No vaccines and antiviral drugs are currently available

No vaccines and antiviral drugs are currently available to prevent and treat ZIKV infection. Animal models are essential for the development of such countermeasures. Young A129 mice (lacking interferon α/β receptor) and AG129 (lacking interferon α/β and γ receptors) were recently reported to succumb to ZIKV infection and to develop neurological signs (Aliota et al., 2016; Lazear et al., 2016; Malone et al., 2016). Since these mouse models are deficient in innate immune response, an immune competent animal model is needed. Non-human primates have been well documented as a more relevant animal model for flavivirus infections (Sariol and White, 2014; Zompi and Harris, 2012), and have been widely used for DENV and WNV pathogenesis studies and vaccine efficacy tests (Sariol and White, 2014). ZIKV was first isolated from a febrile rhesus macaques (Dick et al., 1952). Multiple monkey species in forests were found to be seropositive for ZIKV (McCrae and Kirya, 1982), suggesting that non-human primates can be infected and support viral replication. Initial experiments performed in 1950s showed that rhesus monkeys inoculated subcutaneously (s.c.) or intracerebrally (i.c.) with the African ZIKV strain MR766 developed no signs of pyrexia, but generated antibodies within 2 to 3weeks after infection (Dick, 1952). However, bioinformatics analysis suggests that the ongoing epidemic strains in the Americas have accumulated some amino SCH727965 changes that might contribute to the explosive epidemics (Faria et al., 2016; Wang et al., 2016). Here, we have established a non-human primate model using a contemporary ZIKV strain GZ01/2016 (GenBank accession no: KU820898) that was isolated from a patient returned from Venezuela to China in 2016 (Zhang et al., 2016). ZIKV infection upon subcutaneous in rhesus macaques resulted in fever, viremia, and robust viral shedding in multiple body fluids including saliva, urine, and lacrimal fluids. The major target organs of ZIKV and specific immune response in non-human primates were also characterized in detail. Our study establishes the non-human primate model of ZIKV infection with contemporary clinical isolate that will be valuable for evaluating candidate vaccines and therapeutics as well as understanding ZIKV pathogenesis, dissemination and transmission.
Materials & Methods
Results
Discussion The mechanism of ZIKV pathogenesis remains largely unclear. This is partly due to the lack of a robust animal model that recapitulates the clinical manifestations and disease kinetics as seen in ZIKV patients. Our results showed that rhesus macaques could be infected by the contemporary ZIKV strain that is circulating in south Americas. This non-human primate model described here partly recapitulates some clinical features and viral kinetics in ZIKV-infected patients, and therefore may serve as a model to study ZIKV disease and pathogenesis. Very recently, a rhesus macaque model of ZIKV infection was reported with a clinical strain isolated in French Polynesian in 2013 (Dudley et al., 2016). The 2013 ZIKV strain caused viremia and viral RNA shedding in urine and saliva, while viral shedding in lacrimal fluids was not determined. Specially, inappetence was seen in most ZIKV-infected animals (Dudley et al., 2016), and no other abnormal clinical sighs were noted in their study. In our study, four of five rhesus macaques developed fever upon ZIKV infection, that is directly associated with disease. The challenge dose used in Dudley\'s experiments was 100-fold lower than that in our study, which may account for the difference in clinical symptoms. The viral shedding features in various body fluids in ZIKV-infected macaques correlated with the clinical findings from patients. The presence of high loads of viral RNA in these body fluids supports that besides blood, urine and saliva are now used for clinical diagnosis of ZIKV. Especially, our results demonstrate that viral RNA was abundant in lacrimal fluids in ZIKV-infected adult macaques, supporting the use of tears or lacrimal fluids for clinical diagnosis. ZIKV-associated damages have been documented in babies with microcephaly (de Paula Freitas et al., 2016; Ventura et al., 2016a; Ventura et al., 2016b), and conjunctivitis is also a common symptom in adult ZIKV patients (Dasgupta et al., 2016; Deng et al., 2016; Duffy et al., 2009). Whether the level of viral RNA in body fluids associated with disease severity remains unknown.