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Biomedical subjects

V Liska

Publications and source records attributed to V Liska.

At least 37 records · Page 2Linked to original sources
PubMed1999

Oral transmission of primate lentiviruses.

Oral transmission of human immunodeficiency virus type 1 (HIV-1) is well documented in children who become infected postnatally through breast milk. In contrast, epidemiologic surveys have yielded conflicting data regarding oral HIV-1 transmission among adults, even though case reports have described seroconversion and the development of AIDS in adults whose only risk was oral-genital contact. To study oral virus transmission in primate models, we exposed rhesus macaques of various ages to cell-free simian immunodeficiency virus (SIV), including uncloned and molecularly cloned viruses. In neonates, viremia and AIDS developed after nontraumatic oral exposure to several SIV strains. Furthermore, chimeric simian human immunodeficiency viruses containing the HIV-1 envelope can also cross intact upper gastrointestinal mucosal surfaces in neonates. In adult macaques, infection and AIDS have resulted from well-controlled, nontraumatic, experimental oral exposure to different strains of SIV. These findings have implications for the risks of HIV-1 transmission during oral-genital contact.

Age Factors↗
PubMed1999

Persistent infection of rhesus macaques by the rev-independent Nef(-) simian immunodeficiency virus SIVmac239: replication kinetics and genomic stability.

We generated previously a Nef(-), replication-competent clone of SIVmac239 in which the Rev protein and the Rev-responsive element were replaced by the constitutive transport element (CTE) of simian retrovirus type 1 (A. S. von Gegerfelt and B. K. Felber, Virology 232:291-299, 1997). In the present report, we show that this virus was able to infect and replicate in rhesus macaques. The Rev-independent Nef(-) simian immunodeficiency virus induced a persistent humoral immune response in all monkeys, although viral loads were very low. Upon propagation in the monkeys, the genotype remained stable and the virus retained its in vitro growth characteristics. The infected monkeys showed normal hematological values and no signs of disease at more than 18 months post-virus exposure. Therefore, replacement of the essential Rev regulation by the CTE generated a virus variant that retained its replicative capacity both in vitro and in vivo, albeit at low levels.

Animals↗
PubMed1999

[Contrast sensitivity in type I diabetics without symptoms of diabetic retinopathy].

UNLABELLED: The objective of the work was to assess whether in patients with IDDM without signs of diabetic retinopathy changes in the sensitivity function to contrast (CS) develop as compared with a group of healthy subjects matched for age but also as a result of the persistence of IDDM or the level of its long-term compensation investigated by means of glycated haemoglobin (HbA1c). CS was examined by the static method using a VCTS 6500 table from a distance of 208 and 420 cm which covered the spatial frequencies from 1.15 to 27.25 c/st. Moreover the authors assessed the best correctable central visual acuity on Snellen's optotypes, the ophthalmoscopic finding on the fundus with a colour photograph, fluorescein angiography and the HbA1c serum level. A group of 49 patients with IDDM was divided into two age groups: A(under 35 years), B (35 years and above). A marked decline of the CS function occurs in all spatial frequencies in both age groups. On comparison of the persistence of IDDM in group B no significant difference was found in CS, while in group A statistical significance was revealed in spatial frequencies 4 and 27.25 c/st. On comparison of the CS function in diabetics with a normal and pathological HbA1c level it was found that long-term hyperglycaemia has not a marked effect on visual functions. CONCLUSION: The decline of CS in patients with IDDM without signs of diabetic retinopathy is influenced in particular by the patient's age, in junior patients also by the persistence of IDDM. Examination of the CS is a simple non-invasive method suitable for screening of early affections of the eyes in IDDM.

Adult↗
PubMed1999

Are contrast sensitivity functions impaired in insulin dependent diabetics without diabetic retinopathy?

PURPOSE: To confirm the influence of multilevel metabolic disturbance of insulin dependent diabetes mellitus (IDDM) on the vision even before the onset of the other changes routinely evaluated by ophthalmologists. METHODS: Contrast sensitivity functions (CSFs) were estimated using the VCTS 6500 board. The standardised measurement procedure was performed. The value of the threshold contrast sensitivity was obtained for five spatial frequencies (1.5-3-6-12-18 c/deg). Other data was collected (duration of diabetes, BCVA, funduscopy, fluoresceine angiography, HbA1C). The study group consisted of 48 IDDM patients (94 eyes) without diabetic retinopathy and with Snellen BCVA > 1.0. The control group (56 normals, 98 eyes) was age and BCVA matched. RESULTS: Highly statistically significant decrease of the CSFs in all spatial frequencies in the study group was obtained. Correlation between duration of the diabetes and impaired degree of CSFs was present in the middle spatial frequency. No significant changes in CSFs were found among patients with pathological value of glycated hemoglobin HbA1c (> 7.8%). CONCLUSIONS: If compared with routinely used Snellen visual acuity, the CSFs are more complex descriptors of the subjects vision abilities. IDDM has an influence on these sensitive functions, especially during examination in the middle spatial frequency of 6 and 12 c/deg, before disturbing visual acuity and before changes in the retinal morphology. Decrease of CSFs was influenced mainly by the patients' age and partially (in the middle spatial frequency) by the IDDM duration.

Adult↗
PubMed1998

Oral SIV, SHIV, and HIV type 1 infection.

Several strains of simian immunodeficiency virus (SIV), including uncloned and molecularly cloned SIV strains, can cross intact mucosal surfaces after oral exposure in both adult and neonatal rhesus macaques, resulting in viremia and disease. Cell-free SIV strains as well as infected whole blood have resulted in systemic infection after oral inoculation. Neonatal macaques, exposed orally to the chimeric SHIV-vpu+, a derivative of SIVmac239 that encodes the env gene of the T cell-tropic HIV-IIIB, have also become persistently infected. These data indicate that oral exposure to various virus strains, including T cell-tropic variants, leads to infection. After nontraumatic inoculation, the oral route was more efficient than the rectal route in permitting SIV entry in adult macaques. Infection and AIDS resulting from oral exposure of adult macaques have implications for the transmission of the human immunodeficiency virus type 1 (HIV-1) during oral-genital contact.

AIDS Vaccines↗
PubMed1998

[Contrast sensitivity in glaucoma and ocular hypertension].

It is known that contrast sensitivity declines with advancinG age and during different ophthalmological diseases. The authors examined 263 eyes of 141 patients with different types of glaucoma and 213 eyes of 107 patients with ocular hypertension. The patients were divided into two groups by age: A = under 60 years (mean 53.2 in glaucoma, 51.1 in OH) and B = 60 years and above (mean 67.5 in glaucoma and 65.6 in OH). For examination of contrast sensitivity the authors used a VCTS 6500 board from a 3 m distance, the visual field was examined by means of Goldman's kinetic perimeter or a static Optifield II perimeter and the discs of the optic nerve were examined biomicroscopically or a photograph of the disc was taken. Impaired contrast sensitivity was found in group A in 71.7% of glaucoma patients and in 61.6% in ocular hypertension. In group B in 81.7% glaucoma patients and in 75.1% of patients with ocular hypertension. The authors also proved an association between the decline of contrast sensitivity and impairment of the perimeter and enlargement of the glaucoma excavation of the optic disc. The authors recommend examination of the contrast sensitivity as a supplementary method for screening and observation of ocular hypertension and glaucoma.

Aged↗
PubMed1997

Detection of simian T cell leukemia virus type I infection in seronegative macaques.

Simian species of Asian and African origin are naturally infected with the simian T cell leukemia virus type I (STLV-I). Like the closely related human T cell leukemia virus type I (HTLV-I), STLV-I is primarily cell associated, and typical infections exhibit low viral burdens. Four macaques experimentally inoculated with a new STLV-I strain isolated from a sooty mangabey monkey were examined over extended periods of time for signs of infection by (1) commercial enzyme immunoassay and immunoblot assay for cross-reactive serum antibodies to HTLV-I, (2) commercial HTLV-I p24gag antigen-capture assay on supernatants from cocultures of macaque peripheral blood mononuclear cells (PBMCs) with human PBMCs, and (3) nested PCR amplification of proviral sequences in macaque PBMC DNA. The nested PCR assay was 100% specific and detected a single STLV-I copy in 150,000 PBMCs. In addition, our data show that experimental infection of macaques with STLV-I can be serologically silent for more than 43 months.

Animals↗
PubMed1997

Simultaneous detection of simian retrovirus type D serotypes 1, 2, and 3 by polymerase chain reaction.

Asymptomatic infection of macaques with macaques with simian retroviruses type D (SRV/D), the etiologic agents of one form of retrovirus-induced simian immunodeficiency disease, can confound experiments with the simian immunodeficiency virus (SIV), which also induces immunodeficiency disease in macaques. The SIV/macaque model is the preferred nonhuman primate model for AIDS-related research. Serological screening for SRV/D alone is insufficient because not all infected animals seroconvert, and virus isolation by cocultivation may require 4 to 6 weeks. We have established a DNA polymerase chain reaction (PCR) assay. One set of nested primers allows detection of SRV/D serotypes 1, 2, and 3 and distinguishes SRV-2 from the other two serotypes. The PCR assay is sensitive; a single proviral copy of SRV/D could be detected in 150,000 to 210,000 macaque peripheral blood mononuclear cells (PBMCs). When applied to a panel of virus isolation-positive macaque samples, the PCR assay was positive in 100% of the tests. No false-positive results were seen when known specific-pathogen-free (SPF) macaques were examined. We propose that macaques be screened with a combination of SRV/D serology and this DNA PCR assay prior to enrollment in experiments with SIV.

Animals↗
PubMed1997

[Marfan syndrome].

The author describes three forms of Marfan's syndrome which have only the skeletal symptoms in common. In all instances also ophthalmological symptoms are present but of different types. A familial case was observed only in one family; in the remaining two frust forms of Marfan's syndrome are involved.

Adult↗
PubMed1996

Infection and AIDS in adult macaques after nontraumatic oral exposure to cell-free SIV.

Unprotected receptive anal intercourse is a well-recognized risk factor for infection with human immunodeficiency virus-type 1 (HIV-1). Isolated human case reports have implicated HIV-1 transmission by oral-genital exposure. Adult macaques exposed nontraumatically to cell-free simian immunodeficiency virus (SIV) through the oral route became infected and developed acquired immunodeficiency syndrome (AIDS). The minimal virus dose needed to achieve systemic infection after oral exposure was 6000 times lower than the minimal dose required to achieve systemic infection after rectal exposure. Thus, unprotected receptive oral intercourse, even in the absence of mucosal lesions, should be added to the list of risk behaviors for HIV-1 transmission.

Animals↗
PubMed1995

Presence of virion protein x (Vpx) of simian immunodeficiency virus SIVmac 251 in target cells in vivo.

Localization of virion-associated protein x (Vpx) of SIVmac 251 was studied in lymph nodes and liver of six SIVmac-infected monkeys. Vpx was found associated with the network of follicular dendritic cells and macrophages in lymph nodes and/or livers from five out of six animals by immunohistochemistry. Although the humoral response to Vpx occurs in only 50% of the animals, the presence of Vpx in target cell or antibodies to Vpx in all the monkeys studied, suggests that Vpx may be necessary for viral replication in vivo.

Animals↗
PubMed1994

Production and simple purification of a protein encoded by part of the gag gene of HIV-1 in the Escherichia coli HB101F+ expression system inducible by lactose and isopropyl-beta-D-thiogalactopyranoside.

The development of the Escherichia coli expression system, which was prepared by transferring the F' episome from strain 71/18 to a highly to a transformable F- strain HB101, is described. These new HB101 (F+) cells, which produced high levels of lac repressor, were capable of taking up lactose and grew under strict selection conditions. A relatively simple two-step purification of part of a protein (M(r) 27,000) encoded by the gag gene of HIV-1 in this expression system is described. The supernatant prepared by removal of cell debris was precipitated by 30% saturation of ammonium sulphate. The protein spectrum was characterized by gel electrophoresis, immunoblotting and ion-exchange titration curves. Optimum separation was achieved using a strong anion exchanger (Mono Q) at pH 8.0. The purified protein did not cross-react with antibodies to E. coli.

Antibodies, Bacterial↗
PubMed1994

Localization of viral protein X in simian immunodeficiency virus macaque strain and analysis of its packaging requirements.

Simian immunodeficiency virus (SIV) and human immunodeficiency virus type 2 (HIV-2) encode the accessory viral protein X (Vpx) known to be incorporated into virions in amounts comparable to those of the Gag proteins. The localization of Vpx within SIVmac-infected HUT-78 cells and SIVmac virions was studied by immunoelectron microscopy. Vpx appeared to be associated with extracellular virions as well as budding viral particles at the surface of infected cells. Immunolabelling of purified viral cores suggested that Vpx was a component of the amorphous material surrounding the core structure. Furthermore, a detergent insoluble fraction containing SIV core proteins was devoid of Vpx. To investigate the protein requirement for packaging of Vpx, BHK-21 cells were co-infected with vaccinia virus recombinants encoding Vpx and other SIV proteins able to assemble into virus-like particles. Analysis by immunoprecipitation of the extracellular particulate material as well as immunoelectron microscopy demonstrated that co-expression of Vpx with the Pr56gag polyprotein was sufficient for the formation of pseudo-virions containing Vpx. Virus-like particles that appeared upon expression of p16gag did not contain Vpx. The results suggest that Vpx is packaged into viral particles through its binding to the Gag polyprotein. The precise positioning of Vpx within the space separating the viral envelope from the core structure is postulated to result from the reorganization of viral proteins that occurs upon Gag polyprotein cleavage and budding.

Animals↗