New Animal Model Developed to Aid Zika Studies

 When battling emerging infectious diseases, finding a model that accurately recapitulates the pathogenesis of the infection is critical to developing effective therapeutic interventions. Yet, as most scientists can attest, the things that are the most critical are also most often the most difficult to obtain. An alternative animal model that mimics key features of the Zika virus infection, including its lingering presence in bodily fluids, has been developed at Texas Biomedical Research Institute in San Antonio.

Findings from the new study were published recently in Scientific Reports, in an article entitled “Experimental Zika Virus Inoculation in a New World Monkey Model Reproduces Key Features of the Human Infection.”

The research team found that acute infections in male marmosets, a New World monkey, resemble the human illness the Zika virus creates in people, including the presence of the virus in semen, saliva, and urine up to two weeks after the initial infection. The primary mode of transmission for the Zika virus is through mosquito bites. Moreover, according to the Centers for Disease Control and Prevention, the disease can be spread through sexual contact.

"Given the key similarities to human infections, a marmoset model of Zika may be useful for testing of new drug and vaccines," noted senior study investigator Jean Patterson, Ph.D., a Texas Biomedical Research Institute virologist. "Having an animal model of Zika infection to study may help us identify places where we might be able to block transmission." Like 80% of humans infected with the Zika virus, most of the nonhuman primates used in the current study lacked any apparent clinical symptoms. 

Zika was first identified in Africa in the mid-20th century. It emerged as an infectious threat in the Western Hemisphere in 2015 in Brazil, where it made news for creating a spate of congenital disabilities, including the devastating brain anomaly microcephaly. A year ago, Texas saw its first documented cases of the Zika virus transmitted by local mosquitoes. The handful of cases along the Texas–Mexico border likely won't be the state's last encounter with this emerging virus, according to public health reports.

The Texas researchers looked at Zika infection in the common marmoset (Callithrix jacchus) and determined it to be a good model for studying the pathogenesis of the disease. Additionally, since the primates are small (about the size of a rat), they hold advantages over other animal models.

"That size can be an advantage when testing experimental vaccines and therapeutics that are available in limited quantities," noted co-senior study investigator Suzette Tardif, Ph.D., associate director of research at the Southwest National Primate Research Center at Texas Biomed.

These monkeys have been shown to have a high susceptibility to infection by a variety of pathogens, including Ebola and Lassa viruses that affect humans, making marmosets useful for drug and vaccine testing. Recently, Zika virus was discovered in serum and saliva from marmosets living in the wild in Brazil, suggesting that these nonhuman primates are "a potential reservoir for maintaining Zika virus in endemic countries," according to Dr. Patterson's report.

The research team was optimistic about their findings and is planning the next steps in testing various vaccines. Scientists around the world are working to discover more about how the disease is transmitted from pregnant mother to the fetus, including scientists at Texas Biomed, and this new model could prove to be invaluable in these studies.