Doxycycline, levofloxacin, and moxifloxacin are superior to ciprofloxacin in treating anthrax meningitis in rabbits and NHP

Efficient treatment of anthrax-related meningitis in patients poses a significant therapeutic challenge. Previously, we demonstrated in our anthrax meningitis rabbit model that ciprofloxacin treatment is ineffective with most of the treated animals succumbing to the infection. Herein we tested the efficacy of doxycycline in our rabbit model and found it highly effective. Since all of our findings are based on a rabbit model, we test the efficacy of ciprofloxacin or doxycycline in a specific central nervous system (CNS) model developed in non-human primates (NHPs). Similar to rabbits, ciprofloxacin treatment was ineffective, while doxycycline protected the infected rhesus macaques (n = 2) from the lethal CNS Bacillus anthracis infection. To test whether the low efficacy of Ciprofloxacin is an example of low efficacy of all fluoroquinolones or only this substance, we treated rabbits that were inoculated intracisterna magna (ICM) with levofloxacin or moxifloxacin. We found that in contrast to ciprofloxacin, levofloxacin and moxifloxacin were highly efficacious in treating lethal anthrax-related meningitis in rabbits and NHP (levofloxacin). We demonstrated (in naïve rabbits) that this difference probably results from variances in blood-brain-barrier penetration of the different fluoroquinolones. The combined treatment of doxycycline and any one of the tested fluoroquinolones was highly effective in the rabbit CNS infection model. The combined treatment of doxycycline and levofloxacin was effective in an inhalation rabbit model, as good as the doxycycline mono-therapy. These findings imply that while ciprofloxacin is highly effective as a post-exposure prophylactic drug, using this drug to treat symptomatic patients should be reconsidered.

In Vitro and In Vivo Therapeutic Potential of 6,6'-Dihydroxythiobinupharidine (DTBN) from Nuphar lutea on Cells and K18-hACE2 Mice Infected with SARS-CoV-2

We have previously published research on the anti-viral properties of an alkaloid mixture extracted from Nuphar lutea, the major components of the partially purified mixture found by NMR analysis. These are mostly dimeric sesquiterpene thioalkaloids called thiobinupharidines and thiobinuphlutidines against the negative strand RNA measles virus (MV). We have previously reported that this extract inhibits the MV as well as its ability to downregulate several MV proteins in persistently MV-infected cells, especially the P (phospho)-protein. Based on our observation that the Nuphar extract is effective in vitro against the MV, and the immediate need that the coronavirus disease 2019 (COVID-19) pandemic created, we tested here the ability of 6,6'-dihydroxythiobinupharidine DTBN, an active small molecule, isolated from the Nuphar lutea extract, on COVID-19. As shown here, DTBN effectively inhibits SARS-CoV-2 production in Vero E6 cells at non-cytotoxic concentrations. The short-term daily administration of DTBN to infected mice delayed the occurrence of severe clinical outcomes, lowered virus levels in the lungs and improved survival with minimal changes in lung histology. The viral load on lungs was significantly reduced in the treated mice. DTBN is a pleiotropic small molecule with multiple targets. Its anti-inflammatory properties affect a variety of pathogens including SARS-CoV-2 as shown here. Its activity appears to target both pathogen specific (as suggested by docking analysis) as well as cellular proteins, such as NF-κB, PKCs, cathepsins and topoisomerase 2, that we have previously identified in our work. Thus, this combined double action of virus inhibition and anti-inflammatory activity may enhance the overall effectivity of DTBN. The promising results from this proof-of-concept in vitro and in vivo preclinical study should encourage future studies to optimize the use of DTBN and/or its molecular derivatives against this and other related viruses.

Cap-independent translation and a precisely located RNA sequence enable SARS-CoV-2 to control host translation and escape anti-viral response

Translation of SARS-CoV-2-encoded mRNAs by the host ribosomes is essential for its propagation. Following infection, the early expressed viral protein NSP1 binds the ribosome, represses translation, and induces mRNA degradation, while the host elicits an anti-viral response. The mechanisms enabling viral mRNAs to escape this multifaceted repression remain obscure. Here we show that expression of NSP1 leads to destabilization of multi-exon cellular mRNAs, while intron-less transcripts, such as viral mRNAs and anti-viral interferon genes, remain relatively stable. We identified a conserved and precisely located cap-proximal RNA element devoid of guanosines that confers resistance to NSP1-mediated translation inhibition. Importantly, the primary sequence rather than the secondary structure is critical for protection. We further show that the genomic 5'UTR of SARS-CoV-2 drives cap-independent translation and promotes expression of NSP1 in an eIF4E-independent and Torin1-resistant manner. Upon expression, NSP1 further enhances cap-independent translation. However, the sub-genomic 5'UTRs are highly sensitive to eIF4E availability, rendering viral propagation partially sensitive to Torin1. We conclude that the combined NSP1-mediated degradation of spliced mRNAs and translation inhibition of single-exon genes, along with the unique features present in the viral 5'UTRs, ensure robust expression of viral mRNAs. These features can be exploited as potential therapeutic targets.

Revisiting SARS-CoV-2 environmental contamination by patients with COVID-19: The Omicron variant does not differ from previous strains

SARS-CoV-2 Omicron strain emergence raised concerns that its enhanced infectivity is partly due to altered spread/contamination modalities. We therefore sampled high-contact surfaces and air in close proximity to patients who were verified as infected with the Omicron strain, using identical protocols applied to sample patients positive to the original or Alpha strains. Cumulatively, for all 3 strains, viral RNA was detected in 90 of 168 surfaces and 6 of 49 air samples (mean cycle threshold [Ct]=35.2±2.5). No infective virus was identified. No significant differences in prevalence were found between strains.

A Novel Quantitative Multi-Component Serological Assay for SARS-CoV-2 Vaccine Evaluation

A multi-component microarray, applying a novel analysis algorithm, was developed for quantitative evaluation of the SARS-CoV-2 vaccines' immunogenicity. The array enables simultaneous quantitation of IgG, IgM, and IgA, specific to the SARS-CoV-2 spike, receptor binding domain, and nucleocapsid proteins. The developed methodology is based on calculating an apparent immunoglobulin signal from the linear range of the fluorescent read-outs generated by scanning the microarray slides at different exposure times. A dedicated algorithm, employing a rigorous set of embedded conditions, then generates a normalized signal for each of the unique assays. Qualification of the multi-component array performance (evaluating linearity, extended dynamic-range, specificity, precision, and accuracy) was carried out with an in-house COVID-19, qRT-PCR positive serum, as well as pre-pandemic commercial negative sera. Results were compared to the WHO international standard for anti-SARS-CoV-2 immunoglobulins. Specific IgG, IgM, and IgA signals obtained by this array enabled successful discrimination between SARS-CoV-2 q-RT-PCR positive (seroconverted SARS-CoV-2 patients) and negative (naïve) samples. This array is currently used for evaluation of the humoral response to BriLife, the VSV-based Israeli vaccine during phase I/II clinical trials.

Development of an immunofluorescence assay for detection of SARS-CoV-2

SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, emerged as the cause of a global crisis in 2019. Currently, the main method for identification of SARS-CoV-2 is a reverse transcription (RT)-PCR assay designed to detect viral RNA in oropharyngeal (OP) or nasopharyngeal (NP) samples. While the PCR assay is considered highly specific and sensitive, this method cannot determine the infectivity of the sample, which may assist in evaluation of virus transmissibility from patients and breaking transmission chains. Thus, cell-culture-based approaches such as cytopathic effect (CPE) assays are routinely employed for the identification of infectious viruses in NP/OP samples. Despite their high sensitivity, CPE assays take several days and require additional diagnostic tests in order to verify the identity of the pathogen. We have therefore developed a rapid immunofluorescence assay (IFA) for the specific detection of SARS-CoV-2 in NP/OP samples following cell culture infection. Initially, IFA was carried out on Vero E6 cultures infected with SARS-CoV-2 at defined concentrations, and infection was monitored at different time points. This test was able to yield positive signals in cultures infected with 10 pfu/ml at 12 hours postinfection (PI). Increasing the incubation time to 24 hours reduced the detectable infective dose to 1 pfu/ml. These IFA signals occur before the development of CPE. When compared to the CPE test, IFA has the advantages of specificity, rapid detection, and sensitivity, as demonstrated in this work.

Preliminary nonclinical safety and immunogenicity of an rVSV-ΔG-SARS-CoV-2-S vaccine in mice, hamsters, rabbits and pigs

rVSV-ΔG-SARS-CoV-2-S is a clinical stage (Phase 2) replication competent recombinant vaccine against SARS-CoV-2. To evaluate the safety profile of the vaccine, a series of non-clinical safety, immunogenicity and efficacy studies were conducted in four animal species, using multiple doses (up to 10⁸ Plaque Forming Units/animal) and dosing regimens. There were no treatment-related mortalities or any noticeable clinical signs in any of the studies. Compared to unvaccinated controls, hematology and biochemistry parameters were unremarkable and no adverse histopathological findings. There was no detectable viral shedding in urine, nor viral RNA detected in whole blood or serum samples seven days post vaccination. The rVSV-ΔG-SARS-CoV-2-S vaccination gave rise to neutralizing antibodies, cellular immune responses, and increased lymphocytic cellularity in the spleen germinal centers and regional lymph nodes. No evidence for neurovirulence was found in C57BL/6 immune competent mice or in highly sensitive type I interferon knock-out mice. Vaccine virus replication and distribution in K18-human Angiotensin-converting enzyme 2-transgenic mice showed a gradual clearance from the vaccination site with no vaccine virus recovered from the lungs. The nonclinical data suggest that the rVSV-ΔG-SARS-CoV-2-S vaccine is safe and immunogenic. These results supported the initiation of clinical trials, currently in Phase 2.

LAMP-Seq enables sensitive, multiplexed COVID-19 diagnostics using molecular barcoding

Frequent testing of large population groups combined with contact tracing and isolation measures will be crucial for containing Coronavirus Disease 2019 outbreaks. Here we present LAMP-Seq, a modified, highly scalable reverse transcription loop-mediated isothermal amplification (RT-LAMP) method. Unpurified biosamples are barcoded and amplified in a single heat step, and pooled products are analyzed en masse by sequencing. Using commercial reagents, LAMP-Seq has a limit of detection of ~2.2 molecules per µl at 95% confidence and near-perfect specificity for severe acute respiratory syndrome coronavirus 2 given its sequence readout. Clinical validation of an open-source protocol with 676 swab samples, 98 of which were deemed positive by standard RT-qPCR, demonstrated 100% sensitivity in individuals with cycle threshold values of up to 33 and a specificity of 99.7%, at a very low material cost. With a time-to-result of fewer than 24 h, low cost and little new infrastructure requirement, LAMP-Seq can be readily deployed for frequent testing as part of an integrated public health surveillance program.

SARS-CoV-2 infects the human kidney and drives fibrosis in kidney organoids

Kidney failure is frequently observed during and after COVID-19, but it remains elusive whether this is a direct effect of the virus. Here, we report that SARS-CoV-2 directly infects kidney cells and is associated with increased tubule-interstitial kidney fibrosis in patient autopsy samples. To study direct effects of the virus on the kidney independent of systemic effects of COVID-19, we infected human-induced pluripotent stem-cell-derived kidney organoids with SARS-CoV-2. Single-cell RNA sequencing indicated injury and dedifferentiation of infected cells with activation of profibrotic signaling pathways. Importantly, SARS-CoV-2 infection also led to increased collagen 1 protein expression in organoids. A SARS-CoV-2 protease inhibitor was able to ameliorate the infection of kidney cells by SARS-CoV-2. Our results suggest that SARS-CoV-2 can directly infect kidney cells and induce cell injury with subsequent fibrosis. These data could explain both acute kidney injury in COVID-19 patients and the development of chronic kidney disease in long COVID.

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COVID-19 patients present tubulo-interstitial kidney fibrosis compared with controls

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SARS-CoV-2 infection stimulates profibrotic signaling in human kidney organoids

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SARS-CoV-2 infection can be inhibited by a protease blocker in human kidney organoids

A Serological Snapshot of COVID-19 Initial Stages in Israel by a 6-Plex Antigen Array

The first case of SARS-CoV-2 was discovered in Israel in late February 2020. Three major outbreaks followed, resulting in over 800,000 cases and over 6,000 deaths by April 2021. Our aim was characterization of a serological snapshot of Israeli patients and healthy adults in the early months of the COVID-19 pandemic. Sera from 55 symptomatic COVID-19 patients and 146 healthy subjects (early-pandemic, reverse transcription-quantitative PCR [qRT-PCR]-negative), collected in Israel between March and April 2020, were screened for SARS-CoV-2-specific IgG, IgM, and IgA antibodies, using a 6-plex antigen microarray presenting the whole inactivated virus and five viral antigens: a stabilized version of the spike ectodomain (S2P), spike subunit 1 (S1), receptor-binding-domain (RBD), N-terminal-domain (NTD), and nucleocapsid (NC). COVID-19 patients, 4 to 40 days post symptom onset, presented specific IgG to all of the viral antigens (6/6) in 54 of the 55 samples (98% sensitivity). Specific IgM and IgA antibodies for all six antigens were detected in only 10% (5/55) and 4% (2/55) of the patients, respectively, suggesting that specific IgG is a superior serological marker for COVID-19. None of the qRT-PCR-negative sera reacted with all six viral antigens (100% specificity), and 48% (70/146) were negative throughout the panel. Our findings confirm a low seroprevalence of anti-SARS-CoV-2 antibodies in the Israeli adult population prior to the COVID-19 outbreak. We further suggest that the presence of low-level cross-reacting antibodies in naive individuals calls for a combined, multiantigen analysis for accurate discrimination between naive and exposed individuals. IMPORTANCE A 6-plex protein array presenting the whole inactivated virus and five nucleocapsid and spike-derived SARS-CoV-2 antigens was used to generate a serological snapshot of SARS-CoV-2 seroprevalence and seroconversion in Israel in the early months of the pandemic. Our findings confirm a very low seroprevalence of anti-SARS-CoV-2 antibodies in the Israeli adult population. We further propose that the presence of low-level nonspecific antibodies in naive individuals calls for a combined, multiantigen analysis for accurate discrimination between naive and exposed individuals enabling accurate determination of seroconversion. The developed assay is currently applied to evaluate immune responses to the Israeli vaccine during human phase I/II trials.

Mice with induced pulmonary morbidities display severe lung inflammation and mortality following exposure to SARS-CoV-2

Mice are normally unaffected by SARS coronavirus 2 (SARS-CoV-2) infection since the virus does not bind effectively to the murine version of the angiotensin-converting enzyme 2 (ACE2) receptor molecule. Here, we report that induced mild pulmonary morbidities rendered SARS-CoV-2–refractive CD-1 mice susceptible to this virus. Specifically, SARS-CoV-2 infection after application of low doses of the acute lung injury stimulants bleomycin or ricin caused severe disease in CD-1 mice, manifested by sustained body weight loss and mortality rates greater than 50%. Further studies revealed markedly higher levels of viral RNA in the lungs, heart, and serum of low-dose ricin–pretreated mice compared with non-pretreated mice. Furthermore, lung extracts prepared 2–3 days after viral infection contained subgenomic mRNA and virus particles capable of replication only when derived from the pretreated mice. The deleterious effects of SARS-CoV-2 infection were effectively alleviated by passive transfer of polyclonal or monoclonal antibodies generated against the SARS-CoV-2 receptor binding domain (RBD). Thus, viral cell entry in the sensitized mice seems to depend on viral RBD binding, albeit by a mechanism other than the canonical ACE2-mediated uptake route. This unique mode of viral entry, observed over a mildly injured tissue background, may contribute to the exacerbation of coronavirus disease 2019 (COVID-19) pathologies in patients with preexisting morbidities.

Role of acpA and acpB in Bacillus anthracis capsule accumulation and toxin independent pathogenicity in rabbits

The poly- δ- d-glutamic acid capsule of Bacillus anthracis plays a major role in this bacterium pathogenicity. Capsule synthesis relies on a 5 gene operon; capB, C, A, D and E that are regulated by acpA and acpB, that respond to the major virulence regulator - atxA. We took a genetic approach to examine the involvement of acpA and acpB in capsule production in vitro and on B. anthracis virulence in vivo. To complement the effect of the mutations on capsule accumulation in vitro, we applied our toxin independent systemic infection method to study their effects in vivo. We found that though the roles of acpA and axpB are redundant in vitro, deleting acpA had a significant effect on pathogenicity, mainly on the time to death. As expected, deletion of both acpA and acpB resulted in loss of capsule accumulation in vitro and full attenuation in vivo, indicating that capsule production depends exclusively on acpA/B regulation. To identify additional effects of acpA and acpB on pathogenicity via non-capsule related virulence pathways, we bypassed acpA/B regulation by inserting the pagA promotor upstream to the cap operon, diverting regulation directly to atxA. This resulted in restoration of capsule accumulation in vitro and virulence (in intravenous or subcutaneous inoculation) in vivo. To test for additional pXO2-based genes involved in capsule production, we cloned the pagA_prom-capA-E into the chromosome of VollumΔpXO2, which restored capsule accumulation. These results indicate that of the pXO2 genes, only capA-E and acpA are required for capsule production.

Spike vs nucleocapsid SARS-CoV-2 antigen detection: application in nasopharyngeal swab specimens

Public health experts emphasize the need for quick, point-of-care SARS-CoV-2 detection as an effective strategy for controlling virus spread. To this end, many “antigen” detection devices were developed and commercialized. These devices are mostly based on detecting SARS-CoV-2’s nucleocapsid protein. Recently, alerts issued by both the FDA and the CDC raised concerns regarding the devices’ tendency to exhibit false positive results. In this work, we developed a novel alternative spike-based antigen assay, comprising four high-affinity, specific monoclonal antibodies, directed against different epitopes on the spike’s S1 subunit. The assay’s performance was evaluated for COVID-19 detection from nasopharyngeal swabs, compared to an in-house nucleocapsid-based assay, composed of novel antibodies directed against the nucleocapsid. Detection of COVID-19 was carried out in a cohort of 284 qRT-PCR positive and negative nasopharyngeal swab samples. The time resolved fluorescence (TRF) ELISA spike assay displayed very high specificity (99%) accompanied with a somewhat lower sensitivity (66% for Ct < 25), compared to the nucleocapsid ELISA assay which was more sensitive (85% for Ct < 25) while less specific (87% specificity). Despite being outperformed by qRT-PCR, we suggest that there is room for such tests in the clinical setting, as cheap and rapid pre-screening tools. Our results further suggest that when applying antigen detection, one must consider its intended application (sensitivity vs specificity), taking into consideration that the nucleocapsid might not be the optimal target. In this regard, we propose that a combination of both antigens might contribute to the validity of the results.

Specific and Rapid SARS-CoV-2 Identification Based on LC-MS/MS Analysis

SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, emerged as the cause of a global crisis. Rapid and reliable clinical diagnosis is essential for effectively controlling transmission. The gold standard assay for SARS-CoV-2 identification is the highly sensitive real-time quantitative polymerase chain reaction (RT-qPCR); however, this assay depends on specialized reagents and may suffer from false results. Thus, additional assays based on different approaches could be beneficial. Here, we present a novel method for SARS-CoV-2 identification based on mass spectrometry. The approach we implemented combines a multistep procedure for the rational down-selection of a set of reliable markers out of all optional in silico derived tryptic peptides in viral proteins, followed by monitoring of peptides derived from tryptic digests of purified proteins, cell-cultured SARS-CoV-2, and nasopharyngeal (NP) swab matrix spiked with the virus. The marker selection was based on specificity to SARS-CoV-2 and on analytical parameters including sensitivity, linearity, and reproducibility. The final assay is based on six unique and specific peptide markers for SARS-CoV-2 identification. The simple and rapid (2.5 h) protocol we developed consists of virus heat inactivation and denaturation, tryptic digestion, and identification of the selected markers by liquid chromatography coupled to high-resolution mass spectrometry (LC-MS/MS). The developed assay enabled the identification of 10⁴ PFU/mL SARS-CoV-2 spiked into buffer. Finally, the assay was successfully applied to 16 clinical samples diagnosed by RT-qPCR, achieving 94% concordance with the current gold standard assay. To conclude, the novel MS-based assay described here is specific, rapid, simple, and is believed to provide a complementary assay to the RT-qPCR method.

Detection and infectivity potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) environmental contamination in isolation units and quarantine facilities

OBJECTIVES

Environmental surfaces have been suggested as likely contributors in the transmission of COVID-19. This study assessed the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contaminating surfaces and objects in two hospital isolation units and a quarantine hotel.

METHODS

SARS-CoV-2 virus stability and infectivity on non-porous surfaces was tested under controlled laboratory conditions. Surface and air sampling were conducted at two COVID-19 isolation units and in a quarantine hotel. Viral RNA was detected by RT-PCR and infectivity was assessed by VERO E6 CPE test.

RESULTS

In laboratory-controlled conditions, SARS-CoV-2 gradually lost its infectivity completely by day 4 at ambient temperature, and the decay rate of viral viability on surfaces directly correlated with increase in temperature. Viral RNA was detected in 29/55 surface samples (52.7%) and 16/42 surface samples (38%) from the surroundings of symptomatic COVID-19 patients in isolation units of two hospitals and in a quarantine hotel for asymptomatic and very mild COVID-19 patients. None of the surface and air samples from the three sites (0/97) were found to contain infectious titres of SARS-Cov-2 on tissue culture assay.

CONCLUSIONS

Despite prolonged viability of SARS-CoV-2 under laboratory-controlled conditions, uncultivable viral contamination of inanimate surfaces might suggest low feasibility for indirect fomite transmission.

Actin regulators in cancer progression and metastases: From structure and function to cytoskeletal dynamics

The cytoskeleton is a central factor contributing to various hallmarks of cancer. In recent years, there has been increasing evidence demonstrating the involvement of actin regulatory proteins in malignancy, and their dysregulation was shown to predict poor clinical prognosis. Although enhanced cytoskeletal activity is often associated with cancer progression, the expression of several inducers of actin polymerization is remarkably reduced in certain malignancies, and it is not completely clear how these changes promote tumorigenesis and metastases. The complexities involved in cytoskeletal induction of cancer progression therefore pose considerable difficulties for therapeutic intervention; it is not always clear which cytoskeletal regulator should be targeted in order to impede cancer progression, and whether this targeting may inadvertently enhance alternative invasive pathways which can aggravate tumor growth. The entire constellation of cytoskeletal machineries in eukaryotic cells are numerous and complex; the system is comprised of and regulated by hundreds of proteins, which could not be covered in a single review. Therefore, we will focus here on the actin cytoskeleton, which encompasses the biological machinery behind most of the key cellular functions altered in cancer, with specific emphasis on actin nucleating factors and nucleation-promoting factors. Finally, we discuss current therapeutic strategies for cancer which aim to target the cytoskeleton.

Using old antibiotics to treat ancient bacterium-β-lactams for Bacillus anthracis meningitis

As Bacillus anthracis spores pose a proven bio-terror risk, the treatment focus has shifted from exposed populations to anthrax patients and the need for effective antibiotic treatment protocols increases. The CDC recommends carbapenems and Linezolid (oxazolidinone), for the treatment of anthrax, particularly for the late, meningeal stages of the disease. Previously we demonstrated that treatment with Meropenem or Linezolid, either as a single treatment or in combination with Ciprofloxacin, fails to protect rabbits from anthrax-meningitis. In addition, we showed that the failure of Meropenem was due to slow BBB penetration rather than low antibacterial activity. Herein, we tested the effect of increasing the dose of the antibiotic on treatment efficacy. We found that for full protection (88% cure rate) the dose should be increased four-fold from 40 mg/kg to 150 mg/kg. In addition, B. anthracis is a genetically stable bacterium and naturally occurring multidrug resistant B. anthracis strains have not been reported. In this manuscript, we report the efficacy of classical β-lactams as a single treatment or in combination with β-lactamase inhibitors in treating anthrax meningitis. We demonstrate that Ampicillin based treatment of anthrax meningitis is largely efficient (66%). The high efficacy (88-100%) of Augmentin (Amoxicillin and Clavulonic acid) and Unasyn (Ampicillin and Sulbactam) makes them a favorable choice due to reports of β-lactam resistant B. anthracis strains. Tazocin (Piperacillin and Tazobactam) proved inefficient compared to the highly efficient Augmentin and Unasyn.

NLRP3 inflammasome in fibroblasts links tissue damage with inflammation in breast cancer progression and metastasis

Cancer-Associated Fibroblasts (CAFs) were shown to orchestrate tumour-promoting inflammation in multiple malignancies, including breast cancer. However, the molecular pathways that govern the inflammatory role of CAFs are poorly characterised. In this study we found that fibroblasts sense damage-associated molecular patterns (DAMPs), and in response activate the NLRP3 inflammasome pathway, resulting in instigation of pro-inflammatory signalling and secretion of IL-1β. This upregulation was evident in CAFs in mouse and in human breast carcinomas. Moreover, CAF-derived inflammasome signalling facilitated tumour growth and metastasis, which was attenuated when NLRP3 or IL-1β were specifically ablated. Functionally, CAF-derived inflammasome promoted tumour progression and metastasis by modulating the tumour microenvironment towards an immune suppressive milieu and by upregulating the expression of adhesion molecules on endothelial cells. Our findings elucidate a mechanism by which CAFs promote breast cancer progression and metastasis, by linking the physiological tissue damage response of fibroblasts with tumour-promoting inflammation.

Infection with a Nonencapsulated Bacillus anthracis Strain in Rabbits-The Role of Bacterial Adhesion and the Potential for a Safe Live Attenuated Vaccine

Nonencapsulated (∆pXO2) Bacillus anthracis strains are commonly used as vaccines and for anthrax research, mainly in the mouse model. Previously, we demonstrated that the infection of rabbits, intranasally or subcutaneously, with the spores of a fully virulent strain results in the systemic dissemination of the bacteria, meningitis, and death, whereas ∆pXO2 strains are fully attenuated in this animal model. We used the intravenous inoculation of rabbits to study the pathogenicity of the ∆pXO2 strain infection. Bacteremia, brain bacterial burden, and pathology were used as criteria to compare the Vollum∆pXO2 disease to the wild type Vollum infection. To test the role of adhesion in the virulence of Vollum∆pXO2, we deleted the major adhesion protein BslA and tested the virulence and immunogenicity of this mutant. We found that 50% of the rabbits succumb to Vollum∆pXO2 strain following i.v. infection, a death that was accompanied with significant neurological symptoms. Pathology revealed severe brain infection coupled with an atypical massive bacterial growth into the parenchyma. Contrary to the Vollum strain, deletion of the bslA gene fully attenuated the ∆pXO2 strain. Though the Vollum∆pXO2 cannot serve as a model for B. anthracis pathogenicity in rabbits, deletion of the bslA gene prevents central nervous system (CNS) infections, possibly leading to the generation of a safer vaccine.

Pathology of wild-type and toxin-independent Bacillus anthracis meningitis in rabbits

Hemorrhagic meningitis is considered a complication of anthrax and was reported in about 50% of deadly cases in humans and non-human primates (NHP). Recently we demonstrated in Guinea pigs and rabbits that 100% of the B. anthracis-infected animals presented histopathology of meningitis at the time of death, some without any sign of hemorrhage. A similar pathology was observed in animals that succumbed following infection with the toxin deficient mutant, thus indicating that anthrax meningitis is a toxin-independent phenomenon. In this manuscript we describe a histopathological study of the B. anthracis infection of the central nervous system (CNS). Though we could find sporadic growth of the bacteria around blood vessels in the cortex, we report that the main infiltration route is the choroid plexus. We found massive destruction of entire sections of the choroid plexus coupled with massive aggregation of bacilli in the ventricles, in close proximity to the parenchyma. The choroid plexus also contained significant amounts of intravascular bacterial aggregates, often enclosed in what appear to be fibrin-like clots. The high concentration of these aggregates in areas of significant tissue destruction combined with the fact that capsular B. anthracis bacteria have a low tendency to adhere to endothelial cells, might suggest that these clots are used as an adherence mechanism by the bacteria. The major histopathological finding is meningitis. We find massive bacterial growth in the meninges without evidence of encephalitis, even when the bacteria emerge from a parenchymal blood vessel. Erythrocytes were present within the meningeal space but no clear vasculitis could be detected. Histology of the brain stem indicates meningitis, edema and hemorrhages that might explain death from suffocation due to direct damage to the respiratory center. All of these processes are toxin-independent, since they were observed following infection with either the wild type strain or the toxin-deficient mutant. Herein, we propose that the first step of anthrax-meningitis is bacterial adhesion to the blood vessels by manipulating coagulation, mainly in the choroid plexus. The trapped bacteria then destroy sections of the choroid plexus, resulting in penetration into the CSF, leading to meningitis and hemorrhage. Death could be the result of increased intracranial pressure and/or damage to the brain stem.

Induction of the intestinal stem cell signature gene SMOC-2 is required for L1-mediated colon cancer progression

Overactivation of Wnt-β-catenin signaling, including β-catenin-TCF target gene expression, is a hallmark of colorectal cancer (CRC) development. We identified the immunoglobulin family of cell-adhesion receptors member L1 as a β-catenin-TCF target gene preferentially expressed at the invasive edge of human CRC tissue. L1 can confer enhanced motility and liver metastasis when expressed in CRC cells. This ability of L1-mediated metastasis is exerted by a mechanism involving ezrin and the activation of NF-κB target genes. In this study, we identified the secreted modular calcium-binding matricellular protein-2 (SMOC-2) as a gene activated by L1-ezrin-NF-κB signaling. SMOC-2 is also known as an intestinal stem cell signature gene in mice expressing Lgr5 in cells at the bottom of intestinal crypts. The induction of SMOC-2 expression in L1-expressing CRC cells was necessary for the increase in cell motility, proliferation under stress and liver metastasis conferred by L1. SMOC-2 expression induced a more mesenchymal like phenotype in CRC cells, a decrease in E-cadherin and an increase in Snail by signaling that involves integrin-linked kinase (ILK). SMOC-2 was localized at the bottom of normal human colonic crypts and at increased levels in CRC tissue with preferential expression in invasive areas of the tumor. We found an increase in Lgr5 levels in CRC cells overexpressing L1, p65 or SMOC-2, suggesting that L1-mediated CRC progression involves the acquisition of a stem cell-like phenotype, and that SMOC-2 elevation is necessary for L1-mediated induction of more aggressive/invasive CRC properties.

Tumor-derived osteopontin reprograms normal mammary fibroblasts to promote inflammation and tumor growth in breast cancer

Breast tumors are characterized by an extensive desmoplastic stroma, abundantly populated by fibroblasts. Cancer-associated fibroblasts (CAF) support tumorigenesis by stimulating angiogenesis, cancer cell proliferation, and invasion. CAF also orchestrate tumor-promoting inflammation in multiple tumor types, including breast cancer. However, the mechanisms through which normal tissue fibroblasts are reprogrammed to tumor-promoting CAFs are mainly obscure. Here, we show that mammary fibroblasts can be educated by breast cancer cells to become activated to a proinflammatory state that supports malignant progression. Proteomic analysis of breast cancer cell-secreted factors identified the secreted proinflammatory mediator osteopontin, which has been implicated in inflammation, tumor progression, and metastasis. Osteopontin was highly secreted by mouse and human breast cancer cells, and tumor cell-secreted osteopontin activated a CAF phenotypes in normal mammary fibroblasts in vitro and in vivo. Osteopontin was sufficient to induce fibroblast reprogramming and neutralizing antibodies against osteopontin-blocked fibroblast activation induced by tumor cells. The ability of secreted osteopontin to activate mammary fibroblasts relied upon its known receptors CD44 and αVβ3 integrin. Strikingly, osteopontin silencing in tumor cells in vivo attenuated stromal activation and inhibited tumor growth. Our findings establish a critical functional role for paracrine signaling by tumor-derived osteopontin in reprograming normal fibroblasts into tumor-promoting CAFs.

c-Kit is suppressed in human colon cancer tissue and contributes to L1-mediated metastasis

The transmembrane neural cell adhesion receptor L1 is a Wnt/β-catenin target gene expressed in many tumor types. In human colorectal cancer, L1 localizes preferentially to the invasive front of tumors and when overexpressed in colorectal cancer cells, it facilitates their metastasis to the liver. In this study, we investigated genes that are regulated in human colorectal cancer and by the L1-NF-κB pathway that has been implicated in liver metastasis. c-Kit was the most highly suppressed gene in both colorectal cancer tissue and the L1-NF-κB pathway. c-Kit suppression that resulted from L1-mediated signaling relied upon NF-κB, which directly inhibited the transcription of SP1, a major activator of the c-Kit gene promoter. Reconstituting c-Kit expression in L1-transfected cells blocked the biological effects conferred by L1 overexpression in driving motility and liver metastasis. We found that c-Kit expression in colorectal cancer cells is associated with a more pronounced epithelial morphology, along with increased expression of E-cadherin and decreased expression of Slug. Although c-Kit overexpression inhibited the motility and metastasis of L1-expressing colorectal cancer cells, it enhanced colorectal cancer cell proliferation and tumorigenesis, arguing that separate pathways mediate tumorigenicity and metastasis by c-Kit. Our findings provide insights into how colorectal cancer metastasizes to the liver, the most common site of dissemination in this cancer.

Nuclear factor-kappaB signaling and ezrin are essential for L1-mediated metastasis of colon cancer cells

Hyperactivation of beta-catenin-T-cell-factor (TCF)-regulated gene transcription is a hallmark of colorectal cancer (CRC). The cell-neural adhesion molecule L1CAM (hereafter referred to as L1) is a target of beta-catenin-TCF, exclusively expressed at the CRC invasive front in humans. L1 overexpression in CRC cells increases cell growth and motility, and promotes liver metastasis. Genes induced by L1 are also expressed in human CRC tissue but the mechanisms by which L1 confers metastasis are still unknown. We found that signaling by the nuclear factor kappaB (NF-kappaB) is essential, because inhibition of signaling by the inhibitor of kappaB super repressor (IkappaB-SR) blocked L1-mediated metastasis. Overexpression of the NF-kappaB p65 subunit was sufficient to increase CRC cell proliferation, motility and metastasis. Binding of the L1 cytodomain to ezrin - a cytoskeleton-crosslinking protein - is necessary for metastasis because when binding to L1 was interrupted or ezrin gene expression was suppressed with specific shRNA, metastasis did not occur. L1 and ezrin bound to and mediated the phosphorylation of IkappaB. We also observed a complex containing IkappaB, L1 and ezrin in the juxtamembrane region of CRC cells. Furthermore, we found that L1, ezrin and phosphorylated p65 are co-expressed at the invasive front in human CRC tissue, indicating that L1-mediated activation of NF-kappaB signaling involving ezrin is a major route of CRC progression.

Differential, positional-dependent transcriptional response of antigenic variation (var) genes to biological stress in Plasmodium falciparum

1% of the genes of the human malaria causing agent Plasmodium falciparum belong to the heterogeneous var gene family which encodes P. falciparum erythrocyte membrane protein 1 (PFEMP1). This protein mediates part of the pathogenesis of the disease by causing adherence of infected erythrocytes (IE) to the host endothelium. At any given time, only one copy of the family is expressed on the IE surface. The cues which regulate the allelic exclusion of these genes are not known. We show the existence of a differential expression pattern of these genes upon exposure to biological stress in relation to their positional placement on the chromosome – expression of centrally located var genes is induced while sub-telomeric copies of the family are repressed - this phenomenon orchestrated by the histone deacetylase pfsir2. Moreover, stress was found to cause a switch in the pattern of the expressed var genes thus acting as a regulatory cue. By using pharmacological compounds which putatively affect pfsir2 activity, distinct changes of var gene expression patterns were achieved which may have therapeutic ramifications. As disease severity is partly associated with expression of particular var gene subtypes, manipulation of the IE environment may serve as a mechanism to direct transcription towards less virulent genes.

L1-CAM in cancerous tissues

BACKGROUND

L1-cell adhesion molecule (L1-CAM) is a cell adhesion receptor of the immunoglobulin superfamily, known for its roles in nerve cell function. While originally believed to be present only in brain cells, in recent years L1-CAM has been detected in other tissues, and in a variety of cancer cells, including some common types of human cancer.

OBJECTIVE/METHODS

We review the prevalence of L1-CAM in human cancer, the possible mechanisms involved in L1-CAM-mediated tumorigenesis, and cancer therapies based upon L1-CAM antibody treatment.

RESULTS/CONCLUSIONS

In colon cancer cells, the L1-CAM gene was identified as a target of the Wnt/beta-catenin-TCF signaling pathway, and L1-CAM was exclusively detected at the invasive front of colon and ovarian cancer tissue. The expression of L1-CAM in normal and cancer cells enhanced tumorigenesis and conferred metastasis in colon cancer cells. Antibodies against the L1-CAM ectodomain severely inhibited the proliferation of a variety of cancer cells in culture and reduced tumor burden when injected into mice harboring cancer cells expressing L1-CAM. These results, in addition to the presence of L1-CAM on the cell surface and its restricted distribution in normal tissues, make it an ideal target for tumor therapy.