Infection of AGM PBMCs confirmed that viral constructs expressing the parental SIVagm Nef (WT, GU) and the HIV-1 Nef (1N, GU1N) differed markedly in their CD3 downmodulation function (Fig. 1j and Supplementary Fig. 1f), while all SIVagm constructs were capable of downmodulating MHC-I and CD28. The gene discussed is CD28; the disease is infection.