Six- to ten-week-old C57BL/6, B6.SJL-ptprca (CD45.1+), B6.129S2-Cd4tm1Mak/J (CD4 KO), B6.129S2-H2dlAb1-Ea/J (MHC II KO), C57BL/6-Tg(TcraTcrb)1100Mjb/J (OT-I), and B6.Cg-Tg(TcraTcrb)425Cbn/J (OT-II) mice were purchased from The Jackson Laboratory (Bar Harbor, ME). Thymectomized animals underwent adult thymectomy at the Jackson Laboratory (Bar Harbor, ME). E1/E3 deleted Ad5-SIINFEKL-Luc, Ad5-OVA, and Ad5HVR48(1–7)-Gag have been previously described (35 (link)–38 (link)). Mice were immunized intramuscularly with 109 viral particles of the indicated vector in the quadriceps using 100 µl divided equally between the two legs. NYVAC-Env has been previously described (39 (link)) and was used at 106 pfu per mouse. All animal experiments were performed in accordance with the Institutional Animal Care and Use Committee guidelines of Beth Israel Deaconess Medical Center.