Listr1遗传位点影响小鼠对约氏疟原虫易感性的研究

探讨Listr1遗传位点影响小鼠对疟原虫易感性的可能性及其初步作用机制。致死型约氏疟原虫(Plasmodiumyoelii17XL,P.y17XL)感染C.B6By-Listr1小鼠(BALB/c小鼠基因背景下引入C57BL/6小鼠Lis-tr1遗传位点的同类系小鼠)和BALB/c小鼠,分析二者生存率和感染率的差异;HE染色分析P.y17XL感染后第5天C.B6By-Listr1小鼠和BALB/c小鼠肝脏组织损伤情况;定量PCR法检测P.y17XL感染后小鼠肝脏组织第1、2、5天IL-1β、IL-6、TNF-α、IFN-γ的表达含量。结果显示,P.y17XL感染后4~8dC.B6By-Listr1小鼠虫血症水平显著高于BALB/c小鼠(P<0.05)。C.B6By-Listr1小鼠于感染后7~9d全部死亡;而半数BALB/c小鼠于感染后8~9d死亡,其余BALB/c小鼠至感染后第13天仍存活,两种小鼠生存率差异具有统计学意义(P<0.01)。C.B6By-Listr1小鼠P.y17XL感染后第5天肝组织HE染色可见到明显的疟色素沉积;而BALB/c小鼠全片基本未见到疟色素的沉积。P.y17XL感染后第2天BALB/c小鼠肝组织IL-6(P<0.05)、TNF-α(P<0.05)mRNA水平显著高于C.B6By-Listr1小鼠。结果表明Listr1遗传位点可以影响小鼠对疟原虫的易感性,与肝脏固有免疫相关。     

遗传位点影响小鼠对约氏疟原虫易感性的研究

探讨Listr1遗传位点影响小鼠对疟原虫易感性的可能性及其初步作用机制。致死型约氏疟原虫(Plasmodium yoelii 17XL,P.y17XL)感染C.B6By Listr1小鼠（BALB/c小鼠基因背景下引入C57BL/6小鼠Listr1遗传位点的同类系小鼠）和BALB/c小鼠,分析二者生存率和感染率的差异;HE染色分析P.y17XL感染后第5天C.B6By Listr1小鼠和BALB/c小鼠肝脏组织损伤情况;定量PCR法检测P.y17XL感染后小鼠肝脏组织第1、2、5天IL-1β、IL-6、TNF-α、IFN-γ的表达含量。结果显示,P.y17XL感染后4~8 d C.B6By Listr1小鼠虫血症水平显著高于BALB/c小鼠（P＜0.05）。C.B6By Listr1小鼠于感染后7~9 d全部死亡;而半数BALB/c小鼠于感染后8~9 d死亡,其余BALB/c小鼠至感染后第13天仍存活,两种小鼠生存率差异具有统计学意义（P＜0.01）。C.B6By Listr小鼠P.y17XL感染后第5天肝组织HE染色可见到明显的疟色素沉积;而BALB/c小鼠全片基本未见到疟色素的沉积。P.y17XL感染后第2天BALB/c小鼠肝组织IL-6（P＜0.05)、TNF-α（P＜0.05)mRNA水平显著高于C.B6By Listr1小鼠。结果表明Listr1遗传位点可以影响小鼠对疟原虫的易感性,与肝脏固有免疫相关。     

B型流感病毒B/Yamagata/16/88反向遗传操作平台的搭建及BALB/c小鼠感染模型的建立

目的利用基因工程技术全基因合成B型流感病毒B/Yamagata/16/88的8个基因节段,并利用反向遗传技术从体外拯救B型流感病毒B/Yamagata/16/88,同时建立BALB/c小鼠感染模型,为下一步研究B型流感病毒致病机制、传播机制以及开发新型疫苗奠定基础。方法通过基因合成和反向遗传技术体外拯救B型流感病毒B/Yamagata/16/88。全基因组测序验证拯救病毒基因组序列与Genbank序列的一致性。将拯救病毒以105EID50的攻毒剂量人工感染BALB/c小鼠,通过体重变化、生存率、肺脏病毒复制等方面进行致病性分析,建立小鼠感染模型。结果成功从体外拯救出B型流感病毒B/Yamagata/16/88,命名为B-S9。全基因组测序结果表明,B-S9基因组序列与Genbank公布序列一致。B-S9能够人工感染BALB/c小鼠,但不致死,对BALB/c小鼠呈现低致病性;攻毒后第3天,B-S9感染小鼠体重出现下降,攻毒后第8天,小鼠体重开始回升;攻毒后第3天和第6天,B-S9感染小鼠的肺脏内均能检测到病毒复制,且攻毒后第3天的小鼠肺脏病毒滴度比攻毒后第6天的小鼠肺脏滴度高132倍。结论成功搭建B型流感病毒B/Yamagata/16/88反向遗传操作平台,并建立BALB/c小鼠感染模型。目前国内外对B型流感病毒的研究比较少,该反向遗传操作平台的建立为B型流感病毒致病机制和传播机制的研究奠定了基础,同时也为包括B型流感病毒减毒活疫苗在内的新型疫苗的研制开辟了新途径。     

流感泰得在小鼠体内抗H1N1型FM1株流感病毒活性研究

目的:研究流感泰得预防给药在小鼠体内对H1N1型FM1株流感病毒的抑制作用及对病毒感染小鼠的保护作用。方法:BALB/c小鼠随机分为正常对照组,病毒对照组,磷酸奥司他韦组,流感泰得2.5、5、10 mg/kg组,提前24h和1 h滴鼻给药2次,于第二次给药1 h后滴鼻感染小鼠造成肺炎模型,连续观察14 d,统计小鼠存活率、平均存活天数、体重变化;按以上方法于造模后第5 d天取肺脏,计算肺指数、肺脏病毒滴度。结果:与病毒对照组相比,流感泰得3个剂量组可明显提高病毒感染小鼠的存活率,延长平均存活时间,缓解病毒感染引起的体重降低,降低病毒感染小鼠的肺指数和肺脏病毒滴度。结论:流感泰得在小鼠体内预防给药具有抗H1N1型FM1株流感病毒活性。     

板蓝根颗粒对甲型流感病毒小鼠的作用

目的测定板蓝根颗粒抗流感病毒的药效作用。方法 A/California/7/2009（CA7）病毒滴鼻感染BALB/c小鼠观察14d,观察板蓝根对甲型H1N1流感病毒感染小鼠的保护作用,计算小鼠存活率、存活天数以及延长生命率。感染的小鼠第5天每组小鼠处死一半,取肺组织,观察板蓝根对甲型H1N1流感病毒感染小鼠肺组织的保护作用。结果板蓝根可明显延长甲型H1N1流感病毒感染小鼠的存活天数并提高存活率,病理结果显示板蓝根对甲型H1N1流感病毒感染的小鼠的肺组织有一定程度的保护作用,与模型组比较差异显著（P〈0.05）。结论板蓝根颗粒对甲型H1N1流感病毒感染的小鼠有较好的保护作用。     

小鼠对仙台病毒Tianjin株易感性研究

研究129Sv、DBA/2、Kunming、BALB/c四种小鼠对仙台病毒Tianjin株的感染特点,并通过观察易感性的不同,确定适于研究此病毒致病性及疫苗的小型啮齿类实验动物。用9～11d龄鸡胚接种仙台病毒Tianjin株,72h后收集尿囊腔内效价为1:1 280病毒液,用5μl和6倍稀释的30μl病毒液分别接种129Sv、DBA/2、Kunming、BALB/c小鼠,观查12d小鼠体重变化,计算生存率。用6倍稀释的30μl病毒液接种Kunming、BALB/c小鼠,于接种前第1天以及接种后第4、7天断颈处死,取左肺制成切片,HE染色观察病理改变,综合判断仙台病毒Tianjin株对四种鼠感染的易感性的不同。129Sv、DBA/2小鼠在接种仙台病毒Tianjin株5μl后,最高平均体重下降分别为13.0%、4.7%,四种鼠12d生存率均为100%;接种稀释的30μl病毒液,129Sv、DBA/2、Kunming、BALB/c最高平均体重下降21.7%、30.3%、16.7%、9.6%;12d生存率分别为20%、0%、80%、100%。Kunming鼠在感染后第4、7d的肺组织病理改变较BALB/c严重,表现为大量炎细胞渗出,粘膜下层实质性增厚。以上实验结果表明DBA/2对仙台病毒Tianjin株感染最易感,BALB/c耐受性最强,易感顺序为DBA/2129SvKunmingBALB/c。DBA/2和129Sv小鼠可作为仙台病毒Tianjin株致病性及疫苗研究的首选实验动物。     

不同手术方法对小鼠同种异基因移植皮片存活的比较

目的采用不同手术缝合方式观察小鼠移植皮片存活及生长情况,以建立一种简单易行、快速经济的小鼠同种异基因皮肤移植方法.方法 受体BALB/c小鼠随机分为3组(Z组、J组和T组),每组20只,通过背-背法进行供体C57BL/6的皮片移植,Z组、J组和T组分别采用四周缝合、对角缝合和粘贴固定的皮片缝合方法.每天监测小鼠体重变化及生长状态,观察26天,实验第3、7、15和26天观察各组受体移植皮片存活情况,其中皮片变硬、结痂脱落或坏死判定为移植排斥.第26天取小鼠皮肤移植组织以及肝脾组织进行病理检测.结果 各组小鼠移植物平均体重变化趋势类似,第6天达到最低水平,移植皮片病理检测结果显示,各组均见移植皮片真皮内淋巴细胞浸润,3组病理结果类似,肝脾病理检测发现淋巴细胞大量浸润,说明造模成功.实验26天后,Z组、J组和T组小鼠皮片分别有7、5和3只受体小鼠皮片仅观察到炎症反应.结论 3种手术方式建模均成功,但采用粘贴固定方式进行小鼠背部皮肤移植具有手术方式简单有效、对皮肤损伤小的优点,是一种较好的小鼠同种异基因皮肤移植手术方法.     

IL-10在输血相关性移植物抗宿主病小鼠模型中的免疫调节作用

目的:IL-10在输血相关性移植物抗宿主病小鼠模型中的免疫调节作用。方法:取BALB/c实验小鼠免疫活性淋巴细胞,分别输注于BALB/c小鼠(设为A组)及BALB/c裸鼠(设为B组),建立TA-GVHD模型,观察小鼠症状,HE染色判断小鼠肝、肺、小肠、皮肤病理变化情况;采用双夹心酶联免疫吸附法(ELISA)检测两组小鼠血清IL-10浓度;用逆转录聚合酶链反应法RT-PCR检测移植后外周血单个核细胞中IL-10的表达。结果:A组中2只死亡(12.5%),B组中3只死亡(18.75%),共5只死亡,29只存活,两组死亡率比较无明显差异(P>0.05)。B组小鼠累及肝、肺、小肠和皮肤病理损伤程度较A组严重;存活小鼠IL-10浓度较死亡小鼠明显升高(P2<0.05);存活小鼠IL-10 mRNA表达阳性率96.55%明显高于死亡小鼠(20.00%)。结论:IL-10在输血相关的移植物抗宿主病小鼠模型中发挥负向免疫调节--免疫抑制作用。     

二甲基苯蒽/佛波酯两步化学法诱导小鼠皮肤癌的模型优化

目的对两步化学诱导法建立BALB/c小鼠皮肤癌模型进行方法优化。方法将BALB/c小鼠背部剃毛暴露出约2 cm×2 cm的皮肤,小鼠随机分为空白对照组和4个模型组,4个模型组第1周分别涂1、2、4、7次100μg/100μL DMBA/丙酮液,后续均1周涂两次4μg/100μL TPA/丙酮液,记录小鼠体重、成瘤时间、成瘤数量,并在12周后处死小鼠取肿瘤组织及瘤旁组织做HE染色分析。结果 1周涂1次DMBA成瘤周期长;1周两次成瘤周期短,质量高;1周4次会损伤皮肤但不影响肿瘤的形成;1周7次对皮肤伤害较大并导致小鼠死亡。结论采用第1周涂两次DMBA启动,后续用TPA连续诱导建立BALB/c小鼠皮肤癌模型操作简便,成瘤期短,癌变率高,与人类皮肤癌发生发展相似,可用于建立研究皮肤癌较为理想的实验动物模型。     

博尔纳病病毒对BALB/c小鼠感染性检测

目的分析博尔纳病病毒（Borna disease virus,BDV）H1766株对BALB/c小鼠的感染性。方法选择病毒滴度为2.0×107FFU/ml的BDV病毒液分别对新生和成年BALB/c小鼠进行脑内接种,并用相同病毒液对原代培养的新生BALB/c小鼠脑细胞进行接种。经过一定时间的病毒作用后分别提取总RNA,采用巢式RT-PCR方法检测BDV-p40基因,并通过免疫组化方法检测脑内接种脑组织中BDV-P40蛋白。结果脑内接种病毒的小鼠脑组织中可以检测到BDV-p40基因和BDV-P40蛋白,培养的小鼠脑细胞中可以检测到BDV-p40基因。结论BDVH1766株可以感染新生和成年的BALB/c小鼠。     

Effect of rotavirus strain on the murine model of biliary atresia

Biliary atresia is a devastating disorder of the newborn in which afflicted infants develop inflammation and fibrosis of the extrahepatic biliary tract, resulting in cirrhosis and end-stage liver disease. Infection with a virus is thought to be a contributing factor in the etiology of biliary atresia. In the murine model of biliary atresia, perinatal exposure to rhesus rotavirus (RRV) results in biliary epithelial cell infection causing bile duct obstruction. The purpose of this study was to determine if tropism for the biliary epithelial cell was unique to RRV. Newborn mice underwent intraperitoneal injection with five strains of rotavirus: RRV (simian), SA11-FM (simian/bovine), SA11-SM (simian), EDIM (murine), and Wa (human). RRV and SA11-FM caused clinical manifestations of bile duct obstruction and high mortality. SA11-SM caused clinical signs of hepatobiliary injury but the mortality was markedly reduced. EDIM and Wa caused no sign of hepatobiliary disease. The systemic and temporal distribution of viral protein and live virus varied according to the injected strain. Immunohistochemistry revealed that RRV and SA11-FM targeted the biliary epithelial cells. In contrast, SA11-SM was found in the liver but in not in the biliary epithelium. These results indicate that strain-specific characteristics dictate tropism for cells of hepatobiliary origin which in turn impact the ability to induce the murine model of biliary atresia.     

B Cell Deficient Mice Are Protected from Biliary Obstruction in the Rotavirus-Induced Mouse Model of Biliary Atresia

A leading theory regarding the pathogenesis of biliary atresia (BA) is that bile duct injury is initiated by a virus infection, followed by an autoimmune response targeting bile ducts. In experimental models of autoimmune diseases, B cells have been shown to play an important role. The aim of this study was to determine the role of B cells in the development of biliary obstruction in the Rhesus rotavirus (RRV)-induced mouse model of BA. Wild-type (WT) and B cell-deficient (Ig-α^-/-) mice received RRV shortly after birth. Ig-α^-/- RRV-infected mice had significantly increased disease-free survival rate compared to WT RRV-infected BA mice (76.8% vs. 17.5%). In stark contrast to the RRV-infected BA mice, the RRV-infected Ig-α^-/- mice did not have hyperbilirubinemia or bile duct obstruction. The RRV-infected Ig-α^-/- mice had significantly less liver inflammation and Th1 cytokine production compared to RRV-infected WT mice. In addition, Ig-α^-/- mice had significantly increased numbers of regulatory T cells (Tregs) at baseline and after RRV infection compared to WT mice. However, depletion of Tregs in Ig-α^-/- mice did not induce biliary obstruction, indicating that the expanded Tregs in the Ig-α^-/- mice were not the sole reason for protection from disease. Conclusion: B cell deficient Ig-α^-/- mice are protected from biliary obstruction in the RRV-induced mouse model of BA, indicating a primary role of B cells in mediating disease pathology. The mechanism of protection may involve lack of B cell antigen presentation, which impairs T-cell activation and Th1 inflammation. Immune modulators that inhibit B cell function may be a new strategy for treatment of BA.     

Cholangiocyte expression of alpha2beta1-integrin confers susceptibility to rotavirus-induced experimental biliary atresia

Inoculation of BALB/c mice with rhesus rotavirus (RRV) in the newborn period results in biliary epithelial cell (cholangiocyte) infection and the murine model of biliary atresia. Rotavirus infection of a cell requires attachment, which is governed in part by cell-surface expression of integrins such as alpha2beta1. We hypothesized that cholangiocytes were susceptible to RRV infection because they express alpha2beta1. RRV attachment and replication was measured in cell lines derived from cholangiocytes and hepatocytes. Flow cytometry was performed on these cell lines to determine whether alpha2beta1 was present. Cholangiocytes were blocked with natural ligands, a monoclonal antibody, or small interfering RNA against the alpha2-subunit and were infected with RRV. The extrahepatic biliary tract of newborn mice was screened for the expression of the alpha2beta1-integrin. Newborn mice were pretreated with a monoclonal antibody against the alpha2-subunit and were inoculated with RRV. RRV attached and replicated significantly better in cholangiocytes than in hepatocytes. Cholangiocytes, but not hepatocytes, expressed alpha2beta1 in vitro and in vivo. Blocking assays led to a significant reduction in attachment and yield of virus in RRV-infected cholangiocytes. Pretreatment of newborn pups with an anti-alpha2 monoclonal antibody reduced the ability of RRV to cause biliary atresia in mice. Cell-surface expression of the alpha2beta1-integrin plays a role in the mechanism that confers cholangiocyte susceptibility to RRV infection.     

Dendritic Cells Regulate Treg-Th17 Axis in Obstructive Phase of Bile Duct Injury in Murine Biliary Atresia

Several cell types are considered to be effector cells in bile duct injury in rhesus rotavirus (RRV)-induced experimental biliary atresia (BA). Here, we identified an increased T helper 17 (Th17) cell population in a BA mode. By depleting the Th17 cells, the BA symptoms (onset of jaundice, acholic stools and retarded growth) were attenuated and the survival rate was improved. Furthermore, we found that in mice with BA, the percentage of CD4⁺CD25^highFoxp3⁺ T regulatory (Treg) cells decreased along with the increased percentage of Th17 cells. However, the absolute numbers of Treg and Th17 cells were both increased in liver of RRV-injected mice compared to saline-injected mice. The proportion of Th17 cells at 7 days post-infection was decreased if Treg cells isolated from normal adult mice, but not Treg cells from the livers of mice with BA, were intraperitoneally transferred on day 5 of life. In vitro experiments also showed that Treg cells from mice with BA had a diminished suppressive effect on Th17 cell generation. To determine the mechanisms, we investigated the production of cytokines in the liver. The level of IL-6, which has been shown to be abundantly secreted by activated dendritic cells (DCs), was remarkably elevated. Importantly, in a Treg/Th17 cell suppression assay, IL-6 was demonstrated to paralyze the Treg cells’ suppressive effect on Th17 cells and eventually the unrestrained increase of Th17 cells contributed to bile duct injury. In conclusion, the DC-regulated Treg-Th17 axis, probably in conjunction with other effector T cells, aggravates progressive inflammatory injury at the time of ductal obstruction.     

四氯化碳、酒精与四氯化碳联合、胆管结扎致SD大鼠肝纤维化病理学比较

目的研究四氯化碳、酒精与四氯化碳联合、胆管结扎致SD大鼠肝纤维化模型肝脏的病理学改变,初步探讨肝纤维化发病机制。方法四氯化碳组SD大鼠以3 mg/kg的剂量（首次剂量加倍）皮下注射50%四氯化碳（四氯化碳∶橄榄油=1∶1）,每周2次,连续注射6周;酒精与四氯化碳联合组SD大鼠每日按照10 mL/kg剂量灌服酒精混合物（酒精∶吡唑∶玉米油=10 mL∶25 mg∶2 mL）,同时每周2次按0.3 mL/kg剂量给予腹腔注射四氯化碳∶橄榄油（1∶3）,连续造模60 d;胆管结扎组大鼠按10 mg/kg体重腹腔注射3%戊巴比妥钠麻醉,腹部皮肤消毒,无菌操作沿腹部正中线剪开腹腔,分离出胆管,在胆管近端和远端2处结扎胆管,28 d后结束实验。试验结束后麻醉动物,解剖取动物肝脏组织,用10%福尔马林固定,进行病理学检查。结果四氯化碳致SD大鼠肝纤维化模型表现为弥漫性脂肪肝、肝炎、肝纤维化;酒精与四氯化碳联合致SD大鼠肝纤维化模型表现为酒精性脂肪肝、肝炎、肝纤维化;胆管结扎致SD大鼠肝纤维化模型表现为胆管增生、肝炎、肝纤维化。结论这3种方法都可以引起大鼠肝脏发生纤维化,其中胆管结扎致SD大鼠肝纤维化造模方法适合于临床胆汁淤积所致肝纤维化的模型建立,其它两种方法适合于化学性、病毒性肝炎引起的肝纤维化模型的建立,可根据不同的实验目的选择不同的方法构建相应的动物模型。     

Hepatic homing of mononuclear inflammatory cells isolated during murine chronic graft-vs-host disease

Liver injury in murine chronic graft-vs-host disease (CGVHD) to minor histocompatibility Ag, B10.D2----BALB/c (600 rad), is characterized by mononuclear cell inflammation and necrosis of interlobular bile ducts. Bile duct destruction in this model is similar to that which occurs in human CGVHD, late liver transplant rejection, and primary biliary cirrhosis. This model provides a unique opportunity to isolate mononuclear inflammatory cells from the liver during CGVHD, study their functions, and investigate the immunologic mechanisms responsible for bile duct destruction. In the present study, we compared the in vivo organ homing of mononuclear inflammatory cells (MC) isolated from the liver and spleen during the course of CGVHD. MC isolated from the liver showed a progressive increase in homing to the livers of BALB/c mice from day 7 through 42. In contrast, the hepatic homing of MC isolated from the spleen peaked at day 21 and subsequently declined. CGVHD spleen MC showed a progressive increase in homing to the spleen of BALB/c mice whereas CGVHD liver MC showed no change over time. Homing to other organs was negligible. The hepatic and splenic homing of MC isolated during CGVHD was significantly greater in BALB/c (host) mice than in B10.D2 (donor) mice. Autoradiography was used to determine the intrahepatic sites at which CGVHD liver MC accumulate after i.v. injection into BALB/c mice. The results indicated that MC isolated from the liver when bile duct inflammation is most intense accumulate preferentially in hepatic portal spaces in close proximity to interlobular bile ducts. These results suggest that hepatic homing by CGVHD liver MC is specific for minor histocompatibility Ag expressed on host biliary epithelial cells. These data support the hypothesis that bile duct destruction in murine CGVHD is mediated by MC that are sensitized to minor histocompatibility Ag expressed by host biliary epithelial cells.     

Rotavirus Replication in the Cholangiocyte Mediates the Temporal Dependence of Murine Biliary Atresia

Biliary atresia (BA) is a neonatal disease that results in obliteration of the biliary tree. The murine model of BA, which mirrors the human disease, is based upon infection of newborn mice with rhesus rotavirus (RRV), leading to an obstructive cholangiopathy. The purpose of this study was to characterize the temporal relationship between viral infection and the induction of this model. BALB/c mice were infected with RRV on day of life (DOL) 0, 3, 5, and 7. Groups were characterized as early-infection (infection by DOL 3) or late-infection (infection after DOL 5). Early RRV infection induced symptoms in 95% of pups with a mortality rate of 80%. In contrast, late infection caused symptoms in only 50% of mice, and 100% of pups survived. The clinical findings correlated with histological analysis of extrahepatic biliary trees, cytokine expression, and viral titers. Primary murine cholangiocytes isolated, cultured, and infected with RRV yielded higher titers of infectious virus in those harvested from DOL 2 versus DOL 9 mice. Less interferon alpha and beta was produced in DOL 2 versus DOL 9 RRV infected primary cholangiocytes. Injection of BALB/c interferon alpha/beta receptor knockout (IFN-αβR^−/−) pups at DOL 7 showed increased symptoms (79%) and mortality (46%) when compared to late infected wild type mice. In conclusion, the degree of injury sustained by relatively immature cholangiocytes due to more robust RRV replication correlated with more severe clinical manifestations of cholangiopathy and higher mortality. Interferon alpha production by cholangiocytes appears to play a regulatory role. These findings confirm a temporal dependence of RRV infection in murine BA and begin to define a pathophysiologic role of the maturing cholangiocyte.     

Alteration of the Thymic T Cell Repertoire by Rotavirus Infection Is Associated with Delayed Type 1 Diabetes Development in Non-Obese Diabetic Mice

Rotaviruses are implicated as a viral trigger for the acceleration of type 1 diabetes in children. Infection of adult non-obese diabetic (NOD) mice with rotavirus strain RRV accelerates diabetes development, whereas RRV infection in infant NOD mice delays diabetes onset. In this study of infant mice, RRV titers and lymphocyte populations in the intestine, mesenteric lymph nodes (MLN) and thymus of NOD mice were compared with those in diabetes-resistant BALB/c and C57BL/6 mice. Enhanced intestinal RRV infection occurred in NOD mice compared with the other mouse strains. This was associated with increases in the frequency of CD8αβ TCRαβ intraepithelial lymphocytes, and their PD-L1 expression. Virus spread to the MLN and T cell numbers there also were greatest in NOD mice. Thymic RRV infection is shown here in all mouse strains, often in combination with alterations in T cell ontogeny. Infection lowered thymocyte numbers in infant NOD and C57BL/6 mice, whereas thymocyte production was unaltered overall in infant BALB/c mice. In the NOD mouse thymus, effector CD4⁺ T cell numbers were reduced by infection, whereas regulatory T cell numbers were maintained. It is proposed that maintenance of thymic regulatory T cell numbers may contribute to the increased suppression of inflammatory T cells in response to a strong stimulus observed in pancreatic lymph nodes of adult mice infected as infants. These findings show that rotavirus replication is enhanced in diabetes-prone mice, and provide evidence that thymic T cell alterations may contribute to the delayed diabetes onset following RRV infection.     

The rhesus rotavirus gene encoding VP4 is a major determinant in the pathogenesis of biliary atresia in newborn mice

Biliary atresia (BA) is a devastating disease of childhood for which increasing evidence supports a viral component in pathogenesis. The murine model of BA is induced by perinatal infection with rhesus rotavirus (RRV) but not with other strains of rotavirus, such as TUCH. To determine which RRV gene segment(s) is responsible for pathogenesis, we used the RRV and TUCH strains to generate a complete set of single-gene reassortants. Eleven single-gene "loss-of-function" reassortants in which a TUCH gene replaced its RRV equivalent and 11 single-gene "gain-of-function" reassortants in which an RRV gene replaced its TUCH equivalent were generated. Newborn BALB/c mice were inoculated with the reassortants and were monitored for biliary obstruction and mortality. In vitro, the ability to bind to and replicate within cholangiocytes was analyzed. Infection of mice with the "loss-of-function" reassortant R(T(VP4)), where gene 4 from TUCH was placed on an RRV background, eliminated the ability of RRV to cause murine BA. In a reciprocal fashion, the "gain-of-function" reassortant T(R(VP4)) resulted in murine BA with 88% mortality. Compared with those for RRV, R(T(VP4)) binding and titers in cholangiocytes were significantly attenuated, while T(R(VP4)) binding and titers were significantly increased over those for TUCH. Reassortants R(T(VP3)) and T(R(VP3)) induced an intermediate phenotype. RRV gene segment 4 plays a significant role in governing tropism for the cholangiocyte and the ability to induce murine BA. Gene segment 3 did not affect RRV infectivity in vitro but altered its in vivo effect.     

Roles of VP4 and NSP1 in determining the distinctive replication capacities of simian rotavirus RRV and bovine rotavirus UK in the mouse biliary tract

Rotavirus replication and virulence are strongly influenced by virus strain and host species. The rotavirus proteins VP3, VP4, VP7, NSP1, and NSP4 have all been implicated in strain and species restriction of replication; however, the mechanisms have not been fully determined. Simian (RRV) and bovine (UK) rotaviruses have distinctive replication capacities in mouse extraintestinal organs such as the biliary tract. Using reassortants between UK and RRV, we previously demonstrated that the differential replication of these viruses in mouse embryonic fibroblasts is determined by the respective NSP1 proteins, which differ substantially in their abilities to degrade interferon (IFN) regulatory factor 3 (IRF3) and suppress the type I IFN response. In this study, we used an in vivo model of rotavirus infection of mouse gallbladder with UK × RRV reassortants to study the genetic and mechanistic basis of systemic rotavirus replication. We found that the low-replication phenotype of UK in biliary tissues was conferred by UK VP4 and that the high-replication phenotype of RRV was conferred by RRV VP4 and NSP1. Viruses with RRV VP4 entered cultured mouse cholangiocytes more efficiently than did those with UK VP4. Reassortants with RRV VP4 and UK NSP1 genes induced high levels of expression of IRF3-dependent p54 in biliary tissues, and their replication was increased 3-fold in IFN-α/β and -γ receptor or STAT1 knockout (KO) mice compared to wild-type mice. Our data indicate that systemic rotavirus strain-specific replication in the murine biliary tract is determined by both viral entry mediated by VP4 and viral antagonism of the host innate immune response mediated by NSP1.