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B Weiser

Publications and source records attributed to B Weiser.

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

Maternal plasma human immunodeficiency virus type 1 RNA level: a determinant and projected threshold for mother-to-child transmission.

To prevent mother-to-child human immunodeficiency virus type 1 (HIV-1) transmission, it is important to identify its determinants. Because HIV-1 RNA levels can be reduced by antiviral therapy, we examined the role of maternal plasma HIV-1 RNA level in mother-to-child transmission. We used quantitative competitive PCR to measure HIV-RNA in 30 infected pregnant women and then followed their infants prospectively; 27% of the women transmitted HIV-1 to their infants and maternal plasma HIV-1 RNA level correlated strikingly with transmission. Eight of the 10 women with the highest HIV-1 RNA levels at delivery (190,400-1,664,100 copies per ml of plasma) transmitted, while none of the 20 women with lower levels (500-155,800 copies per ml) did (P = 0.0002). Statistical analysis of the distribution of HIV-1 RNA loads in these 30 women projected a threshold for mother-to-child transmission in a larger population; the probability of a woman with a viral RNA level of < or = 100,000 copies per ml not transmitting is predicted to be 97%. Examination of serial HIV-1 RNA levels during pregnancy showed that viral load was stable in women who did not initiate or change antiviral therapy. These data identify maternal plasma HIV-1-RNA level as a major determinant of mother-to-child transmission and suggest that quantitation of HIV-1 RNA may predict the risk of transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Quantitation of human immunodeficiency virus type 1 during pregnancy: relationship of viral titer to mother-to-child transmission and stability of viral load.

To develop strategies to prevent mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1), it is important to define the factors determining it. We examined the relationship between maternal HIV-1 titer and the occurrence of mother-to-child transmission. In addition, we quantitated HIV-1 longitudinally in mothers during pregnancy, at delivery, and up to 1 year postpartum. To examine transmission, we prospectively studied 19 mother-child pairs; in 5 pairs, HIV-1 transmission occurred. We used endpoint dilution culture of peripheral blood mononuclear cells to determine maternal viral titer and found that although 4 of 6 (67%) women with viral titers of > or = 125 HIV-1 infectious units per 10(6) cells transmitted HIV-1 to their infants, only 1 of 13 (7.6%) women with lower viral titers transmitted (P = 0.01). Twelve of the 19 mothers had HIV-1 loads determined serially 3-8 times over periods ranging from 18 to 65 weeks. Viral titers varied greatly between the 12 women, but the viral load in each woman remained stable over time. In this cohort, HIV-1 viral load remained stable during pregnancy and the greater the maternal viral burden, the more likely that transmission occurred. These two related findings suggest that determination of HIV-1 titers early in pregnancy may predict which women are at high risk of transmitting to their infants and may be used to counsel HIV-1-infected women of childbearing age. These data identify maternal viral titer as a major determinant of mother-to-child HIV-1 transmission and thereby provide the scientific rationale for therapeutic strategies designed to interrupt transmission by lowering viral load.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Constraint satisfaction techniques for modeling large complexes: application to the central domain of 16S ribosomal RNA.

Standard experimental techniques for determining the structure of small to moderately-sized molecules are difficult to apply to large macromolecular complexes. These complexes, consisting of multiple protein and/or nucleic acid components, can contain many thousands of atoms and the experimental techniques used to study them provide relatively sparse structural information with significant measurement uncertainty. Computational technologies are required to reduce the conformational search space and synthesize the data in order to produce the structures or (more usually) sets of structures compatible with the data. In this paper, we show that a method based on the constraint satisfaction paradigm produces a three-dimensional topology for the central domain of the 16S ribosomal RNA that is generally consistent with interactively built models, although differing in significant ways. The modeling incorporates information about secondary structure of the nucleic acid, neutron diffraction data about the relative positions and uncertainties of the proteins, and protection experiments indicating proximities of segments of RNA to specific protein subunits. Unlike previously proposed models, our model contains explicit information about the range of positions for each subunit that are compatible with the data. The system uses a grid search, checks distances in a direction-dependent manner, uses disjunctive distance constraints, and checks for volume overlap violations.

Animals↗
PubMed1991

Evolution of human immunodeficiency virus type 1 nucleotide sequence diversity among close contacts.

The degree of change in the nucleotide sequence of human immunodeficiency virus type 1 (HIV-1) that occurs when it is transmitted sexually from one individual to another or vertically from mother to child is unknown. Previous studies have shown that most cultured HIV-1 isolates from the same individuals differed in the entire envelope gene nucleotide sequence by up to 2%, although most isolates from unrelated individuals differed by 6-22%. To examine diversity among HIV-1 isolates from close contacts, we determined the nucleotide sequences of viruses from a family with a known epidemiologic profile, in which a woman transmitted HIV-1 heterosexually to her partner and vertically to her daughter. Direct DNA sequence analysis of primary HIV-1 isolates amplified by PCR was used to distinguish the major and minor viral sequences, termed quasispecies, to rapidly determine the predominant sequences and their phylogenetic relationships. The nucleotide sequence diversity of a major portion of the HIV-1 envelope gene was 3.7% between isolates from the woman and her heterosexual partner and 8.5% between isolates from this woman and her daughter, who had been infected for a longer period than the partner. The configuration of the phylogenetic tree demonstrated that the daughter's predominant isolate evolved from a progenitor of her mother's current strain. This study provides evidence of a continuous spectrum of sequence diversity between any two isolates ranging from those derived from the same person to those from close contacts and, ultimately, those from unrelated individuals. These data and methods can be applied to epidemiologic investigations of possible HIV-1 transmission between health care workers and their patients.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Long HIV-1 incubation periods and dynamics of transmission within a family.

The incubation period of human immunodeficiency virus type 1 (HIV-1) infection was studied in a family of five in which vertical and heterosexual transmission occurred from one index case. This investigation documented incubation periods of longer than 12 years in a mother and her daughter; although neither has symptoms, both are definitely infected and have very low CD4(+)-lymphocyte counts. The study confirmed the predictions of incubation periods longer than 10 years in a small proportion of infected individuals. It provides evidence that vertically HIV-1-infected teenagers can be expected to appear in the population.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Human immunodeficiency virus type 1 expression in the central nervous system correlates directly with extent of disease.

To investigate human immunodeficiency virus type 1 (HIV-1) pathogenesis in infected individuals and examine the correlation of HIV-1 expression with extent of clinical and pathologic disease, we studied spinal cords from acquired immunodeficiency syndrome patients with a wide range of spinal cord pathology. By performing in situ hybridization with HIV-1-specific riboprobes, we detected HIV-1 RNA in all 10 cords from acquired immunodeficiency syndrome patients with a common, characteristic pathologic entity called vacuolar myelopathy but not in 10 control cords from HIV-1-infected and uninfected patients. In the cords from individuals with vacuolar myelopathy, the level of HIV-1 RNA expression correlated directly with extent of spinal cord pathology and clinical findings. These data support a role for HIV-1 in the pathogenesis of tissue damage and related clinical disease in infected individuals.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Dose-limiting toxicity of rifabutin in AIDS-related complex: syndrome of arthralgia/arthritis.

We studied the tolerance of humans to rifabutin, a rifamycin with antimycobacterial and in vitro anti-HIV activity. Sixteen subjects with AIDS-related complex were treated for 4-66 weeks with stepwise increasing oral doses of rifabutin from 300 to 2400 mg/day. The highest dose attained was twice that previously reported for humans. Serum and cerebrospinal fluid levels of drug were detected by high-pressure liquid chromatography. A reversible syndrome of arthritis/arthralgia, not previously described, was seen in most (nine out of 10) of those given doses exceeding 1050 mg/day. Uveitis and aphthous stomatitis developed at doses of approximately 1800 mg in two of those with joint manifestations. Typical manifestations of Reiter's syndrome were not seen in any patient. An orange-tan skin pigmentation was almost universal. Other toxicities resembled those previously associated with rifampin. Serum levels did not approach those found to inhibit HIV significantly in vitro. No consistent antiviral or immunological effects were observed; even at the highest doses, rifabutin did not appear to inhibit cellular immunity. Rifabutin was well tolerated at daily doses blow 1 g.

AIDS-Related Complex↗
PubMed1990

Ventricular tachycardia in two patients with AIDS receiving ganciclovir (DHPG).

We report two cases of patients who developed ventricular tachycardia while receiving intravenous infusions of ganciclovir [9-(1,3-dihydroxy-2-propoxy)methylguanine, DHPG]. Worsening cytomegalovirus infection prompted renewal of ganciclovir therapy under close cardiac monitoring in one of these patients, and ventricular tachycardia recurred. The close temporal relationship between administration of the drug and onset of the arrhythmias in conjunction with the absence of other factors known to predispose to arrhythmias suggest that ganciclovir may have played a role in the development of arrhythmias in these patients. The clinical courses of the patients are discussed, as are autopsy results.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Human immunodeficiency virus type 1 in spinal cords of acquired immunodeficiency syndrome patients with myelopathy: expression and replication in macrophages.

Spinal cord disease is common in patients infected with human immunodeficiency virus type 1 (HIV-1), and a characteristic vacuolar myelopathy is present at autopsy in approximately one-fourth of acquired immunodeficiency syndrome patients. Pathologic examination of the spinal cord shows vacuolation of white matter and infiltration by macrophages, a process distinct from HIV-1 encephalopathy. To determine the presence and localization of HIV-1 RNA in the spinal cords of acquired immunodeficiency syndrome patients with vacuolar myelopathy, we used the technique of combined in situ hybridization and immunohistochemical staining on the same slide. Spinal cord tissue sections were stained with markers for macrophages, endothelial cells, oligodendroglia, astrocytes, and myelin and then hybridized in situ with HIV-1-specific RNA probes. Combined in situ hybridization and immunohistochemical staining on three spinal cords showed HIV-1 expression in mononuclear and multinucleated macrophages localized mainly to areas of myelopathy in spinal cord white matter. Immunohistochemical staining and electron microscopy showed myelin within macrophages and electron microscopy revealed HIV-1 budding from macrophages. These data suggest a role for HIV-1-infected macrophages locally in the pathogenesis of vacuolar myelopathy and add to the body of evidence that these cells play a role systemically in the development of HIV-1-related disease.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Efficacy of rifabutin in the treatment of AIDS-related complex.

We performed a phase 1-2 antiviral dose escalation trial of rifabutin, a rifamycin antibiotic with anti-HIV-1 activity in vitro. We followed 16 men with AIDS-related complex (ARC) for a mean duration of 29 weeks; the maximum toxicity-limited dose of rifabutin was 2400 mg/day, which was achieved in two patients. There was some evidence of anti-HIV-1 activity in two patients, one of whom had an improvement in immune status, but 11 of the 16 patients showed a deterioration in either virologic or immunologic status. The majority of the patients under study remained clinically stable during the trial, but there was clinical deterioration in the three who entered with CD4 cell counts of less than 100 x 10(6)/l. On the basis of this trial, rifabutin as a single antiviral agent does not appear to be beneficial to ARC patients.

AIDS-Related Complex↗
PubMed1988

Model for the three-dimensional folding of 16 S ribosomal RNA.

We have derived a model for the three-dimensional folding of Escherichia coli 16 S ribosomal RNA, using interactive computer graphic methods. It is based on (1) the secondary structure derived from comparative sequence analysis, (2) the three-dimensional co-ordinates for the centers of mass of the 30 S subunit proteins, and (3) the locations of sites in 16 S rRNA that interact with specific ribosomal proteins, from footprinting and crosslinking studies. We present a detailed description of the derivation of the model. About 75% of the RNA chain is sufficiently constrained to provide a useful model. This contains most of the universally conserved core of the molecule. In all but a few instances, protected and crosslinked sites can be placed within or very close to their cognate proteins, while obeying stereochemical rules. The overall shape of the model and locations of specific regions of the RNA correspond well to data derived from electron micrographs of 30 S subunits, although such data were not used to construct the model. Phylogenetic variations in the structure are readily accommodated; as an example, we have modeled the 950-nucleotide mammalian mitochondrial 12 S rRNA by superimposing it on the E. coli structure. The three major RNA domains, as defined by secondary structure, appear to exist as autonomous structural units in three dimensions, for the most part. There is an extensive interface between the 5' and central domains, whereas the 3' major domain has relatively little apparent contact with the rest of the structure. The 5', central and 3' major domains form structures that resemble the body, platform and head, respectively, seen in electron micrographs of 30 S subunits. We discuss possible roles for the ribosomal proteins in stabilizing specific structural features of the RNA during ribosome assembly. The decoding site, as deduced from footprinting and crosslinking studies involving the tRNA anticodon stem-loop, is well-localized. Bases protected from chemical probing by the anticodon stem-loop line the cleft of the subunit. The conserved loop at position 530, which contains some of the bases protected by A site-bound tRNA, is remote (approx. 80 A) from the decoding site. Protection of these bases by the anticodon stem-loop is thus unlikely to be due to direct contact.

Base Sequence↗
PubMed1988

Comparison of antigen immunoassay and reverse transcriptase assay for monitoring human immunodeficiency virus infection in an antiviral trial.

We compared the Abbott enzyme immunoassay for human immunodeficiency virus (HIV) antigen with the reverse transcriptase assay (RTA) as a means of monitoring HIV infection during an antiviral trial. The Abbott enzyme immunoassay detected HIV earlier than RTA whether or not the patients were antigenemic and appears to be superior to RTA for detecting HIV in cultures used for monitoring clinical trials.

AIDS-Related Complex↗
PubMed1987

Antibody to human immunodeficiency virus correlates with decreased T helper lymphocytes in asymptomatic individuals.

To examine the relationship between human immunodeficiency virus (HIV) seropositivity and T lymphocyte subsets in a clinically well population, we assayed HIV antibody and analyzed T lymphocyte subsets in 30 people at increased risk for acquired immunodeficiency syndrome (AIDS) who were clinically well. Seventy-six percent of the HIV-seropositive individuals had abnormally low numbers of T helper lymphocytes, and HIV seropositivity was strongly correlated with an abnormally low number of T helper cells (p less than 0.00002). Among these clinically well subjects at increased risk for AIDS, HIV-sero-positive individuals had a significant decrease in mean T helper lymphocytes and mean T helper:T suppressor ratios as compared to those who were seronegative (483 cells/mm3 vs 915 cells/mm3, p less than 0.002; and 0.80 vs 1.7, p less than 0.002, respectively). Because of the strong correlation of HIV seropositivity and abnormally low numbers of T helper lymphocytes in this asymptomatic population, these findings suggest that asymptomatic seropositive individuals should be followed closely for development of AIDS-related disease and should be considered for future antiviral therapy when it becomes available.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Transmission of lymphadenopathy-associated virus/human T lymphotropic virus type III in sexual partners. Seropositivity does not predict infectivity in all cases.

To investigate transmission of lymphadenopathy-associated virus (LAV)/human T lymphotropic virus type III (HTLV-III) in long-term sexual partners, and the relationship between lymphadenopathy-associated virus seropositivity and transmission, nine couples (five heterosexual and four homosexual) at increased risk for acquired immune deficiency syndrome (AIDS) were studied. In two heterosexual couples, transmission of lymphadenopathy-associated virus from a seropositive man at increased risk to his monogamous wife occurred. In one couple, the wife of a man with hemophilia had lymphadenopathy-associated virus antibody and decreased T helper cells; in the other couple, the wife of a bisexual intravenous drug-user had AIDS. Neither woman had a recognized AIDS risk except marriage to a seropositive man at increased risk. However, study of the other couples revealed that regular sexual contact with seropositive persons over long periods did not always lead to evidence of lymphadenopathy-associated virus infection. This study suggests that presence of lymphadenopathy-associated virus antibody does not always indicate a high degree of infectivity.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Transient antibody to lymphadenopathy-associated virus/human T-lymphotropic virus type III and T-lymphocyte abnormalities in the wife of a man who developed the acquired immunodeficiency syndrome.

We present evidence of transmission of lymphadenopathy-associated virus (LAV)/human T-lymphotropic virus type III (HTLV-III) from a man to his wife, and a return to a normal number of T-helper lymphocytes and loss of antibody after discontinuing sexual exposure to LAV/HTLV-III. The man had hemophilia A, and developed the lymphadenopathy syndrome, antibody to LAV, and a low number of T-helper lymphocytes. His wife, who had no risks for the acquired immunodeficiency syndrome other than sexual contact with him, developed LAV antibody (titer, 1:160) and a mildly decreased number of T-helper cells. The husband subsequently developed the syndrome and lost the LAV antibody. During 10 months of follow-up his wife remained clinically well, discontinued exposure to semen, and then lost the LAV antibody, and regained a normal number of T-helper cells.

Acquired Immunodeficiency Syndrome↗