Use of chemokine receptors by poxviruses.

Chemokine receptors serve as portals of entry for certain intracellular pathogens, most notably human immunodeficiency virus (HIV). Myxoma virus is a member of the poxvirus family that induces a lethal systemic disease in rabbits, but no poxvirus receptor has ever been defined. Rodent fibroblasts (3T3) that cannot be infected with myxoma virus could be made fully permissive for myxoma virus infection by expression of any one of several human chemokine receptors, including CCR1, CCR5, and CXCR4. Conversely, infection of 3T3-CCR5 cells can be inhibited by RANTES, anti-CCR5 polyclonal antibody, or herbimycin A but not by monoclonal antibodies that block HIV-1 infection or by pertussis toxin. These findings suggest that poxviruses, like HIV, are able to use chemokine receptors to infect specific cell subtypes, notably migratory leukocytes, but that their mechanisms of receptor interactions are distinct.

A DSC study of the miscibility of poly(ethylene oxide)-block-poly(DL-lactide) copolymers with poly(DL-lactide).

The purpose of this study was to examine the miscibility of poly(ethylene oxide)-block-poly(DL-lactide) copolymers with poly (DL-lactide). The copolymers L7E73L7 and L17E78L17 (L = carbonyloxymethylmethylene unit, OCOCH(CH3); E = oxyethylene unit, OCH2CH2) were synthesised by non-catalysed anionic polymerisation and characterised by gel permeation chromatography and 13C NMR. Blends of each of the copolymers with poly(DL-lactide) with compositions over the range from 10 to 90 wt% copolymer were cast as thin films and examined by differential scanning calorimetry (DSC) to determine glass transition temperatures (Tg) and melting temperatures (Tm). The phase diagram showed a region of miscibility above the melting point of the copolymer in the system (approx. 35-40 degrees C). Within this region the system was glassy at low mass fractions of oxyethylene in the copolymer (wE < or = 0.1) and rubbery at higher mass fractions. Below Tm a mechanically compatible glassy blend existed at low wE whilst quenching of systems of higher wE led to phase separation, the biphasic region consisting of crystalline Em-sequences of copolymer separated from non-crystalline poly(DL-lactide). The phase diagram resulting from this study provides the means for the design of drug delivery systems based on blends of poly(DL-lactide) and poly(ethylene oxide)-containing components. The crystal melt boundary can be lowered by the use of block copolymers with short poly(ethylene oxide) blocks permitting the preparation of blends which are miscible at room temperature and rubbery or glassy according to composition.

Transforming growth factor-beta in thermally injured patients with hypertrophic scars: effects of interferon alpha-2b.

Hypertrophic scarring is a common dermal fibroproliferative disorder that leads to poor quality wound healing, prolongs rehabilitation, and increases morbidity following major thermal and other injuries to the deep dermis. Local and systemic transforming growth factor (TGF)-beta has been implicated as a fibrogenic cytokine in the pathogenesis of many fibrotic disorders, whereas interferon (IFN) alpha-2b may improve the pathologic features of dermal fibrosis directly or by antagonizing the effects of TGF-beta and histamine. Nine patients with severe hypertrophic scarring were evaluated for 8 weeks before treatment with subcutaneous recombinant IFN alpha-2b, 2 x 10(6) IU three times per week for 24 weeks. Clinical assessment was performed using standardized photography, a burn scar assessment tool, and serial scar volume measurements. Monthly measurements of serum TGF-beta and plasma Ntau-methylhistamine were made prior to, during, and after IFN alpha-2b therapy and compared with 27 age-matched controls. Serial biopsies of the hypertrophic scars and normal skin were performed for evaluation of mast cell numbers. Significant improvement in scar assessment occurred in 7 of 9 patients, and 3 of 9 demonstrated significant reductions in scar volume with interferon therapy beyond that occurring during the 8-week control period. For the entire group, mean rates of improvement were significantly better during interferon therapy with no recurrence following treatment. Before interferon therapy, serum TGF-beta was significantly higher in the burn patients with hypertrophic scarring than in a control population (123.04 +/- 36.48 vs. 56.85 +/- 8.38 ng/ml, p < 0.05). Within 3 months of IFN alpha-2b therapy, serum TGF-beta levels fell significantly and remained within the normal range during therapy and after interferon therapy was stopped. Plasma Ntau-methylhistamine levels were also significantly elevated in the hypertrophic scar patients as compared with age and sex-matched controls (153.6 +/- 92.07 vs. 48.3 +/- 28.9 pg/ml, p < 0.05), and significant reductions were achieved with interferon therapy and maintained after interferon was discontinued. Paired biopsies of hypertrophic scarring and normal tissue demonstrated increased numbers of mast cells in hypertrophic scars compared with normal uninjured skin from the same patients (2.65 +/- 1.63 vs. 1.04 +/- 0.62 cells/high power field, p < 0.001); however, no significant change in mast cell content of the hypertrophic scars accompanied interferon therapy. Patients with severe hypertrophic scarring demonstrate increased levels of serum TGF-beta and plasma Ntau-methylhistamine following thermal injury. A significant clinical improvement in scar quality and volume occurred during IFN alpha-2b therapy, which was associated with normalization of serum TGF-beta and plasma Ntau-methylhistamine levels. A double-blind, placebo-controlled trial will be required to further assess the usefulness of subcutaneous treatment with IFN alpha-2b for the treatment of hypertrophic scarring.

Effect of retinoic acid on expression of transforming growth factor-beta by retinal pigment epithelial cells in culture.

OBJECTIVE: To study the effect of retinoic acid on the expression of transforming growth factor-beta (TGF-beta) by human retinal pigment epithelial (RPE) cells in culture. MAIN OUTCOME MEASURES: Expression of TGF-beta 1 by RPE cells after 24 hours in culture at the messenger RNA level (Northern analysis) and the protein level (enzyme-linked immunosorbent assay [ELISA]). RESULTS: On the basis of cell morphology, growth characteristics and the results of immunohistochemical studies, we concluded that the cells used in these experiments were RPE in origin. Immunohistochemical studies confirmed TGF-beta 1 expression by the RPE cells in culture. Densitometry showed that retinoic acid reduced the level of TGF-beta 1 mRNA expression by 41% compared with control samples. ELISA showed that retinoic acid inhibited TGF-beta expression when compared with the baseline level of TGF-beta in media from RPE cells in culture. CONCLUSIONS: These findings may have implications for the pharmacotherapy of proliferative vitreoretinopathy.