Exogenous apotransferrin and exchange transfusions in hereditary iron overload disease

The Finnish Disease Heritage III: the individual diseases

This article is the third and last in a series entitled The Finnish Disease Heritage I-III. All the 36 rare hereditary diseases belonging to this entity are described for clinical and molecular genetic purposes, based on the Finnish experience gathered over a period of half a century. In addition, five other diseases are mentioned. They may be included in the list of the "Finnish diseases" after adequate complementary studies.

The GRACILE syndrome, a neonatal lethal metabolic disorder with iron overload

GRACILE syndrome (Fellman syndrome, MIM 603358), an autosomal recessive metabolic disorder of the Finnish disease heritage, has been diagnosed in 25 infants of 18 families. The incidence is at least 1/47,000 in Finland. The main findings are fetal growth retardation, Fanconi type aminoaciduria, cholestasis, iron overload (liver hemosiderosis, hyperferritinemia, hypotransferrinemia, increased transferrin iron saturation, and free plasma iron), profound lactic acidosis, and early death. The pathophysiology of the metabolic disturbance is unsolved. No significant deficiency of complex III activity of respiratory chain has been found, although we recently showed that the underlying genetic cause is a missense mutation (S78G) in the BCS1L gene and other mutations in that gene have been associated with complex III deficiency. BCS1L encodes a mitochondrial protein, acting as a chaperone in the assembly of complex III. Iron accumulation in liver, a typical feature being less abundant with increasing age, might be a primary abnormality or a secondary phenomenon due to liver dysfunction. In order to decrease the iron overload, three infants have been repeatedly treated with apotransferrin followed by exchange transfusion. Improvement in iron biochemistry occurred, but no clear beneficial effect on the clinical condition was found. Further studies will elucidate the role of iron in the pathophysiology of the disease.

Antenatal diagnosis of hereditary fetal growth retardation with aminoaciduria, cholestasis, iron overload, and lactic acidosis in the newborn infant

OBJECTIVE

A prenatal diagnosis of the fetus for a mother of two previously deceased infants who died from the recently described autosomal recessive disease (OMIM 603358). The infants presented with intrauterine growth retardation, aminoaciduria, cholestasis, iron overload, severe lactic acidosis, and early death (GRACILE syndrome).

STUDY DESIGN

DNA was extracted from the fibroblasts and tissue samples of the deceased infants, parental leukocytes, and from a chorion villus biopsy in the next pregnancy. Haplotypes were determined using the relevant markers flanking the disease-associated region of chromosome 2.

RESULTS

Both deceased infants were homozygous for the four critical markers. The fetal haploptypes were identical to those of the siblings and the pregnancy was terminated. The iron content of the fetal liver was increased (5000 microg/g) compared with the controls, with a marked iron accumulation in the Kupffer cells.

CONCLUSIONS

Antenatal diagnosis can be performed based on linkage analysis in families with at least one affected child because the disease locus has been assigned to a restricted chromosomal region. Typical histological abnormalities may be present in early fetal life.

ABCB6 (MTABC3) excluded as the causative gene for the growth retardation syndrome with aminoaciduria, cholestasis, iron overload, and lactacidosis

GRACILE syndrome (growth retardation, aminoaciduria, cholestasis, iron overload, lactacidosis, and early death; OMIM 603358) is a rare metabolic disorder with autosomal recessive mode of inheritance. So far it has been diagnosed only in patients with Finnish ancestors. The GRACILE locus has been positioned to a restricted region of chromosome 2q33-37, but the causative gene remains to be identified. The ABCB6 gene, involved in iron homeostasis, mitochondrial respiratory function, and maintenance of the stability of mitochondrial DNA, has been positioned to this same chromosomal region, and advocated in literature as a highly probable candidate gene for the syndrome on both functional and positional grounds. We carried out sequence and quantitative expression analyses to detect potential disease-associated mutations in the ABCB6 gene. No mutations in the coding region of ABCB6 were found, and the expression level of ABCB6 in patient fibroblasts was found to be comparable to controls. Haplotype analysis of the critical DNA region provided evidence for positional exclusion also. Based on these data, ABCB6 is not the causative gene for GRACILE syndrome.

The future of plasma derivatives

In the early 1980s, the advent of recombinant DNA technology provided the perspective of an unlimited supply of recombinant plasma proteins. However, the cost of mammalian cell expression, downstream processing, and the development time of biotechnological pharmaceuticals have generally been underestimated. Despite the initial optimism that plasma derivatives would soon become obsolete, no more than three plasma proteins have been licensed for therapeutic use since that time. The current situation favours a reappraisal of plasma derivatives, which nowadays can meet safety standards similar to those of recombinant products. In terms of cost, human blood has the further advantage over biotechnological sources in that it allows the production of multiple pharmaceutical proteins from one single material. This provides a favourable starting point for exploring the therapeutic potential of the numerous plasma proteins that have remained unused so far.

Development of a pharmaceutical apotransferrin product for iron binding therapy

High-dose chemotherapy of patients with haematological malignancies results in extracellular iron accumulation and appearance of non-transferrin-bound iron, which is thought to predispose the patients to septic infections and contribute to organ toxicity. We describe the development of a human plasma-derived apotransferrin product for iron binding therapy. The product is purified from Cohn fraction IV of human plasma by two ion exchange chromatography steps and ultrafiltration. The process comprises solvent detergent treatment as the main virus inactivation step and 15 nm virus filtration and polyethylene glycol precipitation as removal steps for physico-chemically resistant infectious agents. Product characterization by electrospray and MALDI-TOF mass spectrometry indicated no other chemical modifications than N-linked glycan chains and disulphide bonds, except minor oxidation. The purity of the product was more than 98%, main impurities being IgG, IgA and hemopexin. The product had intact iron binding capacity and native conformation. A stable liquid formulation for the finished product was developed. The product has proved safe and well tolerated in early clinical trials in iron binding therapy.

The capacity of different infusion fluids to lower the prooxidant activity of plasma iron: an important factor in resuscitation?

BACKGROUND

Prooxidant activity of non-protein-bound iron (NPBI) is an important contributor to reactive oxygen species-induced injury after the resuscitation of critically ill patients. Plasma NPBI occurs in critically ill adults, children, and newborn babies, who often require resuscitation. The ability of the resuscitation fluids to bind iron and lower the patients' NPBI levels in vitro has not previously been studied.

STUDY DESIGN AND METHODS

In an in vitro model, highly iron-saturated cord blood plasma from 10 preterm and 10 term babies was mixed with FFP, pasteurized plasma protein solution, and 0.9-percent saline. Plasma from 10 healthy adult volunteers was used as a control. Before and after the mixing with any resuscitation fluid, NPBI levels and ceruloplasmin iron-oxidizing and transferrin iron-binding antioxidant capacities were measured.

RESULTS

After the in vitro mixing with FFP, the incidence and concentration of NPBI were markedly decreased and the iron-binding antioxidant capacity was increased in the plasma of the preterm and term babies. Being mixed with pasteurized plasma protein solution and 0.9-percent saline did not influence the iron-binding antioxidant capacity of newborn babies' plasma. In the control plasma, results were not changed after the mixing with any resuscitation fluid. In every group, the iron-oxidizing antioxidant capacity was not changed after the mixing with any fluid.

CONCLUSION

Iron-induced oxidative tissue damage may be influenced by resuscitation fluids. In the ongoing debate over the choice of crystalloid or colloid resuscitation fluids, the influence of each fluid on the patient's antioxidant capacity warrants more attention.