The salt-sensitive structure and zinc inhibition of Borrelia burgdorferi protease BbHtrA.

HtrA serine proteases are highly conserved and essential ATP-independent proteases with chaperone activity. Bacteria express a variable number of HtrA homologues that contribute to the virulence and pathogenicity of bacterial pathogens. Lyme disease spirochetes possess a single HtrA protease homologue, Borrelia burgdorferi HtrA (BbHtrA). Previous studies established that, like the human orthologue HtrA1, BbHtrA is proteolytically active against numerous extracellular proteins in vitro. In this study, we utilized size exclusion chromatography and blue native polyacrylamide gel electrophoresis (BN-PAGE) to demonstrate BbHtrA oligomeric structures that were substrate independent and salt sensitive. Examination of the influence of transition metals on the activity of BbHtrA revealed that this protease is inhibited by Zn(2+) > Cu(2+) > Mn(2+). Extending this analysis to two other HtrA proteases, E. coli DegP and HtrA1, revealed that all three HtrA proteases were reversibly inhibited by ZnCl2 at all micro molar concentrations examined. Commercial inhibitors for HtrA proteases are not available and physiologic HtrA inhibitors are unknown. Our observation of conserved zinc inhibition of HtrA proteases will facilitate structural and functional studies of additional members of this important class of proteases.

In vitro growth, cytopathic effects and clearance of monolayers by clinical isolates of Balamuthia mandrillaris in human skin cell cultures.

Balamuthia mandrillaris is a free-living ameba (FLA) that has been isolated or its DNA identified in soil, dust and water. It causes a fatal central nervous system infection in humans and animals. Although it is environmental as Acanthamoeba and Naegleria fowleri, the two other free-living amebae that also cause CNS infections in humans and other animals, Balamuthia does not feed on bacteria as the other FLA. In the laboratory, it can be grown on a variety of mammalian cell cultures. In this study we examined the ability of three different Balamuthia isolates to grow on several different human skin cell cultures including the WT/A keratinocyte cell cultures. A corneal isolate of Acanthamoeba castellanii was used for comparison.

Comparison of Zika virus inactivation methods for reagent production and disinfection methods.

Zika virus (ZIKV) infection remains a public health concern necessitating demand for long-term virus production for diagnostic assays and R&D activities. Inactivated virus constitutes an important component of the Trioplex rRT-PCR assay and serological IgM assay (MAC-ELISA). The aim of our study is to establish standard methods of ZIKV inactivation while maintaining antigenicity and RNA integrity. We tested viral supernatants by four different inactivation methods: 1. Heat inactivation at 56 °C and 60 °C; 2. Gamma-Irradiation; 3. Chemical inactivation by Beta-propiolactone (BPL) and 4. Fast-acting commercial disinfecting agents. Effectivity was measured by cytopathic effect (CPE) and plaque assay. RNA stability and antigenicity were measured by RT-PCR and MAC-ELISA, respectively. Results: Heat inactivation: Low titer samples, incubated at 56 °C for 2 h, showed neither CPE or plaques compared to high titer supernatants that required 2.5 h. Inactivation occurred at 60 °C for 60 min with all virus titers. Gamma irradiation: Samples irradiated at ≥3 Mrad for low virus concentrations and ≥5Mrad for high virus titer completely inactivated virus. Chemical Inactivation: Neither CPE nor plaques were observed with ≥0.045 % BPL inactivation of ZIKV. Disinfectant: Treatment of viral supernatants with Micro-Chem Plus™, inactivated virus in 2 min, whereas, Ethanol (70 %) and STERIS Coverage® Spray TB inactivated the virus in 5 min.

High-throughput quantitation of SARS-CoV-2 antibodies in a single-dilution homogeneous assay.

SARS-CoV-2 emerged in late 2019 and has since spread around the world, causing a pandemic of the respiratory disease COVID-19. Detecting antibodies against the virus is an essential tool for tracking infections and developing vaccines. Such tests, primarily utilizing the enzyme-linked immunosorbent assay (ELISA) principle, can be either qualitative (reporting positive/negative results) or quantitative (reporting a value representing the quantity of specific antibodies). Quantitation is vital for determining stability or decline of antibody titers in convalescence, efficacy of different vaccination regimens, and detection of asymptomatic infections. Quantitation typically requires two-step ELISA testing, in which samples are first screened in a qualitative assay and positive samples are subsequently analyzed as a dilution series. To overcome the throughput limitations of this approach, we developed a simpler and faster system that is highly automatable and achieves quantitation in a single-dilution screening format with sensitivity and specificity comparable to those of ELISA.

Rapid development of neutralizing and diagnostic SARS-COV-2 mouse monoclonal antibodies.

The need for high-affinity, SARS-CoV-2-specific monoclonal antibodies (mAbs) is critical in the face of the global COVID-19 pandemic, as such reagents can have important diagnostic, research, and therapeutic applications. Of greatest interest is the ~ 300 amino acid receptor binding domain (RBD) within the S1 subunit of the spike protein because of its key interaction with the human angiotensin converting enzyme 2 (hACE2) receptor present on many cell types, especially lung epithelial cells. We report here the development and functional characterization of 29 nM-affinity mouse SARS-CoV-2 mAbs created by an accelerated immunization and hybridoma screening process. Differing functions, including binding of diverse protein epitopes, viral neutralization, impact on RBD-hACE2 binding, and immunohistochemical staining of infected lung tissue, were correlated with variable gene usage and sequence.

Analysis of the initial lot of the CDC 2019-Novel Coronavirus (2019-nCoV) real-time RT-PCR diagnostic panel.

At the start of the COVID-19 pandemic, the Centers for Disease Control and Prevention (CDC) designed, manufactured, and distributed the CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel for SARS-CoV-2 detection. The diagnostic panel targeted three viral nucleocapsid gene loci (N1, N2, and N3 primers and probes) to maximize sensitivity and to provide redundancy for virus detection if mutations occurred. After the first distribution of the diagnostic panel, state public health laboratories reported fluorescent signal in the absence of viral template (false-positive reactivity) for the N3 component and to a lesser extent for N1. This report describes the findings of an internal investigation conducted by the CDC to identify the cause(s) of the N1 and N3 false-positive reactivity. For N1, results demonstrate that contamination with a synthetic template, that occurred while the "bulk" manufactured materials were located in a research lab for quality assessment, was the cause of false reactivity in the first lot. Base pairing between the 3' end of the N3 probe and the 3' end of the N3 reverse primer led to amplification of duplex and larger molecules resulting in false reactivity in the N3 assay component. We conclude that flaws in both assay design and handling of the "bulk" material, caused the problems with the first lot of the 2019-nCoV Real-Time RT-PCR Diagnostic Panel. In addition, within this study, we found that the age of the examined diagnostic panel reagents increases the frequency of false positive results for N3. We discuss these findings in the context of improvements to quality control, quality assurance, and assay validation practices that have since been improved at the CDC.

Red blood cells are the major source of alpha-synuclein in blood.

BACKGROUND: Alpha-synuclein has been directly linked to Parkinson's disease etiology by mutations in and multiplication of its gene that result in a familial form of Parkinson's disease. Alpha-synuclein has been detected in blood, and was found to be elevated in the blood of those individuals with the alpha-synuclein gene multiplication. OBJECTIVE: A complete analysis of the level of alpha-synuclein in blood has not been performed. In this report, we determine the quantitative distribution of alpha-synuclein in the plasma and different cellular fractions of human blood. The levels of alpha-synuclein in human and mouse blood are compared. METHODS: Alpha-synuclein levels in the different fractions of blood were quantified by a sandwich ELISA with purified recombinant alpha-synuclein as an assay standard. Samples were further characterized by Western immunoblot analysis. RESULTS: More than 99% of the alpha-synuclein resides in the red blood cells (RBCs) with less than 1% of the total detected in the plasma, platelets and peripheral blood mononuclear cells. CONCLUSIONS: More than 99% of the alpha-synuclein in human blood is present in the peripheral blood cells, with the remainder in plasma. Fractionation of peripheral blood cells from human blood and quantification of alpha-synuclein revealed that only a very small amount of the total alpha-synuclein is present in peripheral blood mononuclear cells, and platelets, with the majority of alpha-synuclein in blood being present in RBCs. Considering the abundance and fragility of RBCs, alpha-synuclein levels in these other blood fractions or other bodily fluids such as cerebrospinal fluid may be artificially elevated by contamination with intact or lysed RBCs.

Novel graphene-based biosensor for early detection of Zika virus infection.

We have developed a cost-effective and portable graphene-enabled biosensor to detect Zika virus with a highly specific immobilized monoclonal antibody. Field Effect Biosensing (FEB) with monoclonal antibodies covalently linked to graphene enables real-time, quantitative detection of native Zika viral (ZIKV) antigens. The percent change in capacitance in response to doses of antigen (ZIKV NS1) coincides with levels of clinical significance with detection of antigen in buffer at concentrations as low as 450pM. Potential diagnostic applications were demonstrated by measuring Zika antigen in a simulated human serum. Selectivity was validated using Japanese Encephalitis NS1, a homologous and potentially cross-reactive viral antigen. Further, the graphene platform can simultaneously provide the advanced quantitative data of nonclinical biophysical kinetics tools, making it adaptable to both clinical research and possible diagnostic applications. The speed, sensitivity, and selectivity of this first-of-its-kind graphene-enabled Zika biosensor make it an ideal candidate for development as a medical diagnostic test.

Conserved C-terminal charge exerts a profound influence on the aggregation rate of α-synuclein.

α-Synuclein (α-syn) is the major component of filamentous Lewy bodies found in the brains of patients diagnosed with Parkinson's disease (PD). Recent studies demonstrate that, in addition to the wild-type sequence, α-syn is found in several modified forms, including truncated and phosphorylated species. Although the mechanism by which the neuronal loss in PD occurs is unknown, aggregation and fibril formation of α-syn are considered to be key pathological features. In this study, we analyze the rates of fibril formation and the monomer-fibril equilibrium for eight disease-associated truncated and phosphorylated α-syn variants. Comparison of the relative rates of aggregation reveals a strong monotonic relationship between the C-terminal charge of α-syn and the lag time prior to the observation of fibril formation, with truncated species exhibiting the fastest aggregation rates. Moreover, we find that a decrease in C-terminal charge shifts the equilibrium to favor the fibrillar species. An analysis of these findings in the context of linear growth theories suggests that the loss of the charge-mediated stabilization of the soluble state is responsible for the enhanced aggregation rate and increased extent of fibril fraction. Therefore, C-terminal charge is kinetically and thermodynamically protective against α-syn polymerization and may provide a target for the treatment of PD.

Polo-like kinase 2 (PLK2) phosphorylates alpha-synuclein at serine 129 in central nervous system.

Several neurological diseases, including Parkinson disease and dementia with Lewy bodies, are characterized by the accumulation of alpha-synuclein phosphorylated at Ser-129 (p-Ser-129). The kinase or kinases responsible for this phosphorylation have been the subject of intense investigation. Here we submit evidence that polo-like kinase 2 (PLK2, also known as serum-inducible kinase or SNK) is a principle contributor to alpha-synuclein phosphorylation at Ser-129 in neurons. PLK2 directly phosphorylates alpha-synuclein at Ser-129 in an in vitro biochemical assay. Inhibitors of PLK kinases inhibited alpha-synuclein phosphorylation both in primary cortical cell cultures and in mouse brain in vivo. Finally, specific knockdown of PLK2 expression by transduction with short hairpin RNA constructs or by knock-out of the plk2 gene reduced p-Ser-129 levels. These results indicate that PLK2 plays a critical role in alpha-synuclein phosphorylation in central nervous system.

Phosphorylation of Ser-129 is the dominant pathological modification of alpha-synuclein in familial and sporadic Lewy body disease.

A comprehensive, unbiased inventory of synuclein forms present in Lewy bodies from patients with dementia with Lewy bodies was carried out using two-dimensional immunoblot analysis, novel sandwich enzyme-linked immunosorbent assays with modification-specific synuclein antibodies, and mass spectroscopy. The predominant modification of alpha-synuclein in Lewy bodies is a single phosphorylation at Ser-129. In addition, there is a set of characteristic modifications that are present to a lesser extent, including ubiquitination at Lys residues 12, 21, and 23 and specific truncations at Asp-115, Asp-119, Asn-122, Tyr-133, and Asp-135. No other modifications are detectable by tandem mass spectrometry mapping, except for a ubiquitous N-terminal acetylation. Small amounts of Ser-129 phosphorylated and Asp-119-truncated alpha-synuclein are present in the soluble fraction of both normal and disease brains, suggesting that these Lewy body-associated forms are produced during normal metabolism of alpha-synuclein. In contrast, ubiquitination is only detected in Lewy bodies and is primarily present on phosphorylated synuclein; it therefore likely occurs after phosphorylated synuclein has deposited into Lewy bodies. This invariant pattern of specific phosphorylation, truncation, and ubiquitination is also present in the detergent-insoluble fraction of brain from patients with familial Parkinson's disease (synuclein A53T mutation) as well as multiple system atrophy, suggesting a common pathogenic pathway for both genetic and sporadic Lewy body diseases. These observations are most consistent with a model in which preferential accumulation of normally produced Ser-129 phosphorylated alpha-synuclein is the key event responsible for the formation of Lewy bodies in various Lewy body diseases.