A major part of amfAR’s “Countdown to a Cure for AIDS” initiative, which is aimed at developing the scientific foundations for a cure by 2020, is to determine the best method to detect and measure latently infected cells from individuals on antiretroviral therapy (ART).
Dr. Ramesh AkkinaThis is critical to assessing the outcome of a cure intervention. Writing in the April issue of the journal Virology, amfAR-funded scientist Dr. Ramesh Akkina and colleagues at Colorado State University, along with researchers from the amfAR Institute for HIV Cure Research and Harvard University, reported a very novel approach.
The current “gold standard” for detecting persistent HIV is a test-tube technique known as qVOA (quantitative viral outgrowth assay). It is cumbersome and involves chemicals and antibodies in an attempt to activate virus in latently infected cells. One of its greatest drawbacks, however, is its inability to detect every virus that is capable of growing out of infected cells, estimated at approximately 60 per million cells. Akkina and colleagues sought a living alternative, using mice with human immune systems.
To “humanize” the mice and thus enable HIV to grow in these animals, the researchers used genetically immune-deficient mice transplanted with human stem cells or with bone marrow, liver, and thymus gland cells. They injected these animals with varying numbers of CD4+ T cells—from 100,000 to 20 million cells per mouse—obtained from 11 HIV-positive donors, all on ART. Five of these donors had undetectable viral loads by the standard qVOA.
The injected mice were followed for eight weeks. At weekly intervals blood was obtained in an attempt to detect, by a very sensitive molecular test known as RT-PCR, virus that wasn’t detectable using qVOA. Of the five qVOA-negative samples, four proved positive in the mice. The one sample that failed to produce virus was said to be of “poor quality”—donor samples had been frozen and don’t always thaw out well.
The authors concluded that the higher sensitivity of their humanized mouse models over qVOA and other types of mice used in similar experiments may ultimately lead to avoiding ART interruption as the only means to definitively assess the effectiveness of a potential HIV cure.
Let the mice do the work.
Dr. Laurence is amfAR’s senior scientific consultant.