Biology subjects

Castilletti, C.

Publications and source records attributed to Castilletti, C..

5 recordsLinked to original sources

bioRxiv2025

Oral 4-fluorouridine completely suppresses epidemic Oropouche virus replication in mice and confers protection against virus-induced disease.

Oropouche virus (OROV) is an orthobunyavirus that causes increasingly frequent and severe outbreaks in Central and South America. We report that 4'-fluorouridine (4'-FlU) inhibits the in vitro replication of epidemic and pre-epidemic OROV strains in multiple cell lines. In vitro polymerase assays demonstrate that 4'-FlU (as its triphosphate) targets the Peribunyaviridae L protein, is incorporated during RNA synthesis and causes premature chain termination. Following 69 consecutive days of in vitro passages of OROV in the presence of suboptimal concentrations of 4'-FlU, no drug-resistant variants were identified in the viral polymerase. In stringent mouse (AG129) or Syrian hamster OROV-infection models, oral administration of 4'-FlU completely blocked viral replication and virus-induced disease, even when administration was delayed until 72 hours after infection. Our findings support exploring the potential of 4'-FlU for the management of OROV infections in humans.

microbiology↗

bioRxiv2025

Antigen-agnostic identification of poxvirus broadly neutralizing antibodies targeting OPG153

Recurrent mpox outbreaks caused by the monkeypox virus (MPXV) have prompted the World Health Organization to declare a Public Health Emergency of International Concern and have stimulated the development of medical interventions. Here, antigen-agnostic isolation of neutralizing monoclonal antibodies from convalescent or vaccinated people, AlphaFold 3-based predictive modeling, and cryo-electron microscopy were synergistically combined to identify the protein encoded by orthopoxviral gene (OPG) 153 (MPXV A28) as a target of broadly neutralizing antibodies. OPG153-targeting antibodies neutralized MPXV clade Ib, IIb, and vaccinia virus (VACV), and cross-reacted with OPG153 orthologs from cowpox and variola viruses. Immunization with MPXV OPG153 elicited a potent neutralizing antibody response against MPXV and VACV, substantiating OPG153 as a promising vaccine antigen and a potent target for preventive and therapeutic antibodies.

microbiology↗

bioRxiv2020

Immunogenicity of a new gorilla adenovirus vaccine candidate for COVID-19

The COVID-19 pandemic caused by the emergent SARS-CoV-2 coronavirus threatens global public health and there is an urgent need to develop safe and effective vaccines. Here we report the generation and the preclinical evaluation of a novel replication-defective gorilla adenovirus-vectored vaccine encoding the pre-fusion stabilized Spike (S) protein of SARS-CoV2. We show that our vaccine candidate, GRAd- COV2, is highly immunogenic both in mice and macaques, eliciting both functional antibodies which neutralize SARS-CoV-2 infection and block Spike protein binding to the ACE2 receptor, and a robust, Th1- dominated cellular response in the periphery and in the lung. We show here that the pre-fusion stabilized Spike antigen is superior to the wild type in inducing ACE2-interfering, SARS-CoV2 neutralizing antibodies. To face the unprecedented need for vaccine manufacturing at massive scale, different GRAd genome deletions were compared to select the vector backbone showing the highest productivity in stirred tank bioreactors. This preliminary dataset identified GRAd-COV2 as a potential COVID-19 vaccine candidate, supporting the translation of GRAd-COV2 vaccine in a currently ongoing Phase I clinical trial (NCT04528641).

immunology↗

bioRxiv2020

Extremely potent human monoclonal antibodies from convalescent Covid-19 patients

Human monoclonal antibodies are safe, preventive and therapeutic tools, that can be rapidly developed to help restore the massive health and economic disruption caused by the Covid-19 pandemic. By single cell sorting 4277 SARS-CoV-2 spike protein specific memory B cells from 14 Covid-19 survivors, 453 neutralizing antibodies were identified and 220 of them were expressed as IgG. Up to 65,9% of monoclonals neutralized the wild type virus at a concentration of >500 ng/mL, 23,6% neutralized the virus in the range of 100 - 500 ng/mL and 9,1% had a neutralization potency in the range of 10 - 100 ng/mL. Only 1,4% neutralized the authentic virus with a potency of 1-10 ng/mL. We found that the most potent neutralizing antibodies are extremely rare and recognize the RBD, followed in potency by antibodies that recognize the S1 domain, the S-protein trimeric structure and the S2 subunit. The three most potent monoclonal antibodies identified were able to neutralize the wild type and D614G mutant viruses with less than 10 ng/mL and are good candidates for the development of prophylactic and therapeutic tools against SARS-CoV-2. One Sentence SummaryExtremely potent neutralizing human monoclonal antibodies isolated from Covid-19 convalescent patients for prophylactic and therapeutic interventions.

immunology↗

bioRxiv2020

Identification of neutralizing human monoclonal antibodies from Italian Covid-19 convalescent patients

In the absence of approved drugs or vaccines, there is a pressing need to develop tools for therapy and prevention of Covid-19. Human monoclonal antibodies have very good probability of being safe and effective tools for therapy and prevention of SARS-CoV-2 infection and disease. Here we describe the screening of PBMCs from seven people who survived Covid-19 infection to isolate human monoclonal antibodies against SARS-CoV-2. Over 1,100 memory B cells were single-cell sorted using the stabilized prefusion form of the spike protein and incubated for two weeks to allow natural production of antibodies. Supernatants from each cell were tested by ELISA for spike protein binding, and positive antibodies were further tested for neutralization of spike binding to receptor(s) on Vero E6 cells and for virus neutralization in vitro. From the 1,167 memory B specific for SARS-CoV-2, we recovered 318 B lymphocytes expressing human monoclonals recognizing the spike protein and 74 of these were able to inhibit the binding of the spike protein to the receptor. Finally, 17 mAbs were able to neutralize the virus when assessed for neutralization in vitro. Lead candidates to progress into the drug development pipeline will be selected from the panel of neutralizing antibodies identified with the procedure described in this study. One Sentence SummaryNeutralizing human monoclonal antibodies isolated from Covid-19 convalescent patients for therapeutic and prophylactic interventions.

immunology↗