Clearance, biodistribution, and neuromodulatory effects of aluminum-based adjuvants. Systematic review and meta-analysis: what do we learn from animal studies?

Difference in the cellular response following THP-1 derived phagocytic monocyte cells exposure to commercial aluminum-based adjuvants and aluminum-containing vaccines

BACKGROUND

Aluminum-based adjuvants (ABAs) enhance the immune response following vaccine injection. Their mechanisms of action are not fully understood, and their bio-persistency have been described associated with long-term adverse effects.

METHODS

We evaluated and compared the cellular effects of the two main ABAs and whole vaccines on ATP production, ROS generation and cytokines production (IL-6 and IL-10), using THP-1 cells.

RESULTS

ABAs altered the cell energy metabolism by increasing ROS production after 24 h and reducing ATP production after 48 h. In addition, both ABAs and whole vaccines induced different kinetics of IL-6 production, whereas only ABAs induced IL-10 secretion.

CONCLUSION

This study showed clearly, for a first time, a difference in cellular response to the ABAs and whole vaccines which should be taken into consideration in future studies focusing on the effect of ABA in vaccines. Future studies on ABAs should also pay attention to mitochondrial function alterations following exposure to ABA-containing vaccines.

The Role of Acetylation and Methylation of Rat Hippocampal Histone H3 in the Mechanism of Aluminum-Induced Neurotoxicity

Aluminum is a known neurotoxin and a major environmental contributor to neurodegenerative diseases such as Alzheimer's disease (AD). We uesd a subchronic aluminum chloride exposure model in offspring rats by continuously treating them with AlCl3 solution from the date of birth until day 90 in this research. Then evaluated the neurobehavioral changes in rats, observed the ultrastructural changes of hippocampal synapses and neurons, and examined the level of hippocampal acetylated histone H3 (H3ac), the activity and protein expression of hippocampal HAT1 and G9a, and the protein expression level of H3K9 dimethylation (H3K9me2). The findings demonstrated that aluminum-treated offspring rats had impaired learning and memory abilities as well as ultrastructural alterations in hippocampal synapses and neurons. The level of histone H3ac was decreased along with decreased protein expression and activity of HAT1, while level of H3K9me2 was increased along with increased protein expression and activity of G9a.

A reactogenic "placebo" and the ethics of informed consent in Gardasil HPV vaccine clinical trials: A case study from Denmark

BACKGROUND

Medical ethics guidelines require of clinical trial investigators and sponsors to inform prospective trial participants of all known and potential risks associated with investigational medical products, and to obtain their free informed consent. These guidelines also require that clinical research be so designed as to minimize harms and maximize benefits.

OBJECTIVE

To examine Merck's scientific rationale for using a reactogenic aluminum-containing "placebo" in Gardasil HPV vaccine pre-licensure clinical trials.

METHODS

We examined the informed consent form and the recruitment brochure for the FUTURE II Gardasil vaccine trial conducted in Denmark; and we interviewed several FUTURE II trial participants and their treating physicians. We also reviewed regulatory documentation related to Gardasil vaccine approval process and the guidelines on evaluation of adjuvants used in human vaccines.

RESULTS

It was found that the vaccine manufacturer Merck made several inaccurate statements to trial participants that compromised their right to informed consent. First, even though the study protocol listed safety testing as one of the study's primary objectives, the recruitment brochure emphasized that FUTURE II was not a safety study, and that the vaccine had already been proven safe. Second, the advertising material for the trial and the informed consent forms stated that the placebo was saline or an inactive substance, when, in fact, it contained Merck's proprietary highly reactogenic aluminum adjuvant which does not appear to have been properly evaluated for safety. Several trial participants experienced chronic disabling symptoms, including some randomized to the adjuvant "placebo" group.

CONCLUSION

In our view, the administration of a reactive placebo in Gardasil clinical trials was without any possible benefit, needlessly exposed study subjects to risks, and was therefore a violation of medical ethics. The routine use of aluminum adjuvants as "placebos" in vaccine clinical trials is inappropriate as it hinders the discovery of vaccine-related safety signals.

Concentrations, Number of Doses, and Formulations of Aluminium Adjuvants in Vaccines: A Systematic Review with Meta-Analysis and Trial Sequential Analysis of Randomized Clinical Trials

Aluminium adjuvants are commonly used in vaccines to boost the effects of vaccination. Here, we assessed the benefits and harms of different aluminium adjuvants vs. other aluminium adjuvants or vs. the same aluminium adjuvant at other concentrations, administered a different number of doses, or at different particle sizes used in vaccines or vaccine excipients. We conducted a systematic review with meta-analysis and Trial Sequential Analysis to assess the certainty of evidence with Grading of Recommendations Assessment, Development and Evaluation (GRADE). We obtained data from major medical databases until 20 January 2023 and included 10 randomized clinical trials of healthy volunteers. The comparisons assessed higher vs. lower aluminium adjuvant concentrations; higher vs. lower number of doses of aluminium adjuvant; and aluminium phosphate adjuvant vs. aluminium hydroxide adjuvant. For all three comparisons, meta-analyses showed no evidence of a difference on all-cause mortality, serious adverse events, and adverse events considered non-serious. The certainty of evidence was low to very low. None of the included trials reported on quality of life or proportion of participants who developed the disease being vaccinated against. The benefits and harms of different types of aluminium adjuvants, different aluminium concentrations, different number of doses, or different particle sizes, therefore, remain uncertain.

Inflammation and Autophagy: A Convergent Point between Autism Spectrum Disorder (ASD)-Related Genetic and Environmental Factors: Focus on Aluminum Adjuvants

Autism spectrum disorder (ASD), schizophrenia, and bipolar disorder are genetically complex and heterogeneous neurodevelopmental disorders (NDDs) resulting from genetic factors and gene-environment (GxE) interactions for which onset occurs in early brain development. Recent progress highlights the link between ASD and (i) immunogenetics, neurodevelopment, and inflammation, and (ii) impairments of autophagy, a crucial neurodevelopmental process involved in synaptic pruning. Among various environmental factors causing risk for ASD, aluminum (Al)-containing vaccines injected during critical periods have received special attention and triggered relevant scientific questions. The aim of this review is to discuss the current knowledge on the role of early inflammation, immune and autophagy dysfunction in ASD as well as preclinical studies which question Al adjuvant impacts on brain and immune maturation. We highlight the most recent breakthroughs and the lack of epidemiological, pharmacokinetic and pharmacodynamic data constituting a "scientific gap". We propose additional research, such as genetic studies that could contribute to identify populations at genetic risk, improving diagnosis, and potentially the development of new therapeutic tools.