First evidence of HIV infection of CD8 lymphocytes expressing CD4 during primary HIV-1 infection

Could CD4 capture by CD8+ T cells play a role in HIV spreading?

CD8(+) T cells have been shown to capture plasma membrane fragments from target cells expressing their cognate antigen, a process termed "trogocytosis". Here, we report that human CD4, the Human Immunodeficiency Virus (HIV) receptor, can be found among the proteins transferred by trogocytosis. CD4 is expressed in a correct orientation after its capture by CD8(+) T cells as shown by its detection using conformational antibodies and its ability to allow HIV binding on recipient CD8(+) T cells. Although we could not find direct evidence for infection of CD8(+) T cells having captured CD4 by HIV, CD4 was virologically functional on these cells as it conferred on them the ability to undergo syncytia formation induced by HIV-infected MOLT-4 cells. Our results show that acquisition of CD4 by CD8(+) T cells via trogocytosis could play a previously unappreciated role for CD8(+) T cells in HIV spreading possibly without leading to their infection.

HIV-1-infected CD8+CD4+ T cells decay in vivo at a similar rate to infected CD4 T cells during HAART

OBJECTIVES

To investigate the potential for CD4+CD8+ T cells [CD8 double positive (CD8 DP)] T cells to form a reservoir of HIV-1 following HAART through measurement of the rate of decay of infected CD4/CD8 DP T cells.

METHODS

HIV-1 proviral loads in highly pure CD4 and CD8 DP T cells were determined for study subjects before and after 200-400 days of therapy and HIV-1 DNA decay rates were calculated.

RESULTS

Before therapy, HIV-1 proviral load in CD8 DP correlated negatively with CD4 cell count. Decay rates of HIV-1-infected CD4 and CD8 DP T cells were similar. Rates for CD8 DP T cells correlated with the time to suppression of viral replication, whereas no such relationship was true for CD4 cell decay rates. A significant reduction in activated cells was observed for both cell types. The action of HAART on HIV-1 replication was similar for both CD4 cells and CD8 DP T cells, although the rate of clearance of infected CD8 DP T cells appeared more critical for a rapid reduction in plasma viral load. Although the size of the CD8 DP T cell reservoir in peripheral blood was smaller relative to that of CD4 cells, HAART did not completely clear HIV-1 infection from this cell subset.

CONCLUSION

This study confirmed that CD8 DP T cells are a major reservoir for HIV-1 in vivo and, therefore, represent a potential reservoir for HIV-1 during HAART, in a manner analogous to that of CD4 T cells.

Virus immunocapture provides evidence of CD8 lymphocyte-derived HIV-1 in vivo

OBJECTIVES

To demonstrate that HIV-1 immunocapture with an antibody against CD8 specifically captures virions derived from infected CD8 T cells, and to determine the proportion of HIV-1 derived from CD8 lymphocytes in plasma samples from HIV-infected individuals.

METHODS

A virus capture method was developed to enable the detection of HIV-1 virions based upon the presence of certain cell-specific host-derived proteins (CD8, CD3, CD36) within the viral envelope. HIV-1 virions were captured using antibodies against these proteins and levels of bound virus were determined by quantitative reverse transcriptase-polymerase chain reaction. Highly pure CD8 and CD3+CD8- T-cell cultures were used as in-vitro models to determine the specificity of the virus capture technique.

RESULTS

The in-vitro model demonstrates that incorporation of the CD8 molecule into released virions is specific to infection of CD8 T cells. Levels of HIV-1 immunocaptured from plasma of infected individuals using the anti-CD8 antibody indicate that up to 15% (range 10-33) of the plasma viral load is derived from CD8 lymphocytes.

CONCLUSION

This study demonstrates for the first time that HIV-1-infected CD8 T cells can contribute substantially to levels of circulating virus during the course of infection. Levels of CD8-derived virus did not correlate with the level of infection of circulating CD8 T cells, but do show a significantly good fit to plasma viral loads based on a power model. The extensive infection of CD8 T cells implied by these results may contribute towards immune dysfunction and disease progression to AIDS.

Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients

BACKGROUND

Various assays are used to enumerate peripheral blood absolute CD4+ T-lymphocytes. Flow cytometry is considered the gold standard for this purpose. However, the high cost of available flow cytometers and monoclonal antibody reagents make it difficult to implement such methods in the resource-poor settings. In this study, we evaluated a cheaper, recently developed single-platform microcapillary cytometer for CD4+ T-lymphocyte enumeration, the personal cell analyzer (PCA), from Guava Technologies.

METHODS

CD4+ and CD8+ T-lymphocyte counts in whole blood samples from 250 HIV-1 infected Thais were determined, using a two-color reagent kit and the Guava PCA, and compared with the results obtained with two reference microbead-based methods from Becton Dickinson Biosciences: the three-color TruCOUNT tube method and the two-color FACSCount method. Statistical correlations and agreements were determined using linear correlation and Bland-Altman analysis.

RESULTS

Absolute CD4+ T-lymphocyte counts obtained using the Guava PCA method highly correlated with those obtained using TruCOUNT method (R(2) = 0.95, mean bias +13.1 cells/microl, limit of agreement [LOA]-117.9 to +144.1 cells/microl) and the FACSCount method (R2 = 0.94, mean bias = +33.2 cells/microl, LOA-101.8 to +168.3 cells/microl). Absolute CD8+ T-lymphocyte counts obtained using the Guava PCA method also highly correlated with those obtained with the two reference methods (R(2) = 0.92 and 0.88, respectively).

CONCLUSION

This study shows that the enumeration of CD4+ T-lymphocytes using the Guava microcapillary cytometer PCA method performed well when compared with the two reference bead-based methods. However, like the two reference methods, this new method needs substantial technical expertise.