Viral Vectors: “Friends or Foes” in Gene Therapy

Viruses are usually reputed as highly damaging and are considered harmful particles; however, they may show beneficial effects, for example, in the case of viral vectors in gene therapy. Commonly used viral vectors include adenoviruses or lentiviruses. For a successful gene therapy experiment, an appropriate amount of a therapeutic gene must be administered to the intended tissue without considerable virulence. For a particular gene therapy practice, vectors should be of a distinctive nature that affects its fitness. The desired properties of viral vectors include, but are not limited to, stability, specificity, or low immunogenicity. The accurate realization of gene therapy is only possible by manipulating the current vectors in use or if specific targeted new vectors are developed. Viral vectors are also commonly used to deliver CRISPR/Cas9 because of their strong binding and high in vivo efficiency. However, these vectors pose several challenges including the risk of undesired gene mutations, insertional mutagenesis, off-target effects, carcinogenicity, immunogenic reactions, and limited transfection volumes.