Methods for subtyping and molecular comparison of human viral genomes. (41/3874)

The development over the past two decades of molecular methods for manipulation of RNA and DNA has afforded molecular virologists the ability to study viral genomes in detail that has heretofore not been possible. There are many molecular techniques now available for typing and subtyping of viruses. The available methods include restriction fragment length polymorphism analysis, Southern blot analysis, oligonucleotide fingerprint analysis, reverse hybridization, DNA enzyme immunoassay, RNase protection analysis, single-strand conformation polymorphism analysis, heteroduplex mobility assay, nucleotide sequencing, and genome segment length polymorphism analysis. The methods have certain advantages and disadvantages which should be considered in their application to specific viruses or for specific purposes. These techniques are likely to become more widely used in the future for epidemiologic studies and for investigations into the pathophysiology of virus infections.  (+info)

Association of murine leukemia virus pol with virions, independent of Gag-Pol expression. (42/3874)

During the replication cycle of murine leukemia virus (MLV), Pol is normally synthesized as part of a Gag-Pol fusion protein. In this study, the ability of free MLV Pol to be incorporated into virions was examined. When MLV Gag and MLV Pol were coexpressed from separate plasmids in cells, reverse transcriptase (RT) activity associated with Gag core particles at a slightly lower level than did RT activity generated from wild-type Gag-Pol expression. Particles produced in this manner were somewhat less infectious than those produced with wild-type Gag-Pol. A smaller amount of MLV Pol also associated with heterologous human immunodeficiency virus type 1 Gag cores.  (+info)

The trophoblastic epithelial barrier is not infected in full-term placentae of human immunodeficiency virus-seropositive mothers undergoing antiretroviral therapy. (43/3874)

To study the mechanism of the placental barrier function, we examined 10 matched samples of term placentae, cord blood, and maternal blood obtained at delivery from human immunodeficiency virus (HIV)-infected mothers with children diagnosed as HIV negative in Sweden. All placentae were histologically normal, and immunochemistry for HIV type 1 p24 and gp120 antigens was negative. Highly purified trophoblasts (93 to 99% purity) were negative for HIV DNA and RNA, indicating that the trophoblasts were uninfected. Although HIV DNA was detected in placenta-derived T lymphocytes and monocytes, microsatellite analysis showed that these cells were a mixture of maternal and fetal cells. Our study indicates that the placental barrier, i.e., the trophoblastic layer, is not HIV infected and, consequently, HIV infection of the fetus is likely to occur through other routes, such as breaks in the placental barrier.  (+info)

Productive infection of double-negative T cells with HIV in vivo. (44/3874)

HIV induces CD4 down-regulation from the surface of infected cells by several independent mechanisms, suggesting an important biological role for this phenomenon. In vitro CD4 down-regulation generates T cells with a double-negative (DN) CD4(-)CD8(-) T cell receptor-alphabeta(+) phenotype. However, evidence that this down-regulation occurs in vivo in HIV-infected subjects is lacking, and viral load or viral production assays invariably focus on CD4(+) T cells. We show here that HIV infection can often be detected in sorted DN cells from peripheral blood and lymph nodes, even when plasma viral load is undetectable. DN T cells infected with HIV represented up to 20% of the cellular viral load in T cells, as determined by DNA PCR. In patients on successful highly active antiretroviral therapy, the viral load decreased in the plasma in CD4(+) and in DN T cells, suggesting that infected DN cells, like CD4(+) cells, contribute to viral production and are sensitive to highly active antiretroviral therapy. Indeed, HIV unspliced and multispliced RNAs were often detectable in DN T cells in spite of the small size of this subset. Infectious virus from DN T cells was transmitted efficiently in coculture experiments with uninfected T cell lymphoblasts, even when viral DNA in the DN cells was barely detectable. We conclude that a discrete population of infected DN T cells exists in HIV-positive subjects, even when the plasma viral load is undetectable. These cells may represent an important source of infectious virus.  (+info)

Trafficking of the HIV coreceptor CXCR4. Role of arrestins and identification of residues in the c-terminal tail that mediate receptor internalization. (45/3874)

The G protein-coupled chemokine receptor CXCR4 serves as the primary coreceptor for entry of T-cell tropic human immunodeficiency virus. CXCR4 undergoes tonic internalization as well as internalization in response to stimulation with phorbol esters and ligand (SDF-1alpha). We investigated the trafficking of this receptor, and we attempted to define the residues of CXCR4 that were critical for receptor internalization. In both COS-1 and HEK-293 cells transiently overexpressing CXCR4, SDF-1alpha and phorbol esters (PMA) promoted rapid internalization of cell surface receptors as assessed by both enzyme-linked immunosorbent assay and immunofluorescence analysis. Expression of GRK2 and/or arrestins promoted modest additional CXCR4 internalization in response to both PMA and SDF. Both PMA- and SDF-mediated CXCR4 internalization was inhibited by coexpression of dominant negative mutants of dynamin-1 and arrestin-3. Arrestin was also recruited to the plasma membrane and appeared to colocalize with internalized receptors in response to SDF but not PMA. We then evaluated the ability of CXCR4 receptors containing mutations of serines and threonines, as well as a dileucine motif, within the C-terminal tail to be internalized and phosphorylated in response to either PMA or SDF-1alpha. This analysis showed that multiple residues within the CXCR4 C-terminal tail appear to mediate both PMA- and SDF-1alpha-mediated receptor internalization. The ability of coexpressed GRK2 and arrestins to promote internalization of the CXCR4 mutants revealed distinct differences between respective mutants and suggested that the integrity of the dileucine motif (Ile-328 and Leu-329) and serines 324, 325, 338, and 339 are critical for receptor internalization.  (+info)

A theoretical model of the evolution of virulence in sexually transmitted HIV/AIDS. (46/3874)

INTRODUCTION: The evolution of virulence in host-parasite relationships has been the subject of several publications. In the case of HIV virulence, some authors suggest that the evolution of HIV virulence correlates with the rate of acquisition of new sexual partners. In contrast some other authors argue that the level of HIV virulence is independent of the sexual activity of the host population. METHODS: Provide a mathematical model for the study of the potential influence of human sexual behaviour on the evolution of virulence of HIV is provided. RESULTS: The results indicated that, when the probability of acquisition of infection is a function both of the sexual activity and of the virulence level of HIV strains, the evolution of HIV virulence correlates positively with the rate of acquisition of new sexual partners. CONCLUSION: It is concluded that in the case of a host population with a low (high) rate of exchange of sexual partners the evolution of HIV virulence is such that the less (more) virulent strain prevails.  (+info)

Seroprevalence of retroviral infections among pregnant women in Martinique (French West Indies). (47/3874)

A seroepidemiologic study of human T cell lymphotrophic virus type-1 (HTLV-1) and human immunodeficiency virus (HIV) infections was carried out in Martinique among 467 pregnant women receiving prenatal care at the Martinique Department for the Protection of Motherhood and Childhood. A seroprevalence rate of 1.93% was found for HTLV-1 infection. No HIV serum marker was observed. Given the epidemiology of these viral diseases, it is suggested that serologic status should be determined for all pregnant women on this island. A further, large-scale, prospective survey of HIV seroprevalence in Martinique should be performed to confirm the results of the present study.  (+info)

Increase in hepatitis C virus load in hemophiliacs during treatment with highly active antiretroviral therapy. (48/3874)

The effect of highly active antiretroviral therapy (HAART) on liver function and viral load of hepatitis C virus (HCV) was studied in 21 hemophilic men coinfected with HCV and human immunodeficiency virus (HIV). HCV RNA polymerase chain reaction was measured by branched DNA Quantiplex assay on frozen plasma samples obtained at baseline and at 24, 48, and 96 weeks after initiation of HAART. HCV RNA increased at 48 and 96 weeks after initiation of HAART therapy (198x105 Eq/mL [P=.03] and 227x105 Eq/mL [P<.0001], respectively, compared with baseline [141x105 Eq/mL]). This increase was associated with an increase in CD4 cell count and reduction in HIV viral load but no change in hepatic transaminases. With discontinuation of HAART, HCV RNA decreased as HIV RNA rebounded. Further study is required to clarify the histopathologic significance of this finding.  (+info)