Effect of UV-irradiation,spleen cells and MLN cells on protective immunity againstAngiostrongylus cantonensis infection in mice

The UV-irradiated larvae ofAngiostrongylus cantonensis were used for inducing immunity in mice. A single oral dose of 100 infective UV-irradiated larvae exposed for 5 min or 15 min induced 91% and 97% protection against subsequent infection. Adoptive protection againstA. cantonensis could also be transferred by spleen and mesenteric lymph node cells obtained from vaccinated mice.     

In vitro effects of milbemycin oxime: mechanism of action againstAngiostrongylus cantonensis andDirofilaria immitis

The neuropharmacological mechanisms underlying the action of milbemycin oxime on the motility ofAngiostrongylus cantonensis andDirofilaria immitis were examined in vitro. InA. cantonensis, milbemycin oxime caused inhibitory effects at low concentrations of 10^–9 g/ml, and paralysis was elicited at 10^–8–10^–6 g/ml. The paralysis was antagonized by picrotoxin and bicuculline but not by dibenamine. In addition, stimulatory effects were observed when the antibiotic was used at higher concentrations of 3–5×10^–6 g/ml, and the action was antagonized by strychnine. Both effects were also observed in the preparation contracted by eserine or pyrantel. WhenD. immitis was treated with milbemycin oxime at concentrations of 10^–7 and 3–5×10^–6 g/ml, only slight inhibitory and stimulatory effects, respectively, were observed. These effects were partially antagonized by picrotoxin and strychnine, respectively. These results suggest that the inhibitory and stimulatory actions of milbemycin oxime are caused through gabergic and cholinergic mechanisms inA. cantonensis andD. immitis.Studies on chemotherapy of parasitic helminths XXIX     

Antibody responses in rats infected withAngiostrongylus cantonensis and the passive transfer of protective immunity with immune serum

Little haemagglutinating antibody was detected in the serum of rats with primaryAngiostrongylus cantonensis infections until the juvenile worms left the brain and lodged in the lungs about 35 days after infection. Antibody titres reached a peak 50 days after infection and were maintained for at least a further 95 days. Increasing the infective dose ofA. cantonensis larvae increased the peak antibody titres attained by the infected rats. Reinfection temporarily reduced the serum antibody titre, but later it increased and showed an anamnestic response. Reaginic antibody production was transient during primary infections; re-infection failed to stimulate further reaginic antibody production.Antiserum from immune donor rats protected recipients againstA. cantonensis. The transferred immune serum suppressed anti-A. cantonensis antibody production in recipient rats.     

Changes in worm burden,haematological and serological response in rats after single and multipleAngiostrongylus cantonensis infections

Summary Thirteen groups of rats were first sensitized with single or double doses of 5–30 third-stage larvae ofAngiostrongylus cantonensis, followed by a challenge infection with 100 larvae at various periods after the primary infection. Seven other groups of rats receiving only the sensitizing infection served as the controls. In all the sensitized rats, a significantly (p<0.05) smaller mean number of adult worms was found established in the challenge infection as compared to the control. The frequency of the sensitizing dose and timing of the challenge infection appeared to influence the intensity of the host's response. There was no conclusive evidence to indicate that the immune response could retard the growth, development, or sex ratios of the worms established in subsequent infections. A positive haemagglutinating antibody response was first observed in some rats as early as four weeks post-infection with 100 larvae when the worms began migrating from the brain to the lungs. The antibody response and eosinophilia were most pronounced during the oviposition of the female worms and hatching of firststage larvae. Changes in white blood cell, lymphocyte, and neutrophil counts were also followed in some groups.     

Passive immunity in rats infected withAngiostrongylus cantonensis: Interactions between syngeneic immune serum and sensitized lymph node cells

Immune serum injected into the peritoneum of rats passively protected them againstAngiostrongylus cantonensis; this protection was greater than that conferred by passively transferred immune lymph node cells. When immune lymph node cells and serum were transferred together into the same rat, no enhanced protection was observed. The protective effect of serum was inhibited by the lymph node cells to levels commensurate with those conferred by immune lymph node cells alone. Normal lymph node cells also depressed the levels of immunity conferred by immune serum when they were transferred together with serum, but to a lesser extent than did sensitized lymph node cells. Transferred antibody acted to suppress antibody production againstA. cantonensis in recipient rats.     

Protective efficacy of anti-Helicobacter pylori immunity following systemic immunization of neonatal mice

Helicobacter pylori infection of the gastric mucosa is a significant cause of morbidity and mortality because of its etiologic role in symptomatic gastritis, peptic ulcer disease, and gastric adenocarcinoma. Infection occurs in young children; therefore, a prophylactic vaccine would have to be administered within the first year of life, a period thought to be immunologically privileged. We investigated vaccine formulations administered by different routes to confer protective anti-H. pylori immunity in neonatal mice. Neonatal mice immunized with a single dose of vaccine in complete Freund's adjuvant (CFA) generated antigen-specific gamma interferon-, interleukin-2 (IL-2)-, IL-4-, and IL-5-secreting T cells in numbers similar to those in immunized adult mice, while vaccine administered to neonates in incomplete Freund's adjuvant (IFA) induced such cells in reduced numbers compared to those in adult mice. Both IFA and CFA, however, provided partial protection from a challenge with infectious H. pylori when the vaccine was administered subcutaneously. Neonatal immunized mice also had reduced bacterial loads when immunized intraperitoneally with CFA. In all cases, protection was equivalent to that achieved when adult counterparts were immunized. These studies suggest that an efficacious vaccine might be successfully administered to very young children to prevent perinatal infection of H. pylori.     

Cross-resistance betweenTrichinella spiralis andAngiostrongylus cantonensis in laboratory rats

Summary Rats were sensitized with one dose of 20, 30, or 100, or three doses of 30Trichinella spiralis larvae and then given a challenge infection with 100 third-stage larvae ofAngiostrongylus cantonensis during different periods of development ofT. spiralis. A significant reduction in the mean number of adultA. cantonensis was found in all the experimental groups. The mean number of lung worms found in the groups varied from 56 to 68, whereas a mean of 82 was found in the control. This reduction is probably caused by the non-specific inflammatory reaction and cell-mediated response induced byT. spiralis in the intestine and other organs of the host. A weaker and slower haemagglutinating antibody response againstA. cantonensis was observed in animals infected with both species of nematodes. This may be attributed to a suppressive action elicited byT. spiralis against unrelated antigens. Changes in differential and total white blood cell counts were followed in some infected animals. An increase in neutrophils 3–4 weeks after infection with either or both species of parasites was observed. Eosinophilia occurred primarily in the lung phase of the metastrongyloid infection.     

Tissue-specific immunity in helminth infections

A characteristic feature of host responses to helminth infections is the development of profound systemic and tissue-localised Type 2 immune responses that play critical roles in immunity, tissue repair and tolerance of the parasite at tissue sites. These same Type 2 responses are also seen in the tissue-associated immune-pathologies seen in asthma, atopic dermatitis and many forms of allergies. The recent identification of new subtypes of immune cells and cytokine pathways that influence both immune and non-immune cells and tissues creates the opportunity for reviewing helminth parasite–host responses in the context of tissue specific immunity. This review focuses on the new discoveries of the cells and cytokines involved in tissue specific immune responses to helminths and how these contribute to host immunity against helminth infection and allow the host to accommodate the presence of parasites when they cannot be eliminated.     

Protective heterologous immunity against fatal ehrlichiosis and lack of protection following homologous challenge

The roles of antibodies and memory T cells in protection against virulent Ehrlichia have not been completely investigated. In this study, we addressed these issues by using murine models of mild and fatal ehrlichiosis caused by related monocytotropic Ehrlichia strains. Mice were primed with either Ehrlichia muris or closely related virulent ehrlichiae transmitted by Ixodes ovatus (IOE) ticks given intraperitoneally or intradermally. All groups were reinfected intraperitoneally, 30 days later, with a lethal high dose of IOE. Priming with E. muris, but not IOE, induced strong CD4+ and CD8+ memory type 1 T-cell responses, Ehrlichia-specific immunoglobulin G (IgG) antibodies, and persistent infection. Compared to IOE-primed mice, subsequent lethal IOE challenge of E. muris-primed mice, resulted in (i) 100% protection against lethal infection, (ii) strong Ehrlichia-specific secondary gamma interferon (IFN-gamma)-producing effector/effector memory CD4+ and CD8+ T-cell responses, (iii) enhanced secondary anti-ehrlichial antibody response, (iv) accelerated bacterial clearance, and (v) the formation of granulomas in the liver and lung. E. muris-primed mice challenged with IOE had lower levels of serum interleukin-1alpha (IL-1alpha), IL-6, and IL-10 compared to unprimed mice challenged with IOE. Interestingly, the fatal secondary response in IOE-primed mice correlated with (i) decline in the Ehrlichia-specific CD4+ and CD8+ type 1 responses, (ii) marked hepatic apoptosis and necrosis, and (iii) substantial bacterial clearance, suggesting that fatal secondary response is due to immune-mediated tissue damage. In conclusion, protection against fatal ehrlichial infection correlates with strong expansion of IFN-gamma-producing CD4+ and CD8+ effector memory type 1 T cells, which appear to be maintained in the presence of IgG antibodies and persistent infection.     

Effects of milbemycin D on adult Angiostrongylus cantonensis in rats

Effects of milbemycin D against adult Angiostrongylus cantonensis in rats were examined. The first-stage larval counts in rat faeces (larvae per gram of faeces per female worm recovered, LPG/female) were most conspicuously reduced in the group treated with nine consecutive weekly doses of 5.0 mg/kg. The effect was more marked in the group treated with five or ten successive daily doses of 5.0 mg/kg than the group treated with a single dose of 25.0 or 5.0 mg/kg. Host lung-body weight ratio and number of recovered worms were reduced significantly only in the group treated with five or ten successive daily doses of 5.0 mg/kg. These results suggest that the action of milbemycin D on the reproductive system of the worms might be differentiated from its killing action. The in vitro motility of females recovered from rats medicated with nine consecutive weekly doses of 5.0 mg/kg was inhibited, and almost all females and males were semitransparent and colourless. Results obtained from sectioned worms showed little content in their digestive tracts and uteri. In addition, there were few eggs and first-stage larvae in the lung tissues of treated rats. These suggest that milbemycin D affects the reproductive functions of the worms through an indirect mode of action including paralysis and inhibition in food intake and energy and/or synthetic metabolism.Studies of chemotherapy of parasitic helminths XXIX     

Protective immunity towards intracellular pathogens

Immunity towards intracellular pathogens is often dependent upon the generation of CD8(+) memory T cells, which provide long-lasting and effective protection. Over the past few years, we have gained novel insights into the heterogeneity of CD8(+) T cells, time points of lineage commitment, and lineage relationships between subpopulations. These studies suggest that memory CD8(+) T cells progressively develop from na?ve cells early during the immune response and further differentiate unidirectionally into short-living effector cells. We have also learnt that different memory subsets play distinct roles in conferring protection: whereas effector memory T cells are able to provide immediate protection but are not necessarily maintained long-term, central memory T cells have the potential for constant self-renewal. Thus, neither subset really fulfills all criteria of memory. As protective effector memory cells can develop from central memory cells, vaccination strategies should focus on induction of a balanced ratio of the two memory T cell subsets.     

Pathogenesis and immunity in enterococcal infections

Enterococcus faecalis and Enterococcus faecium have emerged as multi-resistant nosocomial pathogens in immunocompromised and critically ill patients. Multi-resistant strains have acquired virulence genes resulting in hospital-adapted clones. The following review summarizes several proteins and carbohydrate- or glycoconjugates that have been identified as putative virulence factors involved in the pathogenesis of enterococcal infections and may be used as targets for alternative therapies. Several studies describing the host immune response against enterococci are also summarized.     

Protective immunity of pneumococcal glycoconjugates

Pneumococcal polysaccharides (PSs), designated as T-cell independent type 2 (TI-2) antigens, induce poor immune responses in young children. Splenic marginal zone B cells, associated with CD21, CD19 and C3d, play an important role in TI-2 antibody responses, and provide host defense against bacterial pathogens. Antibody response, avidity, and opsonophagocytic activity of antisera were examined in mice immunized with type 9V PS conjugated to inactivated pneulmolysin (Ply) or to autolysin (Aly). Compared to mice given 9V PS alone, serum IgG and IgM concentrations against the 9V PS were higher in mice immunized with conjugates. High concentrations of serum antibodies were maintained for over 12 weeks. The relative avidities of IgG and IgM antibodies and opsonophagocytic activity against 9V pneumococci were high in mice immunized with conjugates. Thus, conjugate vaccines can induce high as well as long duration of antibody response and effective functional activity. In another study, mice received intranasal immunization with type 9V conjugate or 9V PS. These animals produced 9V PS IgG and IgA antibodies in their serum, spleen, intestine, lung, Peyer's patch and fecal extract samples. Mice immunized with these glycoconjugates exhibited opsonophagocytic activity and rapid bacterial clearance from blood and provided homologous and cross-protection against challenge with virulent pneumococci. These results indicate that intranasal immunization with glycoconjugate vaccines may serve as an alternative and convenient approach for prevention of pneumococcal infection.     

Skin sensitizing antibody in experimental infections with Metastrongylus spp. (Nematoda)

Homologous passive cutaneous anaphylactic tests in guinea-pigs revealed the production of skin sensitizing antibody by Metastrongylus spp. infection. Skin sensitizing antibody was detected by immediate wheal and flare reaction in an infected pig. The pig skin sensitizing antibody failed to elicit a Prausnitz—Kustner (PK) reaction in an uninfected recipient pig, or heterologous passive cutaneous anaphylaxis in guinea-pigs.     

Protective immunity against Eimeria acervulina following in ovo immunization with a recombinant subunit vaccine and cytokine genes

A purified recombinant protein from Eimeria acervulina (3-1E) was used to vaccinate chickens in ovo against coccidiosis both alone and in combination with expression plasmids encoding the interleukin 1 (IL-1), IL-2, IL-6, IL-8, IL-15, IL-16, IL-17, IL-18, or gamma interferon (IFN-gamma) gene. When used alone, vaccination with 100 or 500 mug of 3-1E resulted in significantly decreased oocyst shedding compared with that in nonvaccinated chickens. Simultaneous vaccination of the 3-1E protein with the IL-1, -15, -16, or -17 gene induced higher serum antibody responses than 3-1E alone. To evaluate protective intestinal immunity, vaccinated birds were challenged with live E. acervulina oocysts 14 days posthatch, and fecal-oocyst shedding and body weight gain were determined as parameters of coccidiosis. Chickens vaccinated with 3-1E protein showed significantly lower oocyst shedding and normal body weight gain than nonvaccinated and infected controls. Simultaneous immunization with 3-1E and the IL-2, -15, -17, or -18 or IFN-gamma gene further reduced oocyst shedding compared with that achieved with 3-1E alone. These results provide the first evidence that in ovo vaccination with the recombinant 3-1E Eimeria protein induces protective intestinal immunity against coccidiosis, and this effect was enhanced by coadministration of genes encoding immunity-related cytokines.     

Cell mediated immunity in experimental rubella infections

Summary Antibody and cell-bound immune response were assessed in rabbits inoculated by the intravenous route with Cendehill or with wild rubella virus. Our results suggest that wild or attenuated live rubella virus induce a transient unresponsiveness of the lymphocytes to PHA stimulationin vitro and suggest also that this immunosuppression was due to the persistence of rubella virus in the lymphocytes.With 2 Figures     

Experimental Salmonella typhimurium infections in rats. III. Transfer of immunity with primed lymphocyte subpopulations

The protective effect of primed lymphocytes against a lethal dose of Salmonella typhimurium was studied in athymic and euthymic LEW rats. Primed lymphocytes were obtained by inoculating euthymic and thymus-grafted animals with a non-lethal dose of Salmonella typhimurium. Four weeks after the infection, spleen lymphocytes were separated by panning technique and antibody-coated magnetic microsphere separation using antibodies to pan T and pan B lymphocytes and subsequent sorting in a fluorescence activated cell sorter by means of monoclonal antibodies against CD4+ and CD8+ cells. Euthymic and athymic rats were injected with different doses of primed pan B, pan T, CD4+ and CD8+ T lymphocytes before inoculation with a lethal bacterial dose. Most of the animals treated with pan B, pan T or CD8+ cells died within two weeks. After treatment with primed CD4+ cells, only six of 39 animals died. Doses as low as 10(4) cells from both euthymic or thymus-grafted animals were effective, and athymic and euthymic recipients survived equally well. Four weeks after the infection both athymic and euthymic animals housed very few bacteria and had high antibacterial antibody titres. The percentages of splenic and lymph node CD4+ cells in the athymic rats were comparable to those found in the euthymic animals. The study shows that primed CD4+ lymphocytes even in very low doses are able to induce immunity against a Salmonella typhimurium infection.     

Digested Ara h 1 has sensitizing capacity in Brown Norway rats

Background Food allergies are a public health issue of growing concern, with peanuts in particular being associated with severe reactions. The peanut allergen, Ara h 1, belongs to the cupin plant food allergen family, which, unlike other structural families, appears to be broken down rapidly following gastrointestinal digestion.
Objective Using Ara h 1 as a model allergen, the ability of digested protein to sensitize has been investigated.
Methods Ara h 1 was purified from whole roasted peanuts. Intact Ara h 1 was digested in an in vitro model, simulating the human gastrointestinal digestion process. Digestion products were analysed for peptide sizes and their ability to aggregate. Brown Norway (BN) rats, used as an animal model, were immunized with purified intact Ara h 1 or the gastrointestinal digestion products thereof. The sensitizing capacity was evaluated by analyses of specific antibody (IgG1, IgG2a and IgE) responses and ability to trigger mediator release of rat basophilic leukaemia (RBL)-2H3 cells.
Results The present study showed that Ara h 1 was broken down, resulting in peptide fragments of sizes <2.0 kDa, of which approximately 50% was in aggregated complexes of M _r up to 20 kDa. Ara h 1 digesta were shown to have sensitizing capacity in BN rats, being capable of inducing specific IgG and IgE antibodies. The IgE response was functional, having the capacity to induce specific degranulation of RBL cells.
Conclusion From this study, it can be concluded that lability of a food allergen to gastrointestinal digestion does not necessarily abrogate its allergenic sensitizing potential.     

睾酮对未成熟雄性大鼠体液和细胞免疫力的影响

目的 以生理浓度的丙酸睾酮处理未成熟的雄性SD大鼠,探讨睾酮对免疫功能的影响。方法 用放射免疫法检测了睾酮和雌二醇水平;用流式细胞仪分析淋巴细胞总数及其亚类;用MTT法测定淋巴细胞转化能力;用酶联免疫吸附法测定白细胞介素6（IL-6）和IgG的水平。结果 睾酮一方面可以下调IL-6、IgG水平,降低淋巴细胞转化能力以及CD4/CD8比率,另一方面可上调抑制性T细胞数目。结论 睾酮对免疫系统起抑制作用,提示可以应用雄激素对免疫系统的调节作用来治疗某些免疫反应增高性疾病,如：某些自身免疫性疾病。