Genomic variability of selected LAV-related AIDS retroviruses

Characterization of monoclonal antibodies directed against distinct conserved epitopes of human immunodeficiency virus type 1 core proteins

Two mouse hybridoma cell lines secreting antibodies to the Human Immunodeficiency Virus (HIV) p25 major core protein and its precursors p55 and p41, were developed after immunization with the highly cytopathic Zaïrian HIV-1 isolate, NDK. These monoclonal antibodies also react with the gag gene products from HIV-1-BRU prototype and present cross reaction with HIV-2-ROD, and SIV-AGM. They map into topographically distinct areas of p25 and define epitopic regions topographically separated from those recognized by four other anti-p25 mAb suggesting the existence of at least 6 spatially distinct epitopic regions on HIV-1-p25 core protein.

The env gene variability is not directly related to the high cytopathogenicity of an HIV1 variant

HIV1-NDK is a Zairian HIV1 isolate which is unique because of its high cytopathic effect on T lymphoblastoid cell lines. Its sequence analysis has indicated 30% divergence with HIV1-LAV/BRU HTLVIII B prototype in the env gene encoding for the envelope glycoprotein gp120. In order to correlate the highly cytopathic properties with the env genetic variability, recombinants between the HIV1 prototype and HIV1-NDK have been constructed, including HIV1-NDK env gene, and their cytopathic phenotypes were analyzed. The viral hybrid containing all HIV1 prototype sequences except a large fragment including the total HIV1-NDK env gene remained at a low cytopathic phenotype. Our results suggest that sequences other than the env gene namely p18 gag, vif, and vpr are required for the high virulence of HIV1-NDK.

Isolation and partial characterization of an unusual human immunodeficiency retrovirus from two persons of west-central African origin

An unusual human retrovirus was isolated from two patients with persistent generalized lymphadenopathy who originate from West-Central Africa and are currently residing in Belgium. Although the virus shared a number of the same biological and morphological properties as human immunodeficiency retrovirus type 1 (HIV-1) and HIV-2, significant antigenic differences could be demonstrated. Several of the viral proteins also differed in molecular weight from the corresponding HIV-1 and HIV-2 proteins. Partial chemical cleavage of the most highly conserved viral proteins resulted in patterns which differed from those of HIV-1 and HIV-2. Furthermore, nucleic acid hybridization experiments were capable of discriminating between the virus types. Sequence analysis of the viral U3 region revealed a unique enhancer organization not found in other immunodeficiency viruses. The data indicated that the new isolate is more closely related to HIV-1 than to HIV-2 but clearly differs in a number of important respects.

Biologic and molecular characterization of producer and nonproducer clones from HUT-78 cells infected with a patient HIV isolate

HUT-78 cells were infected with a reverse transcriptase (RT)-positive supernatant of a culture of peripheral blood lymphocytes (PBL) from an AIDS patient and then cloned. Of these clones, two have been isolated and characterized. Clone D10 is persistently and productively infected with an HIV variant. The clone F12, in spite of the presence of an integrated full-length HIV provirus, does not release virus particles in the medium. D10 and F12 clones substantially differ in terms of protein pattern; that is, D10 is super-imposable to infected HUT-78 cells, whereas F12 exhibits a decreased uncleaved p55 gag precursor and the presence of uncleaved gp160 and of a unique p19, although they do not show qualitative or quantitative differences in viral RNA synthesis. Restriction patterns of F12 proviral DNA do not show major genomic deletions. These results indicate that F12 clone cells carry an HIV genome with minor mutations that probably affect the correct production of viral proteins at a posttranscriptional level. In addition, the F12 clone is resistant to high-multiplicity superinfection with HIV-1 or HIV-2.

Biologic features of HIV-1 that correlate with virulence in the host

Individuals infected with the human immunodeficiency virus type 1 (HIV-1) may be asymptomatic or have AIDS-related complex or the acquired immuno deficiency syndrome (AIDS). Little is known about the factors that influence progression of infection to AIDS. In this study of isolates of HIV-1 obtained at intervals during the infection of four individuals, the development of disease was found to be correlated with the emergence of HIV-1 variants that were more cytopathic in vitro as the disease progressed and that replicated more efficiently in a wide variety of different human cells. The biologic properties of HIV-1 in vitro thus appear to reflect its virulence in the host. Further studies of such sequentially isolated viruses may lead to the identification of viral genes that govern pathogenesis.

Recovery of HIV-related retroviruses from Italian patients with AIDS or AIDS-related complex and from asymptomatic at-risk individuals

Human retroviruses have been detected in supernatants of cultures of Ficoll-enriched lymphocytes from peripheral blood, lymph nodes and bone marrow of (a) 32 out of 42 patients with Acquired Immunodeficiency Syndrome (AIDS), (b) 34 out of 64 patients with AIDS-related Complex (ARC), (c) 9 out of 18 asymptomatic children born from Human Immunodeficiency Virus (HIV) seropositive mothers, and (d) 9 out of 28 asymptomatic drug abusers or hemophiliacs. Virus detection was monitored by assaying culture supernatants for the presence of Mg++-dependent reverse transcriptase (R.T.) activity. A number of these virus-positive sups were passaged repeatedly in cultures of phytohemagglutinin-stimulated and Interleukin-2 (IL-2) treated fresh lymphocytes from healthy blood donors. Occasionally, multiple samples were obtained at varying time intervals from the same patient and consistently yielded detectable retroviral activity. Several isolates were characterized as closely related if not identical to HIV, HTLV-IIIB strain, since cells from either patients' own lymphocyte cultures or subcultures infected with passaged virus were stained in an indirect immunofluorescent assay with both patients sera and monoclonal antibody against p24 antigen of the HTLV-IIIB strain. Representative isolates, grown on fresh lymphocytes of healthy donors and metabolically labelled with 35S-cysteine, were also analyzed in a radioimmunoprecipitation assay (RIPA) against patients' sera to define their antigenic pattern, which was widely superimposable to that obtained with HTLV-IIIB-infected H9 cells. DNA from lymphocytes infected with 2 representative isolates were Southern-blotted and probed with an insert from a plasmid containing the entire genome of the HTLV-IIIB strain. The hybridization patterns were comparable with those obtained with DNA from H9-infected cells.

Detection and titration of neutralizing antibodies to HIV using an inhibition of the cytopathic effect of the virus on MT4 cells

An assay for determining neutralizing antibodies in sera from individuals infected with HIV was developed. This assay is based on an inhibition of the cytopathic effect observed after HIV superinfection of the HTLV-1-positive cell-line MT4. Only about 10% of asymptomatic seropositive donors exhibit a high titre over 1/500 up to 1/2000 while in 60% of sera, neutralizing antibodies were not detected. The assay reported here can also be used for the comparison of the biological properties of the different strains of HIV.

Rapid assessment of relationships among HIV isolates by oligopeptide analyses of external envelope glycoproteins

The most variable proteins, the gp120's, of the many isolates of HIV-I can be readily compared by two-dimensional oligopeptide maps. The gp120 in a given cell line is completely stable, but the cell line defines the actual gp120 size and may induce minor peptide changes. HTLV-IIIB and LAV differ slightly from each other even when grown in the same cell line, while LAV grown in a B cell line is less related. Molecularly distant isolates have unique patterns. While anti-HTLV-IIIB gp120 antibody neutralized both HTLV-IIIB and LAV, it recognizes only the homologous HTLV-IIIB infected cells in cytotoxicity assays. Structural analysis of isolates should be helpful in defining the range of immunological reactivities among variants as a contribution to a rational approach to a vaccine against AIDS.

Lentivirus genomic organization: the complete nucleotide sequence of the env gene region of equine infectious anemia virus

The nucleotide sequence of the envelope (env) gene region of equine infectious anemia virus (EIAV), a member of the lentivirus subfamily of retroviruses, has been determined from a clone of integrated proviral DNA for which the gag and pol sequences have been reported previously. The env gene is 859 codons in length and the sequence reported here is consistent with the published biochemical properties of EIAV glycoproteins. The env gene region of EIAV shares considerable structural similarities but negligible sequence homologies with the env genes of other members of the lentivirus subfamily, visna virus, and human T-lymphotropic virus (HTLV-III) or lymphadenopathy virus (LAV). As in visna virus and HTLV-III, the polymerase (pol) and env genes of EIAV do not overlap. EIAV contains two short open reading frames (orf) of 50 and 66 codons in the pol-env intergenic region. However, unlike the orf Q regions reported for visna virus and HTLV-III, neither EIAV orf overlaps the 3' terminus of the adjacent pol gene. The EIAV genome also contains a third short open reading frame of 135 codons which is contained completely within the env gene, in contrast to the 3'-orf/orf F gene reported for HTLV-III/LAV which extends beyond the env gene terminus. These results provide a detailed description of the env gene region of EIAV and describe a number of characteristic features of genomic organization in lentiviruses which contrast with the genomic organization of oncogenic retroviruses.