The tide is high..., page-27

In the abstract of the paper A platform for discovery of functional cell-penetrating peptides for efficient multi-cargo intracellular delivery, which was published last year, it is stated

We report a versatile platform for the isolation of peptides delivering a wide range of cargos into the cytoplasm of cells. We used this screening platform to identify multiple “Phylomer” CPPs, derived from bacterial and viral genomes.

In the introductory section it is explained that, since pathogenic bacteria and viruses have evolved sequences to facilitate transport through cell membranes, Phylogica’s scientists hypothesized that adding fragments from the genomes of such species into Phylomer libraries could provide novel CPPs. Subsequently, Phylomer libraries were constructed from fragmented genomic material from pathogenic bacteria, archaea and pathogenic viruses.

If you follow the link at the end of the article to Supplementary Table 3, you’ll find a fairly long list of viruses listed in the Synthetic Viral Sequences Library.

In the 2015 research article, Viral and Other Cell-Penetrating Peptides as Vectors of Therapeutic Agents in Medicine you can find some discussion re CPPs and immunogenicity. In the section CPPs and Host Immune Response it is stated that, when compared with recombinant viruses, as carriers of therapeutic molecules, cell-penetrating peptides can be considered much safer in terms of their immunogenicity. It does note that CPPs as transport peptides may still be capable of inducing humoral immune response of the host organism against the therapy but suggests that if a given CPP shows stronger immunogenic properties, it is easily replaceable from a wide choice of CPPs available today.