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R V Srinivas

Publications and source records attributed to R V Srinivas.

At least 37 records · Page 2Linked to original sources
PubMed1995

Metabolic diversity and antiviral activities of acyclic nucleoside phosphonates.

The acyclic nucleoside phosphonates (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) inhibited herpes simplex virus-1 replication in Vero cells, and the IC50 values ranged from 4 microM (for HPMPC and HPMPA) to 40 microM (for PMEA). Pretreatment of cells with HPMPC for 12-24 hr induced an effective antiviral state, and the cells maintained this antiviral state for > 7 days. In contrast, much larger amounts (approximately 2.5-5 x IC50 doses) of PMEA or HPMPA were required to establish an antiviral state, which lasted for only approximately 24 or 72 hr, respectively. A 12-hr treatment of the cells with the phosphonates was required for the establishment of optimal antiviral activity; surprisingly, longer durations of exposure to PMEA (but not HPMPA or HPMPC) resulted in diminished antiviral effect. We investigated the metabolism of PMEA and HPMPC to determine the cellular basis for these differences. The cellular uptake of HPMPC was approximately 8-fold greater than that of PMEA. The levels of the PMEA metabolites PMEA monophosphate and PMEA diphosphate increased for approximately 12 hr and plateaued thereafter. PMEA and its metabolites were cleared from the cells with a half-life of 4.9 hr. In contrast, the HPMPC metabolites HPMPC monophosphate (HPMPCp) and HPMPC diphosphate (HPMPCpp) accumulated throughout the 24-hr study period and, at equimolar drug concentrations (25 microM), reached intracellular levels approximately 2-3-fold greater than those of the PMEA metabolites. HPMPC also differed from PMEA in its capacity to generate a phosphodiester metabolite (HMPCp-choline), which was a predominant metabolite in HPMPC-treated cells. In addition, the rates of disappearance of intracellular metabolites of the two drugs were significantly different. Thus, the decay of HPMPCpp was quite slow and biphasic (t1/2 = 24 and 65 hr) and that of HMPCp-choline was monophasic (t1/2 = 87 hr). Together, these factors can explain the differing antiviral potencies seen with PMEA and HPMPC. The possible role of the choline adduct in the expression of antiviral activity of the drug remains to be elucidated, but the adduct may serve as an intracellular store for the long term maintenance of active HPMPCpp in cells. The results also highlight the extent of diversity in the cellular pharmacology and antiviral activities of the acyclic nucleoside phosphonates.

Adenine↗
PubMed1995

A human T lymphoid cell variant resistant to the acyclic nucleoside phosphonate 9-(2-phosphonylmethoxyethyl)adenine shows a unique combination of a phosphorylation defect and increased efflux of the agent.

9-(2-Phosphonylmethoxyethyl)adenine (PMEA) is a new antiviral agent with activity against herpes viruses and retroviruses, including human immunodeficiency virus, but its metabolism and mechanism of action remain unclear. We have isolated a human T lymphoid cell line (CEMr-1) that is resistant to the antiproliferative effects of PMEA. The antiviral effects of PMEA against human immunodeficiency virus-1 infection were also greatly reduced in CEMr-1 cells, compared with the parental cells. This mutant showed cross-resistance to the related acyclic nucleoside phosphonates 9-(2-phosphonylmethoxyethyl)diaminopurine and 9-(2-phosphonylmethoxyethyl)guanine and the lipophilic prodrug bis(pivaloyloxymethyl)-9-(2-phosphonylmethoxyethyl)adenine-( bispome-PMEA), as well as partial resistance to the purine nucleosides 2-chlorodeoxyadenosine, 2-fluro-9-beta-D-arabinosylfuranosyladenine, and adenosine, but did not show resistance to 2'-deoxyadenosine or 9-beta-D-arabinosylfuranosyladenine. We compared the uptake and metabolism of [3H]PMEA and [3H]-bispom-PMEA in the mutant and parental cells. The analysis of radioactive products by high pressure liquid chromatography revealed marked alterations in the ability of the mutant cell line to accumulate PMEA and its anabolites, compared with the parental cells. Accumulation of PMEA, PMEA monophosphate, and PMEA bisphosphate (major metabolites formed with either PMEA or bispom-PMEA) decreased by 50, 95, and 97%, respectively. Compared with the parental cells, the variant cells showed a approximately 7-fold increase in the rate of efflux of PMEA and a 2-fold decrease in the activity of adenylate kinase. In contrast, other enzymes of nucleotide metabolism, such as adenosine kinase, deoxycytidine kinase, and 5-phosphoribosyl-1-pyrophosphate synthetase, showed no significant change in the two cell lines. Overall, these results suggest that the mutation in this resistant cell line is of a novel type, involving an alteration in the cellular efflux of PMEA as the major basis for the resistant phenotype.

Adenine↗
PubMed1994

Calmodulin antagonists inhibit human immunodeficiency virus-induced cell fusion but not virus replication.

We have reported that amphipathic helical segments in the cytoplasmic domain of the HIV-1 envelope glycoproteins bind to calmodulin (CaM) with high affinity, and inhibit calmodulin-regulated proteins. To investigate the possible role of calmodulin activity in HIV-1 replication, we investigated the anti-HIV activity of various CaM antagonists--trifluoperazine and naphthalenesulfonamide W13 or W7--in HeLa T4 cells, PBMCs, and various T lymphocytic cell lines. The different CaM antagonists were found to inhibit the proliferation of the different cell types to varying extent. Also, the CaM antagonists were found to exert a greater antiproliferative effect on H9/HIV-1IIIB, as compared to uninfected H9 cells, suggesting a deficit of CaM function in HIV-infected cells. The CaM antagonists inhibited virus-induced cell fusion in HeLa T4 cells infected with a recombinant vaccinia virus expressing HIV-1 envelope proteins at threshold concentrations that do not inhibit cell proliferation. The fusion-inhibitory effects of the CaM antagonists were also observed in cocultures of HIV-infected (H9/HIV-1IIIB) and uninfected H9 cells. Under these conditions, the synthesis and surface expression of the viral glycoproteins were not affected, although the kinetics of processing of HIV envelope precursor was delayed. Virus production from both HIV-infected peripheral blood mononuclear cell (PBMC) and MT-2 cell cultures was inhibited by CaM antagonists at concentrations that were inhibitory to cell proliferation. Surprisingly, threshold concentrations of CaM antagonists that do not inhibit cell proliferation were found to enhance virus production from HIV-infected MT-2 cells, but not PBMCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Calmodulin↗
PubMed1994

Enzymatic assay for measurement of zidovudine triphosphate in peripheral blood mononuclear cells.

In this report, we describe a new method to measure intracellular zidovudine triphosphate (ZDV-TP) levels in peripheral blood mononuclear cells (PBMCs) from patients treated with ZDV by utilizing inhibition of human immunodeficiency virus type 1 reverse transcriptase activity by ZDV-TP. Intracellular levels of ZDV-TP were determined with our enzymatic assay in PBMCs isolated from the blood of healthy individuals incubated with different concentrations of labeled ZDV and were validated by high-performance liquid chromatography separation and liquid scintillation counting of the radioactive ZDV-TP. These methods gave virtually identical results over a range of ZDV-TP concentrations from 150 to 900 fmol. ZDV-TP recoveries were over 90%, and the limit of quantitation of ZDV-TP by this method was 20 to 50 fmol. To demonstrate the utility of the method, plasma ZDV and intracellular ZDV-TP concentrations were measured at serial time points over 6 h in 12 human immunodeficiency virus-infected volunteers following a single 100- or 500-mg oral dose of ZDV. Systemic oral clearance rates were similar to those in previous studies with adults but were highly variable (range, 0.86 to 2.75 liters/h/kg of body weight). The area under the plasma concentration versus time curve increased significantly (P < 0.0005) with the dose from a median value of 1.2 mg.h/liter at the lower dose to 4.2 mg.h/liter at the higher dose. Median intracellular ZDV-TP levels ranged from 5 to 57 and 42 to 92 fmol/10(6) cells in volunteers administered 100 and 500 mg of ZDV, respectively. Intracellular ZDV-TP levels rose to a plateau value by 2 h and remained consistent to 6 h. Although the higher dose and higher areas under the curve yielded consistently higher intracellular ZDV-TP levels, systemic pharmacokinetics explains only a modest proportion of the variability in cellular pharmacokinetic. The ZDV-TP bioassay should prove useful in further studies of ZDV metabolism in patient-derived PBMCs at the doses of ZDV currently administered.

Antiviral Agents↗
PubMed1994

Susceptibilities of zidovudine-resistant variants of human immunodeficiency virus type 1 to inhibition by acyclic nucleoside phosphonates.

The acyclic purine nucleoside phosphonates, a newly described class of broad-spectrum antiviral agents, effectively inhibit human immunodeficiency virus type 1 (HIV-1) replication in vitro and in animal AIDS models. 9-(2-Phosphonylmethoxyethyl)adenine (PMEA) is currently being evaluated in clinical trials in patients with AIDS. In this study, we investigated the efficacy of PMEA and a related analog, 9-(2-phosphonylmethoxypropyl)diaminopurine (PMPDAP), against HIV-1 isolates exhibiting various degrees of resistance to zidovudine (azidothymidine [AZT]). HIV isolates highly (approximately 50 to 200-fold) resistant to AZT were found to be about two- to eightfold less susceptible to PMEA. A comparable degree of cross-resistance to PMPDAP, a structurally related analog of PMEA, was also observed. However, the 50% effective dose values of PMEA or PMPDAP against a panel of HIV isolates showing intermediate levels (approximately 8 to 25-fold) of AZT resistance was indistinguishable from the 50% effective dose values of PMEA (0.7 to 1.7 versus 2 microM) or PMPDAP (0.4 to 1.4 versus 0.8 to 1 microM) against HIV isolates from patients who had not previously used AZT. In addition, we were unable to generate PMEA- (or PMPDAP)-resistant HIV-1 variants by > 30 serial passages of the virus in the presence of increasing concentrations of PMEA. Careful analysis of HIV-1 isolates from patients previously treated with AZT for cross-resistance to PMEA are needed to evaluate the significance of these observations.

Adenine↗
PubMed1993

Cytosolic domain of the human immunodeficiency virus envelope glycoproteins binds to calmodulin and inhibits calmodulin-regulated proteins.

Calmodulin (CaM), the major intracellular receptor for calcium, is involved in regulation of diverse cellular functions. Positively charged amphipathic helical segments have been identified as an important structural motif in the recognition of CaM by different CaM-activated enzymes and peptides. The carboxyl-terminal domain of the envelope glycoproteins of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV) contain regions that can fold into amphipathic helical segments, which closely resemble the amphipathic segments found in CaM-activated enzymes. We show here that synthetic peptide analogs corresponding to the two putative amphipathic helical regions of HIV-1/WMJ gp160 bind to CaM with high affinity (Kd 31-41 nM) in the presence of calcium. They also bind CaM in the absence of calcium, although with much lower affinity. The peptides inhibit CaM-regulated activation of bovine brain phosphodiesterase in vitro. The peptides also inhibit mitogen-induced lymphocyte activation, a property shared by CaM antagonists. Purified HIV-1 gp160 binds to CaM, while gp120, which lacks the putative amphipathic helical segments, does not bind CaM. In HIV-infected cells, the putative CaM-binding regions of gp160 are located intracellularly and may therefore interact with the cytosolic CaM. We postulate that CaM binding by HIV envelope proteins is likely to exert diverse modulatory effects, and the mechanism for HIV-induced cytotoxicity may involve, in part, inhibition of CaM-regulated cellular functions.

Amino Acid Sequence↗
PubMed1993

Metabolism and in vitro antiretroviral activities of bis(pivaloyloxymethyl) prodrugs of acyclic nucleoside phosphonates.

Bis(pivaloyloxymethyl) [bis(pom)] derivatives of various acyclic nucleoside phosphonates--9-(2-phosphonylmethoxyethyl)adenine (PMEA), 9-(2-phosphonylmethoxypropyl)adenine (PMPA), and 9-(2-phosphonylmethoxypropyl)diaminopurine (PMPDAP)--were found to exhibit 9- to 23-fold greater antiviral activity than their corresponding unmodified compounds. The cytotoxicity of the bis(pom) analogs was also increased by various degrees, thus altering the therapeutic indexes of these compounds. Metabolic studies using [3H]bis(pom)PMEA and [3H]PMEA as model compounds suggested a > 100-fold increase in the cellular uptake of the bis(pom) derivative and formation of active diphosphorylated metabolite. However, the bis(pom) derivatives were chemically unstable and highly susceptible to serum-mediated hydrolysis, factors which limit their potential utility for intracellular drug delivery.

Adenine↗
PubMed1993

5-Amino-4-imidazolecarboxamide riboside potentiates the metabolism and anti-human immunodeficiency virus activity of 2',3'-dideoxyinosine.

The antiviral activity of the purine dideoxynucleosides 2',3'-dideoxyadenosine (ddA) and 2',3'-dideoxyinosine (ddI) is dependent on their conversion into ddA triphosphate in vivo. 5-Amino-4-imidazolecarboxamide riboside (AICA riboside), a natural metabolite in purine biosynthetic pathways, is converted into IMP, a substrate for the biosynthesis of adenine and guanine nucleotides, and enhances the intracellular purine nucleotide pools. Because IMP also serves as a phosphate donor in the anabolic phosphorylation of ddI (and ddA) into ddI monophosphate by the cytosolic enzyme 5'-nucleotidase, we investigated the effects of AICA riboside on the phosphorylation and antiretroviral activity of these purine nucleoside analogs. At an AICA riboside concentration of 0.5 mM, there was a approximately 2-fold increase in the intracellular ATP and GTP levels, whereas a nearly 8-fold increase was observed for the phosphorylation of ddA (or ddI). A marked reduction in intracellular pools of the pyrimidine nucleotides CTP and UTP was observed in AICA riboside-treated cells and inhibited cell proliferation. However, this growth inhibition was prevented by the addition of uridine to the cultures. Cells pretreated with AICA riboside and ddI were less susceptible to human immunodeficiency virus (HIV) infection and synthesized reduced levels of HIV proviral DNA. A 10-fold potentiation of the effectiveness of ddI against both wild-type HIV (HIVIIIB) and a ddI-resistant variant HIV was observed in the presence of 0.5 mM AICA riboside. These results show that AICA riboside modulates the anabolism and antiviral activity of ddI, and they have implications for possible therapies with dideoxynucleosides.

Aminoimidazole Carboxamide↗
PubMed1992

Membrane interactions of synthetic peptides corresponding to amphipathic helical segments of the human immunodeficiency virus type-1 envelope glycoprotein.

The human and simian immunodeficiency virus envelope glycoproteins, which mediate virus-induced cell fusion, contain two putative amphipathic helical segments with large helical hydrophobic moments near their carboxyl-terminal ends. In an attempt to elucidate the biological role of these amphipathic helical segments, we have synthesized peptides corresponding to residues 768-788 and 826-854 of HIV-1/WMJ-22 gp160. Circular dichroism studies of the peptides showed that the alpha helicity of the peptides increased with the addition of dimyristoyl phosphatidylcholine (DMPC) indicating that the peptides form lipid-associating amphipathic helixes. The peptides solubilized turbid suspensions of DMPC vesicles, and electron microscopy of peptide-DMPC mixtures revealed the formation of discoidal complexes, suggesting that the peptides bind to and perturb lipid bilayers. The peptides were found to lyse lipid vesicles and caused carboxyfluorescein leakage from dye-entrapped egg phosphatidylcholine liposomes. The peptides also lysed human erythrocytes and were found to be toxic to cell cultures. At subtoxic concentrations, the peptides effectively inhibited the fusion of CD4+ cells infected with recombinant vaccinia virus expressing human immunodeficiency virus (HIV)-1 envelope proteins. Based on these results, and reported studies on the mutational analysis of HIV envelope proteins, we suggest that the amphipathic helical segments near the carboxyl terminus of HIV envelope proteins may play a role in lysis of HIV-infected cells and also may modulate the extent of cell fusion observed during HIV infection of CD4+ cells.

Amino Acid Sequence↗
PubMed1992

A 585-bp deletion found in the spleen focus-forming virus (SFFV) env gene is responsible for the defective intracellular transport of SFFV gp52.

The Friend spleen focus-forming virus (F-SFFV) codes for a transport defective, leukemogenic envelope glycoprotein designated as gp52. Gp52 closely resembles the envelope glycoproteins (gp70-p15E) encoded by the mink cell focus-forming viruses (MCFV). The major differences between SFFV and MCFV include a 585-bp deletion and a frame-shift mutation near the 3' end of the SFFV env gene. We have constructed a mutant MCFV env gene, which contains a 585-bp deletion like that found in the SFFV env gene, and expressed this gene using recombinant vaccinia vectors or retroviral vectors. The mutant MCFV env gene expressed a truncated, transport defective glycoprotein (gp57). Only a small proportion of gp57 underwent further oligosaccharide processing. Intracellular gp57 remained predominantly monomeric and only a small proportion of gp57 (and its processed forms) formed disulfide-linked dimers and trimers which resembled those formed by SFFV gp52. Processed forms of gp57 were found on the cell surfaces and in culture fluids. The extracellular forms had a faster electrophoretic mobility than the intracellular-processed forms of gp57. These results indicate that the 585-bp deletion found in SFFV env gene is responsible for the folding, transport, and secretion of gp52. Retroviral vectors carrying the mutant MCFV env gene were nonpathogenic (or weakly pathogenic) in adult mice. The results indicate that the 585-bp deletion, although essential, is not the sole determinant of SFFV-induced disease in adult mice.

3T3 Cells↗
PubMed1992

A carboxy-terminal mutant spleen focus-forming virus (SFFV) envelope glycoprotein is transport-competent, but non-leukemogenic.

The Friend spleen focus-forming virus (F-SFFV) codes for a transport-defective leukemogenic envelope glycoprotein designated as gp52. We have previously shown that the external domain of gp52 carries the determinants responsible for its transport defect. Consistent with this idea, truncated gp52 molecules that lack a hydrophobic membrane anchor were transport-defective, and were not secreted from cells. In this report, we describe the construction of a mutant SFFV envelope gene that codes for altered gp52 molecules in which the carboxyl-terminal hydrophobic residues are replaced with exogenous hydrophilic residues encoded by the vector-derived sequences. The mutant env gene was expressed using the retroviral expression vector, pLXSN, and the mutant envelope protein was found to be transport-competent, and efficiently secreted from the cells. However, M-MuLV pseudotypes of the retroviral vectors expressing the mutant genome were found to be non-leukemogenic in mice.

3T3 Cells↗
PubMed1991

Inhibition of virus-induced cell fusion by apolipoprotein A-I and its amphipathic peptide analogs.

Apolipoprotein A-I (apoA-I), the major protein component of serum high-density lipoproteins (HDL), was found to inhibit herpes simplex virus (HSV)-induced cell fusion at physiological (approximately 1 microM) concentrations, whereas HDL did not exert any inhibitory effect. Lipid-associating, synthetic amphipathic peptides corresponding to residues 1-33 (apoA-I[1-33]) or residues 66-120 (apoA-I[66-120]) of apoA-I, also inhibited HSV-induced cell fusion, whereas a peptide corresponding to residues 8-33 of apoA-I (apoA-I[8-33]), which fails to associate with lipids, did not exert any inhibitory effect. These results suggest that lipid binding may be a prerequisite for peptide-mediated fusion inhibition. Consistent with this idea, a series of lipid-binding 22-amino-acid-residue-long synthetic amphipathic peptides that correspond to the amphipathic helical domains of apoA-I (A-I consensus series), or 18-residue-long model amphipathic peptides (18A series), were found to exert variable levels of fusion-inhibitory activity. The extent of fusion-inhibitory activity did not correlate with hydrophobic moment, hydrophobicity of the nonpolar face, helix-forming ability, or lipid affinity of the different peptides. Peptides in which the nonpolar face was not interrupted by a charged residue displayed greater fusion-inhibitory activity. Also, the presence of positively charged residues at the polar-nonpolar interface was found to correlate with higher fusion-inhibitory activity.

Amino Acid Sequence↗
PubMed1991

Molecular domains involved in oligomerization of the Friend murine leukemia virus envelope glycoprotein.

The oligomeric structure of the Friend murine leukemia virus envelope glycoprotein has been investigated using crosslinking reagents and sucrose density gradient centrifugation. The results obtained provide evidence that both the precursor and the processed molecules are oligomeric and probably form tetramers. Pulse-chase analyses indicate that assembly occurs sequentially, within 30 min of protein synthesis and prior to cleavage of the precursor. Studies using chimeric envelope glycoproteins and deletion mutants indicate that the transmembrane and cytoplasmic domains are not essential for the formation of oligomers. Evidence is also presented that the SU subunit remains in an oligomeric form following disassociation from the TM subunit. Oligomeric envelope glycoprotein complexes linked by intermolecular disulfide bonds were also observed under certain conditions. Mink cell focus-forming virus envelope glycoprotein constructs lacking the transmembrane domain or both the transmembrane and the cytoplasmic domains formed intermolecular disulfide bonds more readily than the full-length molecule, suggesting that these regions are likely to make a contribution to the conformation of the glycoprotein. These data indicate that there are several points of interaction between retrovirus envelope glycoprotein monomers which contribute to assembly of the oligomer and that contacts within the ectodomain appear to be of critical importance.

Amino Acid Sequence↗
PubMed1991

The hydrophobic membrane-spanning sequences of the gp52 glycoprotein are required for the pathogenicity of Friend spleen focus-forming virus.

Friend spleen focus-forming virus (SFFV) codes for a transport-defective envelope glycoprotein designated gp52, which is responsible for the leukemogenic properties of the virus. gp52 is a monotopic integral membrane protein anchored in the membrane by a stretch of hydrophobic amino acid residues located near the carboxy terminus of the molecule. We have constructed a mutant SFFV envelope gene in which the sequences that code for the hydrophobic membrane-spanning domain have been deleted, and we expressed this gene by using recombinant vaccinia virus vectors or retroviral vectors. The mutant SFFV envelope gene was found to encode a truncated glycoprotein (gp52t) which was also transport defective; a majority of gp52t remained cell associated, while a small proportion of the molecules underwent oligosaccharide processing. The processed form of gp52t was secreted from the cells. Retroviral vectors carrying the mutant SFFV envelope gene were found to be nonpathogenic in adult mice. These results indicate that the hydrophobic membrane-spanning region of gp52 is required for pathogenicity of SFFV and suggest that these sequences may play a role in signal transduction. The results also indicate that the transport defect of SFFV gp52 is due to structural features of the ectodomain of the molecule.

Amino Acid Sequence↗
PubMed1990

Antiviral effects of apolipoprotein A-I and its synthetic amphipathic peptide analogs.

Apolipoprotein A-I (apo A-I), the major protein component of serum high density lipoproteins, was found to inhibit herpes simplex virus (HSV)-induced cell fusion at physiological (approximately 1 microM) concentrations. An 18 amino acid-long synthetic amphipathic alpha-helical peptide analog of apo A-I (18A) was also found to inhibit HSV-induced cell fusion at similar concentration (approximately 2 microM). Dimers of 18A connected via a proline (37pA) or an alanine (37aA) residue also inhibited virus-induced cell fusion at similar concentration, suggesting that the presence of a proline turn does not influence the antiviral activity of the amphipathic peptides. However, a peptide analog 18R, in which the distribution of charged residues was reversed, inhibited virus-induced cell fusion only at a higher (approximately 125 microM) concentration, suggesting that the anti-viral activity of the amphipathic peptide is strongly influenced by the nature of the charge distribution at the polar-nonpolar interface. Consistent with their ability to inhibit virus-induced cell fusion, the peptides inhibited the spread of HSV infection as demonstrated by a 10-fold reduction in the virus yield, when virus-infected cells were maintained in the presence of amphipathic peptides. The amphipathic peptides also inhibited penetration of virus into cells, but did not exert any effect on virus adsorption. A nearly complete inhibition of virus penetration was observed when the virus, or both virus and cells, was pretreated with the peptide, suggesting that the peptides may have a direct effect on the virus. The results indicate that amphipathic helices may be useful in designing novel antiviral agents that inhibit penetration and spread of enveloped viruses.

Amino Acid Sequence↗
PubMed1990

Oligopeptide inhibitors of HIV-induced syncytium formation.

The human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is essential for virus entry and the formation of multinucleated giant cells by cell fusion, one of the major virus-induced cytopathic effects. To study the effects of potential fusion inhibitors, a vaccinia virus recombinant expressing the envelope glycoprotein was generated and used to infect HeLa CD4+ cells. Syncytium induction was observed as early as 4 h postinfection and continued until the entire monolayer was fused. The N-terminus of the gp41 subunit of the HIV envelope protein is very hydrophobic, and appears to be involved in virus-induced membrane fusion. We synthesized several oligopeptide analogs of the N-terminal region of gp41 and determined their ability to inhibit HIV-induced cell fusion in CD4+ HeLa cells. A hexapeptide which was identical in amino acid sequence to the N-terminus of gp41 was found to completely inhibit cell fusion, whereas peptides with altered sequences showed reduced inhibitory activity. These peptides had no effect on protein synthesis, processing, or transport to the cell surface, and showed no signs of toxicity to cells even at very high concentrations. These results indicate that oligopeptides which are homologous to the fusion peptide of HIV inhibit virus-induced cytopathology, and should be evaluated further as potential antiviral agents.

Amino Acid Sequence↗