The Shr receptor from Streptococcus pyogenes uses a cap and release mechanism to acquire heme-iron from human hemoglobin.

Streptococcus pyogenes (group A Streptococcus) is a clinically important microbial pathogen that requires iron in order to proliferate. During infections, S. pyogenes uses the surface displayed Shr receptor to capture human hemoglobin (Hb) and acquires its iron-laden heme molecules. Through a poorly understood mechanism, Shr engages Hb via two structurally unique N-terminal Hb-interacting domains (HID1 and HID2) which facilitate heme transfer to proximal NEAr Transporter (NEAT) domains. Based on the results of X-ray crystallography, small angle X-ray scattering, NMR spectroscopy, native mass spectrometry, and heme transfer experiments, we propose that Shr utilizes a "cap and release" mechanism to gather heme from Hb. In the mechanism, Shr uses the HID1 and HID2 modules to preferentially recognize only heme-loaded forms of Hb by contacting the edges of its protoporphyrin rings. Heme transfer is enabled by significant receptor dynamics within the Shr-Hb complex which function to transiently uncap HID1 from the heme bound to Hb's ß subunit, enabling the gated release of its relatively weakly bound heme molecule and subsequent capture by Shr's NEAT domains. These dynamics may maximize the efficiency of heme scavenging by S. pyogenes, enabling it to preferentially recognize and remove heme from only heme-loaded forms of Hb that contain iron.

The Causes of Canine Myocarditis and Myocardial Fibrosis Are Elusive by Targeted Molecular Testing: Retrospective Analysis and Literature Review.

Myocarditis can cause death or permanent heart damage. As epidemiologic and etiopathologic data for canine myocarditis are lacking, we performed a retrospective study using nucleic acid extracted from archived (2007 to 2015) tissues from myocarditis cases and control dogs without myocardial lesions. Heart tissue from pediatric/juvenile and adult dogs was tested with a comprehensive panel of conventional and real-time polymerase chain reaction (PCR) assays targeting recognized agents of canine myocarditis based on a literature review and informed by the comparative epidemiology of human myocarditis. The PCR screen, which included canine parvovirus 2 (CPV-2), canine distemper virus, canine herpesvirus, Borrelia spp, West Nile virus, adenovirus, parainfluenza virus, pneumovirus, respiratory coronavirus, influenza virus, Bartonella spp, Rickettsia spp, Mycoplasma spp, and Neospora caninum, did not detect agents in 35 of 66 cases (53%; 95% confidence interval [CI], 41%-65%) and was frequently negative in adults (21/26); by comparison, agents were not detected in 27 of 57 controls (47%; 95% CI, 35%-60%). Canine distemper virus, herpesvirus, adenovirus, coronavirus, parainfluenza virus, Mycoplasma haemocanis, and N. caninum were occasionally detected in both cases and controls; thus, PCR detection was not considered to indicate causation. We previously reported that CPV-2 continues to be associated with myocarditis in young dogs despite widespread vaccination; in adults, CPV-2 was detected in 2 of 26 cases and 4 of 22 controls. As several agents were similarly detected in cases and controls, it is unclear if these are cardiopathogenic, incidental, or latent. West Nile virus was detected at the analytic limit in 1 adult case. We did not detect Borrelia spp, Bartonella spp, Rickettsia spp, or influenza A virus in the myocarditis cases. These data demonstrate the limitations of current targeted diagnostic tests and the need for additional research to identify unknown agents and develop testing strategies for canine myocarditis.

Parvovirus Infection Is Associated With Myocarditis and Myocardial Fibrosis in Young Dogs.

Perinatal parvoviral infection causes necrotizing myocarditis in puppies, which results in acute high mortality or progressive cardiac injury. While widespread vaccination has dramatically curtailed the epidemic of canine parvoviral myocarditis, we hypothesized that canine parvovirus 2 (CPV-2) myocardial infection is an underrecognized cause of myocarditis, cardiac damage, and/or repair by fibrosis in young dogs. In this retrospective study, DNA was extracted from formalin-fixed, paraffin-embedded tissues from 40 cases and 41 control dogs under 2 years of age from 2007 to 2015. Cases had a diagnosis of myocardial necrosis, inflammation, or fibrosis, while age-matched controls lacked myocardial lesions. Conventional polymerase chain reaction (PCR) and sequencing targeting the VP1 to VP2 region detected CPV-2 in 12 of 40 cases (30%; 95% confidence interval [CI], 18%-45%) and 2 of 41 controls (5%; 95% CI, 0.1%-16%). Detection of CPV-2 DNA in the myocardium was significantly associated with myocardial lesions ( P = .003). Reverse transcription quantitative PCR amplifying VP2 identified viral messenger RNA in 12 of 12 PCR-positive cases and 2 of 2 controls. PCR results were confirmed by in situ hybridization, which identified parvoviral DNA in cardiomyocytes and occasionally macrophages of juvenile and young adult dogs (median age 61 days). Myocardial CPV-2 was identified in juveniles with minimal myocarditis and CPV-2 enteritis, which may indicate a longer window of cardiac susceptibility to myocarditis than previously reported. CPV-2 was also detected in dogs with severe myocardial fibrosis with in situ hybridization signal localized to cardiomyocytes, suggesting prior myocardial damage by CPV-2. Despite the frequency of vaccination, these findings suggest that CPV-2 remains an important cause of myocardial damage in dogs.

Opportunities for targeted therapies: trametinib as a therapeutic approach to canine oral squamous cell carcinomas.

Oral tumors are relatively common in dogs, and canine oral squamous cell carcinoma (COSCC) is the most prevalent oral malignancy of epithelial origin. COSCC is locally aggressive with up to 20% of patients showing regional or distant metastasis at the time of diagnosis. The treatment of choice most typically involves wide surgical excision. Although long-term remission is possible, treatments are associated with significant morbidity and can negatively impact functionality and quality of life. OSCCs have significant upregulation of the RAS-RAF-MEK-MAPK signaling axis, and we had previously hypothesized that small-molecule inhibitors that target RAS signaling might effectively inhibit tumor growth and progression. Here, we demonstrate that the MEK inhibitor trametinib, an FDA-approved drug for human cancers, significantly blocks the growth of several COSCC cell lines established from current patient tumor samples. We further show clinical evidence that the drug is able to cause significant tumor regression in some patients with spontaneously occurring COSCC. Given the limited treatment options available and the high rate of owner rejection of these offered options, these findings provide new hope that more acceptable treatment options may soon enter the veterinary clinic.

Are HIV-negative men who have sex with men and who bareback concerned about HIV infection? Implications for HIV risk reduction interventions.

The emergence of barebacking (intentional unprotected anal intercourse in situations where there is risk of HIV infection) among men who have sex with men (MSM) has been partially attributed to a decrease in HIV-related concerns due to improved anti-retroviral treatment. It is important to understand the level of concern these men have regarding HIV infection because it can affect their interest in risk reduction behaviors as well as their possible engagement in risk reduction interventions. As part of a study on MSM who use the Internet to seek sexual partners, 89 ethnic and racially diverse men who reported never having an HIV-positive test result completed an in-depth qualitative interview and a computer-based quantitative assessment. Of the 82 men who were asked about concerns of HIV infection during the qualitative interviews, 30 expressed "significant concern" about acquiring HIV, 42 expressed "moderate concern," and 10 expressed "minimal concern." Themes that emerged across the different levels of concern were their perceptions of the severity of HIV infection, having friends who were HIV positive, and their own vulnerability to HIV infection. However, these themes differed depending on the level of concern. Among the most frequently mentioned approaches to decrease risk of HIV infection, participants mentioned avoiding HIV-positive sex partners, limiting the number of partners with whom they barebacked, and not allowing partners to ejaculate inside their rectum. Findings suggest that many MSM who bareback would be amenable to HIV prevention efforts that do not depend solely on condom use.

Differential effects of exposure to toxic or nontoxic mold spores on brain inflammation and Morris water maze performance.

People who live or work in moldy buildings often complain of "brain fog" that interferes with cognitive performance. Until recently, there was no published research on the effects of controlled exposure to mold stimuli on cognitive function or an obvious mechanism of action, fueling controversy over these claims. The constellation of health problems reported by mold-exposed individuals (respiratory issues, fatigue, pain, anxiety, depression, and cognitive deficits) correspond to those caused by innate immune activation following exposure to bacterial or viral stimuli. To determine if mold-induced innate immune activation might cause cognitive issues, we quantified the effects of both toxic and nontoxic mold on brain immune activation and spatial memory in the Morris water maze. We intranasally administered either 1) intact, toxic Stachybotrys chartarum spores; 2) ethanol-extracted, nontoxic Stachybotrys chartarum spores; or 3) control saline vehicle to mice. Inhalation of nontoxic spores caused significant deficits in the test of long-term memory of platform location, while not affecting short-term memory. Inhalation of toxic spores increased motivation to reach the platform. Interestingly, in both groups of mold-exposed males, numbers of interleukin-1ß-immunoreactive cells in many areas of the hippocampus significantly correlated with latency to find the platform, path length, and swimming speed during training, but not during testing for long-term memory. These data add to our prior evidence that mold inhalation can interfere with cognitive processing in different ways depending on the task, and that brain inflammation is significantly correlated with changes in behavior.

Human Astrovirus 1-8 Seroprevalence Evaluation in a United States Adult Population.

Human astroviruses are an important cause of viral gastroenteritis globally, yet few studies have investigated the serostatus of adults to establish rates of previous infection. Here, we applied biolayer interferometry immunosorbent assay (BLI-ISA), a recently developed serosurveillance technique, to measure the presence of blood plasma IgG antibodies directed towards the human astrovirus capsid spikes from serotypes 1-8 in a cross-sectional sample of a United States adult population. The seroprevalence rates of IgG antibodies were 73% for human astrovirus serotype 1, 62% for serotype 3, 52% for serotype 4, 29% for serotype 5, 27% for serotype 8, 22% for serotype 2, 8% for serotype 6, and 8% for serotype 7. Notably, seroprevalence rates for capsid spike antigens correlate with neutralizing antibody rates determined previously. This work is the first seroprevalence study evaluating all eight classical human astrovirus serotypes.