Inclusion Criteria:
* Provision of signed and dated informed consent form
* Stated willingness and ability to comply with all study procedures and availability for the duration of the study
* Age: 18+
* Established diagnosis of multiple sclerosis
* Evidence of Epstein Barr virus (EBV) infection by serological testing for EBV antibodies antibodies (subjects will have EBV testing performed at the pre-screening visit and if serologies are negative, the subjects will be removed from the study)
Exclusion Criteria:
* Pregnancy or lactation
* Known allergic reactions to components of Truvada
* Previous treatment with Truvada or Descovy
* Unknown HIV status (subjects must have completed HIV antigen/antibody and viral load testing within the prior 6 months to being enrolled or have the testing completed at the pre-screening visit)
* Active or latent hepatitis B (HBV) (subjects must have completed HBV serologies - HbsAg, anti-HBs, and anti-HBc - within the prior 6 months to being enrolled or have the testing completed at the pre-screening visit)
* Current symptoms of severe, progressive, or uncontrolled renal, hematologic, gastrointestinal, pulmonary, cardiac, or neurologic disease, or other medical conditions that, in the opinion of the investigator, might place the subject at unacceptable risk for participation in this study
* Creatinine clearance (CrCl) \<75mL/min, as calculated by the Cockcroft-Gault equation
* Urine dipstick for protein and glucose, excluding values of "1 +" or greater
* Any history of bone fractures not explained by trauma
* Confirmed Grade 2 or greater hypophosphatemia
* Any Grade 2 or greater toxicity on screening tests and assessments
* Taking a medication with known interactions with Truvada including but not limited to: Acyclovir, valacyclovir, adefovir, cabozantinib, carbamazepine, cidofovir, cladribine, cobicistat, diclofenac, multiple non-steroidal antiinflammatories (NSAIDs) or chronic high dose NSAIDs, fosphenytoin or phenytoin, ganciclovir, valganciclovir, oxcarbazepine, phenobarbital, primidone, rifabutin, rifampin, rifapentine, sofosbuvir, tipranavir, or other drugs that significantly affect renal function
* Current treatment with drugs known to affect EBV replication as listed below: Acyclovir, valacyclovir, ganciclovir, valganciclovir, famciclovir, teriflunomide, interferon
