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Background:  Of the 40 million people currently living with HIV-1 infection or AIDS, 5 million are newly infected. These new infections occurred in countries that are poverty stricken, do not support sexual education and condom use, and are often adulterous and homophobic. Although, researchers strive to create an effective vaccine, there is no cure for HIV-1 infection. HIV-1-infected individual rely heavily on antiretroviral drugs to prevent HIV-1 infection from developing into AIDS. These drugs are extremely expensive; therefore many communities do not have access to these therapies. Due to the expense of antiretroviral drugs, inadequate condom usage, intolerance of sexuality, and new scientific insights, new innovative therapies are needed for prevention of HIV-1. There is an urgent need for agents that can block HIV infection at the primary sites of transmission, namely, gastrointestinal and urogenital mucosa. On the mucosal surface, there are native microbes (flora) that assist in several metabolic functions, inhibit growth and metabolism of foreign organisms, and act as the first line of defense for invasion through the mucosal surfaces. Unfortunately, HIV-1 can successfully elude the flora. If the flora are improved or genetically enhanced, they may provide an adequate line of defense against HIV-1 infection.

Methods:  Therefore, we propose to use genetically modified, commensal microbes that secrete anti-HIV-1 peptides for this purpose. We genetically altered the probiotic bacterial E. coli strain Nissle 1917 and the fungal S. boulardii strain Sb49 to enable both microbes to secrete HIV-1 fusion-inhibiting peptides. E. coli Nissle 1917 can express and secrete large quantities of HIV-1 fusion-inhibiting peptides fused to the carboxyterminal signal sequence of hemolysin A. S. boulardii also express HIV fusion-inhibiting peptides and secrete by route of the alpha-factor secretory pathway.

Results:  The secreted peptides from both organisms successfully prevent HIV-1 infection in vitro. Moreover, E. coli Nissle 1917 colonize the mucosal surfaces of the rectum, colon, cecum, duodenum, ileum, jejunum, and vagina in mice. Bacteria isolated from the feces of the mice several months after initial colonization contain Nissle 1917 that still secrete HIV-1 fusion inhibiting peptides.

Conclusions:  Genetically engineered probiotic microbes can successfully colonize the gastrointestinal and urogenital tracts, express and secrete HIV-inhibiting peptides.

Keywords: Microbe; mucosa; HIV