Factor Helps Shield CD4s from HIV

Researchers at the Gladstone Institute of Virology and Immunology have discovered the mechanism that enables some CD4 cells'the main target of HIV'to escape infection. Scientists found that a key antiviral factor called APOBEC3G helps protect resting CD4 cells from infection. APOBEC3G exists in two forms'a large form that is ineffective in preventing cellular infection and a shorter form that repels the virus. Activated CD4 cells have the longer form of the antiviral compound, but resting CD4 cells carry the smaller form, which makes them impervious to HIV infection. Lab tests showed that blocking the small form of APOBEC3G in resting CD4 cells suddenly removed their antiviral shield and made them susceptible to HIV infection. Researchers are now looking at ways to use this new knowledge therapeutically, including possibly to convert the ineffective, large form of APOBEC3G into the protective, small form in activated CD4 cells or prevent the small form of APOBEC3G from converting to the large form during CD4 cell activation.