Skimune® – Sensitisation & Immunotoxicity

Harness the complexity of human tissue.

Skimune® is a human skin based assay which harnesses the power of both human skin and autologous blood cells as the basis for a sensitive immunotoxicity/ hypersensitivity platform which accurately predicts human responses. 

Why do we use the skin?

The human skin is immunocompetent due to its role as a physical barrier, presence of immune cells like Langerhans cells, T-cells, Dendritic cells etc., production of antimicrobial peptides, ability to trigger inflammatory responses, existence of skin-associated lymphoid tissue (SALT), presence of immunoglobulins, and its capacity to develop immunological memory.

Together with the use of autologous blood, we use human skin as the basis for a extraordinarily powerful assay for the detection of immunological activation and clinical predictability.

The sensitivity and translatability of our assay can predict immunological responses which are regularly missed by simple cell based assays E.g. Cytokine release/ cellular proliferation assays

Our assay can characterise immunological reactions in a wide range of applications such as chemicals, cosmetics, pharmaceuticals, cellular therapies, biologicals (monoclonal and Bispecific antibodies) and gene therapies. Our assay has been widely published and validated to give you clinically relevant insights into the immunotoxicity characteristics of your test articles.

We have developed our assay to test for sensitisation and immunotoxicity in the skin and as a test for more general systemic immune responses.

Key readouts include
1. Histopathological analysis is performed on the skin, and damage graded from I-IV
2. ELISA/ multiplex MSD/ Luminex analysis of culture supernatants
3. qPCR / mRNA expression
4. High throughput RNAseq analysis
5. Immunohistochemistry

Figure 1 – Overview of Skimune® human tissue assay system. Isolated monocytes from our volunteer blood samples are used to produce dendritic and T-cell populations. The test articles are exposed to the dendritic cells potentially maturing them. These dendritic cells are then co-cultured with autologous T-cell populations to produce a T-cell mediated reponse. These cells are finally co-cultured with the autologous skin explant in order to assess lymphocyte mediated tissue damage. This damage can be characterised though histological assessment, IHC, qPCR etc.
The benefits of Skimune are;

1. Primary human tissue-based from varied donors, allowing for a more detailed understanding of immunotoxicity across age groups, sex and other demographics.

Does not rely on 2D cultures of cells.

3. Our dynamic assay is capable of a wide array of readouts. Specifically, Skimune® can cover both key event 2, 3 and 4 in the sensitisation pathway (Figure 3).

4. Saves time and money in product development compared to other available tests.

5. Capable of distinguishing the type of hypersensitivity reaction.

6. Validated to be sensitive against: Chemicals, Complex formulations,
 Cosmetics, Biologicals, Cellular Therapies and many more.
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Our unique assay readout - Tissue damage assesment

Figure 2 - A representitive demonstration of the grading process used in the Skimune assay
Histopathological damage assesment is a unique and key part of our unique Skimune assay readout which provides highly sensitive, characterisable immunotoxicity data which is clinically predictive of human reponse. Our grading system is based both on the severity of the reaction and the proportion of positive donors. Together this allows us a high level of sensitivity meaning we can pick up small but significant differences in immunological profile between tested conditions.

Tissue damage assessment improves predictability over cell-based assays by providing a more physiologically relevant and complex environment to study the effects of drugs, toxins, or other compounds on biological systems. While cell-based assays offer valuable insights into cellular responses, they have limitations in accurately representing the complexity of the whole tissue or system.

Cellular Interaction: In tissues, different cell types interact with each other and communicate through complex signalling pathways. Assessing tissue responses allows researchers to study how various cell types influence each other's behaviour, which cannot be fully replicated in isolated cell cultures.

Microenvironment: Tissues have specific microenvironments, including extracellular matrices and tissue-specific architecture, which significantly impact cellular behaviour. This context is absent in traditional cell-based assays.

Metabolism and Absorption: Tissues can metabolize and absorb compounds differently than individual cells. Assessing tissue damage allows researchers to understand how drugs or toxins are processed and distributed within a complex biological system.

Pharmacokinetics: The study of drug distribution, metabolism, and excretion (pharmacokinetics) is better understood when studying tissues since they reflect the body's overall response to a compound.

Translation to In Vivo Situations: Tissue damage assessment provides more realistic outcomes, making it easier to translate the results to in vivo situations, such as animal models or clinical trials.

While cell-based assays remain valuable for initial screening and mechanistic studies, assessing tissue damage offers a more comprehensive understanding of the effects of compounds on complex biological systems. This enhanced predictability is essential for improving drug development and toxicity testing, ultimately benefiting human health and safety.

Immunotoxicity assessment is a huge consideration when developing a new pharmaceuticals intended for use in humans. Are 2D cell based systems enough to truly model complex immunological reactions?

Figure 3 – Skimune® fits into the current OECD sensitisation guideline process covering multiple key events.​ Our assay is able to provide data for keratinocyte responses, dendritic cell activation, T cell proliferation and organ tissue reponses.

How do our assays compare with others available on the market?

Currently the gold standard techniques to determine skin sensitisation rely on a best 2 of 3 approach from the following OECD assays;

Key event 1 – Molecular initiating event. The Direct Peptide Reactivity Assay (DPRA) is an in chemico method, using synthetic peptides to determine protein reactivity.

Key event 2 – Keratinocyte inflammatory responses. The KeratinoSens assay uses a genetically modified immortalised cell lineage in a 2D system. Increased fluorescence from a Luciferase reporter gene allows for quantification of inflammatory upregulation

Key event 3 – Activation of Dendritic Cells (DC). The h-CLAT assay uses a human leukaemia cell line to mimic DC activation measured through changes in surface marker expression.

The Skimune assay covers multiple parts of the sensitisation pathway (Figure 4), providing valuable, comprehensive and predictive data in a single assay.
As a field do we need to move away from the use of genetically modified cancer cell 2D cultures for our sensitisation assessments?

Here at Alcyomics, we would argue yes. For a number of key reasons;
  • Cancer lineages contain variable genetic abnormalities which can be detrimental to cellular function.
  • Cell lines are homogenous and do not represent the heterogeneity of sensitisation responses present at a population level. Would you trust the safety of a drug if it had only been tested on a single donor?
  • 2D cell cultures have been shown to be less physiologically relevant at both the genetic and proteome level. Recent understandings have shown that a cells shape can have significant effects on its function and differentiative potential
What about animal studies?
Other animal based immunotoxicity assays such as the local lymph node assay (LLNA) have been used extensively in the past to determine immunotoxicity in human drugs. However, these assays have been demonstrated to suffer from several disadvantages such as false positive responses, variability due to the vehicle used, their overall predictivity (~72% against human data) and their inability to distinguish between type of hypersensitivity response.

Overview of the OECD approach

Figure 4 - Overview of the OECD test guideline approach for sensitisation.
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