Stochastic modelling of the effects of human-mobility restriction and viral infection characteristics on the spread of COVID-19.

After several months of "lockdown" as the sole answer to the COVID-19 pandemic, balancing the re-opening of society against the implementation of non-pharmaceutical measures needed for minimizing interpersonal contacts has become important. Here, we present a stochastic model that examines this problem. In our model, people are allowed to move between discrete positions on a one-dimensional grid with viral infection possible when two people are collocated at the same site. Our model features three sets of adjustable parameters, which characterize (i) viral transmission, (ii) viral detection, and (iii) degree of personal mobility, and as such, it is able to provide a qualitative assessment of the potential for second-wave infection outbreaks based on the timing, extent, and pattern of the lockdown relaxation strategies. Our results suggest that a full lockdown will yield the lowest number of infections (as anticipated) but we also found that when personal mobility exceeded a critical level, infections increased, quickly reaching a plateau that depended solely on the population density. Confinement was not effective if not accompanied by a detection/quarantine capacity surpassing 40% of the symptomatic patients. Finally, taking action to ensure a viral transmission probability of less than 0.4, which, in real life, may mean actions such as social distancing or mask-wearing, could be as effective as a soft lockdown.

FcγRIIb on B Cells and Myeloid Cells Modulates B Cell Activation and Autoantibody Responses via Different but Synergistic Pathways in Lupus-Prone Yaa Mice.

C57BL/6 (B6).FcγRIIb-/- Yaa mice spontaneously develop lethal lupus nephritis. To define the cell type-specific role of FcγRIIb in Yaa-associated lupus, we established B cell- (CD19Cre Yaa), myeloid cell- (C/EBPαCre Yaa), and dendritic cell- (DC) (CD11cCre Yaa) specific FcγRIIb-deficient B6.Yaa mouse strains. CD19Cre Yaa mice developed milder lupus than B6.FcγRIIb-/- Yaa mice, indicating that FcγRIIb deficiency on B cells is not sufficient for the development of severe disease. Surprisingly, C/EBPαCre Yaa mice also showed autoantibody production and mild lupus similar to that in CD19Cre Yaa mice, whereas CD11cCre Yaa mice stayed disease free. These observations indicate that FcγRIIb deficiency in B cells and myeloid cells, but not DCs, contributes to the severe disease in B6.FcγRIIb-/- Yaa mice. Flow cytometric analysis showed that the frequency of peripheral Gr-1- but not Gr-1+ monocyte was increased in B6.FcγRIIb-/- Yaa and C/EBPαCre Yaa but not CD19Cre Yaa mice, suggesting a link between FcγRIIb deficiency on myeloid cells and the high frequency of Gr-1- monocytes. RNA sequencing revealed that compared with Gr-1+ monocytes, Gr-1- monocytes expressed higher levels of the B cell-stimulating cytokines BSF-3, IL-10, and IL-1ß, the DC markers CD11c, CD83, and Adamdec1, and the antiapoptotic factors Bcl2 and Bcl6. In conclusion, in Yaa-associated lupus nephritis, FcγRIIb on B cells and myeloid cells modulates B cell activation via different but synergistic pathways. Gr-1- monocytes are the most likely candidate myeloid cells involved.

Label-Free Imaging of Melanoma with Confocal Photothermal Microscopy: Differentiation between Malignant and Benign Tissue.

Label-free confocal photothermal (CPT) microscopy was utilized for the first time to investigate malignancy in mouse skin cells. Laser diodes (LDs) with 405 nm or 488 nm wavelengths were used as pumps, and a 638 nm LD was used as a probe for the CPT microscope. A Grey Level Cooccurrence Matrix (GLCM) for texture analysis was applied to the CPT images. Nine GLCM parameters were calculated with definite definitions for the intracellular super-resolved CPT images, and the parameters Entropy, Contrast, and Variance were found to be most suited among the nine parameters to discriminate clearly between healthy cells and malignant cells when a 405 nm pump was used. Prominence, Variance, and Shade were most suited when a pump wavelength of 488 nm was used.

A study of CDR3 loop dynamics reveals distinct mechanisms of peptide recognition by T-cell receptors exhibiting different levels of cross-reactivity.

T-cell receptors (TCRs) can productively interact with many different peptides bound within the MHC binding groove. This property varies with the level of cross-reactivity of TCRs; some TCRs are particularly hyper cross-reactive while others exhibit greater specificity. To elucidate the mechanism behind these differences, we studied five TCRs in complex with the same class II MHC (1Ab )-peptide (3K), that are known to exhibit different levels of cross-reactivity. Although these complexes have similar binding affinities, the interface areas between the TCR and the peptide-MHC (pMHC) differ significantly. We investigated static and dynamic structural features of the TCR-pMHC complexes and of TCRs in a free state, as well as the relationship between binding affinity and interface area. It was found that the TCRs known to exhibit lower levels of cross-reactivity bound to pMHC using an induced-fitting mechanism, forming large and tight interfaces rich in specific hydrogen bonds. In contrast, TCRs known to exhibit high levels of cross-reactivity used a more rigid binding mechanism where non-specific π-interactions involving the bulky Trp residue in CDR3ß dominated. As entropy loss upon binding in these highly degenerate and rigid TCRs is smaller than that in less degenerate TCRs, they can better tolerate changes in residues distal from the major contacts with MHC-bound peptide. Hence, our dynamics study revealed that differences in the peptide recognition mechanisms by TCRs appear to correlate with the levels of T-cell cross-reactivity.

Gray-level co-occurrence matrix analysis of several cell types in mouse brain using resolution-enhanced photothermal microscopy.

Qualifications of intracellular structure were performed for the first time using the gray-level co-occurrence matrix (GLCM) method for images of cells obtained by resolution-enhanced photothermal imaging. The GLCM method has been used to extract five parameters of texture features for five different types of cells in mouse brain; pyramidal neurons and glial cells in the basal nucleus (BGl), dentate gyrus granule cells, cerebellar Purkinje cells, and cerebellar granule cells. The parameters are correlation, contrast, angular second moment (ASM), inverse difference moment (IDM), and entropy for the images of cells of interest in a mouse brain. The parameters vary depending on the pixel distance taken in the analysis method. Based on the obtained results, we identified that the most suitable GLCM parameter is IDM for pyramidal neurons and BGI, granule cells in the dentate gyrus, Purkinje cells and granule cells in the cerebellum. It was also found that the ASM is the most appropriate for neurons in the basal nucleus.

Noninvasive, label-free, three-dimensional imaging of melanoma with confocal photothermal microscopy: Differentiate malignant melanoma from benign tumor tissue.

Skin cancer is one of the most common cancers. Melanoma accounts for less than 2% of skin cancer cases but causes a large majority of skin cancer deaths. Early detection of malignant melanoma remains the key factor in saving lives. However, the melanoma diagnosis is still clinically challenging. Here, we developed a confocal photothermal microscope for noninvasive, label-free, three-dimensional imaging of melanoma. The axial resolution of confocal photothermal microscope is ~3 times higher than that of commonly used photothermal microscope. Three-dimensional microscopic distribution of melanin in pigmented lesions of mouse skin is obtained directly with this setup. Classic morphometric and fractal analysis of sixteen 3D images (eight for benign melanoma and eight for malignant) showed a capability of pathology of melanoma: melanin density and size become larger during the melanoma growth, and the melanin distribution also becomes more chaotic and unregulated. The results suggested new options for monitoring the melanoma growth and also for the melanoma diagnosis.

Reduction of distortion in photothermal microscopy and its application to the high-resolution three-dimensional imaging of nonfluorescent tissues.

A scheme for reducing image distortion in photothermal microscopy is presented. In photothermal microscopy, the signal shape exhibits twin peaks corresponding to the focusing or defocusing of the probe beam when a sample is scanned in the axial direction. This causes a distortion when imaging a structured sample in the axial plane. Here, we demonstrate that image distortion caused by the twin peaks is effectively suppressed by providing a small offset between two the focal planes of the pump and the probe beams. Experimental results demonstrate improvement in resolution, especially in the axial direction, over conventional optical microscopy-even with the focal offset. When a dry objective lens with a numerical aperture of 0.95 is used, the full width at half the maximum of the axial point spread function is 0.6 µm, which is 50% (62%) smaller than the focal spot sizes of the pump (probe) beam. Herein, we present high-resolution three-dimensional imaging of thick biological tissues based on the present scheme.

Biological imaging with nonlinear photothermal microscopy using a compact supercontinuum fiber laser source.

Nonlinear photothermal microscopy is applied in the imaging of biological tissues stained with chlorophyll and hematoxylin. Experimental results show that this type of organic molecules, which absorb light but transform dominant part of the absorbed energy into heat, may be ideal probes for photothermal imaging without photochemical toxicity. Picosecond pump and probe pulses, with central wavelengths of 488 and 632 nm, respectively, are spectrally filtered from a compact supercontinuum fiber laser source. Based on the light source, a compact and sensitive super-resolution imaging system is constructed. Further more, the imaging system is much less affected by thermal blurring than photothermal microscopes with continuous-wave light sources. The spatial resolution of nonlinear photothermal microscopy is ~ 188 nm. It is ~ 23% higher than commonly utilized linear photothermal microscopy experimentally and ~43% than conventional optical microscopy theoretically. The nonlinear photothermal imaging technology can be used in the evaluation of biological tissues with high-resolution and contrast.

Label-free imaging of melanoma with nonlinear photothermal microscopy.

Nonlinear photothermal microscopy, in which the intensity of the pump heating beam is modulated at f and the photothermal signal is extracted from the probe beam with a lock-in amplifier referred to 2f, is applied to the imaging of mouse melanoma without any staining. The pump and probe pulses, with central wavelengths of 488 and 632 nm, and a pulse duration of ∼100 ps, are filtered from a compact commercial supercontinuum fiber laser source. An auto-balanced detector is applied to accumulate the signal and remove the laser noise of the probe. The spatial resolution of the nonlinear photothermal imaging is enhanced by ∼18% in both theoretical calculations and experiments, compared with a linear photothermal mechanism, and the resolution enhancement is theoretically ∼42% compared with conventional optical microscopy. This imaging technique shows possibilities for the clinical evaluation of melanoma with a high contrast and spatial resolution.

Simultaneous dual-wavelength imaging of nonfluorescent tissues with 3D subdiffraction photothermal microscopy.

Multi-wavelength microscopic imaging is essential to visualize a variety of nanoscale cellular components with high specificity and high spatial resolution. However, previous techniques are based on fluorescence, and thus cannot visualize nonfluorescent species, which are much less suffered from photodamage or photobleaching and hence are intrinsically useful in wider range of optical microscopy. Here, we show that simultaneous multi-wavelength imaging of nonfluorescent species can be achieved with the use of a photothermal microscope. Dual-wavelength subdiffraction imaging of biological tissues stained with hematoxylin and eosin is demonstrated. Three-dimensional label-free imaging of mouse melanoma tissue section is also presented to demonstrate the effectiveness of the enhanced spatial resolution. Our technique can be implemented using cost-effective and compact laser diodes and is applicable for various types of both fluorescent and nonfluorescent tissues.

"Optimal detection angle in sub-diffraction resolution photothermal microscopy: application for high sensitivity imaging of biological tissues": reply.

The differences between our model and existing models are rationalized in terms of the experimental conditions. The theory in [Opt. Express 22(16), 18833-18842 (2014)] is applicable when the temperature increase is moderate (~1 K) and the spatial extend of refractive index being modulated is comparable to or smaller than the wavelength, which are in accordance with our experiment.

Sensitivity enhancement of photothermal microscopy with radially segmented balanced detection.

A novel detection method is proposed for highly sensitive photothermal microscopic imaging. This method is based on the characteristics of an angular-dependent photothermal signal; it improves signal intensity by up to two times and rejects the intensity noise of the probe beam. The subdiffraction resolution photothermal imaging of mouse skin melanoma is demonstrated using a laser diode-based photothermal microscopy system to evaluate this method. We confirm that the signal intensity is enhanced 1.7 times compared with the conventional detection method. Moreover, the intensity noise of the laser diode used for the probe beam is effectively reduced by approximately 31 dB, even for a sample with non-uniformity of the refractive index and stationary absorption. This method is implemented by means of a commonly used balanced detector and is thus potentially useful for high-speed imaging.

IL-6 signal blockade ameliorates the enhanced osteoclastogenesis and the associated joint destruction in a novel FcγRIIB-deficient rheumatoid arthritis mouse model.

OBJECTIVE: We earlier found that TNFα but not interleukin (IL)-17 is indispensable in the pathogenesis of spontaneously occurring rheumatoid arthritis (RA)-like disease in our newly established FcγRIIB-deficient C57BL/6 (B6) mouse model, designated KO1. Here, we examined the role of IL-6 in the pathogenesis of RA features in KO1, with particular reference to cartilage and bone destruction in arthritic joints. METHODS: To evaluate the preventive effect of MR16-1, a rat anti-mouse IL-6 receptor (IL-6R) mAb, 4-month-old preclinical KO1 mice were divided into three groups: the first treated with MR16-1 for 6 months, the second treated with normal rat IgG, as a control, and the third left untreated. The incidence and severity of arthritis, immunological abnormalities, and transcription levels of receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and inflammatory cytokines/chemokines in ankle joint tissues were compared among the three groups. The therapeutic effect of MR16-1 was examined by treating 7-month-old KO1 mice in the early stages of arthritis for 2 months. RESULTS: Compared with the findings in the KO1 mice left untreated or treated with normal rat IgG, the development of arthritis was markedly suppressed in mice with MR16-1 treatment started from preclinical stages. The suppression was associated with the decrease in production of autoantibodies, rheumatoid factors (RF), and anti-cyclic citrullinated peptide (CCP). Histologically, marked synovitis, pannus formation, and cartilage and bone destruction associated with the increase in tartrate-resistant acid phosphatase (TRAP)-positive osteoclast generation were evident in the two control groups; however, these findings were virtually absent in MR16-1-treated mice. Real-time PCR analysis revealed that the up-regulated expression levels of MCP-1, IL-6, and TNFα, and the aberrantly high RANKL/OPG expression ratio in synovial joint tissues from the two control groups of mice with overt arthritis were significantly suppressed in MR16-1-treated mice. In mice with therapeutic MR16-1 treatment, there was no progression in arthritis score and the RANKL/OPG ratio in joint tissues was significantly suppressed. CONCLUSIONS: Administration of an anti-IL-6R mAb ameliorated spontaneously occurring RA-like disease features, indicating that IL-6, as well as TNFα, plays a pivotal role in the pathogenesis of RA in KO1 mice. Current studies showed that, in addition to the role in enhancing autoantibody production, IL-6 promotes synovial tissue inflammation and osteoclastogenesis, leading to the severe synovitis with pannus formation and the progressive cartilage and bone destruction in multiple joints.

Optimal detection angle in sub-diffraction resolution photothermal microscopy: application for high sensitivity imaging of biological tissues.

We evaluated the optimal detection angle for maximizing the signal to noise ratio (SNR) in sub-diffraction resolution photothermal microscopy. The angular dependent photothermal signal was calculated based on scattering theory using the temporally modulated Yukawa potential, and its detection angle and modulation frequency dependencies were analyzed. We verified the theoretical findings by imaging gold nanoparticles using laser diode based photothermal microscopy with balanced detection scheme. High-sensitivity (SNR ~40) photothermal biological imaging of a mouse brain was also demonstrated.

Commensal bacteria regulate thymic Aire expression.

Commensal bacteria in gastrointestinal tracts are reported to function as an environmental factor to regulate intestinal inflammation and immune responses. However, it remains largely unknown whether such bacterial function exerts any effect on other immune organs distant from the intestine. In this study, the influence of commensal bacteria in the thymus, where T cell lineages develop into mature type to form proper repertoires, was investigated using germ-free (GF) mice and Nod1-deficient mice lacking an intracellular recognition receptor for certain bacterial components, in which a commensal bacterial effect is predicted to be less. In both mice, there was no significant difference in the numbers and subset ratios of thymocytes. Interestingly, however, autoimmune regulator (Aire) expression in thymic epithelial cells (TECs), main components of the thymic microenvironment, was decreased in comparison to specific pathogen-free (SPF) mice and Nod1 wild-type (WT) mice, respectively. In vitro analysis using a fetal thymus organ culture (FTOC) system showed that Aire expression in TECs was increased in the presence of a bacterial component or a bacterial product. These results suggest that through their products, commensal bacteria have the potential to have some effect on epithelial cells of the thymus in tissues distant from the intestine where they are originally harbored.

Sub-diffraction resolution pump-probe microscopy with shot-noise limited sensitivity using laser diodes.

We demonstrate the use of intensity-modulated laser diodes to implement pump-probe microscopy and achieved sub-diffraction resolution imaging with shot-noise limited sensitivity with a scheme of balanced detection. This technique has several applications for various types of induced transmission change, including excited-state absorption, ground state absorption bleaching and stimulated emission. By using our technique, biological imaging of mouse T cells and the axons of neurons in the cerebral cortex was demonstrated.

TNFα but not IL-17 is critical in the pathogenesis of rheumatoid arthritis spontaneously occurring in a unique FcγRIIB-deficient mouse model.

OBJECTIVE: TNFα and IL-17 have been shown to be the major inflammatory cytokines involved in the pathogenesis of rheumatoid arthritis (RA). Here, we examined the effect of these cytokines on spontaneously occurring RA in our newly established arthritis-prone FcγRIIB- deficient C57BL/6 (B6) mice, designated KO1, by introducing genetic deficiency of TNFα and IL-17 into KO1 mice. METHODS: KO1.TNFα(-/-) and KO1.IL-17(-/-) mice were established by crossing KO1 with TNFα-deficient and IL-17-deficient B6 mice, respectively. The incidence and severity of RA, cartilage and bone destruction, immunological abnormalities, and transcription levels of receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) and inflammatory cytokines/chemokines in ankle joints were compared among KO1, KO1.TNFα(-/-), and KO1.IL-17(-/-) mice. RESULTS: The development of RA was completely inhibited in KO1.TNFα(-/-) mice. In contrast, KO1.IL-17(-/-) mice unexpectedly developed severe RA comparable to KO1. Compared with those in KO1 and KO1.IL-17(-/-) mice, frequencies of peripheral monocytes, known to be containing osteoclast precursors, were significantly decreased in KO1.TNFα(-/-) mice. Intriguingly, while RANKL expression levels in ankle joints did not differ among the three strains, OPG expression levels were drastically decreased in arthritis-prone, but not arthritis-free, mice. The expression levels of inflammatory cytokines/chemokines, such as MCP-1, IL-6, and TNFα, were up-regulated in arthritis-prone mice. CONCLUSION: TNFα is indispensable while IL-17 is dispensable in the pathogenesis of RA in KO1 mice. In this model, TNFα may contribute to the development of arthritis, through mediating the increase in frequencies of osteoclast precursors in circulation and their migration into the joints, and the decrease in OPG expression, leading to the up-regulated osteoclastogenesis associated with severe cartilage and bone destruction.

Phenotype conversion from rheumatoid arthritis to systemic lupus erythematosus by introduction of Yaa mutation into FcγRIIB-deficient C57BL/6 mice.

We previously established an IgG Fc receptor IIB (FcγRIIB)-deficient C57BL/6 (B6)-congenic mouse strain (KO1), which spontaneously develops rheumatoid arthritis (RA), but not systemic lupus erythematosus (SLE). Here, we show that when Y chromosome-linked autoimmune acceleration (Yaa) mutation was introduced in KO1 strain (KO1.Yaa), the majority of KO1.Yaa mice did not develop RA, but instead did develop SLE. This phenotype conversion did not depend on autoantibody specificity, since KO1.Yaa mice, compared with KO1, showed a marked increase in serum levels of both lupus-related and RA-related autoantibodies. The increase in frequencies of CD69(+) activated B cells and T cells, and the spontaneous splenic GC formation with T follicular helper cell generation were manifest early in life of KO1.Yaa, but not KO1 and B6.Yaa, mice. Activated CD4(+) T cells from KO1.Yaa mice showed upregulated production of IL-21 and IL-10, compared with the finding in KO1 mice, indicating the possibility that this aberrant cytokine milieu relates to the disease phenotype conversion. Thus, our model is useful to clarify the shared and the disease-specific mechanisms underlying the clinically distinct systemic autoimmune diseases RA and SLE.

Lissencephaly with marked ventricular dilation, agenesis of corpus callosum, and cerebellar hypoplasia caused by TUBA1A mutation.

We described the clinical course and pathological findings in a child with TUBA1A mutation. MRI revealed marked ventricular dilation with thin cortex, poorly differentiated basal ganglia, agenesis of corpus callosum, cerebellar hypoplasia with preserved vermis at 2 months of age. No gain of developmental milestones was observed until she died with respiratory failure at 23 months of age. A de novo missense mutation of c.1096G>A (G366R) was identified in TUBA1A gene. Pathological findings included a lack in lamination in the cerebral cortex, absent corpus callosum without Probst bundle, blurred demarcation among the striatum, internal capsule and globus pallidus in association with irregular running of myelinated fibers, cerebellar hypoplasia with irregular undulation in the dentate nucleus and inferior olivary nucleus, absent olfactory bulbs and tracts, and pyramidal tract hypoplasia. These findings are consistent with previous reports and will be a clue to diagnosis of TUBA1A mutation.

Transgenic overexpression of G5PR that is normally augmented in centrocytes impairs the enrichment of high-affinity antigen-specific B cells, increases peritoneal B-1a cells, and induces autoimmunity in aged female mice.

To investigate signals that control B cell selection, we examined expression of G5PR, a regulatory subunit of the serine/threonine protein phosphatase 2A, which suppresses JNK phosphorylation. G5PR is upregulated in activated B cells, in Ki67-negative centrocytes at germinal centers (GCs), and in purified B220(+)Fas(+)GL7(+) mature GC B cells following Ag immunization. G5PR rescues transformed B cells from BCR-mediated activation-induced cell death by suppression of late-phase JNK activation. In G5PR-transgenic (G5PR(Tg)) mice, G5PR overexpression leads to an augmented generation of GC B cells via an increase in non-Ag-specific B cells and a consequent reduction in the proportion of Ag-specific B cells and high-affinity Ab production after immunization with nitrophenyl-conjugated chicken γ-globulin. G5PR overexpression impaired the affinity-maturation of Ag-specific B cells, presumably by diluting the numbers of high-affinity B cells. However, aged nonimmunized female G5PR(Tg) mice showed an increase in the numbers of peritoneal B-1a cells and the generation of autoantibodies. G5PR overexpression did not affect the proliferation of B-1a and B-2 cells but rescued B-1a cells from activation-induced cell death in vitro. G5PR might play a pivotal role in B cell selection not only for B-2 cells but also for B-1 cells in peripheral lymphoid organs.