Progressive brain structural abnormality in depression assessed with MR imaging by using causal network analysis

Background As a neuroprogressive illness, depression is accompanied by brain structural abnormality that extends to many brain regions. However, the progressive structural alteration pattern remains unknown. Methods To elaborate the progressive structural alteration of depression according to illness duration, we recruited 195 never-treated first-episode patients with depression and 130 healthy controls (HCs) undergoing T1-weighted MRI scans. Voxel-based morphometry method was adopted to measure gray matter volume (GMV) for each participant. Patients were first divided into three stages according to the length of illness duration, then we explored stage-specific GMV alterations and the causal effect relationship between them using causal structural covariance network (CaSCN) analysis. Results Overall, patients with depression presented stage-specific GMV alterations compared with HCs. Regions including the hippocampus, the thalamus and the ventral medial prefrontal cortex (vmPFC) presented GMV alteration at onset of illness. Then as the illness advanced, others regions began to present GMV alterations. These results suggested that GMV alteration originated from the hippocampus, the thalamus and vmPFC then expanded to other brain regions. The results of CaSCN analysis revealed that the hippocampus and the vmPFC corporately exerted causal effect on regions such as nucleus accumbens, the precuneus and the cerebellum. In addition, GMV alteration in the hippocampus was also potentially causally related to that in the dorsolateral frontal gyrus. Conclusions Consistent with the neuroprogressive hypothesis, our results reveal progressive morphological alteration originating from the vmPFC and the hippocampus and further elucidate possible details about disease progression of depression.

Impact of B.1.617 and RBD SARS-CoV-2 Variants on Vaccine Efficacy: An In-silico Approach

The existing panels of COVID-19 vaccines are based on the spike protein of earlier SARS-CoV-2 strain that emerged in Wuhan, China. However, the evolving nature of SARS-CoV-2 has resulted in emergence of new variants, thereby, posing a greater challenge in the management of the disease. India faced a deadlier second wave of infections very recently and genomic surveillance revealed that B.1.617 variant and its sub lineages are responsible for majority of the cases. These are highly infectious and possibly more lethal and therefore labelled as variants of concern by WHO. Hence, it’s crucial to determine if the current vaccines available can be effective against these variants. To address this, we performed molecular dynamics (MD) simulation on B.1.617 along with K417G variants and other RBD variants. We studied structural alteration of the spike protein and factors affecting antibody neutralization and immune escape. We found in seven of the 12 variants studied, there was a structural alteration in RBD region further affecting its stability and function. Docking analysis of RBD variants and wild type strain demonstrated increase in binding affinity with ACE2 (angiotensin 2 altered enzymes) receptor in these variants. Molecular interaction with CR3022 antibody revealed that binding affinity was less in comparison to wild type, with B.1.617 showing the least binding affinity. These findings from the extensive simulations provides novel mechanistic insights on the conformational dynamics and improves our understanding of the enhanced properties of these variants in terms of infectivity, transmissibility, neutralization potential, virulence and host-viral replication fitness.