Norwegian HIV vaccine-Very modest results seen in recent clinical trial
21 February 2012 -
Although HIV infection can be treated with combination therapy (commonly called ART or HAART), such therapy has at least the following
drawbacks:
- ART must be taken at least once a day for the rest of one's life
- ART has side effects
- ART does not cure HIV infection
- ART does not fully restore the immune system
- ART is expensive
Therefore, some scientists are undertaking the very difficult and long-term research that is needed to attempt to cure HIV infection.
Not hedging their bets-it may not be possible to cure HIV infection-other scientists are working on vaccines for HIV. Such vaccines fall
into two categories, as follows:
- a vaccine that can be given to HIV-negative people to protect them from infection
- a vaccine that can be given to HIV-positive people to help train their immune systems to fight HIV
These latter types of vaccines are called therapeutic vaccines.
The Norwegian biotechnology company Bionor Pharma ASA recently issued a press release about the results of its candidate
therapeutic vaccine called Vacc-4x. The placebo-controlled study was conducted to assess safety and preliminary efficacy in HIV-positive
people. Researchers had hoped that this vaccine would allow participants to have a prolonged interruption of ART with very low levels
of virus in their blood. This did not happen. However, the vaccine is safe and does stimulate the immune system.
How does it work?
The vaccine is made from four small molecules taken from an inner, or core, protein of HIV called p24. These molecules or peptides used
in the candidate vaccine cannot cause HIV. In some other studies, researchers have found that HIV-positive people who naturally produce
high levels of antibodies against p24 seem to have a reduced pace of damage to their immune system as a result of HIV infection.
Researchers first gave participants a small dose of the bone marrow stimulant GM-CSF (granulocyte-macrophage-colony-stimulating
factor; Leukine, sargramostim), as this can temporarily stimulate the formation of several types of cells, including dendritic cells (DCs).
The vaccine is then injected into the skin-the body's largest organ-where it is taken up by DCs. These cells serve to capture invading
germs and alert the rest of the immune system about them. Also, DCs can help amplify the subsequent reaction by the immune system to
invading germs.
When vaccinated with the peptides in Vacc-4x, DCs capture the peptides and take them to lymph nodes and lymph tissues.
There, DCs show other cells of the immune system the peptides and encourage them to attack p24 and, therefore, HIV and HIV-infected
cells. Ultimately, researchers hoped that the vaccine would coax the immune system into destroying HIV-infected cells and reduce
the burden of HIV in the body.
Study details
As we received word about the study via press release from Bionor Pharma ASA, we cannot provide our readers with the details that
we normally provide.
HIV-positive participants on ART were recruited from the following countries:
- Germany
- Italy
- Spain
- UK
- United States
Participants were randomly assigned to receive one of the following interventions in a 2:1 ratio:
- Vacc-4x - 93 participants
- placebo (fake vaccine) - 43 participants
For the first six months of the study, participants took ART. For the second half of the one-year study, participants stopped taking
ART and were monitored. If the amount of HIV in their blood during this second part of the study was very low, they were allowed to
remain free from therapy for up to 24 consecutive weeks.
Results
The corporation's latest press release suggests that 25 people who received placebo and 56 who received Vacc-4x completed the study.
The trial failed to fulfill its primary purpose: finding a significant difference between vaccine and placebo in the time that
participants were able to stay off ART. Details about this were absent from the press release.
When participants stopped taking ART, levels of HIV in the blood appeared to stabilize as follows:
- Vacc-4x - 23,000 copies/ml
- placebo - 62,000 copies/ml
This difference was statistically significant; that is, not likely due to chance alone.
This difference, while hinting that Vacc-4x may indeed have helped the immune system, needs to be understood in the context of HIV
treatment. Whatever impact Vacc-4x had on viral load, it did not allow recipients to remain off therapy longer than people on placebo.
These results are interesting but do not mean that Vacc-4x is suitable for approval by regulatory authorities in any high-income country
because the clinical benefit (time off therapy) was not significant.
In general, interrupting ART is fraught with risk. Without the suppression provided by drugs, production of HIV increases and the
spread of the virus resumes throughout the body. HIV also causes inflammation that damages many organs, including the following:
- brain
- heart
- kidneys
- liver
- lungs
The press release did not mention any changes in assessments of inflammation during the study.
Vaccine + lenalidomide
The corporation is considering an additional study of Vacc-4x together with the drug Revlimid (lenalidomide). This drug is chemically
related to thalidomide. Drugs such as lenalidomide and thalidomide appear to suppress inflammation and some immune responses. In theory,
such suppression may be useful in cases where there is excessive inflammation or inappropriate immune responses, such as occur in
cancers and HIV infection. However, these drugs carry the potential of weakening the immune system. Several clinical trials in
HIV-negative people have found an increased risk for developing other cancers in people who received lenalidomide. Therefore,
this drug needs to be used cautiously. Additionally, lenalidomide and thalidomide can cause fetal deformities and so their
use is not suitable in women who wish to become pregnant or in men who are trying to help women conceive, as researchers
do not know if these drugs are ejaculated.
The American Food and Drug Administration (FDA) is currently reviewing data on lenalidomide and will issue a statement once it has
completed its review.
Are two vaccines better than one?
Bionor has another HIV vaccine candidate called Vacc-C5. By giving HIV-positive people both Vacc-4x and Vacc-C5, the corporation hopes
that immune responses to HIV will be better. This will require a well-designed clinical trial.
The long road to an HIV vaccine
In 1983, Françoise Barré-Sinoussi, PhD, isolated HIV from the lymph node of an infected patient. Shortly after that time
researchers hoped that an effective vaccine against HIV would be quickly created. However, in the 30 years since the discovery of HIV,
researchers have struggled to create an effective vaccine. In part, this is because HIV appears to be unique among viruses, infecting
the immune system-the system that serves the purpose of protecting the body from infection. Shortly after it penetrates the wet
tissues of the anus and vagina and begins to infect cells, HIV quickly spreads to the lymph nodes and every organ, destroying
critical immune system cells and embedding itself so that it becomes very difficult to remove. Moreover, it causes continuing
dysfunction within the immune system, hampering its ability to clear this virus. Also, researchers are continually amazed
by the never-ending complexity of the immune system. Until they have a better understanding of how the immune system
works, particularly its interaction with HIV, they cannot create an effective vaccine.
Looking to the future
HIV vaccine research is inherently time consuming, complex and intellectually challenging. Although the results of Vacc-4x are
disappointing, Bionor should be praised for attempting such a difficult research program. If anything, the Bionor results should
stimulate other research teams to continue their work so that a better understanding of HIV's interaction with the immune
system can lead to drugs and therapeutic vaccines that can help HIV-positive people and to an effective vaccine to
protect HIV-negative people.
If we are to see a world free from the threat of AIDS, then we need to be conscious of the general complexity of vaccine research and
be patient with the efforts of immunologists and virologists who toil away in laboratories in Canada and around the world. Major funding
agencies such as Canada's CIHR (Canadian Institutes of Health Research), the American NIH (National Institutes of Health) and France's
ANRS (Agence nationale de recherches sur le sida et les hépatites virales) also need to demonstrate patience and give scientists
the long-term support they need for equipment and personnel so that they can learn more about how the immune system works.
In the future there will be news about other HIV vaccines and, in the short-term, likely very modest results. We should not be surprised
about that. However, such results can be used to improve future vaccines. We will one day have a world free from AIDS, but that day is not
yet here.
-Sean R. Hosein
REFERENCES:
- Bionor. Results for viral load on Vacc-4x. Press release . 15 February 2012.
- Asjö B, Stavang H, Sørensen B, et al. Phase I trial of a therapeutic HIV type 1 vaccine, Vacc-4x, in HIV type 1-infected
individuals with or without antiretroviral therapy. AIDS Research and Human Retroviruses . 2002 Dec 10;18(18):1357-65.
- Kran AM, Sommerfelt MA, Sørensen B, et al. Reduced viral burden amongst high responder patients following HIV-1 p24 peptide-based therapeutic immunization. Vaccine . 2005 Jul 1;23(31):4011-5 2005 Jul 1;23(31):4011-5.
- Kran AM, Sørensen B, Sommerfelt MA, et al. Long-term HIV-specific responses and delayed resumption of antiretroviral therapy after peptide immunization targeting dendritic cells. AIDS . 2006 Feb 28;20(4):627-30.
- Kran AM, Jonassen TO, Sommerfelt MA, et al. Low frequency of amino acid alterations following therapeutic immunization with HIV-1 Gag p24-like peptides. AIDS . 2010 Nov 13;24(17):2609-18.
- Food and Drug Administration. Revlimid (lenalidomide): Ongoing Safety Review - Increased Risk of Developing New Malignancies. Safety Information. 08 April, 2011. Available at: www.fda.gov/Safety/MedWatch/SafetyInformation/
SafetyAlertsforHumanMedica...
###
CATIE-News is written by Sean Hosein, with the collaboration of other
members of the Canadian AIDS Treatment Information Exchange, in Toronto.
From Canadian AIDS Treatment Information Exchange (CATIE). For more information visit CATIE's Information Network at http://www.catie.ca
Source: CATIE: CANADIAN AIDS TREATMENT INFORMATION EXCHANGE
|
