Cross-reactive immunologic material status affects treatment outcomes in Pompe disease infants.

Deficiency of acid alpha glucosidase (GAA) causes Pompe disease, which is usually fatal if onset occurs in infancy. Patients synthesize a non-functional form of GAA or are unable to form native enzyme. Enzyme replacement therapy with recombinant human GAA (rhGAA) prolongs survival in infantile Pompe patients but may be less effective in cross-reactive immunologic material (CRIM)-negative patients. We retrospectively analyzed the influence of CRIM status on outcome in 21 CRIM-positive and 11 CRIM-negative infantile Pompe patients receiving rhGAA. Patients were from the clinical setting and from clinical trials of rhGAA, were 6 months of age, were not invasively ventilated, and were treated with IV rhGAA at a cumulative or total dose of 20 or 40 mg/kg/2 weeks. Outcome measures included survival, invasive ventilator-free survival, cardiac status, gross motor development, development of antibodies to rhGAA, and levels of urinary Glc(4). Following 52 weeks of treatment, 6/11 (54.5%) CRIM-negative and 1/21 (4.8%) CRIM-positive patients were deceased or invasively ventilated (p<0.0001). By age 27.1 months, all CRIM-negative patients and 4/21 (19.0%) CRIM-positive patients were deceased or invasively ventilated. Cardiac function and gross motor development improved significantly more in the CRIM-positive group. IgG antibodies to rhGAA developed earlier and serotiters were higher and more sustained in the CRIM-negative group. CRIM-negative status predicted reduced overall survival and invasive ventilator-free survival and poorer clinical outcomes in infants with Pompe disease treated with rhGAA. The effect of CRIM status on outcome appears to be mediated by antibody responses to the exogenous protein.

Effects of chronic opioid exposure on guinea pig mu opioid receptor in Chinese hamster ovary cells: comparison with human and rat receptor.

Chronic opioid treatment leads to agonist-specific effects at the mu opioid receptor. The molecular mechanisms resulting from chronic opioid exposure include desensitization, internalization and down-regulation of membrane-bound mu opioid receptors (MOP). The purpose of this study was to compare the cellular regulation of guinea pig, human and rat MOP expressed in Chinese hamster ovary (CHO) cells, following exposure to two clinically important opioids, morphine and methadone. MOP expressing CHO cells were treated in culture with methadone or morphine for up to 48 h. Radioligand diprenorphine and [D-AIa(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO)-stimulated GTP gamma S binding assays were carried out using paired control and opioid-exposed CHO cells. Methadone induced downregulation of the mu opioid receptor, while morphine induced desensitization of the receptor for all three species. Furthermore, morphine predominantly decreased the potency of DAMGO to stimulate GTP gamma S binding, whereas methadone primarily reduced its efficacy. Changes in DAMGO potency and efficacy differed among species and depended on the opioid used to treat the cells. Our results showed similarities between guinea pig and human MOP for morphine-induced desensitization, but identified differences between the two for methadone-induced desensitization. In contrast, human and rat MOP differed in response to morphine treatment, but were not distinct in their response to methadone treatment. The guinea pig is an excellent and established animal model to study opioid effects, but its molecular opioid pharmacology has not been investigated thus far. These results can assist in understanding species differences in the effects of opioid ligands activating the mu opioid receptor.

Guinea pig mu opioid receptor: brainstem expression in the morphine-exposed neonate.

The mu opioid receptor (MOR) has been characterized in the mouse and rat. The guinea pig has several advantages as a model for in utero exposure to morphine; the placental structure is similar to the human; and the guinea pig metabolizes morphine to its active metabolite, morphine-6-glucuronide, at similar rates as humans. Guinea pig MOR cDNA was sequenced. To evaluate expression in respiratory control areas, a guinea pig specific cRNA probe was prepared and utilized for in situ hybridization in brainstem slices. In situ results were compared with immunohistochemistry to determine a correlation between mRNA expression and MOR protein expression. Neonatal animals exposed in utero to chronic intermittent morphine were compared with saline-exposed controls. Quantitative RT-PCR comparison of mRNA expression levels in brainstem regions was also performed. No differences were found in brainstem areas expressing mRNA or amount of mRNA expression between treatment and neonatal age groups. Immunohistochemistry showed that protein expression correlates anatomically with mRNA expression and no difference in protein levels could be detected between treatment groups. Lack of difference in mRNA or protein levels of MOR following in utero exposure to morphine suggests that differences seen between these groups with DAMGO-stimulated 35S-GTPgammaS binding involve a change in efficiency of coupling to G-proteins when MOR is activated.