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HIV and Emerging Infectious Diseases Program


Study Name

A Double Blind Randomized Placebo Controlled Study Examining the Effects of a Non-absorbable (Rifaximin) Antibiotic on the Chronic Immune Activation Observed in HIV-infected Subjects

Study Number


Goal of Study

You are being invited to participate in this research study because you are HIV-infected and are taking medications (antiretroviral therapy [ART]) for treating this infection. HIV treatment can control HIV, but therapy does not provide a cure. The reasons why therapy does not cure HIV infection are not well understood. HIV persists in blood cells for years, even while people are taking ART. In addition, HIV infection leads to an activated immune system, which can contribute to persistence. Immune activation improves, but does not fully resolve with ART. A better understanding of HIV and the immune activation HIV causes will help understand HIV persistence and identify new strategies to eliminate HIV infection.

In this study, we are investigating the source of immune activation in HIV infection. In general, chronic immune activation may be thought of as an exaggerated response to infection. It is not clear why HIV-infected patients have this exaggerated response. One theory why HIV infection causes immune activation has to do with the gastrointestinal tract. HIV infects immune cells the intestine (gut) soon after infection and causes damage to the intestinal immune barrier. The damage to the intestine lets bacterial products cross into the blood stream, leading to ongoing inflammation. Even when a person with HIV feels well, this chronic leakage of bacterial products may affect the immune system. In this study, we are planning to investigate whether taking Rifaximin, an antibiotic used to reduce bacteria in the intestine, will reduce leaking of bacterial products into the blood stream. Rifaximin is taken by mouth and is designed to stay inside the digestive system, so it’s effects on bacteria are only within the intestines.

Rifaximin is approved by the Food and Drug Administration (FDA) for treating people with traveler’s diarrhea with a particular bacteria (called “noninvasive E. coli”) and to reduce the risk of liver related encephalopathy that arises from increased gut bacteria. Individuals with travelers diarrhea usually take rifaximin for several weeks. Individuals at risk for hepatic encephalopathy take rifaximin for many months at a time. In this study we are using Rifaximin to reduce bacteria in the gastrointestinal tract, which is a research purpose, and not for an FDA indicated purpose; this is considered an “off- label” use of Rifaximin. Participants in the study will take 550 mg of Rifaximin twice a day, which is a dose approved by the FDA. Participants in the study will be taking the active drug, Rifaximin, for part of the time, and a placebo (sugar pill) part of the time; this is a blinded study and you will not be told which medication (rifaximin or placebo) you are taking. The study drug and the placebo will be provided free of charge to participants.

Study Regimen

This study will take place at three different sites: Walter Reed National Military Medical Center (WRNMMC), University of Pittsburgh, and the National Institutes of Health (NIH). You will be part of this study for a maximum of 20 weeks. The study duration may be extended if you need to receive other therapy, such as antibiotics or a vaccine, during the course of the study. A total of 44 subjects are expected to take part in the study. As many as 20 subjects may be enrolled at the NIH Clinical Center however we may check as many as 200 patients to see if they qualify to be in the study.

You will be asked to come to the clinic for up to 13 visits; some visits are required and some are optional. The visits include two screening visits to make sure that you are qualified to be in the study. It may be necessary for you to return every week to the clinic. Each visit will last approximately two hours, but the screening visits when you first come to the clinic may take longer. Volunteers will be compensated.

Eligibility Criteria

  • You are age 18 or older, with documented HIV infection.
  • You are currently taking HIV medications.
  • Your viral load been undetectable (<50) for at least the past three years
  • You do not have hepatitis B or hepatitis C.
  • You do not have a history of inflammatory bowel disease, such as Crohn's disease, ulcerative colitis, or C diff.
  • You do not currently take antibiotics.
  • You do not take probiotics (Probiotics in yogurt is allowed).​

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Last Updated June 14, 2013