Evidence for Finely-Regulated Asynchronous Growth of Toxoplasma gondii Cysts Based on Data-Driven Model Selection

Toxoplasma gondii establishes a chronic infection by forming cysts preferentially in the brain. This chronic infection is one of the most common parasitic infections in humans and can be reactivated to develop life-threatening toxoplasmic encephalitis in immunocompromised patients. Host-pathogen interactions during the chronic infection include growth of the cysts and their removal by both natural rupture and elimination by the immune system. Analyzing these interactions is important for understanding the pathogenesis of this common infection. We developed a differential equation framework of cyst growth and employed Akaike Information Criteria (AIC) to determine the growth and removal functions that best describe the distribution of cyst sizes measured from the brains of chronically infected mice. The AIC strongly support models in which T. gondii cysts grow at a constant rate such that the per capita growth rate of the parasite is inversely proportional to the number of parasites within a cyst, suggesting finely-regulated asynchronous replication of the parasites. Our analyses were also able to reject the models where cyst removal rate increases linearly or quadratically in association with increase in cyst size. The modeling and analysis framework may provide a useful tool for understanding the pathogenesis of infections with other cyst producing parasites

Dual Antibiotic Therapy with Vancomycin and Cefazolin for Surgical Prophylaxis in Total Knee Arthroplasty

Background: Perioperative administration of intravenous antibiotics is a routine part of total knee arthroplasty.  Antibiotic selection is a matter of controversy, and the potential risks and benefits associated with each antibiotic selection need to be considered.  The objective of this study is to examine the effects of routine dual antibiotic prophylaxis with both cefazolin and vancomycin on infection and renal failure after primary total knee arthroplasty (TKA) compared with cefazolin alone. Methods: We performed a retrospective review of primary TKA patients for two years before and two years after routine dual antibiotic prophylaxis was implemented at our institution. 1502 patients were included (567 cefazolin-only and 935 dual prophylaxis).   Results: 2 patients (0.4%) in the cefazolin-only group had a deep surgical site infection, compared with 13 patients (1.4%) in the dual prophylaxis group (p=0.06). 46 patients (8.1%) in the cefazolin-only group had postoperative renal failure, compared with 36 patients (3.9%) in the dual prophylaxis group (p=0.0006). Discussion and Conclusion: Our results did not support the routine use of vancomycin in primary total joint arthroplasty to decrease periprosthetic joint infection. However, we also did not see any clear harm due to renal failure in the routine use of dual antibiotic prophylaxis

VCAM-1/α4β1 Integrin Interaction is Crucial for Prompt Recruitment of Immune T Cells into the Brain During the Early Stage of Reactivation of Chronic Infection with \u3cem\u3eToxoplasma gondii\u3c/em\u3e to Prevent Toxoplasmic Encephalitis

Reactivation of chronic infection with Toxoplasma gondii can cause life-threatening toxoplasmic encephalitis in immunocompromised individuals. We examined the role of VCAM-1/α4β1 integrin interaction in T cell recruitment to prevent reactivation of the infection in the brain. SCID mice were infected and treated with sulfadiazine to establish a chronic infection. VCAM-1 and ICAM-1 were the endothelial adhesion molecules detected on cerebral vessels of the infected SCID and wild-type animals. Immune T cells from infected wild-type mice were treated with anti-α4 integrin or control antibodies and transferred into infected SCID or nude mice, and the animals received the same antibody every other day. Three days later, sulfadiazine was discontinued to initiate reactivation of infection. Expression of mRNAs for CD3δ, CD4, CD8β, gamma interferon (IFN-γ), and inducible nitric oxide synthase (NOS2) (an effector molecule to inhibit T. gondii growth) and the numbers of CD4+ and CD8+ T cells in the brain were significantly less in mice treated with anti-α4 integrin antibody than in those treated with control antibody at 3 days after sulfadiazine discontinuation. At 6 days after sulfadiazine discontinuation, cerebral tachyzoite-specific SAG1 mRNA levels and numbers of inflammatory foci associated with tachyzoites were markedly greater in anti-α4 integrin antibody-treated than in control antibody-treated animals, even though IFN-γ and NOS2 mRNA levels were higher in the former than in the latter. These results indicate that VCAM-1/α4β1 integrin interaction is crucial for prompt recruitment of immune T cells and induction of IFN-γ-mediated protective immune responses during the early stage of reactivation of chronic T. gondii infection to control tachyzoite growth

Targeting GNE myopathy: A dual prodrug approach for the delivery of N-acetylmannosamine 6-phosphate

ProTides comprise an important class of prodrugs currently marketed and developed as antiviral and anticancer therapies. The ProTide technology employs phosphate masking groups capable of providing more favorable druglike properties and an intracellular activation mechanism for enzyme-mediated release of a nucleoside monophosphate. Herein, we describe the application of phosphoramidate chemistry to 1,3,4-O-acetylated N-acetylmannosamine (Ac3ManNAc) to deliver ManNAc-6-phosphate (ManNAc-6-P), a critical intermediate in sialic acid biosynthesis. Sialic acid deficiency is a hallmark of GNE myopathy, a rare congenital disorder of glycosylation (CDG) caused by mutations in GNE that limit the production of ManNAc-6-P. Synthetic methods were developed to provide a library of Ac3ManNAc-6-phosphoramidates that were evaluated in a series of studies for their potential as a treatment for GNE myopathy. Prodrug 12b showed rapid activation in a carboxylesterase (CPY) enzymatic assay and favorable ADME properties, while also being more effective than ManNAc at increasing sialic acid levels in GNE-deficient cell lines. These results provide a potential platform to address substrate deficiencies in GNE myopathy and other CDGs

Targeting GNE myopathy: A dual prodrug approach for the delivery of N-acetylmannosamine 6-phosphate

ProTides comprise an important class of prodrugs currently marketed and developed as antiviral and anticancer therapies. The ProTide technology employs phosphate masking groups capable of providing more favorable druglike properties and an intracellular activation mechanism for enzyme-mediated release of a nucleoside monophosphate. Herein, we describe the application of phosphoramidate chemistry to 1,3,4-O-acetylated N-acetylmannosamine (Ac3ManNAc) to deliver ManNAc-6-phosphate (ManNAc-6-P), a critical intermediate in sialic acid biosynthesis. Sialic acid deficiency is a hallmark of GNE myopathy, a rare congenital disorder of glycosylation (CDG) caused by mutations in GNE that limit the production of ManNAc-6-P. Synthetic methods were developed to provide a library of Ac3ManNAc-6-phosphoramidates that were evaluated in a series of studies for their potential as a treatment for GNE myopathy. Prodrug 12b showed rapid activation in a carboxylesterase (CPY) enzymatic assay and favorable ADME properties, while also being more effective than ManNAc at increasing sialic acid levels in GNE-deficient cell lines. These results provide a potential platform to address substrate deficiencies in GNE myopathy and other CDGs

Schematic life cycle of <i>T. gondii</i>.

<p>Schematic life cycle of <i>T. gondii</i>.</p

Schematic representations of the growth (left) and removal (right) functions.

<p>Schematic representations of the growth (left) and removal (right) functions.</p

Model selection results.

<p>The AIC is calculated using , where is the number of parameters and is the maximum likelihood for the model. Models 1–8 correspond to a constant growth function. Models 9–16 correspond to a linear growth function. Models 17–24 correspond to a logistic growth function. The removal functions in models 4, 12, and 20 are known as the one-parameter type II function. The removal functions in models 5, 13, and 21 are known as the one-parameter type III function. The removal functions in models 7, 15, and 23 are known as the two-parameter type II function. The removal functions in models 8, 16, and 24 are known as the two-parameter type III function. See <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003283#pcbi-1003283-g006" target="_blank">Figure 6</a> for schematic representations of different growth and removal functions. For models 1–5 and models 9–13, and the parameter is . For models 6–8 and models 14–16, and the parameters are and . For models 17–21, and the parameters are and . For models 22–24, and the parameters are , , and .</p

Chronic infection diagram of cyst-volume distribution model.

<p>Parasites infect healthy cells and begin replicating, causing the volume of the cyst to increase. The parasites burst at some rate and release new parasites into the system which are capable of infecting new healthy cells.</p