Comparative loss and maturation of peripheral blood dendritic cell subpopulations in African and non-African HIV-1-infected patients.

OBJECTIVES: To quantify the percentage of the two major subpopulations of blood dendritic cells (DC) in HIV-1-seropositive Ugandan individuals infected with non-clade B viruses and compare this with that seen in clade B HIV-1 infected non-African individuals. DC maturation/activation status was also investigated via the expression of CD86. METHODS: The percentage of blood DC was quantified by using flow cytometry. DC were identified as the lineage (CD3, CD14, CD16, CD19, CD20, CD56)-negative, HLA-DR-positive population and the two major subpopulations were differentiated by CD11c expression. RESULTS: The percentage of blood DC was reduced significantly in HIV-1-seropositive African individuals when compared with controls (0.21 and 0.39% respectively). A similar reduction was also seen in non-African patients residing in the UK (0.19% compared with 0.36% for controls). However, there was no selective loss in either CD11c-positive or CD11c-negative subpopulations. The percentage of blood DC expressing CD86 was significantly greater in HIV-1-seropositive individuals when compared with controls and the increased expression was largely confined to CD11c-negative DC. CONCLUSIONS: Africans infected with non-clade B HIV-1 showed similar reductions in the percentage of blood DC to non-Africans infected with clade B viruses. There was no selective loss of either DC subpopulation, suggesting that the ability of DC to acquire and present antigens or to produce interferon-alpha may both be impaired in HIV-1 infection.

Evaluation of sperm washing as a potential method of reducing HIV transmission in HIV-discordant couples wishing to have children.

OBJECTIVE: A number of discordant couples, in whom the man is HIV positive and the woman is HIV negative, wish to have children. To conceive they must abandon protected sex, posing a risk of HIV transmission to the woman and so to the child. In such circumstances purification of spermatozoa ('sperm-washing') to inseminate the woman artificially has been proposed as a method of reducing the risk of transmission. Here we evaluate whether this does represent a true risk reduction. METHODS: Semen samples from HIV-positive patients were separated into spermatozoa, non-sperm cells (NSCs) and plasma fractions. The amount of viral RNA present in each fraction was measured and compared with the level in the peripheral blood. Each fraction was also assessed for the presence of proviral DNA. The ability of spermatozoa to be infected was assessed by evaluating for the presence of HIV receptors, i.e. CD4, CCR5 and CXCR4 on the surface of the sperm, by flow cytometry. RESULTS: A poor correlation was found between the levels of HIV in blood and semen. Within the semen the virus was restricted to the plasma and/or NSCs. All spermatozoa were negative for viral RNA or proviral DNA. Spermatozoa did not express significant levels of CD4, CCR5 or CXCR4, suggesting that they are unlikely to be major targets for HIV infection. CONCLUSIONS: These data suggest that spermatozoa are not major targets of HIV infection. Purifying spermatozoa reduced the level of HIV RNA and proviral DNA to below the detection limit of the assays irrespective of the amount of virus present in the unfractionated semen. On the basis of these data we would recommend 'sperm-washing' followed by insemination as a safer alternative to natural conception for HIV-discordant couples wishing to have children.

Effect of phototherapy and urocanic acid isomers on natural killer cell function.

Ultraviolet (UV) radiation suppresses a variety of immune responses but it is uncertain whether this action contributes to the effectiveness of phototherapy. Urocanic acid (UCA) has been proposed as a mediator of the immunologic effects of UV. On exposure the naturally occurring trans-isomer of UCA in the skin changes into the cis-isomer, which has been demonstrated to mimic many of the immunomodulatory effects of UV irradiation. Natural killer (NK) cells play an important role in several immunologic processes and published evidence indicates that their activity is altered by UV irradiation. To ascertain the effect on NK cells of phototherapy used in the treatment of psoriasis, modulation of NK activity in psoriatic patients undergoing broad-band UVB, narrow-band UVB, or psoralen plus (PUVA) regimens was examined. This was compared with NK cell activity in psoriatic patients treated with topical coal tar and in normal subjects receiving broad band UVB. The NK cell activity of psoriatic and normal subjects was the same over a wide range of effector to target cell ratios. Almost all patients undergoing phototherapy exhibited depressed NK cell activity during or after irradiation, although the timing of the depression varied between the lamps used and may be related to dose. However, patients treated with topical coal tar showed unchanged NK cell activity throughout the therapy. The effect of UCA isomers on NK cell activity in vitro was also determined. It was found that cis-UCA induced a dose-dependent suppression of NK cell activity in both patients and normal subjects, whereas trans-UCA had hardly any effect in either group. Thus it is possible that there may be a correlation between cis-UCA formation in the epidermis and the modulation of NK cell activity that occurs during phototherapy.

The effect of ultraviolet B irradiation, cis-urocanic acid and tumour necrosis factor-alpha on delayed hypersensitivity to herpes simplex virus.

Previously it has been shown that ultraviolet-B (UVB) irradiation or cis-urocanic acid (cis-UCA) treatment of mice before infection with herpes simplex virus (HSV) suppressed the delayed hypersensitivity (DH) response when the mice were subsequently challenged with inactivated virus. In the present study, the time course of the elicitation phase of the DH was examined, and it was found to be biphasic with one peak 1 h following challenge and a second at 24 h. Both UVB irradiation and cis-UCA treatment of mice before infection with HSV significantly suppressed the DH at 1 h as well as at 24 h. The role of tumour necrosis factor-alpha (TNF-alpha) in the suppression was tested by injecting mice intraperitoneally with neutralizing TNF-alpha antibodies 2 h before UVB irradiation or cis-UCA treatment followed by infection with HSV. This had no effect on the suppression of DH to HSV induced by cis-UCA but significantly reduced that generated by UVB exposure. Thus, the mechanism of suppression of DH induced by UVB irradiation or cis-UCA may be different.

The effect of histamine receptor antagonists on immunosuppression induced by the cis-isomer of urocanic acid.

Urocanic acid (UCA) is found in the stratum corneum predominantly as the trans-isomer; on ultraviolet B (UVB) irradiation, isomerization to the cis-isomer occurs. Cis-UCA has been shown to mimic the consequences of UVB irradiation in generating transient suppression of contact and delayed hypersensitivity (DH) responses. In an attempt to elucidate the mechanisms of action of UCA, the effects of 2 histamine receptor antagonists, cimetidine and terfenadine, were examined. One day after skin painting murine ears with cis-UCA, the number of ATPase- cells was reduced from 1068 to 408 mm-2. However, if cimetidine or terfenadine was applied at the same time as cis-UCA, the number of ATPase- cells was reduced only slightly from the control value, to 1028 and 892 respectively. Cis-UCA given subcutaneously or epidermally 5 h before infection of mice with herpes simplex virus suppressed the DH response on subsequent challenge with the virus. If cimetidine or terfenadine was added at the same time as cis-UCA, little suppression of the DH response to the virus occurred. Thus 2 effects of cis-UCA, on the number of ATPase+ epidermal cells and on DH response, were reduced or abrogated by histamine receptor antagonists, which may indicate that cis-UCA acts through histamine-like receptors in the skin.

The effect of UV therapy on immune function in patients with psoriasis.

Ultraviolet radiation (UVR) is known to suppress some cell-mediated immune responses to antigens encountered during or soon after exposure. Phototherapy is widely used in psoriasis, and this study was undertaken to monitor changes in a range of immunological parameters during standard courses of treatment, with the aim of ascertaining whether such modulations contribute to the effectiveness of therapy. The responses of 17 patients with psoriasis undergoing UVB therapy, and four receiving PUVA therapy, were compared with 15 patients receiving coal tar treatment and four normal subjects undergoing UVB irradiation. In each case, samples were taken before starting therapy, after 4 weeks of therapy, and 4 weeks after completion of treatment. Serum immunoglobulin isotypes and complement components were within normal ranges in most of the psoriasis patients, and remained unchanged throughout therapy. Similarly, percentages of subsets of peripheral blood mononuclear cells (PBMC) were normal, and were unaltered by treatment. Patients who were already infected with herpes simplex virus (HSV), as demonstrated by a positive lymphoproliferation test in vitro, were monitored for asymptomatic HSV shedding and HSV recrudescences during therapy. There was little evidence that phototherapy caused reactivation of the virus. No significant alteration in lymphoproliferative response to HSV and to the mitogen concanavalin A was observed during therapy. Epidermal cells and blood adherent cells were used to present HSV to PBMC, depleted of adherent cells and enriched for T cells, in a lymphoproliferative assay. The functional antigen-presenting ability of adherent cells remained unchanged throughout therapy, whereas that of epidermal cells was suppressed during UVB irradiation and recovered, in most instances, after UVB therapy had been completed. The epidermis of patients with psoriasis contained about three times the quantity of urocanic acid (UCA) of normal subjects, whereas the UCA concentration in suction blister fluid did not differ between the two groups. During UVB irradiation, the percentage of cis-UCA rose in both the epidermis and suction blister fluid of all subjects, and it remained elevated in the blister fluid after therapy had finished. Tumour necrosis factor-alpha was measured in suction blister fluid, and its concentration did not alter consistently as a result of therapy. Whether any of the immunological parameters measured, and the changes noted, contribute to the effectiveness of phototherapy in the treatment of psoriasis remains uncertain.

The role of histamine-like receptors in immunosuppression of delayed hypersensitivity induced by cis-urocanic acid.

The cis-isomer of urocanic acid (UCA) has been shown previously to mimic the effect of ultraviolet B (UVB) irradiation in suppressing delayed hypersensitivity (DH) responses to virus in a murine model of herpes simplex virus (HSV) infection. Cimetidine, an H2 receptor antagonist, and terfenadine, an H1 receptor antagonist, abrogated the suppression of DH to HSV induced by cis-UCA, leading to the suggestion that histamine-like receptors may be involved in the mechanism of action of cis-UCA on immune responses. In the present study, cis and trans-isomers of 4 UCA analogues (1- and 2-imidazoyl-acrylic acid), and (2- and 3-pyridyl-acrylic acid) were tested for their ability to suppress DH to HSV in infected mice, and only cis-2-pyridyl-acrylic acid was effective. Second, an H2 and H3 agonist were similarly tested: the former was suppressive and the latter had no effect. Third, an H3 receptor antagonist, thioperamide, did not seem to abrogate the suppression of DH induced by cis-UCA. These results substantiate a role for H1 and H2-like receptors, but probably not H3 receptors, in cis-UCA induced immunosuppression.

Increased serum transforming growth factor-beta1 in human colorectal cancer correlates with reduced circulating dendritic cells and increased colonic Langerhans cell infiltration.

Cancer-related cytokines may interfere with the differentiation and migration of dendritic cells (DCs) and with the associated up-regulation of co-stimulatory molecules in vitro. We determined whether cytokines affected the distribution and activation of DCs in patients with colorectal cancer by measuring the levels of serum cytokines [transforming growth factor (TGF)-beta1 and vascular endothelial growth factor (VEGF)], DC numbers and phenotype from peripheral blood and mesenteric lymph nodes draining the cancer, and the infiltration of DCs into colorectal cancer. A significant increase in the serum level of TGF-beta1 correlated with a significant reduction in the level of circulating DCs in cancer patients that was associated with an increased infiltration of Langerhans cells into colorectal mucosa. The prevalence but not intensity of co-stimulatory molecule expression in circulating and mesenteric lymph node DCs was reduced in patients with colorectal cancer compared to patients with inflammatory bowel conditions. There was no correlation between co-stimulatory molecule expression and serum TGF-beta1. Thus the circulating DC depletion in colorectal cancer could be explained by a TGF-beta1-related DC redistribution from the circulation into the colorectal cancer and adjacent mucosa where DC levels were increased. There was an impairment of DC activation within colorectal cancer that was not related to serum level of cytokines.