Thesis advisor: Jianman Gao / The interaction between the spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the human angiotensin-converting enzyme 2 (hACE2) receptor is an advantageous target for the development of therapies for COVID-19. We used an anti spike receptor binding domain (S RBD) antibody (AM122) to competitively elute phage binding to the S RBD in phage display screening to identify a novel peptide that binds the S protein and hACE2 interaction. We identified a peptide sequence (P1: CPLEYHTC) as a possible hit, and the KD was determined to be 2.667 μM, indicating the potential of this peptide sequence as a therapeutic agent. However, we found no inhibition of the spike protein and hACE2 receptor interaction, suggesting that the peptide may not directly bind to the hACE2 binding site on S RBD. Although further studies are needed, the competitive elution method in phage display screening appears to be an effective method for elucidating onsite peptide sequences that target protein-protein interactions (PPIs). / Thesis (BA) — Boston College, 2023. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Chemistry.

Zehn Jahre nach dem Ausbruch des Severe Acute Respiratory Syndrome Coronavirus, SARS-CoV, ist ein neues Betacoronavirus, das Middle East Respiratory Syndrome Coronavirus, MERS-CoV, auf der arabischen Halbinsel entdeckt worden. Seine anhaltende Ausbreitung stellt eine Bedrohung für die öffentliche Gesundheit dar. Das Spike (S) Protein der Coronaviren vermittelt den viralen Eintritt in Wirtszellen und bestimmt wesentlich den viralen Tropismus und die virale Pathogenese. Das Verständnis der Determinanten des MERS-CoV Spike (MERS-S)-vermittelnden Eintritts in Zellen könnte daher wichtige Einblicke in die MERS-CoV-Biologie liefern und war somit das erste Ziel dieser Arbeit. Um den Eintritt in die Zelle zu ermöglichen, muss das Coronavirus S-Protein durch Wirtszellproteasen aktiviert werden, welche potentielle Ziele für die therapeutischen Intervention darstellen. Daher sollten im zweiten Ziel dieser Arbeit Proteasen identifiziert werden, die MERS-S aktivieren. Das S-Protein ist das Hauptangriffsziel neutralisierender Antikörper und experimentelle Systeme zur S-Analyse können für die Diagnostik eingesetzt werden. Das letzte Ziel dieser Arbeit war es daher, die MERS-CoV Seroprävalenz in Saudi Arabien zu ermitteln. Es wurde ein lentivirales Vektorensystem etabliert, welches die Analyse des MERS-S-getriebenen Zelleintritts ermöglicht. Mit Hilfe dieses Systems konnte gezeigt werden, dass MERS-S den Eintritt in ein breites Spektrum humaner Zelllinien, wie Lungen-, Nieren- und Darmzellen vermittelt, was mit der klinischen Manifestation von MERS einhergeht. Der Wirtszelleintritt war unabhängig von bereits beschriebenen Coronavirus Eintrittsrezeptoren, wurde jedoch durch die endosomale Cysteinprotease Cathepsin L und die Transmembranserinprotease TMPRSS2 gefördert. Im Gegensatz dazu war die Aktivität von Proprotein Konvertasen für den S-Protein-vermittelnden Eintritt entbehrlich. Schließlich zeigten Neutralisationstests, dass Seren von Patienten aus der östlichen Provinz Saudi Arabiens, die zwischen 2010-2011 und 2012 entnommen wurden, keine MERS-S-neutralisierenden Antikörper enthielten. Dies deutet darauf hin, dass MERS-CoV-Infektionen vor dem Ausbruch 2012 nur selten vorkamen. Die gewonnen Ergebnisse tragen wesentlich zum Verständnis des MERS-CoV-Eintritts in Zellen bei und liefern wichtige Informationen zur MERS-CoV-Epidemiologie. Weiterhin könnte die Beobachtung, dass der Protease-Inhibitor Camostat, der für den Einsatz im Menschen zugelassen ist (in Japan), TMPRSS2 blockiert und damit den MERS-CoV Eintritt inhibiert, helfen, Behandlungsstrategien für MERS-Patienten zu etablieren.

Le coronavirus humain 229E (HCoV-229E) est responsable de rhumes mais peut entraîner de graves complications respiratoires chez les personnes âgées ou atteintes d’une maladie Chronique. Les coronavirus sont des virus enveloppés avec un génome à ARN positif simple brin. Trois protéines virales sont ancrées dans l'enveloppe virale : la protéine spike (S), la protéine de membrane (M) et la protéine d’enveloppe (E). Les protéines M et E sont impliquées dans l'assemblage viral et la sécrétion. La protéine S s'assemble en trimères à la surface des virions et joue un rôle-clé dans l’entrée du virus dans sa cellule-cible. Elle est constituée de deux domaines, le domaine S1 responsable de la liaison du virus à son récepteur et le domaine S2 responsable de la fusion de l’enveloppe virale avec une membrane cellulaire. La fusion est activée par des protéases cellulaires par clivage de la protéine S. Dans un premier temps nous avons caractérisé ce mécanisme. Pour cela, nous avons d'abord cloné la protéine S d’un isolat circulant de HCoV-229E. Nous avons analysé le clivage protéolytique de la protéine S par des sérine-protéases de type trypsine conduisant au processus de fusion à l’aide de particules pseudotypées rétrovirales. Les Résidus arginine, sites potentiels de reconnaissance par les protéases et présents au niveau de la jonction S1/S2 ou de la région S2’ ont été mutés individuellement (R565N, R679N, R683N ou R687N) afin d’étudier leur rôle lors de l'activation de la fusion. Contrairement à d'autres coronavirus, l'activation permettant la fusion de HCoV-229E semble être un processus en une seule étape. En effet, seule la mutation R683N inhibe l’infection médiée par des sérine-protéases et le clivage à l'interface S1/S2 ne semble pas être un pré-requis. Les protéines S de coronavirus sont fortement N-glycosylées et constituent la principale cible des anticorps neutralisants. Nous avons analysé le rôle de la N-glycosylation du domaine S1 dans les mécanismes d'entrée et dans la neutralisation par des anticorps. L'analyse de la séquence de la protéine clonée montre la présence de 33 sites potentiels de N-glycosylation, dont 18 dans le domaine S1 qui ont été numérotés de N1 à N18. Ces 18 sites de N-glycosylation ont été abolis individuellement par mutagenèse dirigée. L’effet des mutations sur l'infectiosité virale a été évalué en utilisant des particules pseudotypées rétrovirales. L'infectiosité des mutants N6, N7 ou N9 est diminuée tandis que deux mutants N12 et N15 montrent une augmentation de l'infectiosité. Nous n'avons détecté aucune différence d'interaction de ces mutants avec une forme soluble du récepteur, l'aminopeptidase N (APN). Des expériences d’activation de la fusion virale à la surface cellulaire par la trypsine suggèrent que les glycanes présents aux positions 6, 7 et 9 sont impliquées dans la fusion virale, cependant nous n’avons détecté aucune différence de clivage de ces mutants par la trypsine. Pour le mutant N17 uniquement, la diminution partielle de l'infectiosité pourrait s'expliquer par une diminution de l'incorporation de la protéine S dans les pseudoparticules, due au mauvais repliement de la protéine, comme le montre le profil du mutant en western blot en conditions réductrices ou non.Nous avons ensuite évalué si les N-glycanes pouvaient moduler la reconnaissance de la protéine S par des anticorps neutralisants. Des pseudoparticules contenant les différents mutants ont été produites et utilisées pour infecter des cellules en présence d'anticorps neutralisants. Nos données montrent que les mutants N4, N10, N11, N12, N15, N16, N17, N18 réduisent la sensibilité des pseudoparticules à la neutralisation des anticorps. Dans ensemble, nos résultats suggèrent que les N-glycanes de la protéine S jouent un rôle important dans l'entrée virale et modulent la reconnaissance de la protéine par des anticorps neutralisants. / The human coronavirus 229E (HCoV-229E) is a causative agent of common colds and can lead to severe respiratory complications in elderly persons and those with underlying disease. Coronavirus are enveloped viruses with a single stranded, positive-sense RNA genome. Three viral proteins are anchored in the viral enveloppe : the spike (S) protein, the membrane (M) protein and the enveloppe (E) protein. The M and E proteins are involved in viral assembly and secretion. The spike proteins assemble into trimers at the surface of the virions and play a key role in the early steps of viral infection. The spike protein comprised two domains, the S1 domain responsible for receptor binding and the S2 domain responsible for fusion of the viral enveloppe with the host cell membrane. Coronavirus fusion is activated by the proteolytic processing of the spike protein. First, we charaterized the proteolytic processing of the HCoV-229E spike protein by trypsin-like serine-proteases. To do so, we first cloned the spike protein of a circulating isolate of HCoV-229E. To investigate the role of the S1/S2 junction and the specific role of the 3 arginine residues located in the S2’ region in the proteolytic activation of HCoV-229E spike protein, the arginine residues present at these positions were mutated individually (R565N, R679N, R683N or R687N). Our results show that unlike other coronaviruses, HCoV-229E fusion activation appears to be a one step process. Indeed, the cleavage of the S1/S2 interface does not seem to be a pre-requisite, and the fusion activation strongly relies on the S2’ region, with R683 acting as the cleavage site.The spike protein is highly N-glycosylated and is the main target of neutralizing antibodies. We analysed the role of S1 domain N-glycosylation in the entry functions of the S protein and in neutralization by antibodies. Analysis of the sequence of the cloned protein shows the presence of 33 potential N-glycosylation sites, 18 being located in the S1 domain (numbered from N1 to N18). We mutated the 18 N-glycosylation sites of S1 individually by site-directed mutagenesis and studied the effect of the mutations using retroviral pseudotyped particles. Infectivity of the spike proteins with mutation either at the N6, N7 or N9 glycosylation site was strongly impaired. We did not detect any difference of interaction of these mutants with the soluble form of the receptor, the aminopeptidase N (APN). Results obtained by inducing the fusion of pseudoparticles at the cell surface with trypsin suggest that N-glycans located at the position N6, N7 and N9 are involved in viral fusion. However, the proteolytic processing of the protein required for fusion activation does not seem to be affected. Two mutants N12 and N15 show an increase of infectivity. Mutation of the N-glycosylation site N17 induces a partial decrease in infectivity. Indeed a decrease of spike protein incorporation into pseudoparticles was observed likely due to misfolding of the protein as shown by the profile of the mutant in western blot under reducing and non-reducing conditions. We next assessed if N-glycans can modulate the recognition of the spike protein by neutralizing antibodies. Pseudoparticles harbouring the different mutants were produced and used to infect cells in presence or absence of neutralizing antibodies. Our data demonstrate that mutants N4, N10, N11, N12, N15, N16, N17, N18 reduce the sensitivity of pseudoparticules to antibody neutralization. Taken together our results suggest that N-glycans of the S protein play an important role in viral entry and modulate the recognition of the protein by neutralizing antibodies.

Introduction: The coronavirus is an RNA virus with a lipid envelope. The initially known coronaviruses are (MERS-CoV and SARS-CoV) which caused fatal endemics in 2002 and 2012. At the end of 2019, a new variant of coronavirus called SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) was discovered in Wuhan in China. SARS-CoV-2 has caused serious diseases especially in the older groups with millions of infections and deaths. The World Health Organization (WHO) identified Covid-19 as a global health emergency on 30 January 2020 and classified it as a pandemic on March 11, 2020. Several companies started developing a vaccine to stop the spread of SARS-CoV-2. Several vaccination programs have been approved and are currently used against Covid-19. Objectives: The work aimed to investigate the safety and efficacy of the approved mRNA-based vaccines against SARS-CoV-2. Method: The work was based on reviewing published, scientific articles that examined safety and efficacy of mRNA-based vaccines (Pfizer BionTech BNT162b and mRNA-1273 Modern). In total there were five clinical trials selected from Pubmed. Two studies examined the safety and efficacy of mRNA-1273 Moderna and three other studies examined the safety and effectiveness of the Pfizer BionTech BNT162b. Results: Both vaccines have shown good safety and efficacy and were well tolerated in patients in different ages. mRNA-based vaccines have shown mild to moderate symptoms that were higher after dose 2 and disappeared after a few days. Both Pfizer BionTech and Modern mRNA-1273 have shown efficiencies over 90%.

No description available.

A Bronquite Infecciosa das Aves (BIG) é uma das doenças respiratórias aviárias de maior impacto na avicultura mundial. No Brasil, as estirpes BR-I (GI-11) e Massachusetts (GI-1) são as mais prevalentes nos planteis avícolas. O presente estudo teve como objetivos desenvolver reações de semi-nested PCR para o diagnóstico das estirpes BR-I e Mass, em amostras brasileiras obtidas durante o período de 2016 e 2017. Foram desenvolvidas duas reações de semi-nested PCR tendo como alvo a subunidade 1 do gene S, específicas para as estirpes BR-I e Mass. O limiar de detecção foi de 104 cópias de DNA/µL nas duas reações (3,76fg/µL na reação exclusiva de BR-I; e 5,58fg/µL e 5,57fg/µL na reação duplex de BR-I e Mass, respectivamente). Posteriormente, foram avaliados 572 pools de órgãos procedentes das 5 regiões do Brasil. Dentre estas amostras, 62,24% foram positivas para Coronavírus, sendo o alvo desta reação a região 3UTR. A reação de semi-nested PCR específica detectou a estirpe BR-I em 84,83% das amostras positivas para Coronavírus. A reação de semi-nested PCR duplex detectou 65,44% das amostras positivas para a estirpe BR-I; 7,35% positivas para a estirpe Mass e co-infecção da estirpe BR-I com Mass em 17,65% das amostras. Após a análise dos controles positivos (vacinas Mass e BR-I) no BLASTn, do resultado do sequenciamento dos produtos de PCR, da análise filogenética, da similaridade de nucleotídeos e a dedução em aminoácidos, foi confirmado o agrupamento esperado das sequências detectadas pelas reações PCR dirigidas para a estirpe BR-I ou Mass. Estes resultados confirmaram a presença predominante da estirpe BR-I, e em menor número, da estirpe Mass nos planteis avícolas do Brasil. As reações desenvolvidas no presente estudo serão valiosas no diagnóstico e na monitoria da doença. / Avian Infectious Bronchitis (IB) is one of the avian respiratory diseases with the greatest impact on poultry farming worldwide. In Brazil, strains BR-I (GI-11) and Massachusetts (GI-1) are the most prevalent in poultry flocks. The present study aimed to develop semi-nested PCR reactions for the diagnosis of IBV BR-I and Mass strains, in Brazilian samples obtained during the period of 2016 and 2017. Two semi-nested PCR reactions targeting the 1 subunit of the S gene were developed, specific for BR-I and Mass strains. The detection threshold was 104 copies of DNA/µL in both reactions (3,76fg/µL in the exclusive BR-I reaction; and 5,58fg/µL and 5,57fg/µL in the duplex reaction of BR-I and Mass, respectively). Subsequently, 572 organ pools from the 5 regions of Brazil were evaluated. Among these samples, 62,24% were positive for Coronavirus, being the target of this reaction the 3UTR region. The specific semi-nested PCR reaction detected the BR-I strain in 84,83% of the Coronavirus positive samples. The duplex semi-nested PCR reaction detected 65,44% of the samples positive for the BR-I strain, 7,35% positive for Mass strain, and co-infection of the BR-I and Mass strain in 17,65% of the samples. After the analysis of the positive controls (Mass and BR-I vaccines) in BLASTn, the result of the sequencing of the PCR products, phylogenetic analysis, nucleotide similarity and amino acid deduction, was confirmed the expected clustering of the sequences detected by the PCR reactions directed to BR-I and Mass strains. These results confirm the predominant presence of the BR-I strain, and to a lesser extent, the Mass strain in Brazilian poultry flocks. The reactions developed in the present study will be valuabe in the diagnosis and monitoring of the disease.

No description available.

There is an ongoing need for high-precision serological assays for the quantitation of anti-SARS-CoV-2 antibodies. Here, a trimeric SARS-CoV-2 spike (S) protein was used to develop an ELISA to quantify specific IgG antibodies present in serum, plasma, and dried blood spots (DBS) collected from infected patients or vaccine recipients. The quantitative S-ELISA was calibrated with international anti-SARS-CoV-2 immunoglobulin standards to provide test results in binding antibody units per mL (BAU/mL). The assay showed excellent linearity, precision, and accuracy. A sensitivity of 100% was shown for samples collected from 54 patients with confirmed SARS-CoV-2 infection more than 14 days after symptom onset or disease confirmation by RT-PCR and 58 vaccine recipients more than 14 days after vaccination. The assay specificity was 98.3%. Furthermore, antibody responses were measured in follow-up samples from vaccine recipients and infected patients. Most mRNA vaccine recipients had a similar response, with antibody generation starting 2–3 weeks after the first vaccination and maintaining positive for at least six months after a second vaccination. For most infected patients, the antibody titers increased during the second week after PCR confirmation. This S-ELISA can be used to quantify the seroprevalence of SARS-CoV-2 in the population exposed to the virus or vaccinated.

Der Eintritt von Influenza A Viren in Wirtszellen erfolgt anhand des Hämagglutinin (HA) Proteins. Neueste Entwicklungen zielen darauf ab, die fusionsinduzierende Konformations-änderung des HA und damit die Freisetzung des viralen Genoms in die Wirtszelle zu inhibieren. Der Fusionsprozess ist pH-abhängig da nur bei einem niedrigen pH-Wert (~5.0-6.0) die Protonierung bestimmter Reste innerhalb des HA eine Konformationsänderung, und somit die Membranfusion, auslöst. Die Identifizierung von konservierten, titrierbaren Resten und die Aufklärung der Strukturveränderungen im HA ermöglichen eine gezielte Entwicklung neuer antiviraler Medikamente. In dieser Arbeit wurden bestimmte Histidine im HA mittels umfassender experimenteller und theoretischer Methoden als potentielle pH-Sensoren untersucht. Dabei konnte das Histidin an Position 184 als wichtiger Schalter der pH-induzierten Konformationsänderung identifiziert werden. Außerdem bewirkte der Austausch des geladenen Rests an Position 216 in der Nähe des His184 eine Veränderung der pH-Abhängigkeit des H5 HA aufgrund der Beeinflussung des pKa-Werts des His184. Da die Mutation R216E im HA des hochpathogenen H5N1 Virus in allen Isolaten während der Vogelvirenseuche im Jahr 2003/04 detektiert wurde, deutet das Ergebnis daraufhin, dass diese Mutation zur Entstehung des hochvirulenten Vogelvirus und dessen Adaptierung an den Menschen beigetragen hat. In diesem Zusammenhang wurde auch der Einfluss der pH-Abhängigkeit des HA auf die Fusion und Infektiosität von Viren in lebenden Zellen getestet. Eine destabilisierende Mutation im HA eines rekombinanten WSN-H3 Virus reduzierte dessen Infektions- und Replikationseffizienz in MDCK-Zellen, was auf den endosomalen pH-Wert dieser Zellen zurückgeführt werden konnte. Die Messung der Virus-Endosom-Fusionskinetik in lebenden Zellen machte außerdem die Bedeutung der pH-Abhängigkeit des HA für den Zeitpunkt der Membranfusion und dessen Einfluss auf die Effizienz der Virusinfektion deutlich. / The entry of influenza A virus into host cells is established by the hemagglutinin (HA) protein. New antiviral strategies aim to inhibit the fusion inducing conformational change of HA and thereby liberation of the viral genome into the cell. This process is strictly pH dependent since the conformational change of HA initiating the fusion of membranes only occurs upon protonation of yet unknown residues within HA at low pH (~5.0-6.0). The identification of conserved titrable residues and better understanding of the sequential structural rearrangements within HA may facilitate the development of new broad-spectrum antivirals. In the present work His184 and His110 were characterized as potential pH sensors by a comprehensive mutational and computational analysis. The results suggest that His184, but not His110, is an important regulator of HA conformational change at low pH. Furthermore, an exchange of charge at position 216 in vicinity to His184 was shown to alter the pH dependence of conformational change and of fusion in correlation to the known pKa dependence of histidines on neighboring residues. The result advocates that the mutation R216E, which emerged in the highly pathogenic H5 HA in 2003-2004, contributed to an altered acid stability of H5 HA via its effect on His184 and thus to the adaptation of avian H5N1 viruses to the human host. Therefore, the role of an altered acid stability of HA for viral fusion and infectivity in living cells was assessed. Recombinant viruses containing a destabilizing mutation in the HA protein were found to have a reduced infectivity and replication efficiency in MDCK cells compared to the respective wild type. Studying virus-endosome fusion kinetics in these cells we could resolve a significant difference in the timing of fusion induction suggesting that the time-point of fusion is a critical determinant of viral infection efficiency which depends on the endosomal acidification as well as on the acid stability of HA.

IntroductionSars-CoV-2 (severe acute respiratory syndrome coronavirus-2) is an RNA virus that causes Covid-19 disease. This disease started in the city of Wuhan in China. This is not the first time that the coronavirus has caused an outbreak, in the last twenty years the coronavirus SARS-CoV (Severe Acute Respiratory Syndrome coronavirus) and MERSCoV (Middle East Respiratory Syndrome coronavirus) have caused two major outbreaks. The main structure of SARS-CoV-2 is built from membrane (M), envelope (E), nucleocapsid (N) and spike (S). When the body is infected by the virus, the virus enters the host cells by binding to the ACE2 receptor. Once the virus has entered the cell, it releases viral RNA. The virus's particles multiply inside the cell. New virus particles from the infected cell are produced, which in its turn infect new cells. The immune system against SARS-CoV-2 involves both the cellular and humoral arms, with neutralizing antibodies directed primarily against the S antigen.ObjectivesThis research aimed to study the litteratur describing how long the antibodies and memory cells remain in the blood, and how long the protection against the virus lasts.MethodThis work was based on six scientific articles to answer the question: How long protective antibody levels last in the plasma after resolution of a Covid-19 infection? To answer the question, the levels of the antibodies of different classes, IgG, IgM and IgA, against the receptorbinding domain (RBD)/ S, N protein were analysed as reported in litterature, as well as the reported amounts of T memory cells and B memory cells.ResultsHumans produce SARS-CoV-2-specific antibodies, especially IgM and IgG antibodies, and T cells response to SARS-CoV-2 infection. IgG and IgM antibody levels were higher in patients whith severe Covid-19 than in mild cases. Studies cohort included patients from 18 to 90 years old. The studies lasted on from three months and up to one year.