Kenya to start trial of new vaccine that stops HIV infecting cells

Kenya is set to launch the clinical human trial of a vaccine that has the potential to stop HIV infecting cells.

Scientists involved in the promising trial said Friday during final preparatory meetings that recruitment for the trial would begin in the next three weeks.

ANTIBODIES

The new vaccine being tested will apply a ‘block approach’ in stopping HIV from attaching itself onto cells. HIV is a virus spread through certain body fluids. The virus attacks the body’s immune system, specifically the CD4 cells, often called T-cells.

The clinical trial codenamed ‘IAVI W001 trial. 664gp140. W001’ will test the vaccine candidate dubbed BG505 SOSIP — a molecule cloned to look exactly as the HIV one — on Kenyan volunteers to check for safety and efficacy.

“This is phase one of the first human trial for this vaccine and over the next one-and-a-half years, the trial will seek to answer questions on how safe the vaccine is and how well it can induce the human body to produce antibodies that can neutralise HIV,” said Prof Omu Anzala, the director of Kenya AIDS Vaccine Initiative (KAVI), the site for the clinical trial.

The researchers spoke during a scientific talk at the University of Nairobi College of Health Sciences’ KAVI-Institute of Clinical Research.

He said the relevant infrastructure and technology transfer for the trial had been concluded at the site.

“The candidates (HIV-negative), will get three shots every month for the first three months … and then we will start to keenly follow them up … to see did it work or not,” he explained. In animal testing, the trial vaccine showed promising results by causing production of antibodies that neutralised a HIV-like virus. Investigators hope to see if a similar specific response is elicited in humans.

PRE-INFECTION

According to Dr Elise Landais, senior research scientist at the Neutralising Antibody Centre, International Aids Vaccine Initiative (IAVI), in New York, which is sponsoring the trial that developed the molecule BG505 SOSIP.664gp140, it belongs to a new generation of immunogens molecules that are capable of causing an immune response in the body called nativelike trimers. They induce broadly neutralising antibodies with capacity to attack the HIV virus in the body upon detection.

The BG505 SOSIP.664 gp140 trimer was engineered by a team directed by John P. Moore, Ph.D., at the Weill Cornell Medical College, Rogier Sanders, Ph.D., now at the University of Amsterdam Academic Medical Center, and Andrew B. Ward, Ph.D., and Ian A. Wilson, D.Phil., at Scripps Research. The outcome of their work was an important advance in stabilizing the highly fragile Env protein in a native-like configuration.

Collaborators in the trial include the Fred Hutchinson Cancer Research Center, Seattle HIV Vaccine Trials Unit; Kenya AIDS Vaccine Initiative-Institute of Clinical Research, University of Nairobi, Kenya (KAVI-ICR, Nairobi); Massachusetts General Hospital, Translational and Clinical Research Center (Boston); and the pharmaceutical company GSK.

“So BG505 SOSIP. 664gp140 is the molecule that will be put in the test candidates by vaccination,” said Dr Landais. “This is the first time we’re trying anything like this. Before the molecule, we were working with HIV products that we discovered recently weren’t very good at achieving the desired results.”

“Now we know the right shape of the molecule that sits on the HIV virus and hence this trial,” she went on. “Before, we were looking at a certain shape of immune cells that are the ones that are killing the infected ones but this time, what we’re trying to activate are cells that are going to produce antibodies that will actually block the virus even before it infects the cells. So instead of coming after the infection has already happened, we’re trying to block it pre-infection. All the products we had before couldn’t activate this kind of response because it did not have the right shape.”

HIV is covered by an envelope protein (Env), which is shaped like a three-pronged spike. This spike, known as a trimer, is a target for antibodies produced by the human immune system after infection. Some of these antibodies can block viral replication by preventing entry into cells. Nativelike trimers are molecules that are designed to look like the spikes on the outer surface of HIV and can induce the body to develop neutralising antibodies.

Prof Anzala said this is a new product. “Previously, we have used products that elicit T-cells, but this particular product is eliciting humoural immunity or B-cells that will give broad and potent neutralising antibodies.”