Biology subjects

Santoro, M. G.

Publications and source records attributed to Santoro, M. G..

5 recordsLinked to original sources

bioRxiv2022

Human coronaviruses activate and hijack the proteostasis guardian HSF1 to enhance viral replication

Organisms respond to proteotoxic stress by activating a cellular defense mechanism, known as the heat shock response (HSR), that triggers the expression of cytoprotective heat shock proteins (HSP) to counteract the damaging effects of proteostasis disruption. The HSR is regulated by a family of transcription factors (heat shock factors, HSFs); among six human HSFs, HSF1 acts as a proteostasis guardian regulating acute and severe stress-driven transcriptional responses. Seasonal coronaviruses HCoV-229E, HCoV-NL63, HCoV-OC43 and HCoV-HKU1 (sHCoV) are globally circulating in the human population. Although sHCoV generally cause only mild upper respiratory diseases in immunocompetent hosts, severe complications may occur in specific populations. There is no effective treatment for sHCoV infections, also due to the limited knowledge on sHCoV biology. We now show that both Alpha- and Beta-sHCoV are potent inducers of HSF1, selectively promoting HSF1 phosphorylation at serine-326 residue and nuclear translocation, and triggering a powerful HSF1-driven transcriptional response in infected cells at late stages of infection. Despite the coronavirus-mediated shut-down of the host cell translational machinery, high levels of selected canonical and non-canonical HSF1-target genes products, including HSP70, HSPA6 and the zinc-finger AN1-type domain-2a gene/AIRAP, were found in HCoV-infected cells. Interestingly, silencing experiments demonstrate that HSR activation does not merely reflect a cellular defense response to viral infection, but that sHCoV activate and hijack the HSF1-pathway for their own gain. Notably, nuclear HSF1 pools depletion via Direct-Targeted HSF1 inhibitor (DTHIB) treatment was highly effective in hindering sHCoV replication in lung cells. Altogether the results open new scenarios for the search of innovative antiviral strategies in the treatment of coronavirus infections.

microbiology↗

bioRxiv2022

Nitazoxanide is a potent inhibitor of human seasonal coronaviruses acting at postentry level: effect on viral spike glycoprotein

Coronaviridae is recognized as one of the most rapidly evolving virus family as a consequence of the high genomic nucleotide substitution rates and recombination. The family comprises a large number of enveloped, positive-sense single-stranded RNA viruses, causing an array of diseases of varying severity in animals and humans. To date, seven human coronaviruses (HCoV) have been identified, namely HCoV-229E, HCoV-NL63, HCoV-OC43 and HCoV-HKU1, which are globally circulating in the human population (seasonal HCoV, sHCoV), and the highly pathogenic SARS-CoV, MERS-CoV and SARS-CoV-2. Seasonal HCoV are estimated to contribute to 15-30% of common cold cases in humans; although diseases are generally self-limiting, sHCoV can sometimes cause severe lower respiratory infections, as well as enteric and neurological diseases. No specific treatment is presently available for sHCoV infections. Herein we show that the anti-infective drug nitazoxanide has a potent antiviral activity against three human endemic coronaviruses, the Alpha-coronaviruses HCoV-229E and HCoV-NL63, and the Beta-coronavirus HCoV-OC43 in cell culture with IC50 ranging between 0.05 and 0.15 g/ml and high selectivity indexes. We found that nitazoxanide does not affect HCoV adsorption, entry or uncoating, but acts at postentry level and interferes with the spike glycoprotein maturation, hampering its terminal glycosylation at an endoglycosidase H-sensitive stage. Altogether the results indicate that nitazoxanide, due to its broad-spectrum anti-coronavirus activity, may represent a readily available useful tool in the treatment of seasonal coronavirus infections.

microbiology↗

bioRxiv2022

Spike mutation resilient scFv76 antibody counteracts SARS-CoV-2 lung damage upon aerosol delivery

Uneven worldwide vaccination coverage against SARS-CoV-2 and emergence of variants escaping immunity call for broadly-effective and easily-deployable therapeutics. We previously described the human single-chain scFv76 antibody, which recognizes SARS-CoV-2 Alfa, Beta, Gamma and Delta variants. We now show that scFv76 also neutralizes infectivity and fusogenic activity of Omicron BA.1 and BA.2 variants. Cryo-EM analysis reveals that scFv76 binds to a well-conserved SARS-CoV-2 spike epitope, providing the structural basis for its broad-spectrum activity. Moreover, we demonstrate that nebulized scFv76 exhibits therapeutic efficacy in a severe hACE2 transgenic mouse model of COVID-19 pneumonia, as shown by body weight and pulmonary viral load data. Counteraction of infection correlates with the inhibition of lung inflammation observed by histopathology and expression of inflammatory cytokines and chemokines. Biomarkers of pulmonary endothelial damage were also significantly reduced in scFv76-treated mice. Altogether the results support the use of nebulized scFv76 for COVID-19 induced by any SARS-CoV-2 variants emerged so far.

microbiology↗

bioRxiv2021

Human single-chain antibodies neutralize SARS-CoV-2 variants by engaging an essential epitope of the spike: a new weapon against COVID-19

As of October 2021, coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a global emergency, and novel therapeutics are urgently needed. Here we describe human single chain variable fragment (scFv) antibodies (76clAbs) that block an epitope of the SARS-CoV-2 spike protein essential for ACE2-mediated entry into cells. 76clAbs neutralize the delta variant and other variants being monitored (VBMs) and inhibit spike-mediated pulmonary cell-cell fusion, a critical feature of COVID-19 pathology. In two independent animal models, intranasal administration counteracted the infection. Due to high efficiency, remarkable stability, resilience to nebulization and low production cost, 76clAbs may become a relevant tool for rapid, self-administrable early intervention in SARS-CoV-2-infected subjects independently of their immune status.

bioengineering↗

bioRxiv2021

Impairment of SARS-CoV-2 spike glycoprotein maturation and fusion activity by the broad-spectrum anti-infective drug nitazoxanide

SARS-CoV-2, the causative agent of COVID-19, has caused an unprecedented global health crisis. The SARS-CoV-2 spike, a surface-anchored trimeric class-I fusion-glycoprotein essential for viral entry, represents a key target for developing vaccines and therapeutics capable of blocking virus invasion. The emergence of SARS-CoV-2 spike-variants that facilitate virus spread and may affect vaccine efficacy highlights the need to identify novel antiviral strategies for COVID-19 therapy. Here we demonstrate that nitazoxanide, an antiprotozoal agent with recognized broad-spectrum antiviral activity, interferes with SARS-CoV-2 spike biogenesis, hampering its maturation at an endoglycosidase H-sensitive stage. Engineering multiple SARS-CoV-2 variant-pseudoviruses and utilizing quantitative cell-cell fusion assays, we show that nitazoxanide-induced spike modifications hinder progeny virion infectivity as well as spike-driven pulmonary cell-cell fusion, a critical feature of COVID-19 pathology. Nitazoxanide, being equally effective against the ancestral SARS-CoV-2 Wuhan-spike and different emerging variants, including the Delta variant of concern, may represent a useful tool in the fight against COVID-19 infections.

microbiology↗