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Study examines immunosuppressants and effectiveness of COVID vaccine

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which is the virus responsible for coronavirus disease 2019 (COVID-19), is easily transmitted between humans. Recent estimates indicate that COVID-19 has a death rate in symptomatic individuals of 2-8%.

To study: Modulation of immunosuppressive drug therapy to improve efficacy of SARS-CoV-2 vaccine in mice. Image Credit: Billion Photos /

Current COVID-19 vaccines

All coronaviruses share four common structural proteins, which include spike (S), envelope (E), core (N), and membrane (M) proteins. The S protein is made up of S1 and S2 subunits. The S1 subunit is where the receptor binding domain (RBD) is located, which binds to the angiotensin converting enzyme 2 (ACE2) receptor on the surface of host cells to allow the viral entry.

The S protein is a target for most of the current SARS-CoV-2 vaccines that have been approved by the World Health Organization (WHO). Serious illnesses are prevented by these vaccines due to the induction of robust antibody and T cell responses. SARS-CoV-2 vaccines have been shown to have weaker responses in people with autoimmune diseases. -immunes, potentially due to vaccine inhibition by immunosuppressive drugs.

In a recent study published on the Preprint Server bioRxiv*, researchers are studying the effects of five established immunosuppressive drugs that target different pathways of the immune response. In addition, the researchers wanted to determine whether the effects of these drugs could be regulated following changes in immunosuppressive regimens in mouse models. The authors then evaluated the immune response to vaccinations against the SARS-CoV-2 S protein in mice that had received immunosuppressive drugs.

Does immune suppression alter antibody responses to SARS-CoV-2 S protein?

Six groups of mice were selected, with five of the groups receiving immunosuppressive drugs and one control group receiving no drugs, to test the effect of these drugs on the efficacy of the SARS-CoV-2 vaccination. Compared to the control groups, all drug treatment groups showed significant decreases in absorbances.

After analysis of individual serum immunoglobulin G (IgG) and IgM levels, significant differences were observed between groups, indicating that immunosuppressive drugs may alter antibody responses to SARS-CoV-2 S protein vaccines. To determine whether inhibition of IgG and IgM titers against S protein would result in functional deficiencies of the anti-S response, the authors used a recombinant vesicular stomatitis virus (VSV), with the VSV glycoprotein replaced. by the SARS-CoV-2 S protein to monitor virus neutralization.

Comparing the 50% neutralization activity 28 days after primary vaccination, sera from mice treated with the drug were less potent than those from the control group. This difference was not observed in mice given leflunomide, which showed no significant difference compared to the control group.

The authors observed functional inhibition of antibody-mediated clearance of S protein-expressing cells in all drug-treated mice. Thus, this discovery revealed that immunosuppressive drugs can inhibit vaccine responses against SARS-CoV-2.

Changes in antibody levels against the SARS-CoV-2 spike protein after administration of immunosuppressants. A. Schematic of intraperitoneal immunization of SARS-CoV-2 spike protein and administration of immunosuppressive drugs. The recombinant peak protein was injected at 0.5 μg / 50 μl of alum per mouse. Alum-only mice received 50 µl of alum without spike protein. Immunosuppressants were administered intraperitoneally at the times indicated according to the concentrations in Supplementary Table 1. B. Serum was obtained from mice treated with immunosuppressant on days 14 (before booster immunization), 17, 21, 28 and 35 (after booster immunization). ELISA was performed to determine serum IgG titers against the spike protein. We did not detect an IgG / IgM response to the spike protein in sera from unimmunized mice (alum only). Entry was individual OD values ​​(405 nm) of sera at a dilution of 1/3200 and significance was determined for all time points after booster immunization. VS. IgG and D. IgM titers after booster immunizations (day 21) and at endpoint (day 35). The means of the OD values ​​at 405 nm absorbance from the technical replicates for an individual mouse serum sample were used in the regression curves to obtain titers (reciprocal serum dilutions) at an absorbance of 0.5 at 405 nm. Significance was determined relative to the drug-free control group. The alum only and CYC groups were non-detectable (ND).

Can temporary suspension of immunosuppressive drugs restore the function of antibodies against SARS-CoV-2?

To determine whether suspending the immunosuppressive regimen would improve the antibody response, the authors treated mice with cyclophosphamide (CYC), methotrexate (MTX), and methylprednisolone (MP), then stopped treatment at the time of vaccination. . The CYC-treated group of mice exhibited negligible levels of IgG and IgM titers against S protein despite discontinuation of treatment one and three days prior to vaccination.

Mice that received MP displayed some restoration of the antibody response when treatment was suspended prior to vaccination. Comparatively, the group that received MTX treatment showed significant increases in booster titer levels when treatment was discontinued. Depending on the drug in question, these results indicate that the antibody response to the SARS-CoV-2 S protein can be enhanced by modulating the immunosuppression regimen.

Changes in antibody titers against SARS-CoV-2 spike protein after continuous or temporarily suspended administration of immunosuppressants. A. Schematic of intraperitoneal immunization of SARS-CoV-2 spike protein and administration of immunosuppressants. The peak protein was injected at 0.5 µg / 50 µl alum per mouse. The immunosuppressants were administered intraperitoneally at the times indicated according to the concentrations in Supplementary Table 2. In each group of immunosuppressants, 4 mice did not receive the respective immunosuppressant on days 0 and 14, and 4 mice did not. not received immunosuppressants on days – 2, 0, 2, 12, 14 and 16. Comics. Serum was obtained from mice treated with an immunosuppressant on days 14, 17, 21, 28 and 35. ELISA was performed to determine serum IgG against the spike protein. Multiple serial serum dilutions were performed, with the sample set of each dilution (including all time points) on a 384-well plate. The entry was individual OD values ​​at an absorbance of 405 nm. ELISA data using 1: 3200 serum dilutions of 4 mice / group (upper panels) and calculated booster titers (day 21) are presented based on serial dilution regression curves (lower panels). Statistical values ​​were determined relative to continuous drug therapy (A. CYC; B. MTX; C. MP).


Current guidelines from the American College of Rheumatology suggest suspending certain immunosuppressive treatments before COVID-19 vaccination, which is validated by the results of this study.

The current COVID-19 pandemic has highlighted the definite need for consistent and progressive research on immunosuppressive therapies and vaccinations. The authors demonstrated in a practical study that careful monitoring of immunosuppressive drugs at the time of vaccination can improve the vaccine response against SARS-CoV-2.

*Important Notice

bioRxiv publishes preliminary scientific reports that are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.

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