Thymosin alpha 1 and thymosin beta 4 in serum: comparison of normal, cord, homosexual and AIDS serum

Cell Senescence and Central Regulators of Immune Response

Pathways regulating cell senescence and cell cycle underlie many processes associated with ageing and age-related pathologies, and they also mediate cellular responses to exposure to stressors. Meanwhile, there are central mechanisms of the regulation of stress responses that induce/enhance or weaken the response of the whole organism, such as hormones of the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic and parasympathetic systems, thymic hormones, and the pineal hormone melatonin. Although there are many analyses considering relationships between the HPA axis and organism ageing, we found no systematic analyses of relationships between the neuroendocrine regulators of stress and inflammation and intracellular mechanisms controlling cell cycle, senescence, and apoptosis. Here, we provide a review of the effects of neuroendocrine regulators on these mechanisms. Our analysis allowed us to postulate a multilevel system of central regulators involving neurotransmitters, glucocorticoids, melatonin, and the thymic hormones. This system finely regulates the cell cycle and metabolic/catabolic processes depending on the level of systemic stress, stage of stress response, and energy capabilities of the body, shifting the balance between cell cycle progression, cell cycle stopping, senescence, and apoptosis. These processes and levels of regulation should be considered when studying the mechanisms of ageing and the proliferation on the level of the whole organism.

Precursors of thymic peptides as stress sensors

INTRODUCTION

A large volume of data indicates that the known thymic hormones, thymulin, thymopoietin, thymosin-α, thymosin-β, and thymic humoral factor-y2, exhibit different spectra of activities. Although large in volume, available data are rather fragmented, resulting in a lack of understanding of the role played by thymic hormones in immune homeostasis.

AREA COVERED

Existing data compartmentalizes the effect of thymic peptides into 2 categories: influence on immune cells and interconnection with neuroendocrine systems. The current study draws attention to a third aspect of the thymic peptide effect that has not been clarified yet, wherein ubiquitous and highly abundant intranuclear precursors of so called 'thymic peptides' play a fundamental role in all somatic cells.

EXPERT OPINION

Our analysis indicated that, under certain stress-related conditions, these precursors are cleaved to form immunologically active peptides that rapidly leave the nucleus and intracellular spaces, to send 'distress signals' to the immune system, thereby acting as stress sensors. We propose that these peptides may form a link between somatic cells and immune as well as neuroendocrine systems. This model may provide a better understanding of the mechanisms underlying immune homeostasis, leading thereby to the development of new therapeutic regimes utilizing the characteristics of thymic peptides.

Serum thymosin alpha 1 levels in normal and pathological conditions

INTRODUCTION

Thymosin alpha 1 (Ta1) is a natural occurring peptide hormone that is crucial for the maintenance of the organism homeostasis. It has been chemically synthesized and used in diseases where the immune system is hindered or malfunctioning.

AREAS COVERED

Many clinical trials investigate the Ta1 effects in patients with cancer, infectious diseases and as a vaccine enhancer. The number of diseases that could benefit from Ta1 treatment is increasing. To date, questions remain about the physiological basal levels of Ta1 and the most effective dose and schedule of treatment. Evidence is growing that diseases characterized by deregulation of immune and/or inflammatory responses are associated with serum levels of Ta1 significantly lower than those of healthy individuals: to date, B hepatitis, psoriatic arthritis, multiple sclerosis and sepsis. The sputum of cystic fibrosis patients contains lower levels of Ta1 than healthy controls. These data are consistent with the role of Ta1 as a regulator of immunity, tolerance and inflammation.

EXPERT OPINION

Low serum Ta1 levels are predictive and/or associated with different pathological conditions. In case of Ta1 treatment, it is crucial to know the patient's baseline serum Ta1 level to establish effective treatment protocols and monitor their effectiveness over time.

Thymosin-alpha1 modulates dendritic cell differentiation and functional maturation from human peripheral blood CD14+ monocytes

Although thymosins have been demonstrated to have immunomodulatory effects, it is still not clear whether they could affect dendritic cells (DCs), the most professional antigen-presenting cells. The objective of this study was to determine the effect and potential mechanisms of thymosin-alpha1 (Talpha1) on DC differentiation and functional maturation. Human peripheral blood CD14(+) monocytes were purified by using a magnetic separation column and cultured with GM-CSF and IL-4 to differentiate into immature DCs (iDCs). In the presence of Talpha1, iDC surface markers CD40, CD80, MHC class I and class II molecules were significantly upregulated as measured by flow cytemotry analysis. However, Tbeta4 or Tbeta10 did not show these effects on iDCs. There was an approximately 30% reduction in antigen (FITC-conjugated dextran)-uptake by Talpha1-treated iDCs as compared with non-Talpha1-treated iDCs. In addition, Talpha1-treated matured DCs (mDCs) showed an increased stimulation of allogeneic CD3(+) T-cell proliferation as measured by a mixed-lymphocyte reaction assay. Talpha1-treated mDCs also increased the production of several Th1- and Th2-type cytokines as measured by a Bio-Plex cytokine assay. Furthermore, rapid activation of p38 MAPK and NFkappaB was seen in Talpha1-treated iDCs as measured by a Bio-Plex phosphoprotein assay. Thus, Talpha1 significantly enhances DC differentiation, activation, and functions from human peripheral blood CD14(+) monocytes possibly through a mechanism of the activation of p38 MAPK and NFkappaB pathways. This study provides a basis to further evaluate Talpha1 as a possible adjuvant for a DC-directed vaccine or therapy.

Development of a sensitive and specific enzyme-linked immunosorbent assay for thymosin beta15, a urinary biomarker of human prostate cancer

OBJECTIVES

In tissue-based assays, thymosin beta15 (Tbeta15) has been shown to correlate with prostate cancer (CaP) malignancy and with future recurrence. To be clinically effective, it must be shown that Tbeta15 is released by the tumor into body fluids in detectable concentrations. Toward this end, we have worked to develop a quantitative high-throughput assay that can accurately measure clinically relevant concentrations of Tbeta15 in human urine.

DESIGN AND METHODS

Sixteen antibodies were raised against recombinant Tbeta15 and/or peptide conjugates. One antibody, having stable characteristics over the wide range of pH and salt concentrations found in urine and minimal cross-reactivity with other beta thymosins, was used to develop a competitive enzyme-linked immunosorbent assay (ELISA). Urinary Tbeta15 concentration was determined for control groups; normal (N = 52), prostate intraepithelial neoplasia (PIN, N = 36), and CaP patients; untreated (N = 7) with subsequent biochemical failure, radiation therapy (N = 17) at risk of biochemical recurrence.

RESULTS

The operating range of the competition ELISA fell between 2.5 and 625 ng/mL. Recoveries exceeded 75%, and the intra- and inter-assay coefficients of variability were 3.3% and 12.9%, respectively. No cross-reactivity with other urine proteins was observed. A stable Tbeta15 signal was recovered from urine specimens stored at -20 degrees C for up to 1 year. At a threshold of 40 (ng/dL)/mug protein/mg creatinine), the assay had a sensitivity of 58% and a specificity of 94%. Relative to the control groups, Tbeta15 levels were greater than this threshold in a significant fraction of the CaP patients (P < 0.001), including 5 of the 7 patients who later experienced PSA recurrence.

CONCLUSIONS

We have established an ELISA that is able to detect Tbeta15 at clinically relevant concentrations in urine from patients with CaP. The assay will provide a tool for future clinical trials to validate urinary Tbeta15 as a predictive marker for recurrent CaP.

Roles of thymosins in cancers and other organ systems

Thymosins are small peptides, originally identified from the thymus, but now known to be more widely distributed in many tissues and cells. Thymosins are divided into three main groups, alpha-, beta-, : and gamma-thymosins, based on their isoelectric points. alpha-thymosins (ProTalpha, Talphal) have nuclear localization and are involved in transcription and/or DNA replications; whereas beta-thymosins (Tbeta4, Tbeta10, Tbetal5) have cytoplasmic localization and show high affinity to G-actin for cell mobility. Furthermore, it is well known that both alpha- and beta-thymosins play important roles in modulating immune response, vascular biology, and cancer pathogenesis. More importantly, thymosins may have significant clinical applications. They may serve as molecular markers for the diagnosis and prognosis of certain diseases. In addition, they could be molecular targets of certain diseases or be used as therapeutic agents to treat certain diseases. However, the molecular mechanisms of action of thymosins are largely unknown. This review not only presents recent advances of basic science research of thymosins and their clinical applications but provides thoughtful views for future directions of investigation on thymosins.

Apoptosis-related fragmentation, translocation, and properties of human prothymosin alpha

Human prothymosin alpha is a proliferation-related nuclear protein undergoing caspase-mediated fragmentation in apoptotic cells. We show here that caspase-3 is the principal executor of prothymosin alpha fragmentation in vivo. In apoptotic HeLa cells as well as in vitro, caspase-3 cleaves prothymosin alpha at one major carboxy terminal (DDVD(99)) and several suboptimal sites. Prothymosin alpha cleavage at two amino-terminal sites (AAVD(6) and NGRD(31)) contributes significantly to the final pattern of prothymosin alpha fragmentation in vitro and could be detected to occur in apoptotic cells. The major caspase cleavage at D(99) disrupts the nuclear localization signal of prothymosin alpha, which leads to a profound alteration in subcellular localization of the truncated protein. By using a set of anti-prothymosin alpha monoclonal antibodies, we were able to observe nuclear escape and cell surface exposure of endogenous prothymosin alpha in apoptotic, but not in normal, cells. We demonstrate also that ectopic production of human prothymosin alpha and its mutants with nuclear or nuclear-cytoplasmic localization confers increased resistance of HeLa cells toward the tumor necrosis factor-induced apoptosis.

Modulatory role of thymosin-alpha-1 in normal bone-marrow haematopoiesis and its effect on myelosuppression in T-cell lymphoma bearing mice

In continuation with the earlier and ongoing studies on Thymosin-alpha-1 (Talpha1) exerting its immunomodulatory effects on various components of the immune system including T-cells, NK-cells, blood lymphocytes and macrophages, the role of Talpha1 in normal bone-marrow haematopoiesis has been investigated in the present study. The haematopoietic alterations associated with the growth of murine T-cell lymphoma, Dalton's Lymphoma (DL) and subsequently its restoration by Talpha1 was also investigated. It is observed that the non-adherent bone-marrow cells from normal mice (N-BMCs) exhibited enhanced proliferation on in vitro treatment with Talpha1 (dose range of 1-100 ng/ml) with maximal response at 100 ng/ml of Talpha1. In vitro stimulation with 100 ng/ml of Talpha1 also resulted in increased myeloid colony formation, as manifested by the rise in total number of colonies, frequency of the individual colony types and their size. This response was further upregulated in the presence of various colony stimulating factors (CSFs) like MCSF, GMCSF, GCSF and IL-3. Similarly, in vivo administration of Talpha1 (a single intraperitoneal injection of 10 microg per mouse) to normal mice also resulted in enhanced proliferation and colony formation by BMCs as compared with BMCs obtained from untreated mice. On the contrary, the progressive growth of T-cell lymphoma in mice led to suppressed myelogenesis, with marked reduction in the total colony numbers and their size. The BMCs from DL-bearing mice (DL-BMCs) displayed a preferential lineage-restricted differentiation towards the granulocytic-type colonies with maximum numbers of CFU-Gs and CFU-GMs, followed by CFU-Ms. However, incubation of DL-BMCs with 100 ng/ml of Talpha1, in vitro restored their suppressed proliferation and colony forming ability (CFA) with significantly enhanced total number of colonies and individual colony types, which further increased in the presence of CSFs. In vivo studies with BMCs from DL-bearing mice treated with single intraperitoneal injection of 10 microg Talpha1/mouse also resulted in significant enhancement in their proliferative as well as colony forming ability in comparison to that of untreated DL-mice. The present observations suggest that Talpha1 can positively modulate the haematopoietic functions of normal murine BMCs, in addition to its myelorestorative role in tumour-bearing mice showing suppressed myelopoiesis.

Effect of thymosin peptides on the chick chorioallantoic membrane angiogenesis model

The effect of alpha- and beta-thymosin peptides, namely prothymosin alpha (ProT(alpha)), thymosin alpha(1) (T(alpha)1), parathymosin alpha (ParaT(alpha)), thymosin beta(4) (Tbeta4), thymosin beta(10) (Tbeta10), and thymosin beta(9) (Tbeta9), on the angiogenesis process was investigated using the chick chorioallantoic membrane as an in vivo angiogenesis model. The thymosin peptides tested were applied in 10 microl aliquots containing 0.01-4 nmoles of Tbeta4, Tbeta10 or Tbeta9, 0.016-6.66 nmoles of T(alpha)1, 4.1 pmoles-1.66 nmoles of ProT(alpha), and 4.4 pmoles-1.76 nmoles of ParaT(alpha). Phorbol 12-myristate 13-acetate and hydrocortisone were also used as positive and negative control, respectively. Tbeta4, ProT(alpha) and T(alpha)1 were found to enhance angiogenesis, while Tbeta10, Tbeta9 and ParaT(alpha) exhibited an inhibitory effect on the angiogenesis process. When mixtures of Tbeta4 and Tbeta10 containing active amounts of the two peptides at different proportions were applied, the promoting effect of Tbeta4 on angiogenesis was reversed in the presence of increasing concentrations of Tbeta10 and vice versa. The effect of Tbeta10, Tbeta9, ProT(alpha) and ParaT(alpha), in parallel with Tbeta4 and T(alpha)1, on the angiogenesis process was investigated for the first time as far as we know and the results of this study offer more insight into the biological regulatory roles of thymosin peptides, and provide helpful information about their therapeutic potential. Whether these agents could be used either as inhibitors of angiogenesis in disease states where uncontrolled angiogenesis is involved, e.g. in carcinogenesis, or as angiogenesis promoters that could be useful in wound healing, fracture repair, peptic ulcers etc., remains to be further studied.

Mechanism of thymocyte apoptosis induced by serum of tumor-bearing host: the molecular events involved and their inhibition by thymosin alpha-1

The observations presented in this paper indicate that serum of Dalton's lymphoma (DL) bearing mice contained certain soluble factor(s) that augmented the induction of apoptosis in thymocytes in a time- and dose-dependent manner. DL-ascitic fluid and DL-conditioned medium could also induce apoptosis of thymocytes in vitro, though the magnitude of the same was consistently lower than that induced by serum of DL-bearing mice. It was observed that the interaction of FasL and TNFalpha with their respective receptors could trigger apoptosis in thymocytes. Elucidation of the signal transduction mechanism revealed involvement of protein tyrosine kinase, protein kinase C and ser/thr phosphatases with concomitant increase in the level of protein products of apoptosis associated genes p53, bax, bad, fas and fas ligand and cleavage of N-terminal 23 kDa fragment of Bcl-2 that exhibited Bax-like death effector properties. Further, we report, for the first time, the ability of thymosin alpha-1, an immunopotentiating thymic hormone, to antagonize apoptosis in thymocytes induced by factors present in serum of DL-bearing mice. The underlying mechanism of tumor serum induced apoptosis inhibition by thymosin alpha-1 was also analyzed. The signal transduction cascade evoked by thymosin alpha-1 involves activation of protein kinase C with a decrease in the level of protein products of proapoptotic genes like bax and bad and increase in the protein products of bcl-2 gene.

Thymosin α1 Stimulates Endothelial Cell Migration, Angiogenesis, and Wound Healing

In wound healing, lymphoid cells release soluble factors that attract fibroblasts and macrophages, initiating repair, endothelial cell migration, angiogenesis, and matrix production. We analyzed the effect of thymosin α1 (Tα1) on endothelial cell migration, angiogenesis, and wound healing. Tα1, a 28 amino acid peptide initially isolated from the thymus, enhanced the morphologic differentiation of endothelial cells and was a potent chemoattractant for endothelial cells and monocytes in vitro. In vivo, Tα1 stimulated angiogenesis in a subcutaneous model. When given either topically or i.p., it accelerated wound healing in a punch model, demonstrating that Tα1 promotes angiogenesis and wound healing.

Biodistribution of synthetic thymosin alpha1 in the serum, urine and major organs of mice

Thymosin fraction 5 (TF5), a thymic preparation, has been shown to be an immune-potentiating agent consisting of biologically active polypeptide components with hormone-like activities. Thymosin alpha1 (T alpha1) was the first biologically active polypeptide to be purified from TF5 and completely characterized. It is an acidic peptide with an isoelectric point of 4.2 and a molecular weight of 3108. T alpha1 is considered a biological response modifier which amplifies T-cell immunity. In the present study, we have studied some pharmacokinetic properties of T alpha1 by measuring its concentrations in serum, urine and ten major organs of female Swiss-Webster mice following administration of 500 microg T alpha1 intraperitoneally. Using a modified enzymatic immunoassay, our data show a significant increase of T alpha1 in serum 2 min after injection and lasting for 2 h (average: 1.55 +/- 0.27 microg/ml). In urine, at four different time points after injection (20 min, 40 min, 2 h, 6 h), increased concentrations of T alpha1 were found between 24.2 and 25.4 microg/ml (average: 25 +/- 0.47 microg/ml). Of the 500 microg T alpha1 administered to mice, 8.97% was recovered at the end of the study, of which 2% corresponded to urine, 1.25% to serum (2 ml of serum per mouse), and 5.72% to organs. Since the urine/day volume and the serum volume of any Swiss Webster mouse is ca 2 ml, additional extrapolation of the above mentioned values could show percentages of recovery close to 40% for urine and 2.5% for serum. In most of the organs, the wet weight concentrations of T alpha1 increased significantly during the first 40 min after injection in comparison to their baseline wet weight concentrations. These organs consisted of the following: thymus (33.1 +/- 3.5 microg/g vs 18 microg/g baseline); lungs (7.7 +/- 1.1 microg/g vs 1.9 microg/g baseline); spleen (15.6 +/- 0.7 microg/g vs 5.6 microg/g); kidneys (6.2 +/- 1.1 microg/g vs 3.9 microg/g); ovaries (9.2 +/- 1.4 microg/g vs 0 microg/g); and peritoneal fat (4 +/- 1 microg/g vs 0 microg/g). No significant increases were observed in the liver (1.7 +/- 0.1 microg/g vs 1.4 microg/g) and heart (0.7 +/- 0.5 microg/g vs 0 microg/g). Increased concentrations of T alpha1 were not detected in the brain and skeletal muscle tissues. These pharmacokinetic studies of T alpha1 in mice indicate that rapid renal excretion of T alpha1 represents a major source of humoral loss following I.P. administration. Recent preliminary studies in humans confirm that the kidney rapidly releases high levels of T alpha1 in urine in a time frame consistent with that observed in mice.

Biodistribution of synthetic thymosin beta 4 in the serum, urine, and major organs of mice

Thymosin beta 4 (T beta 4) is a peptide of 43 amino acids that was first isolated from the thymus gland and subsequently found to be ubiquitous in nature. T beta 4 functions mainly as an actin-sequestering molecule in nonmuscle cells, where its primary role is to maintain the large pool of unpolymerized G-actin in the cell. Studies on the pharmacokinetics of T beta 4 in human and other mammals have not been reported so far. In the present study, we have measured T beta 4 concentrations in serum, urine, and 10 major organs of female Swiss-Webster mice following intraperitoneal administration of 400 micrograms synthetic T beta 4. Using a modified enzymatic immunoassay, our data show a significant increase of T beta 4 in serum starting 2 min after injection and lasting for 40 min (average: 2.34 +/- 0.54 micrograms/ml). High concentrations were found in urine (59.3 +/- 7.54 micrograms/ml) at three different points after injection (20 min, 40 min, and 2 h). Of the 400 micrograms T beta 4 administered to mice 83% was recovered at the end of the study, 44.6% of which corresponded to urine, 1.4% to serum, and 37.5% to the organs. In 50% of the tested organs, the wet weight concentrations of T beta 4 increased significantly from the first 40 min to 2 h after injection in comparison to their baseline wet weight concentrations. These organs were: the brain (72 micrograms/g), heart (80 micrograms/g), liver (15 micrograms/g vs 9 micrograms/g), kidneys (65 micrograms/g vs 28 micrograms/g), and peritoneal fat (47 micrograms/g vs 13 micrograms/g). Wet weight concentrations increased in the thymus (196 micrograms/g vs 147 micrograms/g) and muscle (45 micrograms/g vs 0 micrograms/g) after 6 h of injection. The spleen showed an increase in wet weight concentrations at the 2 min timepoint (267 micrograms/g vs 161 micrograms/g). Ovaries had a biphasic increase at 40 min (72 micrograms/g vs 62 micrograms/g) and 24 h (92 micrograms/g vs 62 micrograms/g) after T beta 4 administration. In lungs, the highest wet weight increase after injection (149 micrograms/g at timepoint 6 h) was not higher than its basal wet weight concentration (153 micrograms/g). These pharmacokinetic studies of T beta 4 in mice have established that high levels of T beta 4 are found in blood following I.P. administration and the kidney rapidly removes the peptide from the circulation. The kinetics of this response should help define the proper scheduling of administration of T beta 4 during clinical trials in disorders, such as the acute respiratory distress syndrome (ARDS), associated with actin toxicity.

Matrigel induces thymosin beta 4 gene in differentiating endothelial cells

We performed differential cDNA hybridization using RNA from endothelial cells cultured for 4 hours on either plastic or basement membrane matrix (Matrigel), and identified early genes induced during the morphological differentiation into capillary-like tubes. The mRNA for one clone, thymosin beta 4, was increased 5-fold. Immunostaining localized thymosin beta 4 in vivo in both growing and mature vessels as well as in other tissues. Endothelial cells transfected with thymosin beta 4 showed an increased rate of attachment and spreading on matrix components, and an accelerated rate of tube formation on Matrigel. An antisense oligo to thymosin beta 4 inhibited tube formation on Matrigel. The results suggest that thymosin beta 4 is induced and likely involved in differentiating endothelial cells. Thymosin beta 4 may play a role in vessel formation in vivo.

Modulation of cellular gene expression of HIV type 1 infection as determined by subtractive hybridization cloning: downregulation of thymosin beta 4 in vitro and in vivo

Chronic infection with HIV-1 has profound effects on host cell growth and function. We used subtractive hybridization cloning to identify genes whose expression is modulated by HIV-1 infection in the T leukemia cell line CEM. The gene encoding thymosin beta 4, a ubiquitous polypeptide associated with hematopoietic differentiation, showed two- to threefold reduced transcription in HIV-1-infected CEM cells and other HIV-1-infected T cells and macrophages in vitro. Solid-phase radioimmunoassay revealed about a threefold decrease in the level of thymosin beta 4 protein in lysates of infected cells. Northern blot analysis of RNA samples from lymphocytes of five AIDS patients reveals an up to fivefold reduction in the level of thymosin beta 4 mRNA. These results indicate that HIV-1 infection may directly influence the expression of certain physiologically important proteins.

Altered levels of prothymosin immunoreactive peptide, a growth-related gene product, during liver regeneration after chronic ethanol feeding

Liver regeneration is regulated by the orderly activation of growth-related genes. Although ethanol impairs induction of liver regeneration by partial hepatectomy, we have not identified ethanol-associated differences in the hepatic mRNA levels of several proto-oncogenes, including c-myc, which peaks 3-6 hr post-partial hepatectomy. Prothymosin alpha, a gene encoding a ubiquitous nuclear protein, is activated by c-myc in resting fibroblasts and has been implicated as a regulator of cell proliferation. Prothymosin alpha mRNA levels reportedly increase 12-32 hr post-partial hepatectomy, several hours after c-myc induction. We sought to determine if chronic ethanol intake alters the expected induction post-partial hepatectomy of prothymosin alpha steady-state mRNA expression and protein levels. Comparing rats chronically fed ethanol with pair-fed controls, we found no significant differences in steady-state levels of prothymosin alpha mRNA; however, we did see a delay in the increase of prothymosin immunoreactive peptide in rats chronically fed alcohol. This suggests that the inhibition in protein levels in ethanol fed rats is not due to lower steady-state mRNA levels, but may occur post-transcriptionally. Further data are needed to determine if this finding is important in the inhibition in cell growth following partial hepatectomy in rats chronically fed ethanol.

Thymosin alpha-1 as adjunct for conventional therapy of malignant tumors: a review

T alpha 1, a 28-amino-acid peptide, is derived from PT alpha, which is an intracellular, nonsecretory protein of unknown function. Both T alpha 1 and PT alpha are found in the blood of normal individuals. Subcutaneous and intramuscular injections of T alpha 1 in doses up to 9.6 mg/m2 are tolerated without side effects, and 0.9 mg/m2 injections raise the serum level approximately 30-fold after 1 hr of administration, which slowly returns to baseline within 24 hr. In vitro, and perhaps in vivo, T alpha 1 restores normal T-cell function. It increases IL-2 production and IL-2 receptors in normal mitogen-stimulated T cells and stimulates IL-3 production in immunocompromised mice. The dose-response relationship for these effects is not linear and may be bimodal. T alpha 1 binds to VIP receptors and inhibits in vitro and xenograft growth of non-SCLC cell lines. In patients with nonbulky carcinomas who have received standard therapy, T alpha 1 is possibly effective in prolonging the time to relapse and in improving survival. At present there is a great need to clearly define the clinical role of T alpha 1 in cancer patients. A major problem encountered in studies with T alpha 1 will, however, be the present lack of knowledge with regard to its mechanism in effecting tumor growth. It is not at all clear whether its immunomodulatory functions, its interaction with VIP receptors, or none of these mechanisms are related to its antineoplastic activities. In addition, the apparent nonlinear dose-response relationship will make it difficult to choose a reasonable dosing schedule for clinical trials. This is particularly apparent in light of the experimental animal data summarized above where a tumor response was seen at doses of 4 micrograms/kg and 400 micrograms/kg but not at 0.4 microgram/kg and 40 micrograms/kg. This dose range could conceivably be given to humans since 9.6 mg/m2, the maximum dose given to humans without major side effects to date, is roughly equivalent to 250 micrograms/kg. At this time a reasonable clinical approach would be a well-designed risk factor stratified phase III clinical trial using 0.9 mg/m2 T alpha 1 subcutaneously twice a week compared to a control group to substantiate the data reported by Schulof et al. Before such data are available, T alpha 1 should not be used in clinical oncology.

Thymosin beta 4 synergizes with human granulocyte-macrophage colony-stimulating factor in maintaining bone marrow proliferation

Recent evidence supports a role for thymosin beta 4 (T beta 4) in the inhibition of murine hematopoietic stem cell proliferation. This supposition results from studies in which the N-terminal tetrapeptide derived from native T beta 4 was administered to mice and appeared to prevent CFU-S recruitment into DNA synthesis. The importance of this observation was the concomitant ability of the tetrapeptide to prevent cytosine arabinoside (ara-C) toxicity in mice given LD50 doses of this drug. In the present study, we have extended these observations by demonstrating that whole synthetic T beta 4 is more effective than the N-terminal tetrapeptide in protecting mice from the toxicity of ara-C. This observation supports the hypothesis that T beta 4 is the biologically important parent molecule for this activity. To determine if inhibition of cell cycle progression also occurs in committed human bone marrow progenitors treated with T beta 4, we have investigated the effects of synthetic T beta 4 on proliferating and unstimulated enriched human bone marrow. In short-term liquid cultures studied sequentially over 1-7 days, T beta 4 failed to inhibit cell proliferation, but maintained the proliferative effect of granulocyte-macrophage colony stimulating factor (GM-CSF) on days following maximum stimulation (days 5-7). No effect was noted before the fifth day in culture, nor did T beta 4 exert any demonstrable effect in the absence of added GM-CSF. Any observable effect of T beta 4 required that it be present in the cultures on or before day 3 of GM-CSF stimulation. These results suggest that an additional effect of T beta 4 is the stimulation of a subpopulation of committed human bone marrow precursor cells to become more sensitive to the growth-promoting activity of GM-CSF, thereby enhancing myelopoiesis. It is of interest that the N-terminal peptide of T beta 4 is a shared sequence with tumor necrosis factor alpha, which is also known to have a similar stimulatory capacity. We, therefore, postulate that the growth enhancement noted in short-term cultures is mediated by the region containing these shared sequences.

Serum cross-reactive thymosin alpha 1 levels in rats during induction of mammary carcinoma with 7,12-dimethylbenz[a]anthracene: short- and long-term effects

The levels of serum cross-reactive thymosin alpha 1 (CRT alpha 1) were measured at various time intervals during the course of development of mammary tumors in female Sprague-Dawley rats intubated with 7,12-dimethylbenz[a]-anthracene (DMBA; 10 mg/rat). Matched control rats were also tested simultaneously. An increase in CRT alpha 1 in DMBA-treated animals was observed within 2 h of DMBA treatment. Thereafter the levels of CRT alpha 1 in the serum of the DMBA-treated rats remained elevated for another 3 weeks prior to declining to control levels. Levels remained stationary until an increase in serum CRT alpha 1 was observed at 9-11 weeks post-DMBA treatment. This correlated with the time when mammary tumors were either palpable or observed. Levels of CRT alpha 1 fell at 13 weeks but remained slightly elevated until sacrifice due to tumor burden at 18 weeks.

Identification of immunoreactive forms of thymosin alpha 1 in serum and supernatants by combining HPLC and RIA

Thymosin alpha 1 (T alpha 1) is a biologically active peptide, originally isolated from the thymus and currently undergoing clinical trials as an immunomodulator in cancer patients, in individuals with chronic active hepatitis, and as an immunoenhancer of vaccines in immunocompromised individuals. Absorption of rabbit antibody to thymosin alpha 1 with a synthetic C-14 fragment of T alpha 1 results in an antiserum with increased affinity for the amino terminal region of T alpha 1 and the precursor protein prothymosin alpha (ProT alpha). Using HPLC methodologies, the predominant form of immunoreactivity in serum and thymus was T alpha 1 not the precursor. Using this assay we detected a decline in mouse serum T alpha 1 following irradiation but not thymectomy, an observation consistent with the existence of an important radiation sensitive lymphoid source of serum T alpha 1. The secretion of authentic T alpha 1 but not the precursor into culture medium by thymic epithelial cells as well as in mitogen-stimulated peripheral blood lymphocytes was also demonstrated by HPLC/RIA. HPLC analysis by molecular weight sizing columns demonstrated that unlike thymic epithelial cells or peripheral blood lymphocytes, the immunoreactive T alpha 1 (IRT alpha 1) form in the supernatants from tumor cells such as MCF-7 breast carcinoma was of a lower molecular weight than authentic T alpha 1. These studies suggest that the authentic form of T alpha 1 is the major immunoreactive form in normal serum and that it is secreted by the medullary thymic epithelial cells as well as by peripheral blood lymphocytes. An additional immunoreactive form, secreted by tumor cells has also been identified and is the subject of future studies.

AIDS virus infection and autoimmunity: a perspective of the clinical, immunological, and molecular origins of the autoallergic pathologies associated with HIV disease

The acquired immune deficiency syndrome (AIDS) is a viral-induced disorder of humans that is reaching pandemic proportions. The etiologic agent responsible for AIDS is recognized as a retrovirus termed the human immunodeficiency virus (HIV). This virus is both cytotropic and cytopathic for T lymphocytes in vitro, and patients with AIDS and HIV-related conditions invariably have serious T cell abnormalities, notably a reduced number of the helper/inducer (CD4+) subpopulation. There is now a substantial body of evidence to suggest that the AIDS virus triggers a diverse range of autoimmune phenomena. The purpose of this article is to summarize the clinical and immunopathological manifestations of autoimmunity in HIV infection and to provide a perspective of the possible origins and roles autoimmune reactions play in HIV disease progression.

Beta 2-microglobulin and neopterin: predictive markers for human immunodeficiency virus type 1 infection in children?

The value of beta 2-microglobulin and neopterin concentrations in serum for early diagnosis of infants born to human immunodeficiency virus type 1 (HIV-1)-infected mothers was assessed. Concentrations of both markers were measured in serum samples from pediatric patients (Centers for Disease Control classifications P0, P1, and P2), as well as in age-matched normal subjects. Both beta 2-microglobulin and neopterin were significantly increased in HIV-1-infected symptomatic subjects (P2) compared to controls. Seventy-five percent of asymptomatic patients (P1) also had increased values. On the other hand, a significant overlap in concentrations of both markers in serum was found between controls and P0 patients. Thirty-eight percent of the P0 patients had values comparable to those of the P2 group. Persistently high concentrations of both markers in P0 patients may be indicative of HIV-1 infection.

Changes in circulating levels of neuroendocrine and thymic hormones during aging in rats: a correlation study

It is well established that during early life the thymus gland and the neuroendocrine system influence each other's maturation. Furthermore, there is a growing body of evidence indicating that the immune and neuroendocrine systems also function as a bidirectional network during adult life. In order to assess possible changes in the thymic-neuroendocrine network during aging, we undertook to measure and correlate the circulating levels of several neuroendocrine and thymic hormones in young (3 month) and old (26 month) male Sprague-Dawley rats. Sequential plasma samples were obtained from chronically cannulated, nonstressed animals every 30 min for 5 h. Two days later rats were killed between 11:30 a.m. and 1:30 p.m. and trunk serum was obtained. All hormones were measured by radioimmunoassay. Growth hormone (GH), prolactin (PRL), thyrotropin (TSH) and corticosterone were measured in plasma, whereas thyroxine (T4), triiodothyronine (T3), thymosin alpha 1 (T alpha 1) and thymosin beta 4 (T beta 4) were determined in trunk serum. The circulating levels of T3, PRL, corticosterone and T beta 4 did not show significant differences between young and old rats, whereas GH, T4, T alpha 1, and thymus weight showed a significant age-related reduction. The anterior pituitary (AP) weight and plasma TSH were significantly higher in old than in young rats. Three pairs of parameters showed highly significant levels of linear correlation: AP weight vs. T alpha 1; thymus weight vs. T4 and T alpha 1 vs. T4 (p less than 0.01, p less than 0.001 and p less than 0.001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated levels of circulating immune complexes in human immunodeficiency virus infection

Circulating immune complexes were quantitated in asymptomatic intravenous drug abusers (IVDA), male homosexuals, and patients with lymphadenopathy or acquired immunodeficiency syndrome (AIDS) by two different methods. Circulating immune complexes were elevated in HIV-seronegative IVDAs and male homosexuals, probably reflecting viral infections such as cytomegalovirus (CMV). Circulating immune complexes were also elevated in HIV-seropositive IVDAs and male homosexuals and in patients with lymphadenopathy or AIDS, reflecting infections such as CMV and HIV.

Neopterin and alpha and beta interleukin-1 levels in sera of patients with human immunodeficiency virus infection

Levels of neopterin and alpha and beta interleukin-1 (IL-1) in sera of normal controls, asymptomatic intravenous drug abusers, homosexuals, and patients with lymphadenopathy or acquired immunodeficiency syndrome were measured. Neopterin levels were elevated in the sera of human immunodeficiency virus (HIV)-seronegative intravenous drug abusers and homosexuals, as well as in the sera of HIV-seropositive patients. Alpha IL-1 was the most predominant form of IL-1 found in the sera of all groups, and its level in HIV-seronegative intravenous drug abusers was elevated compared with the level in controls, whereas its levels in asymptomatic HIV-seropositive intravenous drug abusers and asymptomatic HIV-seronegative and HIV-seropositive homosexuals were decreased relative to the level in controls. Beta IL-1 levels in sera in all groups were not significantly different from the control value, except for the HIV-seropositive homosexual group; in this group the beta IL-1 level was significantly decreased compared with the control value.

MicroELISA method for the determination of thymosin beta 9 discriminating between thymosin beta 9 and the structurally closely related thymosin beta 4

In order to obtain specific antibodies against thymosin beta 9 showing minimal cross-reactivity with the highly homologous peptide thymosin beta 4, the N-terminal fragment 1-14 of thymosin beta 9 was used for immunization. These antibodies have been tested in a competitive ELISA and show less than 1% cross-reactivity with thymosin beta 4. On the other hand, antibodies raised against the native thymosin beta 9 (1-14) cross-react 35% with thymosin beta 4. Specific antibodies against thymosin beta 9 are important for studying the concentration and localization of thymosin beta 9 in thymus and other bovine tissues because thymosin beta 9 is always accompanied by thymosin beta 4. Using N-terminal fragments of thymosin beta 4-like peptides may be a general approach for obtaining specific antibodies since this part of sequence is less conserved in thymosin beta 4-like peptides.

Elevated soluble CD8 levels in sera of human immunodeficiency virus-infected populations

Soluble CD8 levels in sera were quantitated in asymptomatic intravenous drug abusers, homosexuals, and patients with lymphadenopathy or acquired immunodeficiency syndrome. Soluble CD8 levels were elevated in human immunodeficiency virus-seronegative intravenous drug abusers and homosexuals, probably reflecting infections like cytomegalovirus. The sera of human immunodeficiency virus-seropositive groups of patients with human immunodeficiency virus infection also had elevated levels of soluble CD8, reflecting infections like cytomegalovirus and human immunodeficiency virus infection.

A radioimmunoassay for parathymosin alpha using antibodies to synthetic N-terminal peptide 1-30

Antibodies against the N-terminus of rat parathymosin alpha have been raised in rabbits by conjugating parathymosin alpha (1-30) to hemocyanin. A radioimmunoassay for parathymosin alpha was established by utilizing antibodies against the above polypeptide and parathymosin alpha(1-12)[Tyr] as tracer. The useful range was 5-450 pmol for parathymosin alpha. An epitope was located in the amino acid sequence 1-12. The antiserum failed to crossreact with the same molar concentrations of the partly homologous thymosin alpha 1 or prothymosin alpha. With this radioimmunoassay, parathymosin alpha was isolated from calf thymus after separation from prothymosin alpha by reversed phase HPLC. Endogenous proteases did not appear to generate N-terminal fragments of parathymosin alpha in rat liver extracts in a similar fashion to that observed for prothymosin alpha. Parathymosin alpha has a ubiquitous distribution in the human tissues examined, with levels ranging from 93 (brain) to 1043 (liver) ng of parathymosin alpha(1-30) equivalents/g (wet weight).

MicroELISA detection of thymosin alpha 1 released in thymic organ cultures

Using a polyclonal specific rabbit anti-thymosin alpha 1 a highly sensitive enzyme-linked immunosorbent assay (ELISA) has been developed to measure thymosin alpha 1. Production of thymosin alpha 1 was detected in both thymic organ cultures and in mouse serum. The method is rapid (5 h), reproducible and easy to perform.

Elevated soluble interleukin-2 receptor levels in serum of human immunodeficiency virus infected populations

Soluble interleukin-2 receptor (SIL-2R) levels in sera were quantitated in asymptomatic intravenous drug abusers (IVDA) and in patients with lymphadenopathy or AIDS. The mean SIL-2R level in serum of normal controls was 158 +/- 19 compared to 368 +/- 35 U/ml in serum of HIV-seronegative asymptomatic IVDA. The mean SIL-2R in serum of HIV-seropositive asymptomatic IVDA was 609 +/- 85 U/ml and in patients with lymphadenopathy was 745 +/- 79 U/ml. In addition, AIDS patients with Pneumocystis carinii pneumonia, Kaposi's sarcoma, or both had elevated mean levels of SIL-2R values with a broad range. This elevated level of SIL-2R may reflect excessive cell surface IL-2R expansion by the infected cells.

The identification of prothymosin alpha-like material in vertebrate lymphoid organs by a radioimmunoassay for the N-terminal decapeptide

A radioimmunoassay (RIA) is described for the detection and quantitation of prothymosin alpha (ProT alpha), and its N-terminal fragments containing as a minimum the first ten amino acid residues. This range of peptides includes thymosins alpha 1 (T alpha 1) and alpha 11 (T alpha 11). Antibodies against T alpha 1 and the tracer T alpha 1(1-10)Tyr11(125I), an analogue of the major epitope, were utilized in this RIA. 50% displacement of the ligand was observed with 1.3 pmol of T alpha 1 and 6.4 pmol of ProT alpha. The partially homologous parathymosin alpha (ParaT alpha) showed less than 2% crossreactivity with ProT A. Sephacryl S-200 gel filtration separation of the peptides of calf thymus, chicken spleen and trout spleen extracts prepared by a method eliminating proteolysis, combined with the above RIA, showed the presence of a major immunoreactive peak. Its elution volume corresponded to that of rat ProT alpha (apparent mol. weight 36,000) for both calf (37,000) and chicken (35,000) tissues. In trout it corresponded to a significantly higher molecular weight (62,000). No detectable levels of shorter fragments, including T alpha 1, were observed in any of the above species. The levels of ProT alpha-like peptides in calf thymus, chicken spleen and trout spleen were found to be 246, 8.6 and 7.7 micrograms respectively, of rat ProT alpha equivalents per gram of fresh tissue. The significance of the presence of ProT alpha-like polypeptides in vertebrate species as distant as fish and mammals, the absence of short T alpha 1-like fragments, and the relative conservation of the N-terminus as suggested by the RIA is discussed.

Lack of reactivity of anti-human immunodeficiency virus (HIV) P17/18 antibodies against alpha 1 thymosin and of anti-alpha 1 thymosin monoclonal antibody against P17/18 protein

The blood rate of alpha 1 thymosin is increased during HIV infection, despite the thymus involution. Anti-alpha 1 thymosin antibodies inhibit HIV replication in vitro. A homology between alpha 1 thymosin and the HIV P17/18 core protein exists and would explain a cross-antigenicity. We have studied the interaction between anti P17/18 antibodies from HIV patients and alpha 1 thymosin and between an anti-alpha 1 thymosin monoclonal antibody and the P17/18 protein. We were unable to confirm any cross-reactivity. During acquired immune deficiency syndrome, a major involution of the thymus appears with a severe depletion of thymocytes and epithelial cells. Certain thymic functions are missing, as corroborated by the reduction of the hormone thymulin in the blood. At the same time, the blood rate of the 2 other hormones (partly of thymic origin), alpha 1 thymosin and beta 4 thymosin is increased. One of the theories explaining this discordance is that patients with acquired immunodeficiency syndrome produce molecules which have a cross antigenicity with these thymic hormones. Sarin et al. have recorded a 50% homology between the C-terminal part (last 18 aminoacids) of alpha 1 thymosin and the part between the 92nd and the 109th aminoacids of the HIV P17/18 protein. The cross reactivity between this P17/18 protein and alpha 1 thymosin would explain the high rates of alpha 1 thymosin found in the radio-immunoassay of sera from patients infected with HIV. Another result of this cross-reactivity is the ability of alpha 1 thymosin antibodies to inhibit HIV replication in the H9 permissive cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Neutralization of HTLV-III/LAV replication by antiserum to thymosin alpha 1

An antiserum prepared against thymosin alpha 1, a hormone secreted by the thymus gland, effectively neutralized the AIDS-associated virus [HTLV-III/LAV (clone BH-10)] and blocked its replication in H9 cells. Reverse transcriptase activity and expression of the HTLV-III/LAV antigens p15 and p24 were inhibited by purified immunoglobulin G preparations of antisera to thymosin alpha 1. The antiviral activity of the antiserum was found to be due to a region of homology between thymosin alpha 1 and p17, a product of the gag gene of HTLV-III/LAV. Comparison of the primary sequences of thymosin alpha 1 and the gag protein revealed a 44% to 50% homology in an 18-amino acid region, between positions 11 and 28 on thymosin alpha 1 and 92 and 109 on the gag protein. The effectiveness of the thymosin alpha 1 antiserum and of immunoglobulin G-enriched preparations in blocking replication of HTLV-III(BH-10) in H9 cells suggests a novel approach to the development of an AIDS vaccine. A vaccine directed against the gag protein might overcome the problem of genetic drift in the envelope region of the virus and be useful against all genetic variants of HTLV-III/LAV.