Parasitic infection and the polarized Th2 immune response can alter a vaccine-induced immune response

The AIDS epidemic in the Developing World represents a major global crisis. It is imperative that we develop an effective vaccine. Vaccines are economically the most efficient means of controlling viral infections. However, the development of a vaccine against HIV-1 has been a formidable task, and in developing countries chronic parasitic infection adds another level of complexity to AIDS vaccine development. Helminthic and protozoan infections, common in developing countries, can result in a constant state of immune activation that is characterized by a dominant Th2 type of cytokine profile, high IgE levels, and eosinophilia. Such an immune profile may have an adverse impact on the efficacy of vaccines, in particular, an HIV-1 vaccine. Indeed, the CD8 cellular immune response and the corresponding Th1 type cytokines that enhance the CD8 cellular immune response are important for clearing many viral infections. It is believed that an antigen specific CD8 cellular immune response will be an important component of an HIV-1 vaccine.     

Skewed Th1/Th2 immune response to Sarcoptes scabiei

Scabies is a contagious skin disease of humans and many other species of mammals. Previous studies suggested that the balance between the Th1 and Th2 immune responses may influence the outcome of a scabies infestation in a sensitized host. Therefore, in this study, we examined the T-helper cell cytokine profiles of splenocytes and lymph node cells in BALB/c mice that were immunized with scabies extract (primary response), infested with scabies mites (primary response), or immunized and then infested (secondary response). Lymphocyte cytokine expression was analyzed by flow cytometry after staining for intracellular cytokines. Immunization with scabies extract induced production of interferon-gamma (IFNgamma) (Th1 response) by both spleen and lymph node cells. Mice that were infested with scabies increased production of interleukin-4 by lymph node cells and of IFNgamma by splenocytes. Mice that were first immunized and then infested with mites increased production of IFNgamma by both spleen and lymph node cells. However, this increased level of IFNgamma was only about half of that induced by immunization alone. These results suggest that live scabies mites produced something that inhibited IFNgamma production in the lymph nodes of scabies-immunized mice. Our data also indicate that lymphocytes in the spleen and lymph nodes can present different cytokine response profiles.     

Different cytokines are required for induction and maintenance of the Th2 type response in DBA/2 mice resistant to infection with Leishmania major

Experimental cutaneous leishmaniasis is a useful model in studying the mechanism regulating immune responses between T helper type 1 (Th1) and Th2. Mice susceptible to Leishmania major infection such as BALB/c (H-2(d)) are associated with the induction of the disease-promoting Th2 response, while the resistant mice such as DBA/2 (H-2(d)) develop the protective Th1 response. To understand the induction mechanism of Th1 and Th2 responses, it is necessary to establish an immunization scheme by which the induction of each Th response can be easily and experimentally controlled. Adjuvants are known to enhance the immune responses through the combined effect of several factors: prolonged release of antigen, migration of cells, mitogenic effect and so forth. When the genetically resistant DBA/2 mice were immunized twice with soluble leishmanial antigen (SLA), emulsified in incomplete Freund's adjuvant (IFA) before L. major inoculation, these mice mounted a Th2 cell response and suffered from progressive infection. While IL-4 and IL-13 were upregulated early after the infection in both healer and non-healer groups of mice, IL-5 and IL-10 were upregulated only in non-healer mice. From these results, IL-5 and IL-10 appear to have an important role, at least in the early phases of the infection, rather than IL-4 and IL-13 in establishing the disease-promoting Th2 response in leishmaniasis. Further, IL-9 was found to be expressed in both BALB/c and DBA/2 mice immunized with IFA/SLA. This cytokine may support the establishment of a Th2 response in these mice. Therefore it is suggested that Th2 cytokines play different roles between priming and maintaining the Th2 immune response after the infection.     

Oral beta-glucan adjuvant therapy converts nonprotective Th2 response to protective Th1 cell-mediated immune response in mammary tumor-bearing mice

Beta (1-3)-D-glucans were identified almost 40 years ago as biological response modifiers that stimulated tumor rejection. In vitro studies have shown that beta-glucans bind to a lectin domain within complement receptor type 3 (CR3), or to, more recently described dectin-1 a beta-glucan specific receptor, acting mainly on phagocytic cells. In this study, we assessed the intracellular cytokine profiles of peripheral blood lymphocytes from mice bearing mammary tumors receiving i.v. anti-tumor mAbs combined or not with whole glucan particle suspension given orally (WGP, 400 microg every 24 hours). The proportions of T cells producing IL-4 and IFNgamma were determined by flow cytometry. The proportion of T cells producing IL-4 was significantly higher in tumor-bearing mice not receiving beta-glucan-enhanced therapy. Conversely, T cells from mice undergoing beta-glucan-enhanced therapy showed increased production of the Th1 cytokine IFNgamma. The switch from a Th2 to a Th1 response after WGP therapy was possibly mediated by intestinal mucosal macrophages releasing IL-12.     

Preferential Th1 immune response in invariant chain-deficient mice

MHC class II molecules associate with the invariant chain (Ii) molecule during biosynthesis. Ii facilitates the folding of class II molecules, interferes with their peptide association, and is involved in MHC class II transport. In this study, we have investigated the in vitro and in vivo immune response of Ii-deficient mice (Ii(-/-)). Our results have demonstrated that CD4(+) T cells from Ii(-/-) mice proliferate normally in vitro after in vivo immunization with protein Ags. However, cytokine secretion profiles of Ag-primed CD4(+) T cells from Ii(-/-) mice differ from CD4(+) T cells from wild-type mice. Whereas cells from wild-type mice secrete IFN-gamma and IL-4, cells from Ii(-/-) mice secrete mostly IFN-gamma. Moreover, Ii(-/-) mice exhibit a normal Th1 response in the delayed-type hypersensitivity and trinitrobenzene sulfonic acid colitis models; however, these mice lack an in vivo Th2 response, as demonstrated in the asthma model. Therefore, we suggest that defective Ag presentation in Ii(-/-) mice leads selectively to a Th1 effector response.     

A balanced type 1/type 2 response is associated with long-term nonprogressive human immunodeficiency virus type 1 infection

Previous reports have emphasized the requirements for strong type 1 cell-mediated responses in the control of human immunodeficiency virus type 1 (HIV-1). HIV-1 Gag p24-specific CD4 helper T-lymphocyte (HTL) responses have been shown to inversely correlate with viral burden in HIV-1-infected individuals. In this study, peripheral blood mononuclear cells from 70 individuals with chronic progressive HIV-1 infection (clinical progressors), 10 clinical nonprogressors, and 3 immunologically discordant progressors were assessed for HTL proliferation and type 1/type 2 cytokine production. Clinical progressors lacked functional HIV-1-specific HTLs with proliferative and cytokine-producing capacity. Clinical nonprogressors were found to respond to a wide range of HIV-1 antigens from different clades, producing both type 1 and type 2 cytokines. Immunologically discordant progressors responded strongly to clade B Gag p24 with a type 1 cytokine profile but not to other antigens. Thus, in contrast to clinical nonprogressors, neither progressors nor immunologically discordant progressors secreted interleukin-4 (IL-4) in response to HIV-1 antigens. Both clinical nonprogressors and immunologically discordant progressors responded broadly to B clade Gag p24-overlapping peptides. However, IL-4 production in the nonprogressors was restricted to a limited number of p24 peptides. No HIV-1-specific T-cell responses were seen in 20 seronegative controls. Additionally, we observed a rapid type 1 to type 2 shift in the response of one immunologically discordant progressor upon onset of clinical symptoms. These results suggest that a balanced type 1/type 2 profile correlates with successful long-term control of HIV-1.     

A HER-2/neu peptide admixed with PLA microspheres induces a Th1-biased immune response in mice

The elimination of cancer cells requires strong cellular immune responses, and these responses are induced by the activation of Th1 lymphocytes. In this work, the possibility of inducing a Th1 type of immune response in vivo by mixing a HER-2/neu synthetic CTL (cytotoxic T lymphocyte) peptide [HER-2/neu (789-797)], with poly-lactide (PLA) microspheres was investigated. Various formulations of the peptide were administered to HLA-A2.1 transgenic (HHD) mice. Cellular experiments, assessing proliferation and cytokine determination in splenocyte culture supernatants, were carried out in order to evaluate the type of immune response to the antigen. The in vivo administration of the peptide antigen admixed with the PLA microspheres induced a potent immune response which was comparable to that induced by the combination of the antigen in complete Freund's adjuvant (CFA). Furthermore, the cytokine profile produced by the T lymphocytes of the immunized animals indicated that the combination of the peptide antigen with the PLA microspheres induced a strong Th1 biased immune response to the antigen. The time of peptide incubation with the microspheres prior to administration did not affect the immune response, which further simplifies the preparation of this type of vaccine. The results justify further investigation of the possibility of inducing effective cellular immune responses against cancer cells overexpressing HER-2/neu molecules by simply mixing appropriate HER-2/neu peptide antigens with PLA microspheres.     

Enhanced Th1 response to Staphylococcus aureus infection in human lactoferrin-transgenic mice

Lactoferrin (Lf) is an iron-binding protein of external secretions and neutrophil secondary granules with antimicrobial and immunomodulatory activities. To further define these properties of Lf, we have investigated the response to Staphylococcus aureus infection in transgenic mice carrying a functional human Lf gene. The transgenic mice cleared bacteria significantly better than congenic littermates, associated with a trend to reduced incidence of arthritis, septicemia, and mortality. We identified two pathways by which S. aureus clearance was enhanced. First, human Lf directly inhibited the growth of S. aureus LS-1 in vitro. Second, S. aureus-infected transgenic mice exhibited enhanced Th1 immune polarization. Thus, spleen cells from infected transgenic mice produced higher levels of TNF-alpha and IFN-gamma and less IL-5 and IL-10 upon stimulation ex vivo with the exotoxin toxic shock syndrome toxin-1 compared with congenic controls. To confirm that these effects of Lf transgene expression could occur in the absence of live bacterial infection, we also showed that Lf-transgenic DBA/1 mice exhibited enhanced severity of collagen-induced arthritis, an established model of Th1-induced articular inflammation. Higher levels of stainable iron in the spleens of transgenic mice correlated with human Lf distribution, but all other parameters of iron metabolism did not differ between transgenic mice and wild-type littermates. These results demonstrate that human Lf can mediate both antimicrobial and immunomodulatory activities with downstream effects on the outcome of immune pathology in infectious and inflammatory disease.     

Cellular immune response and Th1/Th2 cytokines in human neurocysticercosis: lack of immune suppression.

Some reports have suggested that human neurocysticercosis (NCC) induces immunosuppression. To test this hypothesis, we performed a study on active cases of NCC who had not received cestocidal or immunosuppressive treatments. We examined blood counts and specific T cell markers (CD3, CD4, and CD8) by flow cytometry and found no differences between patients with NCC and healthy individuals. Both groups responded to concanavalin A (Con A), and patients with NCC responded more to a parasite crude antigen than uninfected individuals. Peripheral blood mononuclear cells were examined for interleukin (IL)-2, interferon-gamma, IL-10, and IL-4 mRNA. Regardless of infection status, more than 60% of individuals synthesized IL-2 mRNA and, less frequently, the other cytokines. These data suggest that immunosuppression does not occur in NCC patients.     

Cathepsin L is crucial for a Th1-type immune response during Leishmania major infection

Prior to the activation of CD4+ T cells, exogenous proteins are digested by endo/lysosomal enzymes in antigen-presenting cells (APCs) to produce antigenic peptides that are presented on MHC class II molecules. In the studies described here, the functional significance of cathepsin L for antigen processing and Th1/Th2 differentiation in experimental leishmaniasis was investigated. We first demonstrated that cathepsin L is one of the candidates for endo/lysosomal enzymes in the processing of soluble Leishmania antigen (SLA) by using CLIK148, a specific inhibitor of cathepsin L. Treatment of BALB/c or DBA/2 mice with CLIK148 exacerbated the disease by enhancing an SLA-specific Th2-type response such as IL-4 production. CLIK148 did not exert any direct influence on Leishmania major promastigotes themselves or on the course of L. major infection in SCID mice. Taken together, these findings suggest that treatment of host mice with CLIK148 affects the processing of SLA in APCs, resulting in the potentiation of Th2-type immune responses and thus leading to exacerbation of the disease. Furthermore, endo/lysosomal cathepsin L was found to be functionally distinct from previously described cathepsins B and D.     

Vaccination with recombinant Ascaris suum 24-kilodalton antigen induces a Th1/Th2-mixed type immune response and confers high levels of protection against challenged Ascaris suum lung-stage infection in BALB/c mice

Previous studies have shown that antigens from various life-cycle stages of Ascaris suum can induce host-protective immunity against challenge infections with infective eggs of A. suum. This study evaluated whether Escherichia coli-expressed recombinant 24-kDa antigen from A. suum (rAs24) was a suitable vaccine candidate for the control of Ascaris infections by examining its performance in a mouse model. Immunization of BALB/c mice in three consecutive doses with rAs24 in Freund's Complete Adjuvant (FCA) results in protection against challenge infections as manifested by a 58% reduction (P<0.001) in recovery and stunted development of A. suum lung-stage larvae at day 7 post-challenge. Sera obtained from immune protected mice had a significantly increased level of immunoglobulin G (IgG) (P<0.0001) but had no IgE response. Analysis of IgG-subclass profiles revealed that IgG1 (P<0.0001) showed the greatest increase followed by IgG2b (P<0.005), IgG2a (P<0.006) and IgG3 (P<0.04). Splenic T cells from rAs24-FCA immunized mice secreted significantly high levels of both Th1 cytokine gamma-interferon (P<0.005) and Th2 cytokine interleukin-10 (P<0.001) after stimulation with rAs24 in vitro. Interestingly, affinity purified anti-rAs24 IgG was shown to inhibit moulting of A. suum lung-stage L3 to L4 in vitro by 26%, indicating an in vivo function of the endogenous As24 in the moulting processes. An intense expression of endogenous As24 in the hypodermis and gut epithelium of A. suum lung-stage L3 by immunofluorescence supports a function for endogenous As24. These findings may contribute to the understanding of rAs24-induced Th1/Th2-mediated effector mechanisms required for the protection of A. suum lung-stage larval infection.     

The immune response to ocular herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) is a prevalent microbial pathogen infecting 60% to 90% of the adult world population. The co-evolution of the virus with humans is due, in part, to adaptations that the virus has evolved to aid it in escaping immune surveillance, including the establishment of a latent infection in its human host. A latent infection allows the virus to remain in the host without inducing tissue pathology or eliciting an immune response. During the acute infection or reactivation of latent virus, the immune response is significant, which can ultimately result in corneal blindness or fatal sporadic encephalitis. In fact, HSV-1 is one of the leading causes of infectious corneal blindness in the world as a result of chronic episodes of viral reactivation leading to stromal keratitis and scarring. Significant inroads have been made in identifying key immune mediators that control ocular HSV-1 infection and potentially viral reactivation. Likewise, viral mechanisms associated with immune evasion have also been identified and will be discussed. Lastly, novel therapeutic strategies that are currently under development show promise and will be included in this review. Most investigators have taken full advantage of the murine host as a viable working in vivo model of HSV-1 due to the sensitivity and susceptibility to viral infection, ease of manipulation, and a multitude of developed probes to study changes at the cellular and molecular levels. Therefore, comments in this review will primarily be restricted to those observations pertaining to the mouse model and the assumption (however great) that similar events occur in the human condition.     

Experimental autoimmune myasthenia gravis may occur in the context of a polarized Th1- or Th2-type immune response in rats.

Experimental autoimmune myasthenia gravis (EAMG) is a T cell-dependent, Ab-mediated autoimmune disease induced in rats by a single immunization with acetylcholine receptor (AChR). Although polarized Th1 responses have been shown to be crucial for the development of mouse EAMG, the role of Th cell subsets in rat EAMG is not well established. In the present work we show that while the incidence and severity of EAMG are similar in Lewis (LEW) and Brown-Norway (BN) rats, strong differences are revealed in the immune response generated. Ag-specific lymph node cells from LEW rats produced higher amounts of IL-2 and IFN-gamma than BN lymph node cells, but expressed less IL-4 mRNA. IgG1 and IgG2b anti-AChR isotype predominated in BN and LEW rats, respectively, confirming the dichotomy of the immune response observed between the two strains. Furthermore, although IL-12 administration or IFN-gamma neutralization strongly influenced the Th1/Th2 balance in BN rats, it did not affect the disease outcome. These data demonstrate that a Th1-dominated immune response is not necessarily associated with disease severity in EAMG, not only in rats with disparate MHC haplotype but also in the same rat strain, and suggest that in a situation where complement-fixing Ab can be generated as a consequence of either Th1- or Th2-mediated T cell help, deviation of the immune response will not be an adequate strategy to prevent this Ab-mediated autoimmune disease.     

Madecassoside attenuates inflammatory response on collagen-induced arthritis in DBA/1 mice

Madecassoside (MA), a triterpenoid product isolated from Centella asiatica, has been described to exhibit antioxidant and anti-inflammatory activities. The present study was undertaken to determine whether madecassoside (MA) is efficacious against collagen-induced arthritis (CIA) in mice and its possible mechanisms. DBA/1J mice were immunized with bovine type II collagen and treated with MA (3, 10 and 30 mg/kg d, i.g.) from days 21 to 42 after immunization. Arthritis was evaluated by hind paw swelling, polyarthritis index, and histological examination. In vitro proliferation of spleen cells was examined using 3-[4,5-dimethylthylthiazol-2-yl]-2, 5-diphenyltetrazoliumbromide (MTT) assay. Plasma levels of cytokines tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10) and the expression of prostaglandin E₂ (PGE₂), cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in synovial tissues were also determined. The results showed that comparing with untreated CIA mice, treated with MA dose-dependently suppressed the clinical arthritis score and joints tissues pathological damage, reduced the proliferation of spleen cells, plasma levels of TNF-α and IL-6, synovial tissues PGE₂ production and COX-2 protein expression, however, the expression of COX-1 in symovial tissues did not change and the plasma levels of IL-10 were increased. These results suggest that MA can effectively alleviate inflammatory response on CIA, and anti-inflammatory effects of MA can be attributed, at least partially, to the inhibition of pro-inflammatory mediators, including COX-2 expression, PGE₂ production, TNF-α and IL-6 levels and the up-regulation anti-inflammatory molecule IL-10.     

Retinal ganglion cell degeneration is topological but not cell type specific in DBA/2J mice

Using a variety of double and triple labeling techniques, we have reevaluated the death of retinal neurons in a mouse model of hereditary glaucoma. Cell-specific markers and total neuron counts revealed no cell loss in any retinal neurons other than the ganglion cells. Within the limits of our ability to define cell types, no group of ganglion cells was especially vulnerable or resistant to degeneration. Retrograde labeling and neurofilament staining showed that axonal atrophy, dendritic remodeling, and somal shrinkage (at least of the largest cell types) precedes ganglion cell death in this glaucoma model. Regions of cell death or survival radiated from the optic nerve head in fan-shaped sectors. Collectively, the data suggest axon damage at the optic nerve head as an early lesion, and damage to axon bundles would cause this pattern of degeneration. However, the architecture of the mouse eye seems to preclude a commonly postulated source of mechanical damage within the nerve head.     

DNA vaccines: influenza virus challenge of a Th2/Tc2 immune response results in a Th2/Tc1 response in the lung

For this study, we used DNA-based immunizations to elicit gamma interferon-producing (Tc1) or interleukin 4 (IL-4)-producing (Tc2) CD8 T cells to the influenza virus nucleoprotein. We examined the response of these cells to an intranasal viral challenge. Both the Tc2- and Tc1-biased responses were present in mice with predominantly IL-4-producing (Th2) CD4 T cells. After viral challenge, Tc1 cells underwent more efficient expansion than did Tc2 cells, and only Tc1 cells were detected at the site of infection. In contrast, the CD4 response remained IL-4 biased. However, only a limited number of CD4 cells appeared in the postchallenge lung, and these were strongly enriched for the Th1 phenotype. Thus, the type of memory T-cell response induced by DNA vaccination does not determine the type of response that will predominate at the site of an infection.     

Genetically resistant mice lacking MyD88-adapter protein display a high susceptibility to Leishmania major infection associated with a polarized Th2 response

Host resistance to the intracellular protozoan Leishmania major is highly dependent on IL-12 production by APCs. Genetically resistant C57BL/6 mice develop IL-12-mediated Th1 immune response dominated by IFN-gamma and exhibit only small cutaneous lesions that resolve spontaneously. In contrast, because of several genetic differences, BALB/c mice develop an IL-4-mediated Th2 immune response and a chronic mutilating disease. Myeloid differentiation marker 88 (MyD88) is an adaptator protein that links the IL-1/Toll-like receptor family to IL-1R-associated protein kinase. Toll-like receptors recognize pathogen associated molecular patterns and are crucially implicated in the induction of IL-12 secretion by APC. The role of MyD88 protein in the development of protective immune response against parasites is largely unknown. Following inoculation of L. major, MyD88(-/-) C57BL/6 mice presented large footpad lesions containing numerous infected cells and frequent mutilations. In response to soluble Leishmania Ag, cells from lesion-draining lymph node showed a typical Th2 profile, similar to infected BALB/c mice. IL-12p40 plasma level collapses in infected MyD88(-/-) mice compared with infected wild-type C57BL/6 mice. Importantly, administration of exogenous IL-12 rescues L. major-infected MyD88(-/-) mice, demonstrating that the susceptibility of these mice is a direct consequence of IL-12 deficiency. In conclusion, MyD88-dependent pathways appear essential for the development of the protective IL-12-mediated Th1 response against the Leishmania major parasite. In absence of MyD88 protein, infected mice develop a nonprotective Th2 response.     

轮状病毒致乳鼠肠道外感染Th1/Th2细胞因子变化的研究

目的通过复制轮状病毒（RV）肠道外感染乳鼠的动物模型,检测接种后乳鼠体内Th1/Th2平衡改变,对RV肠道外感染后机体免疫状态进行初步研究。方法48只乳鼠随机均分为3组：肠道外组、肠道内组和正常对照组。肠道外组通过腹腔注射猴RVSA11株,肠道内组灌胃等量RV悬液,对照组无特殊处理。分别在接种后第4天、第8天处死乳鼠,收集标本,观察心、肝、肾、肺等脏器病理变化,用ELISA法检测血清中IL-10和IFN-γ的表达。结果光镜下肠道外组乳鼠肾、肝、肺和脾脏出现病理改变。感染后第4天,肠道内、外组乳鼠血清IFN-γ水平均高于正常组,到第8天明显下降,基本达到基线水平;IL-10在肠道外组第4天增高,到第8天小幅下降,但仍然高于正常组;而肠道内组IL-10无明显改变。结论RV肠道外感染早期呈现Th1-Th2混合反应,而后期则以IL-10的表达为主,T细胞向Th2型免疫应答方向偏离,Th1/Th2细胞因子失衡机制可能是RV肠道外感染的重要因素。     

EMS-induced dominant lethal dose response curve in DBA/1J male mice

An ethyl methanesulfonate (EMS) induced dominant lethal dose response experiment was conducted in strain DBA/1J male mice. Two methods of scoring for dominant lethals, the classic method (dissecting females at mid-pregnancy) and an alternative method (inspection of uterine scars after litters were weaned) were compared. Results indicate that strain DBA/1J has a similar sensitivity to EMS-induced dominant lethals as has been previously reported for other mouse genotypes. Of the two methods used to score dominant lethals, the classic method is more sensitive.