Heterologous prime-boost vaccination targeting MAGE-type antigens promotes tumor T-cell infiltration and improves checkpoint blockade therapy.

BACKGROUND: The clinical benefit of immune checkpoint blockade (ICB) therapy is often limited by the lack of pre-existing CD8+ T cells infiltrating the tumor. In principle, CD8+ T-cell infiltration could be promoted by therapeutic vaccination. However, this remains challenging given the paucity of vaccine platforms able to induce the strong cytotoxic CD8+ T-cell response required to reject tumors. A therapeutic cancer vaccine that induces a robust cytotoxic CD8+ T-cell response against shared tumor antigens and can be combined with ICB could improve the outcome of cancer immunotherapy. METHODS: Here, we developed a heterologous prime-boost vaccine based on a chimpanzee adenovirus (ChAdOx1) and a modified vaccinia Ankara (MVA) encoding MAGE-type antigens, which are tumor-specific shared antigens expressed in different tumor types. The mouse MAGE-type antigen P1A was used as a surrogate to study the efficacy of the vaccine in combination with ICB in murine tumor models expressing the P1A antigen. To characterize the vaccine-induced immune response, we performed flow cytometry and transcriptomic analyses. RESULTS: The ChAdOx1/MVA vaccine displayed strong immunogenicity with potent induction of CD8+ T cells. When combined with anti-Programmed Cell Death Protein 1 (PD-1), the vaccine induced superior tumor clearance and survival in murine tumor models expressing P1A compared with anti-PD-1 alone. Remarkably, ChAdOx1/MVA P1A vaccination promoted CD8+ T-cell infiltration in the tumors, and drove inflammation in the tumor microenvironment, turning 'cold' tumors into 'hot' tumors. Single-cell transcriptomic analysis of the P1A-specific CD8+ T cells revealed an expanded population of stem-like T cells in the spleen after the combination treatment as compared with vaccine alone, and a reduced PD-1 expression in the tumor CD8+ T cells. CONCLUSIONS: These findings highlight the synergistic potency of ChAdOx1/MVA MAGE vaccines combined with anti-PD-1 for cancer therapy, and establish the foundation for clinical translation of this approach. A clinical trial of ChadOx1/MVA MAGE-A3/NY-ESO-1 combined with anti-PD-1 will commence shortly.

Xenoantigen Deletion and Chemical Immunosuppression Can Prolong Renal Xenograft Survival.

OBJECTIVE: Xenotransplantation using pig organs could end the donor organ shortage for transplantation, but humans have xenoreactive antibodies that cause early graft rejection. Genome editing can eliminate xenoantigens in donor pigs to minimize the impact of these xenoantibodies. Here we determine whether an improved cross-match and chemical immunosuppression could result in prolonged kidney xenograft survival in a pig-to-rhesus preclinical model. METHODS: Double xenoantigen (Gal and Sda) knockout (DKO) pigs were created using CRISPR/Cas. Serum from rhesus monkeys (n = 43) was cross-matched with cells from the DKO pigs. Kidneys from the DKO pigs were transplanted into rhesus monkeys (n = 6) that had the least reactive cross-matches. The rhesus recipients were immunosuppressed with anti-CD4 and anti-CD8 T-cell depletion, anti-CD154, mycophenolic acid, and steroids. RESULTS: Rhesus antibody binding to DKO cells is reduced, but all still have positive CDC and flow cross-match. Three grafts were rejected early at 5, 6, and 6 days. Longer survival was achieved in recipients with survival to 35, 100, and 435 days. Each of the 3 early graft losses was secondary to IgM antibody-mediated rejection. The 435-day graft loss occurred secondary to IgG antibody-mediated rejection. CONCLUSIONS: Reducing xenoantigens in donor pigs and chemical immunosuppression can be used to achieve prolonged renal xenograft survival in a preclinical model, suggesting that if a negative cross-match can be obtained for humans then prolonged survival could be achieved.

Immune recognition of exposed xenoantigens on the surface of PEGylated bovine red blood cells.

Due to potential problems that can occur during blood transfusion and increasing blood shortages, our group engineered methoxypolyethylene glycol conjugated bovine red blood cells (mPEG-bRBCs) as a potential universal oxygen therapeutic. This current work investigates the immunological properties of mPEG-bRBCs incubated with human plasma (hP) and correlates these properties to exposed Galalpha(1,3)Gal xenoantigens. After mPEG-bRBCs were incubated with hP, the amount of bound IgG and IgM was assessed via flow cytometry. Flow cytometry also assessed the amount of GS-IB4 bound to exposed Galalpha(1,3)Gal xenoantigens. The results of this study demonstrate that most hP samples strongly promote agglutination of mPEG-bRBCs regardless of the extent of mPEG surface coverage or donor blood type. IgG and IgM from hP bound strongly to mPEG-bRBCs. In general, the Galalpha(1,3)Gal xenoantigen remains exposed at all levels of PEG surface coverage. PEGylation did block some of the xenoantigens as the amount of exposed Galalpha (1,3)Gal decreased with increased mPEG surface coverage. However, this was not sufficient to prevent a strong agglutination reaction. Taken together, the results of this study indicate that the current strategy for PEGylating bRBCs is unsatisfactory for the development of immunologically silent oxygen therapeutics.

[A comparative study of the synthesis of membrane hetero-organic antigens of kidney origin on tissue slices and isolated cells after a single carcinogenic exposure in rats]. / Sravnitel'noe izuchenie sinteza membrannykh geteroorgannykh antigenov pochechnoi prirody na tkanevykh srezakh i izolirovannykh kletkakh posle odnokratnogo kantserogennogo vozdeistviia na krys.

A comparative study was carried out of a single carcinogenic injection of rats with a "weak" carcinogen, 4-dimethylaminoazobenzene (DAB), and a "strong" carcinogen, N-diethylnitrozamine (DENA). Both carcinogenic agents caused similar antigenic rearrangements involving the appearance of membrane hetero-organic antigens of kidney origin associated with the Zajdela hepatoma on the hepatocyte membrane. The expression of these antigens is longer in DENA carcinogenesis. On the sections of embryonic liver (16-18 days) single hepatocytes were discovered carrying membrane hetero-organic antigens. No synthesis of these antigens was discovered in cells of the definitive liver, but it was seen to resume at early stages of carcinogenesis. Quantitative characteristics of synthesis of the investigated antigens was done by means of immunocytofluorometric method using membranes of isolated hepatoma cells and hepatocytes of rats after a single carcinogenic injection and partial hepatectomy.

Two chicken monoclonal antibodies specific for heterophil Hanganutziu-Deicher antigens.

Two chicken monoclonal antibodies (MAbs), HU/Ch2-7 and HU/Ch6-1, against heterophil Hanganutziu-Deicher (HD) antigens with N-glycolylneuraminic acid (NeuGc) at a terminal carbohydrate were established by cell fusions using chicken B cell lines lacking thymidine kinase and spleen cells from chickens immunized with II3NeuGc alpha-LacCer (HD3). The reactivities of these MAbs against several gangliosides including NeuGc-containing glycosphingolipids were examined by a thin-layer chromatography/immunostaining method. MAb HU/Ch2-7 (IgG) reacted strongly with HD3 and IV3NeuGc alpha-nLc4Cer (HD5) and weakly with VI3NeuGc alpha-nLc6Cer (HD7) and 4-O-acetyl-HD3. HU/Ch6-1 (IgG) reacted with HD3 and HD5, but did not react with the other HD antigens. The reactivities of these MAbs against HD antigen were greatly reduced by pre-treatment of the antigen with neuraminidase. These MAbs did not react with N-acetylneuraminic acid-containing gangliosides (GM1 and GM3). These results indicate that these two chicken MAbs are directed toward the antigenic epitope containing the NeuGc.

[The expression of hetero-organic antigens of kidney origin on the surfaces of cultured rat hepatocytes under the influence of the narrow-band fractions of non-histone chromosomal proteins]. / Ekspressiia geteroorgannykh antigenov pochechnoi prirody na poverkhnosti kul'tiviruemykh gepatotsitov krys pod vliianiem uzkikh fraktsii khromosomal'nykh negistonovykh belkov.

Narrow fractions of nonhistone chromosomal proteins (NHCP) eluted with 0.4-0.5 M NaCl from the phosphocellulose column stimulate expression of hetero-organic antigens of kidney origin on the membrane of intact hepatocytes cultured in suspension. These fractions of NHCP were isolated from the intact rats kidney, from cells of hepatoma 27 and Zajdela hepatoma, and from the carcinogenic liver after a single diethylnirozamine injection. The membrane hetero-organic antigens were identified by means of indirect immunofluorescence using specific immune serum.