Free and complexed-secretory immunoglobulin A triggers distinct intestinal epithelial cell responses.

Secretory immunoglobulin A (SIgA) antibodies play an important role in protecting the mucosal surfaces against pathogens and maintaining homeostasis with the commensal microbiota. Because a substantial portion of the gut microbiota is coated with SIgA, we hypothesized that microbiota-SIgA complexes are important for the maintenance of gut homeostasis. Here we investigated the relationship between microbiota-SIgA complexes and inflammatory epithelial cell responses. We used a multi-cellular three-dimensional (3D) organotypical model of the human intestinal mucosa composed of an intestinal epithelial cell line and primary human lymphocytes/monocytes, endothelial cells and fibroblasts. We also used human SIgA from human colostrum, and a prominent bacterial member of the first colonizers, Escherichia coli, as a surrogate commensal. We found that free and microbiota-complexed SIgA triggered different epithelial responses. While free SIgA up-regulated mucus production, expression of polymeric immunoglobulin receptor (pIgR) and secretion of interleukin-8 and tumoir necrosis factor-α, microbiota-complexed SIgA mitigated these responses. These results suggest that free and complexed SIgA have different functions as immunoregulatory agents in the gut and that an imbalance between the two may affect gut homeostasis.

Generation of specific effector and memory T cells with gut- and secondary lymphoid tissue- homing potential by oral attenuated CVD 909 typhoid vaccine in humans.

Induction of effective memory T cells is likely to be critical to the level and duration of protection elicited by novel live oral typhoid vaccines. Using cells from volunteers who ingested Salmonella Typhi vaccine strain CVD 909, we characterized the induction of interferon (IFN)-gamma-secreting central (T(CM), CD45RO(+)CD62L(+)) and effector (T(EM), CD45RO(+)CD62L(-)) memory T populations, and their gut-homing potential based on integrin alpha4/beta7 expression. Both CD4(+) T(EM) and T(CM) populations secreted IFN-gamma. However, although CD4(+) T(EM) expressed, or not, integrin alpha(4)/beta(7), CD4(+) T(CM) cells were predominantly integrin alpha(4)/beta(7)(+). In contrast, IFN-gamma-secreting CD8(+) cells were predominantly classical T(EM) and CD45RA(+) T(EM) (T(EMRA), CD45RO(-)CD62L(-)) subsets. However, although CD8(+) T(EM) expressed, or not, integrin alpha(4)/beta(7), CD8(+) T(EMRA) were predominantly integrin alpha(4)/beta(7)(+). This is the first demonstration that oral immunization of humans with S. Typhi elicits diverse IFN-gamma-secreting CD4(+) and CD8(+) T(CM) and T(EM) subsets able to migrate to the gut and other lymphoid tissues.

Quantitative analysis of the antiviral activity of CD8(+) T cells from human immunodeficiency virus-positive asymptomatic patients with different rates of CD4(+) T-cell decrease.

We have measured in 22 asymptomatic human immunodeficiency virus type 1-infected patients (10 rapid progressors and 12 slow progressors) the proviral load of CD4(+) T cells homogeneously superinfected by the same dose of a non-syncytium-inducing virus in the presence or in the absence of autologous CD8(+) T cells. We demonstrated that the antiviral activity of CD8(+) T cells was highly predictive of the rate of peripheral CD4(+) T-cell decline.

Lysis of CD4+ T cells expressing HIV-1 gag peptides by gag-specific CD8+ cytotoxic T cells.

The vast majority of in vitro experiments testing the cytotoxic T lymphocytes (CTL) activity in HIV infection has been performed with target cells consisting of autologous EBV-transformed B lymphoblastoid cell lines (B-LCLs) expressing Human immunodeficiency virus type I (HIV-1) proteins. However data concerning the lysis of primary CD4+ T lymphocytes expressing HIV-1 antigens by CTLs is still lacking. To study the CTL activity against such primary targets, we used a system involving PBMCs of an HIV+ asymptomatic patient (PT) as effector cells and the CD4+ lymphocytes or B-LCLs of his healthy HLA-identical twin brother (HTW) as target cells. These syngeneic targets were either infected with recombinant vaccinia virus containing HIV-1 gag gene (gag-vac), or coated with HIV-1 gag peptides. We demonstrate in this study that PT CTLs (which were CD3+, CD4-, CD8+, TCRalphabeta+, TCRgammadelta-, CD56-) specifically lysed both types of syngeneic target cells expressing gag-vac; however, CD4+ T cells expressing HIV gag proteins were lysed less efficiently than B-LCLs expressing the same HIV epitopes. On the other hand, no specific lysis was detected when the target cells were uninfected or infected by wild-type vaccinia virus.

Restoration of immune response by a cationic amphiphilic drug (AY 9944) in vitro: a new approach To chemotherapy against human immunodeficiency virus type 1.

AY 9944 [AY; trans-1,4-bis(chlorobenzylaminomethyl)-cyclohexane dihydrochloride], an inhibitor of sterol synthesis, was found to help restore the normal mitogenic responses and cytokine profiles of peripheral mononuclear cells (PBMCs) from AIDS patients in vitro. Compared to untreated cells, the human immunodeficiency virus type 1 (HIV-1)-infected PBMCs precultured in the presence of AY exhibited a normal rate of either mitogen-induced or recall- and superantigen-induced proliferation. After 2 weeks in the presence of the drug, the percentage of dead CD4(+) cells in HIV-1-infected cultures was comparable to that observed in uninfected cultures, while over the same time interval it increased by three- to fivefold in HIV-1-infected cultures maintained in the absence of AY. AY also stimulated by 2- to 12-fold interleukin-12 (IL-12) and (gamma interferon production. For IL-12, this effect appears to be related to an increase in corresponding IL-12 p35 and IL-12 p40 mRNA levels. Moreover, AY restored the expression of the IL-2 receptor, which was severely impaired in HIV-1-infected PBMCs. Although the drug has no direct antiviral effect (it does not significantly inhibit reverse transcriptase activity measured in vitro), it might be considered a potential therapeutic agent for HIV-infected patients, in that it may correct viral infection-related immune system defects by indirectly enhancing the level of resistance to HIV and opportunistic infections.

Glucocorticoids rescue CD4+ T lymphocytes from activation-induced apoptosis triggered by HIV-1: implications for pathogenesis and therapy.

OBJECTIVE: During HIV-1 infection, CD4+ T lymphocytes migrate to immune-reactive lymphoid organs where they are infected by the virus and/or killed by apoptosis on immunoregulatory stimuli--a potential mechanism underlying fatal CD4+ T-cell depletion observed in AIDS. This study seeks to determine the effects of glucocorticoids (GCC) on the activation-induced T-cell apoptosis triggered by HIV-1. METHODS: CD4+ and CD8+ T cells were purified from HIV-negative donor peripheral blood mononuclear cells (PBMC) by positive selection and exposed to HIV-1 (primary isolates). HIV-1-exposed CD4+ and CD8+ T cells as well as PBMC derived from HIV-1-infected patients were cultured with medium alone or anti-CD3 monoclonal antibodies (MAb)/mitogens in the presence or absence of hydrocortisone or prednisolone. Viral infection kinetics were assessed by polymerase chain reaction and viral replication was measured by p24 enzyme-linked immunosorbent assay. Cell survival, apoptosis, T-cell proliferation, blast cell transformation, and interleukin (IL)-2 receptor (CD25) expression were monitored in parallel for each cell population. RESULTS: Fractionated CD4+ T cells acutely infected by HIV-1 underwent apoptotic death on anti-CD3 MAb/mitogen stimulation. This activation-induced apoptotic cell killing was antagonized by pharmacological doses of prednisolone or hydrocortisone added up to 6 h after stimulation. GCC were also found to be capable of inhibiting the accelerated apoptosis in PBMC (including both CD4+ and CD8+ T-cell fractions) from HIV-1-infected patients. This anti-apoptotic action of GCC overbalanced their downregulatory effect on T-cell proliferation, resulting in an overall improvement of CD4+ T-cell survival in patient PBMC. These effects of GCC were abrogated by the anti-GCC RU 486 and were not associated with significant suppression of CD25 expression and IL-2-dependent T-cell blast transformation; moreover, GCC had no impact on viral infection and replication. CONCLUSION: GCC exert a receptor-mediated anti-apoptotic activity in mature T cells through both activation-induced and HIV-1-triggered pathways and could be potent inhibitors of T-cell apoptosis in HIV-1-infected patients.