Anti–CII-specific antibody levels in serum from lentivirus-treated mice. (a) IgG1 and (b) IgG2a isotype CII–specific antibodies in serum obtained at days 28, 40, and 62 after immunization from mice injected with LNT-Ii-CLIP and LNT-Ii-CII viral particles 28 days before CII immunization. Statistical analyses were performed using Student's t-test. Data are expressed as mean ± SEM. Day 28: LNT-Ii-CLIP (n = 9), LNT-Ii-CII (n = 10); Day 40: LNT-GFP (n = 8), LNT-Ii-CLIP (n = 13), LNT-Ii-CII (n = 11); Day 62: LNT-Ii-CLIP (n = 5), LNT-Ii-CII (n = 5). *P < 0.05 LNT-Ii-CII versus LNT-Ii-CLIP; †P < 0.05 LNT-Ii-CII versus LNT-GFP.