The role of genetic variations in type I Interferons related to respiratory tract infections in Down Syndrome children.

Children with Down Syndrome (DS) have a higher susceptibility to recurrent and
more severe upper and lower (or secondary) respiratory tract infections in
comparison to children without DS, resulting in an increased frequency of
hospitalization. Earlier research within our group shows preliminary evidence
that DS children have a dysregulated IFN response following ex vivo stimulation
with Influenza A virus. In this pilot project, we aim to study in more detail
the mechanism of IFN dysregulation and to identify dysfunctional components of
the Interferon signaling pathway in order to create a risk profile for disease,
namely the higher susceptibility to respiratory tract infections in DS
children. Identification of DS children who are at an increased risk for
(severe) respiratory tract infections allows preventive measures to be taken.
In the future, specific therapies may be developed which target the
dysfunctional components of the immune response in these children.

The main objective is to identify a difference in mRNA expression level of IFN
and IFN related genes between Down Syndrome children and a control group of
healthy children (siblings).
The secondary objective is to identify a relationship between mRNA expression
levels and history (current/past) of respiratory tract infections.

Observational study

Total duration: 6 months-1 year

Setting: outpatient clinic and laboratory

Study procedures:
A. Patient-related: single visit to the outpatient clinic:
1. Interview with participants or parents of participants regarding
history of respiratory tract infections (see attachment).
2. Blood collection from each participant: Total volume: 7,5 ml (2,5 ml
collected in PaxGene tube for baseline mRNA expression measurements, 4 ml
heparinized blood for full blood stimulation experiments, 1 ml of blood for
analysis of C-Reactive protein level, complete blood count, and leukocyte
differentiation).


B. Laboratory-related:
Laboratory of Clinical Chemistry VUmc: laboratory analysis of infection
parameters (C-Reactive protein level, complete blood count, and leukocyte
differentiation).

CCA/V-ICI laboratory VUmc:
In the blood samples, we will measure gene expression of several genes of
interest, measured by mRNA expression levels using Real Time PCR. Gene
expression will be measured at baseline and following in vitro stimulation of
whole blood with five different ligands (see protocol).

Ligands:
Interferon alpha, single stranded RNA (ssRNA), Lipopolysaccharide (LPS), CpG
DNA and Poly I:C.


Genes of interest:
1. IFN type I and II genes: IFN alpha, -beta and *gamma
2. IFN response genes: MxA, RSAD2, ISG15, IRF5
3. IFN alpha and gamma receptor subunits: IFNAR1, IFNAR2, IFNGR1, IFNGR2
4. TLR genes: TLR 3, 4, 7, 9

The burden involves a single visit to the outpatient clinic, an interview
regarding the history of respiratory tract infections, and venapuncture. The
venapuncture can cause pain, discomfort, or a hematoma at the site of the
venapuncture.
The risks are similar to the risks of a venapuncture performed for other
reasons.

We specifically want to include a group of Down syndrome children because this
group has an even higher susceptibility to respiratory tract infections
compared to children without Down syndrome. Preliminary results point to a
dysregulation in the Interferon system, and we therefore want to explore
whether a dysregulated Interferon system is correlated to a higher
susceptibility to respiratory tract infections. The information and results
obtained from this study may contribute to predicting which Down Syndrome
children have a higher risk of severe respiratory tract infections and to the
development of specific measures and/or therapies for this high risk group.

We want to include the siblings of these Down syndrome children because they
share a common genetic background and a similar environmental exposure to
pathogens, except that they do not have a chromosomal abnormality. This allows
us to compare two groups with shared common variables and differing only in the
number of copies of chromosome 21.

Participants will not have a direct benefit from this study. We believe that
the possible benefits from information obtained from this study regarding the
immune response in Down syndrome children outweigh the inconvenience of
participation.