October 30, 2016

Research Roundup: Gene editing, mosquito takeover, and decoys for drug resistance

Senior Program Assistant

A key target of the HIV virus is immune cells known as T cells. The virus infects T cells and hijacks the cell’s genetic machinery, enabling it to multiply and spread throughout the body. However, some T cells have genetic mutations that protect against HIV infection, and scientists at University of California, San Francisco (UCSF), are using CRISPR—a novel approach to gene editing—to insert these protective genetic mutations into ordinary T cells. First, the team used CRISPR to rapidly identify all T cell genes involved in HIV infection. Next, they inserted 149 different genetic mutations into T cells, 6 of which successfully blocked the virus. Eventually, the researchers hope that one or more of these mutations could be developed into a drug to prevent or treat HIV/AIDS. Biotech company Sangamo Biosciences is currently testing one such gene mutation that in early results appears to lower the viral load of participants. However, other studies suggest that the virus may be able to outsmart this approach, mutating until it is able to infect T cells. Consequently, an effective treatment may need to elicit multiple gene mutations in T cells, either concurrently or sequentially.

Aedes aegypti mosquito larvae (Photo: National Institute of Allergy and Infectious Diseases)

Over the past five years, the Eliminate Dengue Program has released mosquitoes infected with the innocuous Wolbachia bacteria into small communities in Colombia, Brazil, Vietnam, Indonesia, and Australia. The bacteria colonizes a multitude of insect species, and while it doesn’t harm the Aedes aegypti mosquito—which spreads Zika, dengue, and yellow fever—it does prevent these viruses from replicating and blocks further transmission. Wolbachia is passed down from generation to generation of A. aegypti with each generation only living for a few weeks. Consequently, within weeks of releasing Wolbachia-infected mosquitoes into the wild, disease transmission drops drastically. Now, Eliminate Dengue will be conducting two large-scale trials in Bello, Colombia, and Rio de Janeiro, Brazil, to determine if this approach can successfully combat mosquito-borne illnesses in urban areas home to millions. The trials are funded by the United States and United Kingdom governments and philanthropic organizations the Wellcome Trust and the Bill & Melinda Gates Foundation.

The highly drug-resistant Methicillin-resistant Staphylococcus aureus (MRSA) bacteria is only susceptible to a few, last-resort antibiotics, including daptomycin, which is effective against two-thirds of MRSA infections. Now, scientists at Imperial College London have discovered how the remaining one-third of MRSA infections evade antibiotics. The bacterial cells use chemical signals to communicate with one another, however, some cells can shut down this communication system. Once that system is deactivated, the bacterial cells are able to produce decoys—molecules that have a similar outer layer to the bacteria, and consequently are targeted by the antibiotics. Thus, the antibiotics are wasted on the decoy cells and the bacterial cells are able to thrive. These findings could pave the way for new ways to treat MRSA, by combining daptomycin with a drug that interferes with the decoy system. Currently, clinical trials are underway to test such an approach, combining daptomycin with approved and experimental antibiotics that impede either the production or release of decoy molecules.