CD7 expression distinguishes subsets of CD4(+) T cells with distinct functional properties and ability to support replication of HIV-1.

Enrichment of a subset of CD4(+)CD45R0(+)CD7(-) T cells has been observed in HIV-infected individuals. We have investigated the ability of CD7(+) and CD7(-) T cells to support replication of HIV and show that virus replicates preferentially in CD7(+) cells. Several possible mechanisms that may underlie such differences in susceptibility to HIV were studied. Our data demonstrate that mitogen stimulation induces poor expression of CD25 and IL-2 in CD7(-) compared with CD7(+) cells. We also show that uninfected CD7(-) cells are more resistant to mitogen-induced apoptosis than CD7(+) cells. Our data support the view that the CD7(-) subset is inherently resistant to HIV replication and that this is due in part to reduced CD25 expression and IL-2 production.

HIV infection alters the production of both type 1 and 2 cytokines but does not induce a polarized type 1 or 2 state.

OBJECTIVE: To test the T-helper (TH)1/TH2 cytokine paradigm in HIV infection. DESIGN AND METHODS: Cytokine profiles in two separate studies of HIV patients and controls are presented: (i) a longitudinal study of HIV patients with CD4 counts > 500 x 10(6)/l tested at three timepoints compared with controls; (ii) a blinded cross-sectional study of controls and patients with high (> 500 x 10(6)/l) and low (< 500 x 10(6)/l) CD4 counts. Peripheral blood mononuclear cells (PBMC) from patients and controls were tested for the production of two type 1 [interleukin (IL)-2, interferon (IFN)-gamma] and two type 2 (IL-4, IL-10) cytokines by enzyme-linked immunosorbent assay. Both spontaneous and mitogen-induced cytokine production was measured. RESULTS: HIV infection was noted to have the following effects on cytokine production: (i) it led to the in vivo activation of type 2 cytokines in a small group of individuals with high CD4 numbers characterized by the spontaneous release of IL-4 and IL-10. Longitudinal data showed high spontaneous IL-4 and IL-10 to be a consistent feature of the patient group (at each timepoint some patients were high producers) but to be variable in a given individual; (ii) HIV infection impaired the ability of PBMC to respond to stimuli (selected for their ability to optimally induce each cytokine) in terms of IL-2, IL-4 and IL-10 production in patients with both high and low CD4 cell counts; and (iii) conversely, HIV infection led to an overproduction of IFN-gamma in patients with high CD4 counts; patients with low CD4 produced normal levels of IFN-gamma. CONCLUSIONS: Our observations did not suggest polarization of the type 1/type 2 cytokine profile in HIV patients. Instead, the data suggested more complex changes to type 1/type 2 cytokine patterns in HIV infection than originally proposed by the TH1/TH2 dichotomy.

Th1 cells specific for HIV-1 gag p24 are less efficient than Th0 cells in supporting HIV replication, and inhibit virus replication in Th0 cells.

This report provides three lines of evidence to suggest that T-helper type 1 (Th1) and type 0 (Th0) cells could play an opposing role in acquired immune deficiency syndrome (AIDS). Using a panel of Th1 and Th0 clones specific for human immunodeficiency virus-1 (HIV-1) gag p24, derived from seronegative volunteers immunized with gag p24: Ty virus-like particles, a Th1 clone specific for tuberculin (PPD), and a Th0 clone derived by random activation from the same volunteer, we have demonstrated the following differences in the capacity of these clones to regulate the in vitro replication of HIV. (1) Th1 clones were less efficient than Th0 clones in supporting HIV replication, both in their resting state (by 10-1000-fold) and after antigen activation (by five to 100-fold). Furthermore, the infectious titre of HIV recovered from the Th0 population was more than 1000-fold higher than virus from the Th1 population, and the number of HIV-infected Th0 cells was five to 16 times higher than the number of infected Th1 cells. (2) Antigen- or mitogen-activated Th1, but not Th0 clones, inhibited HIV in bystander CEM-4 cells. Th1 cells also inhibited HIV in autologous and allogeneic Th0 cells. The level of inhibition in these experiments ranged from 50% to 100% and was three to 10-fold higher and more sustained in the presence of p24-specific clones compared to the PPD-specific Th1 clone. The capacity of Th1 cells to inhibit HIV in neighbouring cells was also reflected in the reduced replication of HIV in the clones immediately after antigen activation compared to unstimulated cells. Kinetic studies of virus production, cytokine release and proliferation showed that inhibition of HIV was associated with peak cytokine release and preceeded proliferation. (3) The Th1 clones had higher cytolytic potential than the Th0 clones. Therefore, the HIV inhibitory activity of Th1 cells could be partly due to cell to cell killing. These data demonstrate the opposing effects of Th1 and Th0 cells on the in vitro replication of HIV, and suggest that Th1 cells might be important in immunity whereas Th0/Th2 cells might lay a role in promoting disease.

HIV-1 infection of human CD4+ T cells in vitro. Differential induction of apoptosis in these cells.

The H9 and CEM CD4+ T cell lines were infected with HIV-1 (NY5/LAV-1 isolate) and monitored for losses in cell viability, syncytium formation, and internucleosomal DNA cleavage (a marker for apoptosis). H9 cells were found to undergo cell death via apoptosis as a result of HIVNY5 infection, but this effect was not apparent in CEM cell cultures. The differential effects of HIV-1NY5 in terms of its apoptosis-inducing properties correlated with the relative abilities of H9 and CEM cells in supporting replication of this HIV-1 isolate, since infected CEM cell cultures produced 10-fold lower levels of HIV-1 p24 protein, and very few of these cells stained positive for cell-associated p24 by comparison with H9 cell cultures infected at the same multiplicity of infection. Furthermore, a different HIV-1 isolate (RF), which replicated equally efficiently in both H9 and CEM cells, produced similar levels of apoptosis in these cultures. HIV-1NY5 was also found to be capable of inducing apoptosis in purified peripheral blood CD4+ T cells as well as inhibiting anti-CD3-driven proliferation of these cells. In contrast, incubation of purified CD8+ T cells with HIV-1NY5 under similar conditions produced no cytopathic effects. Substantial levels of apoptosis were also recorded in HIV-1NY5-infected PHA blasts cell cultures. Soluble rHIV-1IIIB type CHO-derived gp120 was found to mimic the effects of HIV in terms of inhibition of anti-CD3/TCR mAb-induced proliferation of T cells, but apoptosis was not detected in gp120-treated T cell cultures whether cross-linked or used in conjunction with anti-CD3 mAb or not. We conclude therefore that both HIV-1NY5 and HIV-1RF isolates have the capacity to directly trigger apoptotic cell death in CD4+ T cells and that this appears to be at least partly associated with the efficiency of virus replication in these cells.

Immunization of human HIV-seronegative volunteers with recombinant p17/p24:Ty virus-like particles elicits HIV-1 p24-specific cellular and humoral immune responses.

OBJECTIVE: To evaluate the immune response to HIV-1 p24 generated in vivo by p17/p24:Ty virus-like particles (p17/p24:Ty-VLP) by examining the lymphoproliferative and antibody (Ab) responses to HIV-1 p24, as well as Gag-specific cytotoxic T lymphocytes (CTL), in HIV-seronegative volunteers immunized with hybrid p17/p24:Ty-VLP. DESIGN AND METHODS: Sixteen HIV-seronegative volunteers were immunized with p17/p24:Ty-VLP at two dose levels (100 or 500 micrograms) and monitored for the following 48 weeks for production of anti-p24 and anti-p17 Ab, in vitro lymphoproliferative responses to HIV-1 p24 and p17, and in vitro CTL responses to HIV-1 Gag. RESULTS: Twelve out of the 16 volunteers had significant p24-specific proliferative responses, with volunteers on the higher dose schedule exhibiting earlier proliferative responses than those on the lower dose schedule. Proliferative responses in both volunteer groups were similar in overall magnitude but appeared at different times during the immunization schedule. Anti-p24 Ab were detected in six out of the nine individuals in the lower dose group and in five out of the seven in the higher dose group. There was a good correlation between the presence of p24-specific Ab and the detection of lymphoproliferative responses to the p24 protein in peripheral blood mononuclear cells isolated from the same individuals. Anti-p17 Ab were detected in five volunteers. No Gag-specific CTL responses were detected. CONCLUSION: We conclude that hybrid HIV-1 p17/p24:Ty-VLP are capable of inducing both cellular and humoral immunity to HIV-1 Gag p17 and p24 components and are worthy of further study as a potential HIV immunotherapeutic.

Langerhans cell distribution and keratinocyte expression of HLADR in oral lichen planus.

Keratinocyte expression of the Class II major histocompatibility complex antigen HLADR, is seen in several inflammatory disorders of skin and mucosa, including lichen planus. The purpose of this study is to determine whether the distribution of Langerhans cells and their expression of CD4 in oral lichen planus is related to keratinocyte HLADR. The numbers of CD1- and CD4-positive Langerhans cells were compared in areas of keratinocyte HLADR and areas showing no expression in oral lichen planus and with normal oral mucosa. Cells were identified using an immunoalkaline phosphatase technique and numbers were expressed per mm epithelial surface length. In lichen planus, an increase both in the number of Langerhans cells and the numbers expressing CD4 were found in areas of keratinocyte HLADR expression compared with HLADR negative areas and with normal oral mucosa. There was no difference in the numbers of Langerhans cells or their expression of CD4 between HLADR-negative areas in LP and normal oral mucosa. These results show that the distribution of Langerhans cells is related to keratinocyte expression of HLADR and suggest that Langerhans cell entry may be enhanced in these areas. Whilst it is possible this enhancement is mediated by CD4/HLADR interaction, other molecules are also likely to be important in controlling Langerhans cell entry into oral mucosa.

T cell responses to peptides covering the gag p24 region of HIV-1 occur in HIV-1 seronegative individuals.

We demonstrate that peptides (16 amino acids long) covering the sequence of the HIV-1 core protein p24 induce significant proliferation in peripheral blood mononuclear cells (PBMC) of several (greater than 50%) healthy seronegative volunteers as well as seronegative homosexual men. The nature of this response was characterized and compared with those of HIV-infected patients. Several peptides induced responses; however, the most frequent responses in both seropositive and seronegative individuals were noted to the following peptides: 1 and 2 (aa 133-157); 6 and 7 (aa 183-207); 15 (aa 273-287); and 17 and 18 (aa 293-317). The response pattern was related to the disease stage of the patients; seronegative individuals as well as asymptomatic seropositive individuals (CDC II/III) responded to low concentrations of several peptides, but symptomatic patients (CDC IV) only responded to high concentrations of a few peptides. Cell separation studies of PBMC from healthy volunteers showed that the responding cells were CD4+ and expressed the CD45RO differentiation antigen. Furthermore, cord-blood mononuclear cells with less than 5% of CD45RO T cells did not proliferative to any of the peptides. Finally, CD4+ T cell lines specific for both peptides and p24 protein were successfully established from the PBMC of seronegative individuals confirming the data obtained with freshly isolated cells. These studies therefore suggest that the CD4+ cell response to p24 is not strictly disease related, instead, the response may be due to priming of the host with cross-reactive antigens.

Altered production of tumour necrosis factors alpha and beta and interferon gamma by HIV-infected individuals.

In vitro studies shows that recombinant tumour necrosis factor (TNF) alpha and beta, and interferon-gamma (IFN-gamma) can enhance HIV replication, and peripheral blood mononuclear cells (PBMC) infected with HIV in vitro secrete high levels of the same cytokines. As T cells secrete all three mediators, the capacity of T cell activation signals to trigger cytokine production in PBMC from HIV-infected individuals was investigated as such patients may be immunocompromised. We demonstrate that asymptomatic seropositives in CDC group II/III as well as patients who have progressed to CDC group IV of the disease proliferate efficiently to anti-CD3 antibody, recombinant interleukin-2 (rIL-2), phytohaemagglutinin (PHA), PHA plus phorbol 12,13 dibutyrate (PMA) but secrete significantly (P less than 0.05) higher amounts of TNF-alpha, TNF-beta and IFN-gamma compared with controls in response to the same stimulants. We also show a difference between group II/III and group IV patients with the latter secreting more TNF-alpha and IFN-gamma. The kinetics of TNF-alpha and -beta, and IFN-gamma production was stimulus dependent with overall levels varying in time for each stimulus. Furthermore, the kinetics of the response to all three stimulants were altered in seropositives; CDC group II/III and group IV patients secreted higher levels of cytokines over several time points compared to controls. The altered production of these mediators by HIV-infected patients may contribute to disease progression and to the pathogenesis of AIDS.

The activation of Langerhans cells in oral lichen planus.

The numbers of CD1, HLADR, HLADP and HLADQ positive, intraepithelial, dendritic cells were compared in lesions of oral lichen planus and normal oral mucosa using an immunoalkaline phosphatase technique. In normal mucosa, there were equal numbers of CD1 and HLADR positive cells but significantly fewer cells were positive for HLADP (P less than 0.001) and HLADQ (P less than 0.05). In lichen planus, the cells appeared more dendritic and equal numbers of CD1, HLADR, HLADP and HLADQ positive cells were found, with significantly more HLADP (P less than 0.01) and HLADQ (P less than 0.05) positive cells than in normal mucosa. There was no change in the number of CD1 and HLADR positive cells. These results show that although there is no change in the total number of Langerhans cells (CD1 positive cells) in lichen planus, there is an increase in Class II major histocompatibility antigen expression. This suggests that in lichen planus, Langerhans cells are immunologically active and play a role in lesion development.