No abstract

Since the CD40/CD40 ligand (CD40L) interaction is involved in the regulation of macrophage production of interleukin 12 (IL-12) and T-cell production of gamma interferon (IFN-␥), effector cell functions associated with resistance to Toxoplasma gondii, the role of CD40L in immunity to this parasite was assessed. Infection of C57BL/6 mice with T. gondii results in an upregulation of CD40 expression on accessory cell populations at local sites of infection as well as in lymphoid tissues. Splenocytes from C57BL/6 mice infected with T. gondii for 5 days produced high levels of IL-12 and IFN-␥ when stimulated with toxoplasma lysate antigen, and blocking CD40L did not significantly alter the production of IFN-␥ or IL-12 by these cells. Similar results were observed with splenocytes and mononuclear cells isolated from the brains of chronically infected mice. Interestingly, although CD40L؊/؊ mice infected with T. gondii produced less IL-12 than wild-type mice, they produced comparable levels of IFN-␥ but succumbed to toxoplasmic encephalitis 4 to 5 weeks after infection. The inability of CD40L؊/؊ mice to control parasite replication in the brain correlated with the ability of soluble CD40L, in combination with IFN-␥, to activate macrophages in vitro to control replication of T. gondii. Together, these results identify an important role for the CD40/CD40L interaction in resistance to T. gondii. However, this interaction may be more important in the control of parasite replication in the brain rather than the generation of protective T-cell responses during toxoplasmosis.The induction of a TH1-type immune response is critical for resistance to many intracellular pathogens, including Toxoplasma gondii (10). The events that lead to protective immunity are dependent on the production of interleukin 12 (IL-12), which drives the development of a TH1-type response dominated by the production of gamma interferon (IFN-␥). IFN-␥ is the major mediator of resistance to T. gondii (41) and is required for the activation of effector mechanisms that are essential for control of T. gondii (10). The importance of T cells in resistance to T. gondii is best illustrated by the patients with acquired immune deficiencies who develop toxoplasmic encephalitis (TE). For example, patients with certain cancers, or who are being actively immunosuppressed to allow successful transplantation, are susceptible to reactivation of toxoplasmosis (21, 36). Moreover, patients with AIDS become susceptible to TE as their T-cell counts fall (20), which correlates with a reduction in the levels of IFN-␥ that they can produce (11). The common characteristic of these patients is that they have an acquired defect in their T-cell functions that cripples the ability of the immune system to control T. gondii.Interestingly, a role for the CD40/CD40 ligand (CD40L) interaction in resistance to T. gondii is indicated by the development of TE in pediatric patients with a primary defect in this receptor-ligand interaction (24, 42). However, although the CD40/CD40L interactio...

When chemical or microbial contaminants are assessed for potential effect or possible regulation in ambient and drinking waters, a critical first step is determining if the contaminants occur and if they are at concentrations that may cause human or ecological health concerns. To this end, source and treated drinking water samples from 29 drinking water treatment plants (DWTPs) were analyzed as part of a two-phase study to determine whether chemical and microbial constituents, many of which are considered contaminants of emerging concern, were detectable in the waters. Of the 84 chemicals monitored in the 9 Phase I DWTPs, 27 were detected at least once in the source water, and 21 were detected at least once in treated drinking water. In Phase II, which was a broader and more comprehensive assessment, 247 chemical and microbial analytes were measured in 25 DWTPs, with 148 detected at least once in the source water, and 121 detected at least once in the treated drinking water. The frequency of detection was often related to the analyte's contaminant class, as pharmaceuticals and anthropogenic waste indicators tended to be infrequently detected and more easily removed during treatment, while per and polyfluoroalkyl substances and inorganic constituents were both more frequently detected and, overall, more resistant to treatment. The data collected as part of this project will be used to help inform evaluation of unregulated contaminants in surface water, groundwater, and drinking water.

No abstract

Cryptosporidium is an important waterborne protozoan parasite that can cause severe diarrhea and death in the immunocompromised. The current methods used to monitor for Cryptosporidium oocysts in water are the microscopy-based USEPA methods 1622 and 1623. These methods assess total levels of oocysts in source waters, but do not determine oocyst viability or genotype. Recently, propidium monoazide (PMA) has been used in conjunction with molecular diagnostic tools to identify species and assess the viability of bacteria. The goal of this study was the development of a Cryptosporidium PMA-PCR (CryptoPMA-PCR) assay that includes PMA treatment prior to PCR analysis in order to prevent the amplification of DNA from dead oocysts. The results demonstrated that PMA penetrates only dead oocysts and blocks amplification of their DNA. The CryptoPMA-PCR assay can also specifically detect live oocysts within a mixed population of live and dead oocysts. More importantly, live oocysts, not dead oocysts, were detected in raw waste or surface water samples spiked with Cryptosporidium oocysts. This proof-of-concept study is the first to demonstrate the use of PMA for pre-PCR treatment of Cryptosporidium oocysts. The CryptoPMA-PCR assay is an attractive approach to specifically detect and genotype viable Cryptosporidium oocysts in the water, which is critical for human health risk assessment.