GeoVax Trial Results Establish a New Benchmark for Preventative HIV Vaccine Model

ATLANTA, June 8, 2011 /PRNewswire/ -- GeoVax Labs, Inc. (OTCQB/OTCBB: GOVX) announced today the publication of the results of preclinical testing of a simian prototype of its 2nd generation HIV/AIDS vaccine. The article, titled "Prevention of Infection by a Granulocyte-Macrophage Colony-Stimulating Factor Co-Expressing DNA/Modified Vaccinia Ankara Simian Immunodeficiency Virus Vaccine," will appear in the July 1 issue of The Journal of Infectious Diseases. A PDF of the article can be obtained at the following URL:

http://jid.oxfordjournals.org/content/204/1/164.full.pdf+html

The publication compares the level of prevention of infection against repeated rectal challenges of simian prototypes of the GeoVax HIV/AIDS vaccine in the presence and absence of granulocyte-macrophage colony-stimulating factor (GM-CSF).  In this non human primate study, the highly beneficial activity of the GM-CSF was shown by 70% of the group receiving the GM-CSF co-expressing DNA vaccine resisting infection.  GM-CSF is a growth factor that recruits and matures immune system cells that are specialized for initiating immune responses. GM-CSF was co-expressed in the DNA prime for the recombinant MVA boost. Animals were given two DNA immunizations, either expressing or not expressing the GM-CSF, followed by two MVA immunizations.  The ability of the two vaccine regimens to prevent infection was then tested by administering 12 weekly rectal challenges with a dose of virus that infected 30% of unvaccinated animals at each challenge. All of the unvaccinated animals became infected.  

The co-expression of the GM-CSF enhanced the ability of vaccine-elicited antibodies to bind to the envelope protein that mediates entry into cells.   This enhanced binding activity correlated with the prevention of infection.  The animal with the least tightly binding antibody was the first to be infected, whereas all animals with binding indices above a certain level were protected against infection.  Antibody is produced by the immune system in response to infections (or vaccines).  It is a clothespin shaped protein that specifically recognizes and blocks microbes, preventing infections. "Having an antibody activity that correlates with the prevention of infection is an enormous step forward for the development of HIV/AIDS vaccine," said Dr. Robinson, Chief Scientific Officer of GeoVax.  "If one does not have an effective antibody, the vaccine has to rely on T cells that recognize and kill infected cells.  T cells can control infections, but they do not have the power that antibodies have to prevent infection.  The GM-CSF provided the edge for our vaccine to elicit antibody that could tightly bind to virus." Other prototype vaccines have not achieved the same level of prevention in non-human primates.  Thus, the GM-CSF adjuvanted GeoVax prototype has established a new standard for prevention of infection.

As recently announced, the GM-CSF co-expressing version of the GeoVax HIV vaccine is entering human trials through the NIH supported HIV Vaccine Trials Network (HVTN).  The protocol, HVTN 094 will test two inoculations of the GM-CSF expressing DNA vaccine followed by three inoculations of the MVA vaccine. The DNA vaccine co-expresses GM-CSF and non-infectious HIV-like particles.  The MVA vaccine expresses non-infectious HIV-like particles, but does not express GM-CSF. "We are optimistic that the vaccine will prove as effective at preventing HIV infections in humans as the SIV prototype was in non human primates" said Dr. Robinson.  "The rectal challenges used in the simian model represent 30 to 300 times  higher doses of virus than are experienced during typical HIV transmissions in humans," said Dr. Robinson.

About GeoVax Labs, Inc.

GeoVax is a biotechnology company developing human vaccines for diseases caused by HIV (Human Immunodeficiency Virus – that leads to AIDS) and other infectious agents. Our goals include developing HIV/AIDS vaccines for global markets, overseeing the manufacture and testing of these vaccines under GMP/GLP conditions (FDA guidelines), conducting clinical trials for vaccine safety and effectiveness, and obtaining regulatory approvals to move the product forward. GeoVax's vaccines are unique in expressing virus like particles that display the trimeric membrane bound form of the HIV-1 envelope glycoprotein. All preventative Phase 1 human clinical trials conducted to date tested various combinations and doses of our DNA and MVA vaccines, their ability to raise anti-HIV humoral (antibody) and cellular (cytotoxic T cell) immune responses, as well as, the vaccines' safety. Successful results from Phase 1 testing supported the initiation of the first Phase 2 testing. GeoVax's Phase 2 human trial began in January 2009 and will ultimately involve 300 participants at sites in the United States and South America. Recently GeoVax began enrolling patients in a Phase 1 therapeutic trial for individuals already infected with HIV. For more information, please visit www.geovax.com.

Forward-Looking Statements

Certain statements in this document are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act These statements are based on management's current expectations and are subject to uncertainty and changes in circumstances. Actual results may differ materially from those included in these statements due to a variety of factors, including whether: GeoVax can develop and manufacture its vaccines with the desired characteristics in a timely manner, GeoVax's vaccines will be safe for human use, GeoVax's vaccines will effectively prevent AIDS in humans, vaccines will receive regulatory approvals necessary to be licensed and marketed, GeoVax raises required capital to complete vaccine development, there is development of competitive products that may be more effective or easier to use than GeoVax's products, GeoVax will be able to enter into favorable manufacturing and distribution agreements, and other factors, over which GeoVax has no control. GeoVax assumes no obligation to update these forward-looking statements, and does not intend to do so. More information about these factors is contained in GeoVax's filings with the Securities and Exchange Commission including those set forth at "Risk Factors" in GeoVax's Form 10-K.

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Investor Relations
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SOURCE GeoVax Labs, Inc.

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