The CD4 molecule, which is expressed by a subset of mature human T cells, has been identified as the cellular receptor for the human immunodeficiency virus type I (HIV I)' (1, 2). In searching for the putative region in the HIV I envelope protein that interacts with the CD4 receptor, we postulated that this virus had evolved to mimic the natural ligand of CD4. It was previously established that CD4 plays an auxiliary role during T cell activation, probably by interacting with MHC class II molecules on APCs that also serve as restriction elements for presentation of foreign antigens to the T cell receptors (3-5). Furthermore, results from a study in which chimeric class I/class II molecules bearing L cells were used led us to suspect that the NH2-terminal domain of the MHC class II ,B chain (,B 1 domain) is involved in CD4 binding (5).In this report we describe a computer search comparing the conserved amino acid regions of HLA class 11 a and 0 chains with the amino acid sequences of HIV I proteins . This search identified an homology between two highly conserved sequences in the 0 1 domain of HLA class II molecules and in the gp41 region of HIV I envelope protein.To assess the biological relevance of this homology, peptides from the conserved regions of HIV gp41 and HLA class II were synthesized and tested for their ability to generate antibodies that would recognize the native protein molecules. This report describes the generation of murine mAbs against the gp41-derived peptide and their crossreactivity on native HIV I env as well as on human class II antigens. Moreover, in screening of HIV I-infected individuals, 'Abbreviations used in this paper: AA, amino acids; CSA, chicken serum album; HIV 1, human immunodeficiency virus type I.

BruceUa abortus may be useful as a component of vaccines. This is because it possesses several unique properties as a carrier that enable it to stimulate human B cells even in the relative absence of T cells. Human immunodeficiency virus type 1 proteins conjugated to B. abortus could induce neutralizing antibodies against human immunodeficiency virus type 1. Recently we showed that the characteristics of lipopolysaccharide (LPS) derived from B. abortus are similar to those of the whole bacterium in that the LPS acts as a T-independent type 1 carrier in mice. In this study we wanted to determine whether LPS derived from B. abortus is associated with the adverse effects seen with other bacterial endotoxins. LPS purified from B. abortus by butanol extraction was shown to have <2% (wt/wt) contamination by protein and < 1% (wt/wt) contamination by nucleic acids and to contain 1% (wt/wt) ketodeoxyoctanic acid. Compared with LPS derived from Escherichia coli, B. abortus LPS was 10,000-fold less potent in eliciting fever in rabbits, 268-fold less potent in killing D-galactosamine-sensitized mice, and 1,400-fold and 400-fold less potent in inducing interleukin-1 and tumor necrosis factor alpha production, respectively. These results suggest that B. abortus LPS is much less likely than the LPS from E. coli to evoke endotoxic shock; therefore, it may be feasible to incorporate B. abortus as a component of vaccines.

Mesosomal vesicles and plasma membranes were isolated from Staphylococcus aureus ATCC 6538P by protoplasting and differential centrifugation. The lipids of each of the two membrane fractions were extracted with pyridine-acetic acid-N-butanol, and the nonlipid contaminants were removed by Sephadex treatment. The lipids were then separated by passage through diethylaminoethyl-cellulose columns and characterized by thin-layer chromatographic, chemical, and spectral analyses. The lipids were separated into four discrete diethylamino

In the present study inactivated human immunodeficiency virus type 1 (HIV-1) was conjugated to Brucella abortus and tested for immunogenicity in normal and anti-L3T4-treated BALB/c mice. HIV-BA was more immunogenic than uncoupled HIV in normal mice, since 6-fold less virus in HIV-BA preparations elicited higher titer responses than HIV-1 alone. Furthermore, the HIV-BA antibody response reached higher levels before the HIV-1 response. Immunoblot analysis showed that most of the HIV-1 antigens were recognized by antibodies induced by either HIV-1 or HIV-BA. Isotype analysis revealed that HIV-1 induced similar levels of IgG1 and IgG2a antibodies, whereas the IgG2a responses to HIV-BA were more pronounced than the IgG1 response. These different IgG subclass patterns suggest that conjugation of HIV-1 to BA changed the immunogenic nature of HIV-1. The requirement for helper T cells was examined by immunizing mice that were depleted of CD4+ T cells by in vivo anti-L3T4 treatment. Under these conditions the IgG responses to HIV-1 were completely eliminated. Although HIV-BA antibody responses were markedly reduced in anti-L3T4-treated mice, anti-HIV-1 antibodies, mainly of the IgG2a isotype, were produced. The antibodies generated by HIV-1 and HIV-BA immunization were also tested for their ability to inhibit syncytia formed by infecting CD4 + CEM cells with gp160 vaccinia. Sera from normal mice, immunized with either HIV-1 or HIV-BA were capable of inhibiting syncytia. In contrast, following anti-L3T4 treatment, only mice immunized with HIV-BA, but not HIV-1, produced antibodies capable of inhibiting syncytia.

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