Biology subjects

Dalebout, T. J.

Publications and source records attributed to Dalebout, T. J..

4 recordsLinked to original sources

bioRxiv2021

Ad26.COV2.S-elicited immunity protects against G614 spike variant SARS-CoV-2 infection in Syrian hamsters and does not enhance respiratory disease in challenged animals with breakthrough infection after sub-optimal vaccine dosing

Previously we have shown that a single dose of recombinant adenovirus serotype 26 (Ad26) vaccine expressing a prefusion stabilized SARS-CoV-2 spike antigen (Ad26.COV2.S) is immunogenic and provides protection in Syrian hamster and non-human primate SARS-CoV-2 infection models. Here, we investigated the immunogenicity, protective efficacy and potential for vaccine-associated enhanced respiratory disease (VAERD) mediated by Ad26.COV2.S in a moderate disease Syrian hamster challenge model, using the currently most prevalent G614 spike SARS-CoV-2 variant. Vaccine doses of 1x109 vp and 1x1010 vp elicited substantial neutralizing antibodies titers and completely protected over 80% of SARS-CoV-2 inoculated Syrian hamsters from lung infection and pneumonia but not upper respiratory tract infection. A second vaccine dose further increased neutralizing antibody titers which was associated with decreased infectious viral load in the upper respiratory tract after SARS-CoV-2 challenge. Suboptimal non-protective immune responses elicited by low-dose A26.COV2.S vaccination did not exacerbate respiratory disease in SARS-CoV-2-inoculated Syrian hamsters with breakthrough infection. In addition, dosing down the vaccine allowed to establish that binding and neutralizing antibody titers correlate with lower respiratory tract protection probability. Overall, these pre-clinical data confirm efficacy of a 1-dose vaccine regimen with Ad26.COV2.S in this G614 spike SARS-CoV-2 virus variant Syrian hamster model, show the added benefit of a second vaccine dose, and demonstrate that there are no signs of VAERD under conditions of suboptimal immunity.

immunology↗

bioRxiv2020

Immunogenicity of one- and two-dose regimens of the Ad26.COV2.S COVID-19 vaccine candidate in adult and aged rhesus macaques

Safe and effective coronavirus disease (COVID)-19 vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one- and two-dose regimens of the Ad26.COV2.S vaccine candidate in adult and aged non-human primates (NHP). A two-dose Ad26.COV2.S regimen induced higher peak binding and neutralizing antibody responses compared to a single dose. In one-dose regimens neutralizing antibody responses were stable for at least 14 weeks, providing an early indication of durability. Ad26.COV2.S induced humoral immunity and Th1 skewed cellular responses in aged NHP that were comparable to adult animals. Importantly, aged Ad26.COV2.S-vaccinated animals challenged 3 months post -dose 1 with a SARS-CoV-2 spike G614 variant showed near complete lower and substantial upper respiratory tract protection for both regimens. These are the first NHP data showing COVID-19 vaccine protection against the SARS-CoV-2 spike G614 variant and support ongoing clinical Ad26.COV2.S development. SummaryCOVID-19 vaccines are urgently needed and while single-dose vaccines are preferred, two-dose regimens may improve efficacy. We show improved Ad26.COV2.S immunogenicity in non-human primates after a second vaccine dose, while both regimens protected aged animals against SARS-CoV-2 disease.

immunology↗

bioRxiv2020

Ad26-vector based COVID-19 vaccine encoding a prefusion stabilized SARS-CoV-2 Spike immunogen induces potent humoral and cellular immune responses

Development of effective preventative interventions against SARS-CoV-2, the etiologic agent of COVID-19 is urgently needed. The viral surface spike (S) protein of SARS-CoV-2 is a key target for prophylactic measures as it is critical for the viral replication cycle and the primary target of neutralizing antibodies. We evaluated design elements previously shown for other coronavirus S protein-based vaccines to be successful, e.g. prefusion-stabilizing substitutions and heterologous signal peptides, for selection of a S-based SARS-CoV-2 vaccine candidate. In vitro characterization demonstrated that the introduction of stabilizing substitutions (i.e., furin cleavage site mutations and two consecutive prolines in the hinge region of S1) increased the ratio of neutralizing versus non-neutralizing antibody binding, suggestive for a prefusion conformation of the S protein. Furthermore, the wild type signal peptide was best suited for the correct cleavage needed for a natively-folded protein. These observations translated into superior immunogenicity in mice where the Ad26 vector encoding for a membrane-bound stabilized S protein with a wild type signal peptide elicited potent neutralizing humoral immunity and cellular immunity that was polarized towards Th1 IFN-{gamma}. This optimized Ad26 vector-based vaccine for SARS-CoV-2, termed Ad26.COV2.S, is currently being evaluated in a phase I clinical trial (ClinicalTrials.gov Identifier: NCT04436276).

immunology↗

bioRxiv2019

The deubiquitinating activity of Middle East respiratory syndrome coronavirus papain-like protease delays the innate immune response and enhances virulence in a mouse model

AbstractMiddle East respiratory syndrome coronavirus (MERS-CoV) continues to cause zoonotic infections and serious disease, primarily in the Arabian Peninsula, due to repeated spill-over from dromedary camels and subsequent nosocomial transmission. Approved MERS vaccines for use in animals or humans are not currently available. MERS-CoV replication requires the virus-encoded papain-like protease (PLpro) to cleave multiple sites in the viral replicase polyproteins, thereby releasing functional non-structural proteins. Additionally, PLpro is a deubiquitinating enzyme (DUB) that can remove ubiquitin(-like) moieties from substrates, presumably to counteract host antiviral responses. In previous work, we determined the crystal structure of MERS-CoV PLpro in complex with ubiquitin, facilitating the design of PLpro mutations that impair DUB activity without affecting viral polyprotein cleavage. Here, we introduced these DUB-inactivating mutations into the viral genome and examined their impact on MERS-CoV infection both in cell culture and in a lethal mouse model. Although overall replication of DUB-negative and wild-type (wt) recombinant MERS-CoV was comparable in multiple cell lines, infection with DUB-negative virus markedly increased mRNA levels for interferon (IFN)-{beta} and IFN-stimulated genes. Moreover, compared to a wt virus infection, the survival rate was significantly increased when DUB-negative MERS-CoV was used to infect transgenic mice expressing a human MERS-CoV receptor. Interestingly, DUB-negative and wt MERS-CoV replicated to the same titers in lungs of infected mice, but the DUB-negative virus was cleared faster, likely due to the observed accelerated and better-regulated innate immune responses, in contrast to delayed and subsequently excessive responses in wt virus-infected mice. This study provides the first direct evidence that the DUB activity of a coronaviral protease contributes to innate immune evasion and can profoundly enhance virulence in an animal model. Thus, reduction or removal of the innate immune-suppressive DUB activity of PLpros is a promising strategy for coronavirus attenuation in the context of rational vaccine development.\n\nAuthor SummaryAlthough zoonotic coronaviruses such as Middle East respiratory coronavirus (MERS-CoV) have pandemic potential, therapeutics and vaccines that counteract this public health threat are not currently available. Coronaviruses typically employ multiple strategies to evade the hosts innate immune response, which may enhance clinical disease and/or reduce the efficacy of modified live vaccines. The MERS-CoV-encoded papain-like protease (PLpro) is not only crucial for the expression of functional replicase proteins, but has also been postulated to antagonize ubiquitination-dependent steps during the activation of the innate immune response. Here, we report the generation of engineered MERS-CoVs mutants in which PLpros deubiquitinating (DUB) activity was specifically disrupted without affecting virus viability. In this manner, we could demonstrate that the DUB activity of PLpro suppresses the interferon response in MERS-CoV-infected cells. Strikingly, in the lungs of mice infected with DUB-negative MERS-CoV, innate immune responses were induced at an earlier stage of infection than in wt virus-infected mice. This group also showed a clearly increased survival, indicating that the DUB activity is an important MERS-CoV virulence factor. This proof-of-concept study establishes that the engineering of DUB-negative coronaviruses, which elicit a more effective immune response in the host, is a viable strategy for vaccine development.

microbiology↗