Jacobson is a professor of medicine in the Division of Infectious Diseases and HIV Medicine at Drexel University College of Medicine, specializing in infections diseases, internal medicine and HIV.
Jeffrey Jacobson was among the first physicians to take on HIV/AIDS, and over the past 30 years, he had made defeating the disease his life’s work. As his most recent work has shown, he and his colleagues worldwide are getting very close to achieving precisely that.
The first time Jeffrey Jacobson stared into the eyes of an AIDS patient, the disease that was ravaging the victim’s body didn’t yet have a name. The year was 1981, and Jacobson, then a fellow at Mount Sinai Hospital’s School of Medicine in New York City, was studying to be an infectious disease expert.
Maybe it was a fortunate circumstance; a right place, right time type of coincidence. But the emergence of human immunodeficiency virus at a time when he was starting his medical career presented Jacobson and other young physicians like him with a unique opportunity to rewrite the rules for treating patients with chronic infections.
“Suddenly it fell upon us and others to take care of this whole new group of patients,” says Jacobson, who now is chief of the Division of Infectious Diseases and HIV Medicine at Drexel. “Many of us started inpatient and outpatient programs to treat people and study the disease. First we had to figure out what it was. When the virus was discovered, we had to figure out how it was doing its damage and causing all the complicating infections, and develop ways to treat it.”
Despite many medical advances in the treatment of HIV patients, there still is no cure or vaccine for HIV and some 30 years after his career started, Jacobson continues to help patients manage their HIV.
Drexel Medicine’s Partnership Comprehensive Care Practice is the largest HIV patient care center in Philadelphia, but there was little clinical research taking place there when Jacobson arrived six years ago. Since then, Jacobson landed in excess of $10 million in National Institutes of Health funding for a series of studies on improved HIV treatments, novel medicines and potential vaccines. All of the work has but one goal: finally and forever putting an end to the AIDS epidemic.
A Frustrating Start
Pharmacological advances, increased HIV testing and greater public awareness of how HIV disease is spread have helped stabilize the rate of infection and prolonged life expectancy in industrialized countries like the U.S., where resources are plentiful. But HIV remains an almost certain death sentence in many poorer countries and regions of the world, where infection rates and disease burdens are highest. The World Health Organization estimates there were 34 million people living with HIV/AIDS worldwide in 2011, and there were 1.7 million AIDS-related deaths that year.
In the earliest days of the epidemic, Jacobson found that treating his patients also meant confronting issues of HIV stigma and discrimination. He lobbied to increase access to appropriate medical care for infected prisoners. He convinced a PTA group there was no public health danger in allowing an HIV-infected child to attend school. All the while, he and others sought to better understand why the human immune system was not effective at controlling this highly challenging and lethal virus.
“It was very frustrating in the beginning as there were no effective treatments. And because HIV was a viral infection, it wasn’t clear whether there could be very effective treatments anytime soon,” he says.
In tandem with the race to develop safe and effective antiviral agents to kill the virus, infectious disease researchers started looking at different vaccine approaches and ways to manipulate the immune system to make it more active against HIV. The purpose of these early studies was to try to pinpoint immune system deficiencies and determine whether they could be reversed.
“We’ve always been interested in understanding the immunology of HIV disease and seeing if we can improve the immune response,” Jacobson says. “We wanted to know,
“Pills have really penetrated the market. We’ve seen what they can do and they’ve saved lots of lives and they’ve been really phenomenal at turning the epidemic around. But they’re just not enough.”
–Richard Trauger, chief scientific officer at CytoDyn
‘Why was the immune system not effective at controlling this virus, unlike other self-limited viral illnesses that we get?’”
Antiretroviral therapies now in use have been successful at suppressing the virus but do not eradicate the virus from the body. Drugs are designed to attack the virus once it’s invaded healthy cells by affecting enzymes the virus needs to complete its lifecycle. Drug resistance, adverse side effects and toxicities from long-term use remain challenges to managing patients’ care with pills.
Old Science, New Approach
One aspect of Jacobson’s research focuses on an alternative antibody-based approach to treating HIV infection. Antibodies, also called immunoglobulins, are proteins that circulate in the blood stream. They are a natural part of the immune system, helping fight off foreign pathogens that cause disease. When HIV antigens enter the body, the immune system activates white blood cells to create and send out HIV-specific antibodies.
Early antibody-based HIV studies conducted by Jacobson involved collecting hyper-immunoglobulins from the blood of healthy patients and using them to treat patients with more advanced disease. An established practice for more than 100 years, this was an attempt to neutralize the virus. Later, single antibodies with more specific, targeted activity against HIV were constructed. If the antibodies proved effective, it could lead to new vaccine candidates.
This line of research, Jacobson says, evolved into looking for antibodies capable of inhibiting the virus from attaching to and getting inside new cells. HIV antigen can only adhere to a host cell’s outer surface membrane at certain receptor points. By coating these molecules with special antibodies that block HIV—without impairing the receptor’s ability to otherwise function—antibodies essentially work like the lock on the front door, denying HIV the key to gain entry to the cell where it can replicate.
Unlike drugs, which can be swallowed, therapies that use antibodies must be delivered either intravenously or subcutaneously. One of Jacobson’s NIH studies is a Phase II-b clinical trial to optimize the dosing regimen of a novel monoclonal antibody called Pro140. Three initial clinical studies led by Jacobson showed it to be as antiviral as the best oral agents currently in use. Because it’s a molecule produced by the body itself, it’s also less toxic. The most innovative feature of Pro140, Jacobson says, is that it’s longer lasting than drugs currently on the market. One dose of Pro140 was shown to decrease viral loads for at least one to two weeks.
For HIV-infected patients who struggle to take the daily regimen of antiretroviral pills, Pro140 could be a game changer, Jacobson says. The Centers for Disease Control and Prevention estimated that less than 30 percent of the 1.2 million HIV-positive Americans have been diagnosed and treated successfully to the point where their viral loads are undetectable. The main challenge to achieving this clinical result is patient adherence to taking the medication daily as prescribed.
There can be many reasons for non-adherence. In his experience treating HIV patients, Jacobson says, most are young and they struggle to think of themselves as having a chronic disease. Taking a cocktail of pills every day is a reminder that they are different from others. Within the HIV population are subgroups that have particular difficulties, including intravenous drug users and those abused as children.
“It’s hard for anyone to take all their medications all the time but these are people who live disorganized lives to begin with, and that’s how they got infected in first place. They are not necessarily motivated to take care of themselves,” he says.
Stopping the Spread of HIV
Easing the burden of treatment is critical to controlling the spread of HIV because those who engage in high-risk behaviors are at especially high risk of transmitting the virus to others, says Richard Trauger, a former chief scientific officer at CytoDyn, which is hoping to bring Pro140 to market.
“If we can keep people on the therapy, even if they drift off and don’t take their pills, we’ve still got coverage and we’re managing this disease better from an epidemiological perspective,” he says. “Pills have really penetrated the market. We’ve seen what they can do and they’ve saved lots of lives and they’ve been really phenomenal at turning the epidemic around. But they’re just not enough. You can’t give them another pill to solve the [adherence] problem.”
Additional research on Pro140 will explore whether it potentially could be used to block new infections in people for short periods of time, a concept called protective immunity, Trauger says. The earlier clinical studies led by Jacobson show P140 antibodies can remain on cells targeted by HIV for up to 45 days.
During Jacobson’s other NIH Phase II clinical trial, 76 HIV-infected patients who abuse substances and have not been successfully treated with oral drugs will receive a standard drug regimen plus a dose of P140 or a placebo to determine if P140 improves the antiviral response. Researchers will monitor the patients for six months to see if their viral loads reach non-detectable levels.
“Now there’s even more interest in going for a so-called cure,” Jacobson says. “I think the most realistic approach is to go for a functional cure where you don’t fully eradicate the virus, because that’s going to be a tall order.”
Making People Sicker, to Make Them Better
Meanwhile, the search for an effective vaccine continues. Developing a universal HIV vaccine has proven elusive, in part, because there are many different varieties of the virus.
In an immune system-based intervention Jacobson led through the national AIDS Clinical Trial Group, patients whose viral loads had been stabilized with antiretroviral drugs were exposed to their own virus for a short period of time and were asked to stop taking the drugs. This essentially tricked the immune system into fighting a “new” infection. The process was then repeated several times. By monitoring dropping viral loads until they reached a new, hopefully lower set point, researchers were able to gauge for the first time the effectiveness of this and other immune-based approaches.
The results were encouraging. Those who were “pulsed” with their own virus achieved modestly lower viral set points. And about 15-20 percent of the treated group attained near undetectable levels—and stayed there for at least a year. Inducing the immune system to control the virus on its own without the need for antiviral drugs would achieve what has been called a “functional” cure.
“The immune system is not really set up to chronically react to an antigen. It’s set up to see an invader, deal with it and then create memory cells for when it happens again. Otherwise it goes to rest,” Jacobson says. “We thought exposing them again to their own virus for a brief period of time, then treating them to ‘slam down’ the virus would be a way to pulse the immune system without exhausting it too much.”
In another NIH study, Jacobson’s lab is using this new tool of monitoring viral set points to explore the idea of taking samples of a patient’s virus and using it to create a personalized vaccine. First, researchers take blood samples from HIV-infected patients before they are put on antiretroviral therapies. The samples are stored while the patient is treated. Once the virus is suppressed, white blood cells called dendritic cells are harvested from blood samples of HIV-infected patients through a lab process called leukapheresis. In a normal immune response, dendritic cells act to communicate the presence of a foreign antigen to other immune cells which then attack it.
“Dendritic cells are like the guards outside the castle; they signal to everyone else how to respond when there’s an invader,” Jacobson says. “They’re also known as nature’s adjuvant because they boost the response of the immune system to what’s attacking the body.”
By loading the RNA genetic material of the virus onto these active dendritic cells in the lab and transplanting them back into the person’s bloodstream, researchers hope to trigger a stronger, natural immune response, similar to the way vaccines work, but with active disease. This same approach was recently approved to treat prostate cancer, and other research groups are looking at dendritic cell-based vaccines for other types of cancer.
According to the National Institutes of Health, PRO140 is an investigational drug included in the entry inhibitor drug class for the treatment of HIV infection. Entry inhibitors interfere with the first step in the HIV life cycle—binding and fusion to target cells. By preventing HIV from entering target immune cells, entry inhibitors stop HIV from replicating and reduce the amount of HIV in the blood.
‘An Amazing Roller Coaster Ride’
As promising as the research appears, only one HIV-positive adult—the so-called Berlin patient—has been considered functionally cured of the disease; that patient received a bone-marrow transplant for leukemia from a donor genetically resistant to HIV infection, but such treatment is cost-prohibitive and unlikely to be replicated en masse. Meanwhile, in another medical first, doctors announced that a 2-year-old Mississippi child born with HIV and treated aggressively with a full regimen of antiretroviral drugs starting just after birth had also experienced a functional cure. The child had been off drugs for a year with no sign of active virus.
The news was promising, but as Jacobson points it, the baby’s infection may not have been established yet and the drugs may have merely prevented, and not actually treated, the infection.
“Both cases represent situations that are highly unusual and not typical of the average HIV-infected person. Nevertheless, they provide opportunities to advance our knowledge of the mechanisms underlying persistence of HIV infection, knowledge that could help guide the testing of strategies to cure the infection,” Jacobson says.
Each major breakthrough helps rekindle the hope he first felt 30 years ago of helping to find a cure. Great progress has been made in our knowledge and in developing effective treatments for HIV infection.
“It’s been an amazing roller coaster ride. There were a lot of ups and downs and a lot of struggles getting patients the care that they needed, helping them deal with the discrimination and stigma,” he says. “There were a lot of challenges but also many rewards. To have my career span from my training at the beginning of it all to now is amazing.”