Five Quarts_ A Personal and Natural History of Blood - Bill Hayes [110]
The company has been in a similar precarious spot before, as Barnett recollected. Back in 1994, when she’d arrived at Chiron from Jay Levy’s lab, the first generation of AIDS vaccines was about to enter Phase II trials, in which efficacy is tested. Under study was not only Chiron’s vaccine but also vaccines developed by other pharmaceuticals, all employing a similar design: the use of a single small part of the “envelope” of the virus.
“And they didn’t go,” Barnett recalled. Indeed, based on dismal Phase I results, the government pulled the plug on this approach to vaccine creation, deeming it hopelessly ineffective.
“That was a pivotal moment,” she told me. “Everybody retrenched and started doing more research.” Her voice had grown sober in the memory. What was a major setback for companies such as Chiron was also a devastating blow to communities and individuals affected by the epidemic. So, yeah, I agreed with Susan, 1994 was not a banner year.
Chiron’s latest, best hope is as different from the failed version as a hybrid car from a 1970s gas guzzler. “We’ve combined everything we have, our best weapons: DNA technology plus protein technology,” Barnett explained, her enthusiasm renewed. The vaccine, designed to protect uninfected people, is administered in two parts. First a series of “prime” immunizations, which is the DNA aspect of the vaccine, at zero, four, and eight weeks, followed by the protein “boost,” probably at twenty-four and thirty-six weeks. A promising concoction is only the beginning of a good vaccine formula, I was coming to realize. The true finesse comes with the administering and the dosing. As Barnett described the protocol, I couldn’t help but hear an echo from Jay Levy. “Vaccinology is an art,” he’d said to me. And now, standing before me, dry-erase marker in hand, was an artist.
At this point Barnett dived into a finer presentation of the relevant mechanisms, complete with visuals, all the while checking in with me with a look: Okay? Okay? Still with me? Although phrases such as trimeric proteins, polymer microparticles, and occluded loop whizzed past me like bullets in a Yosemite Sam cartoon, I had no trouble grasping the principle upon which the vaccine’s potential success rests, an immutable, biological truth: Blood remembers illness.
Existing within our bloodstreams is an elite class of white blood cell—they can be either B or T cells—whose prime function is to retain a “memory” of infectious organisms the body has previously encountered. Should one of these organisms return, memory cells, as they are called, recognize it and rally fellow B and T cells to fight off the invader. This is why we do not get chicken pox a second time.
Memory cells are a vaccinologist’s ally because they can be tricked. A vaccine, in other words, can plant false memories. If Chiron’s AIDS vaccine is a success, it will convince memory cells that they’ve already encountered HIV when they have not. (Chiron’s product contains a noninfectious facsimile of portions of the virus.) If a vaccinated person is then exposed to actual HIV, the memory cells will, in theory, initiate a massive immunological response, killing the virus. This expectation is fairly well grounded. The immune system’s “secondary response” is usually faster, larger, and more specifically tailored than the first, or primary, immune response. And, again, in theory, the protection should last. Unlike suppressors, killers, and other white blood cells, memory cells live for decades before dying.
Those are some pretty big ifs, I had to admit to myself, especially since HIV can mutate so rapidly and hides so well in the body. It takes only one—just one—infected T cell to restart a cascade of viral replication. “So,” I asked Susan, “what does your gut say?”
“I think we’re going to get good immune responses. That’s my gut. And yet,” she added, “I’m not stopping research until I see some human data.” Even in the best-case scenario, she noted, it would be six to ten