Viruses: More Friends Than Foes (Revised Edition). Karin Moelling
gene therapy of selected cells, perhaps viral vectors for treatment and reinfusion, and a second therapy to fight against “minimal residual disease”, left over cells, because no therapy works 100 percent. Who can pay for this type of research and later treatment — where? In Africa? Yet even a whole new journal Cure HIV was founded. A big hype. Another novel approach is to activate the virus in the patient’s reservoirs (by a drug Vorinostat) to make it accessible for therapies. This is being tested in a study called DARE — a meaningful acronym, because it sounds a bit risky first to increase the number of viruses in order then to kill them. Furthermore, the so-called “Elite Controllers” are being investigated to find out what mechanism can control the virus. They have special features in their immune system (HLA-B57), which may be exploited; this possibility is being explored in a study called VISCONTI (Virology and Immunology Study on CONtrollers after Treatment Interruption). A major simple message is: treat early!
No vaccine against HIV?
What is the result after 30 years of vaccine development? There is no vaccine and after so many wrong promises nobody dares to make any more predictions. When HIV was discovered, molecular biologists assumed that a vaccine could be produced immediately. The model was the hepatitis B virus (HBV), where a surface molecule induces antibodies that neutralize the virus, counteract its infectivity and prevent its replication. By analogy to HBV, the envelope sequence of HIV was selected as the basis for vaccine development, and the sequence was known within a few months. The DNA of the surface protein of HBV was then used to produce a protein in yeast or in bacteria by recombinant DNA technology — the first successful vaccine ever to be produced by this novel technology. However, this did not work out for HIV, even though it has some similarities with the hepatitis virus, HBV. The reason is that HBV is genetically more stable, and it carries an almost complete double-stranded DNA inside the virus particle, which does not change easily in contrast to the single-stranded RNA genome of HIV, which is so variable that all efforts to “capture” it have so far failed. The prediction of virologists was thus far off the mark that all the people involved are still ashamed of it, since the differences between hepatitis B virus, HBV and HIV were even then known to all researchers. The vaccines against the surface protein were at best capable of neutralizing the virus used in the test-tube, but not the viruses in real life, which do not consist of one species but of many different ones, the quasispecies, and furthermore can rapidly change.
An unintended “vaccination” took place in Australia when patients with a blood-clotting deficiency received supplementation with a blood product called Factor VIII. However, the product they received was contaminated with a virus that was defective and lacked an accessory gene of HIV, the pathogenicity (originally “negative”) factor Nef. This was a slowly replicating virus and would have been an ideal vaccine, as known from previous vaccines, e.g. the vaccine against poliomyelitis, an attenuated (slowly replicating) virus. That is one of the best designs for a vaccine. However, after a dozen years some recipients of the contaminated Factor VIII fell ill: the virus had reverted to a faster-replicating virus, replenishing the defective gene and causing the disease — to the great surprise of the virologists.
The surface protein has been analyzed down to its last possible detail, but so far without success. The virus needs this surface molecule to find its host cell. Therefore, surface molecules are still in the focus of attention. Today a new approach is being taken, exploiting the antibodies of long-term survivors, termed long-term non-progressors (LTNP) or elite controllers (EC). Out of the whole antibody reservoir of such an infected but resistant person, the antibodies that bind to the surface of HIV and neutralize it, to make it non-infectious, are selected in the laboratory. 200,000 antibodies were screened in a tour de force to select a few candidates, which are now under development for producing a novel vaccine.
An early large scale clinical trial, RV144, was performed in Thailand with 16,000 volunteers, and evaluated more than once, with always better interpretations, depending on the statistics between 2009 and 2015. The vaccine is a prime-boost combination of a canarypox virus vector (ALVAC) and gp120 viral surface proteins (from clades B and AE, as monomers not the trimers, it was not known initially that the coat protein naturally trimerizes, so this vaccine was not optimal). It reduced the risk of infection by 31%. The Bill and Melinda Gates Foundation is sponsoring a variation of this vaccine in Africa with 5400 volunteers (clade C) and predicts — or hopes for — success by 2030.
New technologies identify “broadly neutralizing antibodies” (bnAbs) with a new strategy. If one vaccine fails, maybe several of them will succeed — by sequential immunizations, though. The immune response could then be guided stepwise to develop special classes of antibodies to fight HIV — several sequential vaccines shooting at a moving target? Difficult. Adeno-associated virus (AAV) expresses the bnAbs in an ongoing clinical trial in the U.K. A vaccine “Ad-Env” is tested by Dan H. Barouch at Harvard with an adenovirus modified to express several HIV proteins (Gag, Pol, and Env) and a subsequent boost with the viral surface Env protein alone.
Then there is a “cheating approach” on the way. Instead of using the real viral surface protein one synthesizes a similar one as antigen, more immunogenic than the native viral surface Env, in the hope that antibodies will also recognize the native one better. This approach is known in animal studies (we also used it successfully), it may work but it is new for HIV. Now a “replicating” vaccine virus is going to be tested: remember, replicating viruses are the most efficient ones as vaccines — if they do not cause diseases. In this case the virus is a modified herpes virus CMV, so no intact HIV can arise from the vaccine again. Let us hope and wait — 15 years? 30 years?
“Naked DNA”
One day in the 1990s I received an unexpected invitation to Malvern, Pennsylvania, USA. I had earlier been an adviser there, for several years, for the company Centocor for the application of cancer genes in the diagnosis or therapy of cancer. The project now was a vaccine against HIV, and a spinoff of Centocor by the name Apollon was founded. I was supposed to direct the development of that vaccine and received an impressive business card as CSO, Chief Scientific Officer, for a very small team! I was on leave from the Max Planck Institute in Berlin for one week per month; my time at the computer was not recorded. The science was exciting: the goal was a naked DNA vaccine, a novelty then, whereby the muscle of a vaccinee is injected with DNA to produce parts of the virus, some proteins, simulating infection. This should lead to antibodies in the recipient as vaccine. The DNA was a complex combination of a variety of viral genes, amplifying genes, some of which originated from totally different other viruses or even bacteria. That is the playground of virologists but also the art — the secret lies in the selection, cutting and recombining genes to intensify certain properties and to avoid others, as modules of an artificial virus. That was the challenge. No intact pathogenic virus is allowed to emerge from the process. And in clinical tests, or the customs at the US border, it should be clear that the carrier has not been infected but only vaccinated.
While we were producing large amounts of the DNA, suddenly all samples, text-tubes and reagents were found to be contaminated with the DNA. There was a leak somewhere — until we could repair it in the safety laboratory, we were all already vaccinated through the air and our nose and lungs. The DNA was safe! It was further modified to a “dummy” so that it could not be stolen or imitated by competitors — a normal precaution in industry, but less so in a research laboratory — and new to me.
The DNA was then tested in some HIV-infected patients in Zurich. This was the first DNA-based vaccine in Europe. “Adverse events” did not occur in the patients within several years. (The most important thing was that the volunteers did not develop autoimmune responses.)
However, unexpectedly, the local immunologists at the University showed “severe adverse” behavior — maybe because we were invading their “territory”? I tried to co-operate before we started injecting the patients, but failed. I had initiated the project before I came to Zurich — still something to remember for others if one wants to avoid trouble.
After the injections