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Biomedical subjects

H Salomon

Publications and source records attributed to H Salomon.

At least 37 records · Page 2Linked to original sources
PubMed1996

The nucleoside analog-resistant E89G mutant of human immunodeficiency virus type 1 reverse transcriptase displays a broader cross-resistance that extends to nonnucleoside inhibitors.

The alteration of a glutamic acid (E) to a glycine (G) amino acid residue at position 89 (E89G alteration) in the human immunodeficiency virus type 1 reverse transcriptase confers decreased susceptibility to several nucleoside analog inhibitors. Because the nonnucleoside inhibitor-binding pocket is adjacent to the deoxynucleoside triphosphate substrate-binding site, the impact of the E89G reverse transcriptase has decreased susceptibility to TIBO R82150, nevirapine, and to a lesser extent, delavirdine. Human immunodeficiency viruses bearing the same mutation displayed decreased susceptibility to inhibition by these compounds in a cell culture virus replication assay.

Anti-HIV Agents↗
PubMed1996

Resistance to (-)-2',3'-dideoxy-3'-thiacytidine (3TC) in HIV-1 isolated from paediatric patients.

We conducted detailed virological evaluations of 16 HIV-1-infected paediatric patients treated with 3TC (lamivudine) monotherapy. High-level phenotypic resistance against this compound (up to 2,500-fold) was seen in virtually all cases, usually within 8-12 weeks of initiation of therapy. This was concomitant with the appearance of the M184V mutation in viral reverse transcriptase, previously shown to be responsiblefor such resistance. Viral burden fell in virtually all cases after commencement of therapy, and remained below baseline in each instance studied, despite a rebound effect and the appearance of drug resistance. Viral isolates from some patients underwent a switch from a non-syncytium-inducing (NSI) to a syncytium-inducing (SI) phenotype during the course of the study, although no relationship was apparent between dose of drug employed, time to development of drug resistance or time of appearance of SI phenotype.

Anti-HIV Agents↗
PubMed1995

Antiviral activity and protection of cells against human immunodeficiency virus type-1 using an antisense oligodeoxyribonucleotide phosphorothioate complementary to the 5'-LTR region of the viral genome.

A COS-like monkey kidney cell line stably transfected with the plasmids pCMVgagpol-rre-r with the gag and pol genes, and pCMV rev with the rev gene of HIV-1 derived from the cDNA clone BH10, was used as a model for assessing the effectiveness of antisense (AS) constructs, A 20-mer oligodeoxyribonucleotide (oligo) phosphorothioate sequence (5'-CCG CCC CTC GCC TCT TGC CG) complementary to a portion of the 5'-long terminal repeat (5'-LTR) of the HIV-1 genome was tested for its inhibitory effects on the biologically important processes of HIV-1 replication and proliferation. We observed a concentration-dependent inhibition of HIV protein synthesis. Desitometric analysis of data from Western blot analysis showed sequence-specific and concentration-dependent oligo inhibition of p24 viral core antigen formation in the low-microM range. When lipofectin was used as a delivery vehicle, a markedly increased potentiation of the AS activity of the sequence was observed at a lower concentration (0.1 microM), following a 24-h preincubation. The AS construct specifically inhibited intracellular p24 production in chronically HIV-1-infected cells of lymphoid origin (H9/IIIB cells) by 95%, resulting in a 15-fold inhibitory effect relative to a similar sequence thiolated at only seven single-base positions. A concentration-dependent attenuation in the reverse transcriptase activity and a reduction in viral p24 level was observed in the culture supernatant of AS-pretreated HIV-1-infected phytohemagglutinin A-stimulated human cord blood mononuclear cells. Incubation of a HIV-1-infected lymphoid cell line with AS sequence resulted in a marked reduction in syncytium formation, and therefore protected cells from the cytopathic effects of the virus. Furthermore, the AS oligo did not appear to be cytotoxic in cell growth rate and colony-forming ability assays. The AS oligo described in this report is a useful new tool for the molecular analysis of HIV-1 gene expression and proliferation, and may have potential as a therapeutic agent.

Animals↗
PubMed1995

Didanosine compared with continued zidovudine therapy for HIV-infected patients with 200 to 500 CD4 cells/mm3. A double-blind, randomized, controlled trial. Canadian HIV Trials Network Protocol 002 Study Group.

OBJECTIVE: To compare the safety and efficacy of didanosine with that of continued zidovudine therapy in persons with human immunodeficiency virus (HIV) infection who had received zidovudine for at least 6 months and had CD4 cell counts of 200 to 500 CD4 cells/mm3. DESIGN: Double-blind, randomized controlled trial. SETTING: 10 Canadian university-affiliated specialty clinics. PATIENTS: 246 patients were assigned to receive standard doses of either zidovudine or didanosine. OUTCOME MEASURES: The primary clinical end point was the occurrence of a new, previously undiagnosed acquired immunodeficiency syndrome (AIDS)-defining illness or death. RESULTS: 245 of 246 patients were eligible (118 receiving didanosine and 127 receiving zidovudine). Sixty-six percent were asymptomatic, 30% had AIDS-related complex, and 4% had AIDS. The median baseline CD4 count was 320 cells/mm3. The median previous duration of zidovudine therapy was 471 days. Nine new AIDS-defining illnesses developed during the study; all but one were in the zidovudine group (relative risk, 7.9 [95% CI, 1.0 to 63.3; P = 0.02]). A change to didanosine led to a statistically significant increase in CD4 counts by week 2 that persisted until the end of the study at week 48 (P < or = 0.01). Viral sensitivity studies (done in 102 patients) showed that 28% of the zidovudine group and 21% of the didanosine group had high-level in vitro resistance to zidovudine (50% inhibitory concentration greater than 0.8 microM) at baseline (P = 0.49). Only one patient in the didanosine group developed high-level resistance to zidovudine during the study. In the zidovudine group, the cumulative probability of developing high-level resistance to zidovudine was 59% at 1 year (P = 0.01). Abdominal pain, leukopenia, and neutropenia were more frequent in the zidovudine group, and hyperuricemia was more frequent in the didanosine group (P < 0.05). CONCLUSION: In clinically stable patients with 200 to 500 CD4 cells/mm3 who had tolerated zidovudine for at least 6 months, a change to didanosine led to a decrease in the rate of disease progression, a sustained increase in CD4 counts, and a decrease in the chances of developing high-level resistance to zidovudine. Both drugs were generally well tolerated.

Adult↗
PubMed1995

A 3-week hepatitis B vaccination schedule provides rapid and persistent protective immunity: a multicenter, randomized trial comparing accelerated and classic vaccination schedules.

Hepatitis B (HB) vaccinations given once weekly for 3 weeks can provide early seroprotection. This study compared immune responses induced by the accelerated (A; days 0, 10, 21) and classic (C; days 0, 28, 56) HB vaccination schedules. Two hundred seventy healthy subjects (95 men, 175 women) with a mean age of 23.8 years received 3 doses of GenHevac B, a recombinant vaccine produced in mammalian cells. The subjects were randomly assigned to schedules A or C. A booster dose was given 1 year later. One month after the third dose, 70% (schedule A) and 92% (schedule C) of the subjects were seroprotected and 100% (A) and 99% (C) had developed anti-pre-S2 antibodies. Before booster injections, 93% (A) and 95% (C) of the subjects were seroprotected, and 1 month after the booster, almost all subjects were seroprotected. A 3-week HB vaccination schedule with GenHevac B can confer early protective immunity lasting up to 1 year.

Adolescent↗
PubMed1995

K65R mutation of human immunodeficiency virus type 1 reverse transcriptase encodes cross-resistance to 9-(2-phosphonylmethoxyethyl)adenine.

Cloned variants of human immunodeficiency virus type 1 that contain the K65R mutation in reverse transcriptase have previously been shown to display approximately 10- to 30-fold resistance against 2',3'-dideoxycytidine, 2',3'-dideoxyinosine, and 2',3'-dideoxy-3'-thiacytidine. On the basis of tissue culture studies with both primary T cells and established cell lines, we now report that the K65R mutation confers approximately 12- to 15-fold resistance to 9-(2-phosphonylmethoxyethyl)adenine (PMEA). Likewise, a chain termination system revealed that mutated recombinant K65R reverse transcriptase displays resistance to PMEA diphosphate, the active metabolite of PMEA, in cell-free enzyme assays. Parallel studies have shown that the M184V mutation in reverse transcriptase, associated with high-level resistance against the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine, does not confer resistance to PMEA in tissue culture. Viruses and enzymes that included both the K65R and M184V mutations were resistant to PMEA and PMEa diphosphate, respectively, but only to the extent conferred by the K65R mutation alone.

Adenine↗
PubMed1995

[Molecular basis and clinical significance of HIV-1 resistance to nucleoside compounds].

The prolonged use of anti-viral nucleosides (ZDV, ddI, ddC) in HIV-infected patients has given rise to the isolation of viral variants that display resistance against these compounds. Tissue culture selection experiments, involving increasing concentrations of anti-viral compounds, have likewise been shown to select for drug-resistant strains of HIV. Cloning, sequencing and site-directed mutagenesis have shown that a series of point mutations in the viral reverse transcriptase (RT) are responsible for this phenomenon. A different series of mutations in RT are responsible for resistance against non-nucleoside inhibitors of this enzyme. These mutations are due to the error-prone nature of RT during viral replication. Mutated forms of recombinant RT, that derive from drug-resistant viruses, have reduced affinity for relevant triphosphorylated nucleosides.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Development of HIV-1 resistance to (-)2'-deoxy-3'-thiacytidine in patients with AIDS or advanced AIDS-related complex.

OBJECTIVE: To determine the rate of development of in vitro HIV resistance to (-)2'-deoxy-3'-thiacytidine (3TC) and relate the effect of dose to emergence of resistance. METHODS: HIV-infected men and non-pregnant women, aged > or = 18 years, with a CD4 count < or = 300 x 10(6)/l cells were followed in a Phase I/II study, in which they were evaluated for tolerance to 3TC and effect of this agent with regard to viral susceptibility. Peripheral blood and plasma samples were collected at regular intervals for analysis. HIV was isolated using umbilical cord blood mononuclear cells as targets. These cells were also used in determinations of median inhibitory drug concentration. Specific amplification of the 184 mutation site, associated with HIV resistance to 3TC, was performed by polymerase chain reaction, using specific primer pairs, on DNA harvested from infected peripheral blood mononuclear cells (PBMC) of donors or, alternatively, on DNA that had been reverse transcribed from plasma-associated HIV RNA. RESULTS: Phenotypic resistance was detected in approximately one-third of individuals studied, who were followed between 8 and 56 weeks. Development of 3TC resistance occurred independently of dose, although time of first appearance of resistant HIV-1 variants appeared reduced at high 3TC doses. Amino-acid changes at codon 184 in HIV-1 reverse transcriptase were associated with, and preceded, the development of phenotypic 3TC resistance. Most commonly, a Met to Ile substitution appeared transiently before being superceded by a Val substitution at codon 184. CONCLUSIONS: In vitro resistance to 3TC developed in a high proportion of subjects who received prolonged monotherapy with this drug. The development of resistance to 3TC was associated with appearance of mutated viral forms and the disappearance of wild-type virus, with regard to codon 184, in both patient plasma and PBMC.

AIDS-Related Complex↗
PubMed1994

Randomised placebo-controlled trial of recombinant interleukin-2 in chronic uraemic patients who are non-responders to hepatitis B vaccine.

Natural interleukin-2 at low dose has been reported to overcome the non-responsiveness of patients with chronic uraemia to hepatitis B vaccine. Therefore, we revaccinated 52 previous such non-responders (24 on maintenance dialysis) with 20 micrograms of recombinant preS2-containing hepatitis B vaccine with human recombinant interleukin-2 (1 MU) or placebo (randomly allocated). Seroconversion rates (74 vs 80%, respectively) and proportion of patients who elicited anti-HBs titres of 10 mlU/mL or more (56 vs 68%) were similar in both groups. Our results do not confirm local injection of interleukin-2 as an effective immunoadjuvant to hepatitis B vaccine in uraemic patients.

Adjuvants, Immunologic↗
PubMed1994

Generation of multiple drug resistance by sequential in vitro passage of the human immunodeficiency virus type 1.

We have sequentially passaged both laboratory and clinical isolates of the human immunodeficiency virus type 1 (HIV-1) in MT-4 cells in the presence of increasing concentrations of different drugs to derive viral variants that are multiply resistant to various combinations of ddC, ddI, d4T and AZT. The EC50 values obtained for the viruses thus generated varied between 50-100 times above those of parental wild-type strains in the case of AZT, 20-30 times for d4T, but only 10-15 times for ddI and ddC. Cultivation of AZT-resistant viruses in the presence of increasing concentrations of ddI yielded viruses that were resistant to the latter compound, with no apparent decrease in susceptibility to AZT. Sometimes, viruses selected for resistance against ddI were cross-resistant as well against ddC, although most viruses selected for resistance to ddC were not cross-resistant to ddI. Combinations of two or three of these compounds inhibited replication of HIV variants that displayed resistance to the same drugs when tested individually. No emergence of drug resistance was demonstrable when combinations of drugs were employed simultaneously in these selection protocols or when single drugs were used in concert with interferon-2 alpha or high dilutions of virus-neutralizing antisera. Cloning and sequencing of some viruses resistant to each of AZT, ddI, and ddC revealed the simultaneous presence of mutations at sites 41, 74, 184 and 215 within the HIV pol gene open reading frame.

Antiviral Agents↗
PubMed1994

Identification of a mutation at codon 65 in the IKKK motif of reverse transcriptase that encodes human immunodeficiency virus resistance to 2',3'-dideoxycytidine and 2',3'-dideoxy-3'-thiacytidine.

The technique of in vitro selection was used to generate variants of the human immunodeficiency virus type 1 that are resistant to 2',3'-dideoxycytidine (ddC). Most of the pol regions of such viruses, including the complete reverse transcriptase open reading frame and portions of flanking protease and integrase genes, were cloned and sequenced, using PCR-based procedures. Mutations were variously detected at amino acid site 65 (Lys-->Arg; AAA-->AGA) and at a previously reported codon, site 184 (Met-->Val; ATG-->GTG). We introduced the site 65 mutation into the pol gene of infectious, cloned HxB2-D DNA by site-directed mutagenesis in order to confirm by viral replication assay the importance of this site in conferring resistance to ddC. The recombinant virus possessed greater than 10-fold resistance against this compound in comparison with parental HxB2-D. Cross-resistance of approximately 20- and 3-fold, respectively, was detectable against the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine and 2',3'-dideoxyinosine but not against 3'-azido-3'-deoxythymidine. Combinations of the site 65 and 184 mutations did not yield levels of resistance higher than those attained with the site 65 mutation alone. The presence of the site 65 mutation was confirmed by PCR analysis of peripheral blood mononuclear cells from patients on long-term ddC therapy in 4 of 11 cases tested. Viruses that possessed a ddC resistance phenotype were isolated from subjects whose viruses contained the site 65 mutation in each of four instances. Four of these clinical samples were also demonstrated to possess the Met-184-->Val mutation, and one of them possessed both the Lys-65-->Arg and Met-184-->Val substitutions. Direct cloning and sequencing revealed the site 65 mutation in viruses isolated from these individuals.

Amino Acid Sequence↗
PubMed1994

Comparison of cord blood and peripheral blood mononuclear cells as targets for viral isolation and drug sensitivity studies involving human immunodeficiency virus type 1.

We have shown that umbilical cord blood mononuclear cells (CBMC) are at least as sensitive as peripheral blood mononuclear cells (PBMC) for isolation of human immunodeficiency virus type 1 from the PBMC of infected individuals. Viral replication was more efficiently monitored by a p24 antigen capture assay than by a viral reverse transcriptase test, regardless of whether CBMC or PBMC were employed. We also found that CBMC and PBMC yielded similar results with regard to the susceptibility profiles of both wild-type and drug-resistant variants of human immunodeficiency virus type 1 for 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine, and the (-) enantiomer of 2',3'-dideoxy-3'-thiacytidine. Finally, viruses isolated on CBMC could be routinely grown on PBMC and vice versa.

Antiviral Agents↗
PubMed1994

Development and significance of nucleoside drug resistance in infection caused by the human immunodeficiency virus type 1.

Nucleoside antagonists of human immunodeficiency virus (HIV) reverse transcriptase (RT) activity have been commonly used in the therapy of HIV-associated disease. The prolonged use of such drugs has led to the development of HIV variants that display resistance against these compounds. HIV drug resistance has been documented clinically for each of the following nucleosides: 3'-azido-3'-deoxythymidine (AZT; zidovudine, ZDV), 2',3'-dideoxyinosine (ddI; didanosine), and 2',3'-dideoxycytidine (ddC; zalcitabine). In addition, resistance has been demonstrated against a series of non-nucleoside inhibitors of the viral RT. Several groups have documented that a series of point mutations within the HIV pol gene, that encodes the RT enzyme, is responsible for HIV drug resistance. Diminished sensitivity to anti-viral drugs results from both the selective pressure exerted by these compounds in individuals receiving prolonged therapy and the error-prone nature of the viral RT itself, thus permitting the outgrowth of mutated forms. Patients suffering from both disease progression and/or low CD4 counts are most likely to develop HIV drug resistance.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Clinical correlates of in vitro HIV-1 resistance ot zidovudine. Results of the Multicentre Canadian AZT Trial.

OBJECTIVE: To describe the rate of development of in vitro HIV resistance to zidovudine (ZDV) and its prognostic implications within the Multicentre Canadian AZT Trial (MCAT). METHODS: HIV-infected subjects in Centers for Disease Control (CDC) stages IIB, III and IVC-2 with CD4 cell counts > 270 x 10(6)/l were treated with ZDV as part of a dose-range study. Participating volunteers underwent prospective clinical and laboratory evaluations at regular intervals. Viral cultures and sensitivity testing were performed every 12 weeks in a predefined subset of 50 volunteers. An isolate was designated ZDV-resistant if it had a median inhibitory concentration (IC50) for ZDV at least 50-fold higher than that of virus isolated from the same subject before initiation of antiviral chemotherapy. The relationship between resistance and subsequent disease progression was studied using the Mantel and Byar method, for which, at each instance of disease progression, 2 x 2 tables classifying progression versus resistance status were constructed. The observed number of progressions was compared with that expected under the null hypothesis using Mantel-Haenszel methods adjusted for baseline CD4:CD8 ratio. RESULTS: The Kaplan-Meier estimate for the cumulative development of in vitro resistance was 64% [95% confidence interval (CI), 41-78] at 180 weeks. Baseline CD4:CD8 ratio was negatively associated (P = 0.10) with the subsequent development of resistance (proportional hazard, 0.44; 95% CI, 0.17-1.10). After adjusting for baseline CD4:CD8 ratio, the numbers of observed and expected progressions following the development of resistance were 15 and 7.6, respectively (P = 0.008). A similar relative risk of progression between resistant and non-resistant states was found in the two CD4:CD8 strata; observed and expected progressions were 4 and 2.3 and 11 and 5.2 in the high and low CD4:CD8 strata, respectively. CONCLUSIONS: In vitro resistance to ZDV developed in 64% of subjects after 180 weeks of ZDV therapy. Lower CD4:CD8 ratio at baseline was associated with faster development of resistance. In addition, the development of resistance was found to be a marker of subsequent disease progression. This association persisted after adjustment for baseline CD4:CD8 ratio. Whether in vitro resistance to ZDV is merely a surrogate marker or a determinant of disease progression remains to be established.

Adult↗
PubMed1993

HIV resistance to anti-viral drugs.

The use of zidovudine (ZDV) and other forms of nucleoside therapy, including dideoxyinosine (ddI), to treat HIV-infected individuals has led to both longer survival and improved quality of life. However, ZDV-resistant variants of HIV-1 can be isolated from patients undergoing prolonged therapy with this drug. HIV drug resistance against ZDV, ddI and other nucleosides is attributable to a series of point mutations within the pol gene of HIV-1 that encodes the viral enzyme, reverse transcriptase (RT). This is not surprising, since the virus is known to replicate at high rates in infected individuals; moreover the RT which mediates transcription of proviral DNA from viral genomic RNA is known to be highly error-prone. Thus, mutants of HIV-1, which possess a drug resistance phenotype and genotype, may be expected to emerge under the selective pressure of long-term anti-viral chemotherapy. HIV drug resistance occurs most commonly in individuals with low CD4 counts, who have progressed to more serious forms of disease. Moreover, viruses obtained from patients with AIDS generally display higher levels of resistance, relative to pre-treatment isolates, than do viruses from patients with more limited illness. Although observations of drug resistance can be correlated with disease progression and a weakened immune system, it is still unclear whether a cause and effect relationship exists. Current clinical research is designed to answer this question while testing the notion that combinations of nucleosides and immuno-stimulatory drugs may provide important clinical benefits.

Cross Reactions↗
PubMed1992

[Vaccination against measles at 6 months of age].

Measles immunization with the Edmonston Zagreb stain was carried out in 71 six-month-old infants. Proportions of subjects with immunity were 91% among the 47 subjects retested before one year of age and 100% among the 28 subjects retested between two and three years of age. These results support the WHO recommendation that measles immunization should be given at the age of six months. The concerns expressed by some about possible adverse effects of early measles immunization (decreased immune defenses) are discussed, as well as the transfer of maternal antibodies and persistence of these antibodies in the child. The obstacles to such studies in developing countries, including the need for repeated phlebotomies with centrifugation of specimens and freezing of sera, could be circumvented by the use of filter paper dried blood spot samples which seem to provide reliable results although with values somewhat lower than those found in frozen sera.

Antibodies, Viral↗
PubMed1990

Treatment of ureteric colic. Intravenous versus rectal administration of indomethacin.

A randomised multicentre clinical trial was undertaken to compare the effect on pain of indomethacin administered either intravenously or rectally to 116 patients with ureteric colic. Adverse reactions were also assessed. Of the patients receiving the intravenous injection, 48/53 (91%) achieved good pain relief (i.e. no supplementary analgesia was required) 30 min after administration, compared with 46/63 (73%) receiving the enema. Significantly more side effects occurred in the group treated intravenously. It was concluded that indomethacin administered as an enema was less effective than the intravenous form, but it should be regarded as a good alternative in the treatment of ureteric colic.

Administration, Rectal↗