A virus in stealth mode: Zika infects babies by tunnelling into placenta
Researchers have discovered Zika’s cunning trick, creating tiny tunnels through the body that can evade the immune system in a similar way to HIV and flu.
- 25 February 2025
- 3 min read
- by Priya Joi
Zika virus came to the world’s attention during the 2016 Olympics in Rio. Athletes and spectators were concerned, not so much for their own health, but for that of any babies they might be carrying.
For most people, Zika symptoms tend to be mild. Fever, conjunctivitis, and muscle and joint pain tend to be the limit of the disease.
For unborn babies, however, the virus can be devastating. When a pregnant person is infected with Zika virus, it can lead to miscarriage or preterm birth.
Babies might be born with neurological disorders or other foetal abnormalities: microcephaly, or a smaller than expected head size, was one widely reported result of the disease.
Exactly how the virus enters the placenta has been a mystery, until now. Researchers have discovered that the virus covertly spreads through placental cells without sounding our immune system’s alarms.
Research has already shown that Zika, which is transmitted by Aedes mosquitoes, is adept at evading our immune system.
Once inside our body, the virus targets dendritic cells that are critical to our immune response and hijacks them so that they can’t fight the infection. Other research shows that when the virus invades the foetal brain, it controls the RNA metabolism expressed in cell nuclei, which can damage brain development.
Tunnelling through on a covert mission
Normally, the immune system would jump into action as soon as it detects anything that could potentially affect the placenta.
However, as researchers at Baylor College of Medicine, in collaboration with others at Pennsylvania State University, have found, Zika can tunnel through placental cells in a way that keeps it hidden from our immune system.
Have you read?
A Zika virus protein called NS1 is able to form tunnels to connect one placental cell to another, and these tiny nanotubes allow the virus to invade new cells.
“Other viruses unrelated to Zika, such as HIV, herpes, influenza A and SARS-CoV-2, can also induce tiny tunnels in cells they infect and use the tunnels to spread to uninfected cells,” said first author Dr Rafael T. Michita, postdoctoral research associate in Indira Mysorekar’s laboratory at Baylor College. “This is the first time that tunnelling has been shown by Zika virus infection in placental cells.”
Raiding cells for a mobile battery pack
The tiny conduits not only create a path for Zika virus particles to travel through, but they allow human RNA, proteins and mitochondria – the powerhouse of the cell – to leak through.
The researchers suggest that transporting mitochondria from infected to neighbouring cells is a way for the Zika virus to carry its own battery pack with it, aiding viral replication.
Crucially, the researchers also showed that Zika viruses that are altered to be unable to make these nanotunnels could no longer hide from the immune system, and triggered a potent immune reaction.
“These findings offer vital insights that could be used to develop therapeutic strategies targeted against this stealth transmission mode,” said senior author Indira Mysorekar, Professor of Medicine at Baylor College.
More from Priya Joi
