Effect of thymosin alpha one on specific antibody response and susceptibility to infection in young and aged mice

Thymosin α-1 in cancer therapy: Immunoregulation and potential applications

Thymosin α-1 (Tα-1) is an immunomodulating polypeptide of 28 amino acids, which was the first peptide isolated from thymic tissue and has been widely used for the treatment of viral infections, immunodeficiencies, and especially malignancies. Tα-1 stimulates both innate and adaptive immune responses, and its regulation of innate immune cells and adaptive immune cells varies under different disease conditions. Pleiotropic regulation of immune cells by Tα-1 depends on activation of Toll-like receptors and its downstream signaling pathways in various immune microenvironments. For treatment of malignancies, the combination of Tα-1 and chemotherapy has a strong synergistic effect by enhancing the anti-tumor immune response. On the basis of the pleiotropic effect of Tα-1 on immune cells and the promising results of preclinical studies, Tα-1 may be a favorable immunomodulator to enhance the curative effect and decrease immune-related adverse events of immune checkpoint inhibitors to develop novel cancer therapies.

Animal Models of Pneumococcal pneumonia

Streptococcus pneumoniae remains the most common bacterial pathogen causing lower respiratory tract infections and is a leading cause of morbidity and mortality worldwide, especially in children and the elderly. Another important aspect related to pneumococcal infections is the persistent rate of penicillin and macrolide resistance. Therefore, animal models have been developed to better understand the pathogenesis of pneumococcal disease and test new therapeutic agents and vaccines. This narrative review will focus on the characteristics of the different animal pneumococcal pneumonia models. The assessment of the different animal models will include considerations regarding pneumococcal strains, microbiology properties, procedures used for bacterial inoculation, pathogenesis, clinical characteristics, diagnosis, treatment, and preventive approaches.

The effect of thymosin α1 for prevention of infection in patients with severe acute pancreatitis

INTRODUCTION

Severe acute pancreatitis (SAP) is an acute inflammatory disease with prolonged clinical course, which is complicated by the presence of persistent organ failure and severe infection. Infection mainly occurs in the late phase of SAP and it is found to be the main cause of death. Therefore, developing strategies for the prevention of SAP-related infection has been a crucial approach to improve patients' outcomes. Due to remarkable immune-cells-regulating properties, thymosin α1 has been recognized as a promising immune therapy, especially in several infectious diseases. Recently, thymosin α1 has been given high expectations to exert clinical benefits in the prevention of SAP-related infection.

AREAS COVERED

The review of currently available strategies for SAP-related infection prevention and the use of thymosin α1 in SAP patients.

EXPERT OPINION

The current available strategies achieve limited success for preventing SAP-related infection. A possible explanation is that the trigger of infection, immunosuppression has not been concurrently resolved. The application of thymosin α1 in a clinical study showed a prophylactic effect against SAP-related infection. However, the use of thymosin α1 in SAP patients is still at an early stage of clinical investigation and requires high-quality and large sample size evidences.

Perspective: Should Vitamin E Recommendations for Older Adults Be Increased?

Current vitamin E requirements are uniformly applied across the population for those >14 y of age. However, aging is associated with alterations in cellular and physiologic functions, which are affected by vitamin E. Therefore, it is questionable whether vitamin E requirements can be uniformly applied to all adult age categories. With aging, there is dysregulation of the immune system in which there are decreased cell-mediated and pathogen defense responses coupled with an overactive, prolonged inflammatory state. Both animal and human studies in the aged suggest that intake above currently recommended levels of vitamin E may improve immune and inflammatory responses and be associated with a reduced risk of infectious disease. We review the evidence that was considered in establishing the current requirements for vitamin E and highlight data that should be considered in determining the vitamin E requirements in older adults, particularly focusing on the evidence suggesting a benefit of increased vitamin E intake on immune function and inflammatory processes and resistance to infection. The main objective of this Perspective is to initiate the discussion of whether the current Dietary Reference Intake for vitamin E should be increased for the older population. We make this suggestion on the basis of mechanistic studies showing biological plausibility, correction of a major cellular dysfunction in older adults, and strong evidence from several animal and a few human studies indicating a reduction in risk and morbidity from infections.

Nutritional modulation of age-related changes in the immune system and risk of infection

The immune system undergoes some adverse alterations during aging, many of which have been implicated in the increased morbidity and mortality associated with infection in the elderly. In addition to intrinsic changes to the immune system with aging, the elderly are more likely to have poor nutritional status, which further impacts the already impaired immune function. Although the elderly often have low zinc serum levels, several manifestations commonly observed during zinc deficiency are similar to the changes in immune function with aging. In the case of vitamin E, although its deficiency is rare, the intake above recommended levels is shown to enhance immune functions in the elderly and to reduce the risk of acquiring upper respiratory infections in nursing home residents. Vitamin D is a critical vitamin in bone metabolism, and its deficiency is far more common, which has been linked to increased risk of infection as demonstrated in a number of observational studies including those in the elderly. In this review, we focus on zinc, vitamin E, and vitamin D, the 3 nutrients which are relatively well documented for their roles in impacting immune function and infection in the elderly, to discuss the findings in this context reported in both the observational studies and interventional clinical trials. A perspective will be provided based on the analysis of information under review.

Immune Modulation with Thymosin Alpha 1 Treatment

Thymosin alpha 1 (Ta1) is a peptide originally isolated from thymic tissue as the compound responsible for restoring immune function to thymectomized mice. Ta1 has a pleiotropic mechanism of action, affecting multiple immune cell subsets that are involved in immune suppression. Ta1 acts through Toll-like receptors in both myeloid and plasmacytoid dendritic cells, leading to activation and stimulation of signaling pathways and initiation of production of immune-related cytokines. Due to the immune stimulating effects of Ta1, the compound would be expected to show utility for treatment of immune suppression, whether related to aging or to diseases such as infection or cancer. Extensive studies in both the preclinical and clinical setting will be summarized in the subsequent sections. These studies have demonstrated improvements in immune system cell subsets and the potential of Ta1 for the treatment of a range of diseases.

Historical review of thymosin α 1 in infectious diseases

INTRODUCTION

Thymosin α 1 (Tα1) is a peptidic biological response modifier, which plays a significant role in activating and regulating various cells of the immune system. For the above-mentioned activities it is expected to exert a clinical benefit in the treatment of diseases where the immune system is altered.

AREAS COVERED

Several clinical trials have been carried out with Tα1 for treatment or prevention of many different infectious diseases such as hepatitis B and C, sepsis and Aspergillosis in bone marrow-transplanted patients. Data available on the use of Tα1 in infectious disease as well as a vaccine enhancer will be reviewed to possibly generate new working hypothesis.

EXPERT OPINION

Tα1 has been widely used in thousands of patients. Nevertheless, there are some issues that have not yet been properly addressed (i.e., dose, schedule, combination treatments, end-points to be evaluated in clinical trials). In the most recent clinical trials Tα1 has been used at higher doses than those commonly used in the past showing a direct proportionality between the dose and the effect. The safety profile of Tα1 is excellent and it is virtually devoid of toxicity.

Thymosin α1 continues to show promise as an enhancer for vaccine response

Thymosin α1 (Tα1) is an immune-modulating peptide that can be expected to improve response to vaccinations, as stimulated dendritic cells and T cells can act in concert to increase antibody production along with an improved cytotoxic response from the T cells themselves. Tα1 demonstrated efficacy in preclinical studies; subsequently, it was shown to enhance response to vaccinations in difficult-to-treat populations, including individuals immune suppressed due to age or hemodialysis, and leading to a decrease in later infections. During the 2009 pandemic outbreak of H1N1 influenza, mouse and ferret studies confirmed that the use of higher doses of Tα1 allowed for fewer injections than those used in the previous clinical studies. In addition, a clinical study with Focetria™ MF59-adjuvanted monovalent H1N1 vaccine showed that treatment with Tα1 twice provided an earlier and greater response to the vaccine (P < 0.01).

Thymosin Alpha 1 as an Adjunct to Influenza Vaccination in the Elderly: Rationale and Trial Summaries

From a clinical perspective, the immune deficiency of aging (immune senescence) is not profound. In fact, it may be of little clinical consequence. However, older people are prone to chronic and debilitating disorders which alone, or in concert with the medications used in their treatment, may add to the age effect and create a more clinically relevant immune deficiency. As a result, many older people are susceptible to infection. Furthermore, it is now well recognized that older people respond less well to immunization protocols. Protection against influenza by vaccination with hemagluttinin is the prototype example. Despite programs that have raised vaccination rates dramatically over the past three decades, influenza remains a major cause of morbidity and mortality in the elderly. This, in part, is due to the fact that vaccine responses are reduced in older recipients. Strategies are under development to enhance vaccine efficacy in this population and one such strategy is the adjuvant use of thymosin alpha 1 (Talpha1). In both animal experiments and human trials, there has been demonstrated enhancement of vaccine responses. The findings to date warrant additional efforts to further examine the role of Talpha1 in augmenting specific vaccine responses both in the elderly or in younger subjects in situations in which there are suboptimal quantities of immunizing antigen available.

Future challenges in analysis and treatment of human immune senescence

Immune functions decline with age; immunorestorative approaches have been explored in laboratory animals and humans with definite, but limited success. In the clinical setting, the age-associated immune deficiency (immunesenescence) is compounded by the presence of comorbidities that are associated with a functional decline in immunity. Thus, any successful immune reconstitution strategy for humans must involve treatment of the underlying diseases. Furthermore, general health measures such as nutrition and exercises may have powerful effects on restoring immunity, to the extent that malnutrition and a sedentary lifestyle have contributed to existing immune deficiency. More selective approaches, such as with specific cytokines or organ transplantation are of experimental interest but are quite distant from achieving clinical applicability as interventions to restore immunity in the frail elderly.

Cell mediated immunity changes in ageing, relative importance of cell subpopulation switches and of nutritional factors

Decreased T-cell functions with ageing have been extensively described. This review focuses on recent data on changes in T-cell subpopulations related to ageing and their consequences on T-cell proliferation. Increase of immature T cells CD2+ CD3- is an ageing phenomenon related to T-cell declining proliferation. Recently it was shown that increase of immature T cells was due to an increase in different subtypes of the CD2+ CD3- population, double-negative CD2+ CD4- CD8- and double-positive CD2+ CD4+ CD8+ subpopulations, the former being associated with nutritional deficit, the latter with associated diseases. Other authors have focused on decreases of native T cells with parallel increase of memory T cells; such a switch is also relevant to declining T-cell proliferation. This review focuses on two major factors which influence immune ageing; nutritional parameters and antigen exposure.

Humoral immunity in aging

The interactions between B and T lymphocytes, leading to the development of humoral responses, are reviewed with references to the changes occurring in aged people. Aging is perceived as a process of impairment of immune functions; it is known that T cells from aged subjects have a reduced ability to produce IL-2. However, other functions seem to be upregulated in elderly subjects; indeed, IL-1, IL-3, IL-4, IL-6 and TNF alpha production are increased both in aged mice and humans. These cytokines are known to control B cell differentiation, through isotype switch and Ig production. A significant increase in IgG subclasses and IgA is observed in sera of aged subjects. This contrasts with the significant decrease in circulating B lymphocytes. The impairment of primary responses to immunization, and other aspects of humoral immunity, including mucosal responses, autoantibody production and correlations with phenotypic markers of T and B cell subsets, are discussed.

Effect of synthetic thymic hormones on the cocaine-induced inhibition of the primary immune response in mice

The effects of thymosin alpha 1 (T alpha 1) and thymopentin (TP5) on the cocaine-induced impairment of the primary antibody response to sheep red blood cells (SRBC) was studied. The administration of cocaine from day -4 to the day of immunization (day 0) induced a significant impairment of the response to the T-dependent antigen SRBC, as evaluated on day 5 post-immunization by the Splenocyte-Induced SRBC Hemolysis (SIH) assay. The analysis of the responses to immunogen elicited from each single mouse indicated that, under the experimental conditions used, cocaine acted by exerting more an "all or nothing" effect rather than by modulating the strength of the immune response. Both T alpha 1 and TP5, injected into mice during cocaine administration and for 4 days after, induced a significant recovery of the response to SRBC. Our experiments did not show any great differences in the overall efficacy of the two drugs, although they showed quite a different dose-response effect. The results of the present investigation demonstrated the capability of TP5 and T alpha 1 to reverse the cocaine-induced impairment of the response to SRBC and suggested that the effect of the two peptides may be related to their immunomodulating activities on T-cell functions.

Quantitative and qualitative analysis of anti-tetanus toxoid antibody response in the elderly. Humoral immune response enhancement by thymostimulin

In order to explore the humoral primary and secondary response to tetanus toxoid (TT), and to define the possible immunopotentiating effect of the thymic hormone thymostimulin, we studied 13 elderly people, selected according to the Senieur Eurage protocol, vaccinated against TT, an antigen never encountered before. Six of them were treated with thymostimulin before and during the immunization protocol. Specific anti-TT antibody level measurement and spectrotypic analysis were performed on the sera collected from the subjects at different times over the immunization protocol. In addition, spontaneous in vitro production of anti-TT antibodies as well as cutaneous delayed hypersensitivity reactions were also studied. Only one patient showed a detectable humoral immune response after the first immunization. After the booster, four of six thymostimulin-treated individuals, compared with only two of seven controls, showed in vivo anti-TT humoral response; at the same time, spontaneous anti-TT production was detected in peripheral blood mononuclear cells from five of six thymostimulin-treated individuals but only three of seven untreated controls. These differences were highly significant (p < 0.0001). In addition, only in thymostimulin-treated subjects were the levels of serum anti-TT antibodies 14, 21 and 28 days after the booster significantly (p < 0.05) higher than the baseline values. The spectrotypic analysis of anti-TT antibodies performed by isoelectric focusing and reverse blotting showed total agreement with the results from enzyme-linked immunosorbent assay.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of thymus supernatant on the thymus homing ability of aged murine bone marrow cells

This study examined the effect of thymus supernatant on the ability of bone marrow cells from senescent mice to home to the thymus. An in vitro and an in vivo assay were employed. The in vitro assay used a blind well migration of aged bone marrow cells to thymus supernatant across a membrane with 5-microns pores. The in vitro assay measured the ability of aged bone marrow to repopulate the thymus of an irradiated host. Our results support previous reports that the bone marrow from old mice has a greatly reduced ability to migrate to thymus supernatant and to repopulate the thymus of an irradiated host. Further, we found that a brief treatment of the old bone marrow with thymus supernatant significantly improved its thymus homing ability both in vitro and in vivo.

Immune dysfunction in the elderly: effect of thymic hormone administration on several in vivo and in vitro immune function parameters

The effects of short-term thymic hormone administration on age-associated immune function were evaluated. Two groups of individuals greater than 65 years of age were treated for 30 days with thymic extracts (TP1) or placebo; before and after this treatment a panel of in vitro and in vivo parameters was determined according to a very rigorous experimental protocol. In most individuals, TP1 treatment was associated with an improvement in cutaneous delayed-type response to PPD. Moreover, an increase in a circulating T cell subpopulation bearing the CD45R surface antigen ("virgin" T cells), and in NK cell cytotoxic activity was also observed in some subjects. Finally, lymphocyte responsiveness to PHA tended to increase, while no effect on lymphocyte ability to produce IL-2 following mitogen stimulation was observed. These findings suggest that TP1 treatment may influence age-related alterations in immune function parameters in some subjects.

Augmentation of influenza antibody response in elderly men by thymosin alpha one. A double-blind placebo-controlled clinical study

Influenza remains a major cause of illness and death in elderly people despite current vaccination programs. One factor is an immunization failure rate in the elderly that may be as high as 50%. To test whether administration of thymosin alpha 1 would result in greater antibody production, we administered it (900 micrograms/m2 subcutaneously twice weekly for eight doses) in conjunction with the 1986 trivalent influenza vaccine. Ninety men (65-99 years old, mean age 77.3 years) were randomized double-blind to receive thymosin alpha 1 or placebo by the same schedule; the sera from 85 of these men were acceptable for analysis. The two groups were similar with respect to underlying disease, medications, and age. No toxicity was observed in either group. Antibody response rate was defined as a four-fold rise in antibody titer over 3-6 weeks following vaccination and was measured by an enzyme-linked immunosorbent assay (ELISA). Analysis was performed on treatment groups and subgroups divided by the mean age: the older group consisted of subjects aged 77 years and older, and the younger group those aged from 65-76 years. Baseline and change in absolute antibody levels were compared by t test and using age as a continuous variable by multiple regression analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic immunoenhancement in the elderly: in vitro effects of isoprinosine

The loss of immune competence that occurs with aging may be responsible for increased morbidity and mortality in elderly individuals. Pharmacologic modulation of the immune response might reverse the immunologic aberrations associated with aging. We, therefore, investigated the effects of isoprinosine, an immunoenhancing drug, on selected in vitro immune responses in elderly subjects. Subjects studied were 65 years of age or older, and all had chronic diseases. We chose this population since they were at greatest risk for morbid events. Isoprinosine significantly enhanced mitogen-stimulated mononuclear cell proliferation, did not affect unstimulated cell growth, and needed to be present for the entire culture period for maximum effect. Isoprinosine is a potent in vitro immunoenhancing agent in aged humans.

Influenza vaccination in the elderly: improved antibody response with Imuthiol (Na diethyldithiocarbamate) adjuvant therapy

To improve influenza vaccine efficacy in hospitalized elderly, we compared the evolution of antibody level after vaccination in three patient groups. A sample of apparently primo vaccinated elderly were randomized to receive either Imuthiol (Na diethyldithiocarbamate: group 1) or a placebo (group P). They were compared to patients who had been vaccinated annually for several years (group C). All patients were immunized in the same week. Antibody responses increase within 15 days to reach a plateau in group P and C, while they continue to increase in the Imuthiol treated group, reaching higher antibody levels 30 days after vaccination. This higher antibody rise in group I is essentially due to higher antibody responses in patients with initially low antibody levels and who exhibited at least a four-fold antibody rise. This effect of Imuthiol on influenza antibody responses was observed in spite of a lower nutritional status in this group, a condition that induces lower antibody responses. The higher antibody responses observed in the Imuthiol treated group allow longer protection against influenza.

Immunization with heat-killed pneumococci, but not pneumococcal capsular polysaccharides, improves survival in splenectomized mice

Immunization with pneumococcal capsular polysaccharides (pn PS) is advocated after splenectomy to decrease the risk of overwhelming sepsis. The clinical and experimental evidence for the benefit of immunization after splenectomy is controversial. Various reports in the literature have claimed a benefit of immunization after splenectomy, but careful review of methodologies reveals that heat-killed pneumococci (pn) were used to immunize the experimental animals. Since we have not been able to protect splenectomized (splx) mice by immunization with pn PS, we compared survival after live pneumococcal aerosol challenge and antibody (Ab) responses in splx and sham splx mice immunized with either pn PS or heat-killed pn. Immunization with either heat-killed type 3 pn or pn type 3 PS improved survival in sham-splx mice compared to saline controls (p less than 0.001). Only immunization with heat-killed type 3 pn improved survival in splx mice (p less than 0.001), while pn PS had no effect on survival compared to saline splx controls. Ab responses to pn type 3 PS measured by enzyme linked immunosorbent assay were depressed in splx mice compared to sham-splx mice regardless of the method of immunization. Sham-splx mice immunized with heat-killed pn had higher Ab levels compared to mice vaccinated with pn PS (p less than 0.001) suggesting an adjuvant effect in sham-splx mice. The data suggest that immunization with pn PS may not be beneficial to a splx host. Improved survival after immunization with heat-killed bacteria in splx mice may be related to Ab responses to antigens other than the capsular polysaccharide.

The age-related decline in antibody response is transferred by old to young bone marrow transplantation

The immune response declines with age. This decline correlates with thymic involution and involves primarily a loss in T-cell function, whereas humoral immunity is more variably affected. In the current experiments we have measured immunoglobulin synthesis in vitro after mitogen stimulation, and specific antibody response after vaccination. We found that the response to pokeweed mitogen by non-specific immunoglobulin production, and the response to vaccine was shown to be transferred to lethally irradiated young mice by old to young bone marrow transplantation. Both pokeweed mitogen and tetanus toxoid require T-cell help for optimal response, and, therefore, our observations are in accordance with the age-associated decline in T-cell immunity. The finding that young hosts transplanted with old bone marrow produce less antibody than young hosts transplanted with young bone marrow highlights the importance of the decline in cellular function with age.

Interleukin-2 and aging: decreased interleukin-2 production in healthy older people does not correlate with reduced helper cell numbers or antibody response to influenza vaccine and is not corrected in vitro by thymosin alpha 1

The capacity of lymphocytes obtained from healthy young or old volunteers to produce interleukin-2 was measured and the results were compared with other measures of immune function. The in vitro effect of thymosin alpha 1 on interleukin-2 production was also measured. Interleukin-2 was lower in lymphocytes from the elderly, and individuals with low production also had lower proliferative responses in vitro to phytohemagglutinin. These individuals did not have a reduced helper T-cell number, abnormal ratio of helper to suppressor T-cells or reduced antibody production in response to vaccine. Thymosin alpha 1 did not have a consistent effect on interleukin-2 production.