According to the landscape documents of COVID-19 candidate vaccines prepared by the World Health Organization, there are 44 candidate vaccines in clinical trials globally, 10 of which are in Phase III (Table 1). Additionally, we have 154 candidate vaccines in the preclinical stage worldwide.

Table 1 Ten candidate vaccines in Phase III clinical trial

Source: https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines.

A typical development cycle for a vaccine is about 10 to 15 years. Given this COVID-19 public health emergency, scientists are working very hard to reduce the development cycle to a year or two. Due to the rush of vaccine development and the insufficient understanding of the vaccine's immune responses, extra caution could be used when evaluating the safety and efficacy of the vaccine. Two major studies of the COVID-19 vaccine from AstraZeneca and Johnson& Johnson, both paused because of potential safety concerns earlier. However, announced last Friday, both trials are set to restart.

Currently, clinical trials are being conducted according to the rigorous standards set forth by FDA in their June 2020 guidance document, Development and Licensure of Vaccines to Prevent COVID-19. If a vaccine meets its safety and effectiveness standards, it will be approved for use or authorized for emergency use. Continued vaccine safety monitoring after approval/ authorization can pick up on adverse events that may not have been seen in clinical trials. If an unexpected adverse event is seen, experts quickly study it further to assess whether it is a true safety concern. Experts then decide whether changes are needed in U.S. vaccine recommendations. This monitoring is critical to help ensure that the benefits continue to outweigh the risks for people who receive vaccines. ^[1]

There is still a long way to go for COVID-19 vaccine development and testing. ACROBiosytems, specialized in recombinant protein, developed a series of COVID-19-related protein products, including S trimer protein and the titer measurement kits to support vaccine development.

Application 1: Vaccine immunogenicity evaluation ----- IgG antibody measurement

Recommended product 1: SARS-CoV-2 S protein, His Tag, Super stable trimer (MALS & NS-EM verified) 

Catalog Number: SPN-C52H9

Fig. 1 ACRO SARS-CoV-2 S protein was verified through SDS-PAGE, SEC-MALS, and negative staining electron microscopy. Our S trimer protein has over 90% purity with an MW of 550-660 kDa. According to the data of negative staining electron microscopy, the S trimer protein has a similar size and appearance compared to references.

Protocol

Fig. 2 The binding affinity of SARS-CoV-2 S trimer (Cat. No.SPN-C52H9) and human ACE2 (Cat. No. AC2-H5257) was evaluated using Biacore. The KD was 5.82nM.

Protocol

Fig. 3 Antibody measurement in recovered patient samples using SARS-CoV-2 S trimer (Cat. No.SPN-C52H9) with a very good signal-noise ratio.

Protocol

Recommended product 2: Anti-SARS-CoV-2 Antibody IgG Titer Serologic Assay kit (S protein trimer)

Catalog Number: TAS-K007

A rapid and effective assay kit for IgG antibody quantification in serum/plasma samples. This established method has advantages, including low background and a good signal to noise ratio.

Fig. 4 Immobilized SARS-CoV-2 S protein at 2 μg/mL (100 μL/well) can bind Monoclonal Anti-SARS-CoV-2 Antibody, Human IgG1 in 1:50 human serum. Detection was performed using the HRP-Conjugated Anti-human IgG antibody with a sensitivity of 12ng/mL.

Protocol

Recommended product 3: Anti-SARS-CoV-2 Antibody IgG Titer Serologic Assay kit (Spike protein RBD) 

Catalog Number: TAS-K002

A rapid and effective assay kit for IgG antibody quantification in serum/plasma samples. This established method has advantages, including low background and a good signal to noise ratio.

Fig. 5 Immobilized SARS-CoV-2 S protein RBD at 2 μg/mL (100 μL/well) can bind Monoclonal Anti-SARS-CoV-2 Antibody, Human IgG1 in 1:50 human serum. Detection was performed using the HRP-Conjugated Anti-human IgG antibody with a sensitivity of 24 ng/mL.

Protocol

Application 2: Vaccine clinical immunogenicity evaluation ----- Neutralizing antibody measurement

Recommended product 1: Anti-SARS-CoV-2 Neutralizing Antibody Titer Serologic Assay kit

Catalog Number: TAS-K003

This kit is intended for serologic measurement for the titer of Anti-SARS-CoV-2 neutralizing antibody in serum/plasma samples.

Fig. 6 Neutralizing titer of Anti-SARS-CoV-2 Neutralizing Antibody, Human IgG1 (Cat.No.SAD-S35) measured by Anti-SARS-CoV-2 neutralizing antibody titer serologic assay kit (Cat. No. TAS-K003).

Protocol

Recommended product 2: Anti-SARS-CoV-2 RBD Potent Neutralizing Antibody, Chimeric mAb, Human IgG1 (AM128)

Catalog Number: SPD-M128

This neutralizing antibody was verified using a pseudotyped virus. It is designed as a standard reference for the vaccine evaluation assays.

Fig. 7 Serial dilutions of Anti-SARS-CoV-2 RBD Potent Neutralizing Antibody, Chimeric mAb, Human IgG1 (AM128) (Cat. No. SPD-M128) was detected by SARS-CoV-2 Inhibitor screening Kit (Cat. No. EP-105) with a half maximal inhibitory concentration (IC50) of 1.197 μg/mL.

Protocol

Application 3: Vaccine post-market evaluation ----- Neutralizing antibody measurement

Recommended products:

Fig. 8 Lateral Flow Assay with spike-in neutralizing antibody serum samples (Cat No. SPD-M128). The anti-mouse IgG and RBD-his protein were coated to the control line and test line respectively. Colloidal gold labeled ACE2 and mouse IgG were immobilized in conjugate release pad.

Protocol

Additionally, ACRO developed an antibody isotyping kit, which can be used for anti-SARS-CoV-2 IgG1, IgG2, IgG3 and IgG4 testing. There will be more validated kits available for COVID-19 studies.

Reference:

1. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html