Search

Neutralizing antibody (nAb) responses are attenuated in solid organ transplant recipients (SOTRs) despite severe acute respiratory syndrome-coronavirus-2 vaccination. Preexposure prophylaxis (PrEP) with the antibody combination tixagevimab and cilgavimab (T+C) might augment immunoprotection, yet in vitro activity and durability against Omicron sublineages BA.4/5 in fully vaccinated SOTRs have not been delineated. Vaccinated SOTRs, who received 300 + 300 mg T+C (ie, full dose), within a prospective observational cohort submitted pre and postinjection samples between January 31, 2022, and July 6, 2022. The peak live virus nAb was measured against Omicron sublineages (BA.1, BA.2, BA.2.12.1, and BA.4), and surrogate neutralization (percent inhibition of angiotensin-converting enzyme 2 receptor binding to full length spike, validated vs live virus) was measured out to 3 months against sublineages, including BA.4/5. With live virus testing, the proportion of SOTRs with any nAb increased against BA.2 (47%-100%; P < .01), BA.2.12.1 (27%-80%; P < .01), and BA.4 (27%-93%; P < .01), but not against BA.1 (40%-33%; P = .6). The proportion of SOTRs with surrogate neutralizing inhibition against BA.5, however, fell to 15% by 3 months. Two participants developed mild severe acute respiratory syndrome-coronavirus-2 infection during follow-up. The majority of fully vaccinated SOTRs receiving T+C PrEP achieved BA.4/5 neutralization, yet nAb activity commonly waned by 3 months postinjection. It is critical to assess the optimal dose and interval of T+C PrEP to maximize protection in a changing variant climate., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Neutralizing antibody responses are attenuated in many solid organ transplant recipients (SOTRs) despite SARS-CoV-2 vaccination. Pre-exposure prophylaxis (PrEP) with the monoclonal antibody combination Tixagevimab and Cilgavimab (T+C) might augment immunoprotection, yet activity against Omicron sublineages in vaccinated SOTRs is unknown. Vaccinated SOTRs who received 300+300mg T+C (either single dose or two 150+150mg doses) within a prospective observational cohort submitted pre- and post-injection samples between 1/10/2022-4/4/2022. Binding antibody (anti-receptor binding domain [RBD], Roche) and surrogate neutralization (%ACE2 inhibition; ≥20% connoting neutralizing inhibition, Meso Scale Discovery) were measured against variants including Omicron sublineages BA.1 and BA.2. Data were analyzed using the Wilcoxon matched-pairs signed-rank test and McNemar's test. Among 61 participants, median (IQR) anti-RBD increased from 424 (IQR <0.8-2322.5) to 3394.5 (IQR 1403.9-7002.5) U/ml post T+C (p<0.001). The proportion demonstrating vaccine strain neutralizing inhibition increased from 46% to 100% post-T+C (p<0.001). BA.1 neutralization was low and did not increase (8% to 16% of participants post-T+C, p=0.06). In contrast, BA.2 neutralization increased from 7% to 72% of participants post-T+C (p<0.001). T+C increased anti-RBD levels, yet BA.1 neutralizing activity was minimal. Encouragingly, BA.2 neutralization was augmented and in the current variant climate T+C PrEP may serve as a useful complement to vaccination in high-risk SOTRs.