# Impact of maintenance immunosuppression regimen on anti-SARS-CoV-2 antibody and cellular kinetics in kidney transplant recipients receiving ChAdOx1 as primary vaccination

## TL;DR

This study compares how two immunosuppression drugs affect antibody and cellular responses to a SARS-CoV-2 vaccine in kidney transplant recipients.

## Contribution

The study reveals that Azathioprine provides early immune advantages over Mycophenolate Sodium, but both drugs lead to similar long-term immunity with booster doses.

## Key findings

- AZA showed higher baseline neutralizing activity compared to MPS, but both groups had comparable immunity by month 3.
- Booster doses significantly improved neutralizing activity in both groups over 12 months.
- Long-term humoral and cellular immunity were similar between the two immunosuppression regimens.

## Abstract

Kidney Transplant Recipients (KTRs) face increased COVID-19 risks due to immunosuppression, which may affect vaccine response. This study evaluates the impact of Mycophenolate Sodium (MPS) versus Azathioprine (AZA) on anti-SARS-CoV-2 humoral and cellular kinetics after ChAdOx1 vaccination.

In this prospective, observational study, 89 KTRs who seroconverted post-vaccination were grouped based on maintenance immunosuppression (MPS: n = 51; AZA: n = 38). Anti-SARS-CoV-2 IgG titers, neutralizing antibody activity, and cellular immunity assessed by the Interferon-Gamma (IFN-γ) release were measured at screening and 1-, 3-, 6-, and 12-months post-transplant. Linear regression and generalized estimating equations assessed group and time effects.

At baseline, IgG titers were 12,059.2 AU/mL (MPS) and 14,369.3 AU/mL (AZA), with both groups experiencing a decline at month 1 (9483.9 AU/mL and 11,023.5 AU/mL, respectively). By month 12, titers stabilized at 11,626.8 AU/mL (MPS) and 13,851.4 AU/mL (AZA; p = 0.286). Neutralizing activity was initially higher with AZA (0.924 vs. 0.764 at baseline; p = 0.006) but converged by month 3 (0.937 vs. 0.871; p = 0.161). Booster doses significantly enhanced neutralizing activity by 0.175 over 12 months. Positive cellular immunity was inferior in the MPS group at screening (4.2% vs. 15.8 %; p = 0.171) and M1 (13.3% vs. 27.8 %; p = 0.266), but similar in the following visits.

AZA provided a transient early advantage in immunity responses against SARS-CoV-2, but long-term humoral and cellular kinetics were comparable. Booster doses are essential for sustaining immunity in KTRs, emphasizing the need for tailored vaccination strategies. These findings may inform clinical decisions during pandemics.