CD8.sup.+ cell antiviral factor

A method of inhibiting the replication of retrovirus in cells comprising exposing the cells to a substantially pure composition of CD8.sup.+ cell antiviral factor defined by the following properties:

• (a) released from activated CD8.sup.+ cells;
• (b) biologically inactivated when exposed to a pH in a range of 10-12 while maintaining biological activity when exposed to a pH in the range of 2-8;
• (c) resistant to heat of 100.degree. C. for 30 minutes to the extent that about 60% of its activity is maintained;
• (d) resistant to trypsin;
• (e) does not affect CD4.sup.+ cell activation or proliferation;
• (f) blocks viral replication by inhibiting viral RNA transcription;
• (g) function not inhibited by antibodies specific for IFN.alpha., IFN.beta., IFN.gamma., TNF.alpha., TNF.beta., TGF.beta., IL-6, IL-4, MIP-1.alpha., MIP-1.beta. or RANTES;
• (h) is not a cytokine selected from the group consisting of IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12, IL-13, IL-15, IL-16, G-CSF, GM-CSF, TNF.alpha., TNF.beta., IFN.alpha., IFN.beta., IFN.gamma., TGF.beta., RANTES, MIP-1.alpha., MIP-1.beta., MCP-1, MCP-3, IP-10, lymphotactin, GRO-.alpha., GRO-.beta., and LIF;
• (i) is not a soluble receptor selected from the group consisting of TNF.alpha.-I receptor and TNF.alpha.-II receptor;
• (j) activity is maintained after being subjected to freezing and thawing;
• (k) sensitive to staph V8 protease but not to protease type XIA (proteinase K);
• (l) does not induce 2'-5'-A synthetase in CD4.sup.+ lymphocytes and is, accordingly, different from interferon;
• (m) precipitated from CD8.sup.+ cell supernatant by 53% ammonium sulfate;
• (n) lipid free;
• and
• wherein substantially pure indicates that any of the cytokines of (h) naturally present in CD8.sup.+ cell extract as well as any soluble receptor of (i) naturally present in CD8.sup.+ cell extract have been separated away.