CYP3A5 polymorphisms and their effects on tacrolimus exposure in an ethnically diverse South African renal transplant population.

BACKGROUND: Tacrolimus forms the cornerstone for immunosuppression in solid-organ transplantation. It has a narrow therapeutic window with wide inter- and intra-patient variability (IPV). Cytochrome P-450 3A5 (CYP3A5) is the main enzyme involved in tacrolimus metabolism, and rs776746A>G is the most frequently studied polymorphism in the CYP3A5 gene. The rs776746A>G (i.e. CYP3A5*3) single-nucleotide polymorphism in CYP3A5 alters tacrolimus predose trough concentration (C0) and may also affect IPV, which may lead to immune- and/or drug-mediated allograft injury. CYP3A5*3 may result in absent (*3/*3), partial (*1/*3) or normal (*1/*1) CYP3A5 expression. The effect of CYP3A5*3 on tacrolimus exposure and variability has not been examined in South African (SA) transplant recipients. OBJECTIVES: To determine the frequencies and effect of CYP3A5 and adenosine triphosphate-binding cassette subfamily B member 1 (ABCB1) polymorphisms on tacrolimus C0/dose ratios in different ethnic groups attending a tertiary renal transplant clinic in SA, and other factors that may explain inter- and IPV in tacrolimus C0. METHODS: All consenting stable renal transplant recipients on tacrolimus at the Livingstone Hospital Renal Unit in Port Elizabeth, SA, were included. Tacrolimus concentrations were obtained using a microparticle enzyme immunoassay method (ARCHITECT analyser, Abbott Laboratories). Polymerase chain reaction/restriction fragment length polymorphism was used to genotype for CYP3A5*3 and *6 allelic variants. RESULTS: There were 43 participants (35% black African, 44% mixed ancestry and 21% white), with a mean age of 44.5 years, median duration post-transplant of 47 months and median (interquartile range) creatinine and estimated glomerular filtration rate levels of 118 (92 - 140) µmol/L and 62 (49 - 76) mL/min at study inclusion. The mean tacrolimus C0 in the study was 6.7 ng/mL, with no difference across the different ethnic groups. However, the mean total daily dose of tacrolimus required was 9.1 mg (0.12 mg/kg), 7.2 mg (0.09 mg/kg) and 4.3 mg (0.06 mg/kg) in black, mixed-ancestry and white patients, respectively (p=0.017). The frequencies for CYP3A5 expressors (i.e. CYP3A5*1/*1 + CYP3A5*1/*3 genotypes) were 72%, 100%, 76% and 12% for all patients combined and black, mixed-ancestry and white patients, respectively. The frequencies for CYP3A5 non-expressors (i.e. CYP3A5*3/*3 genotypes) were 0%, 24% and 88% among the black, mixed-ancestry and white patients, respectively. None of the patients carried the CYP3A5*6 allele. CYP3A5*1/*1 and CYP3A5*1/*3 genotype carriers required a two-fold increase in dose compared with the non-expressor genotype carriers, CYP3A5*3/*3 (p<0.05). CYP3A5*3/*3 carriers also demonstrated higher IPV than CYP3A5*1/*1 and *1/*3 carriers (18.1% v. 14.2%; p=0.125). CONCLUSIONS: Compared with global transplant populations, SA renal transplant recipients demonstrated a very high rate of CYP3A5 expression, with a significant impact on tacrolimus pharmacokinetics. Genetic variation in CYP3A5 expression affects tacrolimus dosing requirements, and knowing the CYP3A5 genotype of transplant patients may allow better dose prediction compared with current standard dosing recommendations in a multi-ethnic population. Overall, black African patients required higher doses of tacrolimus than their white counterparts. While further prospective studies are needed to better evaluate dosing algorithms, it would appear that the starting dose of tacrolimus should be higher in black and mixed-race patients.

Virtual reality in surgical arthroscopic training.

Arthroscopy has become an irreplaceble method in diagnostics. The arthroscope, with optics and light source, and the exploratory probe are inserted into the knee joint through two small incisions underneath the patella. Currently, the skills required for arthroscopy are taught through hands-on clinical experience. Therefore, the Fraunhofer-Institut fuer Graphische Datenverarbeitung in Darmstadt, in cooperation with the Berufsgenossenschaftliche Unfallklinik Frankfurt am Main, developed a highly interactive medical training system for arthroscopy through computer graphics and virtual reality (VR) techniques. Two main issues are addressed: the three-dimensional (3-D) reconstruction process and the 3-D interaction. The goal of the reconstruction process is to obtain a realistic representation of the knee joint derived from a magnetic resonance image sequence suitable for computer simulation. Moreover, the 3-D interaction of the training system must stimulate real arthroscopy, providing an intuitive handling of the instruments.

Attempts to reproduce amyotrophic lateral sclerosis in laboratory animals by inoculation of Schu virus isolated from a patient with apparent amyotrophic lateral sclerosis.

A virus isolated from the CSF of a patient who had amyotrophic lateral sclerosis for 7 years, and prolonged pleocytosis in the CSF, was adapted to suckling mouse brain by subsequent serial blind passages. This Schu virus belongs to the tick-borne encephalitis complex of the genus Flavivirus (Togaviridae). Suckling mouse brain homogenate of the 13th passage was used for transmission experiments in various species of laboratory animals. Golden hamsters infected subcutaneously fell ill after a number of months, lost weight, and had paresis of the legs. Histologically they had petechial hemorrhages in different parts of the CNS and inflammatory changes in the gray substance of the spinal cord. Pilot studies with repeated inoculations of small doses of different flavivirus strains suggest a course of the disease in experimental animals which resembles slow-virus infections insofar as no encephalitis is produced and degenerative changes of the anterior horn cells prevail over inflammatory signs in the spinal cord. After intracerebral application of Schu virus, cynomolgus monkeys developed the typical lesions of togavirus panencephalitis with epileptic seizures, ataxia, and paresis. After subcutaneous application, the virus seems to spread along peripheral nerves to anterior spinal roots and spinal cord, where mainly motor neurons of the anterior horn are damaged, and from there to the brain. The histological findings are such that one may assume the disease of the patient was due to the infection with the virus isolated from his CSF. Therefore, the hypothesis may be advanced that at least some of the cases diagnosed as amyotrophic lateral sclerosis are due to a togavirus infection.

An uncommon case of amyotrophic lateral sclerosis with isolation of a virus from the CSF.

An atypical case of amyotrophic lateral sclerosis (ALS) is described, characterized by early manifestation, a long lasting course with asymmetry of the lesions, absence of bulbar symptoms in the presence of an otherwise very advanced symptomatology, and constant signs of an inflammatory reaction in the CSF which was the reason to initiate extensive virological studies, including procedures for virus isolation. A virus belonging to the TbE complex of arbovirus group B (tick-borne flavivures), was finally isolated from the CSF. About 70% of the ALS cases in Hamburg/W. Germany, examined for antibodies, apparently had contact with this virus. The antibody pattern found made it possible to explain this exceptional case.