Coreceptor requirements of primary HIV type 1 group O isolates from Cameroon

HIV-1 group O has its epicenter in Cameroon and neighboring countries and i s responsible for 3 to 5% of all HIV infections in this region. It is belie ved that HIV-1 group O was introduced into the human population by a separa te cross-species transmission, occurring independently of the HIV-1 (group M and group N) and HIV-2 transmissions. We have studied the coreceptor requ irements of 12 primary HIV-1 O-type isolates from individuals with differen t clinical symptoms. Only 2 of these 12 viruses showed a syncytium-inducing phenotype after infection of primary peripheral blood mononuclear cells (P BMCs) and were infectious for the T cell line C8166, These isolates used CX CR4 as a coreceptor for entry, whereas the remaining isolates used only CCR 5 efficiently. One isolate was able to use BOB and CCR8 as coreceptors in a ddition to CXCR4 All group O isolates tested were efficiently inhibited by SDF-1 or RANTES, the natural ligands of CXCR4 and CCR5, respectively. These results indicate that CXCR4 and CCR5 are the principal coreceptors for HIV -1 O-type viruses, Most of the HIV-1 group O isolates studied were derived from patients at later stages of the disease. Although HIV-1 group O and gr oup M infections do not differ in their pathogenesis, the studied isolates did not evolve to use a broad range of coreceptors as described for HIV-1 g roup hi and HIV-2.