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Purpose: Kidney transplant recipients taking belatacept (KTR-B) have poor immune response to two-dose SARS-CoV-2 vaccination. We sought to characterize the impact of an additional vaccine dose on plasma neutralizing capacity and cellular responses as compared to that of KTRs controls (KTR-C) not taking belatacept. Method(s): Within an observational cohort, we tested 26 KTR-Bs and 27 KTR-Cs for anti-spike antibody responses before and after a third SARS-CoV-2 vaccine dose (D3) using two clinical assays (Roche Elecsys anti-S Ig and EUROIMMUN anti-S1 IgG). For a subset of 5 KTR-Bs and for all KTR-Cs we used a research assay (Meso Scale Diagnostics V-Plex [MSD]) to further assess anti-spike and RBD IgG, as well as surrogate plasma neutralizing activity (% ACE2 inhibition) versus the ancestral and delta variants. For 3 KTR-Bs, post D3 T cell response was assessed via IFN-y ELISpot and deemed positive if spot forming units > 20 per million PBMC and stimulation index > 3. Result(s): KTR-Bs had significant lower clinical anti-spike seroconversion than KTR-Cs (31% vs 74%, p=0.001) after D3 despite similar demographics, clinical factors, and vaccines administered (Table 1). No KTR-B (0/5) was seropositive by MSD anti-spike or anti-RBD IgG (Figure 1). % ACE2 inhibition versus the ancestral variant was significantly lower in KTR-Bs than in KTR-Cs (Median [IQR] 5.2 [2.8, 6.5] vs 12.5 [7.7, 23.9], p<0.01);all KTR-Bs were below a level consistent with detectable neutralizing antibody. All tested KTR-Bs (3/3) had a negative ELISpot, consistent with negligible cellular response. Conclusion(s): These results suggest minimal humoral or cellular immunogenicity of additional vaccine doses for KTR-Bs and indicates the need for alternative strategies to improve vaccine response such as immunosuppression alteration or use of passive immunoprophylaxis with monoclonal anti-spike antibody to improve protection versus SARS-CoV-2.
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Purpose: The impact of antigenic imprinting, when immune memory of one antigen influences the response to subsequent similar antigens, on the antibody response in solid organ transplant recipients (SOTRs) after SARS-CoV-2 vaccination is currently unknown. This study examines the relationship between seasonal coronaviruses (sCoV) and SARS-CoV-2 antibody levels pre- and post-vaccination in SOTRs. Method(s): Plasma from 52 SOTRs pre- and post-SARS-CoV-2 vaccination (2 doses, mRNA) was analyzed using the Meso Scale Diagnostic Coronavirus Panel 3 (an electrochemiluminescence detection-based multiplexed sandwich immunoassay) for IgG antibodies against alpha sCoVs (229E, NL63), beta sCoVs (HKU1, OC43), and SARS-CoV-2 spike proteins. Changes in IgG titers were determined by paired Wilcoxon rank-sum tests. Spearman correlation analysis was used to determine associations between pre-vaccination anti-sCoVs and post-vaccination anti-SARS-CoV-2 IgG. Result(s): Vaccination increased both anti-SARS-CoV-2 (fold change (FC) 1.9, p<0.001) and anti-beta sCoV (HKU1 [FC 0.05, p<0.001], OC43 [FC 0.8, p<0.001]) IgG titers in SOTRs, but did not increase anti-alpha sCoV IgG. Furthermore, prevaccination anti-beta sCoV (HKU1 [rho= -0.3, p=0.03], OC43 [rho= -0.3, p<0.03]) IgG titers were negatively correlated with post-vaccination anti-SARS-CoV-2 IgG. Conclusion(s): These exploratory findings suggest that prior exposure to seasonal betacoronaviruses may lead to antigenic imprinting in SOTRs that negatively impacts the antibody response to vaccination against the novel pandemic betacoronavirus, SARS-CoV-2.
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Purpose: Humoral response to COVID-19 vaccines is attenuated in many solid organ transplant recipients (SOTRs), necessitating additional primary and booster vaccinations. The omicron variant demonstrates substantial immune evasion, and it is not known if boosters increase neutralizing capacity versus omicron among SOTRs. We therefore investigated SOTR antibody response and neutralization versus variants of concern (VOC) including omicron to a 4th vaccine dose (D4). Method(s): Within a national, prospective observational cohort, 25 SOTRs underwent anti-SARS-CoV-2 spike and receptor binding domain (RBD) IgG testing using the Meso Scale Discovery platform before and 2-4 weeks after D4. Surrogate neutralization (%ACE2 inhibition [%ACE2i], range 0-100% with >20% correlating with live virus neutralization), was measured versus full spike proteins of the ancestral ("vaccine") strain and 5 VOCs including delta and omicron. Change in IgG level and %ACE2i were compared using paired Wilcoxon rank-sum testing. Result(s): Demographics are outlined in Table 1, including median (IQR) age 59 (45- 55) years, 64% kidney recipients, and D4 receipt (60% Moderna, 40% Pfizer) median (IQR) 93 days (28-134) post D3. Two participants had SARS-CoV-2 exposure per anti-nucleocapsid testing, including one incident infection. Overall, anti-RBD (92%- >100%) and anti-spike (84%->92%) seropositivity increased after D4, as did median (IQR) anti-spike IgG 42.3 (4.9-134.2)->228.9 (115.4-655.8) WHO binding antibody units (p<0.05). Median (IQR) %ACE2i significantly increased after D4 vs the vaccine strain 5.8% (0-16.8)->20.6% (5.8-45.9) and delta variant 9.1% (4.9-12.8)->17.1% (10.3-31.7) (both p<0.001). In contrast, no SOTR showed neutralization vs omicron before or after D4: median (IQR) %ACE2i 4.1% (0-6.9)->0.5% (0-5.7) (p=0.11). Conclusion(s): Although a 4th vaccine dose increased anti-spike IgG and neutralizing capacity vs some VOC, there was no omicron variant neutralization among SOTRs. SOTRs may remain at high risk for SARS-CoV-2 infection despite boosting, thus additional protective interventions should be urgently explored. (Figure Presented).
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Purpose: Understanding the dynamics of antibody response to a third dose (D3) of anti-SARS-CoV-2 vaccine in solid organ transplant recipients (SOTRs) is important to inform booster strategies. Method(s): We studied the the dynamics of anti-RBD (Roche, <0.8 to >2500 U/dL) and anti-S (Euroimmun, 0.1 to >8.9 AU) antibody levels in a cohort of SOTRs at 2 weeks, 1 month and 3 months after D3. We compared the proportion of seroconversion at 1 month or 3 months after D3 between mRNA and Ad.26.COV2.S D3 recipients, using Poisson regression with robust standard error, adjusting for age and numbers of immunosuppressants. Result(s): Among 928 SOTRs with 2-week (n=655), 1-month (n=651) or 3-month (n=404) post-D3 titer, 78%, 82% and 86% tested positive for antibodies. The median (IQR) anti-RBD at the three timepoints were >2500 (73, >2500), 2494 (49, >2500) and 1234 (59, >2500) U/mL (Figure 1A, blue), and there were 61% (n=436), 60% (n=491) and 53% (n=313) with anti-RBD> 1000 u/mL, respectively. The median (IQR) anti-S at the three timepoints were 3.2 (0.3, 8.4), 8 (2, >8.9) and 7.4 (2, >8.9) AU (Figure 1B, blue), and there were 47% (n=218), 61% (n=161) and 64% (n=91) who developed anti-S>4 AU. Among patients with no or minimal immune response at 2 weeks post-D3 (n=102), 3/41 (7%) had increased anti-RBD by 1 month while 11/18 (61%) had increased anti-S (Fisher exact p<0.001). 6/29 (21%) had increased anti-RBD by 3 months while 12/20 (60%) had increased anti-S (p<0.01) (Figure 1A&B, yellow). 27/102 (27%) of them seroconverted at 1 or 3 months after D3. Having received Ad.26.COV2.S as D3 is associated with 3.9X increased proportion of seroconversion at 1 month or 3 months among patients with no or minimal immune response at 2 weeks after D3 (aIRR=2.223.926.92, p<0.001). Conclusion(s): Among SOTRs who received a booster anti-SARS-CoV-2 vaccination, dynamics of Anti-RBD and Anti-S antibodies differed substantially. Anti-RBD titers on average declined only slightly after 14 days post-D3, while anti-S increased up through 30-60 days post-D3. After the peak, average titer values for both antibodies declined slightly through three months post-D3.
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Purpose: Heart and lung transplant (HT/LT) recipients have impaired humoral responses to SARS-CoV-2 vaccination compared to other solid organ transplant recipients (SOTRs). The purpose of this study is to describe antibody titer kinetics and durability among HT and LT recipients. Method(s): HT or LT recipients (> 18 years) with no known COVID-19 infection were included. Demographics and clinical characteristics were collected via survey. Serologic testing was performed on the Roche Elecsys anti-SARS-CoV-2 enzyme immuno-assay (EIA) or the EUROIMMUN EIA pre- and post-dose 2 (D2). Result(s): Among 93 HT recipients, 59 (63%) were seropositive 1 month and 66 (71%) 3 months post-D2 (Table 1). Seropositive HT recipients had a higher median length of time from transplant to vaccination. 7/66 (11%) had delayed seroconversion (were negative for antibodies 1-month post-D2). Median(IQR) anti-RBD was 81 (8, 250) 1-month post-D2 (n=38) and 231 (48, 438) U/mL 3-months post-D2 (n=43) (Figure 1). Among 68 LT recipients, 29/68 (43%) were seropositive 1-month and 30 (44%) 3-months post-D2. Seronegative LT recipients were more likely to younger (18-39 years old, 15% vs 3%), or older (> 60 years, 74% vs. 50%, p=0.01). Seronegative LT recipients were more likely to be on anti-metabolite therapy (79% vs. 53%, p=0.04) and had a lower median length of time from transplant to vaccination. Among seropositive LT recipients at 3-months, 3 (10%) had delayed seroconversion. Median (IQR) anti-RBD was 61 (4, 233) U/mL 1-month post-D2 (n=26) and 45(11, 299) U/mL 3-months post-D2. Conclusion(s): HT and LT recipients develop a delayed and variable antibody response to mRNA SARS-CoV-2 vaccination. HT recipients more frequently seroconverted, and had higher anti-RBD levels, than LT recipients. Persistent negative and low antibody titers may place LT recipients at the highest risk of breakthrough SARSCoV- 2 infection among SOTRs.
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Purpose: Some solid-organ transplant recipients (SOTRs) with low or negative antibody levels after a 2-dose mRNA vaccine series against SARS-CoV-2 experience boosting after a third dose (D3), but long-term antibody durability after D3 is unknown. We describe six-month SARS-CoV-2 antibody kinetics and durability in 31 SOTRs who received D3. Method(s): 31 SOTRs without prior COVID-19 were identified within our national observational study. Serologic testing was performed a median of 30 (IQR 27-40) days after D3 and repeated at a median of 166 (148-184) days after D3. Semiquantitative anti-spike serologic testing using the Roche Elecsys anti-S enzyme immunoassay (EIA) or EUROIMMUN anti-S1 EIA was performed. Result(s): Over 6 months of follow-up, antibody levels increased in 16/27(59%), remained stable in 6/27(22%) (one negative, the others above the assay limit), and decreased in 5/27(19%). One-month post-D3, 24/31(77%) were seropositive and 7/31(23%) were seronegative. Six-months post-D3, 29/31(94%) were seropositive and 2/31(6%) remained seronegative. Both nonresponders received the BNT-162b2 primary series;one received Ad.26.CoV2.S and the other mRNA-1273 for D3. This difference in seroconversion after D3 was not statistically significant (Fisher exact = 0.49, between primary series). There were no reported cases of COVID-19 during the study period. Conclusion(s): We observed a very high rate of seroconversion after D3 in SOTRs, with marked heterogeneity in timing and strength of response depending on baseline antibody level and vaccine platform received. These results are encouraging evidence for the durable immunogenicity of additional vaccine doses in most SOTRs, and demonstrate the need for dedicated analysis of heterologous boosting strategies.
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Purpose: While SARS-CoV-2 vaccination has dramatically reduced COVID-19 severity in the general population, fully vaccinated solid organ transplant recipients (SOTRs) demonstrate reduced seroconversion and increased breakthrough infection rates. Furthermore, a third vaccine dose only increases antibody and T cell responses in a proportion of SOTRs. We sought to investigate the underlying mechanisms resulting in varied humoral responses in SOTRs. Method(s): Within a longitudinal prospective cohort of SOTRs, anti-spike IgG, total and spike-specific B cells were evaluated in 44 SOTR participants before and after a third vaccine dose using high dimensional flow cytometry to assess immunologic and metabolic phenotypes. B cell phenotypes were compared to those of 10 healthy controls who received a standard two-dose mRNA series. Result(s): Notably, even in the absence anti-spike antibody after two doses, spikespecific B cells were detectable in most SOTRs (76%). While 15% of participants were seropositive before the third dose, 72% were seropositive afterward. B cells, however, were differentially skewed towards non-class switched B cells in SOTRs as compared to healthy control B cells. Expansion of spike-specific class-switched B cells in SOTRs following a third vaccine dose correlated with increased classswitched (IgG) antibody titers. Antibody response to a third vaccine dose was associated with expanded populations of germinal center-like (CD10+CD27+) B cells, as well as CD11c+ alternative lineage B cells with specific upregulation of CPT1a, the rate limiting enzyme of fatty acid oxidation and a preferred energy source of germinal center B cells. Conclusion(s): This analysis defines a distinct B cell phenotype in SOTRs who respond to a third SARS-CoV-2 vaccine dose, specifically identifying fatty acid oxidation as pathway that could be targeted to improve vaccine response such as through targeted immunosuppressive modulation. (Figure Presented).
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Purpose: Mycophenolate mofetil (MMF) use is associated with decreased antibody response to the SARS-CoV-2 mRNA vaccine series in heart and lung transplant recipients (HLTRs). Higher MMF doses have been associated with poor immunogenicity in kidney transplant recipients, but limited data exist on HLTRs. We evaluated the relationship between daily MMF dose and vaccine-induced antibody response in HLTRs. Method(s): HLTRs (n= 212) from an observational cohort were categorized by daily MMF doses (None, Low: <1000mg, Moderate: 1000-2000mg, High: >=2000mg). Semi-quantitative antibody testing was performed at 1, 3, and 6-months post-dose 2 (D2) using the Roche Elecsys anti-SARS-CoV-2 S enzyme immunoassay (EIA), testing for antibodies to SARSCoV2 spike protein receptor binding domain, and the EUROIMMUN EIA, testing for S1 domain of SARS-CoV-2 spike protein. Multivariable Poisson regression was used to estimate the risk of a negative antibody response with increasing MMF dose. Result(s): At the time of vaccination, 94 (44.3%) HLTRs reported receiving no MMF, 33 (15.6%) reported a low dose, 54 (25.7%) reported a moderate dose, and 31 (14.8%) reported a high dose regimen. There were statistically significant differences in the number of participants on mTOR inhibitors and Triple immunosuppression among the groups but the participants in all 4 dose categories were otherwise comparable (Table 1) The risk ratio of a negative post-D2 titer with low, moderate and high dose regimens compared to no MMF was 0.65 1.15 2.05 (p=0.63), 1.34 2.043.10 (p=0.001) and 1.83 2.77 4.21 (p<0.001) after adjusting for age, sex, vaccine type, time since transplant, and corticosteroid use. Conclusion(s): HLTRs taking MMF >1000mg/day are at higher risk of remaining seronegative after mRNA vaccination, with evidence of a dose-nonresponse effect. The findings support the exploration of whether targeted MMF reduction strategies in HLTRs increase SARS-CoV-2 vaccine immunogenicity. (Table Presented).
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Purpose: Understanding risk factors for impaired vaccine responses can guide strategies for testing, additional dose recommendations, and vaccine schedules to provide improved protection in solid organ transplant recipients (SOTRs). Our purpose was to use machine learning to characterize risk factors and create a prediction model for seroconversion after 2-dose mRNA SARS-CoV-2 vaccination. Method(s): Using our national observational cohort of 1031 SOTRs we created a machine learning model using gradient boosting to explore, rank, and quantify the association of 19 clinical factors with antibody responses to 2-dose mRNA vaccination. Gradient boosting is a general-purpose machine learning algorithm that generates a sequence of parsimonious prediction models based on the residual error of the previous models. We measured the area under the receiver operating characteristic curve (AUROC) via a 10-fold cross validation to evaluate the model's performance. Finally, we evaluated the prediction performance of the models in discrimination and calibration with an external cohort of 512 SOTRs from Houston Methodist. Result(s): Mycophenolate mofetil (MMF) use, shorter time since transplant, and older age were the strongest predictors of seronegativity, collectively contributing to 76% of the model's prediction performance (Figure 1). Other clinical factors, including organ type, vaccine type, sex, race, and other immunosuppression medications, showed weaker associations with seronegativity. Longer time since transplant was associated with higher odds of seropositivity, especially during the first 5 years post-transplant (Figure 2a). Older age among those <65 years old (Figure 2b) and MMF (Figure 2c) were associated with lower odds of seropositivity. The model had moderate prediction performance, with an AUROC of 0.79 (our cohort) and 0.67 (Houston Methodist cohort). Conclusion(s): Our machine learning model allows us to identify SOTRs at highest risk of suboptimal immunogenic response to vaccination, highlighting opportunities for improving protection from COVID-19 including more targeted vaccination strategies. (Figure Presented).
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Purpose: To compare antibody response to a third dose (D3) of SARS-CoV-2 vaccine in solid organ transplant recipients (SOTRs) with negative or low-positive antibody levels after 2-dose mRNA vaccination across D3 platforms. Method(s): From our observational study, 532 SOTRs who developed suboptimal antibody responses to 2-dose mRNA vaccination (Roche<50 U/mL or EUROIMMUN <1.1 AU) were selected. Belatacept recipients and persons with any COVID-19 diagnosis were excluded. We compared post-D3 antibody levels among SOTRs who received an mRNA vaccine for D3 (n=487) versus Ad.26.COV2.S for D3 (n=45). Poisson regression with robust standard error was used to study the association between vaccine platform and seroconversion, adjusting for immunosuppression, age, time since transplant, and liver transplant status. Result(s): Pre-D3, 342 SOTRs (64%) were seronegative, of whom 107 (31%) developed high-positive antibody levels post-D3. In contrast, of the 190 (36%) with low-positive pre-D3 antibody levels, 172 (91%) were high-positive post-D3 (Figure 1). Among SOTRs seronegative pre-D3, 1.8x more Ad.26.COV2.S D3 recipients seroconverted compared to mRNA D3 recipients (49.7% vs 27.8%, Fisher's exact=0.014) (Figure 2). Among the pre-D3 seronegative group, there was a 2x higher chance of developing high-positive post-D3 levels with Ad.26.COV2.S compared to mRNA D3 (IRR =1.42.02.9, p<0.001). This was despite the Ad.26. COV2.S D3 group having fewer younger patients and liver transplant recipients, factors that are associated with higher odds of positive antibody response. 165 SOTRs (31%) remained seronegative after D3 (22% of Ad.26.COV2.S recipients vs 32% of mRNA recipients). Conclusion(s): Heterologous boosting with Ad.26.COV2.S may be a promising vaccination option for SOTRs with poor response to the 2-dose mRNA series, particularly among those who are seronegative. (Table Presented).
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Purpose: Post-acute sequelae of SARS-CoV-2 infection (PASC) is an increasingly recognized phenomenon manifested by long lasting cognitive, mental, and physical symptoms. We aimed to estimate the prevalence of PASC symptoms in solid organ transplant recipients (SOTRs) in the short (1- 6 months) and long-term (> 6 months) periods after SARS-CoV-2 infection. We also compared the prevalence of these symptoms between those with SARS-CoV-2 infection requiring hospitalization and those not requiring hospitalization. Method(s): We surveyed 111 SOTRs with self-reported SARS-CoV-2 infection diagnosed more than 4 weeks prior to survey administration. The survey consisted of 7 validated questionnaires ("Quick Dementia Rating System (QDRS)", "Patient Health Questionnaire (PHQ9)", "Generalized Anxiety Disorder 7 (GAD-7)", "Impact of Events Scale (IES-6)", "EuroQol- 5 Dimension (EQ-5D)", "PROMIS global physical health scale (GHS) "and "Breathlessness, Cough and Sputum Scale (BCSS)"). Result(s): Of the 111 survey participants, 32 (33%) had been hospitalized and 35 (36%) had SARS-CoV-2 infection >6 months ago. Median (IQR) age was 58 years (46, 65). Median time from SARS-CoV-2 diagnosis was 167 days (138, 221). Cognitive impairment, anxiety, depression, insomnia, feeling of trauma, fatigue, pain, breathing problems, cough, abnormal smell, abnormal taste, and diarrhea were reported by 40%, 23%, 36%, 55%, 53%, 41%, 19%, 33%, 33%, 21%, 22%, and 32% of patients respectively. Hospitalized patients had poorer scores in cognition (QDRS survey score of 2 versus 0.75, p=0.048) (Figure 1), quality of life (EQ-5D survey score of 2 versus 1, p=0.043), physical health (PROMIS GHS survey score of 10 versus 11, p=0.013), respiratory status (BCSS survey score of 1 versus 0, p=0.056), and pain (Pain score of 3 versus 0, p 0.006). Among patients who had SARS-CoV-2 infection >6 months ago, abnormal breathing, cough, abnormal smell, abnormal taste, and diarrhea continued to be reported by 31%, 31%, 29%, 32%, and 32% of patients respectively. Conclusion(s): After SARS-CoV-2 infection, SOTRs had a high prevalence of PASC symptoms. Some of the symptoms are more severe in patients who had required hospitalization and persist beyond 6 months. Further studies are needed to understand the long term sequalae of SARS-CoV-2 infection in SOTRs and to develop an evidence-based multidisciplinary approach for caring for these patients beyond the acute phase. (Table Presented).