United Nations Global HIV & AIDS statistics 2020 estimated that about 38 million people were infected by the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) in 2019. About 36.2 million of the infected population were adults and 1.8 million were children aged between 0 to 14 years. Although 81% of the infected population were aware of their HIV status, about 7.1 million infected people were unaware of their health condition.
The HIV-1 genome has ten viral proteins assisting in the viral invasion into the host cell and replication. Conventional HIV management includes the administration of antiretroviral therapy (ART) or highly active antiretroviral therapy (HAART). Only 66.8% of the infected population were estimated to be able to access ART in 2019. The conventional therapies still remain the key therapeutic strategy. These therapies successfully inhibit the HIV replication cycle, thereby reducing the viral load and disease progression. Although these therapies have reduced both morbidity and mortality due to the HIV/AIDS, they are unable to eliminate the virus completely from the body which continues to remain as latent viral reservoirs. It poses a risk of disease recurrence with treatment interruption. Thus, HIV is considered as chronic and incurable disease. This warranted the need for a therapeutic strategy capable of inhibiting viral replication and eliminating latent HIV provirus, and therapies based on genome editing have been particularly interesting.
In 2013, CRISPR/Cas9 genome editing technology was first used to prevent re-emergence of HIV/AIDS by disrupting latent HIV-1 provirus and suppressing HIV-1 gene expression in Jurkat cell lines. The promising results prompted researchers to perform similar studies and used transfection and lentivirus to deliver the CRISPR/Cas9 components into the host cell. The sgRNA directed CRISPR/Cas9 system targets the NF-κB binding cassettes in the R region (located in the U3 region of LTR and TAR sequences) of the viral genome. All these studies informed that CRISPR/Cas9 technology can not only inhibit transcription and replication of HIV-1 but also excise internally integrated viral genome from the host cell genome. Thus, the CRISPR/Cas9 technique with a simple approach, high efficiency and limited off-target effects can be used to cure the incurable HIV/AIDS.
The HIV-1 can escape from the cleavage mediated by a single sgRNA, whereas multiple sgRNA based CRISPR/Cas9 genome editing approach has higher cleavage efficiency compared to a single sgRNA. Hence, multiple sgRNA-mediated CRISPR/Cas9 genome editing approach is a promising HIV/AIDS therapeutic strategy.
In addition to therapeutic prospect, CRISPR technology can be used to prevent the entry of HIV-1 into the host cells. The entry of the HIV-1 into host cells is mediated by host cell receptors such as CD4, CCR5, and CXCR4. Since the CD4 receptor is also expressed by immune cells on their surface, the inhibition of CD4 receptors is not advisable. However, CRISPR/Cas9 can be used to disrupt CCR5 and CXCR4 expression. In 2013, CRISPR/cas9 successfully employed to disrupt CCR5 expression in human embryonic kidney. Similarly, 40% disruption of CXCR4 expression has also been reported in CD4+ T cells. Thus, the CRISPR/Cas9 system has the potential of eliminating latent HIV-1-viral pool from infected cells and preventing the entry of the virus into healthy non-infected cells.