Zika virus (ZIKV) is an infectious RNA flavivirus primarily transmitted to humans by the bites of Aedes spp. Mosquitoes. An outbreak of ZIKV began in Brazil in early 2015 and has since spread throughout South America, Central America, and the Caribbean, with autochthonous cases now being reported in the United States (Miami, Florida, and Texas).
The rapid emergence of ZIKV in the Western Hemisphere is of particular concern given the proven association of viral infection with devastating fetal outcomes in pregnant women, including miscarriage and microcephaly.
Although the primary mode of ZIKV transmission is via mosquito bite, it has also been shown that the virus has the capacity for sexual transmission and transmission through blood transfusions from an infected donor has also been reported.
To date, there have been several published mouse models of ZIKV infection; however, these have focused on studying ZIKV-associated complications in pregnant females such as fetal microcephaly and have required the use of immunodeficient animals.
Scientists believe a viable non-human primate (NHP) model may thus better reflect the biology and pathogenesis of ZIKV in acute human infections. Investigations with NHP can also enable serial sampling and analyses of body fluids (e.g. urine, saliva, feces, and semen) that are impractical with rodent models.
Therefore, investigators at the Texas Biomedical Research Institute in San Antonio have recently developed an alternative animal model that mimics key features of the Zika virus infection, including its lingering presence in bodily fluids.
“Given the key similarities to human infections, a marmoset model of Zika may be useful for testing of new drug and vaccines,” said Texas Biomedical Research Institute virologist Jean Patterson, Ph.D. “Having an animal model of Zika infection to study may help us identify places where we might be able to block transmission.”
“That size can be an advantage when testing experimental vaccines and therapeutics that are available in limited quantities,” explained Suzette Tardif, Ph.D., the Associate Director of Research at the Southwest National Primate Research Center at Texas Biomed.
Researchers hope to use what they learn from these monkeys to identify locations where they could effectively block transmission of Zika. Marmosets in the past have proven highly susceptible to other problematic, human-hitting viruses, such as Ebola and Lassa. Given that Zika has also been found in the saliva of these animals in the wild, institute virologist Jean Patterson has theorized that left alone, they could even potentially add an endemic nature to the virus in certain nations.
The next step after infecting male marmosets with the virus is to infect pregnant females to “help us identify where in a pregnancy you’re more likely to have difficulties and more likely to have difficulties to the fetus,” Patterson said.
Infecting pregnant marmosets could lead to a vaccine or drug that can block infection during pregnancy.
“That’s a difficult thing because, as you know, giving pregnant women any kind of drug is always very risky, so we would have to determine if the risk of giving a drug would be better than not and that we could find a drug that could interfere with the infection,” she said.
The research team is optimistic about their findings and is planning the next steps in testing various vaccines.
“We don’t know where it (the Zika virus) will emerge, but we know more cases will show up in the United States,” Patterson emphasized. “It’s befuddling the epidemiologists.”
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.