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T Salas

Publications and source records attributed to T Salas.

14 recordsLinked to original sources
PubMed1995

Potential applications of proviral load measurement in clinical retrovirology.

We have previously noted an association between proviral load and the severity of immune disease in individuals with a wide range of CD4 cell counts. Using the quantitative DNA polymerase chain reaction technology developed in our laboratory, we sought to extend these observations, with a view to establishing guidelines for the use of proviral load in a clinical context. We studied 199 patients with a range of CD4 cell counts attending an urban tertiary care center. Proviral load/10(6) peripheral blood mononuclear cells (PBMCs) was measured using a microtiter plate assay designed specifically for this purpose. Human immunodeficiency virus proviral DNA was detected in 193 of 199 clinical samples. Levels of proviral load were tabulated for patients and evaluated in seven categories defined by CD4 cell counts. Although a wide range of proviral loads was observed in each category of patients, there was a trend toward increasing proviral load with decreasing CD4 cell count. Statistically significant relationships were observed between proviral load and the CD4 cell count and the CD4 cell percentage (Spearman's correlation coefficient -0.19, p = 0.01 for both absolute CD4 and CD4 percentage). These relationships were quite weak and could not be taken to explain disease progression in isolation. If we defined a cutoff between low and high proviral loads at 100 copies/10(6) PBMCs, we noted that 52% (24 of 46) of patients with CD4 cell counts > 400/microliters had lower loads, as compared with 16% (24 of 143) of those with more advanced disease (p < 0.01). There is a weak, but statistically significant association between proviral load and CD4 cell depletion.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4 Lymphocyte Count↗
PubMed1992

OLIGSCAN: a computer program to assist in the design of PCR primers homologous to multiple DNA sequences.

OLIGSCAN (oligonucleotide scanner) is a computer program for IBM-PC-compatible computers that allows the user to scan up to 200 DNA sequences for homology to oligonucleotide sequences of interest. Once a core sequence of longer than the user-defined minimum length is found, the remainder of the oligonucleotide is compared to the corresponding positions of the larger sequence to identify matches or mismatches flanking the core region. This algorithm results in identification of the longest possible homologous regions first. The program was originally designed to assist in the identification of potential annealing sites for polymerase chain reaction (PCR) primers in the genomic DNA of related strains of viruses. However, it may also be used for more general pattern-identification purposes, including scanning for various sequence motifs of functional importance. We present the analysis of homology to an oligonucleotide primer in 16 complete genomic sequences of the human and simian immunodeficiency viruses.

Algorithms↗
PubMed1992

Rapid DNA fingerprinting to control for specimen errors in HIV testing by the polymerase chain reaction.

Variable-number-tandem-repeats (VNTRs) are highly polymorphic and provide informative genetic markers for distinguishing between individuals. We have used PCR amplification of VNTR locus pMCT118 to identify mislabelled specimens submitted for HIV PCR testing. The method is rapid, can be applied to large numbers of samples and eliminates the need for radioactive probes. DNA samples (10 ng) are amplified for 25 cycles using fluorescence-labelled oligonucleotide primers (blue dye). An aliquot of the PCR product is then combined with an internal lane size standard (labelled with a red dye), electrophoresed through a 2% agarose gel on an automated fluorescence DNA fragment analyser and the size and quantity of the fragments determined automatically relative to the internal standard. Fifteen alleles, ranging in size from 398 tp 709 bp were readily identified in a random sampling of DNA from 63 unrelated HIV-infected patients. Fragment size was reproducible and corresponded to alleles containing from 16 to 35 repeats of a 16 bp unit. VNTR genotyping will prove useful for resolving discordant results due to specimen mix-up and ensuring that the correct samples have been analyzed.

Alleles↗
PubMed1992

Stability of dried blood spot specimens for detection of human immunodeficiency virus DNA by polymerase chain reaction.

Blood sampling on filter paper has many advantages for the detection of perinatal human immunodeficiency virus (HIV) infection by the polymerase chain reaction (PCR). However, if the method is to be widely used, an assessment of its performance under field conditions is required. To simulate conditions in the field, 50-microliters aliquots of whole blood containing low levels of HIV proviral DNA (4 to 1,024 copies per 100,000 nucleated cells) were spotted onto filter paper; dried; and subjected to heat, humidity, and prolonged storage at room temperature. After exposure, the DNA was recovered and amplified with primers to human leukocyte antigen DQ alpha- and HIV-specific sequences. Treatment at 37 degrees C and 60% humidity for 7 days, storage for 12 weeks at 22 degrees C, and freeze-thawing twice had no adverse effect on PCR reactivity when compared with the results obtained with reference spots stored at -20 degrees C. The lower limits of HIV detection in all tests ranged from 4 to 16 HIV copies per 100,000 cells. Fixation in 70% ethanol improved the amplification of low levels of HIV DNA and reduced biohazard risks. These findings suggest that dried blood spots will provide a powerful new resource for testing for HIV by PCR, especially in remote areas where refrigeration and immediate sample processing are unavailable.

Blood Specimen Collection↗
PubMed1992

Detection of incident HIV infection by PCR compared to serology.

In order to determine the most sensitive method for the early detection of HIV infection, polymerase chain reaction (PCR) and serology were compared using matched peripheral blood mononuclear cells (PBMC) and serum samples taken sequentially at 3-month intervals on 17 HIV seroconverters. All samples from the time of enrollment in the study to the time of seroconversion were studied. [There were only two of the 17 cases where PCR and antigen positivity preceded EIA detectable seroconversion.] Initially, one of these cases was found to be PCR positive 11 months prior to seroconversion, however DNA fingerprinting techniques indicated that the early positive specimen did not belong to the subject in question. In a single subject, PCR was negative at the time of serologic evidence of infection but was positive at the next sampling 3 months later. In the remaining 14 cases, PCR was positive at the same sample time as full or partial seroconversion as determined by three EIA screening tests and Western blot. EIA antibody screen tests showed variability in detection of early HIV antibodies. We found no evidence for prolonged HIV infection prior to seroconversion. PCR offers little if any advantage over serology in the early detection of HIV infection in adults.

AIDS Serodiagnosis↗
PubMed1992

Diagnosis of vertical HIV-1 transmission using the polymerase chain reaction and dried blood spot specimens.

We have used the polymerase chain reaction (PCR) to detect HIV proviral sequences in minute amounts of peripheral blood collected onto newborn screening blotters. Forty-three newborns, infants, and children of HIV-infected mothers were serially studied: dried blood spot (DBS) specimens were processed for PCR; serum was assayed for HIV antibodies, p24 antigen, and immunoglobulins; mononuclear cells were cultured and CD4 cells were quantitated by immunofluorescence. There was excellent agreement between the results of blood spot PCR, viral culture, and clinical and immunological indicators of HIV infection. Eighteen of 19 infected children tested positive by both PCR and culture, including six asymptomatic infants who were less than 10 weeks of age. As expected, p24 antigen capture assays were insensitive, detecting only 13 of the 19 infected children. One infected infant tested positive by PCR, but negative by culture and antigen. This infant was seropositive at 27 months and had pronounced hypergammaglobulinemia in association with non-specific symptoms. Twenty-four of the 43 infants were asymptomatic with normal immune profiles, declining antibody levels and no evidence of infection. These children tested repeatedly negative by PCR, culture, and p24 antigen assays. Our results indicate that DBS PCR is a sensitive, specific, and cost-effective alternative to viral culture for the early diagnosis (or exclusion) of perinatal HIV infection. DBS sampling opens the way for large-scale prospective studies to determine the exact rates of vertical HIV transmission in industrialized, as well as, nonindustrialized countries.

Child, Preschool↗
PubMed1991

Improved detection of HIV-1 envelope sequences using optimized PCR and inosine-substituted primers.

We describe inosine-substituted 'consensus' primers for the detection of HIV-1 envelope sequences by the polymerase chain reaction. The primers, modifications of SK68 and SK69, are highly specific (100%) and sensitive (greater than 94%) and they prevent false-negative results due to variation in the HIV-1 genome. Consensus primers are needed to ensure the detection of most, if not all, variants of HIV-1 including American, African and newly emerging strains.

AIDS-Related Complex↗
PubMed1991

Use of dried blood spot specimens in the detection of human immunodeficiency virus type 1 by the polymerase chain reaction.

Dried blood spots (DBSs) constitute a potentially valuable source of material for human immunodeficiency virus (HIV) serologic and molecular testing. To facilitate molecular testing, we have adapted the polymerase chain reaction (PCR) to the detection of HIV proviral DNA in DBS samples. The method is highly reproducible, with 75 microliters of whole dried blood providing sufficient DNA for duplicate testing with three primer sets. By using DBS PCR, 66 of 69 (95.6%) seropositive at-risk individuals tested positive by at least two primer sets and 85 of 85 (100%) low-risk seronegative blood donors tested negative by all three sets of primers. The frequency of HIV DNA detection in seronegative at-risk individuals was low, with only 1 of 58 (1.7%) individuals testing positive. These results show that in a clinical environment, HIV PCR analysis of DBS specimens is specific and sensitive. The method is cost effective and presents a useful alternative to the isolation of HIV from seropositive babies with an undefined infection status.

Blood↗
PubMed1990

The effect of tuberculosis as a new AIDS definition criterion in epidemiological surveillance data from a south European area.

In this article, we evaluate the effect of the 1987 revised CDC AIDS definition on the AIDS epidemiological surveillance in Catalonia. From data collected in our population-based registry, we observed a 1.3- and a 1.6-fold increase in AIDS prevalence and incidence rates, respectively. In our setting, the new criteria appear to affect case ascertainment in male intravenous drug abusers, with extrapulmonary tuberculosis being the disease that accounts for the major increase in the identified cases. An additional effect of this case revision has been on the median survival time of AIDS patients, which will probably increase due to the use of the new definition criteria.

Acquired Immunodeficiency Syndrome↗
PubMed1989

[Course of the epidemic of acquired immunodeficiency syndrome in Catalonia. Descriptive analysis of the case registry].

Since the beginning of the acquired immunodeficiency syndrome (AIDS) epidemic, the systems for epidemiological surveillance have monitored the dynamics of spread of the disease, thus permitting to identify the possible risk factors and the evaluation of the preventive measures that have been carried out. In the present article the data collected in the AIDS registry for Catalonia are reported. In contrast with the overall figures for the rest of Spain, in Catalonia the most numerous group of patients was represented by homosexual or bisexual males until the second half of 1986; since then, parenteral drug abusers became the major group of risk as in other countries from Southern Europe. In addition, a consistent increase in the number of involved females and children and a small increase in those cases where the only possible known route of transmission was heterosexual contact was observed.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Mapping of porcine parvovirus DNA and development of a diagnostic DNA probe.

Dimeric and monomeric replicative forms of DNA of porcine parvovirus (PPV) strain NADL-2 were isolated and examined by restriction enzyme analysis and reciprocal Southern blot hybridization during development of a DNA probe for PPV. Genomic single stranded PPV DNA was 5.0 kb long, and results substantiated the rolling-hairpin model of parvovirus DNA replication with the primer sequence located in the 3' terminal hairpin loop. An additional finding was the generation of a 4.7 kb species of viral DNA which was considered to be a 0.3 kb deletion variant of genomic PPV DNA. A 3.0 kb DNA fragment obtained by Pst I/Hind III digestion of monomer replicative form DNA was cloned into a plasmid vector, pUC 19. The cloned fragment, recovered from transformed Escherichia coli strain TB1 and labelled with [32P] dCTP, was evaluated by dot hybridization as a probe for PPV in infected cell cultures. The probe was specific for PPV infected cells, and was 100 times more sensitive than the standard hemagglutination test.

Animals↗