ImmunoPET imaging of TIGIT in the glioma microenvironment

Abstract Glioblastoma (GBM) is the most common primary malignant brain tumor. Currently, there are few effective treatment options for GBM beyond surgery and chemo-radiation, and even with these interventions, median patient survival remains poor. While immune checkpoint inhibitors (ICIs) have demonstrated therapeutic efficacy against non-central nervous system cancers, ICI trials for GBM have typically had poor outcomes. TIGIT is an immune checkpoint receptor that is expressed on activated T-cells and has a role in the suppression of T-cell and Natural Killer (NK) cell function. As TIGIT expression is reported as both prognostic and a biomarker for anti-TIGIT therapy, we constructed a molecular imaging agent, [89Zr]Zr-DFO-anti-TIGIT (89Zr-αTIGIT), to visualize TIGIT in preclinical GBM by immunoPET imaging. PET imaging and biodistribution analysis of 89Zr-αTIGIT demonstrated uptake in the tumor microenvironment of GBM-bearing mice. Blocking antibody and irrelevant antibody tracer studies demonstrated specificity of 89Zr-αTIGIT with significance at a late time point post-tracer injection. However, the magnitude of 89Zr-αTIGIT uptake in tumor, relative to the IgG tracer was minimal. These findings highlight the features and limitations of using 89Zr-αTIGIT to visualize TIGIT in the GBM microenvironment

Mediation of Host Immune Responses after Immunization of Neonatal Calves with a Heat-Killed Mycobacterium avium subsp. paratuberculosis Vaccine ▿

A major drawback of current whole-cell vaccines for Mycobacterium avium subsp. paratuberculosis is the interference with diagnostic tests for bovine tuberculosis (TB) and paratuberculosis. The current study was designed to explore the effects of immunization with a heat-killed whole-cell vaccine (Mycopar) on diagnostic test performance and to characterize host immune responses to vaccination over a 12-month period. Neonatal dairy calves were assigned to treatment groups consisting of (i) controls, not vaccinated (n = 5), and (ii) vaccinates, vaccinated with Mycopar vaccine (n = 5). The results from this study demonstrated a rapid initiation of M. avium subsp. paratuberculosis-specific gamma interferon (IFN-γ) in vaccinated calves by 7 days, with robust responses throughout the study. Vaccinated calves also had responses to M. bovis purified protein derivative tuberculin (BoPPD) but minimal reactivity to ESAT-6/CFP-10, an M. bovis recombinant fusion protein. The levels of antigen-specific interleukin-4 (IL-4) and IL-10 were markedly decreased in vaccinated calves between days 7 and 90 of the study but thereafter were similar to the levels in controls. Vaccinated calves began to seroconvert at 4 months, with 4/5 calves having detectable M. avium subsp. paratuberculosis antibody by 6 months. The responses in test platforms for bovine TB were negligible in the vaccinate group, as only one calf had a response, which was in the suspect range of the comparative cervical skin test. Serum antibody responses to M. bovis antigens ESAT-6, CFP-10, and MPB83 were negative on the Vet TB STAT-PAK, DPP VetTB, and DPP BovidTB tests. These results suggest that the Mycopar vaccine will interfere with diagnostic tools for paratuberculosis but result in low interference with the comparative cervical skin test and emerging serologic tests for M. bovis