Our interest in parainfluenza and RS virus surface glycoproteins stems from the critical role they play in virus attachment, virus penetration, host range and tissue specificity. Equally important is the critical role these surface polypeptides play in the induction of immunity to infection and resistance to disease. To date, clones representing four non-surface antigen genes have been identified -- nucleoprotein (44kd), matrix protein (28kd), phosphoprotein (33kd), a non-structural protein (17kd). Characterization and sequencing of the cloned genes is in progress. Although cloned DNA representing the viral glycoproteins has not been identified, it should be possible to produce the desired glycoprotein DNA clones by "walking across" the viral RNA genome (i.e., using cloned DNA as a primer to extend reverse transcription of DNA sequences into an adjacent region of the genome). Optimism for this approach is based upon the fact that the gene order for the parainfluenza viruses appears to be 5' NP, P, Fo, M., HN 3'. If RS virus has the same gene order, clones coding for the M and P genes could be extended into the adjacent genes on the negative-strand template and subsequently amplified by cloning in E. coli.