For the first time, rhesus macaques have been shown to be susceptible to infection by Zika virus, reports a study published in Nature Communications. The Zika virus strain used in this study, which is of Asian-lineage, is closely related to strains currently circulating in the Americas. These results imply that a new animal model of infection can be used to study Zika virus pathogenesis and to test potential therapies.

Infection with Asian-lineage Zika virus has been associated with Guillain-Barre syndrome and foetal abnormalities in the Americas, but the underlying mechanisms remain poorly understood. Immunocompromised mice have been experimentally infected with Zika virus in previous studies, but these mouse models do not mimic key attributes of human infection and foetal development, such as infection in an immunocompetent state.

David O'Connor and colleagues inoculated eight immunocompetent rhesus macaques (two of which were pregnant) with an Asian-lineage Zika virus closely related to strains currently circulating in the Americas. All eight animals became infected, as shown by detection of viral RNA in plasma, saliva, urine and cerebrospinal fluid. The non-pregnant and pregnant animals remained infected for 21 days and up to at least 57 days, respectively. Antibodies directed against the virus were detected by day 21. Inoculation of the same animals with a similar strain of Zika virus ten weeks after the first inoculation did not lead to detectable re-infection, indicating that the animals developed an immune response that protected them against the second virus.

Infection of rhesus macaques with Zika virus provides a relevant animal model for studying pathogenesis and evaluating potential therapies. Further work will be required to determine whether foetal infection and/or abnormalities might occur in the pregnant animals, and whether the presence of virus in body fluids might allow for transmission between animals.