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PubMed1996

Trypanosoma cruzi: protective immunity in mice immunized with paraflagellar rod proteins is associated with a T-helper type 1 response.

We have examined the ability of mice to survive a lethal challenge with the parasitic hemoflagellate, Trypanosoma cruzi, following immunization with paraflagellar rod proteins (PAR) 1 and 2 either alone or in combination with the following adjuvants: Freund's, alum, QS-21, Ribi-700, or IL-12. PAR administered subcutaneously (sc) in combination with Freund's or alum provided significant protection, 100 and 83%, respectively, against a T. cruzi challenge. In contrast, PAR in combination with QS-21, Ribi-700, IL-12, or Freund's administered intraperitoneally (ip) or PAR alone provide no protection against a challenge. PAR-specific serum antibody titers and isotype profiles for several of the immunization regimens were determined, and no positive correlation could be seen between a protective immune response and either antibody titer or the subclass of antibody induced. We also examined the ability of PAR to stimulate T cells from the spleen and lymph nodes of mice immunized with PAR in combination with Freund's (sc), Freund's (ip), alum, or Ribi-700. Each of the adjuvants strongly enhanced the ability of enriched T cells to proliferate in a PAR-specific fashion, suggesting no obvious correlation between PAR-specific T cell activation and protection. However, examination of the cytokine profiles of the stimulated T cell groups showed that the protective groups differed from the nonprotective groups. While all four groups showed low levels of IL-10, the Freund's (sc) and alum groups had higher levels of IFN-gamma and IL-2 than Freund's (ip) and Ribi-700 groups, and most strikingly, no IL-4 could be detected in either the Freund's (sc) or the alum group, in contrast to significant levels of IL-4 in both the Freund's (ip) and the Ribi-700 group. These findings indicate that protective immunity in mice immunized with PAR is associated with a Th1-type response.

Adjuvants, Immunologic↗
PubMed1998

Innate immune recognition and control of adaptive immune responses.

The immune system of higher vertebrates consists of two components: innate and adaptive. The innate immune system relies on a set of germ-line encoded receptors that recognize conserved molecular patterns found only in microorganisms. The adaptive immune system uses somatically generated antigen receptors which are clonally distributed on the two types of lymphocytes: T cells and B cells. These antigen receptors are generated by random processes and, as a consequence, the general design of the adaptive immune system is based on clonal selection of lymphocytes expressing receptors with particular specificities. Here we discuss the essential role of the innate immune system in the clonal selection of lymphocytes and activation of the adaptive immune responses.

Animals↗
PubMed1979

Some perspectives on the transfer of cell-mediated immunity by immune-RNA.

Ribonucleic acid extracts of lymphoid cells from immune hosts were used to transfer in vivo and in vitro cell-mediated immune reactivity to a variety of antigens. The in vivo immune responses transferred by RNA included the delayed cutaneous hypersensitivity reaction to fungal and chemically-defined antigens and the tumor-rejection reaction to guinea pig hepatoma antigens. The in vitro immune responses transferred by RNA included macrophage migration inhibition by fungal, chemically-defined, and tumor antigens. The transfer activity of RNA preparations was contained in the 8 s to 18 s species of RNA and was sensitive to RNase but not to DNase or trypsin. Antigen was not detectable in the RNA preparations and appeared to have no role in the transfer activity. Syngeneic, allogeneic, or xenogeneic sources of RNA could transfer immune reactivity. In each system tested, the transfer of cell-mediated reactivity by RNA was specific for the antigen used to sensitize the RNA donor. The potential use of RNA-mediated transfer of immunity is discussed.

Animals↗
PubMed1982

Passive immunity in rats infected with Angiostrongylus cantonensis: interactions between syngeneic immune serum and sensitized lymph node cells.

Immune serum injected into the peritoneum of rats passively protected them against Angiostrongylus 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 against A. cantonensis in recipient rats.

Angiostrongylus↗
PubMed1996

The effect of immune sera from hamsters immunized with sandfly gut and whole body extract antigens on the fecundity and mortality of Phlebotomus duboscqi (Diptera: Psychodidae).

Phlebotomus duboscqi were fed on hamsters previously immunized with different concentrations of homogenized crude sandfly gut antigen and supernatant obtained from whole body extract. The humoral response in the rodents was quantified at different times post-immunization by the enzyme-linked immunosorbent assay. Sandflies were fed on either immunized or saline control hamsters and the effect of the blood meals on sandfly feeding, survival and fecundity was investigated. The humoral response in immunized hamsters as measured by the presence of P. duboscqi-specific IgG antibodies was significantly greater (P < 0.05) as compared to the controls. This difference was noted in sera collected on 15 and 25 days post-immunization. Sandflies fed on immunized hamsters had a significantly higher mortality (P < 0.05) and decreased egg production (P < 0.05) than those fed on unimmunized control hamsters.

Animals↗
PubMed1996

Induction of pneumococcal polysaccharide-specific mucosal immune responses by oral immunization.

Liposome and cholera toxin (CT) are considered to be effective antigen delivery vehicles and adjuvants for mucosal vaccines. The effect of these antigen delivery systems on adjuvant responses to mucosally administered pneumococcal polysaccharide (Pnup) was investigated in this study. Both mucosal (e.g. oral) and systemic (i.p.) immunization of mice with purified preparations of Pnup type 23F induced antigen-specific IgM responses in sera. Interestingly, oral immunization of as little as 10 micrograms of Pnup type 23F was sufficient to induce systemic IgM responses. Pnup-specific IgM antibodies peaked by day 7 and no booster responses were evident after a second dose on day 14. In order to examine whether IgG and IgA Pnup-specific immune responses are induced by mucosal immunization, the mucosal adjuvant CT was mixed with Pnup type 23 as an oral vaccine. Co-oral administration of CT and Pnup type 23F resulted in the induction of Pnup-specific faecal IgA antibodies. These results were confirmed by detecting antigen-specific IgA-spot-forming cells in mononuclear cell suspensions prepared from the intestine of immunized mice. These findings suggest that oral immunization with Pnup in the presence of mucosal adjuvants, such as CT, could induce Pnup-specific IgA responses whereas Pnup alone did not. In an attempt to further enhance antigen-specific antibody responses, Pnup type 23F was encapsulated in liposomes and used as mucosal vaccine. However, immunogenicity of Pnup was not improved.

Administration, Oral↗
PubMedDate not supplied

Genistein suppresses antigen-specific immune responses through competition with 17beta-estradiol for estrogen receptors in ovalbumin-immunized BALB/c mice.

OBJECTIVE: The aim of this study was to determine the effects of phytoestrogen genistein on antigen (Ag)-specific immune responses and elucidate the mechanisms underlying those effects. METHODS: Ovalbumin (OVA)-immunized BALB/c mice were administered genistein for 35 d, and OVA-specific immune responses were examined by measuring OVA-specific proliferative responses, production of cytokines, and antibody responses. To assess the effect of genistein on antibody responses to thymus-independent Ag, mice were immunized with 2,4,6-trinitrophenyl (TNP)-Ficoll instead of OVA. Effect of genistein on the functions of CD11c(+) dendritic cells was also examined. Finally, to determine the contribution of estrogen receptor to genistein-mediated immune regulation, mice that had been administered genistein were treated with the estrogen receptor antagonist ICI 182,780 and OVA-specific proliferative responses were examined. RESULTS: OVA-specific proliferative responses and interferon-gamma production levels were decreased in mice administered 20 mg/kg genistein compared with those in control mice without reduction in responses to anti-CD3 monoclonal (m)antibody. The level of OVA-specific immunoglobulin (Ig)G1 was also decreased in mice administered genistein. Levels of OVA-specific IgG2a and IgG2b production and interleukin-4 production in response to OVA were not significantly different but tended to decrease in genistein-treated mice. Genistein administration did not influence the TNP-specific IgM and IgG levels. Furthermore, genistein did not affect the Ag-presenting activity of CD11c(+) dendritic cells. Treatment with ICI 182,780 decreased OVA-specific proliferative responses, but genistein did not suppress these responses synergistically in mice treated with ICI 182,780. CONCLUSIONS: The results of this study suggest that genistein suppresses Ag-specific immune responses. The mechanism underlying the suppression is responsible for the competition of genistein with endogenous 17beta-estradiol for estrogen receptors.

Animals↗
PubMed2004

IL-12 enhances protective immunity in mice engendered by immunization with recombinant 14 kDa Schistosoma mansoni fatty acid-binding protein through an IFN-gamma and TNF-alpha dependent pathway.

Herein, we tested the ability of IL-12 to enhance protection induced by recombinant Sm14 (rSm14). Mice immunization with three doses of 25 microg of rSm14 was able to induce 25% of protection in mice against challenge. However, co-administration of exogenous IL-12 enhanced protective immunity engendered by rSm14 from 25 to 42.2%. Higher levels of IgG2a and TNF-alpha were observed in mice immunized with rSm14 plus IL-12 compared to animals vaccinated with rSm14 alone. Regarding other cytokines, significant amounts of IFN-gamma were measured in splenocyte culture supernatants of rSm14/IL-12 or rSm14 vaccinated mice and no IL-4 was detected. In an attempt to determine the role of IFN-gamma and TNF-alpha in IL-12 induced immunity, IFN-gamma and TNFR-p55 knockout mice were immunized with rSm14/IL-12 and no protection was achieved. Therefore, protection induced by rSm14/IL-12 was shown to be dependent on endogenous IFN-gamma and TNF-alpha. Although, rSm14 immunization induced partial protection, reduction of hepatic granuloma area was only observed when IL-12 was co-administered.

Adjuvants, Immunologic↗
PubMed2004

Efficacy of immune sera from human immunoglobulin transgenic mice immunized with a peptide mimotope of Cryptococcus neoformans glucuronoxylomannan.

The efficacy of antibody mediated immunity against Cryptococcus neoformans has not been established experimentally for human antibodies. Our group has previously shown that immunization with a conjugate consisting of a peptide mimotope of the C. neoformans capsular polysaccharide glucuronoxylomannan (GXM), P13, and diphtheria toxoid (P13-DT) prolonged survival of transgenic mice with human immunoglobulin loci, XenoMouse mice, which were challenged with a lethal dose of C. neoformans. In the study reported herein, we determined the efficacy of human antibodies in the sera of immunized XenoMouse mice against C. neoformans in passive transfer experiments in naïve BALB/c mice. Survival studies were performed with sera from XenoMouse mice expressing human IgG2/kappa (G2/k mice) or IgG4/kappa (G4/k mice) that had been immunized with P13-tetanus toxoid (TT)/Alhydrogel with or without CpG, and G2/k mice that had been immunized with P13-DT/Alhydrogel/CpG or Alhydrogel/CpG, obtained on day 7 (early sera) and days 30 or 35-59 (late sera) after primary immunization. Compared to mice receiving sera from G2/k-PBS-treated mice, the survival of naïve mice was prolonged by both early and late sera from G2/k-P13-DT/Alhydrogel/CpG-immunized mice, but only late sera from G2/k-P13-TT/Alhydrogel/CpG-immunized mice. Late, but not early sera from G2/k-Alhydrogel/CpG-immunized mice also prolonged survival. For all sera, prolongation of survival was associated with GXM-specific serum IgM. Sera from G2/k mice that received P13-TT without CpG, and all groups of G4/k mice had low to undetectable levels of antibody to GXM and were not protective. Our findings suggest that GXM-specific human IgM may be a functional mediator of protection against C. neoformans.

Adjuvants, Immunologic↗
PubMed1997

Cellular and humoral immune response to hepatitis B virus structural proteins in mice after DNA-based immunization.

BACKGROUND & AIMS: Development of a broad-based cellular immune response to hepatitis B viral structural proteins may be important for recovery from infection, and lack of such responses may lead to persistent viral infection and chronic liver disease. Strategies designed to enhance the hepatitis B virus (HBV)-specific immune response may be able to reduce persistent viral infection of the liver. The aim of this study was to induce HBV-specific cellular and humoral immune responses in mice using DNA-based immunizations with the large and middle envelope and nucleocapsid proteins. METHODS: Antibodies to HBV structural proteins, T-helper-cell proliferation, and cytokine release and generation of cytotoxic T lymphocyte (CTL) activity were measured in vaccinated mice. RESULTS: Immunized mice developed high-titer antibodies against envelope and core proteins in serum. More importantly, 93% of the immunized mice produced strong inflammatory CD4+ T-cell and CD8+ CTL responses to viral proteins. CONCLUSIONS: This study shows that DNA-based vaccination will generate broad-based CTL activity as well as strong T-helper cell responses with the production of TH1-type cytokines to HBV structural proteins. Such constructs are promising candidates as antiviral agents, and these studies have defined some of the most immunogenic antigens for an immunotherapeutic approach of chronic HBV infection.

Animals↗
PubMed2003

Immune responses against Abeta1-42 in HLA class II transgenic mice: implications for Abeta1-42 immune-mediated therapies.

We have investigated whether polymorphic differences in the major histocompatibility complex (MHC) class II molecules influence humoral and cellular immune responses against Abeta1-42. To analyze the effects of mouse MHC class II and tolerance effects of overexpression of human APP in mice, we immunized Tg2576 and non-transgenic littermates bred into two different MHC backgrounds with Abeta1-42 and compared both B and T cell responses. We found that in the presence of the mouse C57BL/6 background, both B and T cell responses against Abeta1-42 were significantly suppressed. To directly test the contribution of human MHC class II, we immunized various human HLA class II transgenic (TG) mice with Abeta1-42 and analyzed anti-Abeta immune responses. HLA-DR3 and HLA-DQ8 TG mice generated modest B and T cell responses against Abeta1-42. The presence of HLA-DR3/DQ8 in double TG mice enhanced the overall immune response against Abeta1-42. In contrast, HLA-DR4 TG mice mounted strong T cell responses but failed to generate high titer antibody responses against Abeta1-42, whereas, the HLA-DQ6 TG mice were not able to mount significant B or T cell responses against Abeta1-42. These studies in mice suggest that the presence of certain MHC class II molecules or combinations of class II molecules can potentially influence the overall immune response against Abeta1-42.

Amyloid beta-Peptides↗
PubMed1995

Higher levels of passive compared with active immunity in rats immunized with larval antigens of Schistosoma mansoni.

We have previously shown that it is the lung stage schistosomulum which is both the inducer and the target of immunity in rats vaccinated with irradiated cercariae but that rats can also be partially protected by immunization with detergent extracts of mechanically-transformed schistosomula. In the present study we therefore compared the immunogenicity of these and intermediate schistosomular stages. In the first experiment low levels of protection (13-24%) were induced by extracts of mechanically-transformed schistosomula cultured for 3 hours or 2 days but not by extracts of lung schistosomula. In a repeat experiment insignificant levels of protection were induced by extracts of 3 h schistosomula and lung schistosomula were again non-protective. Nevertheless, high levels of anti-schistosomula antibodies were demonstrated and sera from actively immunized rats conferred significant passive protection in five out of six trials. The levels of protection conferred by passive immunization (26-51%) were in each case higher than the levels of protection demonstrated in the respective serum donor groups, showing that some form of immunological blockade suppression is operating to prevent expression of protective immunity in the actively immunized rats.

Animals↗
PubMed1985

Comparison of immune responses between high and low responder strains of mice in the concomitant immunity and vaccine models of resistance to Schistosoma mansoni.

Mice of the inbred P strain fail to develop significant resistance to challenge Schistosoma mansoni infection at 6 weeks after either low-grade primary infection or vaccination with attenuated homologous parasites, in contrast to other strains such as C57Bl/6, and thus provide a model for comparison of potential immune resistance mechanisms in low versus high responder animals. In this study, the antigen-specific cellular responses found to correlate with resistance in these strains were delayed cutaneous hypersensitivity, production of macrophage activating lymphokine and macrophage larvicidal activity, all of which were greater in infected or vaccinated C57Bl/6 mice than in similarly immunized but non-resistant P mice. Humoral responses correlating with resistance were IgM reactivity to schistosomula surface antigens in both infected and vaccinated animals, as well as both IgM and IgG reactivity to soluble schistosome antigens in infected mice. Immune responses that showed no relationship with resistance included IgG reactivity to larval surface antigens and immediate hypersensitivity to soluble worm antigens. In infected mice, neither granuloma size nor extent of hepatic fibrosis correlated positively with resistance to challenge infection. Thus, similarities exist between patterns of resistance and immune response at this early time after immunization with either viable or attenuated parasites. These observations suggest that common immune effector mechanisms could be involved, with activated macrophages playing a central role in resistance.

Animals↗
PubMed2000

Cellular and humoral immune response of European sea bass (Dicentrarchus labrax L.) (Teleostei: Serranidae) immunized with Sphaerospora dicentrarchi (Myxosporea: Bivalvulida).

The immune response of European sea bass after intracaelomic immunization with Sphaerospora dicentrarchi was studied. Fish were injected with S. dicentrarchi spores (DIC), with spores plus adjuvant (DIC + FCA), with adjuvant alone (FCA) or with PBS. Several parameters of the immune response were measured. Serum lysozyme increased significantly in DIC fish 1 week after immunization (p.i.) and it remained significantly higher in DIC + FCA fish 4 weeks p.i., and in DIC fish 8 weeks p.i. than in PBS-injected fish. The number of nitroblue tetrazolium-positive blood cells was significantly higher in DIC + FCA fish 1, 4 and 8 weeks p.i, but the highest values were detected 1 week p.i. The highest stimulation index was detected in phagocytes from DIC + FCA fish. The number of S. dicentrarchi antibody-secreting cells was significantly higher in DIC + FCA fish than in DIC fish. Serum from DIC and DIC + FCA fish, stained the polar capsules and the valves of S. dicentrarchi spores in immunohistochemistry. Serum antibodies could not be detected using immunoblot assay. All these results show that immunization with S. dicentrarchi resulted in the activation of the non-specific immune response, mainly 7 days p.i. A specific humoral response against the parasite was also demonstrated but it had a low magnitude.

Animals↗
PubMed1999

Co-immunization with DNA vaccines expressing granulocyte-macrophage colony-stimulating factor and mycobacterial secreted proteins enhances T-cell immunity, but not protective efficacy against Mycobacterium tuberculosis.

The development of more effective antituberculosis vaccines would assist in the control of the global problem of infection with Mycobacterium tuberculosis. One recent vaccination strategy is immunization with DNA plasmids encoding individual microbial genes. Using the genes for the M. tuberculosis-secreted proteins, MPT64 (23 000 MW) and Ag85B (30 000 MW) as candidate antigens, we previously prepared DNA vaccines and demonstrated their ability to stimulate T-cell responses and confer protection in a mouse model of aerosol tuberculosis (TB). The protective efficacy of the DNA vaccines was less than that promoted by the current vaccine Mycobacterium bovis bacille Calmette-Guèrin (BCG). To improve the immunogenicity and protective efficacy of these mycobacterial vectors, co-immunization of a plasmid expressing granulocyte-macrophage colony-stimulating factor (GM-CSF) was investigated. Intramuscular immunization with DNA expressing MPT64 or Ag85B and GM-CSF enhanced the antigen-specific cellular immune response, with increased proliferative response and production of interferon-gamma (IFN-gamma). The titre of antimycobacterial protein immunoglobulin G (IgG) antibodies was unchanged. Mice immunized with DNA vaccines showed reduced pulmonary bacterial load following an aerosol challenge of M. tuberculosis, but codelivery of the plasmid expressing GM-CSF did not increase the protective effect. Therefore, despite modifying the cellular immune response to DNA vaccines, GM-CSF does not improve their protective efficacy at the peak of infection after an aerosol challenge with 100 c.f.u. of M. tuberculosis.

Animals↗
PubMed1999

Nasal immunization of mice with Cryptosporidium parvum DNA induces systemic and intestinal immune responses.

DNA immunization offers a novel approach to inducing humoral and cellular immunity against infectious pathogens. We examined whether such an approach could be used against cryptosporiodiosis, an intestinal disease caused by the protozoan parasite Cryptosporidium parvum. This infection is a major problem for young ruminants and immunosuppressed individuals in whom cryptosporidiosis causes life-threatening symptoms. The life cycle of C. parvum takes place in the enterocytes of the intestinal epithelium. We therefore focused our attention on a route of immunization that might induce a mucosal immunoglobulin (Ig)A response. Eight-week-old BALB/c mice were immunized intranasally with DNA encoding a 15-kDa C. parvum sporozoite antigen (CP15-DNA) cloned onto the plasmid pcDNA3. CP15-DNA-immunized mice developed specific and longlasting production of anti-CP15 Ig A in intestinal secretions and specific IgG in sera 3 months and 1 year after the first DNA inoculation. CP15-DNA-immunized mice also developed an antigen-specific T lymphocyte proliferative response in both spleen and mesenteric lymph nodes. Control mice that received the pcDNA3 plasmid alone did not develop specific humoral and cellular responses. These results indicate that plasmid DNA may provide a powerful means of eliciting intestinal humoral and cellular responses to C. parvum infections in mammals.

Administration, Intranasal↗
PubMed1998

Skin delivery of a hybrid liposome/ISCOM vaccine implicates a role for adjuvants in rapid modulation of inflammatory cells involved in innate immunity before the enhancement of adaptive immune responses.

There is now compelling evidence that intradermal vaccination with an efficacious adjuvanted antigen triggers a series of coordinated responses characterized initially by the rapid mobilization and recruitment of granulocytes to the lung. Activation of effector cells of the innate immune system is intended to provide surveillance and temporary protective cover at vulnerable mucosal sites while both T and B cell precursors, as well as haematopoietic progenitor cells, are undergoing dramatic reductions in numbers during the first 2-4 days post-vaccination. Some of these events recapitulate those seen after infection with a pathogen. Initial decreases in cell numbers in the thymus and bone marrow (BM) are followed by rapid increases in cellular proliferation in these organs, probably in response to peripheral signals. Vaccine-induced cell death (by apoptosis) in the thymus may provide one of many stimuli needed to up-regulate BM production of progenitor cells, and cells of the B, myeloid and monocytic lineages so that depleted peripheral compartments are replenished. Reconstitution of the latter cell population is critical in ensuring sufficient numbers of APC are generated to deal with extraneous antigen resulting from either vaccination or proliferation of a pathogen. Ultimately, these APC, as effector cells of the innate immune system, must provide pattern recognition of dangerous pathogens and serve to activate appropriate T cell responses. Vaccination not only educates both the innate and adaptive arms of the immune response but also more interestingly, appears to regulate subsequent innate immune responses following exposure to a lethal challenge dose of bacteria. Under these conditions, the rate of loss of BM precursors is greatly attenuated in mice previously vaccinated with adjuvanted antigen compared to unvaccinated controls or mice that had received only antigen. Mice intradermally vaccinated with adjuvanted antigen also displayed increased rates of granulocyte and monocyte recruitment in the lung and spleen. These events occurred very rapidly within 12-36 h of challenge and may be crucial in providing complete protection in vaccinated mice against a challenge dose that was otherwise lethal for unvaccinated controls. Therefore, an important characteristic of an efficacious intradermal vaccine may be the ability to deplete T and B precursors in the thymus and BM lymphoid compartments followed by increased rates of haematopoiesis to re-supply peripheral requirements for granulocytes/monocytes, and T and B cells. Adaptive immunity elicited by intradermal vaccination is, therefore, dependent upon prior activation of the innate immune system.

Adjuvants, Immunologic↗
PubMed1987

Specific cellular immune response and neutralizing antibodies in goats immunized with native or recombinant envelope proteins derived from human T-lymphotropic virus type IIIB and in human immunodeficiency virus-infected men.

Animals immunized with native or recombinant envelope proteins from the human immunodeficiency virus (HIV, formerly referred to as human T-lymphotropic virus type III) human T-lymphotropic virus type IIIB and naturally HIV-infected men were assessed for neutralizing antibodies and cell-mediated immunity toward the virus. Immunization of rabbits or goats with the native external envelope glycoprotein gp120 or with corresponding recombinant proteins elicited strictly type-specific neutralizing antibodies. A broad, group-specific cellular immune response to gp120 and to three different HIV isolates was seen in goats immunized with the native gp120 but not in animals immunized with the nonglycosylated recombinant envelope proteins. In HIV-infected people, no T-cell response was seen, even though their T-cell response toward other foreign antigens was intact. The results show type- and group-specific epitopes on gp120, some of which may be of importance for the development of a vaccine against HIV infection.

Acquired Immunodeficiency Syndrome↗