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OBJECTIVES: To describe the management of haematological patients experiencing prolonged SARS-CoV-2 viral shedding, as the optimal management strategy for this condition remains undetermined. METHODS: We conducted a retrospective evaluation of our prospectively followed cohort of haematological patients treated with remdesivir for more than 10 days. Starting January 2023, upon COVID-19 diagnosis, the treatment strategy was based on symptoms and PCR cycle threshold (Ct) as follows: (i) when Ct was 25 or less or if the patient had symptoms, a course of remdesivir for at least 10 days, nirmatrelvir/ritonavir for 5 days (whenever possible) and convalescent plasma was administered; and (ii) when the patient was asymptomatic and had a PCR Ct of more than 25, when possible, a course of 5 days of nirmatrelvir/ritonavir was administered. The patient was considered to have achieved viral clearance and, thus, remdesivir was stopped, in either of these cases: (i) PCR negativity, or (ii) subgenomic RNA negativity. RESULTS: From January to November 2023, 18 patients benefited from a safe extended remdesivir administration, resulting in detection of SARS-CoV-2 viral clearance in a median time of 3.5 weeks (IQR 2.6-3.9) (min-max 1.6-8.0). No clinical or biological side effects were detected. No patient died or needed further treatment for their COVID-19 episode. CONCLUSIONS: The extended course of remdesivir, combined with other active therapies for COVID-19 infection, was well tolerated. Cure and virus negativity were obtained in all these high-risk patients.
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Enhancing our comprehension of mRNA vaccines may facilitate the future design of novel vaccines aimed at augmenting immune protection while minimising reactogenic responses. Before this design is carried out, it is important to determine whether adaptive immunity correlates with the reactogenicity profile of vaccines. We studied a large cohort that was vaccinated with mRNA vaccines to answer this question. This was an observational study with real-world data. Reactogenicity data were obtained from the VigilVacCOVID study. Immunogenicity (humoral and cellular) data were retrieved from health records. One main population (n = 215) and two subpopulations were defined (subpopulation 1, n = 3563; subpopulation 2, n = 597). Sensitivity analyses were performed with subpopulations 1 and 2 to explore the consistency of results. We analysed the association of the intensity and types of adverse reactions with the development and quantity of elicited antibody titres. As an exploratory analysis in subpopulation 1, we assessed the association between reactogenicity and cellular immunogenicity. A higher incidence of fever, malaise, and myalgia including severe cases was significantly associated with the development and quantity of positive antibody titres. No significant findings were observed with cellular immunity. We observed a positive association between immunogenicity and reactogenicity. These findings can be relevant for the future development of our understanding of how mRNA vaccines function.
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INTRODUCTION: There is no reliable microbiological marker to guide responses to antiviral treatment in kidney transplant recipients (KTR) with COVID-19. We aimed to evaluate the dynamics of subgenomic RNA (sgRNA) RT-PCR before and after receiving treatment with remdesivir compared with genomic RNA (gRNA) RT-PCR and its use as a surrogate marker of viral replication. METHODS: We analyzed gRNA and sgRNA at baseline and after remdesivir treatment in KTR who received remdesivir for SARS-CoV-2 infection from November 2021 to February 2022. RESULTS: Thirty-four KTR received remdesivir for SARS-CoV-2 infection. The median time since transplantation was 80 months (IQR 3-321) and 75% of patients had previously received 3 doses of a mRNA SARS-CoV-2 vaccine. Three patients (8%) were classified with mild, 25 (73%) with moderate, and 6 (17%) with severe SARS-CoV-2 infection. Thirty-two (94%) patients received 5 doses of remdesivir and two patients received 2 doses. The median time between symptom onset to remdesivir treatment was 5 days (IQR 3-8.5). The median days of hospitalization were 6 (IQR 2-112). gRNA was positive in all patients at baseline and after remdesivir. Five (15%) patients had negative sgRNA at baseline and 20 (59%) after receiving remdesivir. Patients presenting with negative sgRNA at baseline were discharged from hospital in ≤ 6 days without complications. Moreover, those with negative sgRNA after remdesivir therapy did not require ICU admission and had favorable outcomes. Nevertheless, patients with positive sgRNA after antiviral treatment presented worse outcomes, with 47% requiring ICU admission and the three (9%) recorded deaths in the study were in this group. CONCLUSIONS: Based on these data, we hypothesize that sgRNA may have clinical utility to help monitor virologic response more accurately than gRNA in KTR who receive remdesivir. Moreover, patients with negative sgRNA at baseline may not require antiviral treatment and others presenting positive sgRNA at day 5 could benefit from prolonged or combined therapies.
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BACKGROUND: We aimed to describe a cohort of hematologic patients with COVID-19 treated with antivirals early. METHODS: Non-interventional chart review study. Comparison of baseline characteristics and outcomes in high-risk hematologic patients treated with remdesivir between December 2021 and April 2022 versus those treated with nirmatrelvir/ritonavir between May and August 2022. RESULTS: Eighty-three patients were analyzed. Forty-two received remdesivir, and 41 nirmatrelvir/ritonavir. Patients with remdesivir were younger, vaccinated with lower number of doses, and received prior corticosteroids less frequently and sotrovimab, hyperimmune plasma and corticosteroids more often. Viral shedding median (IQR) duration was 18 (13-23) and 11 (8-21) days in the remdesivir and nirmatrelvir/ritonavir groups, respectively (p = 0.004). Median (IQR) Ct values before treatment were similar in both groups. Within 5 days of treatment, median (IQR) Ct values were 26 (23-29) and 33 (30-37) in the remdesivir and nirmatrelvir/ritonavir groups, respectively (p < 0.0001). All patients were hospitalized for remdesivir administration and only four (9.8%) in the nirmatrelvir/ritonavir group. The overall outcomes in this cohort of COVID-19 patients with Omicron variant was good, as no patient needed oxygen or ICU admission. One patient in remdesivir group died from septic shock. No severe adverse event was recorded in both treatment groups. CONCLUSIONS: Patients with hematologic malignancies and non-severe COVID-19 who received nirmatrelvir/ritonavir experienced faster decrease in viral load and shorter viral shedding. Furthermore, besides the advantage of oral administration, nirmatrelvir/ritonavir administration reduced the need of hospital admission.
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COVID-19 , Neoplasias Hematológicas , Lactamas , Leucina , Nitrilos , Prolina , Humanos , Ritonavir/uso terapéutico , SARS-CoV-2 , Corticoesteroides , Antivirales/uso terapéutico , Tratamiento Farmacológico de COVID-19RESUMEN
PURPOSE: We aimed to evaluate the performance of the FilmArray (FA) meningitis/encephalitis (ME) panel. Secondarily, we analyzed the false positive (FP) and false negative (FN) results, as well as the predictive values of the technique, regarding the cerebrospinal fluid (CSF) characteristics. METHODS: FA is a multiplex real-time PCR detecting 14 of the most common ME pathogens in CSF. All FA performed at our hospital (2018-2022) were retrospectively reviewed. FA was compared to conventional techniques and its performance was assessed based on the final diagnosis of the episode. RESULTS: FA was performed in 313 patients with suspicion of ME. Most patients had altered mental status (65.2%) and fever (61%). Regarding CSF characteristics, 49.8% and 53.7% presented high CSF proteins and pleocytosis, respectively. There were 84 (26.8%) positive FA results, mainly for HSV-1 (10.9%), VZV (5.1%), Enterovirus (2.6%), and S. pneumoniae (1.9%). In the 136 cases where both FA and routine methods were performed, there was a 25.7% lack of agreement. We identified 6.6% FN results, but 28.6% FP, mainly due to HSV-1. This resulted in a high negative predictive value (NPV) of 93.4%, but a positive predictive value (PPV) of 73%. Remarkably, PPV as low as 36.9%, and 70.2%, were found in cases without pleocytosis, or lack of high CSF protein levels, respectively. CONCLUSION: FA was associated with high NPV, but frequent FP results and low PPV, particularly for HSV-1, and especially in patients without high CSF protein levels or pleocytosis.
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Encefalitis , Meningitis , Meningoencefalitis , Humanos , Meningitis/diagnóstico , Encefalitis/diagnóstico , Reacción en Cadena en Tiempo Real de la Polimerasa , Estudios Retrospectivos , Leucocitosis , Meningoencefalitis/diagnóstico , Reacción en Cadena de la Polimerasa Multiplex/métodosRESUMEN
Cytomegalovirus (CMV) infection is a relevant cause of morbimortality in patients receiving allogeneic stem cell transplantation (allo-HCT). Foscarnet (FCN) is an effective drug against CMV administered intravenously and usually on an inpatient basis. The Home Care Unit (HCU) for hematologic patients at our hospital designed an at-home FCN administration model to avoid the hospitalization of patients requiring FCN treatment. This study analyzes whether the at-home administration of FCN is as safe and effective as its hospital administration. We collected and compared demographic, clinical, analytical, and economic data of patients with CMV infection post-allo-HCT who received FCN in the hospital (n = 16, 17 episodes) vs. at-home (n = 67, 88 episodes). The proportions of patients with cured CMV infections were comparable between the two groups (65.9% vs. 76.5%, p = 0.395). The median duration of FCN treatment was 15 (interquartile range [IQR] 9-23) and 14 (IQR 11-19) days in the HCU and inpatient cohorts, respectively (p = 0.692). There were no significant differences in the FCN toxicities between groups except for hypocalcemia (26.1% vs. 58.8%, p = 0.007), which was more prevalent in the inpatient cohort. A significant cost-effectiveness was found in the HCU cohort, with a median savings per episode of EUR 5270. It may be concluded that home administration of FCN is a safe, effective, and cost-efficient therapeutic option for patients with CMV infection and disease.
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IMPORTANCE: This observation provides comprehensive data on the clinical correlates of both cytomegalovirus (CMV) genotypic follow-up and clinical monitoring and outcomes for two different solid organ transplantation recipients that received letermovir as secondary prophylaxis. Our study emphasizes that monitoring of CMV disease in the patient and early genotypic detection of resistance mutations are essential when using new antiviral drugs for off-label indication in patients experiencing CMV relapses or not responding to standard antiviral therapy. These cases and the bibliography reviewed can be helpful for other researchers and clinicians working in the field to optimize the use of new treatments for transplant recipients since drug-resistant CMV infection is an important emerging problem even with new developments in antiviral treatment.
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Infecciones por Citomegalovirus , Trasplante de Órganos , Humanos , Antivirales/uso terapéutico , Infecciones por Citomegalovirus/tratamiento farmacológico , Infecciones por Citomegalovirus/prevención & control , Citomegalovirus/genética , Receptores de Trasplantes , Trasplante de Órganos/efectos adversosRESUMEN
OBJECTIVES: We aimed to describe the clinical outcomes and duration of viral shedding in high-risk patients with haematological malignancies hospitalized with COVID-19 during Omicron variant predominance who received early treatment with antivirals. METHODS: We conducted a prospective observational study on high-risk haematological patients admitted in our hospital between December 2021 and March 2022. We performed detection techniques on viral subgenomic mRNAs until negative results were obtained to document active, prolonged viral replication. RESULTS: This analysis included 60 consecutive adults with high-risk haematological malignancies and COVID-19. All of these patients underwent early treatment with remdesivir. Thirty-two (53%) patients received combined antiviral strategies, with sotrovimab or hyperimmune plasma being added to remdesivir. The median length of viral replication-as measured by real-time RT-PCR and/or subgenomic RNA detection-was 20 (IQR 14-28) days. Prolonged viral replication (6 weeks after diagnosis) was documented in six (10%) patients. Only two patients had prolonged infection for more than 2 months. Overall mortality was 5%, whereas COVID-19-related mortality was 0%. CONCLUSIONS: Current outcomes of high-risk patients with haematological malignancies hospitalized with COVID-19 during Omicron variant predminance are good with the use of early antiviral strategies. Persistent viral shedding is uncommon.
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COVID-19 , Fármacos Dermatológicos , Neoplasias Hematológicas , Adulto , Humanos , Antivirales/uso terapéutico , Neoplasias Hematológicas/complicaciones , Neoplasias Hematológicas/tratamiento farmacológico , SARS-CoV-2 , ARN SubgenómicoRESUMEN
The influenza virus has accompanied humans since time immemorial, in the form of annual epidemics and occasional pandemics. It is a respiratory infection with multiple repercussions on people's lives at an individual and social level, as well as representing a significant burden on the health system. This Consensus Document arises from the collaboration of various Spanish scientific societies involved in influenza virus infection. The conclusions drawn are based on the highest quality evidence available in the scientific literature and, failing that, on the opinion of the experts convened. The Consensus Document addresses the clinical, microbiological, therapeutic, and preventive aspects (with respect to the prevention of transmission and in relation to vaccination) of influenza, for both adult and pediatric populations. This Consensus Document aims to help facilitate the clinical, microbiological, and preventive approach to influenza virus infection and, consequently, to reduce its important consequences on the morbidity and mortality of the population.
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Enfermedades Transmisibles , Gripe Humana , Orthomyxoviridae , Adulto , Niño , Humanos , Gripe Humana/diagnóstico , Gripe Humana/prevención & control , Gripe Humana/tratamiento farmacológico , Salud Pública , Medicina Comunitaria , VacunologíaRESUMEN
The inï¬uenza virus has accompanied humans since time immemorial, in the form of annual epidemics and occasional pandemics. It is a respiratory infection with multiple repercussions on people's lives at an individual and social level, as well as representing a signiï¬cant burden on the health system. This Consensus Document arises from the collaboration of various Spanish scientiï¬c societies involved in inï¬uenza virus infection. The conclusions drawn are based on the highest quality evidence available in the scientiï¬c literature and, failing that, on the opinion of the experts convened. The Consensus Document addresses the clinical, microbiological, therapeutic, and preventive aspects (with respect to the prevention of transmission and in relation to vaccination) of inï¬uenza, for both adult and pediatric populations. This Consensus Document aims to help facilitate the clinical, microbiological, and preventive approach to inï¬uenza virus infection and, consequently, to reduce its important consequences on the morbidity and mortality of the population.
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Enfermedades Transmisibles , Gripe Humana , Orthomyxoviridae , Niño , Adulto , Humanos , Gripe Humana/diagnóstico , Gripe Humana/prevención & control , Salud Pública , Medicina Comunitaria , VacunologíaRESUMEN
OBJECTIVES: To review the drug-drug interactions between tacrolimus and lopinavir/ritonavir in 23 patients who received solid organ transplant during the first wave of COVID-19 and to determine the efficacy as well as safety of prednisone monotherapy. METHODS: Observational study performed between March and June 2020 in solid organ transplant recipients admitted with an established diagnosis of SARS-CoV-2 infection who received lopinavir/ritonavir (≥2 doses). Once lopinavir/ritonavir therapy was initiated, calcineurin inhibitor treatment was temporarily switched to prednisone monotherapy (15-20 mg/d) to avoid drug-drug interactions and toxicity. After lopinavir/ritonavir treatment completion, immunosuppressive treatment was restarted with reduced doses of prednisone-tacrolimus (target minimum blood concentration -C0- approximately 5 ng/mL). Patients were observed for 3 months to confirm the absence of rejection. RESULTS: The median time from discontinuation of tacrolimus to initiation of lopinavir/ritonavir was 14 hours (interquartile range [IQR], 12-15) and from discontinuation of lopinavir/ritonavir to resumption of tacrolimus 58 hours (IQR, 47-81). The duration of lopinavir/ritonavir treatment was 7 days (IQR, 5-7). Nine of the 21 (42.8%) patients on tacrolimus treatment had C0 above the cutoff point after lopinavir/ritonavir initiation, despite having been substituted with prednisone before lopinavir/ritonavir initiation. Three patients had very high concentrations (>40 ng/mL) and developed toxicity. No episodes of acute rejection were diagnosed. DISCUSSION: We did not observe toxicity in patients for whom tacrolimus was discontinued 24 hours before starting lopinavir/ritonavir and reintroduced at half dose 48 to 72 hours after lopinavir/ritonavir discontinuation. Prednisone monotherapy during lopinavir/ritonavir therapy was safe with no episodes of acute rejection. Experience with lopinavir/ritonavir may be applicable to the use of nirmatrelvir/ritonavir, but larger multicentre studies are needed to confirm these findings.
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COVID-19 , Trasplante de Órganos , Humanos , Ritonavir/efectos adversos , Lopinavir/efectos adversos , SARS-CoV-2 , Inhibidores de Proteasas , Tacrolimus/efectos adversos , Prednisona/efectos adversos , Tratamiento Farmacológico de COVID-19 , Interacciones Farmacológicas , Receptores de TrasplantesRESUMEN
Remdesivir (RDV) was the first antiviral drug approved by the FDA to treat severe coronavirus disease-2019 (COVID-19) patients. RDV inhibits SARS-CoV-2 replication by stalling the non structural protein 12 (nsp12) subunit of the RNA-dependent RNA polymerase (RdRp). No evidence of global widespread RDV-resistance mutations has been reported, however, defining genetic pathways to RDV resistance and determining emergent mutations prior and subsequent antiviral therapy in clinical settings is necessary. This study identified 57/149 (38.3%) patients who did not respond to one course (5-days) (n = 36/111, 32.4%) or prolonged (5 to 20 days) (n = 21/38, 55.3%) RDV therapy by subgenomic RNA detection. Genetic variants in the nsp12 gene were detected in 29/49 (59.2%) non responder patients by Illumina sequencing, including the de novo E83D mutation that emerged in an immunosuppressed patient after receiving 10 + 8 days of RDV, and the L838I detected at baseline and/or after prolonged RDV treatment in 9/49 (18.4%) non responder subjects. Although 3D protein modeling predicted no interference with RDV, the amino acid substitutions detected in the nsp12 involved changes on the electrostatic outer surface and in secondary structures that may alter antiviral response. It is important for health surveillance to study potential mutations associated with drug resistance as well as the benefit of RDV retreatment, especially in immunosuppressed patients and in those with persistent replication. IMPORTANCE This study provides clinical and microbiologic data of an extended population of hospitalized patients for COVID-19 pneumonia who experienced treatment failure, detected by the presence of subgenomic RNA (sgRNA). The genetic variants found in the nsp12 pharmacological target of RDV bring into focus the importance of monitoring emergent mutations, one of the objectives of the World Health Organization (WHO) for health surveillance. These mutations become even more crucial as RDV keeps being prescribed and new molecules are being repurposed for the treatment of COVID-19. The present article offers new perspectives for the clinical management of non responder patients treated and retreated with RDV and emphasizes the need of further research of the benefit of combinatorial therapies and RDV retreatment, especially in immunosuppressed patients with persistent replication after therapy.
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COVID-19 , SARS-CoV-2 , Humanos , SARS-CoV-2/genética , SARS-CoV-2/metabolismo , Tratamiento Farmacológico de COVID-19 , Adenosina Monofosfato/uso terapéutico , Adenosina Monofosfato/metabolismo , Antivirales/uso terapéutico , Antivirales/químicaRESUMEN
Respiratory virus infection can cause severe illnesses capable of inducing acute respiratory failure that can progress rapidly to acute respiratory distress syndrome (ARDS). ARDS is related to poor outcomes, especially in individuals with a higher risk of infection, such as the elderly and those with comorbidities, i.e. obesity, asthma, diabetes mellitus and chronic respiratory or cardiovascular disease. Despite this, effective antiviral treatments available for severe viral lung infections are scarce. The coronavirus disease 2019 (COVID-19) pandemic demonstrated that there is also a need to understand the role of airborne transmission of respiratory viruses. Robust evidence supporting this exists, but better comprehension could help implement adequate measures to mitigate respiratory viral infections. In severe viral lung infections, early diagnosis, risk stratification and prognosis are essential in managing patients. Biomarkers can provide reliable, timely and accessible information possibly helpful for clinicians in managing severe lung viral infections. Although respiratory viruses highly impact global health, more research is needed to improve care and prognosis of severe lung viral infections. In this review, we discuss the epidemiology, diagnosis, clinical characteristics, management and prognosis of patients with severe infections due to respiratory viruses.
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COVID-19 , Síndrome de Dificultad Respiratoria , Virus , Humanos , Anciano , SARS-CoV-2 , Antivirales/uso terapéutico , BiomarcadoresRESUMEN
Several genetic polymorphisms of the innate immune system have been described to increase the risk of cytomegalovirus (CMV) infection in transplant patients. The aim of this study was to assess the impact of a polygenic score to predict CMV infection and disease in high risk CMV transplant recipients (heart, liver, kidney or pancreas). On hundred and sixteen CMV-seronegative recipients of grafts from CMV-seropositive donors undergoing heart, liver, and kidney or pancreas transplantation from 7 centres were prospectively included for this purpose during a 2-year period. All recipients received 100-day prophylaxis with valganciclovir. CMV infection occurred in 61 patients (53%) at 163 median days from transplant, 33 asymptomatic replication (28%) and 28 CMV disease (24%). Eleven patients (9%) had recurrent CMV infection. Clinically and/or functionally relevant single nucleotide polymorphisms (SNPs) from TLR2, TLR3, TLR4, TLR7, TLR9, AIM2, MBL2, IL28, IFI16, MYD88, IRAK2 and IRAK4 were assessed by real time polymerase chain reaction (RT-PCR) or sequence-based typing (PCR-SBT). A polygenic score including the TLR4 (rs4986790/rs4986791), TLR9 (rs3775291), TLR3 (rs3775296), AIM2 (rs855873), TLR7 (rs179008), MBL (OO/OA/XAO), IFNL3/IL28B (rs12979860) and IFI16 (rs6940) SNPs was built based on the risk of CMV infection and disease. The CMV score predicted the risk of CMV disease with an AUC of the model of 0.68, with sensitivity and specificity of 64.3 and 71.6%, respectively. Even though further studies are needed to validate this score, its use would represent an effective model to develop more robust scores predicting the risk of CMV disease in donor/recipient mismatch (D+/R-) transplant recipients.
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Infecciones por Citomegalovirus , Lectina de Unión a Manosa , Antivirales/uso terapéutico , Infecciones por Citomegalovirus/prevención & control , Ganciclovir/uso terapéutico , Humanos , Inmunidad Innata , Estudios Prospectivos , Receptor Toll-Like 3 , Receptor Toll-Like 4 , Receptor Toll-Like 7 , Receptor Toll-Like 9 , Receptores de TrasplantesRESUMEN
BACKGROUND: This study describes the genotypic and phenotypic characterization of novel human cytomegalovirus (HCMV) genetic variants of a cohort of 94 clinically resistant HCMV patients. METHODS AND RESULTS: Antiviral-resistant mutations were detected in the UL97, UL54, and UL56 target genes of 25 of 94 (26.6%) patients. The genotype-phenotype correlation study resolved the status of 5 uncharacterized UL54 deoxyribonucleic acid polymerase (G441S, A543V, F460S, R512C, A928T) and 2 UL56 terminase (F345L, P800L) mutations found in clinical isolates. A928T conferred high, triple resistance to ganciclovir, foscarnet, and cidofovir, and A543V had 10-fold reduced susceptibility to cidofovir. Viral growth assays showed G441S, A543V, F345L, and P800L impaired viral growth capacities compared with wild-type AD169 HCMV. Three-dimensional modeling predicted A543V and A928T phenotypes but not R512C, reinforcing the need for individual characterization of mutations by recombinant phenotyping. CONCLUSIONS: Extending mutation databases is crucial to optimize treatments and to improve the assessment of patients with resistant/refractory HCMV infection.
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Infecciones por Citomegalovirus , ADN Polimerasa Dirigida por ADN , Humanos , Cidofovir/uso terapéutico , ADN Polimerasa Dirigida por ADN/genética , Proteínas Virales/genética , Farmacorresistencia Viral/genética , Ganciclovir/uso terapéutico , Citomegalovirus/genética , Antivirales/uso terapéutico , Fenotipo , MutaciónRESUMEN
A monkeypox (MPX) outbreak has expanded worldwide since May 2022. We tested 147 clinical samples collected at different time points from 12 patients by real-time PCR. MPX DNA was detected in saliva from all cases, sometimes with high viral loads. Other samples were frequently positive: rectal swab (11/12 cases), nasopharyngeal swab (10/12 cases), semen (7/9 cases), urine (9/12 cases) and faeces (8/12 cases). These results improve knowledge on virus shedding and the possible role of bodily fluids in disease transmission.
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Monkeypox virus , Mpox , ADN Viral/genética , Humanos , Mpox/diagnóstico , Mpox/epidemiología , Monkeypox virus/aislamiento & purificación , Saliva , Semen , España/epidemiologíaRESUMEN
We documented a hematologic patient with prolonged SARS-CoV-2 viral replication in whom emergence of viral mutations was documented after the consecutive use of antivirals and convalescent plasma. The virus detected in the last of 12 clinical samples (day 237) had accumulated 22 changes in amino acids and 29 in nucleotides. Some of these changes, such as the E484Q, were mutations of concern as defined by WHO. This finding represents an enormous epidemiological threat and poses a major clinical challenge. Combined antiviral strategies, as well as specific strategies related to the diagnostic approach of prolonged infections for this specific population, may be needed.
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De novo mutations in the UL56 terminase subunit and its associated phenotypes were studied in the context of cytomegalovirus (CMV) transplant recipients clinically resistant to DNA-polymerase inhibitors, naive to letermovir. R246C was the only UL56 variant detected by standard and deep sequencing, located within the letermovir-resistance-associated region (residues 230-370). R246C emerged in 2/80 transplant recipients (1 hematopoietic and 1 heart) since first cytomegalovirus replication and responded transiently to various alternative antiviral treatments in vivo. Recombinant phenotyping showed R246C conferred an advanced viral fitness and was sensitive to ganciclovir, cidofovir, foscarnet, maribavir, and letermovir. These results demonstrate a low rate (2.5%) of natural occurring polymorphisms within the letermovir-resistant-associated region before its administration. Identification of high replicative capacity variants in patients not responding to treatment or experiencing relapses could be helpful to guide further therapy and dosing of antiviral molecules. IMPORTANCE We provide comprehensive data on the clinical correlates of both CMV genotypic follow-up by standard and deep sequencing and the clinical outcomes, as well as recombinant phenotypic results of this novel mutation. Our study emphasizes that the clinical follow-up in combination with genotypic and phenotypic studies is essential for the assessment and optimization of patients experiencing HCMV relapses or not responding to antiviral therapy. This information may be important for other researchers and clinicians working in the field to improve the care of transplant patients since drug-resistant CMV infections are an important emerging problem even with the new antiviral development.