Bartonella is a bacterial pathogen that causes bacillary angiomatosis (BA) in HIV- infected patients. This condition is characterized by multiplication of blood vessels (angiogenesis) and the formation of tumor -like skin lesions, resembling cancer. If BA is not diagnosed and treated, it can cause death. More cases of Bartonella infection and BA in HIV -positive patients have been reported in San Francisco and California than in any other location in the world, so study of how this bacterium interacts with the AIDS virus is important to Californians and HIV- infected people who are at high risk for severe Bartonella infections. The ability of Bartonella to cause angiogenesis and BA is unique and not known for any other bacterium. Even after years of research, the way that Bartonella causes BA lesions is still unknown.

To study this angiogenesis process in more detail, we have developed a model that reproduces the manifestations of Bartonella (prolonged bloodstream infection and BA) that occur in humans co-infected with Bartonella and HIV. This model gives us two tremendous advantages: it allows us to:

1) follow the natural course of these BA lesions;

2) to study the BA lesions and how they form when a person is infected with both Bartonella and HIV at the same time.

We will also study how the Bartonella bacterium changes when it infects someone already infected with the AIDS virus, and how the immune system reacts to the Bartonella bacterial infection while trying to eliminate the Bartonella infection from the body. We believe that this project will provide knowledge about how Bartonella and HIV interact uniquely to cause the blood vessel tumors that are characteristic of BA lesions. An increased understanding of Bartonella pathogenesis will ultimately lead to potential strategies for improved treatment of Bartonella infection in HIV- infected patients. It may provide information about how cancer forms tumors of blood vessels (angiogenesis), as well.