Navigating the controversy regarding antibiotic prophylaxis in acute variceal bleeding.

Antibiotic prophylaxis in patients with cirrhosis and acute variceal bleeding is part of the standard of care according to most clinical guidelines. However, with recent evidence arguing against antibiotic prophylaxis, the role of this intervention has become less clear.

Cretan HLA genetics supports its early Minoan culture as a link between North Africa and Europe.

HLA studies in Crete show that this population is related to North Africans and also Iberians. This may be a reflection of a common prehistoric first Europeans relationships with North Africans and drying Saharan emigration after 10,000 years BC; it may be specifically represented by a primitive and early cult to the bull in both Cretan (Minoan) and Iberian populations. In the present study, unrelated Cretans representing different Island parts have been studied for class II HLA-DRB1 and -DQB1 alleles. The most frequent ones were HLA-DRB1*11:01 and HLA-DRB1*07:01 and HLA-DQB1*03:01 and DQB1*05:01. Also, the Cretan HLA class II haplotype HLA-DBR1*11:01-DQB1*03:01 had the highest frequency and is also common to other Mediterraneans, including Iberians. In addition, DRB1*07:01-DQB1*02:01 and HLA-DRB1*04:02-DQB1*03:02 Cretan haplotypes are shared with North Africans (the latter with Algerians, Tunisians and Moroccans). In summary, Crete was one of the first European classic cultures (Minoan) which was probably an early link, like Iberia, between North Africa /Sahara and Europe,also supported by genetic results.

Impact of COVID-19 vaccination on liver transplant recipients. Experience in a reference center in Mexico.

BACKGROUND AND AIMS: COVID-19 vaccination has proved to be effective to prevent symptomatic infection and severe disease even in immunocompromised patients including liver transplant patients. We aim to assess the impact of COVID-19 vaccination on the mortality and development of severe and critical disease in our center. METHODS: A retrospective cohort study of LT patients in a reference center between March 2020 and February 2022. Demographic data, cirrhosis etiology, time on liver transplantation, immunosuppressive therapies, and vaccination status were recorded at the time of diagnosis. Primary outcome was death due to COVID-19, and secondary outcomes included the development of severe COVID-19 and intensive care unit (ICU) requirement. RESULTS: 153 of 324 LT recipients developed COVID-19, in whom the main causes of cirrhosis were HCV infection and metabolic-associated fatty liver disease. The vaccines used were BNT162b2 (48.6%), ChAdOx1 nCoV-19 (21.6%), mRNA-1273 vaccine (1.4%), Sputnik V (14.9%), Ad5-nCoV-S (4.1%) and CoronaVac (9.5%). Case fatality and ICU requirement risk were similar among vaccinated and unvaccinated LT patients (adjusted relative case fatality for vaccinated versus unvaccinated of 0.68, 95% CI 0.14-3.24, p = 0.62; adjusted relative risk [aRR] for ICU requirement of 0.45, 95% CI 0.11-1.88, p = 0.27). Nonetheless, vaccination was associated with a lower risk of severe disease (aRR for severe disease of 0.32, 95% CI 0.14-0.71, p = 0.005). CONCLUSIONS: Vaccination reduces the risk of severe COVID-19 in LT patients, regardless of the scheme used. Vaccination should be encouraged for all.

Is iron overload associated with worse outcomes in patients with chronic liver disease undergoing liver transplantation?

Background: Iron overload is frequent in patients with chronic liver disease, associated with shorter survival after liver transplantation in patients with hereditary hemochromatosis. Its effect on patients without hereditary hemochromatosis is unclear. The aim of the study was to study the clinical impact of iron overload in patients who underwent liver transplantation at an academic tertiary referral center. Methods: We performed a retrospective cohort study including all patients without hereditary hemochromatosis who underwent liver transplantation from 2015 to 2017 at an academic tertiary referral center in Mexico City. Explant liver biopsies were reprocessed to obtain the histochemical hepatic iron index, considering a score ≥ 0.15 as iron overload. Baseline characteristics were compared between patients with and without iron overload. Survival was estimated using the Kaplan-Meier method, compared with the log-rank test and the Cox proportional hazards model. Results: Of 105 patients included, 45% had iron overload. Viral and metabolic etiologies, alcohol consumption, and obesity were more frequent in patients with iron overload than in those without iron overload (43% vs. 21%, 32% vs. 22%, p = 0.011; 34% vs. 9%, p = 0.001; and 32% vs. 12%, p = 0.013, respectively). Eight patients died within 90 days after liver transplantation (one with iron overload). Complication rate was higher in patients with iron overload versus those without iron overload (223 vs. 93 events/100 personmonths; median time to any complication of 2 vs. 3 days, p = 0.043), without differences in complication type. Fatality rate was lower in patients with iron overload versus those without iron overload (0.7 vs. 4.5 deaths/100 person-months, p = 0.055). Conclusion: Detecting iron overload might identify patients at risk of early complications after liver transplantation. Further studies are required to understand the role of iron overload in survival.

Different serum sodium assay, different model for end stage liver disease - sodium scores in patients awaiting liver transplant: A cross-sectional study.

INTRODUCTION AND AIMS: Sodium can be measured with direct or indirect methods; abnormal plasma total protein concentration can impact on sodium measured by indirect ion-selective electrodes (ISE). Serum sodium is an important item to determine the Model for End Stage Liver Disease Sodium (MELD-Na) score, commonly used for liver graft allocation. Patients with cirrhosis usually have hypoproteinemia. The aim of this study was to determine if there was a significant difference between the MELD-Na scores calculated based on the results of two different serum sodium ISE: indirect and direct. METHODS: This was a retrospective study; we included 166 patients that underwent liver transplant assessment, and that had paired (i.e. same date and time) direct and indirect sodium determinations. We calculated the MELD-Na scores with both sodium determinations, and we compared them. RESULTS: There was a significant difference between MELD-Na scores; the mean difference was 0.4±1.3. If MELD-Na score had been determined by the sodium measured by the direct ISE, 69 patients (42%) would have stayed in the same place on the waiting list, 67 patients (40%) would have moved up, and 30 patients (18%) would have moved down. CONCLUSIONS: There was a statistically significant difference between the MELD-Na scores calculated based on the two different sodium concentrations, which would theoretically result in changes in the order of the waiting list. This finding should prompt studies to assess if MELD-Na calculated based on direct methods has a better performance to predict clinically relevant outcomes.

Liver transplantation in Latin America: reality and challenges.

Healthcare systems in Latin America are broadly heterogeneous, but all of them are burdened by a dramatic rise in liver disease. Some challenges that these countries face include an increase in patients requiring a transplant, insufficient rates of organ donation, delayed referral, and inequitable or suboptimal access to liver transplant programs and post-transplant care. This could be improved by expanding the donor pool through the implementation of education programs for citizens and referring physicians, as well as the inclusion of extended criteria donors, living donors and split liver transplantation. Addressing these shortcomings will require national shifts aimed at improving infrastructure, increasing awareness of organ donation, training medical personnel, and providing equitable access to care for all patients.

Major histocompatibility complex complement (MHC) Bf alleles show trans species evolution between man and chimpanzee.

HLA and disease studies by using single allele statistics have been fruitless during the last 40 years for explaining association pathogenesis of the associated diseases.Other approaches are necessary to untangle this puzzle. We aim to revisit complement alleleism in humans and primates for both studying MHC and disease association to complotypes and extended MHC haplotypes in order to also explain the positive directional selection of maintaining immune response genes (complement, MHC adaptive and MHC non-specific genes) that keeps these three type of genes together in a short chromosome stretch (MHC) for million years. These genes may be linked to conjointly avoid microbes attack and autoimmunity. In the present paper, it is obtained a new Bf chimpanzee allele, provisionaly named Patr-Bf*A:01,that differs from other Bf alleles by having CTG at eleventh codon of exon 2 in order to start the newly suggested methodology and explain functional and evolutionary MHC obscure aspects. Exons 1 to 6 of Ba fragment of Bf gene were obtained from chimpanzee. This new chimpanzee Factor B allele (Patr-Bf*A:01) is to be identical to a infrequent human Bf allele (SNP rs641153); it stresses the strong evolutive pressure upon certain alleles that are trans specific. It also may apply to MHC extended haplotipes which may conjointly act to start an adequate immune response. It is the first time that a complement MHC class III allele is described to undergo trans species evolution,in contrast to class I and class II alleles which had already been reported . Allelism of complement factors are again proposed for studying MHC complement genes, complotypes, and extended MHC haplotypes which may be more informative that single MHC marker studies.

Approaches to evaluate the specific immune responses to SARS-CoV-2.

The SARS-CoV-2 pandemic has a huge impact on public health and global economy, meaning an enormous scientific, political, and social challenge. Studying how infection or vaccination triggers both cellular and humoral responses is essential to know the grade and length of protection generated in the population. Nowadays, scientists and authorities around the world are increasingly concerned about the arrival of new variants, which have a greater spread, due to the high mutation rate of this virus. The aim of this review is to summarize the different techniques available for the study of the immune responses after exposure or vaccination against SARS-CoV-2, showing their advantages and limitations, and proposing suitable combinations of different techniques to achieve extensive information in these studies. We wish that the information provided here will helps other scientists in their studies of the immune response against SARS-CoV-2 after vaccination with new vaccine candidates or infection with upcoming variants.

HLA alleles and haplotypes in Sudanese population and their relationship with Mediterraneans.

The contribution of migrated people from once green Sahara (about 10,000-6000 years BC) towards Mediterranean area had probably a double effect: both genetic and cultural connections have been described between Western Europe and North Africa. Sudanese populations from different ethnicities have been studied for HLA-A, -B, -DRB1 and -DQB1 antigens by a standard microlymphotoxicity method. Results found show that Nubians are genetically related with African Sub-Saharan populations and distant from other Sudanese tribes, who are closer to Mediterranean populations than to Sub-Saharan ones. This is concordant with other authors and meta-analysis data. Our present work is, to our knowledge, the first and only one HLA research that studies Sudanese people according to different Sudan ethnic groups: samples were collected before Sudan partition between North and South. A prehistoric genetic and peoples exchange between Africa and the Mediterranean basin may be observed and is supported with the results obtained in this Sudanese HLA study. However, demic diffusion model of agriculture and other anthropological traits from Middle East to West Europe/Maghreb do not exist: a more detailed Sahel and North African countries ancient and recent admixture studies are also being carried out which may clearer explain pastoralists/agriculture innovations origins in Eurafrican Mediterranean and Atlantic façade.

[COVID-19 in transplant recipients: Multicentric report of Mexican experience]. / COVID-19 en receptores de trasplante: reporte multicéntrico de la experiencia mexicana.

Background: Solid Organ Transplant recipients (SOTR) appear to be at particular high risk for critical COVID-19 due to immunosuppressive drugs and comorbidities. We report the first description of clinical course and short-term outcomes of kidney and liver transplant recipients with confirmed COVID-19 in Mexico. The objective of this paper was evaluate the clinical course of transplant patients with COVID-19 infection. Material and methods: We retrospectively evaluated SOTR (kidney and liver) over 18 years of age with confirmed diagnosis of COVID-19 from tertiary care centers in Mexico. Results: Data from 45 kidney transplant recipients were recorded. Median (IQR) age was 43 (IQR 25-70) years. Admission to hospital was required in 37 (75.5 %) patients, of which 8 (16.3%) were hospitalized at Intensive Care Unit (ICU). Acute kidney injury (AKI) stage was documented in 33 (67%) patients. The time of hospitalization was 8 (IQR 6-12) days. Six patients died (12.2%). Additionally, data from 10 liver transplant recipients were included. During their evolution, 5 / 10 required hospital admission and there were no deaths in this group. Conclusions: Transplant recipients show a higher fatality rate and complications from SARS-CoV-2 infection; more studies are needed to identify prognostic factors and effective anti-SARS-CoV-2 therapies.

Antecedentes: Los receptores de trasplante de órgano sólido (RTOS) parecen estar en un riesgo particularmente alto de cuadros severos de infección por coronavirus 2 del síndrome respiratorio agudo grave (SARS-CoV-2) debido al uso crónico de medicamentos inmunosupresores y sus comorbilidades. Reportamos la primera descripción del curso clínico y desenlaces a corto plazo de los receptores de trasplante con enfermedad por coronavirus 2019 (COVID-19) confirmada en México. El objetivo de este trabajo es evaluar el curso clínico de estos pacientes. Material y métodos: Evaluamos de manera retrospectiva los RTOS (riñón e hígado) mayores de 18 años de edad, con diagnóstico confirmado de infección por SARS-CoV-2 provenientes de cinco centros de tercer nivel en México. Resultados: Se incluyeron 45 receptores de trasplante renal con una edad de 43 (intervalo intercuartílico [IQR]: 25-70) años. El ingreso hospitalario se requirió en 37 (75.5%) pacientes, de los cuales ocho (16.3%) fueron hospitalizados en la unidad de terapia intensiva. Se documentó lesión renal aguda en 33 (67%) pacientes. El tiempo de hospitalización fue de 8 (IQR: 6-12) días. Seis pacientes fallecieron (12.2%). Adicionalmente, 10 receptores de trasplante hepático fueron incluidos. Durante su evolución, 5 / 10 requirieron ingreso hospitalario; no se presentaron fallecimientos en este grupo de pacientes. Conclusiones: Los receptores de trasplante mostraron una alta tasa de mortalidad y complicaciones por la infección por SARS-CoV-2. Son necesarios más estudios para identificar los factores pronósticos y modalidades de tratamiento eficaces.

Sofosbuvir plus glecaprevir/pibrentasvir as salvage therapy after liver transplantation in NS5A inhibitor-experienced patients. A case series.

BACKGROUND: Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antivirals achieves a sustained virologic response rate higher than 95%. However, virologic failure remains a clinical challenge, and data on retreatment are limited, especially in special populations such as liver transplant (LT) recipients. OBJECTIVES: This study evaluated the sofosbuvir plus glecaprevir-pibrentasvir (GLE/PIB) regimen in LT recipients who had failed to a nonstructural protein 5A (NS5A) inhibitor-based regimen. MATERIAL AND METHODS: Retrospective study of 111 liver transplant recipients between January 2018 and December 2020; 18 patients presented with HCV recurrent infection after LT, out of whom three had a history of at least one NS5A inhibitor-based regimen. Salvage therapy with sofosbuvir plus GLE/PIB was started for 12 weeks; baseline characteristics and outcomes were recorded. RESULTS: All three patients (100%) achieved an undetectable HCV viral load 12 weeks after treatment completion. No serious adverse events were observed. CONCLUSION: In our series, sofosbuvir plus GLE/PIB for 12 weeks is an effective and safe salvage therapy after LT in patients previously treated with NS5A inhibitors.

ANTECEDENTES: El tratamiento del virus de la hepatitis C (VHC) crónica con antivirales de acción directa logra tasas de respuesta virológica sostenida superiores a 95 %. Sin embargo, el manejo del fracaso virológico sigue siendo un desafío clínico y la evidencia sobre el retratamiento es limitada, especialmente en poblaciones como los receptores de trasplante hepático (TH). OBJETIVO: Este estudio evaluó el régimen de sofosbuvir más glecaprevir/pibrentasvir (GLE/PIB) en receptores de TH en quienes falló el régimen basado en inhibidores de la proteína no estructural 5A (NS5A). MATERIAL Y MÉTODOS: Estudio retrospectivo de 111 pacientes trasplantados entre enero de 2018 y diciembre de 2020; 18 pacientes presentaron infección recurrente por VHC posterior al TH, tres de ellos tuvieron antecedentes de al menos un régimen basado en inhibidores de NS5A. Se inició terapia de rescate con sofosbuvir más GLE/PIB durante 12 semanas posterior al TH; se registraron las características basales de los pacientes y sus desenlaces. RESULTADOS: En los tres pacientes se logró obtener una carga viral indetectable de VHC a las 12 semanas de finalizar el tratamiento. No se observaron eventos adversos graves. CONCLUSIÓN: En nuestra serie, sofosbuvir más GLE/PIB durante 12 semanas demostró ser una terapia de rescate efectiva y segura posterior al TH en pacientes previamente tratados con inhibidores de NS5A.

Sofosbuvir más glecaprevir/pibrentasvir como terapia de rescate postrasplante hepático en pacientes con exposición previa a inhibidores de NS5A. Serie de casos / Sofosbuvir plus glecaprevir/pibrentasvir as salvage therapy after liver transplantation in NS5A inhibitor-experienced patients. A case series

Resumen Antecedentes: El tratamiento de la infección crónica por el virus de la hepatitis C (VHC) con antivirales de acción directa logra tasas de respuesta virológica sostenida superiores a 95 %. Sin embargo, el manejo del fracaso virológico sigue siendo un desafío clínico y la evidencia sobre el retratamiento es limitada, especialmente en poblaciones como los receptores de trasplante hepático (TH). Objetivo: Este estudio evaluó el régimen de sofosbuvir más glecaprevir/pibrentasvir (GLE/PIB) en receptores de TH en quienes falló el régimen basado en inhibidores de la proteína no estructural 5A (NS5A). Material y métodos: Estudio retrospectivo de 111 pacientes trasplantados entre enero de 2018 y diciembre de 2020; 18 pacientes presentaron infección recurrente por VHC posterior al TH, tres de ellos tuvieron antecedentes de al menos un régimen basado en inhibidores de NS5A. Se inició terapia de rescate con sofosbuvir más GLE/PIB durante 12 semanas posterior al TH; se registraron las características basales de los pacientes y sus desenlaces. Resultados: En los tres pacientes se logró obtener una carga viral indetectable de VHC a las 12 semanas de finalizar el tratamiento. No se observaron eventos adversos graves. Conclusión: En nuestra serie, sofosbuvir más GLE/PIB durante 12 semanas demostró ser una terapia de rescate efectiva y segura posterior al TH en pacientes previamente tratados con inhibidores de NS5A.

Abstract Background: Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antivirals achieves a sustained virologic response rates higher than 95%. However, virologic failure remains a clinical challenge, and data on retreatment are limited, especially in special populations such as liver transplant (LT) recipients. Objective: This study evaluated the sofosbuvir plus glecaprevir-pibrentasvir (GLE/PIB) regimen in LT recipients who had failed to a nonstructural protein 5A (NS5A) inhibitor-based regimen. Material and methods: Retrospective study of 111 liver transplant recipients between January 2018 and December 2020; 18 patients presented with HCV recurrent infection after LT, out of whom three had a history of at least one NS5A inhibitor-based regimen. Salvage therapy with sofosbuvir plus GLE/PIB was started for 12 weeks; baseline characteristics and outcomes were recorded. Results: All three patients (100%) achieved an undetectable HCV viral load 12 weeks after treatment completion. No serious adverse events were observed. Conclusion: In our series, sofosbuvir plus GLE/PIB for 12 weeks is an effective and safe salvage therapy after LT in patients previously treated with NS5A inhibitors.

Consensus document on acute-on-chronic liver failure (ACLF) established by the Mexican Association of Hepatology.

Acute-on chronic liver failure (ACLF) has been an intensively debated topic mainly due to the lack of a unified definition and diagnostic criteria. The growing number of publications describing the mechanisms of ACLF development, the progression of the disease, outcomes and treatment has contributed to a better understanding of the disease, however, it has also sparked the debate about this condition. As an attempt to provide medical professionals with a more uniform definition that could be applied to our population, the first Mexican consensus was performed by a panel of experts in the area of hepatology in Mexico. We used the most relevant and impactful publications along with the clinical and research experience of the consensus participants. The consensus was led by 4 coordinators who provided the most relevant bibliography by doing an exhaustive search on the topic. The entire bibliography was made available to the members of the consensus for consultation at any time during the process and six working groups were formed to develop the following sections: 1.- Generalities, definitions, and criteria, 2.- Pathophysiology of cirrhosis, 3.- Genetics in ACLF, 4.- Clinical manifestations, 5.- Liver transplantation in ACLF, 6.- Other treatments.

Portopulmonary Hypertension: An Updated Review.

Portal hypertension may have major consequences on the pulmonary vasculature due to the complex pathophysiological interactions between the liver and lungs. Portopulmonary hypertension (PoPH), a subset of group 1 pulmonary hypertension (PH), is a serious pulmonary vascular disease secondary to portal hypertension, and is the fourth most common subtype of pulmonary arterial hypertension. It is most commonly observed in cirrhotic patients; however, patients with noncirrhotic portal hypertension can also develop it. On suspicion of PoPH, the initial evaluation is by a transthoracic echocardiogram in which, if elevated pulmonary pressures are shown, patients should undergo right heart catheterization to confirm the diagnosis. The prognosis is extremely poor in untreated patients; therefore, management includes pulmonary arterial hypertension therapies with the aim of improving pulmonary hemodynamics and moving patients to orthotopic liver transplantation (OLT). In this article, we review in detail the epidemiology, pathophysiology, process for diagnosis, and most current treatments including OLT and prognosis in patients with PoPH. In addition, we present a diagnostic algorithm that includes the current criteria to properly select patients with PoPH who are candidates for OLT.

Correlation of Internal Jugular Vein Collapsibility With Central Venous Pressure in Patients With Liver Cirrhosis.

We aimed to compare internal jugular vein and inferior vena cava ultrasonography as predictors of central venous pressure in cirrhotic patients. We performed ultrasound assessments of the internal jugular vein (IJV) and the inferior vena cava and then invasively measured central venous pressure (CVP). We then compared their correlation with CVP and performed area under the receiver operating characteristic curves to determine which had best sensitivity and specificity. IJV cross-sectional area collapsibility index at 30° correlated better with CVP ( r = -0.56, P < 0.001), and an IJV AP-CI at 30° ≤ 24.8% was better at predicting a CVP ≥8 mm Hg, with 100% sensitivity and 97.1% specificity. Thus, IJV point-of-care ultrasound might be superior than inferior vena cava point-of-care ultrasound as a predictor of CVP in cirrhotic patients.

HLA study in Iranian desert Yazd province inhabitants.

Yazd City (1,200,000 inhabitants) is placed in the middle of its Iran desert province and it was constructed on a oasis in ancient times.However,it was a central point on the Silk Road and merchants from both Asia and Mediterranean/European areas crossed through Yazd City.We have studied HLA-A,-B,-DRB1 and DQB1 alleles in Yazd population.Analysys of nine most frequent extended class I and class II haplotypes shows that four of them are specific of this population.The other six haplotypes are also found in Asian and Mediterranean populations in significant frequency. This supports that the nowadays relatively isolated in desert Yazd area also contains people that may bear HLA genes probably originated because of long lasting merchants route between Europe and Asia through the European/Asian Silk Road in addition to other HLA genes close to other Iranian populations, including Kurds.

HLA-DMB alleles and haplotypes in Ecuador (Cuenca) Amerindians: Importance for HLA and disease studies.

HLA-DMB allele frequencies and HLA-DBM-DRB1-DQB1 extended haplotypes were studied for the first time in Amerindians (Cuenca city area, Ecuador). It was found that most common extended haplotypes gathered the most frequent HLA-DRB1 Amerindian alleles. HLA-DMB polymorphism studies may be important to uncover HLA and diseases pathogenesis and also in an extended HLA haplotype frameshift. HLA-DM molecule has a crucial role together with CLIP protein in HLA class II peptide presentation. HLA extended haplotypes including complement and non classical genes alleles are proposed to HLA and disease studies.

HLA study in Mexico Nahua/Aztec Amerindians: Close relatedness to the ancient Central America ethnic groups.

Nahua population (also named Aztec or Mexica) was studied for HLA class II genes in a Mexican rural city (Santo Domingo Ocotitlan, Morelos State) belonging to the nowadays Náhuatl speaking areas in Mexico. The most frequent HLA class II alleles were typical Amerindian (HLA-DRB1*04:07, DQB1*03:01 DRB1*04:03 or DRB1*04:04) and also were some calculated extended haplotypes (HLA-DRB1*04:07-DQB1*03:02,DRB1*08:02-DQB1*04:02, or DRB1*10:01-DQB1*05:01 among others). When using HLA-DRB1 Neís genetic distances, our isolated Nahua population was found to be close to other Central America Amerindians like the ancient-established Mayans or Mixe. This may suggest that Nahuas origin was also from Central America. It contrasts to legend that assumes they came from the North, and they built the Aztec Empire after submitting Central America neighbouring ethnic groups before 1519 CE when Spaniards led by Hernán Cortés arrived to Mexico.

Role of mTOR inhibitor in the cellular and humoral immune response to a booster dose of SARS-CoV-2 mRNA-1273 vaccine in kidney transplant recipients.

Background: Immunocompromised patients have an increased risk of developing severe COVID disease, as well as a tendency to suboptimal responses to vaccines. The objective of this study was to evaluate the specific cellular and humoral adaptive immune responses of a cohort of kidney transplant recipients (KTR) after 3 doses of mRNA-1273 vaccine and to determinate the main factors involved. Methods: Prospective observational study in 221 KTR (149 non infected), 55 healthy volunteers (HV) and 23 dialysis patients (DP). We evaluated anti-spike (by quantitative chemiluminescence immunoassay) and anti-nucleocapsid IgG (ELISA), percentage of TCD4+ and TCD8+ lymphocytes producing IFNγ against S-protein by intracellular flow cytometry after Spike-specific 15-mer peptide stimulation and serum neutralizing activity (competitive ELISA) at baseline and after vaccination. Results: Among COVID-19 naïve KTR, 54.2% developed cellular and humoral response after the third dose (vs 100% in DP and 91.7% in HV), 18% only showed cell-mediated response, 22.2% exclusively antibody response and 5.6% none. A correlation of neutralizing activity with both the IgG titer (r=0.485, p<0.001) and the percentage of S-protein-specific IFNγ-producing CD8-T cells (r=0.198, p=0.049) was observed. Factors related to the humoral response in naïve KTR were: lymphocytes count pre-vaccination >1000/mm3 [4.68 (1.72-12.73, p=0.003], eGFR>30 mL/min [7.34(2.72-19.84), p<0.001], mTOR inhibitors [6.40 (1.37-29.86), p=0.018]. Infected KTR developed a stronger serologic response than naïve patients (96.8 vs 75.2%, p<0.001). Conclusions: KTR presented poor cellular and humoral immune responses following vaccination with mRNA-1273. The immunosuppression degree and kidney function of these patients play an important role, but the only modifiable factor with a high impact on humoral immunogenicity after a booster dose was an immunosuppressive therapy including a mTOR inhibitor. Clinical trials are required to confirm these results.