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PubMed1990

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.

Animals↗
PubMed2001

[Discovery of natural variant strain of HIV1 in env gene C2-V3 encoded PND of membrane protein].

OBJECTIVE: To sequence and analyze the env gene C2-V3 region of proviral genome from a HIV1 isolate(WWBH7) which was obtained from Huadong Area in China. METHODS: The env gene C2-V3 DNA fragment was amplified by nested-primer PCR with genome DNA of eripheral blood mononuclear cells from a confirmed HIV1 infected individual as a template. The amplified DNA fragment was inserted into pGEM-T vector. The recombinant plasmid was confirmed by restriction enzyme analysis. The inserted DNA fragment was sequenced by ABI737 autosequencer and analyzed by PROSIS software. RESULTS: The HIV1 strain was the derivatives of HIV1 B subtype. But there was mutation of 192 bp fragment repeated insertion at env C2-V3 region of the HIV1 strain compared with standard HIV1 B subtype such as SF2 strain. The mutation brought about a double V3 region in gene encoded PND (principal neutralizing domains). The DNA sequence was registered in GenBank (AF220245). CONCLUSIONS: This was a natural mutated variant strain of HIV1 whose genome showed a 192 bp repeated insertion at C2-V3 region of env gene encoded PND of membrane protein.

Amino Acid Sequence↗
PubMed1995

FIV vaccine studies. I. Immune response to recombinant FIV env gene products and outcome after challenge infection.

We have vaccinated five groups of cats (n = 25) four times with five preparations of recombinant feline immunodeficiency virus (FIV) env gene products; one group (n = 7) served as control. The vaccine formulations were as follows: (1) envelope glycoprotein of FIV Zurich 2 (FIV Z2) expressed in a Baculovirus system and isolated by gel electroelution (denatured form); (2) insect cells expressing FIV Z2 glycoprotein; (3) envelope glycoprotein of a Boston strain (FIV Bangston) expressed in insect cells and isolated by gel electroelution (denatured form); (4) glycosylated Bangston envelope protein made in insect cells and isolated in a native form; (5) non-glycosylated Bangston envelope protein made in Escherichia coli. All cats were challenged with 20 50% cat infective doses (CID50) of FIV Z2 previously titrated in cats. All vaccinated cats developed high enzyme-linked immunosorbent assay (ELISA) antibodies to the homologous antigen; crossreactivity to heterologous antigens was seen at a lower level. Virus neutralizing antibodies (tested with Petaluma virus) reached titers up to 32. After challenge, all cats seroconverted (as judged by anti gag antibodies in Western blot) and became infected (as judged by virus isolation and/or polymerase chain reaction) between 4 and 11 weeks with the exception of one cat. It is concluded that it is relatively easy to induce high ELISA antibody titers using recombinant env gene products, ELISA antibody titers do not correlate with virus neutralization or with protection.

Animals↗
PubMed1996

Characterization of the functional properties of env genes from long-term survivors of human immunodeficiency virus type 1 infection.

A small number of persons infected with human immunodeficiency virus type 1 (HIV-1) remain clinically and immunologically healthy for more than a decade after infection. Recent reports suggest that these individuals may be infected with an attenuated strain of HIV-1; however, a common genetic basis for viral attenuation has not been found in all cases. In the present study, we examined the functional properties of the HIV-1 env genes from six long-term survivors. env clones were generated by PCR amplification of proviral env sequences, followed by cloning of the amplified regions into expression vectors. Eight to ten clones from each subject were screened by transient transfection for expression of the envelope precursor glycoprotein, gp160. Those clones expressing gp160 were then cotransfected with an HIV-1 luciferase reporter vector, pNL4-3Env(-)LUC(+) and evaluated for their ability to mediate infection of phytohemagglutinin-activated peripheral blood mononuclear cells in single-cycle infectivity assays. Clones expressing gp160 were identified for all six long-term survivors, indicating the presence of proviral env genes with intact open reading frames. For two subjects, D and DH, the encoded envelope glycoproteins yielded high levels of luciferase activity when pseudotyped onto HIV-1 virions and tested in single-cycle infectivity assays. In contrast, envelope glycoproteins cloned from four other long-term survivors were poorly processed and failed to mediate infection. Sequencing of the gp120/41 cleavage site and conserved gp41 cysteine residues of these clones did not reveal any obvious mutations to explain the functional defects. The functional activity of env clones from long-term survivors D and DH was comparable to that seen with several primary HIV-1 env genes cloned from individuals with disease progression and AIDS. These results suggest that the long-term survival of subjects D and DH is not associated with overt functional defects in env; however, functional abnormalities in env may contribute to maintaining a long-term asymptomatic state in the other four cases we studied.

Cohort Studies↗
PubMed2002

Genotypic and phenotypic analysis of the env gene from South African HIV-1 subtype B and C isolates.

The objective of the study was to assess the genotypic and phenotypic properties of 18 viral strains from human immunodeficiency virus-1 (HIV-1) positive patients and to identify subtype C isolates for vaccine design strategies. All the isolates were non-syncytium-inducing (NSI) in both the primary and MT-2 cell cultures. The amino acid charge of the V3 loop correlated with the NSI phenotype of the strains. The V3 competitive peptide enzyme immunoassay and DNA sequencing of the partial gp120 region gave concordant results on the 15 subtype C strains, whereas the three B genotypes gave a positive to B, a nonreactive to B, and a dual reaction to the B-D peptides, respectively. Sixteen of the isolates used only CCR5 as coreceptor whereas two isolates made use of additional coreceptors including CXCR4. In summary, all our subtype C isolates are NSI phenotypically and almost all of them use CCR5 exclusively as their coreceptor.

Amino Acid Sequence↗
PubMed2000

Generation of intersubtype human immunodeficiency virus type 1 recombinants in env gene in vitro: influences in the biological behavior and in the establishment of productive infections.

The occurrence of human immunodeficiency virus type 1 (HIV-1) recombinant genomes belonging to different subtypes is a common event in regions where more than two subtypes cocirculate. Although there are accumulating data toward an increase in the number of intersubtype recombinants, little has been addressed about the biological behavior of such mosaic genomes. This work reports the biological characterization of engineered in vitro HIV-1 intersubtype recombinants in the gp120 region. The recombinants possess the entire gp120 of B or F Brazilian isolates in the Z6 (subtype D) backbone. Here we show that this type of recombinant structure results in profound impairment to the establishment of productive infections in CD4-positive cells. The characterization of biological properties of those recombinant viruses demonstrated viral production occurring only during a transient peak early on infection and that they are not able to down-regulate the expression of CD4 receptor on the cell surface. We also report the phenotype reversion of one recombinant virus studied here, after 62 days in culture. Two amino acid substitutions in highly constant gp120 regions (C1 and C4) were identified in the revertant virus. The mutation occurring in the C4 region is localized near two amino acid residues critical for gp120/CD4 interaction. Based on these data, we suggest that failure in CD4 down-modulation by recombinant viruses can be due to a structural dysfunction of gp160 protein unable to block CD4 at the endoplasmic reticule. The possibilities that the establishment of latent infections can be directly related to the continuous expression of CD4 on the infected cell surface and that the occurrence of mutations in amino acid nearby residues critical for gp120/CD4 interaction can restore the fully productive infectious process are discussed.

Amino Acid Sequence↗
PubMed1996

Single-tube heminested PCR coupled with 'touchdown' PCR for the analysis of the walleye dermal sarcoma virus env gene.

The nucleotide sequences of geographically distant isolates of a newly characterized retrovirus of fish, the walleye dermal sarcoma virus (WDSV) were compared. Primers were designed based on the nucleotide sequence of a single molecular clone isolated from a tumor collected from a fish in New York state, USA. Conventional polymerase chain reaction (PCR) did not allow the satisfactory amplification of WDSV isolates from a different geographic region (Quebec, Canada), probably owing to the high genetic variability of retroviruses. To allow the successful amplification of Quebec WDSV isolates, heminested PCR and 'touchdown' PCR were combined in a highly sensitive, short and simple protocol taking place in a single tube, thus minimizing cross contamination. This technique allowed the first unambiguous detection of a fish retrovirus in Canada and the phylogenetic analysis of various geographic isolates of this virus. Other potential applications for this technique include PCR amplification using degenerate primers, and amplification of templates with some expected degree of genetic variability.

Animals↗
PubMed1995

A natural antisense RNA derived from the HIV-1 env gene encodes a protein which is recognized by circulating antibodies of HIV+ individuals.

A naturally occurring antisense RNA, transcribed in the opposite direction and complementary to the envelope transcript, was identified in various cell lines chronically infected with HIV-1. In T cells, the antisense transcript is constitutively expressed and enhanced by activation with phorbol myristate acetate. The open reading frame corresponding to the antisense transcript, when expressed in vitro, encodes a protein with an apparent molecular mass of 19 kDa. Antibodies against this protein have been detected in several sera of HIV+ individuals and not in any of the noninfected control sera. These results indicate, for the first time, that expression of an antisense open reading frame most likely accompanies the HIV infection cycle in humans.

Base Sequence↗
PubMed2004

Elevated expression of the tumor suppressing protein p53 is associated with the presence of mouse mammary tumor-like env gene sequences (MMTV-like) in human breast cancer.

Mouse mammary tumor virus (MMTV) has a proven role in breast carcinogenesis in wild mice and genetically susceptible laboratory inbred mice. The carcinogenic characteristics of this virus are enhanced by estrogen and other steroid hormones. MMTV-like envelope gene sequences, with 95% homology to MMTV have been identified in approximately 40% of breast cancers in US, Australian and Argentinian women. The presence of such sequences indicates the presence of a replication competent MMTV-like virus in human breast tumors. Whether an MMTV-like virus contributes to human breast cancer remains to be demonstrated. Non-statistically significant differences in p53 expression between MMTV-like positive and negative human breast cancers have previously been observed. As high p53 protein expression is associated with aggressive breast carcinogenesis we sought to determine if there were associations between the presence of MMTV-like gene sequences and elevated p53 expression in both invasive ductal carcinomas (IDC) and ductal carcinomas in situ (DCIS). We also investigated the expression of other biomarkers which are commonly associated with human breast cancer. These included estrogen receptor, progesterone receptor, Ki67, Cyclin D1, Bcl-2 and HER-2. Using polymerase chain reaction (PCR) analyses, MMTV-like envelope gene sequences were detected in 15 (75%) of 20 IDC specimens and 5 (23%) of 22 DCIS specimens. The average percentage of p53 positive cells in MMTV-like positive IDC specimens was 69% as compared to 44% in MMTV-like negative specimens (p for difference = 0.067). The average percentage of p53 positive cells in MMTV-like positive DCIS specimens was 93% as compared to 35% in MMTV-like negative specimens (numbers too few for statistical analysis). There was an increased intensity of p53 expression in IDC and DCIS specimens that were MMTV-like positive compared to those that were MMTV-like negative. There were no statistically significant differences in age, grade, and percentage of average positive cells for ERa, PR, Ki67, cyclin D1, Bcl-2, and HER-2, between MMTV-like positive and negative breast cancer specimens. Although these observations do not provide evidence of causality, they are consistent with a role for MMTV-like viruses in some human breast cancers.

Animals↗
PubMed1993

Sequence analysis of the gp120 region of the env gene of Ugandan human immunodeficiency proviruses from a single individual.

DNA sequences encoding the surface glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1) were amplified by the polymerase chain reaction (PCR) from peripheral blood mononuclear cells obtained from a Ugandan AIDS patient. The PCR-amplified DNA was cloned into a phagemid vector and nine clones sequenced. The gp120 sequences of the proviruses were similar to that of the Zairian isolate HIV-JY1 and unlike that of another Ugandan provirus, U455. Six of the clones were closely related to each other (maximum nucleotide sequence divergence 1.9%), and had a V3 amino acid sequence similar to that frequently seen in recent isolates from Uganda. Two others formed a second group that diverged from the first by an average of 6.0% at the nucleotide level, resulting in a 12.5% divergence of amino acid sequence. These divergent clones had extensive amino acid sequence changes not only in the V3 region, which was highly atypical, but also in V1 and V4, and to a lesser extent in V2 and V5. A further proviral clone had a sequence intermediate between those of the other two groups of clones.

Acquired Immunodeficiency Syndrome↗