Plasma cells and their secreted antibodies play a central role in the long-term protection against chronic viral infection. However, due to experimental limitations, a comprehensive description of linked genotypic, phenotypic, and antibody repertoire features of plasma cells (gene expression, clonal frequency, virus specificity, and affinity) has been challenging to obtain. To address this, we performed single-cell transcriptome and antibody repertoire sequencing of the murine BM plasma cell population following chronic lymphocytic choriomeningitis virus infection. Our single-cell sequencing approach recovered full-length and paired heavy-and light-chain sequence information for thousands of plasma cells and enabled us to perform recombinant antibody expression and specificity screening. Antibody repertoire analysis revealed that, relative to protein immunization, chronic infection led to increased levels of clonal expansion, class-switching, and somatic variants. Furthermore, antibodies from the highly expanded and class-switched (IgG) plasma cells were found to be specific for multiple viral antigens and a subset of clones exhibited cross-reactivity to nonviral and autoantigens. Integrating single-cell transcriptome data with antibody specificity suggested that plasma cell transcriptional phenotype was correlated to viral antigen specificity. Our findings demonstrate that chronic viral infection can induce and sustain plasma cell clonal expansion, combined with significant somatic hypermutation, and can generate cross-reactive antibodies.

Plasma cells and their secreted antibodies play a central role in the long-term protection against chronic viral infection. However, due to experimental limitations, a comprehensive description of linked genotypic, phenotypic, and antibody repertoire features of plasma cells (gene expression, clonal frequency, virus specificity, and affinity) has been challenging to obtain. To address this, we performed single-cell transcriptome and antibody repertoire sequencing of the murine bone marrow plasma cell population following chronic lymphocytic choriomeningitis virus infection. Our single-cell sequencing approach recovered full-length and paired heavy and light chain sequence information for thousands of plasma cells and enabled us to perform recombinant antibody expression and specificity screening. Antibody repertoire analysis revealed that, relative to protein immunization, chronic infection led to increased levels of clonal expansion, class-switching, and somatic variants. Furthermore, antibodies from the highly expanded and class-switched (IgG) plasma cells were found to be specific for multiple viral antigens and a subset of clones exhibited cross-reactivity to non-viral- and auto-antigens. Integrating single-cell transcriptome data with antibody specificity suggested that plasma cell transcriptional phenotype was correlated to viral antigen specificity. Our findings demonstrate that chronic viral infection can induce and sustain plasma cell clonal expansion, combined with significant somatic hypermutation, and can generate cross-reactive antibodies. Graphical abstract.Single-cell sequencing reveals clonally expanded plasma cells during chronic viral infection produce virus-specific and cross-reactive antibodies.

BackgroundDementia is becoming a relevant problem worldwide. A simple screening at an early stage will be important to detect the risk of developing dementia. Vestibular dysfunction is likely to be associated with cognitive impairment. Since head-mounted display (HMD) virtual reality (VR) technology has the potential to activate the vestibular function, assessing postural sway with visual stimulation using HMD VR technology could be potentially useful for dementia screening.ObjectiveThe purpose of this study is to evaluate the effect of HMD-based VR visual stimuli on posture in older adults and the relationship between the stimulated body sway behaviors and cognitive performance.MethodUsing a cross-sectional study design, we investigated the effect of an optokinetic design-based room with stripes (OKR) VR environment oscillating forwards and backwards at 23/60Hz. Center of pressure (COP) displacement was measured in older adults aged 65 years and over in the OKR VR environment. The frequency response of COP was compared to the cognitive performance of the Montreal Cognitive Assessment (MoCA).Results20 healthy older adults (70.4 ± 4.9 years; 27.2 ± 1.6 MoCA score) and 3 people with mild cognitive impairment (74.7 ± 4.0 years; 20.3 ± 2.1 MoCA score) were assessed. The results reveal that the oscillating OKR VR environment induced different postural sway in the anterior-posterior direction in the real world. Correlation analysis shows that the cognitive test score was associated with the frequency response of stimulated postural sway in the anterior-posterior direction (frequency Band 1 of 0−0.5Hz related to the visual and vestibular systems: rs = 0.45, P = 0.03).ConclusionOutcomes would suggest that a potential link may emerge between cognition and posture when the HMD-based VR visual stimuli are applied. The simple screening of stimulated postural sway could explain cognitive functioning. Further studies are warranted to clarify the vestibular system and spatial cognitive function more specifically in the proposed assessment system.

Postural sway and eye movements are potential biomarkers for dementia screening. Assessing the two movements comprehensively could improve the understanding of complicated syndrome for more accurate screening. The purpose of this research is to evaluate the effects of comprehensive assessment in healthy older adults (OA), using a novel concurrent comprehensive assessment system consisting of stabilometer and virtual reality headset. 20 healthy OA (70.4 ± 4.9 years) were recruited. Using a cross-sectional study design, this study investigated the effects of various dual-tasking paradigms with integrated tasks of visuospatial memory (VM), spatial orientation (SO), and visual challenge on posture and saccades. Dual-task paradigms with VM and SO affected the saccadic eye movements significantly. Two highly intensive tests of anti-saccade with VM task and pro-saccade with SO task also influenced postural sway significantly. Strong associations were seen between postural sway and eye movements for the conditions where the two movements theoretically shared common neural pathways in the brain, and vice versa. This study suggests that assessing posture and saccades with the integrated tasks comprehensively and simultaneously could be useful to explain different functions of the brain. The results warrant a cross-sectional study in OA with and without dementia to explore differences between these groups.

BackgroundWhile single assessment of postural sway or saccadic eye movements is potentially useful for dementia screening at clinical settings [1, 2], multimodal assessment of the two movements could improve the screening accuracy [3‐5]. We have developed a novel comprehensive assessment system of posture and saccades, with integrated additional cognitive tasks of visuospatial memory and spatial orientation. We hypothesised that the new system would improve the classification of mild cognitive impairment (MCI).Method23 older adults joined the experiment and were split into two group based on the score of Montreal Cognitive Assessment (MoCA) [6]: 20 healthy older adults (HA) (70.35±4.93 years, 11 men / 9 women) and 3 older adults with MCI (74.7±4.04 years, 1 man / 2 women). The assessment system consists of stabilometer (GP‐5000, ANIMA Corporation, Japan) and a head‐mounted display virtual reality (VR) technology (VIVE Pro Eye, HTC Corporation, Taiwan). We measured postural sway and pro‐ or anti‐saccadic eye movements simultaneously in each of three different VR environments: #1) no additional cognitive task, #2) with visuospatial memory task, and #3) with spatial orientation task. We compared the parameters of saccades and postural sway between HA and MCI groups.ResultHA group achieved the MoCA score of 27.2±1.64, while MCI group scored 20.3±2.08 (P=0.006). Our analysis did not find significant differences between the two groups in all parameters. However, we observed moderate effect on standard deviation of centre of pressure in medio‐lateral direction in two test conditions: 1) the condition with pro‐saccade and visuospatial memory tasks (P=0.14; effect size = 0.32) and 2) the condition with anti‐saccade and spatial orientation tasks (P=0.09; effect size = 0.36).ConclusionModerate effect was observed on postural sway behaviours in the two test conditions. Since these conditions theoretically activate wider areas of the brain, our comprehensive assessment approach could be useful for dementia screening. Future research requires more sample size of MCI population for further analysis.