Mutations in the env gene of human immunodeficiency virus type 1 NDK isolates and the use of African green monkey CXCR4 as a co-receptor in COS-7 cells

A previous report from this laboratory described the isolation of the first CD4-independent human immunodeficiency virus type 1 isolate, m7NDK. This i ndependence of CD4 is due to seven mutations located in the C2, V3 and C3 r egions of the gp 120 protein. The present report describes the entry featur es of the m5NDK virus, which contains five of the seven m7NDK mutations, lo cated in the V3 loop and C3 region. The entry of this virus is strictly CD4 -dependent but it can fuse with African green monkey (agm) COS-7 cells bear ing human CD4 (h-CD4). This fusion is directly due to the five mutations in the env gene. It has also been shown that entry of m7NDK is CD4-independen t in COS-7 cells. Since the wild-type NDK and m7NDK viruses use the human C XCR4 protein as coreceptor, agm-CXCR4 was cloned and used in transfection a nd fusion inhibition experiments to show that this receptor can be used by the mb and m7NDK viruses. The wild-type NDK virus, which does not enter COS -7 cells, can use agm-CXCR4, but only when the receptor is transfected into target cells, Although co-receptor nature and expression levels are still major determinants of virus entry, this is the first case where a few mutat ions in the env gene can overcome this restriction.