Anti-CD3/28 mediated expansion of macaque CD4⁺ T cells is polyclonal and provides extended survival after adoptive transfer

Background: Our lab has previously shown that adoptive transfer of in vitro expanded autologous purified polyclonal CD4⁺ T cells using anti-CD3/CD28 coated beads induced antiviral responses capable of controlling simian immunodeficiency virus (SIV) replication in vivo. Results: Expansion on anti-CD3/28 coated beads was found to induce a true polyclonal expansion as CFSE labeled cells uniformly showed dilution of the dye over several days of culture, in contrast to aliquots of the same cells subjected to mitogen stimulation. Of interest was the finding that CD4⁺ T cells collected before and during early chronic SIV infection or AIDS stage did not show any or only modest differences in proliferative response or expansion kinetics. The reason for such excellent expansion properties was analyzed by the quantitation of telomerase activity in aliquots of expanding CD4⁺ T cells from sample collected at various times post-infection. First, anti-CD3/28 expanded CD4⁺ T cells exhibited telomerase levels 2- to 20-fold higher than the starting population of CD4⁺ T cells. Moreover, while telomerase activity in ex vivo tested CD4⁺ T cells was found to decrease following SIV infection and disease progression, anti-CD3/28 expansion appeared to restore significant levels of telomerase activity as no difference was noted in telomerase expression between CD4⁺ T cells expanded from samples collected before or during the chronic SIV infection. When such expanded and CFSE labeled T cells were autologously transferred to monkeys, evidence for extended survival in vivo was provided as CFSE labeled cells were detected to relatively high levels in blood and spleen at 1week post-infection. Conclusion: In summary, the data suggest that anti-CD3/28 mediated expansion of CD4⁺ T cells retains its immunotherapeutic potential not only during the early stages of lentiviral infection but also at more advanced stages of disease.