Novel AIDS therapies based on gene editing

Abstract

HIV/AIDS remains a major public health issue. In 2014, it was estimated that 36.9 million people are living with HIV worldwide, including 2.6 million children. Since the advent of combination anti-retroviral therapy (cART) in the 1990s, treatment has been so successful that in many parts of the world, HIV has become a chronic condition in which progression to AIDS has become increasingly rare. However, while people with HIV can expect to live a normal life span with cART, lifelong medication is required and cardiovascular, renal, liver and neurologic diseases are still possible, which continues to prompt research for a cure for HIV. Infected reservoir cells such as CD4+ T-cells and myeloid cells allow persistence of HIV as an integrated DNA provirus and serve as a potential source for the re-emergence of virus. Attempts to eradicate HIV from these cells have focused mainly on the so-called “shock and kill” approach where cellular reactivation is induced so as to trigger the purging of virus producing cells by cytolysis or immune attack. This approach has several limitations and its usefulness in clinical applications remains to be assessed. Recent advances in gene editing technology have allowed the use of this approach for inactivating integrated proviral DNA in the genome of latently infected cells or knocking out HIV receptors. Here we review this strategy and its potential to eliminate the latent HIV reservoir resulting in a sterile cure of AIDS.

Developmental progress of CRISPR/Cas9 and its therapeutic applications for HIV‐1 infection

“…Several studies [45][46][47] rather than transiently transducing nuclease, may run a risk of generating off-target events. 35,52 To avoid these disadvantages, researchers have to select suitable vector or seek various possible solutions to improve the delivery vehicles.…”

“…As noted by literatures, the currently available common delivery vectors include adenovirus, AAVs, and lentiviruses, etc. Adenoviral vectors possess a prominent effect on immunogenicity, and AAVs vectors are only capable of accommodating small size of an exogenous gene, while lentiviral vectors, integrating into the genome and giving stable expression rather than transiently transducing nuclease, may run a risk of generating off‐target events . To avoid these disadvantages, researchers have to select suitable vector or seek various possible solutions to improve the delivery vehicles.…”

CRISPR Editing Technology in Biological and Biomedical Investigation

“…Now that CRISPR effector endonucleases are available to target RNA, e.g., FnCas9 directed by an engineered RNA-targeting gRNA, inhibition of human RNA viruses such as hepatitis C virus within eukaryotic cells should be possible (Price et al, 2015). Our research has focused on several pathogenic human viruses, including JCV, which is a circular double-stranded DNA virus (Wollebo et al, 2015b), HIV-1, which is a retrovirus (Hu et al, 2014; Kaminski et al, 2016a,b,c; Khalili et al, 2015, 2017; White and Khalili, 2016; White et al, 2015, 2016; Yin et al, 2016, 2017; Zhang et al, 2015a) and HSV-1 a herpesvirus comprised of a double-stranded DNA of greater than 100 Kbp in size (McGeoch et al, 2006). …”

“…However, if only single gRNA is used for a single target site, it is possible to generate InDels where the mutated gene can be changed in such a way as to allow the virus to replicate but yet no longer be susceptible to cleavage by Cas9 because its mutated sequence is now different to the Cas9/gRNA target sequence, i.e., an “escape mutant”. (Wang et al, 2016a, 2016e; Khalili et al, 2017). Thus when designing any gene editing strategy against HIV, it is essential to consider the possibility of escape mutants arising (White et al, 2016).…”

“…In October of 2016, the first clinical trial of CRISPR technology was begun when PD-1 knockout engineered T cells were injected into human subjects as a therapy for metastatic non-small cell lung cancer [Cyranoski, 2016]. We have been interested in our research in developing CRISPR/Cas9 approaches to human pathogenic viruses [White et al, 2015[White et al, , 2016Khalili et al, 2017], in particular HIV-1, which causes AIDS, and Polyomavirus JC (JCV), which causes progressive multifocal leukoencephalopathy [PML; Wollebo et al, 2015b]. We will discuss these studies in the following section as well as CRISPR strategies to other human virus.…”