Commercial and clinical Ad development for HIV vaccines have progressed preferentially more than vector systems such as HRV because, the plasticity of Ad generally exceeds current rhinovirus systems. For example, because it is a relatively small RNA virus, the rhinovirus platform can display an array limited to 60 copies of a single HIV-1 epitope [44] . In comparison, the Ad hexon-incorporation display platform could present an array of 720 HIV-1 epitope copies and the pIX incorporation display platform could potentially present an array of 240 HIV-1 epitope copies. Another significant difference between the two platforms is in the number of locales that have been successfully utilized for heterologous epitopes insertion. In this regard, to our knowledge, the human rhinovirus 14-based platform utilizes a single-epitope insertion site in the major immunogenic portion of the viral VP2 loop 2 [46, 47] . In contrast, the Ad vector platform, could potentially allow incorporation of the HIV-1 MPER epitope into four structurally distinct locales, including: hexon, (HVR2 and HVR5) [20] , protein IX, penton base and/or fiber. Lastly, in contrast to the rhinovirus that lacks this capacity, the Ad platform has sufficient coding capacity allowing for HIV-1 transgene expression in combination with presenting the same or a different antigen on the viral capsid surface. Despite some of the noted limitations with the rhinovirus platform, one of its attractive features has been the previously mentioned development of mutagenic libraries of human rhinovirus 14 chimeras that each display randomized residues representing HIV-1 V3 or MPER epitopes [48, 49] . In this regard, it is worth mentioning that our lab has previously developed a similar approach for screening and identifying heterologous amino acid sequence insertions which have been incorporated into the adenovirus fiber knob region using a modified phage display approach [50] [51] [52] . Overall, through extensive and ongoing vector development by both our group and others, the Ad platform offers a dynamic level of plasticity that translates into the advantage of multiple vaccine development [20] .