The acquisition of host-derived major histocompatibility complex class II glycoproteins by human immunodeficiency virus type 1 accelerates the process of virus entry and infection in human T-lymphoid cells.

Infection by human immunodeficiency virus type 1 (HIV-1) results in a progressive depletion of CD4+ T lymphocytes, leading to fatal immunodeficiency. The mechanisms causing the marked loss of CD4+ T lymphocytes are incompletely understood. However, several lines of evidence indicate that direct cytopathology mediated by HIV-1 is a key element in such CD4+ T-cell depletion. In this study, we investigated whether the previously reported incorporation of host-derived major histocompatibility class II glycoproteins (MHC-II) on HIV-1 can alter its replicative capacity. To achieve this goal, virus stocks were produced in parental MHC-II-expressing RAJI cells and in MHC-II-negative RAJI mutants (RM3), both of which have been stably transfected with human CD4 cDNA to allow productive infection with HIV-1. An enhancement of the rate/efficiency of virus entry was seen after infection with normalized amounts of virions carrying host-derived MHC-II on their surface as compared with inoculation with virions devoid of cellular MHC-II. Data from time-course and infectivity experiments showed that the kinetics of infection were more rapid for virions bearing host-derived MHC-II glycoproteins than for MHC-II-free HIV-1 particles. These results suggest that virally embedded cellular MHC-II glycoproteins are functional and can have a positive effect on early events in the virus replicative cycle. Therefore, we show that the acquisition of cellular MHC-II glycoproteins by HIV-1 can modify its biologic properties and might, consequently, influence the pathogenesis of this retroviral disease.

Host-derived ICAM-1 glycoproteins incorporated on human immunodeficiency virus type 1 are biologically active and enhance viral infectivity.

Human immunodeficiency virus type 1 (HIV-1) acquires several host cell membrane proteins when it buds from infected cells. To study the effect of virally incorporated host-derived ICAM-1 glycoproteins on the biology of HIV-1, we have developed a transient expression system that has enabled us to produce virus particles differing only in the absence or the presence of virion-bound ICAM-1. By using a single-round infection assay based on an ICAM-1-negative target T-cell line stably transfected with an HIV-1 long terminal repeat driven luciferase gene construct, we have been able to demonstrate that the acquisition of host-derived ICAM-1 by HIV-1 has functional significance, since it leads to a pronounced increase in viral infectivity (4.6- to 9.8-fold) in an ICAM-1/LFA-1-dependent fashion, as shown by blocking with anti-ICAM-1 and -LFA-1 antibodies. The same potentiating effect on viral infectivity was also observed with monocytoid cells. Studies of the kinetics of infection revealed that the positive effect mediated by virally embedded host cell membrane ICAM-1 is due to an increase in the efficiency of early steps in the viral life cycle. These results provide new insights into how incorporation of host proteins can modulate the biological properties of HIV-1. Our findings have direct clinical relevance, considering that ICAM-1 is expressed on the surface of virus-infected cells and, more importantly, that host-derived ICAM-1 has been shown to be acquired by clinical HIV-1 isolates grown on primary mononuclear cells. These data justify a more complete analysis of the other putative role(s) that virally incorporated ICAM-1 may play in the life cycle of HIV-1, for example, at the level of neutralization sensitivity.

The presence of host-derived HLA-DR1 on human immunodeficiency virus type 1 increases viral infectivity.

Human immunodeficiency virus type 1 (HIV-1) incorporates several host cell components when budding out of the infected cell. One of the most abundant host-derived molecules acquired by HIV-1 is the HLA-DR determinant of the major histocompatibility complex class II (MHC-II) molecules. The fact that CD4 is the natural ligand of MHC-II prompted us to determine if such virally embedded cellular components can affect the biology of the virus. Herein, we report for the first time that the incorporation of cellular HLA-DR1 within HIV-1 enhances its infectivity. This observation was made possible with virions bearing or not bearing on their surfaces host-derived HLA-DR1 glycoproteins. Such virus stocks were prepared by a transient-expression system based on transfection of 293T cells with a recombinant luciferase-encoding HIV-1 molecular clone along with plasmids encoding the alpha and beta chains of HLA-DR1. Cell-free virions recovered from transfected cells were shown to have efficiently incorporated host-derived HLA-DR1 glycoproteins. Infectivity was increased by a factor of 1.6 to 2.3 for virions bearing on their surfaces host-derived HLA-DR1. The observed enhancement of HIV-1 infectivity was independent of the virus stocks used and was seen in several T-lymphoid cell lines, in a premonocytoid cell line, and in primary peripheral blood mononuclear cells. Finally, we determined that the presence of virion-bound cellular HLA-DR1 is associated with faster kinetics of virus infection. Taken together, these results suggest that HLA-DR-1-bearing HIV-1 particles had a greater infectivity per picogram of viral p24 protein than HLA-DR1-free virions.

PCR-based analysis of voltage-gated K+ channels in vascular smooth muscle.

Irregularities in K+ currents form the basis of several cardiovascular dysfunctions, among which are arrhythmias and vasospasms. The developmental regulation of voltage-gated K+ channels, however, has been difficult to study. A novel approach was therefore employed to examine these channels in muscle tissue. Primers for a PCR-based analysis were designed using published nucleic acid sequences for voltage-gated K+ channels. Final selection of the primer pairs was based on the homology present in the S4 and H5 transmembrane domains. A specific band was amplified with these primers using RNA isolated from both rat A10 vascular smooth muscle cells and rat heart tissue.

A comparison study of the EF-18 agar/Hydrophobic Grid Membrane Filter (HGMF) method and the enzyme linked antibody (ELA)/HGMF method to the HPB standard method in the isolation of Salmonella.

As part of a comparative and collaborative study of rapid methods for the detection of Salmonella and the standard Health Protection Branch (HPB) method, six Federal and Provincial Laboratories compared the EF-18 agar/Hydrophobic Grid Membrane Filters (HGMF) method to the standard HPB method. Two Federal Laboratories also compared the enzyme linked antibody (ELA)/HGMF method (which is a further development of the EF-18 agar/HGMF method) to the standard method. During this study the false-negative rates ranged from 0% to 15% for the standard HPB method, from 5.88% to 43.5% for the EF-18 agar/HGMF method, and from 0% to 10.5% for the ELA/HGMF method. The EF-18 agar/HGMF method did not compare well with the standard HPB method due to the number of false-negatives. Problems with this method resulted from the inability to isolate colonies of Salmonella on the HGMF due to the small colony size, abnormal colony coloration, and overgrowth by competitors. The ELA/HGMF method, however, was shown to be comparable to the standard HPB method. The main advantages of this method are that the antibody-staining step is independent of colony coloration and carbohydrate utilization on the plating media; the ability to detect some unusual strains of Salmonella irrespective of their atypical reactions on the media; and the ELA staining can indicate the presence of Salmonella even when the HGMF is overgrown by competitors. Also, cultural confirmation can proceed simultaneously yet independently of the ELA staining procedure. The data presented here indicate that this method is worth further study.