Biology subjects

Pandit, N. P.

Publications and source records attributed to Pandit, N. P..

3 recordsLinked to original sources

bioRxiv2023

Multiple steps of prion strain adaptation to a new host

The transmission of prions across species is a critical aspect of their dissemination among mammalian hosts, including humans. This process often necessitates strain adaptation. In this study, we sought to investigate the mechanisms underlying prion adaptation while mitigating biases associated with the history of cross-species transmission of natural prion strains. To achieve this, we utilized the synthetic hamster prion strain S05. Propagation of S05 using mouse PrPC in Protein Misfolding Cyclic Amplification did not immediately overcome the species barrier. This finding underscores the involvement of factors beyond disparities in primary protein structures. Subsequently, we performed five serial passages to stabilize the incubation time to disease in mice. The levels of PrPSc increased with each passage, reaching a maximum at the third passage, and declining thereafter. This suggests that only the initial stage of adaptation is primarily driven by an acceleration in PrPSc replication. During the protracted adaptation to a new host, we observed significant alterations in the glycoform ratio and sialylation status of PrPSc N-glycans. These changes support the notion that qualitative modifications in PrPSc contribute to a more rapid disease progression. Furthermore, consistent with the decline in sialylation, a cue for "eat me" signaling, the newly adapted strain exhibited preferential colocalization with microglia. In contrast to PrPSc dynamics, the intensity of microglia activation continued to increase after the third passage in the new host. In summary, our study elucidates that the adaptation of a prion strain to a new host is a multi-step process driven by several factors.

neuroscience↗

bioRxiv2023

Reactive astrocytes associated with prion disease impair the blood brain barrier

BackgroundImpairment of the blood-brain barrier (BBB) is considered to be a common feature among neurodegenerative diseases, including Alzheimers, Parkinsons and prion diseases. In prion disease, increased BBB permeability was reported 40 years ago, yet the mechanisms behind the loss of BBB integrity have never been explored. Recently, we showed that reactive astrocytes associated with prion diseases are neurotoxic. The current work examines the potential link between astrocyte reactivity and BBB breakdown. ResultsIn prion-infected mice, the loss of BBB integrity and aberrant localization of aquaporin 4 (AQP4), a sign of retraction of astrocytic endfeet from blood vessels, were noticeable prior to disease onset. Gaps in cell-to-cell junctions along blood vessels, together with downregulation of Occludin, Claudin-5 and VE-cadherin, which constitute tight and adherens junctions, suggested that loss of BBB integrity is linked with degeneration of vascular endothelial cells. In contrast to cells isolated from non-infected adult mice, endothelial cells originating from prion-infected mice displayed disease-associated changes, including lower levels of Occludin, Claudin-5 and VE-cadherin expression, impaired tight and adherens junctions, and reduced trans-endothelial electrical resistance (TEER). Endothelial cells isolated from non-infected mice, when co-cultured with reactive astrocytes isolated from prion-infected animals or treated with media conditioned by the reactive astrocytes, developed the disease-associated phenotype observed in the endothelial cells from prion-infected mice. Reactive astrocytes were found to produce high levels of secreted IL-6, and treatment of endothelial monolayers originating from non-infected animals with recombinant IL-6 alone reduced their TEER. Remarkably, treatment with extracellular vesicles produced by normal astrocytes partially reversed the disease phenotype of endothelial cells isolated from prion-infected animals. ConclusionsTo our knowledge, the current work is the first to illustrate early BBB breakdown in prion disease and to document that reactive astrocytes associated with prion disease are detrimental to BBB integrity. Moreover, our findings suggest that the harmful effects are linked to proinflammatory factors secreted by reactive astrocytes.

neuroscience↗

bioRxiv2021

Alzheimer's disease-associated β-Amyloid does not protect against Herpes Simplex Virus 1 brain infection

Alzheimers disease (AD) is devastating fatal neurodegenerative disease. An alternative to the amyloid cascade hypothesis is the hypothesis that a viral infection is key to the etiology of late-onset AD, with amyloid A{beta} peptides playing a protective role. Contrary to previous work, in the current study the 5XFAD genotype failed to protect mice against infection with two strains of herpes simplex virus 1 (HSV-1), 17syn+ and McKrae. Moreover, the region- or cell-specific tropisms of HSV-1 were not affected by the 5XFAD genotype, arguing that host-pathogen interactions were not altered. In aged 5XFAD mice with abundant A{beta} plaques, only small, statistically non-significant protection against acute HSV-1 infection was observed, yet no colocalization between HSV-1 and A{beta} plaques was found. While the current study questions the antiviral role of APP or A{beta}, it neither supports nor refutes the viral etiology hypothesis of late-onset AD.

neuroscience↗