ISOLATION OF A C-TYPE RETROVIRUS FROM AN HIV-INFECTED CELL-LINE

A study by electron microscopy of HUT78 cells infected with the ARV-2 strain of HIV-1 revealed, in addition to virions having the characteri stic morphology of a lentivirus, the presence of numerous C-type parti cles, suggesting that the analysed specimen might in fact contain two different viruses. In order to further investigate this observation, t he cell culture supernatant was filtered and mixed at serial dilutions with uninfected HUT 78 cells. In this way, it was possible to obtain cells producing only virions with C-type morphology and a Mn++ depende nt reverse transcriptase activity which in a sucrose gradient was foun d to peak at a buoyant density of 1.16 g/cm3. The RNA purified from th e culture medium was not detected by reference DNA probes for either H IV-1 and -2 or HTLV-I and -II. In an indirect immunofluorescence assay , sera from patients seropositive for these human retroviruses failed to recognize any antigen in the cells producing only the C-type partic les. Using the same technique, plasma samples from 100 blood donors al so gave negative results. The presence of this retrovirus could be the result of previous laboratory contamination but the possibility that it is indeed a human virus has to be considered.