Chlamydia trachomatis Subverts Alpha-Actinins To Stabilize Its Inclusion

Chlamydia trachomatis is the leading cause of sexually transmitted bacterial disease and a global health burden. As an obligate intracellular pathogen, Chlamydia has evolved many strategies to manipulate its host and establish its intracellular niche called the inclusion. C. trachomatis reorganizes the host actin cytoskeleton to form scaffolds around the inclusion and reinforce the growing inclusion membrane. To control the kinetics and formation of actin scaffolds, Chlamydia expresses the effector InaC/CT813, which activates the host GTPase RhoA. Here, we have discovered that InaC stabilizes actin scaffolds through the host actin cross-linking proteins α-actinins 1 and 4. We demonstrate that α-actinins are recruited to the inclusion membrane in an InaC-dependent manner and associate with actin scaffolds that envelop the inclusion. Small interfering RNA (siRNA)-mediated knockdown of α-actinins differentially regulate the frequency of actin scaffolds and impair inclusion stability, leaving them susceptible to rupture and to nonionic detergent extraction. Overall, our data identify new host effectors that are subverted by InaC to stabilize actin scaffolds, highlighting the versatility of InaC as a key regulator of the host cytoskeletal network during Chlamydia infection. IMPORTANCE Despite antibiotics, recurrent C. trachomatis infections cause significant damage to the genital tract in men and women. Without a preventative vaccine, it is paramount to understand the virulence mechanisms that Chlamydia employs to cause disease. In this context, manipulation of the host cytoskeleton is a critical component of Chlamydia development. Actin scaffolds reinforce the integrity of Chlamydia's infectious vacuole, which is a critical barrier between Chlamydia and the host environment. Having previously established that InaC co-opts RhoA to promote the formation of actin scaffolds around the inclusion, we now show that Chlamydia hijacks a new class of host effectors, α-actinins, to cross-link these scaffolds and further stabilize the inclusion. We also establish that a core function of the chlamydial effector InaC is the regulation of cytoskeletal stability during Chlamydia infection. Ultimately, this work expands our understanding of how bacterial pathogens subvert the actin cytoskeleton by targeting fundamental host effector proteins.

Identification and characterization of M6903, an antagonistic anti-TIM-3 monoclonal antibody

T cell immunoglobulin and mucin domain-3 (TIM-3) is an immune checkpoint that regulates normal immune responses but can be exploited by tumor cells to evade immune surveillance. TIM-3 is primarily expressed on immune cells, particularly on dysfunctional and exhausted T cells, and engagement of TIM-3 with its ligands promotes TIM-3-mediated T cell inhibition. Antagonistic ligand-blocking anti-TIM-3 antibodies have the potential to abrogate T cell inhibition, activate antigen-specific T cells, and enhance anti-tumor immunity. Here we describe M6903, a fully human anti-TIM-3 antibody without effector function and with high affinity and selectivity to TIM-3. We demonstrate that M6903 blocks the binding of TIM-3 to three of its ligands, phosphatidylserine (PtdSer), carcinoembryonic antigen cell adhesion-related molecule 1 (CEACAM1), and galectin 9 (Gal-9). These results are supported by an atomic resolution crystal structure and functional assays, which demonstrate that M6903 monotherapy enhanced T cell activation. This activation was further enhanced by the combination of M6903 with bintrafusp alfa, a bifunctional fusion protein that simultaneously blocks the transforming growth factor-β (TGF-β) and programmed death ligand 1 (PD-L1) pathways. M6903 and bintrafusp alfa combination therapy also enhanced anti-tumor efficacy in huTIM-3 knock-in mice, relative to either monotherapy. These in vitro and in vivo data, along with favorable pharmacokinetics in marmoset monkeys, suggest that M6903 as a monotherapy warrants further pre-clinical assessment and that M6903 and bintrafusp alfa may be a promising combination therapy in the clinic.

Balancing Selectivity and Efficacy of Bispecific Epidermal Growth Factor Receptor (EGFR) × c-MET Antibodies and Antibody-Drug Conjugates

Bispecific antibodies (bsAbs) and antibody-drug conjugates (ADCs) have already demonstrated benefits for the treatment of cancer in several clinical studies, showing improved drug selectivity and efficacy. In particular, simultaneous targeting of prominent cancer antigens, such as EGF receptor (EGFR) and c-MET, by bsAbs has raised increasing interest for potentially circumventing receptor cross-talk and c-MET-mediated acquired resistance during anti-EGFR monotherapy. In this study, we combined the selectivity of EGFR × c-MET bsAbs with the potency of cytotoxic agents via bispecific antibody-toxin conjugation. Affinity-attenuated bispecific EGFR × c-MET antibody-drug conjugates demonstrated high in vitro selectivity toward tumor cells overexpressing both antigens and potent anti-tumor efficacy. Due to basal EGFR expression in the skin, ADCs targeting EGFR in general warrant early safety assessments. Reduction in EGFR affinity led to decreased toxicity in keratinocytes. Thus, the combination of bsAb affinity engineering with the concept of toxin conjugation may be a viable route to improve the safety profile of ADCs targeting ubiquitously expressed antigens.

Serous retinal detachment in hypertensive posterior reversible encephalopathy syndrome

In accelerated hypertension, vasogenic brain edema associated with PRES may represent either autoregulatory breakthrough leading to vasodilation or excessive autoregulation leading to vasoconstriction. We describe 2 patients with PRES in accelerated hypertension who had serous retinal detachments, a vasoconstrictive phenomenon. The concurrence of serous retinal detachment and PRES offers intriguing support for the idea that vasoconstriction rather than vasodilation is the mechanism of vasogenic edema in PRES.

Antifungal compounds redirect metabolic pathways in yeasts: metabolites as indicators of modes of action

AIMS

Metabolic pathways, e.g. biosynthesis of ergosterol or carbohydrate metabolism including respiration, are well-known targets of several fungicides. With our study we wanted to prove that metabolite profiles can be used to classify fungicides according to their mode of action and that concentrations of key metabolites are changed even without detectable reduced growth rates.

METHODS AND RESULTS

We exposed the yeasts Candida albicans and Saccharomyces cerevisiae to inhibitors of the electron transport chain and to compounds known to interact with osmotic stress defence pathways. Glycerol and ethanol were chosen as key metabolites of branches of glucose catabolism. Increased glycerol concentrations were observed not only when the osmotic stress response was activated, but also as response to the inhibition of the electron transfer chain, whereas elevated ethanol levels were observed only when the respiratory pathways were blocked.

CONCLUSIONS

The treatment of the yeasts Candida albicans and Saccharomyces cerevisiae with antimycotic compounds led to a redirection of metabolic pathways, which could be followed by the quantification of both the metabolites ethanol and glycerol. Only the combination of both concentration profiles allowed the clear distinction between inhibitors of the respiratory chain and effects on the osmotic stress response pathway. IMPACT OF STUDY: The extension of the number of metabolites to a comprehensive quantitative metabolic profile of compound-treated test organisms can be an additional tool in fungicide research allowing the detection of compounds which act on fungi and, moreover, the elucidation of modes of action.

Improving the efficacy of antibody-interleukin 2 fusion proteins by reducing their interaction with Fc receptors

Fusion proteins between whole antibodies (Abs) and cytokines (immunocytokines) such as interleukin 2 have shown efficacy in several mouse tumor models despite a circulating half-life that is significantly shorter than that of the original Ab. We have examined the potential mechanisms responsible for clearance and shown that an important factor is enhanced binding to Fc receptor (FcR). Improvements in the half-lives of two different immunocytokines were made by changing the isotype of the human heavy chain C region from IgG1 or IgG3 to those with reduced binding to FcR, e.g., IgG4. The same effect could also be achieved through site-directed mutagenesis of the FcR binding site in the IgG1 H chain. In vitro studies using mouse J774 FcR-expressing cells showed increased binding of interleukin 2-based immunocytokines, relative to their corresponding Abs, and that this was reversed in those fusion proteins made with IgG4 or mutated IgG1 H chains. All of the fusion proteins showing reduced FcR binding also had reduced Ab-dependent cellular cytotoxicity activity, as measured in 4-h chromium release assays. A complete loss of complement-dependent cytotoxicity activity was seen with an IgG4-based immunocytokine derived from an IgG1 Ab with potent activity. Despite these reduced effector functions, the IgG4-based immunocytokines with extended circulating half-lives showed equivalent (in the case of severe combined immunodeficiency mouse xenograft models) or better (in the case of syngeneic models) efficacy in mouse tumor models than the original IgG1-based molecules. These novel immunocytokines may show improved efficacy in therapeutic situations where T cell- rather than natural killer- or complement-mediated antitumor mechanisms are involved.

FP-21399 blocks HIV envelope protein-mediated membrane fusion and concentrates in lymph nodes

The identification of fusin and other chemokine receptors as coreceptors for HIV-1 has renewed the interest in agents that may prevent viral entry. Polyanionic compounds such as dextran sulfate, curdian sulfate, and suramin act on the V3 loop of the viral envelope and may prevent its interaction with fusin. These agents show activity against a wide range of HIV-1 strains, but have undesirable circulating half-life, bioavailability, and toxicity. We have developed a small molecule inhibitor of HIV-1 that has several advantages over these other agents. FP-21399 is a novel compound of the bis(disulfonaphthalene) dimethoxybenzene class that blocks entry of HIV into CD4+ cells and blocks fusion of infected and noninfected CD4+ cells. This compound only weakly inhibits binding of CD4 and gp120, at concentrations much greater than are required to block viral entry. Furthermore, FP-21399 can block the interaction between gp120 and antibodies directed against the V3 loop, but does not block binding of antibodies directed against the V4 loop. Animal studies demonstrate that FP-21399 is concentrated in lymph nodes, making it a promising compound for anti-HIV therapy. In SCID mice reconstituted with human immune cells, maintenance of HIV-1 infection was blocked by a 5-day treatment with low doses of FP-21399, suggesting that lymph node accumulation may contribute to antiviral activity. Finally, attempts to generate drug-resistant virus in cell culture resulted in only weakly resistant variants with IC90 values that are much lower than concentrations of FP-21399 found in lymph nodes.

Relation between residential radon concentrations and housing characteristics. The Cracow Study

The survey on indoor radon exposure was undertaken to explain whether the excess in lung cancer deaths in Cracow city center may be attributed to this particular exposure. A total of 310 detectors was placed in households randomly chosen from three homogenous strata of residential buildings. The first stratum included house in the old city center constructed predominantly out of the stone bricks. The second stratum covered area of the city with big apartment condominiums built out of concrete blocks. The third stratum consisted of single family houses located in a suburban area. From each of these residency strata a random sample of equal number of households has been chosen and the radon detectors were placed in households located at different levels of buildings. The three-month radon sampling data were used to determine the distribution of various levels of radon in the households. In the measurement of radon exposure the Landauer alpha-track samplers were used. The data collected show that the best single predictor of indoor radon concentrations was type of building. Other variables found to be associated significantly with indoor concentrations were household level in the building and house age. In general, residences with a concrete slabs and dwellings with rarely-opened windows were found to have slightly higher radon concentrations.

Irritant effects of formaldehyde exposure in mobile homes

This paper reports the irritant effects associated with formaldehyde exposures in mobile homes. Week-long, integrated formaldehyde concentrations were measured using passive monitors in summer and winter while the mobile home residents continued their normal activities. Information on acute health problems, chronic respiratory/allergic illnesses, smoking behavior, demographic variables, and time spent at home was obtained on over 1000 individuals during the sampling period. Measured formaldehyde concentrations varied from under the limit of detection (0.01 ppm) to 0.46 ppm. Formaldehyde exposure was estimated for each individual by multiplying the concentration measured in his or her home by the time he or she spent at home. Irritant effects were found to be associated with formaldehyde exposure after controlling for age, sex, smoking status, and chronic illnesses using a logistic procedure. Some of the interaction terms found to be significant indicated that there were synergistic effects between formaldehyde exposure and chronic health problems.

High-level expression of chimeric antibodies using adapted cDNA variable region cassettes

A rapid and generally applicable method for the modification of immunoglobulin cDNAs was developed so that the variable (V) regions could be expressed as cassettes, together with a variety of constant regions. Murine cDNAs were isolated, sequenced and the V regions joined to short oligonucleotides providing both splice donor sites and unique restriction sites for insertion into an expression vector. Using this strategy we have expressed the V regions of several murine antibodies, together with the human gamma 1 constant region. Although most of these chimeric antibodies were readily expressed, one murine light-chain cDNA sequence could not be expressed in transfected hybridoma cells. Reconstruction experiments indicate that the sequence created by the fusion of the murine leader and variable region blocked expression at the level of RNA accumulation. The methods described, as well as the potential problems of expression, are applicable to both traditional cDNA fragments and those obtained by in vitro amplification techniques.

The usefulness of Doppler time interval histogram analysis in arterial occlusion

The method based on the Time Interval Histogram analysis of the Doppler signal was applied for localisation of arterial diseases and the precision of the reconstructive operation. The preliminary investigations were carried out on the abdominal aorta of a dog. After that 87 patients were examined. The examination confirmed the usefulness of the method.

Heparin inhibition of antibody-dependent complement-mediated lysis

The effect of heparin on the monoclonal antibody-dependent complement-mediated lysis of human lymphoid cell lines and peripheral blood T-lymphocytes was studied. T-lymphoid cell lines (CEM and MOLT-3) were lysed by optimal concentrations of monoclonal antibodies and rabbit complement. Heparin at concentrations as low as 0.5 U/ml partially inhibited the complement-mediated lysis of all antibody-cell combinations while a heparin concentration of 25 U/ml produced complete inhibition. Lysis mediated by an IgG monoclonal antibody (J5) to the common acute lymphoblastic leukemia antigen (CALLA) was more sensitive to heparin inhibition than that due to an IgM antibody (VIL A1). Bovine and porcine heparin were equally inhibitory. Peripheral blood T-lymphocytes collected in heparin (100 U/ml) were resistant to complete lysis when treated with 17F12 and complement immediately after isolation; complete lysis was achieved only when they were incubated for 2 h prior to treatment. The role of monoclonal antibody and complement in the in vitro lysis of normal and leukemic lymphocytes is discussed.