Consideration of additional factors

Up until this point, the discrepancy of tolerance and immunogenicity of interferon-βin patients a�ected with multiple sclerosis has not yet been fully understood. Although recent studies suggest an association between HLA genes and the production of antibodies, the immune process pathway still remains fairly unexplored. Previous studies revealed that a correlation between the HLA alleles HLA-DRB1*0401, HLA-DRB1*0408 and HLA-DRB1*1601 and the production of antibodies to interferon-βis assumedHo�mann et al.(2008);Buck et al.(2011).

Also, the alleleHLA-DRB1*0701 especially when linked toHLA-DQA1*0201 showed an in�u-ence on the formation of antibodiesBarbosa et al.(2006). Furthermore, a recent study also investigated a speci�c genetic predisposition for the development of neutralizing antibodies dependent of the interferon-β-preparation givenLink et al.(2014). The results showed that the alleleHLA-DRB1*15 causes an enhanced risk to develope neutralizing antibodies against Interferon-β_1aapplied both subcutaneously and intramuscularly. Moreover, the well-known al-leleHLA-DRB1*04 revealed a high risk of antibody production especially against Interferon-β_1b preparations. In this study, only patients developing neutralizing antibodies, apart from those developing binding antibodies, were included. The�ndings of this study may be explained by a di�erence in binding a�nity of HLA molecules to Interferon-β_1a and Interferon-β_1b. Summariz-ing this study indicates a genetic predisposition to immunogenicity dependSummariz-ing on interferon-β preparation given, certainly further studies are needed.

Despite these imposing research�ndings, a recent study found that no direct association between theHLA-DRB1,HLA-DQA1or HLA-DQB genes and a response to interferon-βtherapy could be proven. This means that the previous assumptions cannot yet be veri�edComabella et al.(2009). More and more research projects are initiated to delve deeply into exploring the immunogenicity of protein therapeutics, such as interferon-β.

Beside genetic in�uence within the immune response to interferon-βtherapy, possible addi-tional factors need to be carefully considered. Immunostimulatory agents such as lipopolysac-charide (LPS),lipopeptidesor other substances added during interferon-βpreparation, speci�-cally appear to in�uence the immune system and result in stimulating antibody production in defense to given medication, as suggested by a recent studyEnevold et al.(2010). This impression can be enhanced when considering the fact that the TLR6 gene, which carries the associated SNP to antibody production rs5743810 on chromosome 4, is known to have a elemen-tary part in pathogen recognition processesEnevold et al.(2010). This means that a residual amount of bacterial lipoprotein or other bacterial traces may appear within a protein drug and possibly trigger immunogenicity. In other words, residual substances within interferon-β preparation may lead to a boost of the immune system and induce the formation of neutralizing antibodies. Most of all, treatment withBetaferonseems to provoke the development of anti-bodies.Betaferonis a Interferon-β_1b obtained fromE. colibacteria or produced synthetically.

Note the accordance of the thoroughly large percentage of patients within our data developing antibodies when treated withBetaferon(48,5 % of patients within theTUM 1 datasetand 40,9 %

13.2. Consideration of additional factors 111 of patients within theTUM 2 dataset) in agreement with previous studies. This may indicate a higher risk in producing antibodies when the protein drug is no human product. Moreover, we have to bear in mind that residual agents in protein drugs can also lead to dangerous side e�ects, cause allergic reactions or even an anaphylactic shock when not tolerated. Thus, there is a great focus on improving the puri�cation process within drug manufacturing to provide safer protein drugs in the future.

What is also remarkable is the extremly low amount of patients that developed antibodies after being treated withAvonex in theTUM 2 dataset(only 9,6 %).Avonexis a Interferon-β_1aobtained from mammalian cells and therefore consists of the identical amino acid sequences to human interferon-β.Betaferondi�ers in the initial methionine as well as two other exchanged amino acid sequences, which can be di�erence enough to display a potential immunomodulatory factor in inducing the formation of neutralizing antibodies.Avonex is the only interferon-βapplied intramuscularly once a week.Betaferon,Rebif 44as well asRebif 22 are applied subcutaneously.

This low incident of antibody production within the group of patients treated withAvonex may also indicate a di�erent absorbance of medication and reveal a protective e�ect on antibody production. Furthermore, the less frequent application may play a participating role in better tolerance of the medication.

As mentioned above, Betaferon is applied subcutaneously and represents the group of interferon-β preparation with the highest percentage of antibody production at the same time. A recent study revealed this statistic may be additionally explained due to the fact that the skin tissue contains a high amount of dendritic cells, which are responsible for detecting external agents. The dendritic cells might be activated through frequently injected interferon-β and initiate a immune responseLink et al.(2014).

The discrepancy of antibody production within various interferon-βpreparations and ap-plication methods was also denoted in further studiesBarbosa et al.(2006);Buck et al.(2011);

Ho�mann et al.(2008);Link et al.(2014). Note that not all of these�ndings accord to those detected within the TUM 1 dataset, which veri�es once more as mentioned above that this dataset needs to be reviewed carefully before further utilization (for details see chapter6).

Summarizing various factors such as drug manufacturing, dose application and frequency of admission as well as length of treatment need to be kept in mind since they in�uence the balance between protein drug tolerance and immunogenicity. Even the possibility of a missing antibody response due to a compromised immune system needs to be considered.

The progress in developing less immunogenic drugs is essential, as is exploring the impact of genetic biomarkers. The prediction model created within the scope of this thesis can be a supplementary screening strategy in clinical practice to forecast therapy outcome.