Attenuated poxvirus vectors MVA and NYVAC as promising vaccine candidates against HIV/AIDS.

As yet, the only human infectious disease eradicated from our planet is smallpox, caused by variola virus a member of the poxvirus family. The vaccination success, with the declaration by WHO in 1980 of a worldwide free of smallpox, was largely due to the availability of a quite effective and stable live vaccine, as well as the restricted human host for virus infection. Variola was considered one of the most devastating diseases of human mankind. With the sudden appearance of the HIV/AIDS in 1981, an infection which spread rapidly to become a pandemic in a short time, causing up to date more than 22 million deaths, about 40 million people infected and a current incidence of about 3 million deaths per year, this dreadful pandemic has become one of the most severe diseases in the World, specially in poor countries. While different antiviral drugs have been developed that block virus replication at various stages of infection, however the rapid virus escape that follows during the drug therapy due to mutations, makes the development of vaccines the most secure option to control and eradicate the disease. Numerous vaccines have been developed, but to date the clinical trials have failed to show any efficacy against HIV infection. Due to the proven success of vaccinia virus in the control of smallpox as well as of poxvirus recombinants against veterinary diseases, a major effort has been directed to document the advantages of poxvirus vectors as vaccines against multiple diseases. Two of the most promising poxvirus vectors are the highly attenuated modified vaccinia virus Ankara (MVA) and the modified Copenhagen strain NYVAC. In this commentary I describe the biological characteristics of the attenuated poxvirus vectors, MVA and NYVAC, with emphasis in their application in HIV preclinical and clinical trials, and considerations as future HIV vaccines.