predicted NS1 1–171 structure is colored in light gray. NS1 172–352 is located in the outer layer of the hexamer barrel.

Song, H., Qi, J, Haywood, J., Shi, Y. and Gao, G.F. (2016). Zika virus NS1 structure reveals diversity of electrostatic surfaces among flaviviruses. Nature Structural & Molecular Biology . 23:456–458.

Fig. 1: Microcephaly: a neonatal malformation defined as a head size much smaller compared with other babies of the same age and sex.