Recombinant Poxvirus and the Tumor Microenvironment: Oncolysis, Immune Regulation and Immunization

Oncolytic viruses (OVs) are being extensively studied for their potential roles in the development of cancer therapy regimens. In addition to their direct lytic effects, OVs can initiate and drive systemic antitumor immunity indirectly via release of tumor antigen, as well as by encoding and delivering immunostimulatory molecules. This combination makes them an effective platform for the development of immunotherapeutic strategies beyond their primary lytic function. Engineering the viruses to also express tumor-associated antigens (TAAs) allows them to simultaneously serve as therapeutic vaccines, targeting and amplifying an immune response to TAAs. Our group and others have shown that vaccinating intratumorally with a poxvirus that encodes TAAs, in addition to immune stimulatory molecules, can modulate the tumor microenvironment, overcome immune inhibitory pathways, and drive both local and systemic tumor specific immune responses

Phase I neoadjuvant study of intravesical recombinant fowlpox-GM-CSF (rF-GM-CSF) or fowlpox-TRICOM (rF-TRICOM) in patients with bladder carcinoma

Intravesical BCG is a highly effective treatment for high-grade nonmuscle invasive bladder cancer and carcinoma in situ (CIS); however, for patients who are either resistant or become unresponsive to BCG therapy there is a need for alternative treatment approaches. This study examined the safety and feasibility of intravesically administered recombinant fowlpox virus encoding GM-CSF (Arm A) or TRICOM (Arm B); and the local and systemic immunologic responses generated to the vector(s). Twenty bladder cancer patients scheduled for cystectomy as their standard of care received preoperatively four weekly doses of intravesical recombinant fowlpox. Treatment was well tolerated, however, three patients experienced transient elevations of liver transaminases, with one rising to the level of a DLT. Cystectomy derived tumor and normal bladder mucosa demonstrated mRNA for the virally encoded LacZ gene supporting effective infection/transfection. Detected serum antibody to the LacZ encoding β-galactosidase indicated successful expression of vector-encoding gene products and the ability to immunize via the bladder site. H&E and IHC using a panel of immune cell specific antigens demonstrated immune cell infiltration of the bladder wall. These findings demonstrate good safety profile, successful infection/transfection, ability to generate systemic immune response, and local recruitment of immune cell populations with intravesical administration of fowlpox-based constructs encoding for GM-CSF(rF-GM-CSF) or TRICOM (rF-TRICOM), and support further evaluation of this treatment modality for bladder cancer

Non-oncogenic Acute Viral Infections Disrupt Anti-cancer Responses and Lead to Accelerated Cancer-Specific Host Death

In light of increased cancer prevalence and cancer-specific deaths in patients with infections, we investigated whether infections alter anti-tumor immune responses. We report that acute influenza infection of the lung promotes distal melanoma growth in the dermis and leads to accelerated cancer-specific host death. Furthermore, we show that during influenza infection, anti-melanoma CD8+ T cells are shunted from the tumor to the infection site, where they express high levels of the inhibitory receptor programmed cell death protein 1 (PD-1). Immunotherapy to block PD-1 reverses this loss of anti-tumor CD8+ T cells from the tumor and decreases infection-induced tumor growth. Our findings show that acute non-oncogenic infection can promote cancer growth, raising concerns regarding acute viral illness sequelae. They also suggest an unexpected role for PD-1 blockade in cancer immunotherapy and provide insight into the immune response when faced with concomitant challenges