Prévention de l’infection BKv :

La fréquence et la gravité de la néphropathie à BKv chez les transplantés rénaux souligne la nécessité d’une stratégie de prévention de cette infection opportuniste. Certains auteurs insistent sur le fait d’identifier les facteurs de risque de survenue d’infection ou de néphropathie à BKv.

La stratification du risque d’infection à BKv permettra de corriger les facteurs de risque modifiables. Dans le cas échéant identifier les transplantés à haut risque d’infection afin et d’adapter le protocole de dépistage de BKv et le niveau d’immunosuppression en tenant compte du risque immunologique de chaque transplanté. Par ailleurs, l’utilisation de Ciclosporine et d’inhibiteur de mTOR semble dans plusieurs études, avoir une efficacité préventive de l’infection BKv [54,88].

L’utilisation de fluoroquinolones en antibioprophylaxie post-transplantation était proposée par plusieurs auteurs sans évidence nette, et au vue des résultats décevants de plusieurs essais randomisés, les fluoroquinolones ne peuvent être recommandés en prophylaxie [89,90].

CONCLUSION :

Le BK virus, fréquemment réactivé chez le sujet transplanté rénal, potentiellement source d’infection dont la gravité peut aller jusqu’à la perte du greffon. La responsabilité de la néphropathie à BKv dans la perte du greffon rénal reste préoccupante. C’est donc l’unique raison pour dépister très tôt cette complication virale nécessitant un diagnostic précoce à l’aide d’un monitoring virologique pour une meilleure prise en charge sous la forme d’une réduction de l’immunosuppression.

Le seul moyen thérapeutique ayant fait la preuve de son efficacité jusqu’à présent est la diminution de l’immunosuppression, ou la modification du type d’immunosuppresseurs. Les modalités de diminution de l’immunosuppression devraient être envisagées au cas par cas, selon le risque immunologique que présente le patient vue le risque de rejet. Aucun traitement adjuvant, utilisé à visée préventive ou curative, n’a donné de résultat concluant dans de grandes études prospectives randomisées qui pourraient en faire recommander formellement l’utilisation en première intention.

Ainsi, un diagnostic précoce et une restauration rapide de l'immunité, en limitant la réplication virale, est actuellement le moyen le plus efficace de contrôler la maladie.

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Le polyomavirus BK (BKv) est un exemple type de virus opportuniste, dont le pouvoir pathogène s’exprime quasi-exclusivement dans un contexte d’immunosuppression. Le BKv est responsable de néphropathies tubulo-interstitielles, particulièrement chez les patients transplantés de rein.

L’objectif principal est de décrire l’épidémiologie, le type de prise en charge et l’évolution de l’infection à BKv en transplantation rénale.

Matériel et méthodes :Il s’agit d’une étude rétrospective, s’étalant de Janvier 2013 à

Novembre 2019, période à partir de laquelle le laboratoire central de Virologie s’est doté de la technique de recherche de BKv par PCR. Cette étude se porte sur les patients transplantés rénaux ayant bénéficié de suivi régulier dans l’unité de transplantation rénale (TR) du CHU de Rabat.

La recherche de BKv est réalisée de manière systématique dans les urines (charge positive >7log) de façon mensuelle pendant 3 mois, puis trimestrielle durant les 2 premières années de TR, Si cette recherche est positive, le monitorage est réalisée dans le sang par la suite (charge positive >4log).

Résultats :Parmi les 74 patients transplantés, 17 patients ont été inclus avec une charge virale urinaire et sanguine positive. L’âge moyen au diagnostic était de 46 ans +/- 13 ans, avec un sex ratio à 1.84. Le donneur était vivant dans 15 cas.

Le diagnostic a eu lieu en médiane de 7.6 +/- 5.7 mois. Le diagnostic était réalisé dans le cadre de surveillance systématique en post TR, sauf deux cas suite à une IRA. Le créatininémie moyenne était de 12.5mg/l.

Le Tacrolimus était prescrit chez 15 patients et la ciclosporine chez un patient. Le Mycophénolate Mofétil (MMF) était prescrit chez 15 patients, alors que l’Azathioprine était à dans 1 cas. La corticothérapie était prescrite chez tous les patients.

Suite au diagnostic de BKv, le traitement immunosuppresseur est modifié chez 16 patients. La baisse du MMF était réalisée chez 12 patients, alors que 5 patients étaient switchés de Tacrolimus à la Ciclosporine avec baisse des taux résiduels.

La virémie s’est négativée chez 16 patients, après un délai médian de 70 jours [30– 180]. Au terme du suivi, la créatininémie moyenne est de 12 ± 3.1 mg/l.

Conclusion :Le BKv, largement prévalent dans la population générale, est fréquemment réactivé chez le sujet transplanté rénal, potentiellement source d’infection dont la gravité peut aller jusqu’à la perte du greffon. Le seul moyen thérapeutique ayant fait la preuve de son efficacité jusqu’à présent est la diminution de l’immunosuppression, ou la modification du type d’immunosuppresseurs.

Abstract :

Introduction: The BK polyomavirus (BKv) is a typical example of an opportunistic virus, the pathogenicity of which is expressed almost exclusively in a context of immunosuppression. BKv is responsible for tubulo-interstitial nephropathies, particularly in kidney transplant patients.

The main objective is to describe the epidemiology, the type of management and the evolution of BKv infection in renal transplantation.

Material and methods: This is a retrospective study, during the period from January 2013 to November 2019, a period from which the central virology laboratory acquired the technique of BKv research by PCR. This study concerns renal transplant patients who received regular monitoring in the renal transplantation unit (TR) of the University Hospital of Rabat.

The search for BKv is carried out systematically in the urine (positive charge> 7log) monthly for 3 months, then quarterly during the first 2 years of TR, If this search is positive, monitoring is carried out afterwards in the blood ( positive charge> 4log).

Results: Among the 74 transplanted patients, 17 patients were included with a positive urinary and blood viral load. The mean age at diagnosis was 46 +/- 13 years, with a sex ratio of 1.84. The donor was alive in 15 cases.

The diagnosis took place at a median of 7.6 +/- 5.7 months. The diagnosis was performed as part of systematic post-TR surveillance, except in two cases following an acute kidney injury. The mean serum creatinine was 12.5 mg / l.

Tacrolimus was prescribed in 15 patients and cyclosporin in one patient. mycophenolate mofetil (MMF) was prescribed in 15 patients, while azathioprine was prescribed in 1. Corticosteroid therapy was prescribed for all patients.

Following the diagnosis of BKv, immunosuppressive therapy was changed in 16 patients. The decrease in MMF was achieved in 12 patients, while 5 patients were switched from tacrolimus