Introduction: Kidney transplant recipients (KTx) are a high-risk population for unfavorable outcomes when infected with SARS-COV2. Lethality in KTx can reach 25-30%. The immunosuppressants lead to a lower immunological response to infection due to both innate and adaptive immunity dysfunction. For this reason, KTx are considered priority group for vaccination (Vac).
Objective: To evaluate the vaccine response against SARS-COV2 in KTx and a healthy control group. Methods: Prospective and observational study. We used a Luminex-based multiplex assay was validated with simultaneous antibodies (Ab) screening that determines the presence of IgG Ab to five SARS-COV2 viral proteins, specifically: full spike protein (FSP), spike protein (S1, receptor binding domain [RBP]) and the nucleocapsid protein10 (NCP10). The analysis of serum and plasma samples was done according to the manufacturer’s instructions. The results are expressed in mean fluorescence intensity (MFI). Patients were classified as positive or negative according to automatic calculation of the FUSION program. Statistical analysis was done using Tukey test HSD.
Results: Sixty vaccinated Ktx were included from Aug/21 to Apr/22. Median age was 58 years, 32 (53%) males, 44 (73%) received a deceased donor transplant, and the median time between Tx and vaccination was 7,5 years. Samples were collected at least 30 days after the 1st, 2nd and 3rd Vac. Thirty-two were health professionals, control group (CG) median age 47 years, 18 (56%) females. The analysis was performed after the first and second Vac. The patients and CG received the vaccines available at the time.  In the KTx there was a significant increase in the humoral response in FSP after the second dose (x̄ 29769±18878) and third (x̄ 38108±15067) doses compared to the first (x̄ 18520±17032) dose (1x2 dose p = 0.004) (1x3 dose p < 0.0001), but with no difference between the 2nd and 3rd dose in the KTx group (2x3 p= 0.47). The same was observed in S1, 1st dose (x̄ 9914±10983), 2nd dose (x̄ 14108 ±2715) and 3rd dose (x̄ 27626±12858) 1x2 P=0.004, 1x3 p<0.0001 and 2X3 p=0.21. In the RDB (1st x̄ 11698±13498), 2nd (x̄ 22943,37±16547), 3rd (x̄ 31845±14939) the formation of antibodies even after the 3rd dose did not show significant increase (1x3) p=0.31. KTx compared to the CG (after 2nd dose- (x̄ 55812±179261)) the response was significantly lower than CG (1xCG2 p<0.0001). The Ab against NCP10 had a lower MFI in both groups. NCP10 analysis are 1 (x̄ 2593±4056), 2 (x̄ 4384±6873), 3 (x̄ 7097±12065), CG1 (x̄ 2226±3607) and CG2 (x̄ 3131±5657).
Conclusion: we found that a 3rd dose of SARS-CoV-2 vaccination in KTRs was associated with an increased antiviral Ab response against FSP and S1 protein of SARS-CoV-2. Although the neutralizing (RDB) responses remained markedly low. The NCP10 MFI was negative in both groups, reflecting a low infection rate.