(Press-News.org) WHAT:
A mathematical model developed by NIH grantees predicts that women must take the antiretroviral medication Truvada daily to prevent HIV infection via vaginal sex, whereas just two doses per week can protect men from HIV infection via anal sex. This finding helps explain why two large clinical trials testing HIV pre-exposure prophylaxis, or PrEP, in women failed to show efficacy. Participants in the VOICE and FEM-PrEP trials of Truvada and tenofovir (another antiretroviral) for HIV prevention were counseled to take one of the medications daily. However, because they actually took the antiretroviral only about 29 percent of the time in VOICE and about 36 percent of the time in FEM-PrEP, the PrEP strategy did not work.
Angela D. M. Kashuba, Pharm.D., of the University of North Carolina, and colleagues determined what intracellular ratios of active tenofovir and emtricitabine, the drugs that compose Truvada, to the DNA molecules with which they compete are necessary to prevent HIV replication. Next, using data from an early clinical trial in women, the researchers created a mathematical model that predicts these ratios in vaginal, cervical and rectal tissues given standard doses of medication taken 2 to 7 days per week. Then, the scientists calculated the percentage of a study population that would achieve the effective drug-to-DNA-molecule ratio by taking tenofovir or Truvada at each dosing frequency.
The model forecasts that two standard doses per week of Truvada or a daily standard dose of tenofovir would achieve the target ratio in rectal tissue across a study population. A daily standard dose of Truvada would achieve the target ratio in vaginal tissue in more than 75 percent of a study population, according to the model, and in cervical tissue in half of the population. A daily standard dose of tenofovir would achieve the target ratio in cervical and vaginal tissues in less than half of a study population, the model predicts.
It is easier to achieve the target ratio in rectal tissue than in cervical and vaginal tissues, according to the scientists, because the concentration of DNA molecules is lower and of tenofovir is higher in rectal tissue than in the female genital tract.
Both men and women who are prescribed Truvada for PrEP should take the pill daily as directed, according to Centers for Disease Control and Prevention guidelines.
INFORMATION:
ORAL ABSTRACT:
ML Cottrell et al. Predicting effective Truvada® PrEP dosing strategies with a novel PK–PD model incorporating tissue active metabolites and endogenous nucleotides (EN). HIV Research for Prevention 2014. Cape Town, South Africa.
WHO:
Carl W. Dieffenbach, Ph.D., director of the Division of AIDS at the National Institute of Allergy and Infectious Diseases, is available for comment.
CONTACT:
To schedule interviews, please contact Laura S. Leifman, (301) 402-1663, laura.sivitz@nih.gov.
NIAID conducts and supports research—at NIH, throughout the United States, and worldwide—to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at http://www.niaid.nih.gov.
About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.
NIH...Turning Discovery Into Health®
Model by NIH grantees explains why HIV prevention dosing differs by sex
2014-10-30
ELSE PRESS RELEASES FROM THIS DATE:
Seeing dinosaur feathers in a new light
2014-10-30
Why were dinosaurs covered in a cloak of feathers long before the early bird species Archaeopteryx first attempted flight? Researchers from the University of Bonn and the University of Göttingen attempt to answer precisely that question in their article "Beyond the Rainbow" in the latest issue of the renowned journal Science. The research team postulates that these ancient lizards had a highly developed ability to discern color. Their hypothesis: The evolution of feathers made dinosaurs more colorful, which in turn had a profoundly positive impact on communication, ...
The geometry of RNA
2014-10-30
Messenger, transfer, ribosomal... there's more than one type of RNA. The difference lies not only in the sequence of the nucleotides, the "beads" that form the strand, but also in the three-dimensional structure that this long molecule takes on. Computer models are often used to reveal this structure but these tend to be rather complex, and they vary depending on the field of application. A team of SISSA scientists used numerical techniques to develop a new "geometrical" model which has the advantage of being much simpler and faster than those traditionally used as well ...
Cochrane Review of RDT for diagnosis of drug resistant TB
2014-10-30
Researchers from the Cochrane Infectious Diseases Group, hosted at LSTM, have conducted an independent review to examine the diagnostic accuracy of the GenoType® MTBDRsl assay for the detection of resistance to second-line anti-tuberculosis drugs.
While there are a number of different drugs available to people suffering from tuberculosis (TB), resistance to these drugs is a growing problem. People suffering from a drug-resistant strain of TB are more likely to die from the disease, and require treatment with what are described as "second-line" drugs. These drugs can ...
New tech aims to improve communication between dogs and humans
2014-10-30
North Carolina State University researchers have developed a suite of technologies that can be used to enhance communication between dogs and humans, which has applications in everything from search and rescue to service dogs to training our pets.
"We've developed a platform for computer-mediated communication between humans and dogs that opens the door to new avenues for interpreting dogs' behavioral signals and sending them clear and unambiguous cues in return," says Dr. David Roberts, an assistant professor of computer science at NC State and co-lead author of a paper ...
Ion adsorption matter in biology
2014-10-30
New York | Heidelberg, 30 October 2014 Biological membranes are mainly composed of lipid bilayers. Gaining a better understanding of adsorption of solution ions onto lipid membranes helps clarify functional processes in biological cells. Now, a new study provides a quantitative description of the equilibria between lipid membranes and surrounding solution ions. Joanna Kotyńska and Zbigniew Figaszewski from the University of Bialystok, Poland, are the authors of a study describing these findings, just published in EPJ E. In addition to shedding some light on biological ...
Accident prone eczema patients
2014-10-30
CHICAGO --- Intense itching and dry, irritable skin aren't the only problems adults with eczema face. They are at greater risk of accidental bone fractures and other injuries, a new Northwestern Medicine® study has found.
This is the first study to find adult eczema is a risk factor for fractures and other injuries.
The increased odds of accidental injury could be directly related to the side effects of steroids and sedating antihistamines commonly prescribed to treat the skin disorder or the under-treatment of severe cases, study authors suggest.
"Many eczema ...
Griffith scientists propose existence and interaction of parallel worlds
2014-10-30
Griffith University academics are challenging the foundations of quantum science with a radical new theory based on the existence of, and interactions between, parallel universes.
In a paper published in the prestigious journal Physical Review X, Professor Howard Wiseman and Dr Michael Hall from Griffith's Centre for Quantum Dynamics, and Dr Dirk-Andre Deckert from the University of California, take interacting parallel worlds out of the realm of science fiction and into that of hard science.
The team proposes that parallel universes really exist, and that they interact. ...
'Nanomotor lithography' answers call for affordable, simpler device manufacturing
2014-10-30
VIDEO:
Nanoengineers at the University of California, San Diego recently invented a new method of lithography in which nanoscale robots swim over the surface of light-sensitive material to create complex surface...
Click here for more information.
What does it take to fabricate electronic and medical devices tinier than a fraction of a human hair? Nanoengineers at the University of California, San Diego recently invented a new method of lithography in which nanoscale robots swim ...
Greater inequality within UK, USA than some developing countries, trade 'footprint' shows
2014-10-30
The United States and United Kingdom buck the overall trend of developed countries having more egalitarian domestic economies than the countries they trade with.
The finding comes from the first ever 'inequality footprint' of nations, created by researchers at the University of Sydney, demonstrating the link that each country's domestic economic activity has to income distribution elsewhere in the world.
Australia, with a comparable level of international trade activity, still maintains greater internal equality than the trading nations that 42 percent of our consumption ...
Air quality and unconventional oil and gas sites
2014-10-30
Research suggesting air pollutants released by unconventional oil and gas production are well over recommended levels in the US is published today in the open access journal Environmental Health. High levels of benzene, hydrogen sulfide and formaldehyde were found. The study is the first to be based on community sampling by people who live near production sites and could be used to supplement official air-quality monitoring programs.
Unconventional oil and gas come from reserves that do not readily flow to the surface. This is because they are either distributed throughout ...