The localization of pp60sr°within adhesion structures of epithelioid rat kidney cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus was compared to the organization of actin, a-actinin, vinculin (a 130,000-dalton protein), tubulin, and the 58,000-dalton intermediate filament protein . The adhesion structures included both adhesion plaques and previously uncharacterized adhesive regions formed at cell-cell junctions. We have termed these latter structures "adhesion junctions." Both adhesion plaques and adhesion junctions were identified by interference-reflection microscopy and compared to the location of pp60à nd the various cytoskeletal proteins by double fluorescence . The results demonstrated that the src gene product was found within both adhesion plaques and adhesion junctions. In addition, actin, a-actinin, and vinculin were also localized within the same pp60 sr°-containing adhesion structures . In contrast, tubulin and the 58,000-dalton intermediate filament protein were not associated with either adhesion plaques or adhesion junctions.Both adhesion plaques and adhesion junctions were isolated as substratum-bound structures and characterized by scanning electron microscopy. Immunofluorescence revealed that pp60grc, actin, a-actinin, and vinculin were organized within specific regions of the adhesion junctions. Heavy accumulations of actin and a-actinin were found on both sides of the junctions with a narrow gap of unstained material at the midline, whereas pp60 ,r, stain was more intense in this central region . Antibody to vinculin stained double narrow lines defining the periphery of the junctional complexes but was excluded from the intervening region . In addition, the distribution of vinculin relative to pp60 ,r, within adhesion plaques suggested an inverse relationship between the presence of these two proteins .Overall, these results establish a close link between the src gene product and components of the cytoskeleton and implicate the adhesion plaques and adhesion junctions in the mechanism of Rous sarcoma virus-induced transformation .Infection of susceptible chicken and mammalian cells with Rous sarcoma virus (RSV) leads to the genetically controlled expression of viral functions and the transformation of these cells to the neoplastic state. This transforming event is mediated by a single genetic locus within the viral genome called the sre gene (46). The product of the src gene is a 60,000-dalton phosphoprotein (pp60-; 3, 29, 34, 39) possessing a unique kinase activity capable of phosphorylating substrate proteins on tyrosine residues (21). Because of this enzymatic activity, transformation in this system has been proposed to involve phosphorylation of host cell proteins (8,21), and recent evidence has indicated that RSV-transformed cells possess ele-

A monoclonal antibody, produced from mice immunized with a herpes simplex virus (HSV)‐infected cell extract, reacts with a molecule which is present in uninfected cells and which accumulates in large amounts during HSV 2 infection. In uninfected cells this molecule is growth regulated, in that exponentially growing cells have intense nuclear immunofluorescence, whereas confluent quiescent cells have little. It has a mol. wt. of 57 000 (p57) in exponential cells, and one of 61 000 (p61) in quiescent cells. In HSV 2‐infected cells, p57 accumulates and nuclear and cytoplasmic immunofluorescence increases. In uninfected cells, p57 also accumulates during heat‐shock treatment, and this is associated with a new immunofluorescence throughout the cytoplasm. We suggest that HSV 2 infection induces a cellular stress response which is involved in the shut‐off of host cell polypeptide synthesis.

Using synthetic peptides, we characterized the B-lymphocyte (antibody) and T-lymphocyte (proliferation) responses to an immunodominant epitope of human immunodeficiency virus type 1 (HIV-1) located near the amino-terminal end of the transmembrane glycoprotein (env amino acids 598 to 609). Both immunoglobulin M (IgM) and IgG antibodies against this epitope appeared early after primary infection with HIV-1. In an animal model, the IgG response to a synthetic peptide derived from this sequence was T-helper-cell dependent, whereas the IgM response was T-cell independent. In addition, antibody generated by immunization with this peptide had HIV-1-neutralizing activity. Greater than 99% (201 of 203) of patients infected with HIV-1 generated antibody to this peptide in vivo; however, only 24% (7 of 29) had T cells that proliferated in response to this peptide in vitro. These observations suggest that different HIV-1 gp4l epitopes elicit B-cell and T-cell immune responses.

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