Compounds called defensins--known to prevent viruses from entering cells--appear to do so by preventing the virus from merging to cells' outer membrane, according to a study by researchers at the National Institute of Child Health and Human Development and the National Heart Lung and Blood Institute, both of the National Institutes of Health, and the University of California at Los Angeles.

The study, appearing in the September 11 Nature Immunology, also received funding from NIH's National Center for Research Resources.

"This discovery provides a basic understanding of a first-line defense against such viruses as HIV and the influenza virus," said Duane Alexander, M.D., Director of the NICHD. "This finding may ultimately lead to new strategies for preventing viral illness, and to increased understanding of why some individuals are more resistant to certain kinds of viral infection than are other individuals."

The means by which many viruses infect a cell is a two-step process, said the study's senior author, Leonid V. Chernomordik, Ph.D., Head of NICHD's Section on Membrane Biology in the Laboratory of Cellular and Molecular Biophysics. First, the membrane of the virus' outer coating, or envelope, must attach, or bind to, the outer membrane of the cell. After this attachment has taken place, the viral envelope membrane combines with, or fuses to, the cell membrane. After the two membranes have fused, the virus inserts its genetic material into the cell.

Defensins are produced by cells that are among the first to come in contact with viruses, Dr. Chernomordik explained. Such cells include leukocytes, a type of immune cell, and epithelial cells, which line the surfaces of many organs and tissues.

In the current study, the researchers studied epithelial cells from the inner surface of the lungs. The researchers discovered that defensins block the influenza virus entry into cells by preventing the fusion of viral and cell m
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Contact: Robert Bock or Marianne Glass Miller
bockr@mail.nih.gov
301-496-5133
NIH/National Institute of Child Health and Human Development
15-Sep-2005

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