In a new paper published in the February issue of Vaccine, my VIRxSYS colleagues discuss the benefits of lentiviral vector-based vaccine candidates for HIV and provide additional details on our HIV-based lentiviral vector vaccine candidate for HIV, VRX1023, now called VRX1273.
As the paper, “An HIV-based lentiviral vector as HIV vaccine candidate: Immunogenic characterization,” points out, in contrast to vectors used in many previous HIV vaccine trials, lentiviral vectors have been shown to be less sensitive to anti-vector neutralizing activity, while displaying desirable characteristics, such as transduction of non-dividing cells (including antigen-presenting cells) and long-term transgene expression. At VIRxSYS, we have seen these benefits in our preclinical studies of VRX1023. As described in the new paper, this lentiviral vector-based HIV vaccine candidate induced significant mucosal and systemic cellular and humoral responses against HIV after sub-cutaneous injection in mice. We have also successfully used this candidate with a DNA prime (e.g. a prime-boost vaccine strategy) in mice, where it elicited as high as 21% HIV Gag-specific CD8 responses as measured by intracellular cytokine staining. Moreover, anti-vector immunity has not been an obstacle to repeated lentiviral vector-based vaccine administrations, as shown by improved anti-vector immune responses compared with repeat vaccine administrations compared to one-time administration. In addition, in head to head comparisons with adenoviral (Ad5) vectors expressing the same vaccine payload in mice, VRX1023 elicited higher and more persistent cellular and antibody responses to HIV than its adenoviral counterpart.
Adding to the preclinical data on VRX1023, in February we presented data from our non-human primate studies at the Conference on Retroviruses and Opportunistic Infections, showing that VRX1023, used as a prophylactic vaccine, is capable of achieving significant control of viral load and improving immune response following a large challenge with a highly pathogenic simian immunodeficiency virus (SIV), a virus found in non-human primates and similar to HIV. VIRxSYS is currently preparing for a Pre-IND Meeting followed by an Investigational New Drug Application for the therapeutic use of this HIV vaccine candidate in HIV infected patients.