Engineered serum markers for non-invasive monitoring of gene expression in the brain.

Measurement of gene expression in the brain requires invasive analysis of brain tissue or non-invasive methods that are limited by low sensitivity. Here we introduce a method for non-invasive, multiplexed, site-specific monitoring of endogenous gene or transgene expression in the brain through engineered reporters called released markers of activity (RMAs). RMAs consist of an easily detectable reporter and a receptor-binding domain that enables transcytosis across the brain endothelium. RMAs are expressed in the brain but exit into the blood, where they can be easily measured. We show that expressing RMAs at a single mouse brain site representing approximately 1% of the brain volume provides up to a 100,000-fold signal increase over the baseline. Expression of RMAs in tens to hundreds of neurons is sufficient for their reliable detection. We demonstrate that chemogenetic activation of cells expressing Fos-responsive RMA increases serum RMA levels >6-fold compared to non-activated controls. RMAs provide a non-invasive method for repeatable, multiplexed monitoring of gene expression in the intact animal brain.

Urea(lly) Got Me: An Uncommon Etiology of Peripartum Liver Failure.

A 23-year-old woman presented 4 days postpartum for agitation and confusion, with initial evaluation consistent with acute fatty liver of pregnancy (AFLP). Later in her course, an amino acid panel was highly suggestive of citrullinemia type 1. She was started on arginine supplementation and glycerol phenylbutyrate and evaluated for a liver transplant. After starting the medication and diet modification, her liver failure resolved, and she was safely discharged. Urea cycle disorders may mimic AFLP with liver enzyme elevation, delirium, and hyperammonemia, but unlike AFLP, patients with urea cycle disorders will typically not recover without dietary modifications and/or medication.

Idiopathic Constrictive Bronchiolitis in an Active Duty Soldier.

Constrictive bronchiolitis is characterized by fibroproliferative thickening of the bronchiolar walls causing narrowing of the bronchiolar lumen, which may progress to the complete obliteration of bronchioles, resulting in progressive dyspnea and ultimately respiratory failure. Active duty service members returning from deployment with toxic exposures such as "burn pits" are known to be at risk for this condition. Other proposed etiologies for this condition include inhalation (nitrogen oxides, ammonia, welding fumes, aerosols [nicotine, diacetyl, and vitamin E acetate]), infection (respiratory syncytial virus, adenovirus, or Mycoplasma pneumoniae), rheumatic diseases, and graft-versus-host disease (lung or hematopoietic cell transplantation). Uncommonly, constrictive bronchiolitis can also be idiopathic. Here we present a case of a young active duty soldier with idiopathic constrictive bronchiolitis without any known risk factors for this disease. The goal of this case presentation is to help the military physician better understand this condition, including identification of this disease process, underlying etiologies, risk factors, and treatments available.

Cloning and characterization of the acidic ribosomal protein P2 of Cryptosporidium parvum, a new 17-kilodalton antigen.

Cryptosporidium infection is commonly observed among children and immunocompromised individuals in developing countries, but large-scale outbreaks of disease among adults have not been reported. In contrast, outbreaks of cryptosporidiosis in the United States and Canada are increasingly common among patients of all ages. Thus, it seems likely that residents of regions where Cryptosporidium is highly endemic acquire some level of immunity, while residents of the developed world do not. A new immunodominant Cryptosporidium parvum antigen in the 15- to 17-kDa size range was identified as the Cryptosporidium parvum 60S acidic ribosomal protein P2 (CpP2). We developed a recombinant protein-based enzyme-linked immunosorbent assay for serologic population surveillance for antibodies that was 89% sensitive and 92% specific relative to the results of the large-format Western blot assay. The human IgG response is directed almost exclusively toward the highly conserved, carboxy-terminal 15 amino acids of the protein. Although IgG antibody cross-reactivity was documented with sera from patients with acute babesiosis, the development of an anti-CpP2 antibody response in our Peru study population correlated better with Cryptosporidium infection than with infection by any other parasitic protozoan. In Haiti, the prevalence of antibodies to CpP2 plateaus at 11 to 20 years of age. Because anti-CpP2 IgG antibodies were found only among residents of countries in the developing world where Cryptosporidium infection occurs early and often, we propose that this response may be a proxy for the intensity of infection and for acquired immunity.

Longitudinal analysis of cryptosporidium species-specific immunoglobulin G antibody responses in Peruvian children.

Cryptosporidium species are ubiquitous in the environment and are frequently detected in the stools of children who live where sanitation conditions are poor. To better characterize the immune response to these parasites, we monitored immunoglobulin G (IgG) antibody levels in a cohort of children from Lima, Peru. Two new enzyme-linked immunosorbent assays based on the C. parvum (bovine, subtype IIa) Iowa strain 17-kDa and 27-kDa antigens were used to measure IgG antibody levels in longitudinal serum samples. Antibody responses were detected during infections with C. parvum, C. felis, and C. meleagridis and with four different subtypes of C. hominis. We also noted that the magnitude of the antibody response was related to the number of previous infections and that older children generally had higher levels of antibodies to the two C. parvum antigens. Antibody responses were not associated with infections with either Cyclospora sp. or Giardia sp. We believe the antibody assays will be important tools for monitoring the success of future public health interventions.

Changes in serum immunoglobulin G levels as a marker for Cryptosporidium sp. infection in Peruvian children.

In a retrospective analysis, we assessed the usefulness of two serologic enzyme-linked immunosorbent assays as epidemiologic tools for the detection of cryptosporidiosis episodes in children from a Peruvian community. The incidence rate determined by the serologic assay was higher than the rate determined by stool microscopy (0.77 versus 0.41 infection/child-year of surveillance).