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The role of T_H1 and T_H2 subsets in human infectious diseases

Enterovirus 71 (EV71) belonging to the Picornaviridae family is considered the most frequently detected causative agent in hand-foot-and-mouth disease (HFMD) and is a serious threat to public health in the Asia-Pacific region. There are currently no approved vaccines or effective drugs for EV71. In this study, using recombinant vesicular stomatitis virus (rVSV) expressing viral VP1 protein (mVP1) of EV71 as a control, we generated two types of rVSVs that can form EV71 virus-like particles (VLPs). First, we co-infected two rVSVs singly expressing P1 (mP1) and 3CD (m3CD) of EV71. Second, we inserted P1 and 3CD into one VSV backbone to generate an rVSV expressing P1 and 3CD together (mP1-3CD). When P1 and 3CD were expressed in the cells either co-infected with mP1 and m3CD (mP1/m3CD) or infected with mP1-3CD, P1 was cleaved by 3CD and produced VP1, VP3, and VP0 to form VLPs. Furthermore, mice immunized with mP1/m3CD or mP1-3CD showed higher humoral and cellular immunity responses than mice immunized with mVP1. Finally, the rVSVs expressing the EV71 proteins were evaluated in mice to determine their potential to protect against a lethal EV71 virus challenge, and among all the rVSVs, the mP1-3CD was shown to be the most promising vaccine candidate for EV71 protection.

Rhodococcus equi, a facultative intracellular pathogen of macrophages, causes life-threatening pneumonia in foals and in people with underlying immune deficiencies. As a basis for this study, we hypothesized that macrophage lineage and age would affect intracellular survival of R. equi and cytokine induction after infection. Monocyte-derived and bronchoalveolar macrophages from 10 adult horses and from 10 foals (sampled at 1–3 days, 2 weeks, 1 month, 3 months, and 5 months of age) were infected ex vivo with virulent R. equi. Intracellular R. equi were quantified and mRNA expression of IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12 p40, IL-18, IFN-γ, and TNF-α was measured. Intracellular replication of R. equi was significantly (P < 0.001) greater in bronchoalveolar than in monocyte-derived macrophages, regardless of age. Regardless of the macrophage lineage, replication of R. equi was significantly (P = 0.002) higher in 3-month-old foals than in 3-day old foals, 2-week-old foals, 1-month-old foals, and adult horses. Expression of IL-4 mRNA was significantly higher in monocyte-derived macrophages whereas expression of IL-6, IL-18, and TNF-α was significantly higher in bronchoalveolar macrophages. Induction of IL-1β, IL-10, IL-12 p40, and IL-8 mRNA in bronchoalveolar macrophages of 1–3-day old foals was significantly higher than in older foals or adult horses. Preferential intracellular survival of R. equi in bronchoalveolar macrophages of juvenile horses may play a role in the pulmonary tropism of the pathogen and in the window of age susceptibility to infection.

CagA protein is the most assessed effecter molecule of Helicobacter pylori. In this report, we demonstrate how CagA protein regulates the functions of dendritic cells (DC) against H. pylori infection. In addition, we found that CagA protein was tyrosine-phosphorylated in DC. The responses to cagA-positive H. pylori in DC were reduced in comparison to those induced by cagA-negative H. pylori. CagA-overexpressing DC also exhibited a decline in the responses against LPS stimulation and the differentiation of CD4⁺ T cells toward Th1 type cells compared to wild type DC. In addition, the level of phosphorylated IRF3 decreased in CagA-overexpressing DC stimulated with LPS, indicating that activated SHP-2 suppressed the enzymatic activity of TBK1 and consequently IRF3 phosphorylation. These data suggest that CagA protein negatively regulates the functions of DC via CagA phosphorylation and that cagA-positive H. pylori strains suppress host immune responses resulting in their chronic colonization of the stomach.

Dehydroepiandrosterone (DHEA) enhances immune responses against a wide range of viral, bacterial, and parasitic pathogens. In a previous study, we reported that administration of DHEA significantly decreased the numbers of blood parasites in Trypanosoma cruzi experimental infection. The present study was undertaken to determine the effectiveness of DHEA in reducing the severity of acute phase T. cruzi infection of male and female Wistar rats. Animals were treated subcutaneously with 40 mg/kg body weight/day of DHEA. The concentration of nitric oxide (NO) was determined in spleen peritoneal cavity. Interleukin-2 (IL-2) and interferon-gamma (IFN-γ) were determined in the sera of uninfected and infected animals. DHEA treatment augments NO production for both sexes after in vitro LPS treatment for uninfected animals. Infection triggered enhanced NO levels although not significant. IL-2 and IFN-γ were detectable in higher concentrations in treated and infected rats of both genders when compared to untreated controls. These data suggest that DHEA may have a potent immunoregulatory function that can affect the course of T. cruzi infection.

In this study we describe for the first time the dynamics of the expression of the cytokines, IL-1β, IL-12p40, TNFα in ovine dendritic cells and macrophages after LPS stimulation. Real time RT–PCR was used for the quantitation of these cytokines and IL-4 and IFNγ as well as two potential housekeeping genes (HKG), ATPase and GAPDH, in mRNAs from ovine leucocyte populations. Both dual-labelled probes (TAMRA/FAM) and SYBR Green assays were utilised, using a Corbett Research RotorGene and ABI 7700 machine. In order to quantitate each cytokine in our assays all C_T values were compared to a standard curve generated using plasmid DNA containing the cytokine of interest. To validate our assays, concanavalin A-stimulated peripheral blood mononuclear cells (PBMCs) and LPS-stimulated monocyte-derived dendritic cells (MoDC) and monocyte-derived macrophages (MDMØ) were examined. We found that peak cytokine mRNA expression was between 3 and 6 h for the cytokines examined except for IL-12p40 where peak cytokine release was around 12 h post-stimulation in MDMØ and PBMCs. However, in MoDCs, peak IL-12p40 mRNA expression was observed within 3–6 h. We have identified a sensitive and reliable method for the identification of ovine cytokine mRNAs.

The susceptibility of thermally injured mice (TI-mice) to various infections is markedly influenced by burn-associated type 2 T cell responses, which are common with severe thermal injuries. Previously, we have reported that CC chemokine ligand 2/monocyte chemoattractant protein-I (CCL2) is produced in mice within 1 day of thermal injury, and the subsequent development of burn-associated type 2 T cell responses are triggered by this chemokine produced early after thermal injury. In this study, influence of norepinephrine (NE) on CCL2 production in mice early after thermal injury (TI) was investigated. Peripheral blood mononuclear cells (PBMC) and peritoneal macrophages (PMφ) from TI-mice produced CCL2, but the same cell preparations from normal mice did not. This chemokine was not produced by PBMC and PMφ from TI-mice previously treated with 6-hydroxydopamine (6-OHDA), which destroys sympathetic nerve termini. NE production was increased in circulation of TI-mice, and treatment of TI-mice with 6-OHDA resulted in the inhibition of NE secretion. When PBMC from normal mice were treated with NE, they acquired the ability to produce CCL2. Splenic T cells from TI-mice produced IL-4 into their culture fluids, while the cytokine was not produced by splenic T cells from TI-mice previously treated with 6-OHDA. These results indicate that NE may have an important role on early CCL2 production and the subsequent development of burn-associated type 2 T cell responses.