MODIFIED MYXOMAVIRAL SERPIN REACTIVE CENTER LOOP (RCL) PEPTIDE IMPROVES SURVIVAL AND OUTCOMES IN AN ACCELERATED LETHAL MOUSE INFLAMMATORY VASCULITIC SYNDROME MODEL



Alexandra R. Lucas, M.D., Biodesign Institute/ Arizona State University, Arizona & St Joseph’s Hospital, Phoenix, AZ, USA

Introduction: Inflammatory vascular syndromes (IVS), giant cell arteritis and Takayasu’s disease, are rare but devastating arterial disorders. Mouse gamma herpesviral (MHV68) infection in interferon gamma receptor knockout mice (IFNγR-/-) is a model for a lethal IVS. The role of the bacterial microbiome in IVS and treatment remains undefined. In prior work, Myxomavirus-derived serine protease inhibitor (serpin), Serp-1, and a Serp-1 RCL-derived anti-inflammatory peptide, S-7 (G305TTASSDTAITLIPR319), significantly improved survival and reduced aortic inflammation in MHV68-infected IFNγR-/- mice.

Method: We examined survival and disease progression in 56 MHV68-infected IFNγR-/- mice with and without Serp-1 or serpin peptide (S-2, S-7, S-8, or two modified S-7 peptides designed for enhanced function in silico) treatments, with and without oral antibiotics. We also assessed microRNA responses to Serp-1 by qPCR and potential plasma protein targets for S-7 by mass spectrometry.

Results: Depletion of gut bacteria accelerated MHV68-induced IVS markedly, increasing early mortality and reducing survival from 60 to 20 days (P<0.036). Suppression of gut bacteria also reduced Serp-1 and S-7 treatment efficacy, decreasing survival from 70% at 150 days to 20% at 30 days for Serp-1 (P<0.0028) and 0% at 30 days for S-7 (P<0.0001). S-2 was inactive and S-8 treatment trended towards improved survival with antibiotic treatment (N=14), while treatment with two modified S-7 peptides (N=10) optimized for serpin blockade retained efficacy and improved survival in MHV68-infected mice (P<0.001). Mass spectrometry revealed S-7 bound to numerous plasma proteins including complements C1S and C3, plasminogen, fibrinogen, antithrombin, and antitrypsin. Antibiotics suppressed aerobic stool bacterial growth and phage counts without alteration of Serp-1 inhibition of uPA. Serp-1 significantly decreased miRNAs 126 and 136 and increased miRNA 335.

Conclusion: Myxomavirus-derived Serp-1 protein and RCL peptide S-7 improve survival in a lethal MHV68 infection in mice. Suppression of gut bacteria both accelerates MHV68 infection and blocks Serp-1 and S-7 peptide treatment efficacy, suggesting microbiome-mediated modulation of serpin treatment in herpes infection. Modified S-7 peptides restored therapeutic benefit in antibiotic-treated MHV68-infected mice. The collective microbiome, or specific microbial sub-populations, may play a central role in viral sepsis, IVS, and modulation of treatment response.