Shivali Kohli

Alzheimer’s disease is a neurodegenerative condition characterized by progressive loss of memory and general decline in cognitive function. Although research has traditionally focused on the hippocampus and entorhinal cortex, other regions important for memory and spatial navigation, such as the anterior thalamic nuclei and retrosplenial cortex, are also affected. The retrosplenial cortex is an important brain region for both memory and spatial navigation, and displays dysfunction in humans during prodromal phases of Alzheimer’s Disease. The anterior thalamic nuclei provide a major input to the retrosplenial cortex, with loss of this input to the retrosplenial cortex causing a dramatic reduction in the expression of the immediate-early gene product c-Fos. The anterior thalamic nuclei to retrosplenial cortex connection may thus present a new target for therapeutic intervention in Alzheimer’s Disease. Here, we set out to determine whether Alzheimer’s-like pathology perturbed projections from the anterior thalamic nuclei to retrosplenial cortex in the hAPP-J20 amyloidopathy mouse model, using optogenetic activation of thalamic inputs combined with ex vivo patch clamp electrophysiology. We found that the retrosplenial cortex displayed an age-dependent decline in basal c-Fos activity, with no additional effect of amyloid pathology on c-Fos expression. At all-time points (3, 6 and 9 months) measured, we found no evidence of impairments in the synaptic strength or efficacy of the anterior thalamic nuclei projections to either granular or dysgranular subdivisions of the retrosplenial cortex. We conclude that, in the hAPP-J20 mouse model, this pathway is unaffected by amyloid-β overexpression.

Sub-population analyses of mass-standardised antibody responses converge from infection recovery and vaccination cohorts pointing to mechanisms of protection.

A multiplex diagnostic test is evaluated for self-reported long COVID associated persistent symptoms and a poor recovery from a SARS-CoV-2 infection. A mass-standardised concentration of total antibodies (AC), high-quality (HQ) antibodies and percentage of HQ antibodies (HQ%) is assessed against a spectrum of spike proteins to the SARS-CoV-2 variants: Wuhan, α, δ, and the Omicron variants BA.1, BA.2, BA.2.12.1, BA.2.75, BA.5, CH.1.1, BQ.1.1 and XBB.1.5 in three cohorts. A cohort of control patients ( n = 46) recovered (CC) and a cohort of self-declared long COVID patients ( n = 113) (LCC). A nested Receiver Operating Characteristic (ROC) analysis, performed for the variant with lowest HQ concentration in the spectrum, produced an area under the curve and AUC = 0.61 (0.53-0.70) for the CC vs LCC cohorts. For the LCC cohort, the cut-off thresholds for AC = 0.8 mg/L, HQ = 1.5 mg/L and HQ% of 34% were determined, leading to a 71% sensitivity and 66% specificity derived by the Youden metric. The cohorts may be fully classified based on ROC and outlier analysis to give an incidence of persistent virus 62% (95% CI 52% – 71%), hyperimmune 12% (95% CI 7% - 20%) and unclassified, 26% (95% CI 18% - 35%). The overall diagnostic accuracy for both the hyper and hypo immune is 69%. All clinical interventions can now be tailored for the heterogenous long COVID patient cohort.

A multivariant total subclass analysis has been performed for a control cohort ( n =15) and a long COVID patient cohort ( n =15) measuring the IgG1, IgG2, IgG3, IgG4 and IgE response to the following 14 variants of SARS-CoV-2: Wuhan, Alpha, Delta, BA.1, BA.2, BA.5, EG.5.1, XBB.1.5, BA.2.75, CH.1.1, BA.2.12.1, BQ.1.1, JN.1, and KP.3. Significant differences ( p < 0.05 and p < 0.005) between concentrations of IgG subclasses by variant were found in 24% of variants and in mean-normalised distributions. The medians of the mean-normalised distributions were significantly lower for IgG1 ( p < 0.05) in long COVID patients compared with controls, and significantly higher ( p < 0.005) for levels of IgG3, IgG4 and IgE for long COVID patients. A preliminary diagnostics classification analysis performed by variation of the mean-normalised upper and lower percentiles symmetrically for IgG3 showed a long COVID diagnostic sensitivity of 80%, and specificity of 80% for the 60 ^th percentile threshold of the control cohort. Three types of long COVID can be identified: patients with at least one variant below the threshold (hypo-immune), patients with at least one variant above the threshold (hyperimmune) and patients with IgG3 levels within the reference range. The multivariant subclass spectrum indicates IgG4 and IgE elevations due to potential chronic antigen exposure from persistent virus or autoimmunity and may indicate potential therapeutic interventions.

A fully mass‐standardised quantitative comparative analysis of the differential antibody binding to spike variant proteins to SARS‐CoV‐2 has been performed for the variants: Wuhan, Alpha, Beta, Gamma, Delta and the Omicron variants BA.1, BA.2.12.1, BA.2.75, BA.4 and BA.5. Evolution of immunity through five patient cohorts ( n = 148 in total) was studied including pre‐pandemic, first infection, first vaccine, second vaccine and triple‐vaccinated cohorts. A population of immunity endotypes has been observed and is classified against a recovery antibody threshold, with concentrations below this threshold being regarded as a ‘dropout’: U(+) showing protection to all variants; U(±) with single, double, triple and further dropout endotypes; and U(−) with all variant concentrations being under the threshold. The U(+) incidence rises significantly following multiple rounds of vaccination reaching an ( n = 41) incidence of 54% (95% CI 39%–68%) suggesting between half and three‐quarters of the population have universal variant vaccine antibody protection. The U(+) epitopes are targeted preferentially to the S1 region. U(±), with at least one dropout, has an incidence of 42% (95% CI 28%–57%), an immunity gap. Further, a U(−) sub‐cohort of the population up to 13% does not make antibodies above the threshold and may not have a sterilising serum leading to persistent virus and a risk of Long COVID.

Alzheimer’s disease (AD) is a neurodegenerative condition characterised by progressive loss of memory and general decline in cognitive function. Although research has traditionally focused on the hippocampus and entorhinal cortex, other regions important for memory and spatial navigation, such as the anterior thalamic nuclei (ATN) and retrosplenial cortex (RSC), are also affected. The RSC is an important brain region for both memory and spatial navigation, and displays dysfunction in humans during prodromal phases of AD. The ATN provide a major input to RSC, with loss of this input to RSC causing a dramatic reduction in the expression of the immediate early gene product c-Fos. The ATN to RSC connection may thus present a new target for therapeutic intervention in AD. Here, we set out to determine whether AD-like pathology perturbed projections from ATN to RSC using the hAPP-J20 amyloidopathy mouse model, using optogenetic activation of thalamic inputs combined with ex vivo patch clamp electrophysiology. We found that RSC displayed an age-dependent decline in basal c-Fos activity, with no additional effect of amyloid pathology on c-Fos expression. At all time points (3, 6 and 9 months) measured, we found no evidence of impairments in the synaptic strength or efficacy of the ATN projections to either granular or dysgranular subdivisions of RSC. We conclude that, in the hAPP-J20 mouse model, this pathway is unaffected by amyloid-β overexpression.

The prefrontal—hippocampal—entorhinal system is perhaps the most widely-studied circuit in cognitive and systems neuroscience, due to its role in supporting cognitive functions such as working memory and decision-making. Disrupted communication within this circuit is a key feature of disorders such as schizophrenia and dementia. Nucleus reuniens (NRe) is a midline thalamic nucleus that sits at the nexus of this circuit, linking these regions together. As there are no direct projections from prefrontal cortex to hippocampus (HPC), the accepted model is that the NRe mediates prefrontal drive of hippocampal activity, although these connections are poorly defined at the cellular and synaptic level. Using ex vivo optogenetics and electrophysiology in both mice and rats, alongside monosynaptic circuit-tracing, we sought to test the mechanisms through which NRe could drive hippocampal activity. Unexpectedly, we found no evidence that pyramidal cells in CA1 receive input from NRe, with midline thalamic input to HPC proper appearing selective for GABAergic interneurons. In other regions targeted by NRe, we found that pyramidal cells in prosubiculum and subiculum received synaptic inputs from NRe that were at least an order of magnitude weaker than those in prefrontal or entorhinal cortices. We conclude that, contrary to widely-held assumptions in the field, hippocampal pyramidal cells are not a major target of NRe.

The retrosplenial cortex (RSC) is a highly interconnected brain region involved in spatial navigation and associative learning. It forms extensive, reciprocal connections with sensory, hippocampal, parahippocampal, prefrontal, and thalamic areas. RSC comprises granular (gRSC) and dysgranular (dRSC) subdivisions with distinct connectivity and functions. Despite its emerging role in behaviour and its implication in memory-related disorders such as Alzheimer’s disease, the nature of its synaptic inputs remains poorly understood. Here, we combined viral anatomical tracing, optogenetic stimulation, and patch-clamp electrophysiology to investigate inputs from the anterior cingulate cortex (ACC), dorsal subiculum (dSub), and anterior thalamic nuclei (ATN) to gRSC and dRSC. Strikingly, all recorded RSC pyramidal neurons received ATN input, regardless of subdivision or cortical layer. Activation of ATN inputs evoked significantly larger post-synaptic responses than those from dSub or ACC, though both regions maintained substantial connectivity with RSC. While dSub projections appeared denser in gRSC, synaptic responses were larger in dRSC, albeit with lower input probability. Notably, NMDA receptor-mediated components of RSC excitatory inputs were weaker than expected, potentially explaining the reported inability to induce long-term potentiation in RSC in ex vivo neurophysiology experiments. This is the first study to characterise the synaptic properties of retrosplenial afferents. Our findings highlight the dominant influence of ATN inputs and raise important questions about how RSC’s long-range connectivity supports its roles in memory and spatial navigation.

A fully quantitative comparative analysis has been performed on the differential antibody binding to a spectrum of Spike proteins to the SARS-CoV-2 variants Wuhan, Alpha, Beta, Gamma, Delta and Omicron BA.1, BA.1, BA.4, BA.5, BA.2.75 and BA.2.12.1. The immunity profile was determined for four patient cohorts: pre-pandemic, the first infection in the pandemic, Wuhan(+), and two vaccinated cohorts, the initial double-vaccination with AstraZeneca (AZ) and Pfizer and a final boosted cohort including with known vaccination but unknown mixture of natural infection. A universal protection immunity endotype, U(+), with significant antibody levels to all ten variants was observed in with a incidence of 11% (95% CI 4% - 25%) in the Wuhan(+) cohort challenging directly the ‘one-and-done’ immunity claim. The U(+) incidence rises to 22% (95% CI 12% - 37%) in the double-vaccinated cohort and 54% (95% CI 39% - 68%) in the triple vaccinated cohort. The remaining patients in each cohort show a spectrum of immunity with some drop-out immunity endotypes, U(±), showing poor antibody response to one or more variants. The U(±) incidence in the triple vaccination cohort is 41% (95% CI 28% - 57%) suggesting patients with poor sterilising sera may not clear a SARS-CoV-2 infection leading to viral persistence and mobile microcolonies that may provide a pathophysiology for the symptoms of long Covid. Funding Exeter University Alumni, Attomarker Ltd-funded PhD studentship (PJP) at the University of Exeter and Attomarker Ltd funding directly.

Prevalence of SARS-CoV-2 amongst school children in the omicron wave was high leading to a constant exposure of teachers to the virus. A cohort of staff members ( n = 28) was recruited from a UK primary school setting. The prevalent variants at the time were Omicron BA.1, BA.4/5 and BA.2: 61% of the cohort reported a lateral-flow-confirmed positive test for SARS-CoV-2 infection in late 2021 or 2022. A mass-standardised quantitative antibody spectrum was measured for both antibody concentration and a new measure of antibody quality; the proportion of antibodies still bound to the epitope at pH 3.2 compared with pH 7.4. The antibody spectrum was measured or IgG to the spike protein for variants Wuhan, Alpha, Beta, Gamma, Delta and Omicron BA.1, BA.2.75, BA.2.12.1, BA.4 and BA.5. The new antibody quality measure shows a mean of 49% with (IQR 32% – 68%). The cohort showed a Universal positive immunity endotype, U(+), of antibodies binding to the spike protein across the variant spectrum with an incidence of 78% (95% CI 60% – 88%) with good antibody concentrations to all ten variants; the incidence drops to 25% (95% CI 13% – 43%) when the affinity spectrum is measured.