Lindgren Helena, Eneslätt Kjell, Golovliov Igor, Gelhaus Carl, Rydén Patrik, Wu Terry, Sjöstedt Anders
Department of Clinical Microbiology and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, SE-901 85 Umeå, Sweden.
MRIGlobal, Kansas City, MO 64110, USA.
Pathogens. 2020 Apr 30;9(5):338. doi: 10.3390/pathogens9050338.
causes the severe disease tularemia. In the present study, the aim was to identify correlates of protection in the rat co-culture model by investigating the immune responses using two vaccine candidates conferring distinct degrees of protection in rat and mouse models. The immune responses were characterized by use of splenocytes from naïve or Live vaccine strain- (LVS) or ∆∆-immunized Fischer 344 rats as effectors and bone marrow-derived macrophages infected with the highly virulent strain SCHU S4. A complex immune response was elicited, resulting in cytokine secretion, nitric oxide production, and efficient control of the intracellular bacterial growth. Addition of LVS-immune splenocytes elicited a significantly better control of bacterial growth than ∆∆ splenocytes. This mirrored the efficacy of the vaccine candidates in the rat model. Lower levels of IFN-γ, TNF, fractalkine, IL-2, and nitrite were present in the co-cultures with ∆∆ splenocytes than in those with splenocytes from LVS-immunized rats. Nitric oxide was found to be a correlate of protection, since the levels inversely correlated to the degree of protection and inhibition of nitric oxide production completely reversed the growth inhibition of SCHU S4. Overall, the results demonstrate that the co-culture assay with rat-derived cells is a suitable model to identify correlates of protection against highly virulent strains of .
引发严重疾病兔热病。在本研究中，目的是通过使用在大鼠和小鼠模型中提供不同程度保护的两种候选疫苗来研究免疫反应，从而在大鼠共培养模型中确定保护的相关因素。免疫反应通过使用来自未免疫或活疫苗株（LVS）或∆∆免疫的Fischer 344大鼠的脾细胞作为效应细胞以及感染高毒力菌株SCHU S4的骨髓来源巨噬细胞来表征。引发了复杂的免疫反应，导致细胞因子分泌、一氧化氮产生以及对细胞内细菌生长的有效控制。添加LVS免疫的脾细胞比∆∆脾细胞对细菌生长的控制效果明显更好。这反映了候选疫苗在大鼠模型中的效力。与来自LVS免疫大鼠的脾细胞共培养相比，与∆∆脾细胞共培养中IFN-γ、TNF、趋化因子、IL-2和亚硝酸盐的水平更低。发现一氧化氮是保护的一个相关因素，因为其水平与保护程度呈负相关，并且一氧化氮产生的抑制完全逆转了SCHU S4的生长抑制。总体而言，结果表明用大鼠来源细胞进行的共培养试验是确定针对高毒力菌株的保护相关因素的合适模型。
