(1) it indicates the potential for a second administration of the same vector without the diminished production of transgene and (2) it demonstrates that the incorporation of HIV epitopes within HVR2 does not have a detrimental effect on in vivo transgene production ( Figure 9 ). We speculate that the MPER-modified vector allows boosting compared to AdCMVGag, possibly because the Ad5/HVR2-MPER-L15(Gag) Ad elicits less anti-Ad5 immune response. It is possible that the MPER epitope reduced the immunogenicity of the Ad5 vector. It is also possible that the anti-MPER antibody fraction was not neutralizing with regards to the hexon-modified Ad5 boost. Similar results were seen with experiments performed by Abe and colleagues, their studies support the concept that modified hexon thwarts Ad5 neutralizing antibodies and promotes cellular immune responses [20] .