A multiplex serological assay for the characterization of IgG immune response to SARS-CoV-2

In the fight against SARS-COV-2, the development of serological assays based on different antigenic domains represent a versatile tool to get a comprehensive picture of the immune response or differentiate infection from vaccination beyond simple diagnosis. Here we use a combination of the Nucleoprotein (NP), the Spike 1 (S1) and Spike 2 (S2) subunits, and the receptor binding domain (RBD) and N-terminal domain (NTD) of the Spike antigens from the CoViDiag® multiplex IgG assay, to follow the immune response to SARS-CoV-2 infection over a long time period and depending on disease severity. Using a panel of 209 sera collected from 61 patients up to eight months after infection, we observed that most patients develop an immune response against multiple viral epitope, but anti-S2 antibodies seemed to last longer. For all the tested IgGs, we have found higher responses for hospitalized patients than for non-hospitalized ones. Moreover the combination of the five different IgG responses increased the correlation to the neutralizing antibody titers than if considered individually. Multiplex immunoassays have the potential to improve diagnostic performances, especially for ancient infection or mild form of the disease presenting weaker antibody responses. Also the combined detection of anti-NP and anti-Spike-derived domains can be useful to differentiate vaccination from viral infection and accurately assess the antibody potential to neutralize the virus.

A multiplex serological assay for the characterization of IgG immune response to SARS-CoV-2

Background: In the fight against SARS-COV-2, the development of serological assays based on different antigenic domains represent a versatile tool to get a comprehensive picture of the immune response or differentiate infection from vaccination beyond simple diagnosis. Objectives: Here we use a combination of the Nucleoprotein (NP), the Spike 1 (S1) and Spike 2 (S2) subunits, and the receptor binding domain (RBD) and N-terminal domain (NTD) of the Spike antigens from the Syrius-CoViDiag multiplex IgG assay, to follow the immune response to SARS-CoV-2 infection over a long time period and depending on disease severity. Results: Using a panel of 209 sera collected from 61 patients up to eight months after infection, we observed that most patients develop an immune response against multiple viral epitope, but anti-S2 antibodies seemed to last longer. For all the tested IgGs, we have found higher titers for hospitalized patients than for non-hospitalized ones. Moreover the combination of the five different IgG titers increased the correlation to the neutralizing antibody titers than if considered individually. Conclusion: Multiplex immunoassays have the potential to improve diagnostic performances, especially for ancient infection or mild form of the disease presenting weaker antibody titers. Also the combined detection of anti-NP and anti-Spike-derived domains can be useful to differentiate vaccination from viral infection and accurately assess the antibody potential to neutralize the virus.

Localization of Viral Epitope-Specific CD8 T Cells during Cytomegalovirus Latency in the Lungs and Recruitment to Lung Parenchyma by Airway Challenge Infection

Interstitial pneumonia is a life-threatening clinical manifestation of cytomegalovirus infection in recipients of hematopoietic cell transplantation (HCT). The mouse model of experimental HCT and infection with murine cytomegalovirus revealed that reconstitution of virus-specific CD8+ T cells is critical for resolving productive lung infection. CD8+ T-cell infiltrates persisted in the lungs after the establishment of latent infection. A subset defined by the phenotype KLRG1+CD62L− expanded over time, a phenomenon known as memory inflation (MI). Here we studied the localization of these inflationary T effector-memory cells (iTEM) by comparing their frequencies in the intravascular and transmigration compartments, the IVC and TMC, respectively, with their frequency in the extravascular compartment (EVC), the alveolar epithelium. Frequencies of viral epitope-specific iTEM were comparable in the IVC and TMC but were reduced in the EVC, corresponding to an increase in KLRG1−CD62L− conventional T effector-memory cells (cTEM) and a decrease in functional IFNγ+CD8+ T cells. As maintained expression of KLRG1 requires stimulation by antigen, we conclude that iTEM lose KLRG1 and convert to cTEM after transmigration into the EVC because pneumocytes are not latently infected and, therefore, do not express antigens. Accordingly, antigen re-expression upon airway challenge infection recruited virus-specific CD8+ T cells to TMC and EVC.

Antiviral Antibody Epitope Selection is a Heritable Trait

There is enormous variability in human immune responses to viral infections. However, the genetic factors that underlie this variability are not well characterized. We used VirScan, a high-throughput viral epitope scanning technology, to analyze the antibody binding specificities of twins and SNP-genotyped individuals. These data were used to estimate the heritability and identify genomic loci associated with antibody epitope selection, response breadth, and the control of Epstein-Barr Virus (EBV) viral load. We identified 4 epitopes of EBV that were heritably targeted, and at least two EBNA-2 binding specificities that were associated with variants in the MHC class-II locus. We identified an EBV serosignature that predicted viral load in white blood cells and was associated with genetic variants in the MHC class-I locus. Our study provides a new framework for identifying genes important for pathogen immunity, with specific implications for the genetic architecture of EBV humoral responses and the control of viral load.Abstract Figure

Rationally designed immunogens enable immune focusing to the SARS-CoV-2 receptor binding motif

Eliciting antibodies to surface-exposed viral glycoproteins can lead to protective responses that ultimately control and prevent future infections. Targeting functionally conserved epitopes may help reduce the likelihood of viral escape and aid in preventing the spread of related viruses with pandemic potential. One such functionally conserved viral epitope is the site to which a receptor must bind to facilitate viral entry. Here, we leveraged rational immunogen design strategies to focus humoral responses to the receptor binding motif (RBM) on the SARS-CoV-2 spike. Using glycan engineering and epitope scaffolding, we find an improved targeting of the serum response to the RBM in context of SARS-CoV-2 spike imprinting. Furthermore, we observed a robust SARS-CoV-2-neutralizing serum response with increased potency against related sarbecoviruses, SARS-CoV and WIV1-CoV. Thus, RBM focusing is a promising strategy to elicit breadth across emerging sarbecoviruses and represents an adaptable design approach for targeting conserved epitopes on other viral glycoproteins.

Codon Usage and Adenovirus Fitness: Implications for Vaccine Development

Vaccination is the most effective method to date to prevent viral diseases. It intends to mimic a naturally occurring infection while avoiding the disease, exposing our bodies to viral antigens to trigger an immune response that will protect us from future infections. Among different strategies for vaccine development, recombinant vaccines are one of the most efficient ones. Recombinant vaccines use safe viral vectors as vehicles and incorporate a transgenic antigen of the pathogen against which we intend to generate an immune response. These vaccines can be based on replication-deficient viruses or replication-competent viruses. While the most effective strategy involves replication-competent viruses, they must be attenuated to prevent any health hazard while guaranteeing a strong humoral and cellular immune response. Several attenuation strategies for adenoviral-based vaccine development have been contemplated over time. In this paper, we will review them and discuss novel approaches based on the principle that protein synthesis from individual genes can be modulated by codon usage bias manipulation. We will summarize vaccine approaches that consider recoding of viral proteins to produce adenoviral attenuation and recoding of the transgene antigens for both viral attenuation and efficient viral epitope expression.

Crystal structure of the classical MHC-I molecule: insights into the MHC-I system in antiviral diseases in dogs

Only one classical MHC-I locus (aka DLA-88) evolved in dogs, and thus far, a total of 76 DLA-88 alleles can be divided into two categories. The first category consists of 60 alleles, and the second category consists of 16 alleles. The main difference between the two categories is the insertion of an amino acid in the α2 region of DLA-88 alleles. To elucidate the structure of the first category, in this study, the crystal structure of pDLA-88*001:01 was determined for the first time. The 3D structure and topological characteristics of the ABG of pDLA-88*001:01 with a CDV peptide were analyzed. The viral presentation profile and the binding motif of viruses presented by pDLA-88*001:01 were determined. Most importantly, there were no amino acid insertions in the α2 region of the first category, which changed the conformation of the D pocket and the docking of the TCR. The results suggest obvious differences between the two categories. Because of the variation in the α2 region, pDLA-88*001:01 showed distinctive features in the two categories. Due to the peptide-binding motif of pDLA-88*001:01, more than 320 high-affinity viral peptides were predicted from dog H7N9, CPV, CMV, CMV, and CDV strains. The results reveal that there are two kinds of structural MHC-I systems in dogs that are responsible for CTL immunity against viral diseases. The results provide knowledge for designing viral epitope vaccines in canines.ImportanceDLA plays an important role in the acquired immunity of organism. In previous study, the pMHC-I structure of dog was analyzed with DLA-88 self-peptide. In this study, we screened several viral peptides which can bind to DLA-88 and resolved the structure of the DLA-88 complex binding the CDV peptide. This study enriches the study of canine MHC-I molecular-presenting polypeptide-activated TCR, which is of great significance for the study of canine cellular immunity and anti-viral vaccine development.

ACE2-Targeting Monoclonal Antibody As A “Pan” Coronavirus Blocker In Vitro and In A Mouse Model

Coronaviruses have caused three major outbreaks of infectious disease since the beginning of 21st century. Broad-spectrum strategies that can be utilized in both current and future coronavirus outbreaks and mutation-tolerant are sought after. Here we report a monoclonal antibody 3E8 targeting human angiotensin-converting enzyme 2 (ACE2) neutralized pseudo-typed coronaviruse SARS-CoV-2, SARS-CoV-2-D614G, SARS-CoV and HCoV-NL63, without affecting physiological activities of ACE2 or causing toxicity in mouse model. 3E8 also blocked live SARS-CoV-2 infection in vitro and in a mouse model of COVID-19. Cryo-EM studies revealed the binding site of 3E8 on ACE2 and identified Histone 34 of ACE2 as a critical site of anti-viral epitope. Overall, our work has provided a potential “pan” coronavirus management strategy and disclosed a “pan” anti-coronavirus epitope on human ACE2 for the first time.SummaryBlocking Multiple Coronaviruses by An ACE2-Neutralizing Monoclonal Antibody