A primary infection with one dengue serotype elicits an immune response resulting in the development of specific antibodies. A secondary infection with a different dengue serotype tricks the immune system into developing a response -- the antibodies will attack the virus, but since they are serotype-specific, they do not inactivate the virus but rather help facilitate infection. This results in an acute infection due to antibody-dependent enhancement (ADE). Given the similarities between dengue virus and Zika virus, infection due to ADE is a concern.
On September 6th, 2016, we challenged three dengue-exposed Indian rhesus macaques with 10e4 PFU of the French Polynesian Zika virus isolate (ZIKV-013
). These dengue-exposed animals were previously challenged a year ago with 600,000 PFU of dengue serotype-3 (DENV-3).
We were able to run dengue PRNT assays on these dengue-exposed animals and comparison of DENV-3 PRNT titers with Zika PRNT titers shows that there is no cross-neutralization. Open bars are DENV-3 PRNT titers. Open circles are Zika PRNT titers.
As of 7 days post-infection, viral load kinetics appear consistent with typical Zika virus infection as observed in our previous challenge studies. Animal 850585 had a much higher peak than the other two animals, and as of days 6 and 7, viremia has leveled off instead of the typical decline. Animal 489988 had a negative viral load on day 7.
We will continue to monitor these animals weekly through 28dpi.