On the World AIDS day the 1st of December a research team from the Western University in Canada announced the successful completion of the phase I trial of the AIDS vaccine they had developed against the HIV. The research team is now ready to start the phase II trail next fall where they are going to test this vaccine in 600 HIV negative subjects across North America. As published in the Retrovirology Journal the the vaccine had been tested in 33 HIV positive patients and the results show that the vaccine is both safe for use and effective in triggering an anti-HIV immune response in HIV-positive patients. The results demonstrate that the vaccine was well tolerated with no serious adverse events and can now proceed to Phase II.
The vaccine named SAV001 uses killed whole HI Virus 1 just like in polio, hepatitis A and rabies vaccines. According to the Western University press release the killed HIV-1 is genetically engineered so it is less dangerous and can be produced in large quantities. The vaccine is the world’s first preventative HIV vaccine using genetically modified killed whole-virus to receive approval by the United States Food and Drug Administration (FDA) to proceed to this phase of human clinical trials.
Chil-Yong Kang a professor in the Department of Microbiology & Immunology at Western and the head of the research team speaking to the Western University website says “The trial demonstrated that our vaccine stimulates broadly neutralizing antibodies that will neutralize not only single sub-types of HIV, but other sub-types, which means that you can have the vaccine cover many different strains of the virus.”
“If we can show that this vaccine is effective in preventing people from contracting HIV, we can stop the AIDS epidemic and that would be tremendous,” said Kang. “It would be a tremendous contribution to humankind, and it would make all of our efforts worthwhile.”
After the phase II the trial will enter the phase III in which the Vaccine will be tested using 6000 individuals across the globe in order to test it’s effectiveness against the virus.
Why it’s too difficult to develop Vaccine against HIV?
Scientists around the world tried to develop a successful vaccine for HIV for years, but failed due to many reasons. In 2005 pioneering HIV scientist Robert Gallo summarized the factors that go against the development of Vaccine for HIV.
He said HIV vaccine development was difficult because of the following factors:
- An HIV vaccine cannot consist of attenuated, actively replicating (live) HIV, due to possible reactivation.
- Killed whole virus (like the polio vaccine) might also be dangerous because one could not be sure one has killed all viral particles. A killed whole virus vaccine had also worked poorly in animal studies.
- There were successful vaccines that use sub-units of viruses such as individual proteins: an example was the hepatitis B vaccine. However medical science was less experienced with them.
- There is no truly useful small animal model for studying HIV infection and vaccines had to be developed in monkeys using SIV or the artificial monkey/human virus SHIV in monkeys, which did not have exactly the same immune effects as HIV.
- We do not know with certainty which immune response will provide protection; this is a major problem. Pre-efficacy studies of vaccines in monkeys and humans used correlates of immunogenicity such as CD8 cell response, but we do not know whether this immune response is in fact a correlate of efficacy.
- We have never before attempted to develop a vaccine against a retrovirus like HIV. Retroviruses, by integrating their genome into ours, are able to hide completely from immune surveillance within quiescent lymphocytes. This means that any vaccine has a small window of opportunity in which to prevent infection and would have to be extremely effective, repelling all attempts by HIV to attach to and infect host cells.
- HIV produces viral proteins such as tat and vif that actively interfere with what would otherwise be a potent anti-HIV response in both infected and uninfected cells.
- CD8 cellular vaccines do not block infection because they act at too late a stage, so, if they worked, would do so by reducing the viral load in chronic infection. They would not necessarily reduce the peak level of viraemia in the early burst of viral reproduction and might not control infections transmitted by people in acute infection.
- HIV is capable of developing immunity to the CD8 cellular response.
But despite all these barriers scientists around the world kept their battle against HIV and AIDS and this news from Canada is one such effort.
Source – Western University Website
