Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the global COVID-19 pandemic. Rapidly spreading SARS-CoV-2 variants may jeopardize newly introduced antibody and vaccine ...countermeasures. Here, using monoclonal antibodies (mAbs), animal immune sera, human convalescent sera and human sera from recipients of the BNT162b2 mRNA vaccine, we report the impact on antibody neutralization of a panel of authentic SARS-CoV-2 variants including a B.1.1.7 isolate, chimeric strains with South African or Brazilian spike genes and isogenic recombinant viral variants. Many highly neutralizing mAbs engaging the receptor-binding domain or N-terminal domain and most convalescent sera and mRNA vaccine-induced immune sera showed reduced inhibitory activity against viruses containing an E484K spike mutation. As antibodies binding to spike receptor-binding domain and N-terminal domain demonstrate diminished neutralization potency in vitro against some emerging variants, updated mAb cocktails targeting highly conserved regions, enhancement of mAb potency or adjustments to the spike sequences of vaccines may be needed to prevent loss of protection in vivo.
Abstract only
Alzheimer’s disease (AD) is associated with gradual memory decline and impairment of cognitive ability. The majority of AD patients also suffer from multiple apneas during sleep. The ...sleep‐disordered breathing entails a reduced ability to adjust respiration during low oxygen (hypoxia) and/or increased carbon dioxide (hypercapnia) conditions, indicating dysfunction of the respiratory system.
In this study, we measured respiratory responses of the Streptozotocin (STZ) ‐induced rat model of AD to hypoxia (10% O
2
‐ peripheral chemoreflex) and hypercapnia (7% CO
2
‐ central chemoreflex). Measurements were taken at three weeks (early stage) and three months (late stage) following STZ injection into the lateral ventricles of the brain (2 mg/kg STZ; 6‐week‐old rats, N = 6/group).
Three weeks following AD induction, hypoxic exposure increased respiratory rate (RR) of vehicle control (CTL) and STZ‐AD rats. However, this increase was significantly blunted by ~25% in STZ‐AD. The blunted response was partial compensation by increased tidal volume (TV) resulting in a non‐significant decrease of minute ventilation (MV; RR x TV). Three months following AD induction, STZ‐AD rats still had a blunted response of RR to hypoxia, which was similar in magnitude to that observed at 3 weeks. However, at this late time point, baseline RR and MV at normoxia (21% O
2
) appeared higher in STZ‐AD than those in CTL. Comparing data between time points (3 weeks AD vs. 3 months AD), both groups showed the expected age‐dependent increase in TV and decrease of RR. This decrease in RR was less in STZ‐AD than that in CTL, but the increase in TV was similar in both groups. Thus, STZ‐AD rats had a ~15% higher MV at the 3 months’ time point than at 3 weeks. CTL rats, on the other hand, had similar MV at both ages (~0% change).
With exposure to 7% CO
2
, responses for RR, TV, and MV at 3 weeks were similar between CTL and STZ‐AD rats. Also at 3 months responses did not differ between groups. However, within the STZ‐AD group, MV at 3 months was significantly greater in response to hypercapnia than that at the younger age. This increase was due to the absent age‐dependent drop of RR in STZ‐AD. CTL rats, in contrast, had significantly reduced RR at 3 months, leading to comparable MV at both ages.
In summary, major changes were observed in the peripheral chemoreflex of STZ‐AD rats throughout our 3‐months observation period. Both, responses to hypoxia (short‐term) and baseline values of respiration under normoxia (long‐term) were altered in these animals. Central chemoreflex function, on the other hand, remained largely unaltered.
Support or Funding Information
Conference Travel Scholarship by Truman State University to M Thapa and seed money from A.T. Still University to TDO
SARS-CoV-2 mRNA-based vaccines are about 95% effective in preventing COVID-19
. The dynamics of antibody-secreting plasmablasts and germinal centre B cells induced by these vaccines in humans remain ...unclear. Here we examined antigen-specific B cell responses in peripheral blood (n = 41) and draining lymph nodes in 14 individuals who had received 2 doses of BNT162b2, an mRNA-based vaccine that encodes the full-length SARS-CoV-2 spike (S) gene
. Circulating IgG- and IgA-secreting plasmablasts that target the S protein peaked one week after the second immunization and then declined, becoming undetectable three weeks later. These plasmablast responses preceded maximal levels of serum anti-S binding and neutralizing antibodies to an early circulating SARS-CoV-2 strain as well as emerging variants, especially in individuals who had previously been infected with SARS-CoV-2 (who produced the most robust serological responses). By examining fine needle aspirates of draining axillary lymph nodes, we identified germinal centre B cells that bound S protein in all participants who were sampled after primary immunization. High frequencies of S-binding germinal centre B cells and plasmablasts were sustained in these draining lymph nodes for at least 12 weeks after the booster immunization. S-binding monoclonal antibodies derived from germinal centre B cells predominantly targeted the receptor-binding domain of the S protein, and fewer clones bound to the N-terminal domain or to epitopes shared with the S proteins of the human betacoronaviruses OC43 and HKU1. These latter cross-reactive B cell clones had higher levels of somatic hypermutation as compared to those that recognized only the SARS-CoV-2 S protein, which suggests a memory B cell origin. Our studies demonstrate that SARS-CoV-2 mRNA-based vaccination of humans induces a persistent germinal centre B cell response, which enables the generation of robust humoral immunity.
Germinal centres (GC) are lymphoid structures in which B cells acquire affinity-enhancing somatic hypermutations (SHM), with surviving clones differentiating into memory B cells (MBCs) and long-lived ...bone marrow plasma cells
(BMPCs). SARS-CoV-2 mRNA vaccination induces a persistent GC response that lasts for at least six months in humans
. The fate of responding GC B cells as well as the functional consequences of such persistence remain unknown. Here, we detected SARS-CoV-2 spike protein-specific MBCs in 42 individuals who had received two doses of the SARS-CoV-2 mRNA vaccine BNT162b2 six month earlier. Spike-specific IgG-secreting BMPCs were detected in 9 out of 11 participants. Using a combined approach of sequencing the B cell receptors of responding blood plasmablasts and MBCs, lymph node GC B cells and plasma cells and BMPCs from eight individuals and expression of the corresponding monoclonal antibodies, we tracked the evolution of 1,540 spike-specific B cell clones. On average, early blood spike-specific plasmablasts exhibited the lowest SHM frequencies. By contrast, SHM frequencies of spike-specific GC B cells increased by 3.5-fold within six months after vaccination. Spike-specific MBCs and BMPCs accumulated high levels of SHM, which corresponded with enhanced anti-spike antibody avidity in blood and enhanced affinity as well as neutralization capacity of BMPC-derived monoclonal antibodies. We report how the notable persistence of the GC reaction induced by SARS-CoV-2 mRNA vaccination in humans culminates in affinity-matured long-term antibody responses that potently neutralize the virus.
In this study we profiled vaccine-induced polyclonal antibodies as well as plasmablast-derived mAbs from individuals who received SARS-CoV-2 spike mRNA vaccine. Polyclonal antibody responses in ...vaccinees were robust and comparable to or exceeded those seen after natural infection. However, the ratio of binding to neutralizing antibodies after vaccination was greater than that after natural infection and, at the monoclonal level, we found that the majority of vaccine-induced antibodies did not have neutralizing activity. We also found a co-dominance of mAbs targeting the NTD and RBD of SARS-CoV-2 spike and an original antigenic-sin like backboost to spikes of seasonal human coronaviruses OC43 and HKU1. Neutralizing activity of NTD mAbs but not RBD mAbs against a clinical viral isolate carrying E484K as well as extensive changes in the NTD was abolished, suggesting that a proportion of vaccine-induced RBD binding antibodies may provide substantial protection against viral variants carrying single E484K RBD mutations.
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•Antibody responses after SARS-CoV-2 mRNA vaccination target RBD, NTD, and S2•SARS-CoV-2 mRNA vaccination induces a high rate of non-neutralizing antibodies•Crossreactive antibodies to seasonal β-coronaviruses are induced by vaccination•Variant mutation N501Y enhances affinity to human ACE2 while E484K reduces it
An analysis of mRNA vaccine-induced polyclonal antibodies and plasmablast-derived monoclonal antibodies from individuals vaccinated against SARS-CoV-2 identifies a high proportion of non-neutralizing antibodies and the induction of cross-reactive antibodies to seasonal coronaviruses and also maps the regions in the spike protein that are targeted, even among viral variants.
Abstract only
Alzheimer’s disease (AD) is associated with deterioration of memory and cognition due to changes in brain areas important for these functions. The majority of AD patients also suffer ...multiple episodes of breathing cessations (apneas) during sleep. AD‐related sleep apnea may be associated with the decline of brainstem centers that control breathing and chemoreflex function. The nucleus tractus solitarii (nTS) is a key region for respiratory control and any AD‐related deterioration of this nucleus critically impacts its function.
In this study, we used the streptozotocin (STZ) ‐induced rat model for sporadic AD (6‐week old rats, N = 6–8 rats/group) and compared chemoreflex dysfunction to indices of morphological alterations in the nTS. Particularly, we compared data obtained two weeks following injections of either 2 mg/kg or 2× 1.5 mg/kg STZ. Peripheral chemoreflex function was tested with 10% O
2
in a plethysmography chamber. While increased respiratory rate thirty minutes into hypoxia was significantly blunted with both STZ dosages, animals receiving 2 mg/kg STZ partially compensated with larger tidal volumes. Hence, minute ventilation (rate x volume) was only significantly decreased in animals that received 2× 1.5 mg/kg STZ. Consistent with previously published data analyzing memory dysfunction in this model, there was a trend for reduced overall hippocampal size for both STZ concentrations. Immunohistochemical analysis of neuronal density (Anti‐NeuN antibody) in the CA1 region showed no difference between both STZ concentrations and control. However, synaptic density (Anti‐Synaptophysin antibody) was significantly reduced in both STZ concentrations. The overall size of the caudal nTS (4 sections each 180 μm apart) in the brainstem exhibited a greater reduction in 2× 1.5 mg/kg STZ. NeuN density was not altered between STZ concentrations and control. Interestingly, despite the stronger decline of chemoreflex function and nTS size with 2× 1.5 mg/kg STZ, synaptic density in the nTS (calamus scriptorius area) yielded a significant reduction for 2 mg/kg STZ only.
Our study shows that reduced nTS size and synaptic density may be underlying the early changes of chemoreflex dysfunction in this model of sporadic AD. 2× 1.5 mg/kg STZ seemed to have a greater impact on respiratory function and nTS size. However, the varying change in synaptic density of each STZ concentration may be due to regional differences, since nTS size at calamus scriptorius did not differ between groups. Future studies will incorporate analysis of more caudal and rostral sections.
Support or Funding Information
TruScholar and MoLSAMP grant from Truman State University (TSU) to CMH, GIASR from TSU to MW, seed money from A.T. Still University to TDO
•Alzheimer’s disease (AD) is highly associated with respiratory dysfunction.•Brainstem pathology corroborates respiratory problems in the STZ model of AD.•Regional atrophy is found in a respiratory ...brainstem area.•Reduced synapses and gliosis may initiate respiratory dysfunction in STZ-AD.
Obstructive sleep apnea is highly prevalent in Alzheimer’s disease (AD). However, brainstem centers controlling respiration have received little attention in AD research, and mechanisms behind respiratory dysfunction in AD are not understood. The nucleus tractus solitarii (nTS) is an important brainstem center for respiratory control and chemoreflex function. Alterations of nTS integrity, like those shown in AD patients, likely affect neuronal processing and adequate control of breathing. We used the streptozotocin-induced rat model of AD (STZ-AD) to analyze cellular changes in the nTS that corroborate previously documented respiratory dysfunction. We used 2 common dosages of STZ (2 and 3 mg/kg STZ) for model induction and evaluated the early impact on cell populations in the nTS. The hippocampus served as control region to identify site-specific effects of STZ. There was significant atrophy in the caudal nTS of the 3 mg/kg STZ-AD group only, an area known to integrate chemoafferent information. Also, the hippocampus had significant atrophy with the highest STZ dosage tested. Both STZ-AD groups showed respiratory dysfunction along with multiple indices for astroglial and microglial activation. These changes were primarily located in the caudal and intermediate nTS. While there was no change of astrocytes in the hippocampus, microglial activation was accompanied by a reduction in synaptic density. Together, our data demonstrate that STZ-AD induces site-specific effects on all major cell types, primarily in the caudal/intermediate nTS. Both STZ dosages used in this study produced a similar outcome and can be used for future studies examining the initial symptoms of STZ-AD.
The emergence of SARS-CoV-2 antigenic variants with increased transmissibility is a public health threat. Some variants show substantial resistance to neutralization by SARS-CoV-2 infection- or ...vaccination-induced antibodies. Here, we analyzed receptor binding domain-binding monoclonal antibodies derived from SARS-CoV-2 mRNA vaccine-elicited germinal center B cells for neutralizing activity against the WA1/2020 D614G SARS-CoV-2 strain and variants of concern. Of five monoclonal antibodies that potently neutralized the WA1/2020 D614G strain, all retained neutralizing capacity against the B.1.617.2 variant, four also neutralized the B.1.1.7 variant, and only one, 2C08, also neutralized the B.1.351 and B.1.1.28 variants. 2C08 reduced lung viral load and morbidity in hamsters challenged with the WA1/2020 D614G, B.1.351, or B.1.617.2 strains. Clonal analysis identified 2C08-like public clonotypes among B cells responding to SARS-CoV-2 infection or vaccination in 41 out of 181 individuals. Thus, 2C08-like antibodies can be induced by SARS-CoV-2 vaccines and mitigate resistance by circulating variants of concern.
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•2C08 is a germinal center B cell-derived anti-SARS-CoV-2 human monoclonal antibody•2C08 protects hamsters against challenge with B.1.351 and B.1.617.2 SARS-CoV-2 strains•2C08 recognizes a conserved epitope in the receptor-binding domain of SARS-CoV-2 spike•2C08-like clonotypes are induced after SARS-CoV-2 infection and vaccination in humans
SARS-CoV-2 variants with increased transmissibility are a public health threat. Schmitz et al. characterize 2C08, a human monoclonal antibody derived from a SARS-CoV-2 vaccine-induced germinal center B cell. 2C08 possesses a broad and potent neutralization capacity and protects hamsters against challenge with D614G, B.1.351, or B.1.617.2 strains. Public 2C08-like clones can be elicited by both SARS-CoV-2 infection and vaccination.
Background
Alzheimer's disease (AD) is the most common cause of dementia and clinically diagnosed largely based on cognitive decline. Most AD patients also present with disorders of respiration, ...swallowing, and autonomic function. Current studies suggest that pathological changes in the brainstem manifest simultaneously or even before those in forebrain regions, and may account for non‐cognitive symptoms. Identifying the pathologic changes in brainstem centers may elucidate the mechanisms behind cardiorespiratory dysfunction in AD. This study concentrated on the respiratory deficits. Using the streptozotocin (STZ)‐induced model of AD, we determined cell activation in response to acute hypoxia in the nucleus tractus solitarii (nTS), a brainstem area that is integral for chemoreflex function.
Methods
Sporadic AD was induced in Sprague Dawley rats (280 ± 17g, n = 6 rats/group) by intracerebroventricular injections of streptozotocin (1.5 mg/kg STZ in citrate buffer; day 1 and 3). Vehicle injections served as control (CTL). Peripheral chemoreflex function was tested with two hours of acute hypoxia (10% O2) in a plethysmography chamber. Immediately following the hypoxic period, the brains were fixed with 4% paraformaldehyde. Four representative areas of the nTS were immunohistochemically analyzed for cell activation (c‐Fos).
Results
The chemoreflex‐mediated increase of minute ventilation in response to acute hypoxia was significantly blunted by ~20% in STZ rats when compared to CTL (p = 0.03). The diminished response continued over the entire 2 hours of hypoxia and was mainly due to alterations in respiratory rate. Immunohistochemical analysis revealed a ~25% decrease of hypoxia‐mediated cell activation in the medial nTS of STZ rats (−14.04 mm from bregma, p = 0.02). This decline in cell activation was not due to a general decrease in cell density as shown by DAPI staining. The level of activation in commissural and rostral nTS sections was not different from CTL.
Conclusion
We had previously found respiratory dysregulation in the STZ model of sporadic AD. This follow‐up study analyzed respiratory parameters over a two‐hour hypoxic period and the underlying pattern of cell activation in the nTS. Our data document a reduced activation of the medial nTS in the chemoreflex pathway of AD rats. This finding may help explain the respiratory symptoms observed in AD patients.
This is from the Experimental Biology 2018 Meeting. There is no full text article associated with this published in The FASEB Journal.
Besides impairment in cognition and memory, patients with Alzheimer's disease (AD) often exhibit marked dysfunction in respiratory control. Sleep-disordered breathing (SDB) is commonly found in cases ...of AD, resulting in periods of hypoxia during sleep. Early structural changes in brainstem areas controlling respiratory function may account for SDB in the course of AD. However, to date the underlying mechanisms for these complications are not known. The streptozotocin (STZ)-induced rat model of AD exhibits abnormal responses to hypoxia and increased astrogliosis in a key region for respiratory control. In this study we further defined the pathophysiological respiratory response of STZ-AD rats to 10% O2. In addition, we analyzed hypoxia-induced neuronal activation in respiratory and cardiovascular nuclei of the dorsal and ventral brainstem. Two hours of hypoxia induced a transient increase in tidal volume that was followed by a prolonged increase in respiratory rate. Only respiratory rate was significantly blunted in the STZ-AD model, which continued over the entire duration of the hypoxic episode. Analysis of c-Fos expression as a marker for neuronal activation showed abundant labeling throughout the nTS, nuclei of the ventral respiratory column, and A1/C1 cells of cardiovascular centers in the ventral brainstem. STZ-AD rats showed a significant decrease of c-Fos labeling in the caudal/medial nTS, rostral ventral respiratory group, and Bötzinger complex. c-Fos in other respiratory centers and A1/C1 cells was unaltered when compared to control. The results of this study document a region-specific impact of STZ-induced AD in respiratory brainstem nuclei. This decrease in c-Fos expression correlates with the observed blunting of respiration to hypoxia in the STZ-AD rat model.
•Alzheimer's disease (AD) patients often experience respiratory dysfunction.•The streptozotocin-induced model of AD (STZ-AD) shows a blunted chemoreflex response to 2 hours of acute hypoxia.•c-Fos expression in STZ-AD rats is reduced in specific regions of the dorsal and ventral brainstem related to respiratory control.•Hypoxia-induced c-Fos in cardiovascular nuclei of STZ-AD rats remains unchanged when compared to control.
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