Abstract 7: Serpin Treatment Reduces Mortality in γ68 Herpesvirus-Infected Mice by Rebalancing of Coagulation and Thrombolytic Cascades
Authors: Chen Hao , Zheng Donghang , Mee Bartee , Davids Jennifer , Thoburn Robert , Lucas Alexandra 
Published: March 2022

Vasculitic syndromes cause devastating arterial occlusion with associated end organ ischemia and significant morbidity. Treatment for vasculitic syndromes remains very limited. Gamma 68 herpesvirus (g68HV) infection in interferon gamma receptor deficient (IFNγR
-/-
) mice provides a good working model of artery inflammation, inducing early death with associated inflammatory cell invasion. Myxomavirus serpin, Serp-1, inhibits tPA, uPA, plasmin (thrombolytic) and fXa (thrombotic) proteases, reducing inflammation in a wide range of animal models whereas mammalian neuroserpin (NSP) inhibits tPA and uPA and reduced myocardial damage in clinical trial of unstable angina and stent implant. To assess the capacity of serpins to block inflammatory vasculopathy development, γ68HV infected IFNγR
-/-
mice were treated with either Serp-1 (100ng/g/100μl), NSP (100ng/g/100μl) or saline (100ul) .Serp-1 treatment given by daily intraperitoneal injections (i.p.) for the first 10 days post infection (6 - 12.5 X 106 PFU), significantly prolonged survival in mice (IFNγR
-/-
) (P ≤ 0.048). Saline treated γ68HV infected mice survived up to 42 days, whereas Serp-1 treated mice survived up to 55 days (N=60 mice, 6-12 mice per group). NSP treatment (100ng/gm i.p. X 10 days) produced an opposite trend toward increased mortality (P ≤ 0.079; N=16). In a subsequent study, prolonged daily treatment with Serp-1 (100ng/gm i.p.) given for the first 30 days post infection, markedly prolonged survival in γ68HV infected INFγR
-/-
mice for up to 150 days (P ≤ 0.032, N =10). Treatment with Serp-1, that was started 3 weeks post γ68HV infection, produced a non-significant trend toward improved survival (P=0.685; N = 12 mice), whereas treatment begun at 1 week post infection again significantly improved survival (P ≤ 0.020; N=12 mice). Serp-1 treatment significantly reduced inflammatory cell invasion in the aortic adventitia ( p < 0.010) and lung ( p < 0.047), NSP significantly increased inflammatory cell invasion when compared to Serp-1 treatment in infected mice in the lung interstitial layer (p ≤ 0.005). At 10 days follow up the plasma cytokine interleukin-1beta (IL-1β) was significantly reduced by Serp-1 treatment (p ≤ 0.049), Treatment with the NSP reduced plasma cytokine TNFα ( p ≤ 0.022), IFNγ (p ≤ 0.022), and IL-4 (p ≤ 0.022) in γ68HV infected IFNγR
-/-
mice (N=14).Gene expression was significantly increased in Serp-1 treated mice for regulatory serpins in the thrombolytic cascade, specifically PAI-1 (p ≤ 0.020) and unexpectedly NSP (p ≤ 0.032), gene expression was significantly reduced for E selectin (p ≤ 0.048) and increased for IL-10 (p ≤ 0.031), and addressin (p ≤ 0.002) with Serp-1 treatment at 10 days . Compared to the saline treated mice, NSP treatment lead to decreased arterial IL-17 and IL-10 gene expression (p ≤ 0.006 and 0.041, respectively) and increased PAI-2 (p ≤ 0.021) . When comparing differences in gene expression for Serp-1 and NSP; Serp-1 treatment increased gene expression for IL-10 (p ≤ 0.001), bFGF (p < 0.022), Addressin (p < 0.001), PAI-1 (p < 0.021), and NSP (p < 0.009) and NSP reduced IL-6 (p < 0.016) and PAI-2 (p < 0.016). Conclusion: Serp-1 but not NSP produced an unexpected improved survival after γ68HV infection with associated rebalancing of the coagulation and thrombolytic cascades as well as modulating inflammatory responses. Anti-inflammatory serpin provides a potential new therapeutic approach to virus induced vasculitis.