New Delhi, Feb 22 US researchers have identified how Zika virus covertly spreads in placental cells, causing disruptions in the immune system and leads to foetal death.
Infection with Zika virus, which is transmitted by mosquitoes, in pregnancy is known to cause neurological disorders, foetal abnormalities, and foetal death.
Until now, how the virus manages to cross the placenta, which nurtures the developing foetus and forms a strong barrier against microbes and chemicals that could harm the foetus, has not been clear.
Researchers at Baylor College of Medicine and Pennsylvania State University discovered that the Zika virus builds underground tunnels -- a series of tiny tubes called tunnelling nanotubes -- that facilitate the transfer of viral particles to neighbouring uninfected cells.
The team found that a Zika protein called NS1 influences the formation of these tiny tunnels. "Exposure of placental cells to the NS1 protein of Zika virus triggers tunnel formation. As the tunnels develop and connect neighboring cells, a path opens for the virus to invade new cells," said Dr. Rafael T. Michita, postdoctoral research associate at Baylor lab.
"Zika is the only virus in its family, which includes dengue and West Nile viruses among others, whose NS1 protein triggers the formation of tunnels in multiple cell types.
"Other viruses unrelated to Zika, such as HIV, herpes, influenza A, and SARS-CoV-2, the virus that causes COVID-19, can also induce tiny tunnels in cells they infect and use the tunnels to spread to uninfected cells. This is the first time that tunnelling has been shown by Zika virus infection in placental cells," Michita said.
The study, published in the journal Nature Communications, showed that the tiny conduits provided a means to transport not only viral particles but also RNA, proteins, and mitochondria, a cell's main source of energy, from infected to neighbouring cells.
Transporting mitochondria through the tunnels may not only provide an energetic boost to virus-infected cells but also potentially help the Zika virus to avoid antiviral defenses implemented by the placenta, the researcher said.
The findings offer vital insights that could be used to develop therapeutic strategies targeted against this stealth transmission mode.
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