Deregulated MHC class II transactivator expression leads to a strong Th2 bias in CD4+ T lymphocytes.

The MHC class II (MHC-II) transactivator (CIITA) is the master transcriptional regulator of genes involved in MHC-II-restricted Ag presentation. Fine tuning of CIITA gene expression determines the cell type-specific expression of MHC-II genes. This regulation is achieved by the selective usage of multiple CIITA promoters. It has recently been suggested that CIITA also contributes to Th cell differentiation by suppressing IL-4 expression in Th1 cells. In this study, we show that endogenous CIITA is expressed at low levels in activated mouse T cells. Importantly CIITA is not regulated differentially in murine and human Th1 and Th2 cells. Ectopic expression of a CIITA transgene in multiple mouse cell types including T cells, does not interfere with normal development of CD4(+) T cells. However, upon TCR activation the CIITA transgenic CD4(+) T cells preferentially differentiate into IL-4-secreting Th2-type cells. These results imply that CIITA is not a direct Th1-specific repressor of the IL-4 gene and that tight control over the expression of CIITA and MHC-II is required to maintain the normal balance between Th1 and Th2 responses.

Use of abatacept in rheumatoid arthritis.

Abatacept (CTLA-Ig), a modulator of T-lymphocyte activation, has been approved by the Swiss health regulatory agency Swissmedic for the treatment of active rheumatoid arthritis (RA). This article summarises the key trial findings for this biologic agent in RA in different situations such as early erosive rheumatoid arthritis (RA), biologic-naïve RA, RA before and after the use of methotrexate or TNF-inhibitors and includes safety information from these trials. Based on these data, recommendations for clinical practice in Switzerland are made by a panel of experts.

Antiretroviral treatment during pregnancy.

OBJECTIVE: Virologic failure of HIV-positive patients is of special concern during pregnancy. We compared virologic failure and the frequency of treatment changes in pregnant and non-pregnant women of the Swiss HIV Cohort Study. METHODS: Using data on 372 pregnancies in 324 women we describe antiretroviral therapy during pregnancy. Pregnant women on HAART at conception (n = 131) were matched to 228 non-pregnant women (interindividual comparison) and to a time period of equal length before and after pregnancy (intraindividual comparison). Women starting HAART during pregnancy (n = 145) were compared with 578 non-pregnant women starting HAART. FINDINGS: The median age at conception was 31 years, 16% (n = 50) were infected through injecting drug use and the median CD4 cell count was 489 cells/microl. In the majority of pregnancies (n = 220, 59%), women had started ART before conception. When ART was started during pregnancy (n = 145, 39%), it was mainly during the second trimester (n = 100, 69%). Two thirds (n = 26) of 35 women starting in the third trimester were diagnosed with HIV during pregnancy. The risk of virologic failure tended to be lower in pregnant than in non-pregnant women [adjusted odds ratio 0.52 (95% confidence interval 0.25-1.09, P = 0.08)], but was similar in the intraindividual comparison (adjusted odds ratio 1.04, 95% confidence interval 0.48-2.28). Women starting HAART during pregnancy changed the treatment less often than non-pregnant women. CONCLUSION: Despite the physiological changes occurring during pregnancy, HIV infected pregnant women are not at higher risk of virologic failure.

Cutting edge: IL-7 regulates the peripheral pool of adult ROR gamma+ lymphoid tissue inducer cells.

During fetal life, CD4(+)CD3(-) lymphoid tissue inducer (LTi) cells are required for lymph node and Peyer's patch development in mice. In adult animals, CD4(+)CD3(-) cells are found in low numbers in lymphoid organs. Whether adult CD4(+)CD3(-) cells are LTi cells and are generated and maintained through cytokine signals has not been directly addressed. In this study we show that adult CD4(+)CD3(-) cells adoptively transferred into neonatal CXCR5(-/-) mice induced the formation of intestinal lymphoid tissues, demonstrating for the first time their bona fide LTi function. Increasing IL-7 availability in wild-type mice either by IL-7 transgene expression or treatment with IL-7/anti-IL-7 complexes increased adult LTi cell numbers through de novo generation from bone marrow cells and increased the survival and proliferation of LTi cells. Our observations demonstrate that adult CD4(+)lineage(-) cells are LTi cells and that the availability of IL-7 determines the size of the adult LTi cell pool.

CD4 T cells producing pro-inflammatory interleukin-17 mediate high pathology in schistosomiasis

In murine schistosomiasis mansoni, pronounced CD4 T cell-mediated, egg-induced, hepato-intestinal immunopathology and death, whether genetically determined or elicited experimentally, are associated with failure to down-regulate a net pro-inflammatory immune response. Important evidence contributing to this notion comes from the observation that immunization with schistosome egg antigens in CFA (SEA/CFA) causes low pathology C57BL/6 mice to develop an exacerbated form of disease and death in a cytokine milieu characterized by elevated interferon (IFN)-gamma levels. Since such a pro-inflammatory environment presumes a signaling pathway involving interleukin (IL)-12, the SEA/CFA immunization model was used to examine the extent of hepatic immunopathology in the absence of this cytokine. Surprisingly, the IL-12p40 subunit was an absolute requirement for the development of exacerbated disease, whereas the IL-12p35 subunit was not. Moreover, significantly elevated in vitro production of IL-17, but not of IFN-gamma, correlated with the high pathology, and neutralization of IL-17 in vivo resulted in a significant reduction of hepatic inflammation. Our findings clearly demonstrate the pathogenic potential of the novel IL-17-producing T cell subpopulation (ThIL-17), previously shown to mediate chronic inflammation in autoimmune disease. They also imply that IL-23, but not IL-12, is the critical signal necessary to support the pro-inflammatory ThIL-17 subset involved in high pathology schistosomiasis.

Effects of dietary protein type on oxidized cholesterol-induced alteration in age-related modulation of lipid metabolism and indices of immune function in rats.

Exogenous oxidized cholesterol disturbs both lipid metabolism and immune functions. Therefore, it may perturb these modulations with ageing. Effects of the dietary protein type on oxidized cholesterol-induced modulations of age-related changes in lipid metabolism and immune function was examined using differently aged (4 weeks versus 8 months) male Sprague-Dawley rats when casein, soybean protein or milk whey protein isolate (WPI) was the dietary protein source, respectively. The rats were given one of the three proteins in diet containing 0.2% oxidized cholesterols mixture. Soybean protein, as compared with the other two proteins, significantly lowered both the serum thiobarbituric acid reactive substances value and cholesterol, whereas it elevated the ratio of high density lipoprotein-cholesterol/cholesterol in young rats, but not in adult. Moreover, soybean protein, but not casein and WPI, suppressed the elevation of Delta6 desaturation indices of phospholipids in both liver and spleen, particularly in young. On the other hand, WPI, compared to the other two proteins, inhibited the leukotriene B4 production of spleen, irrespective of age. Soybean protein reduced the ratio of CD4(+)/CD8(+) T-cells in splenic lymphocytes. Therefore, the levels of immunoglobulin (Ig)A, IgE and IgG in serum were lowered in rats given soybean protein in both age groups except for IgA in adult, although these observations were not shown in rats given other proteins. Thus, various perturbations of lipid metabolism and immune function caused by oxidized cholesterol were modified depending on the type of dietary protein. The moderation by soybean protein on the change of lipid metabolism seems to be susceptible in young rats whose homeostatic ability is immature. These observations may be exerted through both the promotion of oxidized cholesterol excretion to feces and the change of hormonal release, while WPI may suppress the disturbance of immune function by oxidized cholesterol in both ages. This alleviation may be associated with a large amount of lactoglobulin in WPI. These results thus showed a possibility that oxidized cholesterol-induced perturbations of age-related changes of lipid metabolism and immune function can be moderated by both the selection and combination of dietary protein.

An exogenous mouse mammary tumor virus with properties of Mls-1a (Mtv-7).

The classical minor lymphocyte stimulating (Mls) antigens, which induce a strong primary T cell response in vitro, are closely linked to endogenous copies of mouse mammary tumor viruses (MMTV). Expression of Mls genes leads to clonal deletion of T cell subsets expressing specific T cell receptor (TCR) V beta chains. We describe the isolation and characterization of a new exogenous (infectious) MMTV with biological properties similar to the Mls antigen Mls-1a. In vivo administration of either Mls-1a-expressing B cells or the infectious MMTV (SW) led to an increase of T cells expressing V beta 6 followed by their deletion. Surprisingly, different kinetics of deletion were observed with the exogenous virus depending upon the route of infection. Infection through the mucosa led to a slow deletion of V beta 6+ T cells, whereas deletion was rapid after subcutaneous infection. Sequence analysis of the open reading frames in the 3' long terminal repeat of both this exogenous MMTV (SW) and of Mtv-7 (which is closely linked to Mls-1a) revealed striking similarities, particularly in the COOH terminus, which has been implicated in TCR V beta recognition. The identification of an infectious MMTV with the properties of a strong Mls antigen provides a new, powerful tool to study immunity and tolerance in vivo.

T-cell responses associated with resistance to Leishmania infection in individuals from endemic areas for Leishmania (Viannia) braziliensis

Subclinical or asymptomatic infection is documented in individuals living in endemic areas for leishmaniasis suggesting that the development of an appropriate immune response can control parasite replication and maintain tissue integrity. A low morbidity indicates that intrinsic factors could favor resistance to Leishmania infection. Herein, leishmanial T-cell responses induced in subjects with low susceptibility to leishmaniasis as asymptomatic subjects were compared to those observed in cured cutaneous leishmaniasis (CCL) patients, who controlled the disease after antimonial therapy. All of them have shown maintenance of specific long-term immune responses characterized by expansion of higher proportions of CD4+ as compared to CD8+ Leishmania reactive T-lymphocytes. Asymptomatic subjects had lower indexes of in vitro Leishmania induced lymphoproliferative responses and interferon-gamma (IFN-gamma) production in comparison to CCL patients. On the other hand, interleukin (IL-10) production was much higher in asymptomatics than in CCL, while no differences in IL-5 levels were found. In conclusion, long lived T-cell responses achieved by asymptomatic individuals differed from those who had developed symptomatic leishmaniasis in terms of intensity of lymphocyte activation (proliferation or IFN-gamma) and regulatory mechanisms (IL-10). The absence of the disease in asymptomatics could be explained by their intrinsic ability to create a balance between immunoregulatory (IL-10) and effector cytokines (IFN-gamma), leading to parasite destruction without producing skin tissue damage. The establishment of profiles of cell-mediated immune responses associated with resistance against Leishmania infection is likely to make new inroads into understanding the long-lived immune protection against the disease.

Comparison of the epidemiology, profile of mutations, and clinical response to antiretrovirals among subtypes B and F of the human immunodeficiency virus type 1

The authors compared demographic aspects and profile of mutations in 80 patients with subtypes B and F of human immunodeficiency type 1 (HIV-1). Genotyping of the pol region of the reverse transcriptase was performed using the ViroSeqTM Genotyping System. A total of 61 (76.2%) patients had subtype B and 19 (23.8%) subtype F of the HIV-1. Subtype F tended to be more frequent in heterosexuals and women with a low educational level, but without statistical significance. The frequency of mutations related to nucleoside reverse transcriptase inhibitors and protease inhibitors (PI) was the same in the two subtypes, but mutations related to PI at the codons 63, 77, and 71 were more frequent in subtype B, while mutations at the codons 36 and 20 predominated in subtype F. Sixty-two of the 80 patients infected with subtypes B and F were submitted to antiretroviral therapy for an average of 18-22 months. Undetectable viral loads at the end of follow-up were similar in the two groups, representing 63.8% of subtype B and 73.3% of subtype F (p = 0.715). CD4 lymphocyte counts before and after treatment were similar in the two groups. This study, despite pointing to possible epidemiological and genetic differences among subtypes B and F of HIV-1, suggests that the use of highly active antiretroviral therapy is equally effective against these subtypes.

Targeted expression of human CD1d in transgenic mice reveals independent roles for thymocytes and thymic APCs in positive and negative selection of Valpha14i NKT cells.

CD1d-dependent invariant Valpha14 (Valpha14i) NKT cells are innate T lymphocytes expressing a conserved semi-invariant TCR, consisting, in mice, of the invariant Valpha14-Jalpha18 TCR alpha-chain paired mostly with Vbeta8.2 and Vbeta7. The cellular requirements for thymic positive and negative selection of Valpha14i NKT cells are only partially understood. Therefore, we generated transgenic mice expressing human CD1d (hCD1d) either on thymocytes, mainly CD4+ CD8+ double positive, or on APCs, the cells implicated in the selection of Valpha14i NKT cells. In the absence of the endogenous mouse CD1d (mCD1d), the expression of hCD1d on thymocytes, but not on APCs, was sufficient to select Valpha14i NKT cells that proved functional when activated ex vivo with the Ag alpha-galactosyl ceramide. Valpha14i NKT cells selected by hCD1d on thymocytes, however, attained lower numbers than in control mice and expressed essentially Vbeta8.2. The low number of Vbeta8.2+ Valpha14i NKT cells selected by hCD1d on thymocytes was not reversed by the concomitant expression of mCD1d, which, instead, restored the development of Vbeta7+ Valpha14i NKT cells. Vbeta8.2+, but not Vbeta7+, NKT cell development was impaired in mice expressing both hCD1d on APCs and mCD1d. Taken together, our data reveal that selective CD1d expression by thymocytes is sufficient for positive selection of functional Valpha14i NKT cells and that both thymocytes and APCs may independently mediate negative selection.

IL-4 rapidly produced by V beta 4 V alpha 8 CD4+ T cells instructs Th2 development and susceptibility to Leishmania major in BALB/c mice.

BALB/c mice develop aberrant T helper 2 (Th2) responses and suffer progressive disease after infection with Leishmania major. These outcomes depend on the production of interleukin-4 (IL-4) early after infection. Here we demonstrate that the burst of IL-4 mRNA, peaking in draining lymph nodes of BALB/c mice 16 hr after infection, occurs within CD4+ T cells that express V beta 4 V alpha 8 T cell receptors. In contrast to control and V beta 6-deficient BALB/c mice, V beta 4-deficient BALB/c mice were resistant to infection, demonstrating the role of these cells in Th2 development. The early IL-4 response was absent in these mice, and T helper 1 responses occurred following infection. Recombinant LACK antigen from L. major induced comparable IL-4 production in V beta 4 V alpha 8 CD4+ cells. Thus, the IL-4 required for Th2 development and susceptibility to L. major is produced by a restricted population of V beta 4 V alpha 8 CD4+ T cells after cognate interaction with a single antigen from this complex organism.

Inhibition of mouse mammary tumor virus-induced T cell responses in vivo by antibodies to an open reading frame protein.

Minor lymphocyte stimulating (Mls) antigens specifically stimulate T cell responses that are restricted to particular T cell receptor (TCR) beta chain variable domains. The Mls phenotype is genetically controlled by an open reading frame (orf) located in the 3' long terminal repeat of mouse mammary tumor virus (MMTV); however, the mechanism of action of the orf gene product is unknown. Whereas predicted orf amino acid sequences show strong overall homology, the 20-30 COOH-terminal residues are strikingly polymorphic. This polymorphic region correlates with TCR V beta specificity. We have generated monoclonal antibodies to a synthetic peptide encompassing the 19 COOH-terminal amino acid residues of Mtv-7 orf, which encodes the Mls-1a determinant. We show here that these antibodies block Mls responses in vitro and can interfere specifically with thymic clonal deletion of Mls-1a reactive V beta 6+ T cells in neonatal mice. Furthermore, the antibodies can inhibit V beta 6+ T cell responses in vivo to an infectious MMTV that shares orf sequence homology and TCR specificity with Mtv-7. These results confirm the predicted extracellular localization of the orf COOH terminus and imply that the orf proteins of both endogenous and exogenous MMTV interact directly with TCR V beta.

Calbindin-immunoreactive sensory neurons in dissociated dorsal root ganglion cell cultures of chick embryo: role of culture conditions.

Immunoreactivity to calbindin D-28k, a vitamin D-dependent calcium-binding protein, is expressed by neuronal subpopulations of dorsal root ganglia (DRG) in the chick embryo. To determine whether the expression of this phenotypic characteristic is maintained in vitro and controlled by environmental factors, dissociated DRG cell cultures were performed under various conditions. Subpopulations of DRG cells cultured at embryonic day 10 displayed calbindin-immunoreactive cell bodies and neurites in both neuron-enriched or mixed DRG cell cultures. The number of calbindin-immunoreactive ganglion cells increased up to 7-10 days of culture independently of the changes occurring in the whole neuronal population. The presence of non-neuronal cells, which promotes the maturation of the sensory neurons, tended to reduce the percentage of calbindin-immunoreactive cell bodies. Addition of horse serum enhanced both the number of calbindin-positive neurons and the intensity of the immunostaining, but does not prevent the decline of the subpopulation of calbindin-immunoreactive neurons during the second week of culture; on the contrary, the addition of muscular extract to cultures at 10 days maintained the number of calbindin-expressing neurons. While calbindin-immunoreactive cell bodies grown in culture were small- or medium-sized, no correlation was found between cell size and immunostaining density. At the ultrastructural level, the calbindin immunoreaction was distributed throughout the neuroplasm. These results indicate that the expression of calbindin by sensory neurons grown in vitro may be modulated by horse serum-contained factors or interaction with non-neuronal cells. As distinct from horse serum, muscular extract is able to maintain the expression of calbindin by a subpopulation of DRG cells.

The hope for an HIV vaccine based on induction of CD8+ T lymphocytes: a review

The only long-term and cost-effective solution to the human immunodeficiency virus (HIV) epidemic in the developing world is a vaccine that prevents individuals from becoming infected or, once infected, from passing the virus on to others. There is currently little hope for an AIDS vaccine. Conventional attempts to induce protective antibody and CD8+ lymphocyte responses against HIV and simian immunodeficiency virus (SIV) have failed. The enormous diversity of the virus has only recently been appreciated by vaccinologists, and our assays to determine CD8+ lymphocyte antiviral efficacy are inadequate. The central hypothesis of a CTL-based vaccine is that particularly effective CD8+ lymphocytes directed against at least five epitopes that are derived from regions under functional and structural constraints will control replication of pathogenic SIV. This would be somewhat analogous to control of virus replication by triple drug therapy or neutralizing antibodies.