Endogenous HLA-DQ8αβ programs superantigens (SEG/SEI) to silence toxicity and unleash a tumoricidal network with long-term melanoma survival

Abstract

BackgroundAs the most powerful T cell agonists known, superantigens (SAgs) have enormous potential for cancer immunotherapy. Their development has languished due to high incidence (60%–80%) of seroreactive neutralizing antibodies in humans and tumor necrosis factor-α (TNFα)-mediated cardiopulmonary toxicity. Such toxicity has narrowed their therapeutic index while neutralizing antibodies have nullified their therapeutic effects.MethodsFemale HLA-DQ8 (DQA*0301/DQB*0302) tg mice expressing the human major histocompatibility complex II (MHCII) HLA-DQ8 allele on a high proportion of PBL, spleen and lymph node cells were used. In the established tumor model, staphylococcal enterotoxin G and staphylococcal enterotoxin I (SEG/ SEI) (50 µg each) were injected on days 6 and 9 following tumor inoculation. Lymphoid, myeloid cells and tumor cell digests from tumor tissue were assayed using flow cytometry or quantitated using a cytometric bead array. Tumor density, necrotic and viable areas were quantitated using the ImageJ software.ResultsIn a discovery-driven effort to address these problems we introduce a heretofore unrecognized binary complex comprizing SEG/SEI SAgs linked to the endogenous human MHCII HLA-DQ8 allele in humanized mice. By contrast to staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) deployed previously in clinical trials, SEG and SEI does not exhibit neutralizing antibodies in humans or TNFα-mediated toxicity in humanized HLA-DQ8 mice. In the latter model wherein SAg behavior is known to be ‘human-like’, SEG/SEI induced a powerful tumoricidal response and long-term survival against established melanoma in 82% of mice. Other SAgs deployed in the same model displayed toxic shock. Initially, HLA-DQ8 mediated melanoma antigen priming, after which SEG/SEI unleashed a broad CD4+ and CD8+ antitumor network marked by expansion of melanoma reactive T cells and interferon-γ (IFNy) in the tumor microenvironment (TME). SEG/SEI further initiated chemotactic recruitment of tumor reactive T cells to the TME converting the tumor from ‘cold’ to a ‘hot’. Long-term survivors displayed remarkable resistance to parental tumor rechallenge along with the appearance of tumor specific memory and tumor reactive T memory cells.ConclusionsCollectively, these findings show for the first time that the SEG/SEI-(HLA-DQ8) empowers priming, expansion and recruitment of a population of tumor reactive T cells culminating in tumor specific memory and long-term survival devoid of toxicity. These properties distinguish SEG/SEI from other SAgs used previously in human tumor immunotherapy. Consolidation of these principles within the SEG/SEI-(HLA-DQ8) complex constitutes a conceptually new therapeutic weapon with compelling translational potential.

Concurrent Brain Subregion Microgliosis in an HLA-II Mouse Model of Group A Streptococcal Skin Infection

“…20–24 weeks-old females and males expressing the human HLA-DQ8 (DQA1*0301/DQB1*0302) allele and deficient in endogenous class-II molecules [ 31 ] were used as sublethal mouse models of subcutaneous GAS infection. The genotype of the mice was confirmed by PCR-based genotyping using allele-specific oligonucleotide primers Sense 5′-AGG ATT TGG TGT ACC AGT TTA AGG GCA T-3′ and Antisense 5′-TGC AAG GTC GTG CGG AGC TCC AA-3′.…”

Acquired Resistance to Immune Checkpoint Blockades: The Underlying Mechanisms and Potential Strategies

“…Simultaneous anti-PD-1 and vaccine therapy can also reverse resistance ( 142 ). Furthermore, superantigens (SAgs) treatment emerges as a promising strategy to elicit immunogenicity ( 143 ). The detailed approaches to heat the cold tumor can be referred to in another review ( 20 ).…”

Expression of a Synthetic Staphylococcal Enterotoxin B in Escherichia coli BL21(DE3) for Cancer Therapy Development

“…This toxin can activate the immune system, followed by the secretion of apoptosis signals, like TNF-α and Fas Ligand [17]. Compared to other enterotoxins from S. aureus, SEB has antitumor activity in animals model [18]. To prevent the side effects of this toxin, a previous study [19] reported that infused antibody therapy Ig121 or c19F1 could be used to neutralize that toxin.…”