The coronavirus disease 2019 (COVID-19) pandemic has prompted expedited vaccine development. Vaccinations have proven to be a safe and effective modality in preventing the transmission and spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen for COVID-19, as well as for curtailing the disease severity.
However, most approved vaccines were being tested on adults and the elderly, and only recently were messenger ribonucleic acid (mRNA) vaccines approved for children.
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Background
Individuals with rare diseases are susceptible to severe COVID-19 symptoms and until now, immunization efforts in this population have been meager, owing to the limited safety data of these new vaccines among individuals with rare diseases.
The type I interferonopathies, rare genetic disorders affecting the production of interferon (IFN), include Aicardi Goutières Syndrome (AGS), which is a neurologic disease with an early infantile-onset characterized by systemic inflammation and nucleic acid metabolism disruptions.
mRNA-based vaccines are deemed safer and more effective than other COVID-19 vaccines. The addition of lipid nanoparticles (LNPs) enhances the efficacy of mRNA delivery. Examples of the available nucleoside-modified mRNA LNP vaccines are – BNT162b (Comirnaty, Pfizer-BioNTech) and mRNA-1273 (Spikevax, Moderna).
AGS patients require immunosuppressive medications; thus, unvaccinated AGS patients harbor a higher risk for severe COVID-19. It remains to be established whether mRNA-based vaccines could activate potent innate immunity in individuals with rare diseases or if mRNA-LNP-based platforms are capable of mitigating such upregulation.
The study
A new study posted on bioRxiv * preprint server aimed to evaluate the immunostimulatory potential of mRNA vaccines in AGS patients.
The study entailed formulating nucleoside-modified mRNA into LNPs and assessing their impact on peripheral blood monocyte cells. For this, whole blood samples were collected from AGS patients and controls. Upregulation of IFN pathways in vitro, after the addition of mRNA-LNPs, was measured by assessing interferon signaling gene (ISGs) expression from whole blood.
Results
For validating the internalization, immunogenicity, and expression of SARS-CoV-2 di-proline modified spike sequence (S2P), mRNA-LNP (with di-proline-modified spike protein encoding) – 0.3µg/million cells were transfected into human dendritic cells (DCs) and high-density human embryonic kidney cell line (Expi293F cells).
Analysis through Western blot revealed that the spike (S) protein was efficiently translated after 24 hours of the transfection into the DCs and exhibited an expected band around 165 kDa. The lack of expression in the empty LNP control delineated the specificity of the S protein.
Nucleoside-modified mRNA-LNP were found to be non-immunogenic and harbored no detectable levels of tumor necrosis factor (TNF)-α. On the contrary, uridine-containing mRNA-LNP vaccines caused TNF-α elevations.
The expression of the di-proline-modified S protein was detected at high levels on cells transfected with the mRNA-LNP vaccine. Luciferase reporter mRNA was utilized to ascertain LNPs entry and expression into the cells after addition into human blood. The expression was found to be at least 1000-fold higher than the control; this finding confirmed the potential of mRNA-LNPs to transfect the target cells in human blood.
Additionally, the majority of AGS patients showed elevated ISG scores at baseline compared to controls, irrespective of whether they were on baricitinib therapy. After the administration of the unmodified mRNA-LNP vaccine, the ISG scores increased in AGS patient cells, as well as in control cells – with significant elevations compared to baseline in non-AGS controls. However, the ISG scores failed to increase after the nucleoside-modified mRNA-LNP vaccine.
Furthermore, empty LNP (eLNP) could not change or decrease the ISG expression on its own. Moreover, dose-dependent increases in specific IFN signature genes, as seen with unmodified mRNA-LNPs, were not observed with modified mRNA-LNP. Significant changes in expressions of other RNA sensing genes were not apparent between baseline and treatment.
Overall, differences amongst AGS and non-AGS individuals were only distinct for the nucleoside modified mRNA-LNP vaccine, compared to all vaccine types. The modified mRNA-LNP vaccine led to significant reductions in the ISG expression.
Thirty-five vaccinated individuals reported COVID-19 infection; of these, 12 infections were patient-reported. Three patients experienced COVID-19-related long-term health impacts. Among the 12 individuals with known COVID-19, eight were unvaccinated, two were vaccinated and the vaccination statuses of the remaining two were unknown.
Meanwhile, in 16 individuals, COVID-19 had not been confirmed; among these eight individuals had received COVID-19 vaccination. Among the (12) vaccinated, ten received mRNA vaccines, and two (adults) were given the Johnson & Johnson vaccine. Nine individuals reported no vaccine-related side effects while three had side effects, such as fever, myalgia, headache, and fatigue. None had unexpected side effects.
Inference
The safety and effectiveness of the approved COVID-19 vaccines have not been studied in patients with rare diseases. In vitro analysis of whole blood samples collected from AGS populations revealed that a systemic autoinflammatory response to the protein is probable after the administration of the mRNA vaccine. This may augment the ISG signaling, but may not be as robust as the autoinflammatory response observed after SARS-CoV-2 infection.
Therefore, individuals with AGS may benefit from the United States Food and Drug Administration (US FDA) approved mRNA vaccines, corresponding to their age, except for those in whom vaccine-related adverse effects have been documented.
*Important notice
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
