SARS-CoV-2 Virus like Particles produced by a single recombinant baculovirus generate potent neutralizing antibody that protects against variant challenge

The Covid-19 pandemic caused by SARS-CoV-2 infection has highlighted the need for the rapid generation of efficient vaccines for emerging disease. Virus-like particles, VLPs, are an established vaccine technology that produces virus-like mimics, based on expression of the structural proteins of a target virus that can stimulate strong neutralizing antibody responses. SARS-CoV-2 is a coronavirus where the basis of VLP formation has been shown to be the co-expression of the spike, membrane and envelope structural proteins. Here we describe the generation of SARS-CoV-2 VLPs by the co expression of the salient structural proteins in insect cells using the established baculovirus expression system. VLPs were heterologous ~100nm diameter enveloped particles with a distinct fringe that reacted strongly with SARS-CoV-2 convalescent sera. In a Syrian hamster challenge model, a non adjuvanted VLPs induced neutralizing antibodies to the VLP-associated Wuhan S protein, reduced virus shedding following a virulent challenge with SARS-CoV-2 (B.1.1.7 variant) and protected against disease associated weight loss. Immunized animals showed reduced lung pathology and lower challenge virus replication than the non-immunized controls. Our data, using an established and scalable technology, suggest SARS-CoV-2 VLPs offer an efficient vaccine that mitigates against virus load and prevents severe disease.

Download Full-text

Protein Vaccine Induces a Durable, More Broadly Neutralizing Antibody Response in Macaques than Natural Infection with SARS-CoV-2 P.1

10.1101/2021.09.24.461759 ◽

2021 ◽

Author(s):

Albert To ◽

Teri Ann S Wong ◽

Michael M Lieberman ◽

Karen S Thompson ◽

Laurent Pessaint ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Subunit Vaccine ◽

Viral Vector ◽

Protective Efficacy ◽

Natural Infection ◽

Severe Disease ◽

Neutralizing Antibody ◽

Lung Pathology ◽

Recombinant Subunit Vaccine ◽

Broadly Neutralizing Antibody

FDA-approved and Emergency Use Authorized (EUA) vaccines using new mRNA and viral-vector technology are highly effective in preventing moderate to severe disease, however, information on their long-term efficacy and protective breadth against SARS-CoV-2 Variants of Concern (VOCs) is currently scarce. Here we describe the durability and broad-spectrum VOC immunity of a prefusion-stabilized spike (S) protein adjuvanted with liquid or lyophilized CoVaccine HTTM in cynomolgus macaques. This recombinant subunit vaccine is highly immunogenic and induces robust spike-specific and broadly neutralizing antibody responses effective against circulating VOCs (B.1.351 [Beta], P.1 [Gamma], B.1.617 [Delta]) for at least 3 months after the final boost. Protective efficacy and post-exposure immunity were evaluated using a heterologous P.1 challenge nearly 3 months after the last immunization. Our results indicate that while immunization with both high and low S doses shorten and reduce viral loads in the upper and lower respiratory tract, a higher antigen dose is required to provide durable protection against disease as vaccine immunity wanes. Histologically, P.1 infection causes similar COVID-19-like lung pathology as seen with early pandemic isolates. Post-challenge IgG concentrations were restored to peak immunity levels and vaccine-matched and cross-variant neutralizing antibodies were significantly elevated in immunized macaques indicating an efficient anamnestic response. Only low levels of P.1-specific neutralizing antibodies with limited breadth were observed in control (non-vaccinated but challenged) macaques suggesting that natural infection may not prevent reinfection by other VOCs. Overall, these results demonstrate that a properly dosed and adjuvanted recombinant subunit vaccine can provide long-lasting and protective immunity against circulating VOCs.

Download Full-text

Neutralizing Antibody Therapeutics for COVID-19

Viruses ◽

10.3390/v13040628 ◽

2021 ◽

Vol 13 (4) ◽

pp. 628

Author(s):

Aeron C. Hurt ◽

Adam K. Wheatley

Keyword(s):

High Risk ◽

Neutralizing Antibodies ◽

Controlled Trial ◽

Antiviral Treatment ◽

Severe Disease ◽

Neutralizing Antibody ◽

Supplemental Oxygen ◽

European Medicines Agency ◽

Global Public Health ◽

Public Health Burden

The emergence of SARS-CoV-2 and subsequent COVID-19 pandemic has resulted in a significant global public health burden, leading to an urgent need for effective therapeutic strategies. In this article, we review the role of SARS-CoV-2 neutralizing antibodies (nAbs) in the clinical management of COVID-19 and provide an overview of recent randomized controlled trial data evaluating nAbs in the ambulatory, hospitalized and prophylaxis settings. Two nAb cocktails (casirivimab/imdevimab and bamlanivimab/etesevimab) and one nAb monotherapy (bamlanivimab) have been granted Emergency Use Authorization by the US Food and Drug Administration for the treatment of ambulatory patients who have a high risk of progressing to severe disease, and the European Medicines Agency has similarly recommended both cocktails and bamlanivimab monotherapy for use in COVID-19 patients who do not require supplemental oxygen and who are at high risk of progressing to severe COVID-19. Efficacy of nAbs in hospitalized patients with COVID-19 has been varied, potentially highlighting the challenges of antiviral treatment in patients who have already progressed to severe disease. However, early data suggest a promising prophylactic role for nAbs in providing effective COVID-19 protection. We also review the risk of treatment-emergent antiviral resistant “escape” mutants and strategies to minimize their occurrence, discuss the susceptibility of newly emerging SARS-COV-2 variants to nAbs, as well as explore administration challenges and ways to improve patient access.

Download Full-text

SARS-CoV-2 RBD trimer protein adjuvanted with Alum-3M-052 protects from SARS-CoV-2 infection and immune pathology in the lung

Nature Communications ◽

10.1038/s41467-021-23942-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Nanda Kishore Routhu ◽

Narayanaiah Cheedarla ◽

Venkata Satish Bollimpelli ◽

Sailaja Gangadhara ◽

Venkata Viswanadh Edara ◽

...

Keyword(s):

Antibody Response ◽

Antibody Titer ◽

Neutralizing Antibodies ◽

Rhesus Macaques ◽

Neutralizing Antibody ◽

Significant Loss ◽

Lung Pathology ◽

Live Virus ◽

Suitable Candidate ◽

Immune Pathology

AbstractThere is a great need for the development of vaccines that induce potent and long-lasting protective immunity against SARS-CoV-2. Multimeric display of the antigen combined with potent adjuvant can enhance the potency and longevity of the antibody response. The receptor binding domain (RBD) of the spike protein is a primary target of neutralizing antibodies. Here, we developed a trimeric form of the RBD and show that it induces a potent neutralizing antibody response against live virus with diverse effector functions and provides protection against SARS-CoV-2 challenge in mice and rhesus macaques. The trimeric form induces higher neutralizing antibody titer compared to monomer with as low as 1μg antigen dose. In mice, adjuvanting the protein with a TLR7/8 agonist formulation alum-3M-052 induces 100-fold higher neutralizing antibody titer and superior protection from infection compared to alum. SARS-CoV-2 infection causes significant loss of innate cells and pathology in the lung, and vaccination protects from changes in innate cells and lung pathology. These results demonstrate RBD trimer protein as a suitable candidate for vaccine against SARS-CoV-2.

Download Full-text

Titers of Neutralizing Antibodies against SARS-CoV-2 Are Independent of Symptoms of Non-Severe COVID-19 in Young Adults

Viruses ◽

10.3390/v13020284 ◽

2021 ◽

Vol 13 (2) ◽

pp. 284

Author(s):

Hulda R. Jonsdottir ◽

Michel Bielecki ◽

Denise Siegrist ◽

Thomas W. Buehrer ◽

Roland Züst ◽

...

Keyword(s):

Young Adults ◽

Neutralizing Antibodies ◽

Severe Disease ◽

Humoral Response ◽

Neutralizing Antibody ◽

Neutralization Assay ◽

Asymptomatic Infection ◽

Homogeneous Population ◽

Humoral Immune ◽

Antibody Titers

Neutralizing antibodies are an important part of the humoral immune response to SARS-CoV-2. It is currently unclear to what extent such antibodies are produced after non-severe disease or asymptomatic infection. We studied a cluster of SARS-CoV-2 infections among a homogeneous population of 332 predominantly male Swiss soldiers and determined the neutralizing antibody response with a serum neutralization assay using a recombinant SARS-CoV-2-GFP. All patients with non-severe COVID-19 showed a swift humoral response within two weeks after the onset of symptoms, which remained stable for the duration of the study. One month after the outbreak, titers in COVID-19 convalescents did not differ from the titers of asymptomatically infected individuals. Furthermore, symptoms of COVID-19 did not correlate with neutralizing antibody titers. Therefore, we conclude that asymptomatic infection can induce the same humoral immunity as non-severe COVID-19 in young adults.

Download Full-text

Breakthrough of SIV strain smE660 challenge in SIV strain mac239-vaccinated rhesus macaques despite potent autologous neutralizing antibody responses

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1509731112 ◽

2015 ◽

Vol 112 (34) ◽

pp. 10780-10785 ◽

Cited By ~ 21

Author(s):

Samantha L. Burton ◽

Katie M. Kilgore ◽

S. Abigail Smith ◽

Sharmila Reddy ◽

Eric Hunter ◽

...

Keyword(s):

Simian Immunodeficiency Virus ◽

Neutralizing Antibodies ◽

Rhesus Macaques ◽

Neutralizing Antibody ◽

Active Immunization ◽

Antibody Responses ◽

Challenge Virus ◽

Gm Csf ◽

Immunodeficiency Virus

Although the correlates of immunological protection from human immunodeficiency virus or simian immunodeficiency virus infection remain incompletely understood, it is generally believed that medium to high titers of serum neutralizing antibodies (nAbs) against the challenge virus will prevent infection. This paradigm is based on a series of studies in which passive transfer of HIV-specific nAbs protected rhesus macaques (RMs) from subsequent mucosal challenge with a chimeric human/simian immunodeficiency virus. However, it is unknown whether nAb titers define protection in the setting of active immunization. Here we determined serum nAb titers against breakthrough transmitted/founder (T/F) SIVsmE660-derived envelope glycoprotein (Env) variants from 14 RMs immunized with SIVmac239-based DNA-prime/modified vaccinia virus Ankara-boost vaccine regimens that included GM-CSF or CD40L adjuvants and conferred significant but incomplete protection against repeated low-dose intrarectal challenge. A single Env variant established infection in all RMs except one, with no identifiable genetic signature associated with vaccination breakthrough compared with T/F Envs from four unvaccinated monkeys. Breakthrough T/F Env pseudoviruses were potently neutralized in vitro by heterologous pooled serum from chronically SIVsmE660-infected monkeys at IC50 titers exceeding 1:1,000,000. Remarkably, the T/F Env pseudoviruses from 13 of 14 monkeys were also susceptible to neutralization by autologous prechallenge serum at in vitro IC50 titers ranging from 1:742–1:10,832. These titers were similar to those observed in vaccinated RMs that remained uninfected. These data suggest that the relationship between serum nAb titers and protection from mucosal SIV challenge in the setting of active immunization is more complex than previously recognized, warranting further studies into the balance between immune activation, target cell availability, and protective antibody responses.

Download Full-text

Structures of Two Human Astrovirus Capsid/Neutralizing Antibody Complexes Reveal Distinct Epitopes and Inhibition of Virus Attachment to Cells

Journal of Virology ◽

10.1128/jvi.01415-21 ◽

2021 ◽

Author(s):

Lena Ricemeyer ◽

Nayeli Aguilar-Hernández ◽

Tomás López ◽

Rafaela Espinosa ◽

Sarah Lanning ◽

...

Keyword(s):

Receptor Binding ◽

Neutralizing Antibodies ◽

Severe Disease ◽

Neutralizing Antibody ◽

Host Cells ◽

Viral Gastroenteritis ◽

Receptor Binding Site ◽

Virus Attachment ◽

Human Astroviruses ◽

Human Astrovirus

Human astrovirus is an important cause of viral gastroenteritis worldwide. Young children, the elderly, and the immunocompromised are especially at risk for contracting severe disease. However, no vaccines exist to combat human astrovirus infection. Evidence points to the importance of antibodies in enabling protection of healthy adults from reinfection. To develop an effective subunit vaccine that broadly protects against diverse astrovirus serotypes, we must understand how neutralizing antibodies target the capsid surface at the molecular level. Here, we report the structures of the human astrovirus capsid spike domain bound to two neutralizing monoclonal antibodies. These antibodies bind two distinct conformational epitopes on the spike surface. We add to existing evidence that the human astrovirus capsid spike contains a receptor-binding domain and demonstrate that both antibodies neutralize human astrovirus by blocking virus attachment to host cells. We identify patches of conserved amino acids that overlap or border the antibody epitopes and may constitute a receptor-binding site. Our findings provide a basis to develop therapies that prevent and treat human astrovirus gastroenteritis. Importance Human astroviruses infect nearly every person in the world during childhood and cause diarrhea, vomiting, and fever. Despite the prevalence of this virus, little is known about how antibodies block virus infection. Here, we determined crystal structures of the astrovirus capsid protein in complex with two virus-neutralizing antibodies. We show that the antibodies bind two distinct sites on the capsid spike domain; however, both antibodies block virus attachment to human cells. Importantly, our findings support the use of the human astrovirus capsid spike as an antigen in a subunit-based vaccine to prevent astrovirus disease.

Download Full-text

Comparison of the pathogenicity and virus shedding of SARS CoV-2 VOC 202012/01 and D614G variant in hamster model

10.1101/2021.02.25.432136 ◽

2021 ◽

Author(s):

Sreelekshmy Mohandas ◽

Pragya D Yadav ◽

Dimpal Nyayanit ◽

Gururaj Deshpande ◽

Anita Shete-Aich ◽

...

Keyword(s):

Weight Loss ◽

Body Weight ◽

Respiratory Tract ◽

Neutralizing Antibodies ◽

Body Weight Loss ◽

Lung Pathology ◽

Upper Respiratory Tract ◽

Hamster Model ◽

Virus Shedding ◽

Vaccination Programs

AbstractThe emergence of SARS-CoV-2 variants has posed a serious challenge to public health system and vaccination programs across the globe. We have studied the pathogenicity and virus shedding pattern of the SARS-CoV-2 VOC 202012/01 and compared with D614G variant in Syrian hamsters. VOC 202012/01 could produce disease in hamsters characterized by body weight loss and respiratory tract tropism but mild lung pathology. Further, we also documented that neutralizing antibodies developed against VOC 202012/01 could equally neutralize D614G variant. Higher load of VOC 202012/01 in the nasal wash specimens was observed during the first week of infection outcompeting the D614G variant. The findings suggest increased fitness of VOC 202012/01 to the upper respiratory tract which could lead to higher transmission. Further investigations are needed to understand the transmissibility of new variants.One-Sentence SummarySARS-CoV-2 VOC 202012/01 infected hamsters demonstrated high viral RNA shedding through the nasal secretions and significant body weight loss with mild lung pathology compared to the D614G variant.

Download Full-text

The Anamnestic Neutralizing Antibody Response Is Critical for Protection of Mice from Challenge following Vaccination with a Plasmid Encoding the Japanese Encephalitis Virus Premembrane and Envelope Genes

Journal of Virology ◽

10.1128/jvi.73.7.5527-5534.1999 ◽

1999 ◽

Vol 73 (7) ◽

pp. 5527-5534 ◽

Cited By ~ 84

Author(s):

Eiji Konishi ◽

Masaoki Yamaoka ◽

Khin-Sane-Win ◽

Ichiro Kurane ◽

Kazuo Takada ◽

...

Keyword(s):

Japanese Encephalitis ◽

Neutralizing Antibodies ◽

Cytotoxic T Lymphocyte ◽

Neutralizing Antibody ◽

Immunoglobulin M ◽

Antibody Activity ◽

Lethal Challenge ◽

Challenge Virus ◽

Coding Regions

ABSTRACT For Japanese encephalitis (JE), we previously reported that recombinant vaccine-induced protection from disease does not prevent challenge virus replication in mice. Moreover, DNA vaccines for JE can provide protection from high challenge doses in the absence of detectable prechallenge neutralizing antibodies. In the present study, we evaluated the role of postchallenge immune responses in determining the outcome of JE virus infection, using mice immunized with a plasmid, pcDNA3JEME, encoding the JE virus premembrane (prM) and envelope (E) coding regions. In the first experiment, 10 mice were vaccinated once (five animals) or twice (remainder) with 100 μg of pcDNA3JEME. All of these mice showed low (6 of 10) or undetectable (4 of 10) levels of neutralizing antibodies. Interestingly, eight of these animals showed a rapid rise in neutralizing antibody following challenge with 10,000 50% lethal doses of JE virus and survived for 21 days, whereas only one of the two remaining animals survived. No unimmunized animals exhibited a rise of neutralizing antibody or survived challenge. Levels of JE virus-specific immunoglobulin M class antibodies were elevated following challenge in half of the unimmunized mice and in the single pcDNA3JEME-immunized mouse that died. In the second experiment, JE virus-specific primary cytotoxic T-lymphocyte (CTL) activity was detected in BALB/c mice immunized once with 100 μg of pcDNA3JEME 4 days after challenge, indicating a strong postchallenge recall of CTLs. In the third experiment, evaluation of induction of CTLs and antibody activity by plasmids containing portions of the prM/E cassette demonstrated that induction of CTL responses alone were not sufficient to prevent death. Finally, we showed that antibody obtained from pcDNA3JEME-immunized mice 4 days following challenge could partially protect recipient mice from lethal challenge. Taken together, these results indicate that neutralizing antibody produced following challenge provides the critical protective component in pcDNA3JEME-vaccinated mice.

Download Full-text

Specific Antibodies Induced by Immunization with Hepatitis B Virus-Like Particles Carrying Hepatitis C Virus Envelope Glycoprotein 2 Epitopes Show Differential Neutralization Efficiency

Vaccines ◽

10.3390/vaccines8020294 ◽

2020 ◽

Vol 8 (2) ◽

pp. 294

Author(s):

Anna Czarnota ◽

Anna Offersgaard ◽

Anne Finne Pihl ◽

Jannick Prentoe ◽

Jens Bukh ◽

...

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Neutralizing Antibodies ◽

Expression System ◽

Small Surface ◽

Major Health Problem ◽

Virus Like Particles ◽

B Virus

Hepatitis C virus (HCV) infection with associated chronic liver diseases is a major health problem worldwide. Here, we designed hepatitis B virus (HBV) small surface antigen (sHBsAg) virus-like particles (VLPs) presenting different epitopes derived from the HCV E2 glycoprotein (residues 412–425, 434–446, 502–520, and 523–535 of isolate H77C). Epitopes were selected based on their amino acid sequence conservation and were previously reported as targets of HCV neutralizing antibodies. Chimeric VLPs obtained in the Leishmania tarentolae expression system, in combination with the adjuvant Addavax, were used to immunize mice. Although all VLPs induced strong humoral responses, only antibodies directed against HCV 412–425 and 523–535 epitopes were able to react with the native E1E2 glycoprotein complexes of different HCV genotypes in ELISA. Neutralization assays against genotype 1–6 cell culture infectious HCV (HCVcc), revealed that only VLPs carrying the 412–425 epitope induced efficient HCV cross-neutralizing antibodies, but with isolate specific variations in efficacy that could not necessarily be explained by differences in epitope sequences. In contrast, antibodies targeting 434–446, 502–520, and 523–535 epitopes were not neutralizing HCVcc, highlighting the importance of conformational antibodies for efficient virus neutralization. Thus, 412–425 remains the most promising linear E2 epitope for further bivalent, rationally designed vaccine research.

Download Full-text