Systemic and local antibody responses after experimental infection with Actinobacillus pleuropneumoniae in piglets with passive or active immunity

The objectives of the present study was to describe different dynamics of humoral immune responses to experimental infection in piglets of different stages of infection and immunity. Two groups of piglets originating from non-immune (group 1) and immune (group 2) sows at the age of 3 weeks were subdivided as follows: a half of each group of piglets was exposed to a low-dose infection with Actinobacillus pleuropneumoniae (APP) strain 9. At the age of 8 weeks, all four groups of piglets were challenged with a high infection dose of APP of the same strain. Isotype characterization of the specific antibodies in sera and in bronchoalveolar lavage fluids (BALF) to a lipopolysaccharide was carried out, besides monitoring clinical signs and post-mortem examinations. A typical primary immune response was observed in specific antibody-free piglets infected with a challenge infection. Colostrum-derived immunoglobulin-G (IgG) antibodies persisted in sera and BALF of piglets up to the age of 8 weeks. However, they did not prevent induction of specific-primary antibody response, either in 8 or 4 weeks of age, when levels of specific colostrum-derived antibodies were still high. It was demonstrated by the increase of specific IgM antibodies in sera. The infection induced an increase in the levels of IgA antibodies in BALF regardless the severity of infection and presence of specific colostrum-derived antibodies. The specific antibodies of IgG isotype increased only in BALF from piglets without colostrum-derived antibodies.     

In utero infection with porcine reproductive and respiratory syndrome virus modulates leukocyte subpopulations in peripheral blood and bronchoalveolar fluid of surviving piglets

It is well known that piglets congenitally infected with porcine reproductive and respiratory syndrome virus (PRRSV) can be viremic at birth, and that preweaning mortality due to secondary infections often increases during acute outbreaks of PRRS. Therefore, an immunosuppressive effect of in utero infection has been suggested. The aim of the present study was to characterise the changes of leukocyte populations in piglets surviving in utero infection with PRRSV. A total of 27 liveborn uninfected control piglets and 22 piglets infected transplacentally with a Danish strain of PRRSV were included. At 2 and 4 weeks of age, 21 of 22 (96%) and 7 of 14 (50%) examined infected piglets were still viremic, whereas PRRSV could not be detected in the six infected piglets examined at 6 weeks of age. Flow cytometry analysis was used to determine the phenotypic composition of leukocytes in peripheral blood and bronchoalveolar lavage fluid (BALF) of 2-, 4- and 6-week-old infected piglets and age-matched uninfected controls. The key observation in the present study is that high levels of CD8(+) cells constitute a dominant feature in peripheral blood and BALF of piglets surviving in utero infection with PRRSV. In BALF, the average high level of CD8(+) cells in 2-week-old infected piglets (33.4 +/- 12.6%) was followed by a decline to 7.3 +/- 3.0 and 11.1 +/- 3.0% at 4 and 6 weeks of age. BALF of control piglets contained 1.6 +/- 0.9, 2.3 +/- 1.8 and 1.9 +/- 0.5% CD8(+) cells, only. In peripheral blood, however, the average number of CD8(+) cells remained at high levels in the infected piglets throughout the post-natal experimental period (2.8 +/- 1.9, 2.9 +/- 1.8 and 3.2 +/- 1.7 x 10(6) CD8(+) cells/ml at 2, 4 and 6 weeks, respectively). In the controls, the average levels of CD8(+) cells were 0.9+/-0.2, 1.9 +/- 1.7 and 1.6 +/- 0.5 x 10(6)/ml, respectively. Furthermore, the numbers of CD2(+) , CD4(+)CD8(+) and SLA-classII(+) cells, respectively, in peripheral blood, together with the levels of CD2(+) and CD3(+) cells in BALF were increased in the infected piglets infected in utero compared to the uninfected controls.The kinetic analyses carried out in the present study reflect that in utero infection with PRRSV modulates immune cell populations in peripheral blood and BALF of surviving piglets. The observed changes are characterised by high levels of CD8(+) cells supporting an important role of these cells in PRRSV infection. The present results, however, do not support the existence of post-natal immunosuppression following in utero infection with PRRSV.     

猪传染性胸膜肺炎与猪肺疫二联亚单位疫苗的免疫效果评价

为了评价猪传染性胸膜肺炎与猪肺疫二联亚单位疫苗(由多杀性巴氏杆菌外膜蛋白H(OmpH)质粒导入胸膜肺炎放线杆菌(APP)菌影制备)的免疫效果,于某规模化猪场选取30头无上述病原菌和抗体的4周龄(w)仔猪,随机分为安全评估组和试验组进行免疫,试验组包括APP组、OmpH组、APP+OmpH联苗组,分别于4、6 w肌肉注射2 mL/头相应疫苗,采取4、6、9 w外周血,用流式细胞术、ELISA、血常规、血生化试验分析疫苗免疫后,相关免疫因子、免疫细胞及免疫球蛋白的变化。结果显示:APP+OmpH组外周血中CD3⁺、CD8⁺细胞增加数量比APP、OmpH组显著增多(P<0.05);血清抗体结果显示,APP+OmpH组结果优于APP和OmpH组;APP+OmpH组的外周血白细胞数、淋巴细胞数、中性粒细胞数、单核细胞数在二免后增多,白蛋白、球蛋白亦明显增加,且APP+OmpH组增加数量多于APP和OmpH组。结论:APP+OmpH组能更好地刺激机体细胞免疫和体液免疫反应,进而发挥免疫保护效果。     

Distribution of immune cells in the female reproductive tract in uninfected and FIV infected cats

Cell-free and cell-associated FIV effectively cross the mucosa of the feline female reproductive tract. To identify possible cellular targets of FIV and to characterize changes in mucosal immunity after infection, we examined the types and numbers of immune cells residing in the reproductive tracts of control and intravaginally FIV-infected cats. Sections of the vestibule, vagina, cervix, uterus, and ovaries, were examined by immunohistochemistry for CD4+ and CD8+ T lymphocytes, CD22+ B lymphocytes, CD1a+ dendritic cells, and CD14+ macrophages. The reproductive tract of uninfected cats contained substantial numbers of CD8+ T lymphocytes, CD4+ T lymphocytes and macrophages, as well as moderate numbers of CD1a+ dendritic cells, and few B lymphocytes. The most prominent change between FIV- and FIV+ cats was a marked decrease in the concentration of CD4+ T lymphocytes resulting in inverted CD4+:CD8+ ratios throughout the reproductive tract of infected cats. There was also a trend towards increasing numbers of CD1a+ dendritic cells in the intravaginally-infected FIV+ cats, and decreasing numbers of macrophages and CD22+ B lymphocytes. This study indicates that similar to the peripheral immune system, FIV infection is associated with CD4+ cell loss and reduced CD4+:CD8+ ratios in the female reproductive mucosal tissue.     

Immunoperoxidase studies of cell mediated immune effector cell populations in early Mycobacterium avium subsp. paratuberculosis infection in sheep

Immunoperoxidase (IPX) labelling for CD4, CD8, TCR-gammadelta, WC1, CD1b, IFN-gamma, CD45R, CD56 and lysozyme was used to investigate changes in cell mediated immune effector cell populations in the intestinal Peyer's patches (PP) and mesenteric lymph nodes of lambs, 2 and 4 months after experimental infection with low doses of sheep strain Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis). The organism was cultured from the tissues of each infected lamb, but histological lesions were not present. This infection model was considered to be more representative of natural M. a. paratuberculosis infection than previous studies. Infected sheep had significantly more CD4+ cells in the mucosa, domes and interfollicular areas of the terminal ileum, and in the interfollicular areas of the jejunal Peyer's patch. Infected sheep also had significantly increased numbers of TCR-gammadelta+ cells in the mucosa and interfollicular areas of the jejunal Peyer's patch, and increased numbers of WC1+ cells in the ileal Peyer's patch. These findings are consistent with previous findings in sheep given higher doses of cattle strain M. a. paratuberculosis. Significantly fewer CD1b+ cells were present in the paracortical areas of the mesenteric lymph nodes of infected sheep, and the reduction was greater in sheep infected for 4 months compared to sheep infected for only 2 months. Down-regulation of CD1b expression may be important for the continued survival and multiplication of M. a. paratuberculosis as specific adaptive immunity develops. Across all sheep, jejunal Peyer's patches had higher numbers of CD4+, CD8+, TCR-gammadelta+, WC1+ and CD45R+ cells, and lower numbers of CD56+ fibres compared to ileal Peyer's patches. These findings confirm and extend the peculiarities of the terminal ileal Peyer's patch in the young ruminant, with possible implications for the early establishment of M. a. paratuberculosis infection.     

Effect on the immune system of germ-free piglets of probiotics potentiated with polyunsaturated fatty acids

The present study investigated the influence of polyunsaturated fatty acids (PUFA) on the immune system of germ-free piglets. Oil with increased content of omega-3 PUFA was administered to piglets from the experimental group (EG) for four weeks. Piglets from the control group (CG) received identical volumes of saline solution. At the age of 21 days both groups of germ-free piglets were inoculated perorally with Lactobacillus casei subsp. casei at a dose of 2 ml (1x10(8) mli). At the age of 28 days, i.e. after one-week colonisation of germ-free piglets with Lactobacillus casei subsp. casei, significant differences were recorded in phagocytic activity of neutrophils (PANe) and phagocytic activity of potentially phagocytizing cells (PA) (P < 0.05). Between EG and CG there have been observed no significant differences in absolute numbers of CD4+ and CD8+ T lymphocytes and numbers of IgM cells and in additional investigated parameters - number of CD2+ T lymphocytes, index of phagocytic activity of neutrophils (IPANe) and index of phagocytic activity (IPA).The total number of leukocytes (Le) in EG was also higher. Of the parameters determined in blood serum we observed a significant increase in concentration of alpha linolenic, eicosapentaenoic and docosahexaenoic acids and a parallel decrease in the level of arachidonic acid.     

The influence of age and maternal antibodies on the postvaccinal response against swine influenza viruses in pigs

The influence of age and maternal immunity on the development and duration of postvaccinal humoral response against swine influenza viruses (SIV) were investigated under experimental conditions. Piglets born to immune and non-immune sows were vaccinated twice with bivalent inactivated vaccine. Vaccination was done according to 5 different schedules: 1+4, 1+8, 4+8, 8+10 or 8+12 weeks of age. Antibodies to the haemagglutinin type 1 and 3 were determined using the haemagglutination inhibition (HI) test. Maternally derived antibodies (MDA) against H1N1 and H3N2 in the serum of unvaccinated piglets born to immune sows were above the positive level until about 13-14 and 9-10 weeks of life, respectively. No serological responses were seen in any of the groups after the first vaccination. After the second dose of vaccine production of antibodies was observed even before the complete disappearance of maternal antibodies. MDA, however, were associated with reduced antibody response. In MDA-negative piglets, an active humoral postvaccinal response was developed in all vaccinated pigs. The age at which the vaccine was given was associated with the differences in the magnitude of antibody response to SIV. In general those pigs that were vaccinated for the first time at the age of 1 week, developed lower maximum titres after the second vaccination, and become seronegative earlier than pigs that were vaccinated for the first time at 4 or 8 weeks of age.     

Bacillus cereus var. toyoi enhanced systemic immune response in piglets

Probiotic bacteria have been suggested to stimulate the host immune system. In this study we evaluated the immunomodulatory effects of probiotic Bacillus cereus var. toyoi on the systemic immunity of piglets. A pool of 70 piglets was divided into a probiotic or control group. We determined the ratios of peripheral blood mononuclear cell (PBMC) subsets and measured proliferative responses and cytokine production of PBMCs and effects on vaccination responses. Blood samples of probiotic-treated piglets showed a significantly lower frequency of CD8(high)/CD3+ T cells and CD8(low)/CD3+ T cells and a significant higher CD4+/CD8+ ratio. IL-4 and IFN-gamma production of polyclonally stimulated PBMCs was on average higher in the probiotic group. Specific proliferative responses of PBMCs to Influenza vaccination antigens were significantly higher and antibody titers against H3N2 Influenza and Mycoplasma vaccination antigens were on average higher in the probiotic group. In conclusion, B. cereus var. toyoi therefore alters the immune status of piglets as indicated by changes in the ratios as well as functionalities of systemic immune cell populations.     

Characterization of a single dose methylprednisolone acetate immune suppression model using Cryptosporidium muris and Cryptosporidium parvum

An immunosuppressive dose of methylprednisolone acetate (MPA) was compared with a non-immunosuppressive dose using Cryptosporidium oocyst production as an indicator of immunosuppression. To be classified as immunosuppressive, the dose had to satisfy five criteria. First, the dose had to abrogate normal immune defenses allowing the propagation of an organism to which the host is normally resistant, i.e. Cryptosporidium parvum in adult mice. Second, the dose had to decrease overall circulating CD4 T-lymphocyte numbers by greater than 80%. Third, the immunosuppressive dose had to prolong the infection beyond the normal infection length, and fourth, increase the severity of an active infection. Lastly, after complete recovery from a C. muris infection, immunosuppression must suppress the naturally acquired post infection immunity and allow reinfection. In mice immunosuppression with 600 mgMPA/kg lasted approximately 14 days and satisfied all five criteria. Fecal oocyst production could be perpetuated by dosing at 10-day intervals. A 200 mgMPA/kg dose transiently lowered CD4 counts by over 80%, but failed to override the naturally acquired post infection immunity or allow infection with C. parvum. The immunosuppressed blood profile consisted of an immediate sharp rise of mature segmented neutrophils combined with a severe decrease in circulating T-lymphocyte numbers. The rise and fall of neutrophils proved to be a good indicator of the severity and duration of immunosuppression. The thymus and spleen likewise contracted and then expanded in accordance with the steroid effect. The metabolism of MPA resulted in the eventual recovery of immune function signified by the cessation of C. parvum oocyst production. The recovery blood profile was associated with circulating CD8 counts near control levels, continuing 80% depression of CD4 counts and a dropping total neutrophil count. This study shows that the 600 mg/kg MPA dose is a good model for immunosuppression, which satisfies all five criteria for immunosuppression with low morbidity and low mortality.     

Lymphocyte subpopulations in peripheral blood of sheep experimentally infected with tick-borne fever.

The lymphocyte subpopulations in the peripheral blood of normal sheep and sheep experimentally infected with Cytoecetes phagocytophila, the causative agent of tick-borne fever, were analysed by flow cytometry, using a panel of monoclonal antibodies against specific lymphocyte epitopes. Experimental infection with tick-borne fever was characterised by a significant reduction in the total number of circulating lymphocytes six days after experimental infection (P less than 0.001). This lymphocytopenia was associated with a significant reduction in the number of B (LCAp220+) and T (CD5+) lymphocytes (P less than 0.001) but there was a significant increase in the number of cells which were neither T nor B (CD5-LCAp220-) cells (P less than 0.01). The reduction in the number of T lymphocytes was due to reduced numbers of circulating CD4+ (helper) T cells, CD8+ (cytotoxic/suppressor) T cells and those with the pan T cell marker (CD5+) but without CD4 or CD8 epitopes (CD4-CD8-). All lymphocytes returned to preinoculation levels 13 to 16 days after experimental infection.     

Early events in the immunopathogenesis of feline retrovirus infections.

Feline leukemia virus and feline immunodeficiency virus (FIV) are lymphotropic retroviruses that cause a wide range of diseases in domestic cats. Although it is known that both viruses are capable of infecting T lymphocytes and that infected cats are lymphopenic, it was not known how infection with either virus might alter specific lymphocyte subpopulations. Using a panel of monoclonal antibodies to feline lymphocyte subpopulations, we examined, by use of flow cytometric analysis, lymphocyte changes in cats naturally infected with FeLV or FIV and explored the early stages in the immunopathogenesis of experimentally induced infection with these viruses. Both groups of naturally infected cats had T-cell lymphopenia. In the FIV-infected cats, the T-cell decrease was principally attributable to loss of CD4+ cells, whereas CD8+ and B-cell numbers remained normal. This led to inversion of the CD4+ to CD8+ ratio in these cats. In contrast, the T-cell lymphopenia in FeLV-infected cats resulted from decrease in CD4+ and CD8+ cells, which led to a CD4+ to CD8+ ratio within normal limits. Experimentally induced infection with these 2 viruses supported these findings. Infection with FIV induced early (10 weeks after infection), chronic inversion of the CD4+ to CD8+ ratio. In contrast, infection with FeLV did not alter CD4+ to CD8+ ratio in the first 20 weeks after infection.     

Phenotypic analysis of peripheral leukocytes in piglets infected with classical swine fever virus.

The phenotypic changes in circulating leukocytes in swine fever influenced by classical swine fever virus (CSFV) infection with different strain virulence was studied in piglets. The phenotypic differences were measured by monoclonal antibodies specific for porcine differentiation antigens. The pattern of phenotypic change varied with the virulence of CSFV. Infection with virulent, but not the attenuated strain of CSFV resulted in the dramatic early loss of CD8-bearing T lymphocytes from the circulation. A similar trend was also seen in the gammadelta T-cell compartment following infection with the highly virulent strain, Washington. The loss of circulating B-lymphocytes was consistent with the failure to generate neutralising antibody. These observations contrasted the finding that the number of leukocytes expressing the CD4 surface antigen increased in piglets infected with CSFV. These data provide preliminary information on the potential range of leukocyte changes produced in piglets following infection with CSFV.     

Changes in macrophage and lymphocyte subpopulations of lymphoid tissues from pigs infected with the porcine reproductive and respiratory syndrome virus (PRRSV)

We used an immunohistochemical method to investigate changes in macrophage and lymphocyte subpopulations in various lymphoid tissues of pigs in the acute phase of porcine reproductive and respiratory syndrome virus (PRRSV) infection. The numbers of CD8+ cells and B-cells varied among lymphoid tissues after PRRSV infection. In the infected pigs, numbers of CD8+ cells increased in systemic lymphoid tissues whereas numbers of B-cells increased in mucosa-associated lymphoid tissues. There was no difference in the distribution of virus-infected cells and macrophages between lymphoid tissues of the infected pigs. These changes may be associated with the establishment of virus persistence or the emergence of concurrent infection in mucosal organs.     

Cytokines and acute phase proteins associated with acute swine influenza infection in pigs

This study set out to investigate the cytokines and acute phase proteins (APPs) associated with the acute stages of experimentally-induced swine influenza virus (SIV) infection in 3-week-old, colostrum-deprived, caesarean-derived piglets. The piglets were inoculated intratracheally with 10^7.5 50% egg infective dose [EID₅₀] Swine/Belgium/1/98 (H1N1) SIV and were euthanased at time-points between 0 and 120 h post-inoculation (PI). Broncho-alveolar lavage fluid (BALF), lung homogenates and sera were examined for inflammatory mediators by bioassay or ELISA. Interferon (IFN)-α, interleukin (IL)-6, IL-1 and tumour necrosis factor (TNF)-α peaked in BALF 24–30 h PI, when virus titres and the severity of clinical signs were maximal.Whereas IFN-γ and IL-12, but not IL-18, increased in tandem in BALF, serum cytokine concentrations were either undetectable or were up to 100-fold lower. The APP C-reactive protein (CRP) and haptoglobin peaked 24 h later than the cytokines and reached higher levels in serum than in BALF. In contrast, lipopolysaccharide (LPS)-binding protein (LBP) only increased in BALF. Lung virus titres tightly correlated with BALF IFN-α, IL-6, IL-1, TNF-α, IFN-γ and IL-12, as well as with serum IL-6, IFN-α and IFN-γ. Signs of disease correlated with the same cytokines in BALF and serum, as well as with BALF LBP and serum CRP. The findings suggest that IFN-γ and IL-12 play a role in the pathogenesis of SIV and that APPs are induced by cytokines. This influenza infection model may have value in assessing the therapeutic potential of cytokine antagonists.     

Effect of vitamin E supplementation on lymphocyte distribution in gut-associated lymphoid tissues obtained from weaned piglets

Fifteen piglets were used to determine the effect of vitamin E supplementation on the number of CD4-immunoreactive (CD4+) T-lymphocytes, CD8-immunoreactive (CD8+) T-lymphocytes and IgA-immunoreactive (IgA+) B-lymphocytes per follicle in the Peyer's patch of distal ileum and the mesenteric lymph nodes of weaned piglets. Piglets, following a 3-day adaptation period after weaning, were assigned to one of three experimental groups: control (no vitamin E supplementation), vitamin E supplementation of 100 mg/kg of diet and vitamin E supplementation of 300 mg/kg of diet. Supplementation of vitamin E lasted for a period of 36 days. The basal diet contained 80 mg alpha-tocopherol/kg of diet. All piglets were killed at day 39 after weaning and samples of the distal ileum and adjacent mesenteric lymph nodes were collected. The number of cells for each lymphocyte subset was counted in the Peyer's patch and the mesenteric lymph nodes follicles, in cryostat sections processed for immunohistochemistry. Results showed that vitamin E supplementation (300 mg/kg diet) of piglets caused an increase (P < 0.05) in the number of IgA+ B-lymphocytes in the Peyer's patch, but not in the mesenteric lymph nodes, compared with the corresponding values in control animals. Vitamin E supplementation had no effect (P > 0.05) on the number of CD4+ and CD8+ T-lymphocytes in the follicles of the Peyer's patch and the adjacent mesenteric lymph nodes. Thus, vitamin E had relatively minor effects on distribution of the major immunocompetent cells in the gut. The numbers of CD4+ and CD8+ T-lymphocytes as well as IgA+ B-lymphocytes per follicle were higher by 26-77% (P < 0.05) in the mesenteric lymph nodes than the corresponding values in the Peyer's patch.     

怀孕后期感染PRRS病毒母猪所产新生仔猪的免疫反应

将PRRS病毒BJ－4株感染怀孕后期（约90天）的抗体阴性和阳性母猪，待自然分娩后，观察新生仔猪的免疫应答。结果显示，接种PRRS病毒BJ－4的母猪没有表现出明显的临床症状，没有出现流产死产。新生仔猪浦被子前血清中PRRS病毒核酸TR－PCR检测和ELISA抗体阴性，哺乳后特异性抗体出现，5－6周母源抗体逐渐下降；20日龄猪瘟疫苗免疫后疫苗抗体维持时间短，仔猪在40日龄后进入野毒感染的危险期。RT－nested PCR检测血清中PRRS病毒核酸和易感仔猪病毒特异性抗体监测的结果提示仔猪群内可能存在水平传播。流式细胞术检测外周血淋巴细胞亚群发现CD3^ 细胞减少，CD4^ 细胞显著下降，CD8^ ，CD4^ CD8^ 和SLA－DR^ 表达细胞升高。以上结果表明在感染后病毒能够长期持续性存在，猪场内新生仔猪母源抗体逐渐下降后，通过水平传播受到感染，感染后免疫应答受到不利影响。     

Effect of maternally derived antibodies on the clinical signs and immune response in pigs after primary and secondary infection with an influenza H1N1 virus

The aim of this study was to determine the role of maternally derived antibodies (MDA) against an influenza H1N1 virus in the clinical protection of piglets and especially their effect on the development of the active immunity after an infection with a homologous influenza H1N1 virus. Twenty piglets with MDA and 10 piglets without MDA were housed together and inoculated twice with influenza H1N1 virus, at 7 and 15 weeks of age. Nine piglets without MDA were added to these groups at 12 weeks of age to be inoculated at 15 weeks of age only. Clinical signs, body temperature, growth performance, virus excretion, antibody responses, and influenza-specific T-cell response were monitored. It was shown that MDA protect piglets against the clinical consequences of a primary influenza infection, but that this protection is not complete. A short but significant rise in body temperature was observed and growth seemed to be inhibited due to the infection. Piglets with MDA shed virus for a longer period after an infection than piglets without MDA. Piglets with and without MDA were protected against the clinical consequences of a secondary infection. However, both after primary and secondary infection significant differences in immune responses were observed that indicated that pigs with MDA developed a weaker immunity than pigs without MDA. Furthermore, overall growth performances from weaning to slaughter show a trend in favour of pigs without maternal antibodies, compared to pigs with maternal antibodies, mainly caused by a significant better performance in the second half of the finishing period. The results of this study provide us insight in the role of MDA in clinical protection and their influence on active immunity after an influenza virus infection of pigs. Furthermore, it leads us to the discussion about the profitability of massive sow herd vaccinations in an attempt to increase MDA levels in piglets, taking into account the overall performance of these piglets and the possible effects on antigenic drift.     

酵母壁多糖对断奶仔猪外周血免疫和肠道免疫的影响

本试验旨在探讨饲粮中添加酵母壁多糖对断奶仔猪外周血免疫和肠道免疫的影响。采用单因素试验设计方法,选取21日龄遗传胎次、体重接近的断奶仔猪180头,随机分为4个组,每组5个重复,每个重复9头猪。4组分别饲喂饲粮中添加0(对照组)、0.15%、0.30%和0.45%酵母壁多糖的试验饲粮。试验期21 d。结果表明:1)与对照组相比,饲粮中添加0.15%、0.30%和0.45%酵母壁多糖显著提高了断奶仔猪血清免疫球蛋白A(IgA)含量(P0.05),饲粮中添加0.30%和0.45%酵母壁多糖显著提高了断奶仔猪血清免疫球蛋白G(IgG)含量(P0.05)。2)与对照组相比,饲粮中添加0.15%、0.30%和0.45%酵母壁多糖显著降低了断奶仔猪血清干扰素-γ(IFN-γ)含量(P0.05),饲粮中添加0.30%酵母壁多糖显著提高了断奶仔猪血清白细胞介素-10(IL-10)的含量(P0.05)。饲粮中添加酵母壁多糖对断奶仔猪血清白细胞介素-2(IL-2)、白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)含量均无显著影响(P0.05)。3)与对照组相比,饲粮中添加0.30%和0.45%酵母壁多糖显著提高了断奶仔猪回肠CD4~+淋巴细胞含量(P0.05),饲粮中添加酵母壁多糖能一定程度提高断奶仔猪回肠CD8~+和CD20~+淋巴细胞含量,但差异不显著(P0.05)。由此可知,酵母壁多糖能一定程度提高断奶仔猪外周血免疫和肠道免疫,缓解断奶应激。     

Blood lymphocyte subsets in pigs vaccinated and challenged with Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae bacterins do not induce protection in pigs while infection with low doses of the CM5 strain of A. pleuropneumoniae given by aerosol induces complete protection. To evaluate possible correlates of protection in blood lymphocyte subset phenotypes, pigs were treated with a commercial bacterin given intramuscularly, low dose (10(5)cfu/ml) aerosol infection with CM5 or control treatments of the bacterin adjuvant or phosphate buffered saline. All pigs were challenged with a high dose (10(7)cfu/ml) of A. pleuropneumoniae. Lymphocytes and sera were collected prior to and following primary and secondary immunizations and challenge, for evaluation of B- and T-cell markers and antibody to four A. pleuropneumoniae antigens. IgM(micro)+ B-cells were increased following primary exposure to antigen in the bacterin-vaccinated group only. An increase in CD4+ cells in the LD aerosol-infected group was apparent following secondary exposure to antigen. These early changes suggest little difference in lymphocyte populations between treatment groups, however, greater differences were observed following high-dose challenge; CD4+ lymphocytes were increased significantly in both bacterin and LD-challenged groups (p<0.05) while CD8+ cells decreased in the LD-group at this time period. Consequently, there were significant differences (p<0.05) in the CD4:CD8 ratio after high-dose challenge compared to earlier time points and control groups. Variation in cellular expression of SLA-DR and DQ was observed but trends correlating to treatment group were not evident. Complete protection or lack of protection associated with LD challenge or immunisation resulted in significant differences in B-cell frequencies and CD4:CD8 ratio phenotypes in pigs, but only changes in CD4:CD8 ratios appeared relevant to protection.     

T lymphocyte subset alterations following bluetongue virus infection in sheep and cattle

To determine potential mechanisms of differential disease expression in ruminants infected with bluetongue virus (BTV), clinically normal, BTV-seronegative, yearling sheep and cattle were infected subcutaneously with a standardized insect-source inoculum of BTV serotype 17 (BTV-17) (three infected and one contact control each) or animal adapted BTV serotype 10 (BTV-10) (three sheep only). BTV was isolated from peripheral blood cell components of infected sheep and cattle and all infected animals showed evidence of seroconversion by 14 days post infection (PI). Sheep infected with both serotypes of BTV developed pyrexia, oral lesions, and leukopenia which were most severe on days 7-8 PI. Analysis of peripheral blood mononuclear leukocytes with specific monoclonal antibodies and flow cytometry revealed panlymphocytopenia on day 7 PI. This response was further characterized by an increase in the CD4/CD8 ratio (greater than 3) resultant from a greater decrease in absolute numbers of circulating SBU-T8(CD8+) ("cytotoxic/suppressor") lymphocytes compared to SBU-T4 (CD4)+ ("helper") lymphocytes. SBU-T19+ lymphocytes were also decreased below baseline values on days 5-14 post infection. On day 14 PI there were increased CD8+ lymphocytes and decreased CD4/CD8 ratios (approximately 0.6) in these sheep. Clinical and hematologic changes in cattle infected with BTV-17 were minimal and consisted of mild pyrexia (rectal temperature 103 degrees F) on day 9 PI in two of three infected animals and mild leukopenia on several days PI in one animal. This leukopenia was the result of a pan T lymphocytopenia with CD4/CD8 ratios in the expected range (1-2). Similar to infected sheep, infected cattle did have a shift (decrease, approximately 0.8) in the peripheral CD4/CD8 ratio associated with an increase in circulating BoT8 (CD8)+ lymphocytes on day 14 post infection. Lymphocytes in the peripheral blood of all sheep and cattle infected with BTV-17 proliferated in vitro in response to purified BTV-17. These results confirm and extend those of previous studies that indicate species differences in the hematologic response to an equivalent BTV infection in domestic ruminants.