Comparison of Wild Type DNA Sequence of Spike Protein from SARS-CoV-2 with Optimized Sequence on The Induction of Protective Responses Against SARS-Cov-2 Challenge in Mouse Model

COVID-19 caused by SARS-CoV-2 has been spreading worldwide. To date, several vaccine candidates moved into EUA or CA applications. Although DNA vaccine is on phase III clinical trial, it is a promised technology platform with many advantages. Here, we showed that the pGX9501 DNA vaccine encoded the spike full-length protein-induced strong humoral and cellular immune responses in mice with higher neutralizing antibodies, blocking the hACE2-RBD binding against live virus infection in vitro. Importantly, higher levels of IFN-γ expression in CD8+ and CD4+ T cell and specific cytotoxic lymphocyte (CTL) killings effect were also observed in the pGX9501-immunized group. It provided subsequent protection against virus challenges in the hACE2 transgenic mouse model. Overall, pGX9501 was a promising DNA vaccine candidate against COVID-19, inducing strong humoral immunity and cellular immunity that contributed to the vaccine's protective effects.

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Cellular and Humoral Immunogenicity of a Candidate DNA Vaccine Expressing SARS-CoV-2 Spike Subunit 1

Vaccines ◽

10.3390/vaccines9080852 ◽

2021 ◽

Vol 9 (8) ◽

pp. 852

Author(s):

Khalid A. Alluhaybi ◽

Rahaf H. Alharbi ◽

Rowa Y. Alhabbab ◽

Najwa D. Aljehani ◽

Sawsan S. Alamri ◽

...

Keyword(s):

Immune Responses ◽

Dna Vaccine ◽

Neutralizing Antibodies ◽

Vaccine Development ◽

Cell Responses ◽

Cellular Immune Responses ◽

Specific Igg ◽

Cellular Immune ◽

Different Doses

The urgent need for effective, safe and equitably accessible vaccines to tackle the ongoing spread of COVID-19 led researchers to generate vaccine candidates targeting varieties of immunogens of SARS-CoV-2. Because of its crucial role in mediating binding and entry to host cell and its proven safety profile, the subunit 1 (S1) of the spike protein represents an attractive immunogen for vaccine development. Here, we developed and assessed the immunogenicity of a DNA vaccine encoding the SARS-CoV-2 S1. Following in vitro confirmation and characterization, the humoral and cellular immune responses of our vaccine candidate (pVAX-S1) was evaluated in BALB/c mice using two different doses, 25 µg and 50 µg. Our data showed high levels of SARS-CoV-2 specific IgG and neutralizing antibodies in mice immunized with three doses of pVAX-S1. Analysis of the induced IgG subclasses showed a Th1-polarized immune response, as demonstrated by the significant elevation of spike-specific IgG2a and IgG2b, compared to IgG1. Furthermore, we found that the immunization of mice with three doses of 50 µg of pVAX-S1 could elicit significant memory CD4+ and CD8+ T cell responses. Taken together, our data indicate that pVAX-S1 is immunogenic and safe in mice and is worthy of further preclinical and clinical evaluation.

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Cellular and humoral immunogenicity of a candidate DNA Vaccine Expressing SARS-CoV-2 Spike Subunit 1

10.20944/preprints202106.0650.v1 ◽

2021 ◽

Author(s):

Khalid A. Alluhaybi ◽

Rahaf H. Alharbi ◽

Rowa Y. Alhabbab ◽

Najwa D Aljehani ◽

Sawsan S. Alamri ◽

...

Keyword(s):

Immune Responses ◽

Dna Vaccine ◽

Neutralizing Antibodies ◽

Vaccine Development ◽

Cell Responses ◽

Cellular Immune Responses ◽

Specific Igg ◽

Cellular Immune ◽

Different Doses

The urgent need for effective, safe and equitably accessible vaccines to tackle the ongoing spread of COVID-19 led researchers to generate vaccine candidates targeting varieties of immunogens of SARS-CoV-2. Because of its crucial role in mediating binding and entry to host cell and its proven safety profile, the subunit 1 (S1) of the spike protein represents an attractive immunogen for vaccine development. Here, we developed and assessed the immunogenicity of a DNA vaccine encoding the SARS-CoV-2 S1. Following in vitro confirmation and characterization, the humoral and cellular immune responses of our vaccine candidate (pVAX-S1) was evaluated in BALB/c mice using two different doses, 25 µg and 50 µg. Our data showed high levels of SARS-CoV-2 specific IgG and neutralizing antibodies in mice immunized with three doses of pVAX-S1. Analysis of the induced IgG subclasses showed a Th1-polarized immune response as demonstrated by the significant elevation of spike-specific IgG2a and IgG2b compared to IgG1. Furthermore, we found that immunization of mice with three doses of 50 µg of pVAX-S1 could elicit significant memory CD4+ and CD8+ T cell responses. Taken together, our data indicates that pVAX-S1 is immunogenic and safe in mice and is worthy of further preclinical and clinical evaluation.

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Control of SARS-CoV-2 infection after Spike DNA or Spike DNA+Protein co-immunization in rhesus macaques

10.1101/2021.06.11.448032 ◽

2021 ◽

Author(s):

Margherita Rosati ◽

Mahesh Agarwal ◽

Xintao Hu ◽

Santhi Devasundaram ◽

Dimitris Stellas ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Protective Efficacy ◽

Rhesus Macaques ◽

Neutralizing Antibody ◽

Anatomical Site ◽

Cell Responses ◽

Cellular Immune Responses ◽

Antibody Titers ◽

Cellular Immune

The speed of development, versatility and efficacy of mRNA-based vaccines have been amply demonstrated in the case of SARS-CoV-2. DNA vaccines represent an important alternative since they induce both humoral and cellular immune responses in animal models and in human trials. We tested the immunogenicity and protective efficacy of DNA-based vaccine regimens expressing different prefusion-stabilized SARS-CoV-2 Spike antigens upon intramuscular injection followed by electroporation in rhesus macaques. Different Spike DNA vaccine regimens induced antibodies that potently neutralized SARS-CoV-2 in vitro and elicited robust T cell responses. The DNA-only vaccine regimens were compared to a regimen that included co-immunization of Spike DNA and protein in the same anatomical site, the latter of which showed significant higher antibody responses. All vaccine regimens led to control of SARS-CoV-2 intranasal/intratracheal challenge and absence of virus dissemination to the lower respiratory tract. Vaccine-induced binding and neutralizing antibody titers and antibody-dependent cellular phagocytosis inversely correlated with transient virus levels in the nasal mucosa. Importantly, the Spike DNA+Protein co-immunization regimen induced the highest binding and neutralizing antibodies and showed the strongest control against SARS-CoV-2 challenge in rhesus macaques.

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Immunization by exposure to live virus (SIVmne/HIV-2287) during antiretroviral drug prophylaxis reduces risk of subsequent viral challenge

10.1101/2020.09.30.320820 ◽

2020 ◽

Author(s):

LM Frenkel ◽

L Kuller ◽

IA Beck ◽

C-C Tsai ◽

JP Joy ◽

...

Keyword(s):

Immune Responses ◽

Neutralizing Antibodies ◽

Antiretroviral Drugs ◽

Macaca Nemestrina ◽

Live Virus ◽

Experimental Animals ◽

Cellular Immune Responses ◽

Antiretroviral Prophylaxis ◽

Homologous Virus ◽

Cellular Immune

AbstractRationale/Study DesignA major challenge in the development of HIV vaccines is finding immunogens that elicit protection against a broad range of viral strains. Immunity to a narrow range of viral strains may protect infants of HIV-infected women or partners discordant for HIV. We hypothesized that immunization to the relevant viral variants could be achieved by exposure to infectious virus during prophylaxis with antiretroviral drugs. To explore this approach in an animal model, macaques were exposed to live virus (SIVmne or HIV-2287) during prophylaxis with parenteral tenofovir. The humoral and cellular immune responses were quantified. Subsequently, experimental animals were challenged with homologous virus to evaluate protection from infection, and if infection occurred, the course of disease was compared to control animals. Experimental animals uninfected with SIVmne were challenged with heterologous HIV-2287 to assess resistance to retroviral infection.Methodology/Principal FindingsJuvenile Macaca nemestrina (N=8) were given ten weekly intravaginal exposures with either moderately (SIVmne) or highly (HIV-2287) pathogenic virus during tenofovir prophylaxis. Tenofovir protected all 8 experimental animals from infection, while all untreated control animals became infected. Specific non-neutralizing antibodies were elicited in blood and vaginal secretions of experimental animals, but no ELISPOT responses were detected. Six weeks following the cessation of tenofovir, intravaginal challenge with homologous virus infected 2/4 (50%) of the SIVmne-immunized animals and 4/4 (100%) of the HIV-2287-immunized animals. The two SIVmne-infected and 3 (75%) HIV-2287-infected had attenuated disease, suggesting partial protection.Conclusions/SignificanceRepeated exposure to SIVmne or HIV-2287 during antiretroviral prophylaxis blocked infection induced binding antibodies in the blood and mucosa, but not neutralizing antibodies or specific cellular immune responses. Studies to determine whether antibodies are similarly induced in breastfeeding infants and sexual partners discordant for HIV infection and receiving pre-exposure antiretroviral prophylaxis are warranted, including whether these antibodies appear to confer partial or complete protection from infection.

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Deciphering the Role of Humoral and Cellular Immune Responses in Different COVID-19 Vaccines—A Comparison of Vaccine Candidate Genes in Roborovski Dwarf Hamsters

Viruses ◽

10.3390/v13112290 ◽

2021 ◽

Vol 13 (11) ◽

pp. 2290

Author(s):

Jakob Trimpert ◽

Susanne Herwig ◽

Julia Stein ◽

Daria Vladimirova ◽

Julia M. Adler ◽

...

Keyword(s):

Immune Responses ◽

Nucleocapsid Protein ◽

Neutralizing Antibodies ◽

Specific Antigen ◽

T Cell Response ◽

Full Length ◽

Spike Protein ◽

Protective Effects ◽

Cellular Immune Responses ◽

Cellular Immune

With the exception of inactivated vaccines, all SARS-CoV-2 vaccines currently used for clinical application focus on the spike envelope glycoprotein as a virus-specific antigen. Compared to other SARS-CoV-2 genes, mutations in the spike protein gene are more rapidly selected and spread within the population, which carries the risk of impairing the efficacy of spike-based vaccines. It is unclear to what extent the loss of neutralizing antibody epitopes can be compensated by cellular immune responses, and whether the use of other SARS-CoV-2 antigens might cause a more diverse immune response and better long-term protection, particularly in light of the continued evolution towards new SARS-CoV-2 variants. To address this question, we explored immunogenicity and protective effects of adenoviral vectors encoding either the full-length spike protein (S), the nucleocapsid protein (N), the receptor binding domain (RBD) or a hybrid construct of RBD and the membrane protein (M) in a highly susceptible COVID-19 hamster model. All adenoviral vaccines provided life-saving protection against SARS-CoV-2-infection. The most efficient protection was achieved after exposure to full-length spike. However, the nucleocapsid protein, which triggered a robust T-cell response but did not facilitate the formation of neutralizing antibodies, controlled early virus replication efficiently and prevented severe pneumonia. Although the full-length spike protein is an excellent target for vaccines, it does not appear to be the only option for future vaccine design.

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SARS-COV-2 Recombinant Receptor-Binding-Domain (RBD) Induces Neutralising Antibodies Against Variant Strains of SARS-CoV-2 and SARS-CoV-1

10.1101/2021.05.10.443438 ◽

2021 ◽

Author(s):

John Lok Man Law ◽

Michael Logan ◽

Michael Joyce ◽

Abdolamir Landi ◽

Darren Hockman ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Protective Immunity ◽

Vaccine Antigen ◽

Neutralising Antibodies ◽

Cellular Immune Responses ◽

Recombinant Receptor ◽

Virion Envelope ◽

Human Use ◽

Cellular Immune

SARS-CoV-2 is the etiological agent of COVID19. There are currently several licensed vaccines approved for human use and most of them are targeting the spike protein (or virion) in the virion envelope to induce protective immunity. Recently, variants that spread more quickly have emerged. There is evidence that some of these variants are less sensitive to neutralization in vitro, but it is not clear whether they can evade vaccine induced protection. In this study, we tested the utility of SARS-CoV-2 spike RBD as a vaccine antigen and explore the effect of formulation with Alum/MPLA or AddaS03 adjuvants. Our results indicate RBD induces high titers of neutralizing antibodies and activates strong cellular immune responses. There is also significant cross-neutralisation of variants B1.1.7 and B.1.351 and to a lesser extent, SARS-CoV- 1. These results indicate that recombinant RBD can be a viable candidate as a stand-alone vaccine or as a booster shot to diversify our strategy for COVID19 protection.

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Immunization by exposure to live virus (SIVmne/HIV-2287) during antiretroviral drug prophylaxis may reduce risk of subsequent viral challenge

PLoS ONE ◽

10.1371/journal.pone.0240495 ◽

2021 ◽

Vol 16 (4) ◽

pp. e0240495

Author(s):

Lisa M. Frenkel ◽

LaRene Kuller ◽

Ingrid A. Beck ◽

Che-Chung Tsai ◽

Jaimy P. Joy ◽

...

Keyword(s):

Immune Responses ◽

Neutralizing Antibodies ◽

Antiretroviral Drugs ◽

Macaca Nemestrina ◽

Live Virus ◽

Experimental Animals ◽

Cellular Immune Responses ◽

Antiretroviral Prophylaxis ◽

Homologous Virus ◽

Cellular Immune

Rationale/Study design A major challenge in the development of HIV vaccines is finding immunogens that elicit protection against a broad range of viral strains. Immunity to a narrow range of viral strains may protect infants of HIV-infected women or partners discordant for HIV. We hypothesized that immunization to the relevant viral variants could be achieved by exposure to infectious virus during prophylaxis with antiretroviral drugs. To explore this approach in an animal model, macaques were exposed to live virus (SIVmne or HIV-2287) during prophylaxis with parenteral tenofovir and humoral and cellular immune responses were quantified. Subsequently, experimental animals were challenged with homologous virus to evaluate protection from infection, and if infection occurred, the course of disease was compared to control animals. Experimental animals uninfected with SIVmne were challenged with heterologous HIV-2287 to assess resistance to retroviral infection. Methodology/Principal findings Juvenile female Macaca nemestrina (N = 8) were given ten weekly intravaginal exposures with either moderately (SIVmne) or highly (HIV-2287) pathogenic virus during tenofovir prophylaxis. Tenofovir protected all 8 experimental animals from infection, while all untreated control animals became infected. Specific non-neutralizing antibodies were elicited in blood and vaginal secretions of experimental animals, but no ELISPOT responses were detected. Six weeks following the cessation of tenofovir, intravaginal challenge with homologous virus infected 2/4 (50%) of the SIVmne-immunized animals and 4/4 (100%) of the HIV-2287-immunized animals. The two SIVmne-infected and 3 (75%) HIV-2287-infected had attenuated disease, suggesting partial protection. Conclusions/Significance Repeated exposure to SIVmne or HIV-2287, during antiretroviral prophylaxis that blocked infection, induced binding antibodies in the blood and mucosa, but not neutralizing antibodies or specific cellular immune responses. Studies to determine whether antibodies are similarly induced in breastfeeding infants and sexual partners discordant for HIV infection and receiving pre-exposure antiretroviral prophylaxis are warranted, including whether these antibodies appear to confer partial or complete protection from infection.

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Control of SARS-CoV-2 infection after Spike DNA or Spike DNA+Protein co-immunization in rhesus macaques

PLoS Pathogens ◽

10.1371/journal.ppat.1009701 ◽

2021 ◽

Vol 17 (9) ◽

pp. e1009701

Author(s):

Margherita Rosati ◽

Mahesh Agarwal ◽

Xintao Hu ◽

Santhi Devasundaram ◽

Dimitris Stellas ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Protective Efficacy ◽

Rhesus Macaques ◽

Neutralizing Antibody ◽

Anatomical Site ◽

Cell Responses ◽

Cellular Immune Responses ◽

Antibody Titers ◽

Cellular Immune

The speed of development, versatility and efficacy of mRNA-based vaccines have been amply demonstrated in the case of SARS-CoV-2. DNA vaccines represent an important alternative since they induce both humoral and cellular immune responses in animal models and in human trials. We tested the immunogenicity and protective efficacy of DNA-based vaccine regimens expressing different prefusion-stabilized Wuhan-Hu-1 SARS-CoV-2 Spike antigens upon intramuscular injection followed by electroporation in rhesus macaques. Different Spike DNA vaccine regimens induced antibodies that potently neutralized SARS-CoV-2 in vitro and elicited robust T cell responses. The antibodies recognized and potently neutralized a panel of different Spike variants including Alpha, Delta, Epsilon, Eta and A.23.1, but to a lesser extent Beta and Gamma. The DNA-only vaccine regimens were compared to a regimen that included co-immunization of Spike DNA and protein in the same anatomical site, the latter of which showed significant higher antibody responses. All vaccine regimens led to control of SARS-CoV-2 intranasal/intratracheal challenge and absence of virus dissemination to the lower respiratory tract. Vaccine-induced binding and neutralizing antibody titers and antibody-dependent cellular phagocytosis inversely correlated with transient virus levels in the nasal mucosa. Importantly, the Spike DNA+Protein co-immunization regimen induced the highest binding and neutralizing antibodies and showed the strongest control against SARS-CoV-2 challenge in rhesus macaques.

Download Full-text