MO991: Covid-19 Infection After Kidney Transplantation in Spain: Comparable Impact Throughout Six Epidemic Waves

BACKGROUND AND AIMS

The successive COVID-19 epidemic waves have significantly influenced kidney transplantation (KT) programs. Contact protection together with vaccination are the principal protective tools for KT recipients. We reviewed the impact of COVID-19 infection in KT recipients throughout the different epidemic waves.

METHOD

Of 900 active KT recipients in our program, 160 (17.8%) have suffered COVID-19 infection during the six epidemic waves: first (March–August 2020), second (September–December2020), third (January–March 2021), fourth (April–May 2021), fifth (June–September 2021) and sixth (October–December 2021, preliminary data). We compared the clinical evolution and the impact of vaccination.

RESULTS

Infected KT recipients were younger in the third and fourth waves (P  < 0.001). We observed a higher percentage of pneumonia and hospital admission in the first and fifth waves (P = 0.045, P = 0.016) (Table 1), without differences in ICU admission, and with the disappearance of asymptomatic cases after the third wave. The highest mortality was observed in KT recipients >65 years old infected within the first 6 months after KT (P = 0.006) and overall mortality was higher in the first wave (P = 0.033). Mortality in hospitalized KT recipients and those admitted in the ICU were similar along the 5 waves, without clear impact of vaccination (P = 0.251). On the 5 January 2022, we have already accumulated an incidence of COVID in KT of 3.1% (sixth wave, 77% with booster vaccination), similar to the first wave (3.8%), with 12.5% mortality, similar to second, third and fifth waves, in patients with outcome (53.3%).

CONCLUSION

The incidence of COVID-19 in KT recipients has been high in all the waves of the pandemic in Spain. Global mortality has diminished after the first wave, and the time until outcome has increased. The highest mortality occurs in the subgroup of old KT recipients early after KT. Vaccination has not significantly reduced the mortality in KT with Covid who require hospital or ICU admission.

MO984: Increased Mortality After Kidney Transplantation in Mildly Frail Recipients: Need for Pretransplant Intervention

BACKGROUND AND AIMS

Frailty is associated with a higher rate of complications and mortality after kidney transplantation (KT). Physical frailty phenotype (PFP) is the most used frailty instrument among KT recipients, it comprises five criteria and classifies patients as frail if they have ≥3. We aimed to determine the impact of scoring 1 PFP criterion (mild frailty) on transplant outcomes.

METHOD

We have prospectively followed 449 KT candidates evaluated for frailty by PFP at the time of inclusion on the KT waiting list. Patients were classified as follows: 0, robust; 1, pre-frail-1; 2, pre-frail-2; and ≥3, frail. A prospective longitudinal study was performed in all patients in the cohort who underwent KT. Clinical outcomes and survival after transplantation according to frailty status at listing was assessed.

RESULTS

About 71.3% of total listed cohort resulted to be pre-frail (one criterion 41%, two criteria 19.8%) or frail (10.5%). Disparities were observed between sexes, with 5.2% of men and 21.9% of women being frail (P  < 0.01). During the study period (median 26 months [IQR 16–39]), 296 patients got a KT and 153 remained listed. Patients who did not get transplanted were more frequently frail (16.3 versus 7.4%, P = 0.013). Frail patients had more hospital admissions during the first year after listing (43.4% if PFP ≥1 versus 20.8% if PFP = 0) and more cardiovascular events or major infectious events. In a multivariate model including only patients scoring 0 (robust) or prefail-1-criterion (n = 217), older age, previous cerebrovascular disease, peripheral vascular disease and mild pre-frailty were independent risk factors for mortality after KT (Figure 1).

CONCLUSION

Frailty is frequent in KT candidates, more frequent in women than men. Frail patients have less chances to receive a KT. KT candidates are frequently listed with one (out of five) frailty criterion, and this has an independent impact on patient survival after KT. A pre-transplant clinical framework for multimodal prehabilitation interventions to mitigate the effects of frailty and poor fitness after KT may be justified even in mildly pre-frail candidates.

FC 109: Microvascular Inflammation in Kidney Transplant Biopsies in the Absence of HLA-DSA Displays Intense Cytotoxic T-Cell and NK Cell but not Plasma Cell Infiltration

BACKGROUND AND AIMS

Microvascular inflammation (MVI) without evidence of HLA-donor-specific antibodies (HLA-DSA) or C4d+ deposition remains an enigmatic phenotype, which cannot be classified as antibody-mediated rejection (ABMR) according to recent Banff classifications. We aimed to compare peripheral blood lymphocyte (PBL) distribution and infiltrating immune cells in kidney transplant (KT) biopsies presenting MVI (g + ptc ≥ 2) without C4d+ and HLA-DSA, ABMR and normal histology to explore the role of immune cells in these entities.

METHODS

A total of 221 allograft biopsies with ABMR (n = 73), MVI (n = 32) and normal (n = 116) diagnoses were analysed.

RESULTS

MVI patients showed a decrease in the absolute number of T-cells compared with ABMR and normal cases (P = 0.020 and P = 0.006) due to a significant decrease of CD4+ T-cells compared to normal cases (P = 0.013) and a reduction of CD8+ T-cells compared with ABMR (P = 0.029). ABMR and MVI presented a lower absolute number of circulating Natural Killer (NK) cells than normal cases. Immunohistochemistry assessment was performed in 22 ABMR, 13 MVI and 16 normal cases. Glomeruli in ABMR and MVI had more T-cells and CD68+ infiltration than normal biopsies, although TIA1+ was only increased in MVI (P < 0.001), suggesting increased T-cell cytotoxic capacity. Peritubular capillaries displayed more circulating T-cells, CD56+ TIA1+ and CD68+ in ABMR and MVI groups. Contrarily, MVI cases showed mild circulating plasma cell infiltration (CD138+) in peritubular capillaries (P = 0.059) and interstitial aggregates (P = 0.024) compared with ABMR (Figure 1).

CONCLUSION

In conclusion, MVI without HLA-DSA and C4d+ displays decreased circulating T-cell and NK cells, and intense T-cell and NK cell cytotoxic infiltration in the allograft, similar to ABMR. However, the deficiency of plasma cell infiltration in MVI suggests a different underlying stimulus from ABMR.

MO948: Impact of DE Novo Immunosuppression in The Covid-19 Serological Status at Kidney Transplantation

BACKGROUND AND AIMS

COVID-19 infection has heavily impacted our national health system since March-2020. Although the kidney transplant (KT) activity was strongly reduced initially, nowadays it is partially recovered by using ‘COVID-clean’ pathways and vaccination of KT candidates since February-2021. However, scarce information is available regarding how de novo KT immunosuppression influences the serological status of vaccinated recipients.

METHOD

We reviewed the course of 38 de novo KT recipients transplanted between March-September 2021 fully vaccinated before KT. SARS-CoV-2 IgG antibodies against Spike (IgG-S) before and after KT (median: 32 days) were quantified with a serological assay (positive ≥13.0 AU/mL).

RESULTS

Of 38 recipients, 35 showed positive IgG-S at KT (92%). We exclude from the analysis, 4 recipients with COVID infection which interfered the analysis and 5 with inappropriate samples. The remaining 26 recipients had received the second dose of the mRNA vaccine a median time of 48 days before the pre-KT IgG determination. All patients maintained IgG-S over the cut-off after KT, but we observed that half de novo recipients (53.8%) showed a 50% reduction in the level of IgG-S at 1 month: 12/20 (60%) of those who received induction with basiliximab and 2/6 (33%) who received thymoglobulin. Regarding the impact of maintenance immunosuppression under induction with basiliximab, the IgG-S levels halved in 50% of those with tacrolimus-mycophenolate and 67% with tacrolimus-everolimus.

The restricted analysis of IgG-S levels excluding five outliers before KT (>800 AU/mL) showed the most intense reduction in three KT recipients who received thymoglobulin-tacrolimus- mycophenolate (263.8 versus 68.8, 74%) compared with seven basiliximab-tacrolimus-mycophenolate cases (494.4 versus 359.8, 27%) and eleven basiliximab-tacrolimus-everolimus (344.0 versus 306.4, 11%) KT recipients.

CONCLUSION

Immunosuppression in de novo KT recipients reduces significantly the seroprotective levels of antibodies anti-Spike induced by COVID m-RNA vaccines in more than half the recipients. In our experience, the combination of thymoglobulin, tacrolimus and mycophenolate produces a more intense reduction than the combination of basiliximab with tacrolimus and mycophenolate or everolimus.

FC 128NON-HLA ANTIBODIES AND EPLET MISMATCHES IN KIDNEY TRANSPLANT RECIPIENTS WITH A HISTOLOGICAL PICTURE OF ANTIBODY-MEDIATED REJECTION WITH AND WITHOUT HLA DONOR-SPECIFIC ANTIBODIES

Background and Aims

Correlation between antibody-mediated rejection (ABMR) and HLA donor-specific antibodies (DSA) is strong but imperfect in kidney transplant (KT) recipients, raising the possibility of other detrimental antibodies contributing to ABMR. The role of non-HLA antibodies on outcomes is not well known.

Method

We retrospectively assessed KT biopsies scored according to Banff’15 classification. Pre- and post-KT serum samples were checked for HLA and non-HLA antibodies (MICA-Ab, angiotensin II type 1 receptor (AT1R)-Ab, endothelin-1 type A receptor (ETAR)-Ab and crossmatches with primary aortic endothelial cells (EC-XM)). We also analyzed HLA epitope mismatches between donors and recipients.

Results

One-hundred eighteen patients with normal (n=19), ABMR histology (n=52) or IFTA (n=47) in their biopsy were studied. Graft survival was worse in ABMR patients (p=0.003). Pre-KT HLA-DSA were more frequent in ABMR cases (p=0.006). At biopsy, 73% ABMR patients had HLA-DSA (p<0.001). Pre-KT AT1R-Ab were more frequent in ABMR compared with IFTA and normal cases (p=0.003), without differences in other non-HLA antibodies. Fourteen patients with histological ABMR (27%) had no detectable HLA-DSA post-KT and only 3 had non-HLA Ab. However, these ABMR-DSA- cases showed similar biopsy changes and graft survival compared with ABMR-DSA+. Pre- or post-KT non-HLA antibodies other than AT1R-Ab were detected similarly in ABMR and in normal or IFTA cases. Both total class II and DRB1 epitope mismatches were associated with postransplant DSA and ABMR-DSA+. Multivariate analysis showed that both pre-KT HLA-DSA and AT1R-Ab (DSA: OR: 3.39 [1.20-9.59], p=0.021; AT1R-Ab: OR: 5.31 [1.75-16.10], p=0.003) were strong independent predictors of postransplant ABMR-DSA+ (Table 1).

Conclusion

Despite highly prevalent HLA-DSA before and after transplantation in KT with histological ABMR, 27% of cases did not show circulating HLA-DSA. Pre-KT AT1R-Ab associated with ABMR-DSA+, but not MICA-Ab, ETAR-Ab or EC-XM+. Any of them associated significantly with ABMR-DSA-. Epitope mismatch predicted both postransplant DRB-DSA and ABMR-DSA+. Detection of pre-KT HLA-DSA and/or AT1R-Ab, together with HLA epitope mismatch assessment, are valuable tools for better DSA and ABMR prediction in KT patients.

MO954DONOR TYPE INFLUENCE IN EARLY POST KIDNEY TRASPLANTATION HYPERTRANSAMINASEMIA

Background and Aims

The early increase in transaminases after kidney transplant (KT) is a frequent finding. It has been associated with the cross-talk produced between liver and kidney in ischemia-reperfusion situations. However, the influence of the donor type has not been evaluated. We analyze the incidence, relevance and possible correlations of postKT hypertransaminasemia.

Method

Retrospective study (2004-2018) to analyze the increase in serum AST/ALT during the first 3 months after KT in 119 KT recipients of deceased donors, either brain death (DBD n=59), controlled after cardiac death (cDCD n=21) or uncontrolled after cardiac death (uDCD n=39). All recipients received induction with thymoglobulin and maintenance immunosuppression with tacrolimus and mycophenolate.

Results

Recipients of uDCD group were younger, with a higher proportion of men and lower percentage of diabetics and retransplants. Delayed graft function duration was longer, although serum creatinine was similar at 3 months between groups. There were no differences between recipients in terms of past medical liver disease, postKT transfusion requirement or vasoactive drug use. There were also no differences in cumulative thymoglobulin dose, and uDCD recipients presented, as expected, lower levels of tacrolimus at one week postKT (Table).

From all KT recipients, 37.3/45.3% presented with an increase in AST/ALT at 72 hours postKT. Regarding donor type, the percentage of recipients who experienced 72 hours postKT hypertransaminasemia was higher (69.2/82.1% in uDCD group vs 22/29.3% in DBD and 21.1/21.1% in cDCD, p<0.001). This liver function alteration resolved early, and one month after transplant, AST/ALT values in all groups returned to baseline (Figure).

The multivariate analysis showed that uDCD recipients had x10 higher risk of developing early post-KT hypertransaminasemia than the other groups (for AST, OR 10.85 [2.463-47.826] and for ALT OR 11.15 [2.627-47.294]). However, when we tried to correlate this hypertransaminasemia with a prolonged delayed graft function (creatinine decrease> 14 days postKT) we did not find any association.

Conclusion

Early postKT hypertransaminasemia is a frequent and transient event that is related to the kidney donor type, being more frequent in recipients of donors in uncontrolled cardiac death.

FC 129CHANGES IN PERIPHERAL NK CELLS IN KIDNEY TRANSPLANT RECIPIENTS WITH AND WITHOUT HLA DSA

Background and Aims

Antibody-mediated rejection (ABMR) is a frequent cause of renal allograft loss. There is increasing evidence of the role of Natural Killer (NK) cells in the establishment of ABMR damage. Our group described that patients with donor-specific antibodies (DSA) and ABMR present higher proportions of NKG2A+ NK cell subset in peripheral blood than those without HLA DSA or HLA antibodies.

Method

We selected 177 kidney transplant recipients (KT) with renal biopsies 2011-2017: 77 with ABMR (DSA+: 53, DSA-: 24) and 100 without ABMR (DSA+: 15, DSA-: 85). We assessed graft survival with a median time of follow-up since the renal biopsy of 53 months. In 138 KT we evaluated the peripheral blood NK cell immunophenotyping and its value as a prognostic biomarker.

Results

Graft survival was worse in ABMR-KT at the end of follow-up (p<0.001) independently of DSA detection (p=0.63). Regarding NK cell immunophenotyping, we observed a lower proportion and absolute NK cell count in ABMR+DSA+-KT and ABMR+DSA--KT compared with ABMR-DSA--KT (p=0.027, p=0.017). ABMR+DSA+-KT showed higher proportion of NKG2A+ NK cells compared with ABMR-DSA--KT (p=0.007). All ABMR+ patients, independently of DSA detection, presented lower absolute NKG2A- NK cell count in comparison with ABMR-DSA--KT (p=0.001, p=0.017). Finally, a proportion of NKG2A- <30% was associated with lower graft survival 36 months after graft biopsy with ABMR (p=0.067) (Figure).

Conclusion

Graft survival is worse in ABMR+ compared with ABMR- KT independently of DSA detection. Kidney transplant recipients with ABMR show reduced peripheral absolute numbers of NK cells and NKG2A- NK cells regardless of undetectable DSA. This NK cell phenotype associated with a worse medium-term graft survival in cases with ABMR.

P1602MICROVASCULAR INFLAMMATION WITHOUT DSA OR C4D: AN ORPHAN CATEGORY IN BANFF CLASSIFICATION WITH INTENSE CAPILLARITIS AND CYTOTOXIC T-CELL INFILTRATION

Background and Aims

Antibody-mediated rejection (ABMR) associated with donor-specific HLA antibodies (DSA) is the leading cause of late allograft failure after kidney transplantation. Microvascular inflammation (MVI) without detectable circulating DSA or C4d + cannot be classified as ABMR according to Banff-2017. The involvement of intragraft lymphocyte subsets in the development of humoral damage in kidney transplantation (KT) is relevant. We aimed to analyze lymphocyte subset distribution in kidney transplant biopsies (KTBx) with ABMR compared with MVI and with normal KTBx.

Method

KTBx with ABMR, MVI (g+ptc≥2, without DSA) or normal findings were included. DSA were identified with Luminex single antigen assays. Intragraft lymphocyte subsets’ characterization was performed by immunohistochemistry: T-lymphocytes (CD3, CD4, CD8, Foxp3), B-lymphocytes / plasmatic cells (CD20, CD138), NK cells (CD56), macrophages / monocytes (CD68), cytotoxic cells (TIA1) and activated cells (PD1) were evaluated.

Results

We analyzed 34 KTBx: 21 ABMR, 5 MVI and 8 KTBx with normal findings. KT with ABMR and MVI had more proteinuria at the time of the biopsy compared with the normal group (575 mg/24h and 964 mg/24h vs 147 mg/24h, p=0.002 and p=0.005 respectively). DSA were more frequently detected in patients with ABMR (95.2% vs 0% and 37.5%, p<0.001 and p=0.003 respectively). KTBx with ABMR and MVI had increased cytotoxic T-cell infiltration apparently corresponding to NK cells in peritubular capillaries (ptc) compared to normal group. Moreover, both groups showed a greater number of macrophages and monocytes in glomeruli. KT with MVI but not with ABMR had a significantly increased activated cell infiltration (PD1+) in ptc compared to the normal group, and showed an increased cytotoxic T-cell infiltration in glomeruli compared to ABMR and normal groups.

Conclusion

ABMR and MVI have an increased infiltration of NK cells with cytotoxic activity in ptc that differs from the normal group. However, KT with MVI show greater infiltration of activated cells in ptc and cytotoxic T-cell in glomeruli compared to ABMR suggesting the possibility of different activation pathways.

P1601COMPLEMENT MEMBRANE ATTACK COMPLEX DURING THE FIRST WEEK AFTER KIDNEY TRANSPLANTATION AS SEVERITY BIOMARKER TO DELAYED GRAFT FUNCTION

Background and Aims

Ischemia-reperfusion (I/R) damage is a relevant cause of delayed graft function (DGF). Complement activation is involved in experimental I/R injury, but few data are available about the expression of the complement cascade final component -membrane attack complex (MAC)- and I/R injury in KT patients. We studied the dynamics of membrane attack complex (MAC) as plasma fraction (pMAC) and the histological deposit pattern of C3b, complement factor H (FH) and MAC in DGF patients.

Method

We evaluated pMAC levels in 59 recipients, 38 with immediate graft function and 21 without serum creatinine decreased at day 7 (DGF). pMAC was measured at admission for KT (day 0) and 7 days after KT (day 7). Sandwich ELISAs were used to measure MAC. Additionally, we performed imunohistoquimical stained for MAC, C3b and kidney biopsies (KB) with DGF (n=12) and a control group of one-year protocol biopsies without damage (n=4)

Results

Patients in the DGF group were older, more frequently diabetics and received kidneys from older donors and more frequently controlled cardio-circulatory death type.

Day0 and day7 post-KT pMAC levels were similar in non-DGF patients 5902±3049 mAu/L vs 6178±2882 mAu/L; p=0.686). However, patients with DGF showed a significant increase of pMAC levels between day0 and day7 (6621±2202 mAu/L vs 9625±4142 mAu/L; p=0.006. Figure 1

Percentage pMAC levels increase (Δ0-7 pMAC%) discriminative assessment analyzed by ROC curve showed a good discriminative value for DGF with an AUC of 0.78; p<0.001 (sensitivity 81%, specificity 66% by cut-off point of 5%). In patients with DGF longer than ten days, we found more frequently patients with a Δ0-7 pMAC >5% (83% vs 17% Δ0-7 pMAC <5% ; p=0.003).Patients with DGF showed renal function at 3 and 6 months, but worse renal function 1 year after KT (serum creatinine 1.78±0.61 vs 1.35±0.30 mg/dl in non-DGF patients). DGF patients with Δ0-7 pMAC >5% displayed worse renal function 1 and 2 year after KT compared to DGF patients with Δ0-7 pMAC <5%.

MAC, C3b and FH stains were observed in tubular epithelial cells basal membrane. DGF-kidney biopsies showed more frequently high-intensity stain for MAC and FH than controls, without differences to C3b stain. DGF-kidney biopsies also showed a higher number of tubules with positive stain and larger perimeter of tubules with positive stains for MAC, C3b and FH than the controls. Figure 2.

Among the 12 patients with DGF-biopsies, three (25%) never recovered renal function, all of them presented Δ0-7 pMAC >5% and intense, diffuse and positive staining in more than 50% of tubular perimeter for MAC, FH and C3b

Conclusion

Complement activation during peritrasplant period could be related with the severity of graft injury and the presence of DGF. Therefore, the determination of MAC levels could be useful to identify patients with possible complement dependent graft injury that might benefit from complement inhibitor therapies