Biology subjects

Richner, J. M.

Publications and source records attributed to Richner, J. M..

4 recordsLinked to original sources

bioRxiv2022

Nucleocapsid-specific humoral responses improve the control of SARS-CoV-2

The spike protein of SARS-CoV-2 is a critical antigen present in all approved SARS-CoV-2 vaccines. This surface viral protein is also the target for all monoclonal antibody therapies, but it is unclear whether antibodies targeting other viral proteins can also improve protection against COVID-19. Here, we interrogate whether nucleocapsid-specific antibodies can improve protection against SARS-CoV-2. We first immunized mice with a nucleocapsid-based vaccine, and then transferred sera from these mice into naive mice. On the next day, the recipient mice were challenged intranasally with SARS-CoV-2 to evaluate whether nucleocapsid-specific humoral responses affect viral control. Interestingly, mice that received nucleocapsid-specific sera exhibited enhanced control of a SARS-CoV-2 infection. These findings provide the first demonstration that humoral responses specific to an internal coronavirus protein can help clear infection, warranting the inclusion of other viral antigens in next-generation SARS-CoV-2 vaccines and providing a rationale for the clinical evaluation of nucleocapsid-specific monoclonals to treat COVID-19. HighlightsA SARS-CoV-2 nucleocapsid vaccine elicits robust nucleocapsid-specific antibody responses. This nucleocapsid vaccine generates memory B cells (MBC). Nucleocapsid-specific humoral responses do not prevent SARS-CoV-2 infection. Nucleocapsid-specific humoral responses help control a SARS-CoV-2 infection.

immunology↗

bioRxiv2022

Dual Inhibition of Cathepsin L and 3CL-Pro by GC-376 Constrains SARS Cov2 Infection Including Omicron Variant

Recurrent waves of SARS CoV2 infections remain a major global health concern. Emergence of highly infectious variants with reduced sensitivity to neutralization by vaccines and monoclonal antibodies (mAb) necessitates a deeper understanding of factors involved in SARS CoV2 infections and identification of drug candidates to halt infection. Here, we determined the primacy of endosomal protease cathepsin-L in mediating SARS CoV2 entry and screened a library of well-annotated bioactive compounds for potent cathepsin-L inhibitory activity. Whilst the potent cathepsin-L inhibitors were capable of inhibiting SARS CoV2 entry and cytopathic effect (CPE) in less susceptible cell lines such as human ACE2 expressing 293T cells, these drugs failed to inhibit SARS CoV2 in highly susceptible cell lines such as human TMPRSS2 or human-ACE2-TMPRSS2 overexpressing Vero E6 cells. Only drugs with dual inhibitory effect on both host cathepsin-L and virus 3CL-Protease enzymes such as Z-FA-FMK and GC-376 were capable of inhibiting prototypic (USA-WA1/2020, Lineage A) SARS CoV2 induced CPE in highly susceptible cell lines. Moreover, these drugs inhibited delta (Lineage-B.1.617.2) and omicron (Lineage-B.1.1.529) infection with equal potency showing that the newer mutations harbored in these variants did not affect the mechanism of action of these drugs such as cathepsin-L or 3CL-Pro inhibition. Moreover, our early evidence that 3CL-Pro inhibition can effectively inhibit omicron-induced CPE in highly susceptible cell lines suggests that the recently FDA-approved oral drug, a 3CL-Pro inhibitor which is a combination of nirmatrelvir/ritonavir (Paxlovid) could be effective against omicron variant which shows reduced sensitivity to vaccines and mAb. ImportanceWe report that cathepsin-L and 3CL-Pro as major targets for designing antivirals against SARS CoV2. Dual inhibition of cathepsin-L and 3CL-Pro by GC-376 renders it effective in inhibiting SARS CoV2-induced cytopathic effect in highly susceptible cell lines. Moreover, this candidate drug is equally effective against prototypic SARS CoV2 lineage A and emerging variants such as delta and omicron which show reduced sensitivity to vaccines and monoclonal antibodies. Given the recent wave of SARS CoV2 omicron variant infection around the world, and 3CL-Pro inhibitor nirmatrelvir is one of the components of the FDA-approved Paxlovid, our findings are timely, important and should be of broad interest.

microbiology↗

bioRxiv2021

A mRNA-LNP vaccine against Dengue Virus elicits robust, serotype-specific immunity

Dengue virus (DENV) is the most common vector-borne viral disease with nearly 400 million worldwide infections each year concentrated in the tropical and subtropical regions of the world. Severe dengue complications are often associated with a secondary heterotypic infection of one of the four circulating serotypes. In this scenario, humoral immune responses targeting cross-reactive, poorly-neutralizing epitopes can lead to increased infectivity of susceptible cells via antibody-dependent enhancement (ADE). In this way, antibodies produced in response to infection or vaccination are capable of contributing to enhanced disease in subsequent infections. Currently, there are no available therapeutics to combat DENV disease, and there is an urgent need for a safe and efficacious vaccine. Here, we developed a nucleotide-modified mRNA vaccine encoding for the membrane and envelope structural proteins from DENV serotype 1 encapsulated into lipid nanoparticles (prM/E mRNA-LNP). Vaccination of mice elicited robust antiviral immune responses comparable to viral infection with high levels of neutralizing antibody titers and antiviral CD4+ and CD8+ T cells. Immunocompromised AG129 mice vaccinated with the prM/E mRNA-LNP vaccine were protected from a lethal DENV challenge. Vaccination with either a wild-type vaccine, or a vaccine with mutations in the immunodominant fusion-loop epitope, elicited equivalent humoral and cell mediated immune responses. Neutralizing antibodies elicited by the vaccine were sufficient to protect against a lethal challenge. Both vaccine constructs demonstrated serotype specific immunity with minimal serum cross-reactivity and reduced ADE compared to a live DENV1 viral infection. IMPORTANCEWith 400 million worldwide infections each year, dengue is the most common vector-born viral disease. 40% of the worlds population is at risk with dengue experiencing consistent geographic spread over the years. With no therapeutics available and vaccines performing sub optimally, the need for an effective dengue vaccine is urgent. Here we develop and characterize a novel mRNA vaccine encoding for the dengue serotype 1 envelope and premembrane structural proteins that is delivered via a lipid nanoparticle. Our DENV1 prM/E mRNA-LNP vaccine induces neutralizing antibody and cellular immune responses in immunocompetent mice and protects an immunocompromised mouse from a lethal DENV challenge. Existing antibodies against dengue can enhance subsequent infections via antibody-dependent enhancement. Importantly our vaccine only induced serotype specific immune responses and did not induce ADE.

microbiology↗

bioRxiv2020

mRNA induced expression of human angiotensin-converting enzyme 2 in mice for the study of the adaptive immune response to severe acute respiratory syndrome coronavirus 2

The novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic resulting in nearly 20 million infections across the globe, as of August 2020. Critical to the rapid evaluation of vaccines and antivirals is the development of tractable animal models of infection. The use of common laboratory strains of mice to this end is hindered by significant divergence of the angiotensin-converting enzyme 2 (ACE2), which is the receptor required for entry of SARS-CoV-2. In the current study, we designed and utilized an mRNA-based transfection system to induce expression of the hACE2 receptor in order to confer entry of SARS-CoV-2 in otherwise non-permissive cells. By employing this expression system in an in vivo setting, we were able to interrogate the adaptive immune response to SARS-CoV-2 in type 1 interferon receptor deficient mice. In doing so, we showed that the T cell response to SARS-CoV-2 is enhanced when hACE2 is expressed during infection. Moreover, we demonstrated that these responses are preserved in memory and are boosted upon secondary infection. Interestingly, we did not observe an enhancement of SARS-CoV-2 specific antibody responses with hACE2 induction. Importantly, using this system, we functionally identified the CD4+ and CD8+ peptide epitopes targeted during SARS-CoV-2 infection in H2b restricted mice. Antigen-specific CD8+ T cells in mice of this MHC haplotype primarily target peptides of the spike and membrane proteins, while the antigen-specific CD4+ T cells target peptides of the nucleocapsid, membrane, and spike proteins. The functional identification of these T cell epitopes will be critical for evaluation of vaccine efficacy in murine models of SARS-CoV-2. The use of this tractable expression system has the potential to be used in other instances of emerging infections in which the rapid development of an animal model is hindered by a lack of host susceptibility factors.

immunology↗