Ryan Morris

Introduction: CRISPR, Clustered Regularly Interspaced Palindromic Repeats, has stormed onto the scientific stage in a relatively short period of time and is at the forefront of gene-editing technology. Originally discovered as an adaptive immunity system against bacteriophages in Streptococcus pyrogenes, the CRISPR/Cas 9 system is now being used to tackle some of the most challenging medical complications of our time. One such allusive cure is to Human Immunodeficiency Virus (HIV), a dsRNA retrovirus that selectively targets CD4+ cells and inserts a dsDNA copy into the host’s genome ^[1,2]. HIV therapy regiments have come a long way changing a once morbid prognosis to a very manageable disease thanks to advances such as HAART ^[2]. Despite these advances the cure for HIV remains allusive due to latent virus return. CRISPR has proved to be a means by which to excise HIV DNA from infected cells. Methods Using HIV infected cell lines, CRISPR guided gene editing was used to inactivate incorporated viral DNA. Guide RNAs (gRNA) were generated against discrete areas within the HIV viral genome. CRISPR along with the Cas9 endonuclease were introduce into the cell lines along with the gRNA to make site specific edits ^[3]. Once the DNA was cleaved, host cell non-homologous end joining (NHEJ) was utilized to combine the cleaved strains together. With this general approach several different strategies were executed. Results These strategies included introducing mutations within critical HIV gene regions of which the second exon of Rev was found to be the most effective at silencing HIV infection ^[4], excising portions or the entirety of the viral genome from host or inducing immunity by creating novel genes, CCR5Δ32 within iPSCs (induced pluripotent stem cells) driven down the lymphocyte lineage that did not interact with HIV gene products conferring immunity to the host ^[5]. Conclusions Studies have shown that CRISPR can be used to cure cellular lines of HIV infection. These findings as of yet have never been used in a human trial. Human trials utilizing CRISPR have been approved in a study of cancer patients is currently underway ^[6]. These trials may open the door for future use of CRISPR in treating human disease, including HIV caused immunodeficiency.

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4. Zhu, W., Lei, R., Le Duff, Y., Li, J., Guo, F., Wainberg, M.A., and Liang, C. (2015). The CRISPR/Cas9 system inactivates latent HIV-1 proviral DNA. Retrovirology 12, 22.
5. Ye L, Wang J, Beyer AI, Teque F, Cradick TJ, Qi Z, et al. Seamless modification of wild-type induced pluripotent stem cells to the natural CCR5Delta32 mutation confers resistance to HIV infection. Proc Natl Acad Sci U S A. 2014;4:4.
6. Reardon S. (2016) First CRISPR clinical trial gets green light from US panel. Nature News. Doi:10.1038/nature.2016.20137