Vaccination against murine cutaneous leishmaniasis by using Leishmania major antigen/liposomes. Optimization and assessment of the requirement for intravenous immunization

Efficacy of vaccination against cutaneous leishmaniasis in highly susceptible BALB/c mice was assessed comparatively by using radiation-attenuated promastigotes and colloidal Ag mixtures generated from a mixed Leishmania major (LV39) isolate (SLV39) and from a virulent cloned line (SVJ2) derived from the Jericho 2 L. major isolate. Dehydration-rehydration vesicle (DRV) liposomes were used as adjuvants. In optimization experiments phospholipid composition of DRV was varied, and the distearoyl derivative (DSPC) (liquid-crystalline phase transition temperature (Tc) 54 degrees C) of egg lecithin L-alpha-phosphatidylcholine was found to be superior to the dipalmitoyl derivative (DPPC, Tc 41.5 degrees C) and underivatized L-alpha-phosphatidylcholine (Tc -10 degrees C). The criteria studied were in vivo priming for a secondary in vitro proliferative response and the prepatency of lesion onset after L. major challenge of mice immunized once i.v. A single s.c. immunization with SLV39 either free or entrapped within DSPC liposomes primed spleen cells to produce significant levels of IL-3 when stimulated with SLV39 in vitro. In contrast, the i.v. route of immunization with the same Ag preparations led to little or no IL-3 production by the spleen cells. Despite development of significant T cell activation, both SLV39 and SVJ2 administered s.c., either free or entrapped within liposomes, were not protective. However, i.v. immunization four times with SVJ2 entrapped within DSPC liposomes induced a level of resistance comparable with that of 2 x 10(7) gamma-irradiated promastigotes in the stringent BALB/c L. major model. Although significant, protection conferred after i.v. immunization with SLV39/DSPC liposomes was less effective. These data therefore show that DSPC/DRV liposomes, although a good adjuvant for inducing protective immunity to cutaneous leishmaniasis, are not able to overcome the requirement for an i.v. route of immunization with the leishmanial Ag preparation. Additionally, they demonstrate a correlation between IL-3 secretion and non-protection. They also suggest that SVJ2 represents a better source of protective Ag than SLV39.     

Induction of protective immunity against Schistosoma mansoni by a nonliving vaccine. III. Correlation of resistance with induction of activated larvacidal macrophages

Mice protected against Schistosoma mansoni infection by intradermal (i.d.) immunization with nonliving larval or adult worm antigens plus bacterial adjuvant developed 24-hr skin test responsiveness to schistosome antigens with the histologic features of delayed hypersensitivity. Intraperitoneal antigen injection elicited a mononuclear cell-enriched exudative population containing macrophages activated for direct cytotoxicity against schistosomula and tumor cell targets. This was likely to be due to in vivo exposure to macrophage-activating lymphokines, since these cells were unresponsive to further lymphokine stimulation in vitro and splenocytes from immunized mice reacted to specific in vitro antigen challenge by production of lymphokines capable of conferring larvacidal activity upon control macrophages. In contrast, mice treated with schistosome antigens by i.v. injection, which were not protected against challenge infection, failed to develop delayed hypersensitivity or activated macrophages in response to specific antigen challenge in vivo, and the titers of macrophage-activating lymphokine produced by in vitro antigen-stimulated splenocytes from these mice were threefold to fourfold lower than those produced by cells from animals immunized by the i.d. route. Thus, sensitization for cell-mediated immune responses including lymphokine production and macrophage activation correlated with induction of resistance to S. mansoni in this model of vaccination.     

Prophylactic immunization against experimental leishmaniasis. V. Mechanism of the anti-protective blocking effect induced by subcutaneous immunization against Leishmania major infection

The responsiveness of BALB/c mice to protective i.v. immunization with 150,000-rad irradiated or heat-killed Leishmania major promastigotes can be totally suppressed by prior subcutaneous (s.c.) injection of the same "vaccine." Induction of this effect is leishmania specific for although prevention of protection against L. major infection can be obtained with either homologous or Leishmania donovani promastigotes, it does not follow s.c. administration of an immunogenic Trypanosoma cruzi epimastigote preparation. Multiple s.c. injections of irradiated L. major promastigotes do not inhibit the subsequent antibody response of any major isotype to i.v. immunization, but rather induce some priming. The same s.c. injections induced delayed-type hypersensitivity (DTH) reactivity that could be transferred locally or systemically, although it was weaker than in mice with cured infections. Parallel cell-mediated immunity (CMI) responses were also reflected in vitro in specific lymphocyte transformation assays. Despite this evidence of a DTH/helper type of T cell response, transfer of 5 X 10(7) viable T cell-enriched spleen cells from 4 X s.c. immunized donors to normal recipients completely abrogated the protective response to i.v. immunization. Conversely, T cell-depleted (anti-Thy-1.2 + C treated) cells were without effect. The inhibitory T cells were defined by monoclonal antibody pretreatment as possessing an Lyt-1+2-,L3T4+ phenotype. T cells from s.c. immunized donors were also shown, by mixed transfer experiments, to counteract completely the protective effect of T cells from i.v. immunized donors in 550-rad irradiated recipients. They were as potent as suppressor T cells from donors with progressive disease both in this capacity and in abrogating the prophylactic effect of sublethal irradiation itself. The similarities and differences between suppressor and immune effector T cells induced by s.c. or i.v. immunization and those arising in response to leishmanial infection itself are discussed.     

Vaccination against cutaneous leishmaniasis in a murine model. II. Immunologic properties of protective and nonprotective subfractions of soluble promastigote extract

We have previously demonstrated that BALB/c mice can be protected against a fatal infection with Leishmania major by i.p. immunization with a soluble leishmanial antigen (SLA) preparation in conjunction with the adjuvant, Corynebacterium parvum (CP). In this study, SLA was separated into nine distinct fractions by anion exchange liquid chromatography, and the fractions were analyzed for their ability to stimulate T cells obtained from immunized mice, to be recognized by vaccine-induced antibodies, and to induce protective immunity. While all but one of the fractions were recognized by antibodies from SLA + CP immunized mice, only two fractions (fractions 1 and 9) stimulated lymphocytes to produce macrophage-activating factor and elicited significant delayed-type hypersensitivity in vivo. When mice were immunized with the fractions, only fraction 9 stimulated significant immunity (76% protection in seven experiments). Proteins (accounting for 1.3% of the total in SLA) appear to be responsible for the protection elicited with fraction 9, since protease treatment of this fraction destroyed its immunogenicity. Thus, a partially purified protective protein antigen fraction has been obtained and protection with this fraction correlated with cell-mediated immune responses. However, these results also demonstrate that the ability of leishmanial antigens to be recognized by T cells and produce macrophage-activating factor does not in itself predict whether such molecules will induce immunity, suggesting that protective leishmanial antigens may have additional unique properties.     

Evaluation of immune response to bovine rotavirus following oral and intraperitoneal inoculation in mice

With a view to use mice as an experimental model for studying immune response to bovine rotavirus (BRV), the kinetics of humoral and cellular immune responses to BRV in mice were evaluated by immunizing through intraperitoneal and oral route with UK strain of BRV. Following immunization with BRV, anti-rotavirus antibodies was developed in mice. The mean log antibody titres as measured by ELISA in mice immunized by intraperitoneal route were significantly higher than those immunized by oral route. Significant cellular immune response was observed in BRV-immunized mice on stimulation with BRV antigen, as measured by lymphocyte proliferation assay. The thymidine uptake by splenic and mesenteric lymph-node cells of intraperitoneally immunized mice on stimulation with BRV was 21328 +/- 1225 and 739 +/- 55 CPM, respectively. The splenic cells showed significantly higher stimulation (stimulation index 12.98) as compared to those of mesenteric cells (stimulation index 1.57). Foot pad inoculation test showed maximum virus-specific delayed type hypersensitivity reaction at 24 hr post-challenge following primary immunization and at 18 hr post-challenge following secondary immunization. The results indicate that BRV immunization by intraperitoneal route generates more efficient immune response in mice than by oral route and this route may be used for immune response studies involving BRV infection.     

IFN-gamma modulates the early development of Th1 and Th2 responses in a murine model of cutaneous leishmaniasis.

Resistance to Leishmania major in mice is associated with the generation of distinct CD4+ Th subsets, termed TH1 and TH2. To define the factors contributing to the genesis of these Th cells, we first investigated when these subsets developed following L. major infection. Lymph node (LN) cells collected 3 days after infection of BALB/c mice secreted IL-4 and IL-5 in vitro, but little IFN-gamma, whereas LN cells from a resistant strain, C3H/HeN, secreted IFN-gamma and no IL-4 or IL-5. Cytokine production was eliminated in both cases by in vivo or in vitro depletion of CD4+ cells, but not after depletion of CD8+ cells. Similar responses were observed after inoculation of killed promastigotes or a soluble leishmanial Ag preparation. These data indicate that the development of Th1- and Th2-like responses can precede lesion formation and does not require a live infection. We next investigated whether IFN-gamma was important in the differentiation of Th1 and Th2 cells. C3H/HeN mice have previously been shown to be susceptible to leishmanial infection after treatment with anti-IFN-gamma. We confirmed this observation and found that the abrogation of resistance was associated with enhanced production of IL-4 and IL-5, and decreased production of IFN-gamma by cells taken from these mice. Conversely, LN cells from BALB/c mice inoculated with parasites plus IFN-gamma produced significantly higher levels of IFN-gamma, and decreased levels of IL-4 and IL-5, than mice infected with parasites alone. Finally, we determined if IFN-gamma might augment vaccine induced immunity. We found that s.c. immunization with soluble leishmanial Ag, the bacterial adjuvant, Corynebacterium parvum and IFN-gamma could protect mice against L. major infection, and that this protection was associated with induction of Th1 responses. From these data we conclude that levels of IFN-gamma at the time of infection or immunization dramatically alters the type of response elicited: high levels of IFN-gamma favor Th1 type responses, whereas low levels promote a Th2 response.     

Protection against Leishmania major infection by oligomannose-coated liposomes

Liposomes coated with neoglycolipids constructed with mannopentaose and dipalmitoylphosphatidylethanolamine (Man5-DPPE) have been shown to induce cellular immunity against antigens encapsulated in the liposomes. To assess whether these neoglycolipid-coated liposomes can elicit protective immune response against challenge infection, effects of immunization with soluble leishmanial antigens encapsulated in the liposomes were evaluated using Leishmania major infection in susceptible BALB/c mice. Intraperitoneal immunization of mice with leishmanial antigens in the Man5-DPPE-coated liposomes significantly suppressed footpad swelling in comparison to the control, non-immunized mice, while progression of the disease was observed in mice administered antigens in uncoated liposomes and those administered soluble antigens alone, as seen with control mice. Similarly, the number of parasites decreased substantially in local lymph nodes of mice immunized with the antigen in the Man5-DPPE-coated liposomes. Protection against L. major infection in the immunized mice also coincided with an elevated ratio of antigen-specific IgG2a/IgG1 antibodies, which is a profile of T helper-type 1-like immune response. Taken together, these results indicate the possibility that Man5-DPPE-coated liposome-encapsulated antigens could serve as a vaccine that triggers protection against infectious disease.     

Prophylactic immunization against experimental leishmaniasis. VI. Comparison of protective and disease-promoting T cells

In previous studies, we reported that mice immunized i.v. with lethally irradiated Leishmania major promastigotes developed substantial resistance to a subsequent L. major infection. However, such protection could be totally suppressed by prior s.c. injection with the same antigens. Both the protective immunity and the inhibition of its induction could be adoptively transferred with specific Lyt-2- T cells. Here, we present evidence showing that protection and disease promotion resulting from i.v. or s.c. immunization, respectively, are mediated by functionally distinct subsets of T cells. In a series of titration experiments, it was found that freshly isolated T cells derived from prophylactically i.v. immunized BALB/c mice were either protective (greater than 10(7) cells/recipient) or ineffective (less than 10(7) cells/recipient). No exacerbation of disease was observed at any dose. Conversely, T cells from mice immunized s.c. either accelerated disease development and inhibited protective immunization (greater than 10(7) cells/recipient) or had no effect (less than 10(7) cells/recipient). No protection was observed at any dose tested. In mixed transfer experiments, increasing numbers of T cells from s.c. immunized donors progressively inhibited the protective effect of T cells from i.v. immunized donors. Supernatant of T cell cultures from protectively immunized donors contained substantial macrophage-activating factor whereas such activity was not detectable in the supernatant of T cell culture from s.c. immunized donors. Analysis by flow cytometry showed that the spleen and lymph nodes of normal, i.v., or s.c. immunized BALB/c mice contained similar ratios of L3T4+ cells and Lyt-2+ cells.     

Route-related variation in the immunogenicity of killed Salmonella enteritidis vaccine: role of antigen presenting cells

In order to assess the role of the route of immunization on the immunogenicity of killed Salmonella vaccine, mice were immunized with killed S. enteritidis by intraperitoneal (i.p.) and intradermal (i.d.) routes. Whereas the former was non-immunogenic, the i.d. immunization generated an excellent delayed-type hypersensitivity response; further, i.p. immunization could even suppress the subsequent i.d. immunization. Since the peritoneal macrophages (MO) are known to be particularly low in Ia or MHC-class II antigens, so essential for antigen presentation, the non-immunogenicity by i.p. route was thought to be due to their poor presentation efficiency. Poly I: poly C, an interferon inducer, is known to enhance the MHC-class II expression; hence effect of poly I: poly C treatment on the immunogenicity of the killed vaccine by i.p. route was tested and indeed the non-immunogenicity was corrected. Poor efficiency of presentation of S. enteritidis antigen by peritoneal cells and its improvement by prior poly I: poly C treatment was further confirmed by in vitro lymphocyte transformation test using primed T cells and peritoneal cells from normal and poly I: poly C treated mice. Poly I: poly C treatment also enhanced expression of Ia antigens on peritoneal cells.     

Different T helper cell subsets elicited in mice utilizing two different adjuvant vehicles: the role of endogenous interleukin 1 in proliferative responses

Mice were immunized with either poly(Glu, Arg, Ala) or poly(Glu, Lys, Phe) contained in two different adjuvant preparations, alum (A1K(SO4)2) or complete Freund's adjuvant (CFA), and in vitro antigen-driven proliferative responses of lymph node cells were assayed 4-16 days later. After immunization with antigens on alum, endogenous interleukin 1 (IL-1) as well as interleukin 4 (IL-4) production was required for the proliferation of the elicited T cells as inclusion of either polyclonal goat anti-mouse IL-1 alpha or monoclonal anti-mouse IL-4 (11B11) in the cultures inhibited proliferative responses to antigen. In contrast, proliferative responses of cells elicited by antigen in CFA were not inhibited by either anti-IL-1 or anti-IL-4. Monoclonal antimouse CD4 (GK 1.5) inhibited proliferative responses regardless of which adjuvant was used to elicit antigen-reactive cells. These data indicated that phenotypically different subpopulations of CD4+ cells were elicited by the same antigen administered in different adjuvant preparations, Th2-like cells after immunization with polymers on alum and Th1-like cells after immunization with antigens in CFA. An examination of the isotypes of polymer-specific antibodies present in the sera of immunized mice also supported this conclusion.     

人IL-12与结核分枝杆菌抗原ESAT-6联合基因疫苗的免疫效果观察

人白细胞介素12(IL-12)与结核分枝杆菌免疫优势抗原ESAT-6真核表达质粒联合基因免疫,诱导免疫应答效果观察。近交系BALB/c小鼠,随机分组:A组(生理盐水对照)、B组(pcDNA3.1空质粒对照)、C组(BCG对照)、D组(pcESAT-6)和E组(pcIL-12 pcESAT-6)。B、D、E质粒免疫组小鼠分别于胫前肌肌肉注射布比卡因(7.5g/L)和质粒的混和物(1∶4,100μL,含质粒70μg/次),A组小鼠肌肉注射生理盐水和布比卡因的混和物(1∶4,100μL),均间隔2周免疫一次,共免疫3次;末次免疫时,C组小鼠皮下注射BCG菌液,0.3mL/只,含106CFU/mL。末次免疫后14d和28d,各组小鼠分别取血分离血清用于总IgG测定,同时分离脾细胞,经TB-PPD刺激后检测脾细胞增殖(XTT比色法)活性和脾细胞培养上清液中γ干扰素(IFN-γ)、白介素4(IL-4)分泌水平。pcESAT-6质粒DNA单独免疫(D组)或与pcIL-12质粒DNA联合免疫(E组),均能诱导小鼠产生特异性抗体,且抗体水平在末次加强免疫后14~28d逐渐增加;但pcIL-12与pcESAT-6联合免疫后,特异性抗体水平较pcESAT-6单独免疫增加不明显(P<0.05)。C、D、E组免疫小鼠脾细胞体外经TB-PPD刺激后,E组小鼠特异性淋巴细胞增殖活性和IFN-γ分泌水平明显强于C组和D组(P<0.05),而IL-4分泌水平相互间未发现明显差异。末次加强免疫后14~28d,E组小鼠脾细胞增殖活性维持在较高水平,而C组小鼠脾细胞增殖活性先低后高,D组则先高后低;IFN-γ诱生水平,E组最高,C组次之,D组最低。pcIL-12与pcESAT-6质粒DNA联合免疫后能刺激机体产生强烈的细胞免疫和稳定的体液免疫,在动物体内诱发的细胞免疫较ESAT-6或BCG单独免疫时均有明显增加并维持较长时间,此外联合免疫后诱导的体液免疫也较BCG免疫有明显增加。     

Leishmania donovani recombinant iron superoxide dismutase B1 protein in the presence of TLR-based adjuvants induces partial protection of BALB/c mice against Leishmania major infection

In this study, we tested the protective efficacy of recombinant Leishmania donovani iron superoxide dismutase B1 (SODB1) against Leishmania major infection in BALB/c mice. Mice were challenged with L. major 3weeks after the second boost immunization with rSODB1 alone or in the presence of adjuvants. Injection of BALB/c mice with rSODB1 alone elicited both humoral and cellular immune responses. Administration of rSODB1 with CpG ODN or GLA-SE (a synthetic toll-like receptor 4 agonist) adjuvant resulted in the induction of anti-SODB1 IgG1, and more importantly of significantly high levels of IgG2a isotype. Immunization of mice with rSODB1 alone or with adjuvant induced the production of IFN-γ by splenocytes in response to stimulation with L. major soluble leishmanial antigens (SLA). Moreover, immunization protocols involving rSODB1 resulted in a significant decrease in IL-10 as compared to controls. The presence of CpG ODN or GLA-SE adjuvant in the immunization protocols resulted in a relative increase in IFN-γ in response to stimulation with rSODB1 in comparison to immunization with rSODB1 alone. Mice immunized with rSODB1 plus CpG ODN or GLA-SE, were able to partially control their Leishmania infections, as indicated by the reduction in footpad swelling and parasite numbers, compared to controls. These results suggest that immunization with recombinant SODB1 protein together with CpG ODN or GLA-SE can be potential vaccine candidate against leishmaniasis.     

Exacerbation of murine cutaneous leishmaniasis by adoptive transfer of parasite-specific helper T cell populations capable of mediating Leishmania major-specific delayed-type hypersensitivity

The effect of adoptive transfer of in vitro-propagated Leishmania major-specific T cell populations on the course of experimentally induced cutaneous leishmaniasis was studied in mice. The L. major-specific T cells expressed the T helper/inducer phenotype and were able in vitro to a) mount a specific proliferative response, b) provide specific helper activity for antibody responses, c) activate parasitized macrophages resulting in L. major destruction, and d) secrete macrophage-activating factors as tested in a tumoricidal assay. These T cells were also found capable of transferring parasite-specific delayed-type hypersensitivity responses to normal syngeneic mice. Results indicated that the i.v. transfer of these L. major-specific T cell populations into normal syngeneic mice exacerbated cutaneous lesions induced by infection with L. major. This effect on the disease process appeared to be dependent upon recognition of parasite antigens by the injected T cells because no exacerbation of the disease process was seen after the transfer of similar T cell populations specific for an antigen unrelated to the parasite, namely ovalbumin. However, the inclusion of ovalbumin in the L. major infecting inoculum resulted in an exacerbating effect of ovalbumin-specific T cells on cutaneous leishmaniasis. These unexpected results were supported by observations showing that immunization of mice with L. major antigens in complete Freund's adjuvant 7 days before infection with L. major led to exacerbated lesions. A similar aggravation of L. major-induced cutaneous lesions was also observed in mice previously immunized with an unrelated antigen provided that this antigen was included in the L. major infecting inoculum.     

Adjuvant properties of thermal component of hyperthermia enhanced transdermal immunization: effect on dendritic cells

Hyperthermia enhanced transdermal (HET) immunization is a novel needle free immunization strategy employing application of antigen along with mild local hyperthermia (42°C) to intact skin resulting in detectable antigen specific Ig in serum. In the present study, we investigated the adjuvant effect of thermal component of HET immunization in terms of maturation of dendritic cells and its implication on the quality of the immune outcome in terms of antibody production upon HET immunization with tetanus toxoid (TT). We have shown that in vitro hyperthermia exposure at 42°C for 30 minutes up regulates the surface expression of maturation markers on bone marrow derived DCs. This observation correlated in vivo with an increased and accelerated expression of maturation markers on DCs in the draining lymph node upon HET immunization in mice. This effect was found to be independent of the antigen delivered and depends only on the thermal component of HET immunization. In vitro hyperthermia also led to enhanced capacity to stimulate CD4+ T cells in allo MLR and promotes the secretion of IL-10 by BMDCs, suggesting a potential for Th2 skewing of T cell response. HET immunization also induced a systemic T cell response to TT, as suggested by proliferation of splenocytes from immunized animal upon in vitro stimulation by TT. Exposure to heat during primary immunization led to generation of mainly IgG class of antibodies upon boosting, similar to the use of conventional alum adjuvant, thus highlighting the adjuvant potential of heat during HET immunization. Lastly, we have shown that mice immunized by tetanus toxoid using HET route exhibited protection against challenge with a lethal dose of tetanus toxin. Thus, in addition to being a painless, needle free delivery system it also has an immune modulatory potential.     

KM(+), a lectin from Artocarpus integrifolia, induces IL-12 p40 production by macrophages and switches from type 2 to type 1 cell-mediated immunity against Leishmania major antigens, resulting in BALB/c mice resistance to infection.

The outcome and severity of some diseases correlate with the dominance of either the T helper 1 (Th1) or Th2 immune response, which is stimulated by IL-12 or IL-4, respectively. In the present study we demonstrate that gamma interferon (IFN-gamma) secretion by murine spleen cells stimulated with KM(+), a mannose-binding lectin from Artocarpus integrifolia, is due to IL-12 induction, because (1) macrophages from several sources (including cell lines) produced IL-12 p40 in response to KM(+), and (2) lectin-free supernatants from J774 cell line cultures stimulated with KM(+) induced the secretion of IFN-gamma by spleen cell cultures, an effect blocked by the supernatant pretreatment with anti-IL-12 antibody. The known pattern of susceptibility of BALB/c mice to infection with Leishmania major, attributed to high levels of IL-4 production leading to a Th2 nonprotective immune response, was modified by administration of KM(+). Draining lymph node cells from these immunized BALB/c mice (in contrast to cells from animals immunized only with soluble leishmanial antigen [SLA]) secreted high levels of IFN-gamma and low levels of IL-4, which characterized a Th1 rather than a Th2 response pattern. The footpad thickness of BALB/c mice immunized with SLA plus KM(+) and challenged with L. major was similar to that of uninfected mice. This beneficial effect against leishmanial infection was blocked by pretreatment of these mice with anti-IL-12 antibody. These observations indicate that KM(+) induces IL-12 p40 in vivo and has a protective effect against L. major infection.     

Splenic cathepsin L is maturated from the proform by interferon-gamma after immunization with exogenous antigens

The processing of foreign protein antigens into peptides requires the participation of various endo/lysosomal proteases in antigen-presenting cells (APCs). In this study, a proenzyme of cathepsin L, procathepsin L, was found to be present in the spleens of naive mice, as demonstrated by immunoblotting. Interestingly, the maturation of cathepsin L from procathepsin L was strongly induced when the host BALB/c mice were immunized with ovalbumin or soluble leishmanial antigen, despite the fact that mouse albumin, a kind of self-antigen, did not have such a potential. Furthermore, foreign antigens, but not self-antigens, could increase the activity of cathepsin L, probably being mediated by interferon-gamma, as demonstrated by in vivo and in vitro experiments. As cathepsin L matured, the efficiency of antigen processing was increased in APCs. These results suggest that endo/lysosomal cathepsin L plays an important role in the immune regulation via antigen processing even in peripheral lymphoid tissues as well as in the thymus.     

Influence of different routes of anti-tumor immunization: alternative induction of tumor immunity and tumor enhancement.

Chickens and quails were immunized in parallel either i.v. or intramuscularly (i.m.) with lectin column-purified antigens from chick embryo cells that were transformed in vitro by avain sarcoma virus (ASV). After five to six injections, immunity of the animals was tested by challenge with ASV into the wing webs. Whereas tumor growth was inhibited after i.v. immunization with respect to incidence rate and time of tumor appearance, tumor growth was enhanced after i.m. injection. Animals that were injected with normal cell antigens served as controls. Spleen cells from only those animals that were immunized i.v. exerted a cytotoxic effect in vitro against ASV-transformed cells, whereas spleen cells from i.m. injected animals, in contrast, suppressed such cytotoxicity. The search for serum blocking or arming factors suggested that sera from i.m. injected animals block cellular cytotoxicity whereas sera from i.v. immunized animals render normal spleen cells cytotoxic (arming effect). The use of viruses from different subgroups and of antigens from gp85-lacking ASV-transformed cells indicates that immune effects were obtained against tumor cell surface antigens that differ from the antigen that is involved in virus neutralization (s-gp85).     

Lacto-N-fucopentaose III found on Schistosoma mansoni egg antigens functions as adjuvant for proteins by inducing Th2-type response.

We have recently demonstrated that induction of Th2 responses by Schistosoma mansoni egg Ag is largely due to carbohydrates on the Ag functioning as adjuvants. Lacto-N-fucopentaose III (LNFPIII), a polylactosamine sugar, is the predominant carbohydrate found in S. mansoni egg Ag. Therefore, using neoglycoprotein, we investigated whether LNFPIII induces in vivo Th2 response and functions as an adjuvant. Following intranasal immunization with LNFPIII linked to human serum albumin (HSA) (HSA-LNFPIII), BALB/c mice mounted a strong Th2 response and produced significantly higher levels of total IgE as well as HSA-specific IgG, IgG1, and IgE. HSA-LNFPIII was over 1000-fold more potent in inducing Ab production as compared with HSA alone. Although LNFPIII itself did not function as an epitope for either IgG or IgE, its conjugation with protein was essential for the adjuvant activity. Moreover, fucose residue on LNFPIII was crucial for induction of Ab production. Nasal lymphocytes from mice immunized with HSA-LNFPIII produced IL-4, IL-5, and IL-10, but not IFN-gamma following in vitro stimulation with HSA or HSA-LNFPIII. In addition, these activated nasal lymphocytes also showed a significant increase of B7-2 expression on B220-positive cells. Furthermore, not only intranasal but also both i.p. and s.c. immunization with HSA-LNFPIII induced significant production of HSA-specific Abs compared with the immunization with HSA alone, suggesting that the activity of LNFPIII was not restricted on particular route of immunization. These results demonstrate that Lewis type carbohydrate LNFPIII can function as an adjuvant by their ability to induce a Th2 response.     

BCG expressing LCR1 of Leishmania chagasi induces protective immunity in susceptible mice

Cellular immune responses are required for protective immunity against Leishmania chagasi. Immunization strategies using live intracellular bacteria (e.g., bacille-Calmette Guerin strain of Mycobacterium bovis) expressing recombinant antigens can induce cellular immune responses to these antigens. Previous studies demonstrated that the L. chagasi antigen LCR1 stimulates IFN-gamma production from T cells of infected BALB/c mice, and immunization with recombinant LCR1 partially protects against L. chagasi infection. To determine whether live bacteria could enhance the immunization potential of LCR1, we engineered BCG expressing LCR1 (BCG-LCR1). Subcutaneous immunization with BCG-LCR1, but not with BCG containing plasmid only (BCG-pMV261), elicited better protective immunity against L. chagasi infection than LCR1 protein alone. BCG-LCR1 administered intraperitoneally did not protect. Splenocytes from mice immunized s.c. with either BCG-LCR1 or BCG-pMV261 and then infected with L. chagasi promastigotes had increased antigen-induced IFN-gamma and reduced IL-10 production compared to splenocytes of control mice. We propose that BCG-LCR1 promotes a Th1-type protective immune response, and it may be a useful component of a Leishmania vaccine.