Background
As an obligate intracellular pathogen, HIV must hijack resources from infected host cells to support the viral lifecycle. While this includes a viral dependency on host metabolism, little is known about the specific metabolic networks that are essential for infection and viral replication. Previous work leveraging a single-cycle reporter virus has established that blocking the movement of carbon into the TCA cycle from either glucose or glutamine reduces HIV infectivity. In addition to its bioenergetic role, the TCA cycle also serves as a major biosynthetic hub for the synthesis of critical metabolites, like fatty acids. Here, we test the hypothesis that the synthesis of fatty acids is a metabolic dependency during HIV infection.
Methods
To identify the role of fatty acid synthesis during HIV infection, we conducted the following analyses: 1) We tested if the expression of the enzymes involved in synthesizing fatty acids is altered during infection using flow cytometry; 2) We tested the impact of blocking fatty acid synthesis on infection in primary T cells through in vitro perturbational studies; and 3) We have begun to mechanistically map the impact of inhibiting fatty acid synthesis on infection by studying the end product palmitate through metabolite tracing and other biochemical approaches. All experiments were conducted at minimum in technical triplicate and with three experimental replicates where possible.
Results
Through these studies, we identified that the expression of fatty acid synthetic enzymatic machinery is significantly increased during HIV infection of human T cells. Surprisingly, chemical inhibition of fatty acid synthesis increased the susceptibility to infection (3-to-4 fold). However, analysis of viral particle production by p24 ELISA revealed that particle production on a per-cell basis was significantly decreased. Mechanistic studies have demonstrated that this phenotype is dependent on palmitate, the product of fatty acid synthesis.
Conclusions
Our studies indicate that the ability to synthesize fatty acids is a critical metabolic process that can control the balance between infectivity and new viral particle production. While we have identified a role for palmitate in this process, future work will aim to determine the precise biochemical mechanism for this alteration in susceptibility, as well as how in vivo alterations to fatty acid synthesis may affect the clinical progression of HIV infections.
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