Elevated serum thymosin alpha 1 levels associated with evidence of immune dysregulation in male homosexuals with a history of infectious diseases or Kaposi's sarcoma

Immunology in the clinic review series: focus on type 1 diabetes and viruses: the role of viruses in type 1 diabetes: a difficult dilemma

Convincing evidence now indicates that viruses are associated with type 1 diabetes (T1D) development and progression. Human enteroviruses (HEV) have emerged as prime suspects, based on detection frequencies around clinical onset in patients and their ability to rapidly hyperglycaemia trigger in the non-obese diabetic (NOD) mouse. Whether or not HEV can truly cause islet autoimmunity or, rather, act by accelerating ongoing insulitis remains a matter of debate. In view of the disease's globally rising incidence it is hypothesized that improved hygiene standards may reduce the immune system's ability to appropriately respond to viral infections. Arguments in favour of and against viral infections as major aetiological factors in T1D will be discussed in conjunction with potential pathological scenarios. More profound insights into the intricate relationship between viruses and their autoimmunity-prone host may lead ultimately to opportunities for early intervention through immune modulation or vaccination.

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

The Tat protein of human immunodeficiency virus type 1, a growth factor for AIDS Kaposi sarcoma and cytokine-activated vascular cells, induces adhesion of the same cell types by using integrin receptors recognizing the RGD amino acid sequence

Spindle-shaped cells of vascular origin are the probable tumor cells of Kaposi sarcoma (KS). These cells, derived from patients with KS and AIDS, proliferate in response to extracellular Tat protein of human immunodeficiency virus type 1. Normal vascular cells, believed to be the progenitors of AIDS-KS cells, acquire spindle morphology and become responsive to the mitogenic effect of Tat after culture with inflammatory cytokines. Such cytokines are increased in human immunodeficiency virus type 1-infected people, suggesting that immune stimulation (rather than immune deficiency) is a component of AIDS-KS pathogenesis. Here we show that (i) Tat promotes adhesion of AIDS-KS and normal vascular cells; (ii) adhesion of normal vascular cells to Tat is induced by exposure of the cells to the same cytokines; (iii) adhesion is associated with the amino acid sequence RGD of Tat through a specific interaction with the integrin receptors alpha 5 beta 1 and alpha v beta 3, although it is augmented by the basic region; and (iv) the expression of both integrins is increased by the same cytokines that promote these cells to acquire spindle morphology and become responsive to the adhesion and growth effects of Tat. The results also suggest that RGD-recognizing integrins mediate the vascular cell-growth-promoting effect of Tat.

In vitro studies of HIV-1 infection in thymic lymphocytes: a putative role of the thymus in AIDS pathogenesis

To ascertain whether thymic lymphocytes represent suitable targets for HIV-1 infection, we infected thymic cell suspensions from normal donors with HIV-1 (HTLV-IIIB strain). We found that, in vitro, thymic lymphocytes are readily infected and highly permissive for HIV-1 replication. In addition, immature cells with the CD4+/CD8+ phenotype, most likely the precursors of mature circulating CD4+ and CD8+ lymphocytes, showed a marked susceptibility to viral infection and replication. These findings suggest that thymus infection may play a triggering role in the pathogenesis of AIDS, particularly in pediatric cases, and may partially explain the lack of restoration of peripheral CD4+ lymphocytes killed by HIV-1.

Endemic pemphigus foliaceus (fogo selvagem). I. Clinical features and immunopathology

Endemic pemphigus foliaceus is an autoimmune disease that has remarkable features. Endemic foci are found in characteristic environments within the interior of Brazil. The epidemiologic data strongly suggest that an environmental factor initiates the autoantibody response in the host. As such it is an important disease for in-depth study. A group of interested investigators in both Brazil and the United States has been formed to attempt to do just that. As part of the overall effort, this Cooperative Research Group for the Study of Fogo Selvagem presents a definition of the disease, a proposed clinical classification for various forms of the disease, and an outline of what is currently known of its immunopathologic characteristics.

Preliminary results on clinical and immunological effects of thymus hormone preparations in AIDS

The human immunodeficiency virus (HIV) is the newly recognized agent of the acquired immunodeficiency syndrome (AIDS). Global defects of the immune functions, including T- and B-cell immunity, macrophage functions and cytokine production, are commonly observed among patients with HIV infection. Many studies have shown thymus involvement and endocrine function impairments among these patients. Clinical trials with thymic compounds aiming at restoring the immune dysfunctions will be reviewed.

Theoretical implications of cellular immune reactions against helper lymphocytes infected by an immune system retrovirus

The breakdown of the immune system induced by the human immunodeficiency virus might be due to the active immune destruction of human immunodeficiency virus-infected helper T lymphocytes expressing viral antigens. By numerical simulation, we have studied possible consequences that a hypothetical immunodeficiency virus (IDV) may have on the cellular immune response by using a mathematical model. In this model, IDV infects CD4+ (helper) T cells and is actively synthesized by the immunologically activated helper T cells. Infected helper T cells synthesizing IDV express antigenic determinants specific for IDV and trigger a cellular immune response against themselves that is mediated by cytotoxic T cells and cytotoxic macrophages. The dynamic evolution of the model in the case of mixed-type infections with IDV and with another pathogen that evokes a cell-mediated immune response shows strong interactions between both simultaneous infections. The model might be of value to elucidate the dynamics leading to opportunistic infections. Furthermore, a pivotal role for immunological stimulation in the progressive exacerbation of the disease can be demonstrated.

Prothymosin alpha in human blood

The major cross-reacting peptide in human plasma detected with a radioimmunoassay (RIA) for thymosin alpha 1 was identified as prothymosin alpha, based on its elution properties in gel-filtration chromatography and its amino acid composition after purification by HPLC. A small quantity (less than 10%) of the total cross-reacting material was recovered in fractions corresponding to lower molecular weight thymosin alpha 1-like peptides. The total quantity of cross-reacting material detected in human blood, expressed as thymosin alpha 1 equivalents, was 11-14 pmol/ml (approximately 90% was recovered in the leukocyte fraction, approximately 10% was in the plasma fraction, and 1-2% was in the erythrocyte fraction). The peptide present in leukocytes was also identified as prothymosin alpha. After correction for the 5-times lower molar reactivity of prothymosin alpha in the thymosin alpha 1 RIA employed in these experiments, we estimate that the content of prothymosin alpha in human blood is 55-70 pmol/ml (0.6-0.8 microgram/ml). The relatively small quantities recovered in the erythrocyte and plasma fractions may be attributed to contamination of the former by leukocytes or to leakage from leukocytes into the plasma.

Human immunodeficiency virus contains an epitope immunoreactive with thymosin alpha 1 and the 30-amino acid synthetic p17 group-specific antigen peptide HGP-30

We have reported that an antiserum prepared against thymosin alpha 1 [which shares a region of homology with the p17 protein of the acquired immunodeficiency syndrome (AIDS)-associated human immunodeficiency virus] effectively neutralized the AIDS virus and prevented its replication in H9 cells. Using HPLC and immunoblot analysis, we have identified from a clone B, type III human T-lymphotropic virus (HTLV-IIIB) extract a protein with a molecular weight of 17,000 that is immunoreactive with thymosin alpha 1. In contrast, no immunoreactivity was found in retroviral extracts from a number of nonhuman species including feline, bovine, simian, gibbon, and murine retroviruses. Heterologous antiserum prepared against a 30-amino acid synthetic peptide analogue (HGP-30) does not cross-react with thymosin alpha 1 but does react specifically with the p17 protein of the AIDS virus in a manner identical to that seen with an HTLV-IIIB p17-specific monoclonal antibody. The demonstration that this synthetic analogue is immunogenic and that antibodies to HGP-30 cross-react not only with the synthetic peptide but also with the HTLV-IIIB p17 viral protein provides an additional, and potentially more specific, candidate for development of a synthetic peptide vaccine for AIDS. In addition, the p17 synthetic peptide (HGP-30) may prove to be useful in a diagnostic assay for the detection of AIDS virus infection in seronegative individuals.

Kaposi's sarcoma and AIDS

Mucocutaneous lesions are often a prominent manifestation of the acquired immune deficiency syndrome (AIDS). Patients with this syndrome are susceptible to a number of opportunistic skin infections as well as an aggressive form of Kaposi's sarcoma. The diagnosis, the clinical setting, and the treatment of these diseases are discussed.

Low circulating thymulin-like activity in children with AIDS and AIDS-related complex

Thymic secretory function was assessed by determining levels of circulating thymulin-like activity in plasma of 21 pediatric patients infected with the HTLV-III/LAV retrovirus. All the patients had serum antibodies against p41 antigens of HTLV-III on Western blot analyses. In accordance with the latest definition established by the Centers for Disease Control, 14 patients had the acquired immunodeficiency syndrome (AIDS) and the remaining 7 were classified as having AIDS-related complex. Their ages ranged from 1 to 7 years, with 10 being less than 1 year of age. Circulating thymulin activity, normally highest in healthy children under 15 years of age, was undetectable in 11 patients and below normal range for age in the remaining. OKT4/OKT8 ratios of T-cell subsets in peripheral blood were below normal in the majority of patients. Our findings suggest that thymic epithelial injury may be an early event in HTLV-III/LAV-related disease and may precede the development of clinical and/or immunologic aberrations.

Risk factor analysis among men referred for possible acquired immune deficiency syndrome

Responses to a lifestyle questionnaire among 13 patients with Kaposi's sarcoma and 18 with an opportunistic infection were compared with those of 29 symptom-free referred individuals. Odds ratios (OR) with 95% confidence limits were calculated as an estimate of risk. Significantly elevated odds ratios (P less than 0.05) were found for cigarette smoking (OR = 3.4), marijuana use (OR = 3.7), nitrite use (OR = 5.5), frequenting bathhouses (OR = 7.6), prior syphilis (OR = 3.4), and fist-rectal sexual practices (OR = 3.5). A response gradient for the risk estimates was found for marijuana use (OR = 2.7 for occasional, OR = 4.3 for frequent use); nitrites (OR = 4.0 for occasional; OR = 6.3 for frequent use); and prior syphilis (OR = 2.9 for one to two previous infections and 9.0 for three or more). We believe the evidence is now sufficient to recommend preventive practices which may reduce the male homosexual's risk for developing acquired immune deficiency syndrome, Kaposi's sarcoma, and/or opportunistic infections. These include cessation of cigarette smoking, marijuana use, and nitrite inhalation; reduction in number of anonymous sexual partners to decrease risk of sexually transmitted diseases; and avoidance of fisting.

In vitro modulation of purine enzyme metabolism and lymphocyte surface marker expression by thymosin fraction 5 in homosexual males

Thymosin fraction 5 (Thymosin) has numerous immunoregulatory activities including modulation of enzymes involved in lymphocyte maturation. The effect of Thymosin on the purine metabolic enzymes adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and 5' nucleotidase (5'NT) in null and T-enriched peripheral blood lymphocytes from sexually active asymptomatic homosexual males (AS), patients with the AIDS-related symptom complex (ARC), and those with acquired immune deficiency syndrome (AIDS) was examined and compared to its effect on lymphocytes from healthy heterosexual controls. Mean ADA activity was significantly higher in null cells from fourteen AIDS patients than in five asymptomatic homosexuals, ten ARC patients, or 27 controls. Mean PNP activity was significantly elevated in null-enriched lymphocytes from ten ARC and fourteen AIDS patients compared to controls. No differences in these enzymes were found in T-enriched cells from any group. 5'NT was markedly decreased in both null and T lymphocytes in all homosexual groups relative to controls. Homosexuals had significantly elevated percentages of OKT10 positive and Ia positive lymphocytes compared to controls. Thymosin at an optimal concentration of 150 micrograms/ml caused significant decreases in mean ADA and PNP activity in null lymphocytes from ARC + AIDS patients along with a significant decrease in the percentage of OKT10 positive lymphocytes. No phenotypic changes were seen in AS or control lymphocytes. The data suggest that Thymosin has a maturational effect in vitro on immature T cells from symptomatic homosexuals.

Thymic peptide hormones: basic properties and clinical applications in cancer

The manuscript will provide an in-depth and critical review of the nomenclature, biochemistry, biological properties, and a summary of published and on-going clinical trials with all reported thymic preparations, including both partially purified thymic factors (e.g., thymosin fraction 5, thymostimulin) as well as purified and synthesized thymic peptides (e.g., thymosin alpha 1, thymulin). Particular emphasis will be placed on which thymic peptides should be categorized as true hormones. In addition, the comparative biochemistry and biological activity in animals will be summarized and contrasted for all the currently available thymic factors. The effects, in vitro of thymic factors, on peripheral blood lymphocytes isolated from normal donors and patients with primary immunodeficiency disorders, autoimmune disorders, and neoplastic disorders will also be reviewed. Finally, a detailed critical summary of the clinical trials performed with each of the thymic preparations will be presented with an emphasis on treatment of patients with cancer.

Precocious thymic involution manifest by epithelial injury in the acquired immune deficiency syndrome

Thymuses from six heterosexual Haitian patients with the acquired immune deficiency syndrome (AIDS) were studied by light microscopy and the findings were compared with those from three control groups. The control groups included 1) five age-matched Haitian hospital patients; 2) ten age- and sex-matched Montreal patients who had died suddenly or had had brief illnesses; and 3) 20 middle-elderly Montreal patients who had experienced chronic, wasting illnesses or prolonged hospitalization. Thymuses from patients with AIDS demonstrated pronounced involution, effacement of the cortex and medulla, marked thymocyte depletion, variable degrees of plasma cell infiltration and fibrosis, and, above all, absence of Hassall's corpuscles. Thymuses from Haitian and Montreal control subjects who had died suddenly or had brief illnesses demonstrated minimal involution and abundant Hassall's corpuscles. Although thymuses from 12 of the chronically ill control subjects demonstrated marked involution, architectural effacement, and absence of Hassall's corpuscles, partial architectural preservation and variable numbers of Hassall's corpuscles were observed in eight of these subjects. Thus, the extent of thymic involution observed in patients with AIDS antedates that incurred with aging and supersedes that induced by sustained stress and inanition. The loss of Hassall's corpuscles in patients with AIDS suggests that the thymic epithelium either incurs a form of injury or undergoes precocious involution during the illness. Whether this lesion is central to the pathogenesis of AIDS or merely a reflection of intense, sustained stress coupled with accelerated physiologic involution is unknown. It is possible that the disappearance of Hassall's corpuscles may indicate important, although as yet cryptic events within the thymic microenvironment in this syndrome.

Distribution of prothymosin alpha in rat tissues

A radioimmunoassay, using a rabbit antiserum directed against thymosin alpha 1, was employed to detect the presence of crossreacting peptides in rat tissues. Highest concentrations were present in thymus, but thymosin alpha 1 cross-reacting material was also detected in brain, liver, kidney, lung, and spleen, in amounts ranging from 15% to 65% of the quantities found in thymus. In each case, the major immunoreactive peptide, after extraction and purification by a procedure that avoids proteolytic modification, was identified as prothymosin alpha, a peptide containing approximately equal to 112 amino acid residues. Prothymosin alpha is believed to be the endogenous peptide from which thymosin alpha 1 and other fragments are formed by proteolytic modification during the preparation of thymosin fraction 5. No peptides corresponding in size and chromatographic behavior to thymosin alpha 1 were detected with the extraction procedure employed.

Immunoreactive thymosin alpha 1 is associated with murine T-cell lymphomas

Growth of murine spontaneous and transplanted AKR T-cell lymphomas results in marked elevations of serum immunoreactive thymosin alpha 1. Thymosin alpha 1 is one of the peptide hormones believed to be secreted primarily by the thymic epithelium. This elevation, however, is not mediated by the thymus but rather, seems to be directly associated with the tumor cells. Growth of a B-cell lymphoma does not generate elevated immunoreactive thymosin alpha 1 in the serum, thus, a thymosin alpha 1-like peptide is selectively associated with these T-cell lymphomas. The possible relationship between expression of T-leukemia viruses and alpha 1 expression is discussed.