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

Abstract

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.

Sequential Analysis of Binding and Neutralizing Antibody in COVID-19 Convalescent Patients at 14 Months After SARS-CoV-2 Infection

“…Recent emerging Variants of Concern show a multitude of such changes which will likely affect NAb function of the WA1-induced antibodies. We and others reported that WA1 antibody showed lower binding to Delta both in humans (29,(33)(34)(35)(36)(37)(38) and vaccinated macaques (32).…”

“…Differences between slopes from consecutive intervals were also tested with the signed rank test. The fit model to deterrmine both the antibody endpoint titers and 50% titers of the neutralization curves were previously described (32) and were determinated using R methods-package (https://www.rdocumentation.org/packages/ stats/versions/3.6.2/topics/nls) (1). Analysis was performed by using GraphPad Prism Version 9.2 for MacOS X (GraphPad Software, Inc, La Jolla, CA).…”

“…The antibodies are maintained for over 14 months post symptom onset with a ranking of Alpha>Delta>Mu>Beta. Binding antibody strength is predictive of its neutralization capability (29,32), supported by stronger NAb against Delta compared to Beta. We also found that the neutralization capability of SARS-CoV-2 infection-induced antibodies against the Delta variant is better than the BNT162b2 mRNA vaccine induced responses (29).…”

“…Briefly, serial dilutions (4x fold serial dilutions starting at 1:10) of heatinactivated sera were incubated with an equal volume of the pseudotyped virions (pHIV NL Env-Nanoluc (30,31) and the virion-Ab mixture was used to transduce HEK293T/ACE2wt cells. The reporter virus was pseudotyped with the Spike spanning 1254 amino acids from WA1, Alpha, Beta and Delta (32). The highest serum concentration analyzed was a 1:40 dilution (a four-fold serial dilution up to 1:655,360).…”

Reduced Antibodies and Innate Cytokine Changes in SARS-CoV-2 BNT162b2 mRNA Vaccinated Transplant Patients With Hematological Malignancies

“…In-house ELISA assays using a panel of purified trimeric complete Wuhan strain (WA1) Spike and Spike-RBD and a panel of VOC Spike-RBD proteins (Beta B.1.351, Delta B.1.617.2, Omicron B.1.1.529) were detailed elsewhere ( 26 – 28 ). Ab levels were measured using eight 4-fold serial serum dilutions starting at 1:50 and endpoint titers were determined using lastX feature using GraphPad prism area-under-the curve program.…”