ABSTRACT
It has been proven that mRNA vaccines are highly effective against the COVID-19 outbreak, and low prevalence of side effects has been shown. However, there are still many gaps in our understanding of the biology and biosafety of nucleic acids as components of lipid nanoparticles (LNPs) most often used as a system for inctracellular delivery of mRNA-based vaccines. It is known that LNPs cause severe injection site inflammation, have broad biodistribution profiles, and are found in multiple tissues of the body, including the brain, after administration. The role of new medications with such pharmacokinetics in inflammation developing in inaccessible organs is poorly understood. The study was aimed to assess the effects of various doses of mRNA-LNP expressing the reporter protein (0, 5, 10, and 20 microg of mRNA encoding the firefly luciferase) on the expression of neuroinflammation markers (Tnfalpha, Il1beta, Gfap, Aif1) in the prefrontal cortex and hypothalamus of laboratory animals 4, 8, and 30 h after the intramuscular injection of LNP nanoemulsion. It was shown that mRNA-LNP vaccines in a dose of 10-20 microg of mRNA could enhance Aif1 expression in the hypothalamus 8 h after vaccination, however, no such differences were observed after 30 h. It was found that the Gfap, l11beta, Tnfalpha expression levels in the hypothalamus observed at different times in the experimental groups were different. According to the results, mRNA-LNPs administered by the parenteral route can stimulate temporary activation of microglia in certain time intervals in the dose-dependent and site specific manner.Copyright © 2022 Pirogov Russian National Research Medical University. All rights reserved.
ABSTRACT
Purpose : With this research project we wanted to approach the question of whether SARS-CoV 2 can infect the eye. In order to infect ocular tissues, virus-specific receptors;coreceptors or proteases must be present in the eye tissue. SARS-CoV 2 uses the human angiotensin converting enzyme 2 (ACE2) receptor to enter cells. In addition, the mammalian serine protease TMPRSS2, the protease furin and the glycoprotein neuropilin are identified as relevant proteases for the interaction of the virus with ACE2. Last year, we were able to show that ACE2 is significantly more expressed in ocular tissue of covid patients. Here the expression level of the co-receptor and glia markers, as well as the present of virus was confirmed in this study. Methods : Seven eyes from donors without covid disease (COVID-) as well as ten fixed eyes from COVID-19 patients (COVID+) were analysed for their expression profile of ACE2, TMPRSS2, neuropilin and furin in the retina and cornea. The ocular tissues were examined for protein expression by immunohistochemical staining or for RNA expression by quantitative real-time PCR. In addition, viral spike protein was detected histologically in eyes, and expression profiles of GFAP and Iba-1 were assessed. Results : Similar to ACE2 and TMPRSS2, the two proteases neuropilin and furin were detected in the retina and cornea. Interestingly, the expression profile differed in terms of strength and localization, especially in the retina. The presence of the virus in both cornea and retina was also demonstrated by the detection of viral spike protein. In all COVID+ retinas, strong GFAP staining was observed as well as some Iba-1 positive cells, suggesting activation of macro- and microglia. Conclusions : Expression of ACE2, TMPRSS2, furin and neuropilin was demonstrated in COVID+ ocular tissues. In addition to the virus detection in retina and cornea, a glial reaction could also be observed. One can therefore assume an infection of the eye in these cases. However, in summary it can be said that an infection of the eye tissue is possible since all demanded receptors are present.
ABSTRACT
Aims: Activation of microglial cells represents the most common neu-ropathological change in fatal cases of COVID-19 with particular prominence in the brainstem. However, detailed assessments are lacking. Here, we assessed reactive microglia in COVID-19 tissue and tested for disease-specific activation patterns. Methods: We used an early-(Iba1) and a late-stage (CD68) immuno-histochemistry marker for microglial activation in human post-mortem brainstem and frontal lobe tissues in eight fatal COVID-19 cases, seven septic controls and six non-septic controls. We quantified the level of microglial activation employing a Qu-Path-based automated approach. Using a mixed three-way ANOVA, we tested for effects and interactions of brain region, microglial marker and group. Results: Reactive microglia were detected in all cases across brain regions and antibodies. However, COVID-19 brains exhibited significantly higher levels of microglial activation than septic and control brains, especially of late-stage microglia (CD68+). Irrespective of disease, microglia activation was significantly more pronounced and further progressed (CD68+) in brainstem tissues, particularly the medulla, than in the frontal lobe. Whilst survival time from admission marginally significantly correlated with the level of reactive microglia in COVID-19, no associations were found between neuroinflammation and either gender or age at death. Conclusions: Whilst the brainstem demonstrates a disease-independent high susceptibility to inflammation, microglial activation in COVID-19 (COVID-19 microglia encephalopathy) is specific and of importance for understanding the involvement of the CNS in this disease.