The ethics of placebo-controlled trials for perinatal transmission of HIV in developing countries

Structural and phenotypic modifications of rat thymocytes from birth up to one year of age, i.e. during maturation and at the beginning of the involutive process of the thymus are described. Since the biological significance and the mechanisms of thymic involution are still a matter of debate, this study aims at clarifying the complexity of the compensatory events occurring during this relatively neglected period of time. Thymuses from Sprague-Dawley rats were analyzed morphologically and morphometrically by light and electron microscopy. At the same time, thymocyte subsets, isolated from the same animals, were characterized by flow cytometry according to physical parameters and phenotypic markers. Results indicate that major changes occur during the first month from birth and from six months onward. In particular, already during the first weeks after birth, thymocytes undergo a slight reduction of mitoses associated with an increased number of apoptoses. Moreover, during the same period of time, flow cytometry revealed an expansion of small thymocytes and changes in thymocyte subsets such as increase of CD4+CD8+ and CD5+alpha(beta)TCR- and a decrease of CD4-CD8-, CD4-CD8+ cells. The thymus of adult rats was characterized by time-dependent decrease of both mitoses and apoptoses, progressive physical disconnection among cells, increase of necrotic areas and fibrosis. Around one year of age tissue changes were associated with a dramatic reduction of the population of large thymocytes and the rise of numerous small thymocytes that were unexpectedly negative for all tested markers. By contrast, medium-size thymocytes exhibited a marked decrease of CD4+CD8+ and CD5+alpha(beta)TCR- subsets. In conclusion, our data indicate that thymus undergoes, with time, a complex remodeling and suggest that thymic involution is not only a simple shrinkage of the organ but rather the result of a series of compensatory mechanisms among different cell populations in a setting of progressive involution.     

Feasibility of northern Thai factory workers as participants in HIV vaccine trials

Globoid cell leukodystrophy, or Krabbe disease, is a severe, autosomal recessive disorder resulting from a deficiency of galactocerebrosidase (GALC) activity. GALC is responsible for the lysosomal catabolism of certain galactolipids, including galactosylceramide and psychosine. In addition to the human patients, there are several naturally occurring animal models for this disease, including the twitcher mouse, West Highland White terriers (WHWT), and Cairn terriers. All species have deficient GALC activity and have the characteristic pathological findings in the nervous system. We now describe the cloning of the canine GALC cDNA and the identification of the disease-causing mutation in both terrier breeds. The 2007-bp open reading frame is 88% identical to that in human, and the deduced amino acid sequence is about 90% identical. However, the 3'-untranslated region is about 1 kb shorter than that in the human. Two nucleotide changes were found in affected dogs, an A to C transversion at cDNA position 473 (Y158S) and a C to T transition at position 1915 (P639S). Expression studies in COS-1 cells demonstrated that the A to C change at 473 is the disease-causing mutation. A rapid test for the identification of the genotype at that position has been developed, and over 100 WHWT and Cairn terriers have been screened. This will allow breeders to mate their dogs selectively and will permit the establishment of a colony of dogs for use in therapy trials.     

The varicella vaccine. Clinical trials in immunocompromised individuals

A review of the use of live attenuated varicella vaccine in immunocompromised children, particularly those with underlying leukemia in remission, is presented. Data concerning safety, immunogenicity, and efficacy of this vaccine in high-risk children are reviewed. The unique contributions toward our understanding of varicella vaccine, including spread of vaccine-type virus, incidence of zoster, and immune correlates provided by studies of immunocompromised patients are discussed. The importance of protecting high-risk children against severe varicella by the use of varicella vaccine is apparent.     

Research ethics and HIV/AIDS

The effect of 2-chloroadenosine (2CA), an adenosine receptor agonist, on the activation status of mouse natural killer (NK) cells was determined. Splenic lymphocytes incubated with 2CA exocytosed an NK cell-associated granzyme with N alpha-CBZ-L-lysine thiobenzyl ester (BLT) esterase activity in a dose- and time-dependent manner. Selective depletion of NK cells by anti-asialoGM1 antibody plus complement pretreatment confirmed that NK cells were the source of the BLT esterase activity. 2CA-induced granule exocytosis was not reduced in the presence of the nucleoside uptake blockers NBTI, dilazep, or dipyridamole, indicating the involvement of an extracellular receptor. However, adenosine or other A1, A2, or A3 cell-surface adenosine receptor agonists failed to trigger the exocytotic process. Furthermore, the nonselective adenosine receptor antagonist theophylline, as well as the selective A1 receptor antagonist DPCPX and the selective A2 receptor antagonist DMPX, did not interfere with 2CA-induced BLT esterase secretion. These data suggest that 2CA acts on NK cells via a novel (non-A1/A2/A3) cell-surface receptor. Genistein, a protein tyrosine kinase inhibitor, and calphostin C, a protein kinase C inhibitor, both interfered with 2CA-induced granule exocytosis. Pertussis toxin, an ADP-ribosylating toxin to which certain GTP-binding proteins are sensitive, also inhibited 2CA-stimulated BLT esterase release. In addition, 2CA-induced granule exocytosis was reduced in the presence of cyclosporin A, an inhibitor of Ca(2+)-dependent signaling pathways, and the Ca(2+)-chelating agent EGTA. We conclude that 2CA, acting through a novel extracellular receptor on mouse NK cells, triggers granule exocytosis via a Ca(2+)-dependent signal transduction pathway that is coupled to GTP-binding proteins and involves protein tyrosine kinase and protein kinase C activation.     

Preventing discrimination against volunteers in prophylactic HIV vaccine trials: lessons from a phase II trial

OBJECTIVE: This was a randomized, double-blind, crossover study of 30 children with attention-deficit/hyperactivity disorder (ADHD) that evaluated the time course effects of four doses of Adderall (5, 10, 15, and 20 mg), an inactive control (placebo), and a positive control (clinical dose of methylphenidate). METHOD: For each treatment condition, a capsule was administered in the morning and assessments were performed in an analog classroom setting every 1.5 hours across the day. Subjective (teacher ratings of deportment and attention) and objective (scores on math tests) measures were obtained for each classroom session, and these measures were used to evaluate time-response and dose response effects of Adderall. RESULTS: For doses of Adderall greater than 5 mg, significant time course effects were observed. Rapid improvements on teacher ratings and math performance were observed by 1.5 hours after administration, and these effects dissipated by the end of the day. The specific pattern of time course effects depended on dose: the time of peak effects and the duration of action increased with dose of Adderall. CONCLUSIONS: This documentation of efficacy in a controlled study supports the addition of Adderall to the armamentarium of psychotropic medications for the treatment of ADHD. The differences in time-response patterns of Adderall and methylphenidate may help tailor treatment to meet specific clinical needs of different children with ADHD.     

Readiness of high-risk populations in the HIV Network for Prevention Trials to participate in HIV vaccine efficacy trials in the United States

OBJECTIVE: To determine the willingness of populations at high risk of HIV-1 infection to participate in HIV vaccine efficacy trials, determine factors influencing decision-making, and evaluate knowledge levels of vaccine trial concepts. DESIGN: Cross-sectional study. METHODS: HIV-1-negative homosexual men, male and female injecting drug users and non-injecting women at heterosexual risk were recruited in eight cities in the United States (n=4892). RESULTS: A substantial proportion of the study population (77%) would definitely (27%) or probably (50%) be willing to participate in a randomized vaccine efficacy trial. Increased willingness was associated with high-risk behaviors, lower education level, being uninsured or covered by public insurance, and not having been in a previous vaccine preparedness study. Altruism and a desire for protection from the vaccine were major motivators for participation. Major concerns included positive HIV-1 antibody test due to vaccine, safety of the vaccine, and possible problems with insurance or foreign travel. Baseline knowledge of vaccine trial concepts was low. CONCLUSIONS: It is likely that high-risk volunteers will be willing to enroll in HIV vaccine efficacy trials. A variety of participant and community educational strategies are needed to address participant concerns, and to ensure understanding of key concepts prior to giving consent for participation.     

Evaluation of a video-supplement to informed consent: injection drug users and preventive HIV vaccine efficacy trials

In rats injected with bacterial lipopolysaccharide (LPS; 5 gamma mg/g body weight [BWT]), the toxin provokes death within 24 h in 23% of the animals and, in surviving rats, causes a decrease in BWT, hyperlactacidemia, hyperlipacidemia, and hyperketonemia, as well as depletion of both liver and muscle glycogen content. In the liver, LPS severely lowers the ATP and total adenine nucleotide content, ATP/ADP ratio, and adenylate charge. In hepatocytes from LPS-injected rats, the oxidation of D-glucose is first increased 2 h after administration of the toxin, despite close-to-normal phosphorylation of the hexose. In hepatocytes prepared from rats killed 24 h after injection of LPS, the phosphorylation of D-glucose, its incorporation into glycogen, and its oxidation are all severely impaired. This sequence of changes, which coincides with a decreased ratio between pyruvate and lactate production from exogenous D-glucose, is comparable to that found with agents that uncouple oxidative phosphorylation. The injection of LPS also alters the metabolic response of hepatocytes to the dimethyl ester of succinic acid (SAD), in terms, for instance, of the sparing action of the ester upon both the production of 14CO2 by hepatocytes prelabeled with L-[U-14C] glutamine and the output of NH4+, and its inhibitory action on glycogenolysis and futile cycling in the reactions catalyzed by glucokinase and glucose-6-phosphatase. Nevertheless, the infusion of SAD protects the rats against the deleterious effect of LPS upon such variables as the plasma concentration of free fatty acids and beta-hydroxybutyrate, the liver ATP content, and the oxidation of D-glucose, as well as the pyruvate/lactate ratio, in hepatocytes prepared from the LPS-injected rats. The infusion of SAD also virtually suppresses lethality in the LPS-injected animals. It is proposed, therefore, that the infusion of succinic acid esters may represent a novel therapeutic approach in endotoxemia and multiple-organ failure.     

Implications of socio-cultural contexts for the ethics of clinical trials

BACKGROUND: Health technology assesment (HTA) requires scientifically rigorous experimentation involving patients as subjects. HTA itself is required so that treatment given to patients will be both effective and efficient; this requirement is itself ethical in nature. At the same time it is essential that the methods used in HTA are ethically sound. Most healthcare researchers agree that the most effective and soundest method for assessing treatments is the randomised controlled trial (RCT). However, some researchers believe that the RCT is unethical, either in essence, or for use in some forms of medical research and HTA. Furthermore, many patients seem unable to understand the principles and purposes of the RCT, a factor which is highly detrimental for the validity of informed consent. Informed consent is the key to the ethics of medical research, both in most theories and in all codes of research conduct. Many RCTs therefore risk being unethical in practice, even if ethical in principle. AIM OF REPORT: To survey the main objections to the RCT and its alternatives. To assess the philosophical and methodological basis of these objections, and of the methods recommended for addressing them. To identify areas where objections are founded in social or cultural factors normally overlooked in ethical argument about the RCT methodology. To identify alternative arguments or methods which might resolve ethical conflicts in this area. HOW THE RESEARCH WAS CONDUCTED: The methods used were adapted from systematic reviews in medicine. Systematic searches of Medline, Psychlit and Sociofile CD-ROM databases; hand-searches of the major journals in general medicine and surgery, medical ethics and philosophy; and searches of books were carried out. The literature survey was restricted to articles published or abstracted in English. A database of the most relevant and useful materials was compiled, and is accessible on the Internet (http://www.liv.ac.uk/sdthomps/page1.html). RESEARCH FINDINGS: UNDERSTANDING RCTS AND THEIR ALTERNATIVES: There is some evidence of difficulty in understanding the aims and methods of RCTs, and some disquiet about elements of the RCT methodologies. These objections are well known and much discussed, and concern the use of placebo, the continuation of trials after significant differentials in benefit or harm are apparent, and randomisation. CULTURAL OR RELIGIOUS OBJECTIONS: There was an absence of evidence of cultural or religious objections to randomisation, placebo or other kinds of controlled prospective trials. This most likely reflects an absence of research rather than absence of objections. (ABSTRACT TRUNCATED)     

Clinical trials of varicella vaccine in healthy children

The Oka varicella vaccine has been tested in clinical trials worldwide in thousands of children. Following licensure in Japan, Korea, Germany, and the United States, the vaccine has been used in several millions of children. The vaccine has been generally well-tolerated with the most common complaints being pain and redness at the injection site and a mild rash following vaccination. The incidence of herpes zoster has not increased in vaccinees and may have decreased. Efficacy rates vary between 65% and 100% depending on the intensity of exposure to natural varicella and the potency of the vaccine. In those few vaccinees who develop MVLS, the rash is generally milder than seen following natural infection (median < 50 versus 300 lesions, respectively, as well as a lower incidence of fever). There has been no evidence to date to indicate waning immunity postvaccination. Studies are in progress in the United States to evaluate whether this will occur and the effect of booster doses of vaccine. It is expected that in countries where there is widespread use of the vaccine in healthy children, disease rates will fall dramatically as will the morbidity and mortality associated with natural varicella in this population.     

What is required of an HIV vaccine?

Mounting evidence suggests that the early dissemination of HIV in human beings evokes an immune response that is responsible for containment of the infection during the long symptom-free period. Loss of this immune control coincides with a final escalation of the viraemia and the terminal failure of the immune system. Other studies imply that pre-emptive vaccination of monkeys with attenuated forms of simian immunodeficiency virus (SIV) produces a substantial degree of resistance to superinfection with fully virulent viruses. Here we consider how observations from natural and experimental systems might influence thought as to what is required to produce safe induced immunity against HIV. We concentrate on three questions: what is the nature of the immune response that contains the infection? How does this response fail? How could a vaccine enhance protective immunity so that it exceeds the efficacy of this natural response?     

Semi-parametric models for mismeasured exposure information in vaccine trials

Exposure to infection information is important for estimating vaccine efficacy, but it is difficult to collect and inherently prone to missingness and mismeasurement. It is, therefore, generally not feasible to collect good exposure information on all participants in a large vaccine trial. We discuss study designs that collect detailed exposure information for only a small subset of trial participants, while collecting crude exposure information on all participants, and treat estimation of vaccine efficacy in the missing data/measurement error framework. We demonstrate with the example of an HIV vaccine trial the improvements in bias and efficiency when we combine the different levels of exposure information to estimate vaccine efficacy for reducing both susceptibility and infectiousness. We compare the performance of recently developed semi-parametric missing data methods of Pepe and Fleming and Carroll and Wand, Robins, Hsieh and Newey, and Reilly and Pepe.