Heligmosomoides polygyrus (=Nematospiroides dubius): suppression of antibody response to orally administered sheep erythrocytes in infected mice.

Mice infected with 200 to 300 Heligmosomoides polygyrus had reduced serum hemagglutinin titers following a series of oral inoculations of sheep erythrocytes (SRBC) when compared to similarly inoculated uninfected mice. Study of antibody-producing cells by the indirect hemolytic plaque technique demonstrated a low splenic response to oral immunization in which IgA predominated. No alteration was evident in the proportions of antibody-containing cells in the different Ig classes with infection. Comparison of the immune response to oral and intraperitoneal routes of SRBC inoculation in infected and uninfected mice demonstrated a similar reduction in antibody titer with both routes of inoculation, although immunosuppression following intraperitoneal inoculations was not consistantly observed. The data are discussed in relation to the influence of the helminth infection on intestinal immune response and systemic immune response.     

Taenia solium: Immune response against oral or systemic immunization with purified recombinant calreticulin in mice

Recombinant functional Taenia solium calreticulin (rTsCRT) confers different degrees of protection in the experimental model of intestinal taeniosis in hamsters. The aim of this study was to evaluate the immune response induced after oral or systemic immunization with an electroeluted rTsCRT in BALB/c mice. Oral immunization elicited high fecal IgA and the production of IL-4 and IL-5 by mesenteric lymph node cells after in vitro stimulation with rTSCRT, indicating a Th2 response. Mice subcutaneously immunized produced high amounts of serum IgG, being IgG1 (Th2-related) the predominant isotype, while in vitro stimulated spleen cells synthesized IL-4, IL-5 and also IFN-γ, indicating a mixed Th1/Th2 cellular response after systemic immunization. Our data show that purified rTsCRT induces polarized Th2 responses after oral immunization of mice, a common characteristic of protective immunity against helminths and, consequently, a desirable hallmark in the search for a vaccine.     

Cationization of protein antigens. II. Alteration of regulatory properties

Immunoregulatory effects of cationized bovine serum albumin (cBSA) and native bovine serum albumin (nBSA) have been investigated. Intravenous administration of nBSA to BDF1 mice substantially suppressed the antibody response to subsequent immunization with either nBSA or cBSA, whereas pretreatment with cBSA by the same route significantly enhanced the responses to both antigens. The functional properties of BSA-specific T and B cells from mice immunized with cBSA or nBSA were examined in reconstitution experiments in which splenic T populations together with B cells were transferred into irradiated syngeneic recipients. Transfer of splenic T cells from mice primed with nBSA caused profound suppression of the response to subsequent immunization with nBSA or cBSA, whereas transfer of either B or T cells from cBSA treated mice produced an enhanced response to both antigens. C57BL/6 mice, which are considered to be low responders to BSA, produced a significant antibody response to BSA when immunized with cBSA. In contrast, immunization with nBSA did not produce measureable amounts of antibody in mice of this strain. Our data clearly demonstrate that cationized BSA exhibits unique immunogenic properties due to alterations in the self-regulation of the immune response.     

Modulation of the immune response mediated by oral transgene administration of IL-10

In the current study, we analyze the immunomodulatory effect of oral transgene administration of IL-10 using a mice model of viral inflammation. Salmonella harboring a plasmid encoding the IL-10 gene (SLIL10) was administered by the oral route together with Salmonella carrying a plasmid encoding the glycoprotein D or B (SLgD, SLgB) of Herpes simplex virus type 2 (HSV-2). This resulted in a high inhibition of the cellular and human immune response against the viral proteins. When mice immunized against the HSV proteins were challenged with 10 lethal doses of HSV-2 by the intravaginal route, only those that had also received SLIL10 showed severe lesions and died. When Salmonella harboring pIL10 was administered orally to mice immunized by the intramuscular route with a plasmid encoding gD, inhibition of cellular and humoral immune responses were also observed but to a lesser extent than with oral immunization. By means of adoptive transfer experiments and in vitro experiments, we have subsequently determined that the mechanism possibly involved in the inhibition of the immune response could be a reduced antigenic presentation when mice receive SLIL10 that induced a state of anergy on specific T lymphocytes.     

Expressed Salmonella antigens within macrophages enhance the proliferation of CD4+ and CD8+ T lymphocytes by means of bystander dendritic cells

ATP-dependent Lon protease-deficient Salmonella enterica serovar Typhimurium (strain CS2022) appeared to invade successfully the mesenteric lymph nodes (MLN) and Peyer's patches (PP) of BALB/c mice and appeared to be easily eradicated by the host after oral immunization. As detected by flow cytometry, the population of major histocompatibility complex class I (MHC-I)-expressing macrophages and dendritic cells (DCs) was increased in the PP of mice immunized with CS2022 on day 6 after immunization. Thereafter, the population of splenic surface CD69(+) T lymphocytes prepared from mice immunized with CS2022 6 weeks prior to measurement increased as a result of the administration of the extracellular vesicles of RAW264.7 macrophage-like cells derived by Salmonella challenge. In addition, the proliferation of CD8(+) and even of CD4(+)T cells isolated from mouse spleens immunized with CS2022 was enhanced after cocultivation with naive DCs in the presence of the extracellular vesicles. These findings indicate that the extracellular vesicles prepared from the Salmonella-challenged macrophages carried salmonellae antigens to bystander DCs, thereby stimulating T-cell responses. Therefore, as antigen presentation after phagocytosis should be a central process in the T-cell activation that occurs in response to Salmonella infection, an oral immunization with CS2022 sufficiently induces T cell-mediated immunity in mice.     

Intramammary Immunization of Pregnant Mice with Staphylococcal Protein A Reduces the Post-Challenge Mammary Gland Bacterial Load but Not Pathology

Protein A, encoded by the spa gene, is one of the major immune evading MSCRAMM of S. aureus, demonstrated to be prevalent in a significant percentage of clinical bovine mastitis isolates in Australia. Given its’ reported significance in biofilm formation and the superior performance of S. aureus biofilm versus planktonic vaccine in the mouse mastitis model, it was of interest to determine the immunogenicity and protective potential of Protein A as a potential vaccine candidate against bovine mastitis using the mouse mastitis model. Pregnant Balb/c mice were immunised with Protein A emulsified in an alum-based adjuvant by subcutaneous (s/c) or intramammary (i/mam) routes. While humoral immune response of mice post-immunization were determined using indirect ELISA, cell-mediated immune response was assessed by estimation of interferon-gamma (IFN-γ) produced by protein A-stimulated splenocyte supernatants. Protective potential of Protein A against experimental mastitis was determined by challenge of immunized versus sham-vaccinated mice by i/mam route, based upon manifestation of clinical symptoms, total bacterial load and histopathological damage to mammary glands. Significantly (p<0.05) higher levels of IgG1 isotype were produced in mice immunized by the s/c route. In contrast, significantly higher levels of the antibody isotype IgG2a were produced in mice immunized by the i/mam route (p<0.05). There was significant reduction (p<0.05) in bacterial loads of the mammary glands of mice immunized by Protein A regardless of the route of immunization, with medium level of clinical symptoms observed up to day 3 post-challenge. However, Protein A vaccine failed to protect immunized mice post-challenge with biofilm producing encapsulated S. aureus via i/mam route, regardless of the route of immunization, as measured by the level of mammary tissue damage. It was concluded that, Protein A in its’ native state was apparently not a suitable candidate for inclusion in a cell-free vaccine formulation against mastitis.     

Intrarectal immunization with rotavirus 2/6 virus-like particles induces an antirotavirus immune response localized in the intestinal mucosa and protects against rotavirus infection in mice

Rotavirus (RV) is the main etiological agent of severe gastroenteritis in infants, and vaccination seems the most effective way to control the disease. Recombinant rotavirus-like particles composed of the viral protein 6 (VP6) and VP2 (2/6-VLPs) have been reported to induce protective immunity in mice when administered by the intranasal (i.n.) route. In this study, we show that administration of 2/6-VLPs by the intrarectal (i.r.) route together with either cholera toxin (CT) or a CpG-containing oligodeoxynucleotide as the adjuvant protects adult mice against RV infection. Moreover, when CT is used, RV shedding in animals immunized by the i.r. route is even reduced in comparison with that in animals immunized by the i.n. route. Humoral and cellular immune responses induced by these immunization protocols were analyzed. We found that although i.r. immunization with 2/6-VLPs induces lower RV-specific immunoglobulin G (IgG) and IgA levels in serum, intestinal anti-RV IgA production is higher in mice immunized by the i.r. route. Cellular immune response has been evaluated by measuring cytokine production by spleen and Peyer's patch cells (PPs) after ex vivo restimulation with RV. Mice immunized by the i.n. and i.r. routes display higher gamma interferon production in spleen and PPs, respectively. In conclusion, we demonstrate that i.r. immunization with 2/6-VLPs protects against RV infection in mice and is more efficient than i.n. immunization in inducing an anti-RV immune response in intestinal mucosa.     

Functional and quantitative analysis of splenic T cell immune responses following oral toxoplasma gondii infection in mice

Functional and quantitative analysis of splenic T cell immune responses following oral Toxoplasma gondii infection in mice. Experimental Parasitology 91, 212-221. Immunity to Toxoplasma gondii is mediated primarily by the host T cell response. Although there is considerable information regarding host immunity following intraperitoneal infection with tachyzoites, little information is available regarding naturally acquired infection following peroral infection with bradyzoites. In this study, a sequential quantitative analysis of the cell-mediated immune response was performed at the single cell level. To assess the kinetics of this response and parasitic loads, inbred mice were orally infected with the 76K strain bradyzoites of T. gondii. Within 24 h of infection, follicular hyperplasia followed by infiltration with histiocytes, macrophages, and apoptotic bodies was observed in the spleens of infected mice. T. gondii were detected from day 1, and counts increased gradually during the experimental period. Splenocyte DNA synthesis to antigen and mitogen was severely suppressed at days 7 and 10. The percentages of NK1.1(+) or delta gamma T cells were increased from day 1, whereas CD4(+) and CD8alpha+ T cells were signficantly increased after day 7 postinfection. CD25 expression and intracellular IFN-gamma production increased in NK1.1(+) cells on day 1 and by all other T cell subsets after day 4. Intracellular IL-4 did not increase until day 7, and IL-10 production was increased in all T cell subsets after day 4. Together, these findings indicate that oral infection with T. gondii stimulates a strong cellular immune response that appears to polarize toward an early Th1 response. However, within 7 days, a strong immune Th2 regulatory response as well as high parasitic loads can be observed, with a reduction in lymphoproliferation to mitogen stimulation, increased production of IL-4 and IL-10, and evidence of T cell apoptosis in the splenic immune compartment.     

Immunity to avirulent enterovirus 71 and coxsackie A16 virus protects against enterovirus 71 infection in mice

In this study, we sought to determine whether intratypic and intertypic cross-reactivity protected against enterovirus 71 (EV71) infection in a murine infection model. We demonstrate that active immunization of 1-day-old mice with avirulent EV71 strain or coxsackie A16 virus (CA16) by the oral route developed anti-EV71 antibodies with neutralizing activity (1:16 and 1:2, respectively). Splenocytes from both EV71- and CA16-immunized mice proliferated upon EV71 or CA16, but not coxsackie B3 virus (CB3), antigen stimulation. Immunized mice became more resistant to virulent EV71 strain challenge than nonimmunized mice. There was an increase in the percentage of activated splenic T cells and B cells in the immunized mice 2 days after EV71 challenge. The CA16 immune serum reacted with EV71 antigens in an enzyme-linked immunosorbent assay and neutralized EV71 but not CB3 or poliovirus at a titer of 1:4. Passive immunization with the CA16 immune serum reduced the clinical score, diminished the organ viral load, and increased the survival rate of mice upon EV71 challenge. CB3 neither shared in vitro cross-reactivity with EV71 nor provided in vivo protection after both active and passive immunization. These results illustrated that live vaccine is feasible for EV71 and that intertypic cross-reactivity of enteroviruses may provide a way to determine the prevalence of EV71.     

Induction of a cellular immune response to a foreign antigen by a recombinant Listeria monocytogenes vaccine.

A recombinant strain of Listeria monocytogenes that stably and constitutively expresses Escherichia coli beta-galactosidase was used as a live vaccine vector. BALB/c mice were immunized orally or parenterally with the recombinant L. monocytogenes, and their cellular and humoral immune responses to beta-galactosidase were measured. Spleen cells taken 1 week after oral inoculation or 5 weeks after oral or parenteral inoculation (with a boost at 4 weeks) showed beta-galactosidase-specific CTL responses. The CTL line derived from mice immunized i.p. was also shown to be class I restricted and Thy-1.2+, CD8+, and TCR alpha beta+. All mice immunized with the recombinant L. monocytogenes had positive delayed-type hypersensitivity responses to heat-killed L. monocytogenes, but only 15% had a positive delayed-type hypersensitivity reaction to beta-galactosidase. Individual serum samples from mice immunized i.p. or i.v. were tested for antibody to beta-galactosidase. Approximately 11% had low positive titers for beta-galactosidase antibodies. These results demonstrate that both oral and parenteral immunization with recombinant L. monocytogenes results in a cellular immune response to the foreign protein, which is primarily a specific CD8+ CTL response.     

Mucosal delivery of ACNPV baculovirus driving expression of the Gal-lectin LC3 fragment confers protection against amoebic liver abscess in hamster

Mucosal vaccination against amoebiasis using the Gal-lectin of E. histolytica has been proposed as one of the leading strategies for controlling this human disease. However, most mucosal adjuvants used are toxic and the identification of safe delivery systems is necessary. Here, we evaluate the potential of a recombinant Autographa californica baculovirus driving the expression of the LC3 fragment of the Gal-lectin to confer protection against amoebic liver abscess (ALA) in hamsters following oral or nasal immunization. Hamsters immunized by oral route showed complete absence (57.9%) or partial development (21%) of ALA, resulting in some protection in 78.9% of animals when compared with the wild type baculovirus and sham control groups. In contrast, nasal immunization conferred only 21% of protection efficacy. Levels of ALA protection showed lineal correlation with the development of an anti-amoebic cellular immune response evaluated in spleens, but not with the induction of seric IgG anti-amoeba antibodies. These results suggest that baculovirus driving the expression of E. histolytica vaccine candidate antigens is useful for inducing protective cellular and humoral immune responses following oral immunization, and therefore it could be used as a system for mucosal delivery of an anti-amoebic vaccine.     

Evaluation of the Lon-deficient Salmonella strain as an oral vaccine candidate

We evaluated the efficacy of CS2022 (the Lon protease-deficient mutant strain of Salmonella enterica serovar Typhimurium) as a candidate live oral vaccine strain against subsequent oral challenge with a virulent strain administered to BALB/c and C57BL/6 mice. CS2022 persistently resided in the spleen, mesenteric lymph nodes, Peyer's patches, and cecum of both strains of mice after a single oral inoculation with 1 x 10(8) colony-forming units. Finally, CS2022 almost disappeared from each tissue sample by week 12 in BALB/c mice, whereas CS2022 still resided in each tissue type at week 12 after inoculation of C57BL/6 mice. A significant increase in the serovar Typhimurium lipopolysaccharide-specific secretory immunoglobulin A (s-IgA), as measured for one of the mucosal immune responses, was detected in bile and intestinal samples of both strains of immunized mice at week 4 after immunization. In addition, the expression of gamma interferon mRNA in the spleens of both strains of immunized mice, especially those of C57BL/6 mice, was significantly increased at week 4 after immunization and was boosted during the following 5 days after the challenge was administered to the mice. Furthermore, peritoneal macrophages isolated from immunized mice at week 4 after immunization exhibited an increase in intracellular killing activity against both virulent and avirulent Salmonella. The present results suggested that salmonellae-specific s-IgA on the mucosal surfaces induced by immunization with CS2022 generally prevented mice from succumbing to an oral challenge with a virulent strain. Simultaneously, CS2022 promoted the protective immunity associated with macrophages in both strains of mice.     

Trypanosoma gambiense: immunosuppression and polyclonal B-cell activation in mice

The relationship between the suppression of antibody response and polyclonal B-cell activation was studied in mice treated with a cell homogenate of Trypanosoma gambiense. The cell homogenate injection in mice caused a progressive increase in splenic background plaque-forming cell response to sheep erythrocyte. In the mice with markedly increased background plaque-forming cell response, the different reactivity in the primary antibody response to sheep erythrocytes was observed between the intraperitoneal and intravenous immunization with sheep erythrocytes. The intraperitoneal immunization of mice with sheep erythrocytes strongly suppressed the antibody response, while the intravenous immunization with sheep erythrocytes led to an enhancement of the antibody response. The intraperitoneal injection of silica particles, a toxic agent to macrophages, 30 min before intraperitoneal immunization with sheep erythrocytes abolished the suppression of the antibody response completely. In addition, restoration of the suppressed antibody response was found in mice immunized intraperitoneally with a high dose of sheep erythrocytes. It appears that the suppression of antibody response is not attributable to polyclonal B-cell activation, and is associated with the elevation of the phagocytic activity of peritoneal macrophages.     

Modulation of T cell functions by sperm-specific lactate dehydrogenase: fluorescence analysis of immune competent cells and local graft versus host reaction.

Immune responses to a well-defined sperm-specific isogenic lactate dehydrogenase-C4 (LDH-C4) have been studied in C57Bl/Ks (H-2d) mice after immunization through intra-rectal route. Presence of anti-LDH-C4-antibodies in the sera of females immunized in presence or absence of adjuvant suggested that the immune system of mice becomes exposed to sperm antigens following intrarectal insemination. LDH-C4 primed lymphocytes from both males and females, when transferred in F1 hybrids, suppressed stimulation index of local graft versus host reaction. However, contrary to females, male counterparts which did not elicit measurable anti-LDH-C4-antibody titer, showed the presence of a higher proportion of Ly2+ and Ia+ fluorescence labelled cells in the spleen of LDH-C4 administered mice. Results suggest that males are more susceptible for immune suppression of T cell functions through generation of T suppressor cells. Sex differences in relation to immune deviation by intra-rectal administration of sperm-specific LDH-C4 in mice and their consequences in AIDS and AIDS-related complex diseases are described.     

携带HBV包膜大蛋白DNA疫苗的减毒沙门菌在小鼠诱导免疫应答

探索一种简便、有效的乙型肝炎病毒DNA疫苗免疫方法。将编码绿色荧光蛋白的真核表达质粒pEGFPN1转化到减毒鼠伤寒沙门菌SL7207,灌胃饲服BALB/c小鼠,流式细胞术检测出小鼠脾细胞内表达的绿色荧光蛋白;构建编码HBV包膜大蛋白的DNA疫苗pCIS1S2S,分别以SL7207为载体的口服途径或直接肌肉注射途径免疫BALB/c小鼠,检测小鼠的血清抗体、T细胞增殖和细胞毒性T淋巴细胞反应,结果表明两种免疫途径均能在小鼠体内诱生细胞和体液免疫应答,但口服途径诱导免疫应答的强度明显强于肌肉注射途径。口服携带HBV DNA疫苗的减毒伤寒沙门菌可能代表一种简便、有效的治疗乙型肝炎的新方法。      

Intraperitoneal immunization led to T cell hyporesponsiveness to Helicobacter pylori infection in mice

During Helicobacter pylori infection, T cell response is critical in the development of active gastritis and in protective immunity against infection. We studied gastric inflammation and T cell response in H. pylori-challenged mice following an intraperitoneal immunization, using whole H. pylori lysate (HpAg) in the absence of adjuvants. H. pylori-challenged mice without immunization developed moderate to severe gastric inflammation, and splenocytes from these mice produced Th1 polarizing cytokines in response to HpAg and Con A during the acute infection. On the other hand, immunized-challenged mice (those inoculated with H. pylori following immunization) had little or no gastric inflammation despite persistent H. pylori colonization. Our immunization primed splenocytes to produce IL-2, IFN-gamma, and IL-4 in response to HpAg and Con A before infection. However, these cells became hyporesponsive to both stimulants immediately after live bacterial challenge in terms of the production of these cytokines, especially IL-2 and IFN-gamma. CTLA-4 has been documented to be a negative regulator of IL-2 production and lymphoproliferation that induces peripheral tolerance and functions 24-72 hr after the initiation of T cell activation. Compared with challenged mice, T cells from immunized-challenged mice showed higher levels of CTLA-4 expression at 72 hr after oral challenge. These data suggested that our immunization inhibited the development of H. pylori-associated gastritis and induced T cell hyporesponsiveness to H. pylori infection, which might be mediated by the early induction of CTLA-4 following challenge.     

Efficacy of oral administration of live herpes simplex virus type 1 as a vaccine.

Mice given herpes simplex virus type 1 (HSV-1) (Miyama +GC strain) intragastrically via a stainless-steel cannula were rendered immune to subsequent lethal intraperitoneal (i.p.) challenge with HSV-1. The orally administered HSV-1 was completely inactivated in the stomach within a few minutes of inoculation. However, systemic immunity was established 14 days after oral inoculation with the virus and retained for up to 6 months. The mechanisms of establishing systemic immunity were investigated by means of adoptive transfer comparisons. When splenic cells from HSV-1-immunized mice were transplanted into nonimmunized mice, all of the recipient mice survived after a lethal i.p. challenge with the virus. Immunity was not established in antithymocyte serum-treated mice or by transfer of serum from immunized to nonimmunized mice. In addition, all HSV-1-immunized mice died after lethal challenge with HSV-2 and influenza virus A. These findings suggest that the immunity was virus specific, with T lymphocytes playing a major role in its establishment. The present study therefore supports the possibility of oral immunization with live HSV-1 as a vaccine.     

Interrelations of cellular and humoral immune response and different doses of sheep erythrocytes in mice]

In experiments on CBA and C57BL/6 mice the generation of antibody-forming cells respectively either in the popliteal lymph nodes or spleen as well as a rate of delayed type hypersensitivity response (DTHR) on the background of subcutaneous (into foot) or intraperitoneal injection of different doses of sheep erythrocytes (from 10(4) to 10(8)) have been studied. In so doing two types of immune response can be isolated on the dependence upon the sensitivity threshold to antigen of DTHR and humoral immunity. Thus in C57BL/6 mice the antigen threshold for DTHR is of one time (in intraperitoneal immunization) or of a two times (in subcutaneous) lower order than for antibody response. In CBA line mice under subcutaneous immunization there can be seen quite an opposite picture while intraperitoneal immunization causes exact correlation of antigen threshold for cellular and humoral immune response.     

Prime-boost immunization schedules based on influenza virus and vaccinia virus vectors potentiate cellular immune responses against human immunodeficiency virus Env protein systemically and in the genitorectal draining lymph nodes

Vaccines that elicit systemic and mucosal immune responses should be the choice to control human immunodeficiency virus (HIV) infections. We have previously shown that prime-boost immunizations with influenza virus Env and vaccinia virus (VV) WR Env recombinants induced an enhanced systemic CD8(+) T-cell response against HIV-1 Env antigen. In this report, we analyzed in BALB/c mice after priming with influenza virus Env the ability of two VV recombinants expressing HIV-1 Env B (VV WR Env and the highly attenuated modified VV Ankara [MVA] Env) to boost cellular immune responses in the spleen and in the lymph nodes draining the genital and rectal tracts. Groups of mice were primed by the intranasal route with 10(4) PFU of influenza virus Env and boosted 14 days later by the intraperitoneal or intranasal route with 10(7) PFU of MVA Env or VV WR Env, while the control group received two immunizations with influenza virus Env. We found that the combined immunization (Flu/VV) increased more than 60 times the number of gamma interferon-specific CD8(+) T cells compared to the Flu/Flu scheme. Significantly, boosting with MVA Env by the intraperitoneal route induced a response 1.25 or 2.5 times (spleen or genital lymph nodes) higher with respect to that found after the boost with VV WR Env. Mice with an enhanced CD8(+) T-cell response also had an increased Th1/Th2 ratio, evaluated by the cytokine pattern secreted following in vitro restimulation with gp160 protein and by the specific immunoglobulin G2a (IgG2a)/IgG1 ratio in serum. By the intranasal route recombinant WR Env booster gave a more efficient immune response (10 and 1.3 times in spleen and genital lymph nodes, respectively) than recombinant MVA Env. However, the scheme influenza virus Env/MVA Env increased four times the response in the spleen, giving a low but significant response in the genital lymph nodes compared with a single intranasal immunization with MVA Env. These results demonstrate that the combination Flu/MVA in prime-booster immunization regimens is an effective vaccination approach to generate cellular immune responses to HIV antigens at sites critical for protective responses.     

Neonate Intestinal Immune Response to CpG Oligodeoxynucleotide Stimulation

Background

The development of mucosal vaccines is crucial to efficiently control infectious agents for which mucosae are the primary site of entry. Major drawbacks of these protective strategies are the lack of effective mucosal adjuvant. Synthetic oligodeoxynucleotides that contain several unmethylated cytosine-guanine dinucleotide (CpG-ODN) motifs are now recognized as promising adjuvants displaying mucosal adjuvant activity through direct activation of TLR9-expressing cells. However, little is known about the efficacy of these molecules in stimulating the intestinal immune system in neonates.

Methodology/Principal Findings

First, newborn mice received CpG-ODN orally, and the intestinal cytokine and chemokine response was measured. We observed that oral administration of CpG-ODN induces CXC and CC chemokine responses and a cellular infiltration in the intestine of neonates as detected by immunohistochemistry. We next compared the efficiency of the oral route to intraperitoneal administration in stimulating the intestinal immune responses of both adults and neonates. Neonates were more responsive to TLR9-stimulation than adults whatever the CpG-ODN administration route. Their intestinal epithelial cells (IECs) indirectly responded to TLR9 stimulation and contributed to the CXC chemokine response, whereas other TLR9-bearing cells of the lamina-propria produced CC chemokines and Th1-type cytokines. Moreover, we showed that the intestine of adult exhibited a significantly higher level of IL10 at homeostasis than neonates, which might be responsible for the unresponsiveness to TLR9-stimulation, as confirmed by our findings in IL10-deficient mice.

Conclusions/Significance

This is the first report that deciphers the role played by CpG-ODN in the intestine of neonates. This work clearly demonstrates that an intraperitoneal administration of CpG-ODN is more efficient in neonates than in adults to stimulate an intestinal chemokine response due to their lower IL-10 intestinal level. In addition we report the efficiency of the oral route at inducing intestinal chemokine responses in neonate that might be taken into consideration for further vaccine development against neonatal diseases.