Jack H. Nunberg

Release of Human Serum Albumin from Poly(lactide-co-glycolide) Microspheres

Human serum albumin (HSA) was encapsulated in a 50:50 copolymer of DL-lactide/glycolide in the form of microspheres. These microspheres were used as a model formulation to study the feasibility of controlling the release of large proteins over a 20- to 30-day period. We show that HSA can be successfully incorporated into microspheres and released intact from these microspheres into various buffer systems at 37°C. A continuous release of the protein could be achieved in physiological buffers at 37°C over a 20- to 30-day period from microspheres with high protein loadings (11.6%). These results demonstrate the potential of poly(DL-lactide-co-glycolide) microspheres for continuous delivery of large proteins.

Analysis of the Human Ia Antigens by Gene Cloning

We have constructed a cDNA library from mRNA derived from membrane-bound polyribosomes from a B cell line and have identified a subset of clones containing B cell-specific sequences. One of the clones in this subset, pDRα-1, which encodes the entire a chain of the HLA-DR antigen, was isolated with a synthetic oligonucleotide hybridization probe and identified by DNA sequence analysis (1). Using the technique of genomic blotting with DNA derived from a somatic cell variant (6.3.6) which contains a small deletion on chromosome 6 (2), we have mapped genomic restriction fragments complementary to the pDRα-1 probe to the region defined by the 6.3.6 deletion. Using DNA from an HLA-typed family, we have demonstrated cosegregation of a polymorphic restriction fragment with a unique parental HLA haplotype. These genomic blot studies indicate that the HLA-DR α gene is a single copy locus. In addition, we have identified a number of cDNA clones, related to but distinct from the pDRα-1 clone, suggesting that there are at least three, and possibly several more, genes encoding DRα-related chains. Finally, we have identified cDNA clones which encode a product which co-migrates in 2D gels with the Ii polypeptide associated with HLA DR immunoprecipitates.