Australasian Science: Australia's authority on science since 1938

Herpes Infection Route Revealed

By Stephen Luntz

University of Sydney researchers have found a piece in the puzzle explaining how the herpes simplex virus (HSV) infects us.

Approximately 90% of the human population is infected with either HSV1 or HSV2, in most cases without obvious symptoms. Nevertheless HSV1 has been implicated in Alzheimer’s disease, and infection with HSV2 increases the risk of contracting HIV, along with more immediate symptoms.

A/Prof Cheryl Jones of the University of Sydney’s Medical School says she and her colleagues have demonstrated that both strains of HSV infect Langerhans cells in the skin. “These are important immune cells, and we always thought they must have a role,” says Jones.

Rather than alerting the T-cells in the lymph nodes, the expected role of immune cells in the skin, the Langerhans cells appear to mop up the virus. Instead of making them exit the skin to the lymph nodes, Jones says the virus makes the cells “become sticky and die”, thus holding onto enough of the virus so that other cells deeper in the skin are given time to turn on the broader immune system.

In the course of the research Jones’ team also made the more unexpected finding that HSV infects gamma delta T-cells in the skin. At this point the significance of the discovery is unknown. “We found they get infected very early on, but at this stage we don’t know if this is a good thing or not. We know the gamma delta cells have a role in maintaining the integrity of skin cells but we are still investigating what they do,” Jones says.

The clinical significance of the work is not yet clear but Jones says: “It shows we don’t want to target Langerhans cells to turn on. We want to switch on others, perhaps gamma delta cells, to switch on the immune system.”

Jones became interested in the topic through her work at the Children’s Hospital. HSV transmission during birth or in the first weeks of life can be fatal because infant immune systems are often unable to cope with HSV attack.