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Original Studies |
Department of Medicine (H.D.D., A.B-Y., G.F.), Geriatric Unit, Hadassah University Hospital, Ein-Karem; Department of Virology (Z.Z-R.), Hebrew University - Hadassah Medical School; Department of Endocrinology and Metabolism (D.J.G.), Hadassah University Hospital, Ein-Karem, Jerusalem, Israel
Address correspondence and requests for reprints to: H. D. Danenberg, Department of Medicine, Hadassah University Hospital, Ein-Karem, Jerusalem POB 12000, Israel 91120.
| Abstract |
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Methods. Seventy-one elderly volunteers age 6189 yr were enrolled in a prospective randomized, double-blind study to receive either DHEA (50 mg qd p.o. for four consecutive days starting two days before immunization) or placebo. Antibody response to the vaccine was measured before and 28 days after vaccination.
Results. DHEA treatment significantly increased serum DHEA-sulfate (DHEA-S). No enhancement in established immunity was observed. A significant decrease in attainment of protective antibody titer (1:40 or higher) against the A/Texas strain in subjects with nonprotective baseline antibody titer was recorded following DHEA treatment compared with placebo (52% vs. 84%, P < 0.05). Baseline DHEA-S serum levels were inversely related to attainment of immunization in DHEA-treated subjects. Influenza-like morbidity during the winter was low in the study group with no difference between the DHEA and placebo groups.
Conclusions. Although highly effective in aged rodents, a short course of DHEA treatment did not improve the age-related declined response to immunization against influenza in human subjects. Higher baseline DHEA-S levels are not predictive of better immunization against influenza in the elderly.
| Introduction |
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Dehydroepiandrosterone (DHEA) is an abundantly secreted, weak androgenic adrenocortical steroid hormone. Concentrations of DHEA and its sulfatic ester (DHEA-S) decline after the third decade of life, reaching in the elderly 1020% of the peak level (10). It has been suggested that this age-related decline might be involved in major consequences of aging, including the aging of the immune system (11). Treatment of aged mice with DHEA reversed some of the phenomena typical of immunosenescence, including age-related changes in cytokine production and the defective immunization (11, 12).
Recently we have shown that treatment of aged mice by a single injection of DHEA increased their immune response to influenza vaccination. The age-associated decline in antibody production was reversed and the mice were protected against a challenge by a live influenza virus (13).
The present study was designed to examine the effect of DHEA treatment on vaccination of elderly persons against influenza.
| Materials and Methods |
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The study was conducted in a double-blind manner. Participants were randomly assigned to receive either DHEA or placebo capsules. DHEA (Akzo, Oss, Holland) capsules of 50 mg were administered once daily in the morning for a total of four sequential days starting two days before vaccination.
Serum DHEA-S and cortisol levels were measured before the study in all subjects by specific radioimmunoassays (DPC, Los-Angeles, CA.). Measurements were repeated 24 h after administration of the second dose in every sixth participant.
Antibody level studies were performed in a standard microtiter assay for hemagglutination-inhibiting (HAI) antibodies. Serum was treated with receptor-destroying enzyme (RDE) (Sigma, St. Louis, MO) overnight, heat-inactivated (56 C for 30 min), and its capacity to inhibit the agglutination of chicken red blood cells by influenza hemagglutinin was determined as described previously (14).
The following parameters were used for expression of humoral immune response: a) Log2 of HAI antibodies before and four weeks after vaccination, b) mean-fold increase of HAI titer after vaccination, c) proportion of subjects showing protective titer,i.e. HAI antibody titer at least 1:40.
Side-effects of the vaccination regimen and flu-like morbidity during the following winter were recorded by telephone-based interview at days 7, 28, and 120 after vaccination.
Statistical analysis of the significance between baseline and postimmunization titers was determined by the paired t test. Differences in elicitation of protective HAI antibody titer were determined using Fishers exact test.
| Results |
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Local adverse effects to the influenza vaccine were recorded in three subjects of the DHEA group and two of the placebo group. Systemic (flu-like) reactions to the vaccine were reported by one subject in each group. Five subjects reported improved well-being, both mental and physical, during the week of vaccination. All five received DHEA.
Following exclusion of subjects with baseline protective titers pre-
and post-immunization titers, mean-fold increase (MFI) in titer, and
the ability to raise HAI antibody titer to protective levels were
compared (Table 2
). Higher
post-immunization levels and MFIs were recorded in the placebo group
against the two influenza A strains. However, no statistical
significance appeared in these parameters. No difference was observed
against the influenza B. Accomplishment of protective titers against
all three influenza strains was higher in the placebo-treated group,
with significantly higher response against the A/Texas strain.
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| Discussion |
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Such results were not found in humans. In accordance with previous studies (3, 15), the immune response of the elderly to influenza vaccine was indeed incomplete, with protective rates in susceptible subjects treated with placebo ranging between 25% against the B/Harbin strain and 84% against the A/Texas. However, the results in DHEA-treated subjects were even more disappointing with protection ranging between 3152%. A significantly lower attainment of protective immunity against the A/Texax strain was observed in the DHEA group. Thus, DHEA treatment elicited decreased immune response against the H1N1 influenza strain. We can further speculate that the lack of statistical significance favoring placebo over DHEA in the two other strains is possibly due to the small number of subjects in our study.
A recently published study examined the efficacy of DHEA-S treatment as an adjuvant for influenza vaccine in 67 elderly subjects (16). Although not statistically significant, a trend in favor of DHEA-S was observed in immunization to all three components of the influenza vaccine (16). The major difference between that study and ours is the shorter 2-day regimen and the use of DHEA-S instead of DHEA. The prolonged increased plasma levels of DHEA-S in our DHEA-treated subjects probably precludes the difference in DHEA formulation as an explanation for the difference. We cannot conclude whether a shorter regimen is preferable. Based on two studies that showed an immunomodulating effect for DHEA in which longer periods of treatment were sustained (17, 18), a 4-day regimen seemed a reasonable and clinically applicable alternative for checking the above alternative.
The inverse correlation between baseline DHEA-S levels and immunization rate in DHEA-treated subjects adds further evidence to our findings that increasing DHEA-S levels does not improve, and may even harm, immunization against influenza in humans.
DHEA-induced decrease in immunization could be the result of augmented
IL-2 production by CD4+ cells (19). IL-2, by increasing the production
of interferon-
, enhances the clearance of viral particles. This
prevents a proper presentation of antigen to the naive T cells (20),
which are already decreased in number in the elderly (6). Therefore,
induction of rapid viral clearance may make DHEA treatment beneficial
in viral infection, but may jeopardize immunization.
Numerous data concerning the therapeutic ability of DHEA in age-related diseases such as atherosclerosis (21) and cancer (22, 23) were collected from studies in mammals and rodents. Reversal of immunosenescent phenomena and augmentation of the age-associated decline in immunization were repeatedly observed in mice (11, 12, 13). Why werent these results reproduced in the present study? The adrenal glands of rodents are incapable of synthesizing DHEA, with undetectable levels of circulating DHEA (24). Thus, no age-associated decline in DHEA production is found in mice, and therefore extrapolating the results of murine DHEA studies to humans is not obvious. Moreover, mice were treated with pharmacological doses of the drug that, if repeated in humans, would be well above 100 g/day per subject, thus violating our requirement for physiologic replacement therapy. The incomplete age-associated decline of the humoral response in humans, compared with the almost total decline observed in mice renders difficult the interpretation of immunosenescence studies in rodents with respect to the human situation. However, it may be possible that DHEA can boost primary immune responses, as observed in mice, and fails to enhance secondary immune responses that follow influenza vaccination in humans.
The minimal adverse effects of the vaccine are comparable to other studies in elderly populations (25). The self-reported, improved well-being following DHEA treatment was previously reported by Morales et al. (26). In that study, 67% of the men and 84% of the women recipients of DHEA (50 mg for 6 months) reported such a sensation. In the present study, only 15% of the DHEA-treated volunteers reported improved well-being compared with none of the placebo-recipients. Nevertheless, taking into account the short 4-day treatment period, the present results are in keeping with the cited results.
The notion that DHEA is the "fountain of youth" has apparently been scientifically substantiated in three respects: DHEAs age-associated decline; epidemiological studies suggesting that higher DHEA-S levels confer increased longevity (27); and numerous animal studies that convincingly demonstrated beneficial effects of DHEA administration in preventing atherosclerosis (19), cancer (20), and immunosenescence (12). These led to administration of DHEA to aged men and women (28) despite the lack of established beneficial effects. The present study did not confirm its base-line hypothesis that a short course of DHEA combined with influenza vaccine is effective as an adjuvant therapy in an elderly population. Moreover, it may even be detrimental to immunization. Therefore, until further data on the beneficial and adverse effects of DHEA is collected in clinical trials, caution should be used in dispensing DHEA.
| Footnotes |
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Received April 7, 1997.
Revised June 9, 1997.
Accepted June 11, 1997.
| References |
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