唾液乳杆菌Ls04对小鼠肠道菌群及黏膜SIgA质量浓度的影响

对唾液乳杆菌Ls04对小鼠肠道微生物区系和肠黏膜分泌型免疫球蛋白A(SIgA)质量浓度的影响及其持续作用效果进行了研究。将100只SPF雄性昆明白小鼠随机分为Ls高、中、低剂量组及对照组,进行15 d灌胃,将灌胃前、灌胃15 d各处理组小鼠,及灌胃结束后第3,7,14天Ls中剂量组小鼠断颈处死,刮取其大肠黏膜、小肠黏膜,分别进行肠道中乳杆菌、双歧杆菌、肠杆菌、肠球菌和产气荚膜梭菌的计数及肠黏膜SIgA质量浓度的测定。结果表明,灌胃Ls04能显著提高小鼠肠道中乳杆菌、双歧杆菌数量,降低肠杆菌、肠球菌、产气荚膜梭菌数量,且Ls中剂量为最适;灌胃结束后14 d,小鼠肠道中乳酸菌、双歧杆菌数量仍高于灌胃前数量,且肠杆菌仍被显著抑制;灌胃15 d,Ls中剂量组小鼠肠黏膜SIgA质量浓度显著升高,且显著高于Ls高剂量组;灌胃结束后小鼠肠黏膜SIgA质量浓度至14 d显著降低,但仍显著高于灌胃前水平。结果表明,唾液乳杆菌Ls04停用后仍可显著增殖肠道有益菌并抑制致病菌,同时能够有效提高肠黏膜SIgA含量,刺激机体免疫应答。     

分离自内蒙古传统发酵酸马奶中L.casei Zhng潜在益生特性的研究

从内蒙古地区蒙古族家庭制作的16份酸马奶样品中分离得到的50株乳杆菌中，经耐酸性实验和人工胃肠消化液耐受性实验，筛选出1株对酸耐受性强的乳杆菌，为L.casei Zhang。将L.casei Zhang制成发酵乳后，其对人工胃肠消化液的耐受性要高于纯菌体，这是由于乳蛋白对消化液的缓冲作用和对菌体的保护作用所致。L.casei Zhang对介质中胆盐的最大耐受浓度为1．6g／100mL。L．casei Zhang具有一定的胆盐水解酶活性，可以分解培养介质中的牛磺胆酸钠释放出游离胆酸；L.casei Zhang在37℃培养24h可脱除培养介质中49．61％的胆固醇。这一结果表明，L.casei Zhang可以作为潜在的益生菌。     

茶多酚对大强度耐力运动小鼠免疫功能的影响

目的:探讨茶多酚对大强度耐力运动小鼠免疫功能的影响。方法:建立大强度耐力训练动物模型,测定小鼠腹腔巨噬细胞和淋巴细胞增殖能力、脾T淋巴细胞的CD3+、CD4+、CD8+细胞比率和血清SIgA、IgM和IgG。结果:茶多酚组与运动组比较,小鼠腹腔巨噬细胞和淋巴细胞增殖能力显著增强,脾T淋巴细胞的CD3+、CD4+、CD8+细胞比率显著增加,血清SIgA、IgM和IgG含量显著增加。结论:茶多酚具有提高力竭小鼠免疫力的作用。     

干酪乳酪杆菌Zhang在酸和低温胁迫下“活的非可培养”态的诱导研究

为探究干酪乳酪杆菌Zhang(Lacticaseibacillus casei Zhang)在酸和低温胁迫下能否形成活的非可培养(viable but non-culturable, VBNC)状态。该实验将L.casei Zhang置于不同pH值(2.5、3、4、5、6)的MRS液体培养基中，在4℃条件下进行酸和低温胁迫，不同时间点取样，然后采用平板计数法、荧光显微镜和流式细胞术3种方法对胁迫后的菌体进行活性测定。实验结果显示，低温条件下L.casei Zhang在pH值为2.5、3、5、6胁迫下未获得VBNC态；L.casei Zhang在pH 4的MRS液体培养基低温胁迫120 d获得了VBNC态，革兰氏染色观察到VBNC态细胞长度变短变弯曲。该研究为L.casei Zhang VBNC态的机理研究提供了一定的参考依据。     

在不同营养水平日粮中添加益生菌对肉鸡抗氧化功能、黏膜免疫及回肠菌群的影响

采用2×2因素设计,研究在不同营养水平日粮中添加益生菌对肉鸡免疫器官指数、血清和肠黏膜抗氧化性能、肠黏膜IgG和SIgA及回肠菌群的影响,评价益生菌在宿主内的免疫效应及其机理。试验选用1日龄AA肉鸡320只,分成4组,每组10个重复,每个重复8只,饲喂以下4种日粮:(1)正对照组(NC):基础日粮;(2)负对照组(LC):低能低蛋白日粮,使基础日粮的代谢能降低320 kJ/kg,粗蛋白均降低0.85%;(3)试验1组(NP):基础日粮+0.01%益生菌;(4)试验2组(LP):低能低蛋白日粮+0.01%益生菌。结果表明,在不同营养水平下,益生菌能提高21 d肉鸡的胸腺指数(P<0.01)、脾脏指数和法氏囊指数(P<0.05),但不影响42 d免疫器官指数(P>0.05),可显著提高肉鸡21 d血清和肠黏膜总超氧化物歧化酶(T-SOD)的活性(P<0.05),降低肉鸡21 d血清丙二醛(MDA)的含量(P<0.01),对21 d肠黏膜MDA含量也有降低趋势(P=0.057),能极显著提高42 d血清T-SOD活性和总抗氧化能力(T-AOC)(P<0.01),显著降低42 d血清和肠黏膜MDA的含量(P<0.05);在不同营养水平日粮中添加益生菌对肠黏膜IgG的含量有提高趋势(P=0.077),显著提高42 d肠黏膜IgG和SIgA含量(P<0.05),能显著降低21 d、42 d回肠大肠杆菌数量(P<0.05),极显著提高21 d回肠乳酸杆菌的数量(P<0.01),对42 d回肠乳酸杆菌数量没有显著影响(P>0.05)。结果提示,在不同营养水平下添加益生菌能促进肉鸡前期的免疫器官生长和发育,增强血液和肠黏膜的抗氧化功能,促进肠黏膜免疫球蛋白分泌,并能促进回肠乳酸杆菌增殖,抑制大肠杆菌增殖。     

利用Lactobacillus casei Zhang开发益生菌新鲜干酪

通过添加不同比例Lactobacillus casei Zhang发酵剂制作新鲜干酪,并对其在新鲜干酪中的活力和添加Lactobacillus后新鲜干酪的理化性质进行了研究。结果表明,Lb.casei Zhang在新鲜干酪中具有较高的活力,添加2%、1%、0.5% Lb.casei Zhang发酵剂的干酪中,4℃冷藏开始前,Lb.casei Zhang活菌数分别为2.24×10~8 cfu/g,1.38×10~8 cfu/g,5.55×10~7 cfu/g,4℃冷藏28d后,Lb.casei Zhang存活率分别为99.12%,98.31%,98.61%。在制作过程中和4℃冷藏过程中,与空白组相比,添加Lb.casei Zhang对新鲜干酪的pH值、滴定酸度、蛋白水解活性影响都不显著(P>0.05)。     

益生菌L.casei Zhang和B.lactis V9在发酵乳中发酵特性的评价

以L.casei Zhang和B.lactis V9为研究对象,评价其发酵特性及对发酵乳品质的影响。研究结果显示,4℃下贮藏21 d,L.casei Zhang和B.lactis V9的添加对发酵乳的p H值、滴定酸度(TA)、黏度和持水性基本无影响;L.casei Zhang和B.lactis V9在发酵乳中存活稳定;B.lactis V9的添加可促进L.casei Zhang的增殖,同时可进一步改善L.casei Zhang发酵乳的气味和风味。     

Lactobacillus casei Zhang和Bifidobacterium lactis V9在益生菌酸乳中的应用

益生菌在酸乳中的应用已非常普遍,将Lactobacillus casei Zhang单独(样品A)以及与Bifidobacterium lactis V9复合(样品B),同酸乳发酵剂(G027)共同发酵益生菌酸乳,于4℃贮藏21 d。结果表明,整个贮藏期间2组样品间的黏度和持水性差异不显著;贮藏期间2组样品间L.casei Zhang的活菌数没有差异,且L.casei Zhang和B.lactis V9的活菌数不随贮藏时间而降低;L.casei Zhang和B.lactis V9复合益生菌酸奶感官评价优于单独添加L.casei Zhang酸乳。L.casei Zhang和B.lactis V9复合添加,更适合于益生菌酸乳的生产。     

对虾原肌球蛋白致敏小鼠模型的构建及乳酸菌肠黏膜免疫效应对致敏性的影响

以原肌球蛋白（tropomyosin,TM）为主要过敏原,腹腔注射6 周龄BALB/c雌、雄小鼠,从第14天开始给治疗组小鼠口服灌胃长双歧杆菌婴儿亚种（Bifidobacterium longum subsp.）1.2202或芽孢乳酸菌09.712（Bacillus coagulans 09.712）,连续灌胃20 d。根据小鼠腹泻情况、过敏症状评分、血清中组胺（histamine,HIS）质量浓度、TM特异性免疫球蛋白（immunoglobulin,Ig）E水平变化构建TM致敏及益生菌治疗小鼠模型;通过氯乙酸萘酚酯酶染色、高碘酸希夫试剂特殊染色法检测各组小鼠肠道部位的肥大细胞和杯状细胞,通过免疫组化法检测各组小鼠肠道部位的CD4＋ T细胞和嗜酸性粒细胞;探究肠黏膜免疫在TM致敏及益生菌缓解TM致敏作用中的机理。结果表明：雌性小鼠更适用于构建TM致敏模型;益生菌灌胃可以通过降低血清中HIS质量浓度和IgE水平缓解肠黏膜免疫反应,减轻TM过敏症状。本研究从肠黏膜免疫反应角度探究了其在TM致敏中的作用,为食物过敏的研究提供参考。     

益生菌Lactobacillus casei Zhang和Bifidobacterium lactis V9在活性乳酸菌饮料中的应用

以L.casei Zhang和B.lactis V9为发酵菌株制备活性乳酸菌饮料,评价2株益生菌对活性乳酸菌饮料感官品质的影响及在货架期内的存活稳定性,为L.casei Zhang和B.lactis V9在产品中的应用提供基础数据。研究结果显示,利用L.casei Zhang单独发酵制备活性乳酸菌饮料的最适添加量为1.0×107CFU/g,4℃28 d贮藏期内保持高于3.0×108CFU/g水平;最佳复配发酵组合为L.casei Zhang+B.animalis V9(1∶1,2.0×107CFU/g),4℃28 d贮藏期内样品中总的益生菌活菌数保持5.0×108CFU/g以上,且在口感和滋气味方面感官评价分值最高;B.animalis V9与L.casei Zhang共同发酵发生协同效应,B.animalis V9的添加可促进L.casei Zhang的增殖,且有利于改善L.casei Zhang单株发酵样品的感官品质。     

红毛藻多糖对环磷酰胺诱导的免疫抑制小鼠的免疫调节机理

本研究以环磷酰胺（cyclophosphamide,CTX）诱导的免疫力低下小鼠为模型,探究红毛藻多糖（Bangia fusco-purpurea polysaccharides,BFP）对免疫抑制小鼠免疫力的影响。结果表明,BFP干预能够显著提高免疫抑制小鼠自然杀伤细胞活性、巨噬细胞吞噬能力和清除碳颗粒能力;增强T淋巴细胞增殖作用,上调CD4＋ T细胞比例,降低CD8＋ T细胞比例并增加CD4＋/CD8＋,降低辅助性T细胞17和CD3－CD19＋ B细胞的比例;提高血清溶血素、免疫球蛋白（immunoglobulin,Ig）A和IgG、免疫相关细胞因子白细胞介素（interleukin,IL）-2、IL-6、肿瘤坏死因子-α（tumor necrosis factor-α,TNF-α）、干扰素-γ（interferon-γ,INF-γ）的质量浓度,对免疫抑制小鼠的非特异性免疫、细胞免疫及体液免疫均具有良好的调节作用。在明确BFP对免疫抑制小鼠免疫功能具有保护作用的基础上,分析其对免疫抑制小鼠肠道相关免疫细胞表面受体的影响,发现BFP能够显著或极显著下调Toll样受体（Toll-like receptor,TLR）2、TLR4、IL-6和TNF-α基因（P＜0.05）和蛋白（P＜0.01）的表达,推测BFP通过TLR2/TLR4下游相关信号通路调节轴发挥增强免疫力的功能。本研究可为深入认识海洋食品的营养价值,推进海洋食品在居民膳食中的应用提供科学依据。     

Effect of fermented milk containing probiotic bacteria in the prevention of an enteroinvasive Escherichia coli infection in mice

This study investigated the protective capacity of the oral administration of fermented milk containing the probiotic strains; Lactobacillus casei, Lb. delbrueckii subsp. bulgaricus and Streptococcus thermophilus, against enteroinvasive Escherichia coli infection in a murine (BALB/ c mice) model. Mice were fed for 2, 5 or 7 consecutive days with fermented milk diluted to a concentration of viable Lb. casei, Lb. delbrueckii subsp. bulgaricus and Strep. thermophilus of 10(7) cfu/ml. Phagocytic activity of peritoneal macrophages and the number of IgA+ cells in small and large intestine were determined at the end of the feeding periods. For the preventive effect against Esch. coli, animals were fed for 5 days (selected dose). Mice were challenged with an infective dose of enteroinvasive Esch. coli of 10(8) cfu/mouse. The colonization of liver and spleen and the secretory IgA specific for the pathogen in the intestinal fluid were determined (ELISA test). Results showed that the unspecific immune response enhanced itself after 5 consecutive days of the administration of this fermented milk (increase in the percentage of phagocytosis and number of IgA+ cells in the small intestine). Treated animals showed less Esch. coli colonization of liver than control mice and a higher secretory anti-Esch. coli IgA in the intestinal fluids. These results suggest that the protection against enteroinvasive Esch. coli infection observed for the fermented milk containing probiotic bacteria may be associated with an enhance of the intestinal mucosa immunity.     

瑞士乳杆菌对小鼠肠道粘膜免疫应答及细胞因子的影响

探讨灌胃瑞士乳杆菌(Lactobacillus helveticus TS206)发酵制品对健康Balb/c 小鼠肠道黏膜免疫应答及细胞因子的影响。本实验将Balb/c 小鼠分为空白对照组、生理盐水组和瑞士乳杆菌组3 组,瑞士乳杆菌组的灌胃剂量为108CFU/mL,分别在灌胃后0 、1 、2、3 、4 、6 、8、12、24h 处死小鼠得到小肠组织样品,利用RIA 法和ELISA 法测得各组小鼠肠道黏膜SIgA 和细胞因子的含量,并作统计分析。结论：灌胃组小鼠肠道黏膜中SIgA 的含量与生理盐水对照组相比差异极显著(P ＜ 0.01);灌胃组小鼠肠道黏膜中IL-2 和IFN-γ的含量与生理盐水对照组相比具有显著性差异(P ＜ 0.05);灌胃组IL-4 与生理盐水对照组相比含量明显升高(P ＜ 0.05);而灌胃组和生理盐水对照组相比IL-6 的表达水平后期差异不显著(P ＞ 0.05);IFN-γ/IL-4 的值处于相互拮抗的状况,表明瑞士乳杆菌对健康小鼠具有维护肠黏膜免疫平衡的作用,也对保持Th1/Th2 平衡状态具有明显的作用,即证实瑞士乳杆菌作为益生菌具有调控小鼠肠道黏膜免疫应答的功效。     

Study of the possible mechanisms involved in the mucosal immune system activation by lactic acid bacteria.

The induction of a mucosal immune response is not easy due to the development of oral tolerance, but under some conditions, bacteria can activate this immune system. Antigens administered orally can interact with M cells of Peyer's patches or bind to the epithelial cells. We have demonstrated that certain lactic acid bacteria are able to induce specific secretory immunity, and others will enhance the gut inflammatory immune response. The aim of this work was to establish the reason for these different behaviors and to define possible mechanisms involved in the interaction of lactic acid bacteria at the intestinal level. We studied IgA+ and IgM+ B cells comparatively in bronchus and intestine and CD4+ T cells and IgA anti-lactic acid bacteria antibodies in the intestinal fluid, induced by oral administration of Lactobacillus casei, Lb. delbrueckii ssp. bulgaricus, Lb. acidophilus, Lb. plantarum, Lb. rhamnosus, Lactococcus lactis, and Streptococcus salivarius ssp. thermophilus. The increase in the IgA+ B cells in the bronchus means that these lactic acid bacteria were able to induce the IgA cycle by interaction with M cells from Peyer's patches or intestinal epithelial cells. The IgM+ cells increased when the stimulus did not induce the switch from IgM+ to IgA+. The increase in the CD4+ cells suggests interaction of Peyer's patches and enhancement of the B- and T-cell migration. The anti-lactic acid bacteria antibody is related to the processing and presentation of the microorganisms to the immune cells. We demonstrated that Lb. casei and Lb. plantarum were able to interact with Peyer's patch cells and showed an increase in IgA-, CD4+ cells, and antibodies specific for the stimulating strain. Lactobacillus acidophilus induced gut mucosal activation by interaction with the epithelial cells without increase in the immune cells associated with the bronchus. Although Lb. rhamnosus and Strep. salivarius ssp. thermophilus interact with epithelial cells, they also induced an immune response against their epitopes. Lactococcus lactis and Lb. delbrueckii ssp. bulgaricus induced an increase of IgA+ cells entering the IgA cycle but not CD4+ cells; thus, these bacteria would have been bound to epithelial cells that activated B lymphocytes without processing and presenting of their epitopes. We did not determine specific antibodies against Lc. lactis or Lb. bulgaricus.     

Fermentation characteristics and transit tolerance of Lactobacillus casei Zhang in reconstituted mare milk during storage

The fermentation characteristics of Lactobacillus casei Zhang in mare milk and transit tolerance during refrigerated storage for 28 days were evaluated. There were no dramatic changes in the viable counts of L. casei Zhang in the fermented mare milk samples during storage at various inoculation levels. L. casei Zhang showed good tolerance to the simulated transit juice and maintained high viability in mare milk (above 10⁸cfu/g) during storage. Our results showed that L. casei Zhang had good probiotic properties, and suggest that mare milk could serve as the vehicle for the delivery of L. casei Zhang.     

酪蛋白糖巨肽对小鼠肠道免疫系统的影响

研究酪蛋白糖巨肽(CGMP)对正常小鼠肠相关淋巴组织的免疫应答反应的影响,对阐述CGMP 的生物学功能具有重要意义。本实验将BALB/c 雌性小鼠28 只随机分为4 组,每组7 只,分别为0.9% 生理盐水对照组(0.2mL/d),低、中、高3 种剂量组(30、120、300μg/d)。连续灌胃16d 后,取脾脏、PP 结(peyer s patches)和肠系膜淋巴结(mesenteric lymph node,MLN),制备细胞悬液,进行三色荧光标记后,用流式细胞仪检测CD3+、CD3+CD4+ 和CD3+CD8+T 淋巴细胞亚群的变化。结果表明：CGMP 各剂量组均能够促进脾脏和PP 结中CD3+ 和CD3+CD4+ 细胞的显著增加(P ＜ 0.05),高剂量能引起脾脏CD3+CD8+ 淋巴细胞的显著增多(P ＜ 0.05),低剂量能引起脾脏CD3+CD4+/ CD3+CD8+ 的显著增加(P ＜ 0.05);低剂量CGMP 能使MLN 中CD3+CD8+ 淋巴细胞显著增减少(P ＜ 0.01)。研究证实长期灌胃CGMP 会诱导肠黏膜产生获得性的免疫应答,并且不会引起机体产生口服耐受。     

乳杆菌Lb.casei.Zhang对小鼠血清中细胞因子水平的影响

目的:观察及评价乳杆菌Lb.caseiZhang对小鼠血清中IFN-γ、IL-12、IL-1α、TNF-α水平的影响。方法:应用分离自酸马奶,并经过耐酸性实验、人工胃肠消化液中存活能力筛选的L.caseiZhang,制备成热致死菌体和活菌制剂各分成高、中、低三个剂量组灌服小鼠至15d,采用ELISA法检测血清中IFN-γ、IL-12、IL-1α、TNF-α的含量。结果:活菌制剂高、中剂量组小鼠血清中IFN-γ、IL-12含量明显高于对照组(p<0.05),IL-1α、TNF-α含量明显低于对照组(p<0.01);灭活菌制剂对细胞因子的影响与对照相比无显著差异。结论:Lb.caseiZhang活菌制剂的免疫调节作用优于热致死菌体制剂。活菌制剂对小鼠的细胞免疫功能产生了多方面的、有利于机体免疫功能状态的调节作用。     

嗜酸乳酸杆菌对自主活动受限型应激小鼠肠道黏膜免疫状态的影响

目的：探讨嗜酸乳酸杆菌（Lactobacillus acidophilus,LA）对自主活动受限型应激小鼠肠道黏膜免疫状态的影响。方法：以健康雌性BALB/c小鼠为受试动物,分为常规饲养组（NC组）、常规饲养条件灌胃LA组（NC＋LA组）、应激组（S组）、应激条件灌胃LA组（S＋LA组）,小鼠的LA灌胃剂量为108 CFU/d;应激组小鼠每天被限制自主活动3 h;15 d后取材,采用流式细胞术、酶联免疫吸附（enzyme-linked immunosorbent assay,ELISA）等方法,对肠系膜淋巴结（mesenteric lymph nodes,MLN）中CD4＋T细胞、CD8＋T细胞和CD11c＋树突细胞（CD11c＋ dendritic cell,CD11c＋ DC）比例,结肠组织白细胞介素-10（interleukin-10,IL-10）和白细胞介素-17（interleukin-17,IL-17）水平,以及小肠总分泌型免疫球蛋白A（secreted immunoglobulin A,sIgA）水平进行检测。结果：常规饲养条件下,LA能极显著提高小鼠MLN中CD4＋T细胞比例（P＜0.01）,显著提高MLN中CD11c＋ DC比例、小肠总sIgA水平和结肠组织IL-10水平（P＜0.05）,显著降低结肠组织IL-17水平（P＜0.05）,而对MLN中CD8＋T细胞比例无显著影响（P＞0.05）;应激条件能极显著降低小鼠MLN中CD4＋T细胞比例和CD11c＋ DC比例（P＜0.01）,显著降低CD8＋T细胞比例（P＜0.05）,极显著降低小鼠结肠组织IL-10水平和小肠总sIgA水平（P＜0.01）,极显著提高结肠组织IL-17水平（P＜0.01）;应激条件下,LA能显著提高小鼠MLN中CD4＋T细胞比例和CD11c＋ DC比例（P＜0.05）,显著提高小鼠结肠组织IL-10水平和小肠总sIgA水平（P＜0.05）,并显著降低结肠组织IL-17水平（P＜0.05）,而对小鼠MLN中CD8＋T细胞比例无显著影响（P＞0.05）。结论：给予自主活动受限型应激小鼠LA干预,可提高小鼠MLN中CD4＋T细胞和CD11c＋ DC比例,上调结肠IL-10和小肠总sIgA分泌水平,下调结肠IL-17分泌水平,调节应激小鼠的肠道黏膜免疫状态。     

Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 feeding enhances humoral immune responses,which are suppressed by the antiviral neuraminidase inhibitor oseltamivir in influenza A virus–infected mice

Antiviral neuraminidase inhibitors, such as oseltamivir, zanamivir, and peramivir, are widely used for treatment of influenza virus infection. We reported previously that oseltamivir inhibits the viral growth cycle, ameliorates symptoms, and reduces viral antigen quantities. Suppressed viral antigen production, however, induces a reduction of acquired antiviral humoral immunity, and increases the incidence of re-infection rate in the following year. To achieve effective treatment of influenza virus infection, it is necessary to overcome these adverse effects of antiviral neuraminidase inhibitors. Feeding of yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) OLL1073R-1 is reported to have immune-stimulatory effects on influenza virus infection in mice and humans. In the present study, we assessed the effect of feeding L. bulgaricus OLL1073R-1 yogurt cultures (YC) on local and systemic humoral immune responses, which were suppressed by oseltamivir treatment, in mice infected with influenza A virus. Yogurt culture (1.14 × 10⁸ cfu/0.4 mL per mouse per day) or sterile water (vehicle) was administered by intragastric gavage for 35 d. At d 22, influenza A virus/Puerto Rico/8/34 (H1N1) (PR8; 0.5 pfu/15 μL per mouse) was instilled intranasally, followed immediately by oral administration of oseltamivir (50 μg/100 μL per mouse, twice daily) or 5% methylcellulose (100 μL/mouse) as a vehicle for 13 d. Titers of anti-PR8-specific IgG and IgA in serum and mucosal secretory IgA (S-IgA) and IgG in bronchoalveolar lavage fluid (BALF) were analyzed by ELISA at 14 d after infection. Oseltamivir significantly suppressed the induction of anti-PR8-specific IgG and IgA in serum and S-IgA and IgG in BALF after infection. Feeding YC mildly but significantly stimulated production of PR8-specific IgA in serum, S-IgA in BALF, and IgG in serum without changing the IgG_2a:IgG₁ ratio. We analyzed the neutralizing activities against PR8 in serum and BALF and found that oseltamivir also reduced protective immunity, and YC feeding abrogated this effect. The immune-stimulatory tendency of YC on anti-PR8-specific IgA and IgG titers in serum and BALF was also detected in mice re-infected with PR8, but the effect was insignificant, unlike the effect of YC in the initial infection.