Experimental Zika Virus Infection of Neotropical Primates

Abstract

The establishment of a sylvatic reservoir of Zika virus (ZIKV) in the Americas is dependent on the susceptibility of primates of sufficient population density, the duration and magnitude of viremia, and their exposure to the human mosquito-borne transmission cycle. To assess the susceptibility of squirrel (Saimiri sp.) and owl monkeys (Aotus sp.) to infection, we inoculated four animals of each species with ZIKV from the current epidemic. Viremia in the absence of detectible disease was observed in both species and seroconversion occurred by day 28. ZIKV was detected in the spleen of three owl monkeys: one at 7 days postinoculation (dpi) and two at 14 dpi. This study confirms the susceptibility to ZIKV infection of two Neotropical primate species that live in close proximity to humans in South America, suggesting that they could support a widespread sylvatic ZIKV cycle there. Collectively, establishment of a ZIKV sylvatic transmission cycle in South America would imperil eradication efforts and could provide a mechanism for continued exposure of humans to ZIKV infection and disease.

Figure 1.

Zika virus viral load (log₁₀ FFU/mL) data from squirrel monkey plasma, as determined by RT-PCR. This figure appears in color at www.ajtmh.org.

Figure 2.

Cytokine bead array analyses of plasma samples. In duplicate wells of the 96-well filter plate, 25 μL of plasma from nonpregnant, pregnant, and Zika virus (ZIKV)-exposed pregnant squirrel monkeys were incubated with 25 μL of cytokine-coupled beads overnight at 4°C followed by washing and staining with biotinylated detection antibody. The plates were read on Bio-Rad 200 using Luminex technology, and the results are expressed as picograms per milliliter concentration. The minimum detectable concentrations in picograms per milliliter for interferon (IFN)-γ (2.2), interleukin (IL)-2 (0.7), IL-4 (2.7), IL-6 (0.3), IL-10 (6.2), IL-13 (5.8), and IL-17A (1.3) are used for considering positive responses. See Methods section for experimental details. The results shown are the average of two separate experiments, and the standard deviation values did not exceed 15% of the mean value. P values were considered significant at P < 0.05.