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The deletion of a conserved sequence of ca. 30 nucleotides in the 5' noncoding leader region of an avian sarcoma virus DNA clone resulted in a loss of infectivity after transfection of chicken embryo fibroblasts. Genetic and biochemical analysis of a representative mutant demonstrated that the env gene was expressed normally. Thus, viral RNA transcription, splicing, and translation were not impaired. The amount of mutant viral RNA encapsidated into virions, however, was severely reduced despite the presence of helper-virus. We conclude that the deleted sequence is an essential cis-acting packaging signal.

Nine patients with advanced chronic obstructive pulmonary disease (COPD) and recent weight loss resulting in a state of mild malnutrition were entered into a refeeding program at a clinical research center. They were divided into two groups, one using a hospital diet and the other a hospital diet with supplementation. Both groups of patients gained significant weight. Refeeding and weight gain were associated with a significant increase in absolute lymphocyte count and with an increase in reactivity to skin test antigens after 21 days of refeeding. Few changes occurred in large numbers of additional serum measurements during the study period. These preliminary observations suggest that dietary and supplementary refeeding may improve the immune responses in patients with COPD.

VCAM-1 is an immunoglobulin superfamily member that mediates adhesion of a variety of leukocytes to endothelial cells. VCAM expression has been associated with a variety of disease states and has been implicated in a number of normal processes. The predominant form of VCAM produced in human endothelial cells is a transmembrane protein containing seven immunoglobulin domains. In this study the murine VCAM gene has been characterized to allow the function(s) of VCAM to be studied in a small genetically accessible animal. While expression of an mRNA encoding a seven-immunoglobulin-domain transmembrane VCAM protein was seen in most tissues, the predominant change in VCAM expression upon interleukin 113 treatment was the induction of an alternatively spliced VCAM mRNA containing only the first three immunoglobulin domains. This message encodes a glycosylphosphatidylinositol (GPI)-anchored form of VCAM, VCAMGPI. VCAMGPI was efficiently cleaved from the cell surface by phosphatidylnositol-specific phospholipase C, mediated adhesion to leukocytes in a very late antigen 4-dependent manner, and was produced by mouse endothelial cell lines in culture. These data demonstrate that alternate forms of VCAM are produced under different physiological conditions and suggest that VCAMGPI may have a distinct role in inflammatory processes.

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