Changes in survival characteristics of Diplostomum spathaceum cercariae emerged from cadmium-exposed Lymnaea stagnalis

The effect of exposing Lymnaea stagnalis (Gastropoda: Pulmonata), infected with Diplostomum spathaceum (Trematoda: Diplostomatidae), to 100 microg l(-1) cadmium for 7 days on survival characteristics (survival, tail loss, decaudized cercarial life-span) of emerged cercariae was investigated. Exposure of L. stagnalis to cadmium resulted in significantly increased D. spathaceum cercarial survival and an inhibited tail loss compared to controls. The normal parallel relationship which exists over time between decreasing cercarial survival and increasing tail loss in controls was changed in cercariae from cadmium-exposed hosts with an increased proportion of cercarial deaths occurring without tail loss. The decaudized cercarial life-span over the survival period of the cercarial population did not significantly change. However comparisons between individuals decaudized during the initial 24 h time period with those which were decaudized during the final period of cercarial survival showed a significantly altered life span which did not occur in the control population. As a potential indicator of penetration 'fitness' comparisons were also undertaken between control and exposed cercariae decaudized during the initial 24 h time period, which revealed that the decaudized cercarial life-span from the exposed hosts was significantly different from controls. This may have important implications for the ability of cercariae to migrate through the tissues of their target host. The importance and relevance of these results to parasite transmission are discussed.     

Toxicity of cadmium and zinc mixtures to the decaudized cercarial life span of Diplostomum spathaceum

The effects of cadmium and zinc mixtures at concentrations ranging from 0.1 to 10,000 microg l(-1) on the life-span of decaudized cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum (Trematoda: Diplostomatidae) was investigated. Cercariae were exposed to metal mixtures of equal and unequal concentrations, and a low-dose pre-treatment followed by a high-dose exposure mixtures. Metal mixtures demonstrated variable effects on decaudized cercariae either by increasing or reducing their life-span compared to single metal exposures dependent on concentration and the type of mixed metal treatment. Prolonged exposure to equal metal mixtures at low concentrations (0.1-100 microg l(-1)) resulted in a reduction in the life-span of decaudized cercariae at 0.1 and 100 microg l(-1) in those individuals decaudized during the initial 24 h exposure period compared with those decaudized during the final 24 h period of cercarial survival, whilst in controls there was no significant life-span change between the two time periods. Decaudized cercariae which were exposed to low concentrations (0.1-100 microg l(-1)) of equal metal mixtures were also evaluated for their role as an indicator of larval 'fitness' for migrating through the tissues of their target fish host for those individuals decaudized during the initial 24 h exposure period, and demonstrated only a limited change in their life-span compared to control and single metal exposures. The importance of metal mixtures in parasite establishment in the fish host is discussed.     

A synthetic TLR4 antagonist has anti-inflammatory effects in two murine models of inflammatory bowel disease

Current evidence indicates that the chronic inflammation observed in the intestines of patients with inflammatory bowel disease is due to an aberrant immune response to enteric flora. We have developed a lipid A-mimetic, CRX-526, which has antagonistic activity for TLR4 and can block the interaction of LPS with the immune system. CRX-526 can prevent the expression of proinflammatory genes stimulated by LPS in vitro. This antagonist activity of CRX-526 is directly related to its structure, particularly secondary fatty acyl chain length. In vivo, CRX-526 treatment blocks the ability of LPS to induce TNF-alpha release. Importantly, treatment with CRX-526 inhibits the development of moderate-to-severe disease in two mouse models of colonic inflammation: the dextran sodium sulfate model and multidrug resistance gene 1a-deficient mice. By blocking the interaction between enteric bacteria and the innate immune system, CRX-526 may be an effective therapeutic molecule for inflammatory bowel disease.     

Differentiation to the CCR2+ inflammatory phenotype in vivo is a constitutive, time-limited property of blood monocytes and is independent of local inflammatory mediators

It is proposed that CCR2+ monocytes are specifically recruited to inflammatory sites, whereas CCR2- monocytes are recruited to normal tissue to become resident macrophages. Whether these subsets represent separate lineages, how differential trafficking is regulated and whether monocytes undergo further differentiation is uncertain. Using a mouse model of autoimmune uveoretinitis we examined monocyte trafficking to the inflamed retina in vivo. We show that bone marrow-derived CD11b+ F4/80- monocytes require 24 to 48 h within the circulation and lymphoid system before acquiring the CCR2+ phenotype and trafficking to the inflamed retina is enabled. This phenotype, and the capacity to traffic were lost by 72 h. Monocyte CCR2 expression followed a similar time course in normal mice indicating that differentiation to an inflammatory phenotype is a constitutive, time-limited property, independent of local inflammatory mediators. Phenotypic analysis of adoptively transferred cells indicated that circulating inflammatory monocytes also differentiate into CD11c+ and B220+ dendritic cells and F4/80+ tissue macrophages in vivo. Our data supports the hypothesis of continuous extravasation and progressive differentiation over time of inflammatory monocytes in the circulation rather than replication within the actively inflamed tissue, and supports the concept of myeloid dendritic cell differentiation from trafficking monocytes under physiological conditions in vivo.     

Subunit exchange by CheA histidine kinases from the mesophile Escherichia coli and the thermophile Thermotoga maritima

Dimerization of the chemotaxis histidine kinase CheA is required for intersubunit autophosphorylation [Swanson, R. V., Bourret, R. B., and Simon, M. I. (1993) Mol. Microbiol. 8, 435-441]. Here we show that CheA dimers exchange subunits by the rate-limiting dissociation of a central four-helix bundle association domain (P3), despite the high stability of P3 versus unfolding. P3 alone determines the stability and exchange properties of the CheA dimer. For CheA proteins from the mesophile Escherichia coli and the thermophile Thermotoga maritima, subunit dissociation activates at temperatures where the respective organisms live (37 and 80 degrees C). Under destabilizing conditions, P3 dimer dissociation is cooperative with unfolding. Chemical denaturation is reversible for both EP3 and TP3. Aggregation accompanies thermal unfolding for both proteins under most conditions, but thermal unfolding is reversible and two-state for EP3 at low protein concentrations. Residue differences within interhelical loops may account for the contrasted thermodynamic properties of structurally similar EP3 and TP3 (41% sequence identity). Under stabilizing conditions, greater correlation between activation energy for dimer dissociation and P3 stability suggests more unfolding in the dissociation of EP3 than TP3. Furthermore, destabilization of extended conformations by glycerol slows relative dissociation rates more for EP3 than for TP3. Nevertheless, at physiological temperatures, neither protein likely unfolds completely during subunit exchange. EP3 and TP3 will not exchange subunits with each other. The receptor coupling protein CheW reduces the subunit dissociation rate of the T. maritima CheA dimer by interacting with the regulatory domain P5.     

Influence of cadmium exposure on the incidence of first intermediate host encystment by Echinoparyphium recurvatum cercariae in Lymnaea peregra

The effect of cadmium exposure of the snail first intermediate host Lymnaea peregra on the incidence of encystment of Echinoparyphium recurvatum (Digenea: Echinostomatidae) cercariae without emergence from the snail was investigated. Exposure to 100 microg l(-1) Cd for 72 h caused a significant increase in the incidence of first host encystment when compared to controls. In addition, autometallographic staining of E. recurvatum daughter rediae and developing cercariae showed that there was metal accumulation within their body tissues. The significance of these findings to parasite transmission in metal-polluted environments is discussed.     

No Increase in Hepatitis B Virus (HBV)-Specific CD8+ T Cells in Patients with HIV-1-HBV Coinfections following HBV-Active Highly Active Antiretroviral Therapy

Following treatment of hepatitis B virus (HBV) monoinfection, HBV-specific T-cell responses increase significantly; however, little is known about the recovery of HBV-specific T-cell responses following HBV-active highly active antiretroviral therapy (HAART) in HIV-HBV coinfected patients. HIV-HBV coinfected patients who were treatment naïve and initiating HBV-active HAART were recruited as part of a prospective cohort study in Thailand and followed for 48 weeks (n = 24). Production of gamma interferon (IFN-γ) and tumor necrosis factor α (TNF-α) in both HBV- and HIV-specific CD8⁺ T cells was quantified using intracellular cytokine staining on whole blood. Following HBV-active HAART, the median (interquartile range) log decline from week 0 to week 48 for HBV DNA was 5.8 log (range, 3.4 to 6.7) IU/ml, and for HIV RNA it was 3.1 (range, 2.9 to 3.5) log copies/ml (P < 0.001 for both). The frequency of HIV Gag-specific CD8⁺ T-cell responses significantly decreased (IFN-γ, P < 0.001; TNF-α, P = 0.05). In contrast, there was no significant change in the frequency (IFN-γ, P = 0.21; TNF-α, P = 0.61; and IFN-γ and TNF-α, P = 0.11) or magnitude (IFN-γ, P = 0.13; TNF-α, P = 0.13; and IFN-γ and TNF-α, P = 0.13) of HBV-specific CD8⁺ T-cell responses over 48 weeks of HBV-active HAART. Of the 14 individuals who were HBV e antigen (HBeAg) positive, 5/14 (36%) lost HBeAg during the 48 weeks of follow-up. HBV-specific CD8⁺ T cells were detected in 4/5 (80%) of patients prior to HBeAg loss. Results from this study show no sustained change in the HBV-specific CD8⁺ T-cell response following HBV-active HAART. These findings may have implications for the duration of treatment of HBV in HIV-HBV coinfected patients, particularly in HBeAg-positive disease.Individuals infected with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are at increased risk of liver disease progression and liver-related mortality (35). Despite the introduction of effective highly active antiretroviral therapy (HAART), liver disease remains a major cause of non-AIDS-related deaths in HIV-1-infected patients (31). Current guidelines recommend the early consideration of HBV-active HAART in the majority of coinfected individuals (28), and treatment of both HBV and HIV is generally lifelong. This is in contrast to HBV-monoinfected patients, where HBV treatment ceases following production of antibody to HBV e antigen (HBeAg) or HBV surface antigen (HBsAg) (23). HBeAg and HBsAg seroconversions are considered important endpoints of treatment as they are associated with HBV DNA clearance, normalization of alanine aminotransferase (ALT), and a reduction in the risk of liver disease (12).Little is known about the immune events precipitating HBeAg or HBsAg seroconversion. However, a reduction in antigen burden following anti-HBV treatment may reduce T-cell tolerance and exhaustion, allowing for a more efficient HBV-specific T-cell and B-cell immune response against either HBeAg and/or HBsAg (11, 13, 21). Circulating HBV-specific CD4⁺ and CD8⁺ T cells are rarely detected in untreated chronic HBV infection (5, 24). Following treatment of HBV monoinfection with nucleos(t)ide analogues such as lamivudine (LMV), there is an increase in functional HBV-specific CD4⁺ and CD8⁺ T cells both in the peripheral blood (5, 18) and within the liver (32). However, recovery of HBV-specific T cells appears to be transient and has been shown to decline following long-term therapy (5, 14, 20).We have previously shown that the HBV-specific T-cell response is impaired in HIV-HBV coinfection (7, 9). In one small observational study (n = 5), HBV-active HAART was associated with the recovery of CD8⁺ HBV-specific T cells (19); however, in this study, two patients had received prior HAART, and the HBV-specific T-cell responses were examined only during the first 24 weeks of treatment (19). In addition, HBeAg status was not defined, and HBV-specific T-cell responses were measured only by IFN-γ production following stimulation with HLA-A2-restricted epitopes (19).In the present study, we used an overlapping peptide library covering the complete HBV genome to assess change in HBV-specific CD8⁺ T cells following the introduction of HBV-active HAART in treatment-naïve HIV-HBV-coinfected patients in Thailand. Overall, we show that there was no sustained change in the magnitude, frequency, or quality of HBV-specific T-cell responses following initiation of effective HBV-active HAART.