Genetic alterations that give rise to a rare, fatal disorder known as MOGS-CDG paradoxically also protect cells against infection by viruses. Scientists at the Lewis Katz School of Medicine at Temple University have harnessed this unusual protective ability in a novel gene editing strategy that is designed to eliminate HIV-1 infection with no adverse effects on cell mortality.
The new approach is based on a combination of two gene-editing constructs, one that targets HIV-1 DNA and one that targets a gene called MOGS—defects in which cause MOGS-CDG. The Temple researchers showed that in cells from individuals infected with HIV-1 (people with HIV-1; PWH), disrupting the virus’s DNA while also deliberately altering MOGS blocks the production of infectious HIV-1 particles.
The team suggest that their discovery opens up new avenues for the development of a cure for HIV/AIDS. Lead investigators Kamel Khalili, PhD, Rafal Kaminski, PhD, and their team reported their results in Molecular Therapy—Nucleic Acids, in a paper titled “Strategic self-limiting production of infectious HIV particles by CRISPR in permissive cells,” in which the researchers concluded, “Our findings offer the development of a new combined gene editing-based cure strategy for the diminution of HIV-1 spread after cessation of antiretroviral therapy (ART) and its elimination.” Khalili is the Laura H. Carnell Professor and Chair of the Department of Microbiology, Immunology, and Inflammation, Director of the Center for Neurovirology and Gene Editing, and Director of the Comprehensive NeuroAIDS Center at the Lewis Katz School of Medicine. Kamiski is an assistant professor at the Center for Neurovirology and Gene Editing at the Lewis Katz School of Medicine.
Proper MOGS function is essential for glycosylation, a process by which some cellular proteins synthesized in the body are modified to make them stable and functional. Glycosylation, however, is leveraged by certain kinds of infectious viruses. In particular, viruses such as HIV, influenza, SARS-CoV-2, and hepatitis C, which are surrounded by a viral envelope, rely on glycosylated proteins to enter host cells. “Post-translational glycosylation of the HIV-1 envelope protein involving precursor glycan trimming by mannosyl oligosaccharide glucosidase (MOGS) is critically important for morphogenesis of virions and viral entry,” the authors wrote.
However, clinical evaluation of glucosidase inhibitors against HIV found that treatment resulted in side effects. “The global application of pharmacologic inhibitors revealed unexpected, yet noticeable side effects including bintestinal distress and osmotic diarrhea, in part because of the widespread application of the compound that non-specifically suppressed host glucosidases,” the team noted. Nevertheless, they pointed out, harnessing this mechanism for suppressing viral entry to host was deemed “a powerful strategy for antiviral therapy” that required a more specific approach toward the suppression of MOGS in the infected cells.
For their newly reported study, Khalili, Kaminski and their team designed a genetic approach to exclusively turn on CRISPR to impede MOGS gene expression through DNA editing within immune cells that harbor replication competent, latent HIV-1. Their novel approach is expected to avoid any impact on the health of uninfected cells that retain normal MOGS gene function. They found that stimulation of the apparatus in HIV-1 infected cells disrupted the glycan structure of the HIV-1 envelope protein, culminating in the production of non-infectious virus particles.
The authors further explained, “We developed a functional pathway whereby activation of the silent virus and the production of the viral protein, Tat, stimulate CRISPR gene editing apparatus that is delivered to the cells. This strategy is aimed at editing of MOGS gene and is designed for the perturbation of glycan configuration of the HIV-1 envelope protein that eventually results in the production of non-infectious virions.”
They continued, “… it is reasonable to predict that, in a clinical setting, after the reactivation of latent proviral DNA by latency-reversing agents (LRAs), and the expression of Tat, when ART treatment is interrupted, the overall outcome will be the appearance of non-infectious virus with no ability to spread after rebound from the reservoir. Indeed, the combination treatment with CRISPR designed to excise a segment of proviral DNA, yet having no effect on Tat production, further contributes to the elimination of non-infectious viral particles.”
“This approach is conceptually very interesting,” said senior investigator Khalili. “By mitigating the ability of the virus to enter cells, which requires glycosylation, MOGS may offer another target, in addition to the integrated viral DNA for developing the next generation of CRISPR gene-editing technology for HIV elimination.”
Kaminski and Khalili have been working with Tricia H. Burdo, PhD, professor and vice chair in the Department of Microbiology, Immunology, and Inflammation and the Center for Neurovirology and Gene Editing at Temple and an expert in the use of non-human primate models for HIV-1, to further assess the efficacy and safety of CRISPR-MOGS strategy in preclinical studies.
In previous work, the team demonstrated that CRISPR-based technology can successfully remove viral DNA from the cells of infected non-human primates. The authors further suggested that their approach could result in a cure for people with HIV. “… we propose a proof-of-principle design of a novel and safe strategy that begins with the interruption of ART for control of viremia followed by treatment with LRAs to stimulate the expression of CRISPR that is tailored for elimination of HIV-1 and inactivation of MOGS … One may also speculate that the appearance of the inactive, non-infectious viral particles may stimulate the immune system to overcome remaining infectious virus that may escape from elimination by CRISPR-HIV. Thus, the outcome may eventually lead to permanent elimination of HIV-1 in PWH and protects them from re-infection.”