The common cold virus can infect cells derived from the human placenta, according to a study which suggests that it may be possible for the infection to pass from expectant mothers to their unborn children.
The researchers, including those from Tulane University in the US, said the placenta -- an organ that develops in the uterus during pregnancy -- acts as a gatekeeper, providing essential nourishment from a mother to a developing fetus while filtering out potential pathogens.
The study, published in the journal PLOS One, noted that this barrier isn't as impenetrable as once believed with recent studies showing how viruses such as Zika can slip through its defences.
"This is the first evidence that a common cold virus can infect the human placenta," said study co-author Giovanni Piedimonte from Tulane University.
"It supports our theory that when a woman develops a cold during pregnancy, the virus causing the maternal infection can spread to the fetus and cause a pulmonary infection even before birth," Piedimonte said.
From donated placentas, the researchers isolated the three major cells found in the organ -- cytotrophoblast, stroma fibroblasts and Hofbauer cells.
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In the lab, they exposed these cells to the respiratory syncytial virus (RSV), which causes the common cold.
They found that while the cytotrophoblast cells supported limited viral replication, the other two types were significantly more susceptible to infection.
The researchers said the Hofbauer cells survived and allowed the virus to replicate inside its walls.
Since the Hofbauer cells traveled within the placenta, the researchers suspected these cells could act as a "Trojan horse" and transmit the virus into a developing fetus.
"These cells don't die when they're infected by the virus, which is the problem," Piedimonte said.
"When they move into the fetus, they are like bombs packed with virus. They don't disseminate the virus around by exploding, which is the typical way, but rather transfer the virus through intercellular channels," he added.
The researchers speculated that the virus might attack lung tissue within the fetus, causing an infection which may predispose infants to developing asthma in childhood.