The embattled OECD Conference in Genoa announced a $1.2 billion package to help combat AIDS in the Third World. Vaccine developers and United Nation agencies are pushing for large-scale clinical trials of AIDS vaccines in vulnerable Third World populations ravaged by the AIDS pandemic. AIDS virologists point to evidence that the vaccines are not only ineffective but dangerous. Dr. Mae-Wan Ho reports.
The culprit viral gene The intended vaccines all contain gp120, a glycoprotein (protein decorated with side-chains of carbohydrates) belonging to the envelope of the human AIDS virus, HIV-1. The candidates include recombinant HIV proteins and peptides (subunit vaccines), HIV-1 or SIV (the monkey AIDS virus), killed or 'attenuated', ie, rendered harmless by successive passage in cultured cells, and a wide range of recombinant viral, bacterial and plasmid vectors expressing HIV proteins. HIV researchers Dr. Veljko Veljkovic and his colleagues in Belgrade Yugoslavia, have shown that the gp120, is similar to the part of human immunoglobulin (antibody) proteins (Ig) involved in binding foreign antigens, a crucial step in the immune response. Thus, any AIDS vaccine containing the gp120 glycoprotein or the gene coding for it could strongly interfere with the immune system and make the host more vulnerable to the virus. And in the longer term, it could accelerate disease progression in HIV patients that do not yet have symptoms. But the gp120 gene has other properties that pose an even greater threat to the vaccinated population. It contains 'recombination hotspots' similar to those in bacteria and viruses such as Haemophilus influenzae, Mycobacterium tuberculosis, hepatitis B virus and herpes simplex virus, that often co-infect with the HIV, and also similar to recombination elements found in immunoglobulin genes and oncogenes (genes associated with cancer) in the human host. Recombination hotspots are breakpoints at which genetic exchange or recombination occurs much more frequently than usual. Recombination of HIV with bacteria and viruses would generate new pathogens. Within the human host, recombination with human genes would promote chromosomal rearrangements and formation of abnormal immunoglobulins, thus undermining immune responses. HIV-1 sequences integrated into the genome can act as retrotransposons (jumping genes) that can mutate genes by jumping into them, and some of the mutations may trigger cancer [1].
Dr. Veljkovic's team, in collaboration with researchers in UK, Italy and US, already found evidence of recombination between gp120 and a gene from Haemophilus influenzae [2]. Recombination between an HIV gene and Mycoplasm fermentans has been implicated in 'Gulf war syndrome' [3] affecting a high proportion of soldiers from United States and the United Kingdoom who served in the Gulf war. A new subtype of HIV-1 may also have resulted from recombination between HIV- 1 and SIV [4].
The proponents of the AIDS vaccination trials argue that the desperate situation precipitated by the AIDS epidemic justifies acceptance of the 'small risks' involved. But Veljkovic and his colleagues have written a monograph documenting the lack of efficacy of the vaccines and the enormous risks involved [5].
In 1994, the AIDS Research Advisory Committee of the US National Institutes of Health (NIH) recommended that phase III clinical trials of gp120 vaccines should not be conducted 'at this time and in this country'. The reasons, according to Dr. A. Fauci, director of National Institute of Allergy and Infectious Diseases (NIAID), were that the vaccines were ineffective; and there was a remote chance that the vaccines would compromise the immune system and make the recipient more vulnerable to infection [6]. The possibility that a vaccinated individual runs a greater risk of developing an established infection, or of progressing to disease more rapidly once infected, was confirmed subsequently [7]. The recombinant gp120 subunit vaccine tested in HIV-negative individuals was ineffective in protecting them against infection. Those who became infected during or after vaccination actually had in their blood sera significant levels of antibodies against the vaccine before they became infected, but those antibodies failed to protect them from infection. On the contrary, the vaccine appeared to have acted as a decoy to fool the immune system into mounting an attack on it, while allowing the HIV itself to slip through the host defence to get established. This subunit vaccine is due to go on Phase III clinical trial in Thailand.
The safety concerns for the individual is bad enough. But it is the effect on vulnerable populations that really worry Veljkovic and his colleagues, especially from the live recombinant viral and bacterial vector vaccines (see box).
| Live recombinant viral and bacterial vector AIDS vaccines | |
| viral vector vaccines Vaccinia virus Canarypox virus Fowlpox virus Influenza virus Polio virus Venezuelan equine encephalitis virus Rabies virus Adenovirus Hepatitis B virus Herpes simplex Epstein-Barr virus Coxsackie virus Atennuated HIV-1 Vesicular stomatis virus Alfaalfa mosaic virus | bacterial vector vaccines Escherishia coli Sallmonela Shigella Mycobacterium bovis BCG Streptococcus gordonii Listeria monocytogenes |
Many viral and bacterial pathogens are being used as vectors, and a number are currently considered promising AIDS vaccines. But they are also promising candidates for generating new infectious agents.
The AIDS vaccine based on live Salmonella vector was developed by the International AIDS Vaccine initiative (IAVI) in partnership with the US- based Institute of Human Virology (IHV) of the University of Maryland and the Uganda Ministry of Health. The development of the 'disarmed' Salmonella vector expressing HIV-1 gp120 and gp120- derived peptides was started in the early 1990s.
The Salmonella vector expressing HIV envelope proteins has been tested in 37 people in a phase I trial by NIAID. Uganda will be the first country in Africa to host a clinical trial of this vaccine. The only safety concern, it seems, was to ensure that the vaccine did not induce Salmonella disease (ie, diarrhea) in participants [8]. Whereas, Veljkovic stressed, the right safety question should be: 'Is the probability for transfer of HIV's genetic material from recombinant Salmonella vector to other pathogens equal to zero?' To which the answer is an emphatic no. Salmonella has the same kinds of recombination hotspots (called 'Chi') that are present in gp120, and is known to exchange blocks of genes with E. coli and other bacteria. The potential is rife for generating new pathogens by recombination between the Salmonella vaccine and diverse endemic infectious bacteria in Africa.
The Venzuelan equine encephalitis vaccine trialed in South Africa
An AIDS vaccine based on the live Venezuelan equine encephalitis (VEE)
virus vector, developed jointly by South Africa and the United States,
was due for phase I clinical trials early this year, moving on to large
trials lasting several more years. The country hoped to make a vaccine
against AIDS generally available by 2005. According to a spokesperson
of the Medical Research Council of South Africa, a successful vaccine
has the potential to save 20 million lives during its first decade of use. The VEE vaccine was developed by the University of North Carolina
at Chapel Hill with five-year federal funding from NIAID totally more
than $12 million.
The stated advantages of the VEE vaccine, according to the developers,
are that it targets cells in the lymph nodes, and that 'unlike
vaccinia virus, poliovirus, adenovirus, herpesviruses and influenza
virus-based vaccine vectors, most of the human population have never
been exposed to VEE. Therefore immunisation to HIV with a VEE-based
vector would not be restricted by preexisting immunity to the vector
itself' [9]. Unfortunately, that is not the case.VEE virus is carried by arthropods, and it is endemic in northern South
America, Trinidad, Central America, Mexico and Florida; and eight
different VEE strains have been associated with human disease. These
agents also cause disease in horses, mules, burros and donkeys. Natural
infections are acquired by bites from a wide variety of mosquitoes. The
same virus was also developed as a biological weapon by the US in the
1950s and 1960s.
A herpes simplex viral vaccine shows promise in non-human primates A modified herpes simplex virus (HSV) that invades host cells and expresses protein from the SIV has been developed by researchers in Harvard University into a live attenuated AIDS vaccine, which show promise in non-human primates. They claim that 'HSV vectors show great promise for being able to elicit persistent immune responses and to provide durable protection against AIDS' [10]. The same research team has also developed an HSV-2 vector based on another herpes virus responsible for genital herpes, with the expectation that this vector could serve a double role as vaccine for HIV as well as genital herpes.
Unfortunately, the HSV genome contains the greatest number of Chi recombination hotspots of all the microorganisms listed. It also contains Ig class-switch sequences (also recombination hotspots) and other sequences involved in the genetic rearrangements that take place in producing human immunoglobulin genes in blood cells. High levels of recombination have already been identified in the HSV genome associated with these hotspots.
A vaccinia virus vaccine led to disease and death Among the first AIDS vaccine with live viral vectors which was tested in humans was a recombinant, highly attenuated vaccinia virus expressing HIV-1 proteins. The vaccinia-gp160 vaccine was developed by Bristol-Myers-Squibb who performed the preclinical study in the period 1985-1988. The phaseI/II research began in 1988 and was dropped in 1993, then continued for an additional year. These studies combined the vaccinia-p160 vaccine with gp160 or gp120 vaccine developed by MicroGeneSys, Chiron, Genetech, and Immuno AG. Unfortunately, a recombinant HIV-vaccine virus arose from the attenuated live vaccine, which was harmful for the immune compromised individuals, producing symptoms of progressive vaccinia and death [11]. There was also the danger that the recombinant virus could spread and harm other persons with AIDS.
A canary pox vaccine trialed in Uganda, Haiti, Trinidad and Brazil Another poxvirus was used, the canarypox virus. When the canarypox virus carrying HIV genes infect human cells, the cells make proteins from the genes and package them into HIV-like particles called pseudovirions that are non-infectious. These trigger the host immune response against HIV. The first such canarypox viral vaccine carrying the HIV-1 gp160 gene was developed by Pasteur-Merieux-Connought and, in combination with Chiron's gp120 construct. It entered phase II trial in the US in 1997.
The first phase I trial of a canarypox vaccine in Africa was launched early in 1999. It was tested for safety and immunogenicity in Ugandan volunteers, and to reveal the extent to which immunized Ugandans have cytotoxic lymphocytes that are active against the subtypes A and D of HIV, which are prevalent in Uganda. The vaccine was planned to enter phase I/II trials in Haiti, Trinidad, and Brazil during 2000. Is canarypox virus safer than vaccinia virus? Most probably not. Both are orthopox viruses and are rich in recombination hotspots. This family of viruses is widely distributed, and recombination between different poxviruses can readily take place. Recombinants have arisen that are more virulent than either parent, and it is impossible to predict the fate of released canarypox vaccine with HIV genes. The use of these vaccines in Africa where monkeypox is endemic is likely to generate recombinants with unpredictable pathogenicities. Monkey pox is transmitted from human to human, but the natural virus is relatively harmless. Could a recombinant virus arise that may be as virulent as the smallpox virus?
Finally, AIDS vaccines based on HIV antigens produced in plants are also being developed. The tobacco mosaic virus, TMV, has been used as a vector to express recombinant coat protein of alfafa mosaic virus (AIMV) containing antigenic peptides from the rabies virus and HIV-gp120 [12]. There have already been many examples of recombination between viral coat proteins in transgenic plants and infecting viruses [13]. In addition, there is also evidence that a plant virus has switched host to infect vertebrates and recombined with a vertebrate virus [14].
According to the WHO report 2000, more than 90% of all AIDS cases are in developing countries. UNAIDS and NIH are the two most important organizations involved in developing AIDS vaccines. UNAIDS Executive Director Peter Piot has declared, 'It is our collective responsibility to ensure that all vaccine trials are conducted under the strictest possible ethical and scientific standards.' But Dr. Veljkovic has shown that current vaccines based on HIV-1 gp120 can harm the immune system of individuals and, on account of its recombinogenic tendencies, has the potential to generate deadly viruses and bacteria that can spread through the vaccinated populations and to wild life. The intended vaccine trials are in serious breach of ethical, scientific and safety standards.
AIDS, more so than other diseases, cannot be addressed simply by vaccinations, even if efficacious and safe vaccines could be found. More than drugs and vaccines, we need to end poverty, malnutrition and environmental destruction, to reinstate social equity and free access to primary healthcare and education.
A UN body to monitor and control GM experiments Dr. Veljkovic is calling for the formation of an ' organization which could pick up information concerning all laboratories performing GM experiments, like [the] International Atomic Agency which control all nuclear experiments and activities around the world'. That should be the task of the International Biosafety Clearing House.
Article first published 29/07/01
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