Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Microbiology and Immunology

Supervisor

Mann, Jamie F.S.

2nd Supervisor

Arts, Eric J.

Co-Supervisor

Abstract

HIV-1 is the etiological agent behind acquired immune deficiency syndrome (AIDS) – a chronic, life-threatening condition that compromises host immune function. After nearly four decades and despite ongoing global efforts, HIV-1 persists in nearly 38 million individuals worldwide. Of this population, only 60% have access to life-saving combination antiretroviral therapy (cART), clearly emphasizing the need to realize a cure. Unfortunately, the establishment of replication-competent provirus in resting CD4+ T lymphocytes represents a significant barrier to HIV-1 curative research. The viral reservoir is highly stable and has a half-life of ~44 months. Therefore, it is unlikely that infection will naturally exhaust over the course of a human lifetime. Furthermore, infected cells are phenotypically indistinguishable from uninfected CD4+ T cells – thus making it difficult to selectively target these cells for eradication. Evidence suggests that HIV preferentially infects and establishes latency within HIV-specific CD4+ T cells and that HIV latency reversal can be achieved using HIV derived proteins. Therefore, a therapeutic vaccine that represents the entire proteome of HIV within a given individual, immediately prior to antiretroviral therapy, might activate the entire cellular reservoir and initiate proviral gene transcription. Herein, we investigate the ability of a highly diverse virus-like particle formulation to ‘shock’ HIV-infected cells into transcriptional activity, thus leading to their eradication via immune-mediated or viral cytopathic effects. This activation vector (ACT-VEC) represents the first targeted approach to HIV-1 latency reversal. Based on the detection of viral RNA in culture supernatants, we show that ACT-VEC significantly outperforms other clinically relevant latency reversing agents at both the acute and chronic stages of infection. Using a quantitative outgrowth assay, we determined that ACT-VEC was also capable of inducing replication competent provirus from HIV-infected CD4+ T cells. Furthermore, we provide preliminary evidence that a virus-like particle formulation can provide an immune-mediated ‘kill’ after transcriptional reactivation occurs. Our VLP construct is also minimally antigenic, suggesting that it will be well tolerated in vivo. All together, our research suggests that ACT-VEC is a highly efficacious transcriptional reactivator that merits further investigation in the context of curative therapeutic strategies.

Summary for Lay Audience

Human immunodeficiency virus 1 (HIV-1) is a virus that, in the absence of treatment, leads to acquired immunodeficiency syndrome (AIDS). AIDS is typically described as a period during which a subclass of immune cells, called T cells, die. In the absence of T cells, an HIV-infected individual is unable to mount a proper immune response and can be at an increased risk of infection by other pathogens (ie. bacteria, viruses, etc.). These infections, which are often uncommon in humans with properly functioning immune systems, lead to AIDS-related death. Despite efforts to stop HIV-1, the virus continues to persist in approximately 38 million individuals worldwide. Of this, approximately 60% have access to lifesaving medications which function to inhibit the virus’ life cycle. Unfortunately, several factors ultimately prevent these medications from being a long-term feasible solution, including i) high therapy-associated cost, ii) the requirement to take medication daily, for life, iii) logistical barriers, and iv) economic barriers. Furthermore, the currently available medications are non-curative due to the ability for HIV-1 to persist within host immune cells. There remains a need for new strategies capable of removing cells harboring HIV-1. The literature suggests that the reservoir can be targeted using small, HIV-1 proteins. These proteins are presented to cells that have a high likelihood of harboring latent HIV-1 and, subsequently, can stimulate the target cell. After reactivation, cells can be targeted by the immune system for destruction. Herein, we present an activator vector (ACT-VEC) that contains proteins encompassing the entirety of HIV-1. This activator vector currently outperforms all clinically-relevant drugs designed to remove latent HIV-1. ACT-VEC causes minimal immune activation, which suggests that it will be well tolerated in further stages of testing. Overall, we present a novel vaccine formulation capable of removing latent virus from host CD4 T cells. The activator vector represents a novel strategy for achieving HIV-1 cure and merits further investigation.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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