Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis (TB), is an intracellular bacterial pathogen that kills approximately 1.7 million people each year and infects one-third of the world's population. The most-widely used vaccine in use today is BCG, which is a live avirulent variant of M. bovis, a closely related species that causes tuberculosis in ruminants. BCG administration to an immunosuppressed individual can disseminate and lead to serious life-threatening infection. This inherent safety ris remains in second- generation BCG vaccines modified to express Mtb antigens and/or factors that imbue the bacteria with enhanced survival inside host cells. Thus, there is a need for a safe and more effective TB vaccine. In this proposal, we seek to develop a novel TB vaccine based on parainfluenza virus 5 (PIV5), a respiratory virus. Parainfluenza virus 5 (PIV5), a paramyxovirus, is thought to be a contributing factor for causing kennel cough and is not known to cause any illness in humans. Several characteristics of PIV5 make it an attractive vaccine candidate vector. First, kennel cough vaccines containing live PIV5 have been used in dogs over 30 years. Humans are likely exposed to this virus due to close contact to dogs. Yet, no recorded illness in humans has been associated with the virus. Second, it can be produced in high titers in many cells including Vero cells that have been approved for vaccine production. Third, PIV5 can infect human cell lines and primary human cells. Fourth, in our recent study, we have found that pre-existing immunity against PIV5 does not negatively affect immunity generated by a PIV5-based vaccine. Fifth, PIV5 expressing NP, an internal protein of influenza virus, protected against lethal influenza virus challenge in mice. Since NP-mediated protective immunity relies on cell-mediated immunity, the results suggest that PIV5-based vaccine is capable of inducing protective cellular immune responses. Sixth, in a side-by-side comparison of PIV5 expressing HIV Gag protein (PIV5-gag) and a vaccinia virus (MVA) expressing Gag (MVA-Gag), PIV5-Gag induced better cellular immune responses than MVA-Gag in mice in our preliminary studies. Finally, the intranasal administration of PIV5 is a very good feature for eliciting robust mucosal immune responses, and thus ideal for vaccinating against respiratory pathogens. This vector has not previously been evaluated as an Mtb vaccine vector. We hypothesize that PIV5 as a live vector will induce immunity to prevent Mtb infection. In this proposal, we plan to demonstrate the proof-of principal for using PIV5 as a vector for Mtb vaccine development. We will focus our efforts on the following specific aims: generate and analyze recombinant PIV5 expressing Mtb antigens 85A (PIV5-85A) and 85B (PIV5-85B) and evaluate immunogenicity and efficacy of recombinant viruses in vivo. At the end of this study, we expect to have determined whether PIV5 expressing Mtb antigens are good Mtb vaccine candidates. If we identify efficacious PIV5-based vaccine candidates in this study, we will further test the candidates in more relevant animal models such as guinea pig and non-human primate. We also will continue to modify the viral vector to make the vaccine candidate maximally effective.
Mycobacterium tuberculosis (Mtb) is a major human health problem. Current vaccine has many shortcomings. There is a need for a safe and more effective TB vaccine. In this proposal, we seek to develop a novel TB vaccine based on parainfluenza virus 5 (PIV5).