Quantification of SARS-CoV-2 neutralizing antibody by wild-type plaque reduction neutralization, microneutralization and pseudotyped virus neutralization assays.

Virus neutralization assays measure neutralizing antibodies in serum and plasma, and the plaque reduction neutralization test (PRNT) is considered the gold standard for measuring levels of these antibodies for many viral diseases. We have developed procedures for the standard PRNT, microneutralization assay (MNA) and pseudotyped virus neutralization assay (PNA) for severe acute respiratory syndrome coronavirus 2. The MNA offers advantages over the PRNT by reducing assay time, allowing increased throughput and reducing operator workload while remaining dependent upon the use of wild-type virus. This ensures that all severe acute respiratory syndrome coronavirus 2 antigens are present, but Biosafety Level 3 facilities are required. In addition to the advantages of MNA, PNA can be performed with lower biocontainment (Biosafety Level 2 facilities) and allows for further increases in throughput. For each new vaccine, it is critical to ensure good correlation of the neutralizing activity measured using PNA against the PRNT or MNA. These assays have been used in the development and licensure of the ChAdOx1 nCoV-19 (AstraZeneca; Oxford University) and Ad26.COV2.S (Janssen) coronavirus disease 2019 vaccines and are critical for demonstrating bioequivalence of future vaccines.

Mutations in the spike glycoprotein of human coronavirus OC43 modulate disease in BALB/c mice from encephalitis to flaccid paralysis and demyelination.

The etiology of most neurodegenerative diseases of the central nervous system remains unknown and likely involves a combination of genetic susceptibility and environmental triggering factors. Given that exposure to numerous infectious pathogens occurs during childhood, and that some viral infections can lead to neurodegeneration and demyelination, it is conceivable that some viruses may act as triggering factors in neuropathogenesis. We have previously shown that the prototype OC43 strain of the common cold-associated human respiratory coronavirus has the capacity to infect human neuronal and glial cells and does persist in human brains. Moreover, it has neuroinvasive properties in susceptible BALB/c mice, where it leads to a chronic encephalitis with accompanying disabilities. Here, we show that mutations in the viral spike glycoprotein, reproducibly acquired during viral persistence in human neural cell cultures, led to a drastically modified virus-induced neuropathology in BALB/c mice, characterized by flaccid paralysis and demyelination. Even though infection by both mutated and wild-type viruses led to neuroinflammation, the modified neuropathogenesis induced by the mutated virus was associated with increased viral spread and significantly more CD4+ and CD8+ T-lymphocyte infiltration into the central nervous system, as well as significantly increased levels of the proinflammatory cytokine interleukin (IL)-6 and the chemokine CCL2 (monocyte chemoattractant protein [MCP]-1). Moreover, recombinant virus harboring the S glycoprotein mutations retained its neurotropism, productively infecting neurons. Therefore, interaction of a human respiratory coronavirus with the central nervous system may modulate virus and host factors resulting in a modified neuropathogenesis in genetically susceptible individuals.

Evaluation of novel synthetic TLR7/8 agonists as vaccine adjuvants.

Small-molecule adjuvants that boost and direct adaptive immunity provide a powerful means to increase the effectiveness of vaccines. Through rational design several novel imidazoquinoline and oxoadenine TLR7/8 agonists, each with unique molecular modifications, were synthesized and assessed for their ability to augment adaptive immunity. All agonists bound human TLR7 and TLR8 and induced maturation of both human mDCs and pDCs. All agonists prompted production of type I interferon and/or proinflammatory cytokines, albeit with varying potencies. In most in vitro assays, the oxoadenine class of agonists proved more potent than the imidazoquinolines. Therefore, an optimized oxoadenine TLR7/8 agonist that demonstrated maximal activity in the in vitro assays was further assessed in a vaccine study with the CRM197 antigen in a porcine model. Antigen-specific antibody production was greatly enhanced in a dose dependent manner, with antibody titers increased 800-fold compared to titers from pigs vaccinated with the non-adjuvanted vaccine. Moreover, pigs vaccinated with antigen containing the highest dose of adjuvant promoted a 13-fold increase in the percentage of antigen-specific CD3(+)/CD8(+) T cells over pigs vaccinated with antigen alone. Together this work demonstrates the promise of these novel TLR7/8 agonists as effective human vaccine adjuvants.

Methods to monitor monocytes-mediated amyloid-beta uptake and phagocytosis in the context of adjuvanted immunotherapies.

Antibody-mediated capture of amyloid-beta (Aß) in peripheral blood was identified as an attractive strategy to eliminate cerebral toxic amyloid in Alzheimer's disease (AD) patients and murine models. Alternatively, defective capacity of peripheral monocytes to engulf Aß was reported in individuals with AD. In this report, we developed different approaches to investigate cellular uptake and phagocytosis of Aß, and to examine how two immunological devices--an immunostimulatory Adjuvant System and different amyloid specific antibodies--may affect these biological events. Between one and thirteen months of age, APPswe X PS1.M146V (TASTPM) AD model mice had decreasing concentrations of Aß in their plasma. In contrast, the proportion of blood monocytes containing Aß tended to increase with age. Importantly, the TLR-agonist containing Adjuvant System AS01B primed monocytes to promote de novo Aß uptake capacity, particularly in the presence of anti-Aß antibodies. Biochemical experiments demonstrated that cells achieved Aß uptake and internalization followed by Aß degradation via mechanisms that required effective actin polymerization and proteolytic enzymes such as insulin-degrading enzyme. We further demonstrated that both Aß-specific monoclonal antibodies and plasma from Aß-immunized mice enhanced the phagocytosis of 1 µm Aß-coated particles. Together, our data highlight a new biomarker testing to follow amyloid clearance within the blood and a mechanism of Aß uptake by peripheral monocytes in the context of active or passive immunization, and emphasize on novel approaches to investigate this phenomenon.

Yeast one-hybrid screen of a thymus epithelial library identifies ZBTB7A as a regulator of thymic insulin expression.

Insulin self-tolerance is, to a large extent, assured by the expression of small quantities of insulin by medullary thymic epithelial cells (mTECs). Regulation of thymic insulin expression differs from that in pancreas and its therapeutic manipulation could play an important role in the prevention of type 1 diabetes (T1D). Knowledge of the transcriptional regulators involved in the mTEC nuclear environment is essential for the development of such therapeutics. The yeast one-hybrid (Y1H) approach was used in order to identify such mTEC-specific nuclear proteins. We used a target composed of the human insulin gene promoter joined to the upstream class III VNTR allele, which is associated with both protection from T1D and higher thymic insulin expression, and a cDNA library from our insulin-producing mouse mTEC line. The Y1H screening allowed the identification of eleven proteins. An in vitro assay was used to confirm and quantify protein-DNA binding to the human insulin gene promoter alone or joined to a class I or class III VNTR allele, and identified the transcription factors ZBTB7A, JUN and EWSR1 as strong interacting partners. All three proteins could induce insulin expression in transfected HEK-293 cells, but ZBTB7A provided the most robust results especially in the presence of AIRE, with an additional 11-fold increase of the insulin mRNA levels from a co-transfected reporter driven by the class III VNTR allele. Thus, ZBTB7A is identified as a strong candidate for regulation of thymic insulin expression.

A human coronavirus OC43 variant harboring persistence-associated mutations in the S glycoprotein differentially induces the unfolded protein response in human neurons as compared to wild-type virus.

We have reported that human respiratory coronavirus OC43 (HCoV-OC43) is neurotropic and neuroinvasive in humans and mice, and that neurons are the primary target of infection in mice, leading to neurodegenerative disabilities. We now report that an HCoV-OC43 mutant harboring two persistence-associated S glycoprotein point mutations (H183R and Y241H), induced a stronger unfolded protein response (UPR) and translation attenuation in infected human neurons. There was a major contribution of the IRE1/XBP1 pathway, followed by caspase-3 activation and nuclear fragmentation, with no significant role of the ATF6 and eIF2-alpha/ATF4 pathways. Our results show the importance of discrete molecular viral S determinants in virus-neuronal cell interactions that lead to increased production of viral proteins and infectious particles, enhanced UPR activation, and increased cytotoxicity and cell death. As this mutant virus is more neurovirulent in mice, our results also suggest that two mutations in the S glycoprotein could eventually modulate viral neuropathogenesis.

Recovery of a neurovirulent human coronavirus OC43 from an infectious cDNA clone.

This study describes the assembly of a full-length cDNA clone of human coronavirus (HCoV)-OC43 in a bacterial artificial chromosome (BAC). The BAC containing the full-length infectious cDNA (pBAC-OC43(FL)) was assembled using a two-part strategy. The first step consisted in the introduction of each end of the viral genome into the BAC with accessory sequences allowing proper transcription. The second step consisted in the insertion of the whole HCoV-OC43 cDNA genome into the BAC. To produce recombinant viral particles, pBAC-OC43(FL) was transfected into BHK-21 cells. Recombinant virus displayed the same phenotypic properties as the wild-type virus, including infectious virus titers produced in cell culture and neurovirulence in mice.

Human respiratory coronavirus OC43: genetic stability and neuroinvasion.

The complete genome sequences of the human coronavirus OC43 (HCoV-OC43) laboratory strain from the American Type Culture Collection (ATCC), and a HCoV-OC43 clinical isolate, designated Paris, were obtained. Both genomes are 30,713 nucleotides long, excluding the poly(A) tail, and only differ by 6 nucleotides. These six mutations are scattered throughout the genome and give rise to only two amino acid substitutions: one in the spike protein gene (I958F) and the other in the nucleocapsid protein gene (V81A). Furthermore, the two variants were shown to reach the central nervous system (CNS) after intranasal inoculation in BALB/c mice, demonstrating neuroinvasive properties. Even though the ATCC strain could penetrate the CNS more effectively than the Paris 2001 isolate, these results suggest that intrinsic neuroinvasive properties already existed for the HCoV-OC43 ATCC human respiratory isolate from the 1960s before it was propagated in newborn mouse brains. It also demonstrates that the molecular structure of HCoV-OC43 is very stable in the environment (the two variants were isolated ca. 40 years apart) despite virus shedding and chances of persistence in the host. The genomes of the two HCoV-OC43 variants display 71, 53.1, and 51.2% identity with those of mouse hepatitis virus A59, severe acute respiratory syndrome human coronavirus Tor2 strain (SARS-HCoV Tor2), and human coronavirus 229E (HCoV-229E), respectively. HCoV-OC43 also possesses well-conserved motifs with regard to the genome sequence of the SARS-HCoV Tor2, especially in open reading frame 1b. These results suggest that HCoV-OC43 and SARS-HCoV may share several important functional properties and that HCoV-OC43 may be used as a model to study the biology of SARS-HCoV without the need for level three biological facilities.