Oropharyngeal mucosal transmission of Zika virus in rhesus macaques

Abstract

Zika virus is present in urine, saliva, tears, and breast milk, but the transmission risk associated with these body fluids is currently unknown. Here we evaluate the risk of Zika virus transmission through mucosal contact in rhesus macaques. Application of high-dose Zika virus directly to the tonsils of three rhesus macaques results in detectable plasma viremia in all animals by 2 days post-exposure; virus replication kinetics are similar to those observed in animals infected subcutaneously. Three additional macaques inoculated subcutaneously with Zika virus served as saliva donors to assess the transmission risk from contact with oral secretions from an infected individual. Seven naive animals repeatedly exposed to donor saliva via the conjunctivae, tonsils, or nostrils did not become infected. Our results suggest that there is a risk of Zika virus transmission via the mucosal route, but that the risk posed by oral secretions from individuals with a typical course of Zika virus infection is low.Zika virus (ZIKV) is present in body fluids, including saliva, but transmission risk through mucosal contact is not well known. Here, the authors show that oropharyngeal mucosal infection of macaques with a high ZIKV dose results in viremia, but that transmission risk from saliva of infected animals is low.

Fig. 1

Study design. Two cohorts of animals were inoculated with Zika virus either by application of stock virus to the tonsils (orange filled symbols) or subcutaneously (blue-filled symbols). Saliva from animals infected subcutaneously was used to challenge naive recipient animals (open symbols) either to the palatine tonsils, conjunctivae or nasal passages. Blood plasma, urine and oral swabs (and/or saliva) were tested for Zika virus RNA by qRT-PCR in all animals

Fig. 2

Longitudinal detection of ZIKV RNA in plasma, urine and oral swabs in subcutaneously infected animals (blue) or animals inoculated directly to the tonsils (orange). a Legend for graphs represented in parts b–d. Orange lines represent animals infected via the tonsils and blue lines represent animals infected via subcutaneous injection. b ZIKV RNA copies per ml of peripheral blood plasma. c ZIKV RNA copies per ml of passively collected urine from pans. d ZIKV RNA copies per oral swab. The gray box indicates the time frame in which saliva or an oral swab sample from saliva donor animals was used to challenge recipient animals. The y axis starts at the limit of quantification of the qRT-PCR assay (100 vRNA copies per ml)

Fig. 3

Longitudinal Zika virus load detected in saliva and oral swabs. Two of three animals infected either via the tonsils (under orange monkey) or subcutaneously (under blue monkey) had sufficient saliva collected for viral load testing. Only time points in these four animals at which both saliva (gray) and oral swabs (black) were tested simultaneously are shown. All points not distinguishable above the limit of quantification (100 vRNA copies per ml) are present on the x axis