1. Results & Discussion
- Disturbance detected in RANKL/OPG
ratio in RRV infected OBs
(Fig. 1):
• Increase in RANKL and a decrease
in OPG.
• Elevated ratio makes it in favor of
bone loss.
- RRV was concentrated in OBs based
on the murine model.
• Remained in OBs for 21 days after
infection as compared to 2 days in
other parts of the bone.
Literature Cited
Methods
I. ELISA & qualitative RT-PCR analysis
- Used to evaluate RANKL/OPG levels in mock- and RRV-infected hOBs
- ELISA is used to determine if a particular protein is present in a sample
- RT-PCR analysis is used to detect RNA expression
II. Microcomputed tomography (µCT)
- Similar to a CT scan
- Uses x-rays to create cross-sections to make a virtual model
- Imaging to show bone loss and impact of bone architecture caused by RRV
- Investigate the role of IL-6 in RRV-induced bone loss, and mice treated with
IL-6 neutralizing antibody.
Fig. 2 A & B: µCT imaging of the change in bone density
on the 15th day of RRV infection. Arrows were placed by me
for simplicity to notice the comparisons.
Fig. 3A: µCT imaging of RRV reducing the
width of growth plate width and cortical bone
thickness. Values and arrows were created by me
to show the obvious decrease in size.
: non-infected OBs
Introduction
The Ross River virus (RRV) is one of the many arthritogenic
alphaviruses that causes musculoskeletal conditions such as arthritis. The Ross
River virus disease (RRVD) causes inflammation, pain, and muscle aches on
the ankles, knees and peripheral joints.
This research focused on how RRV affected human and mouse
osteoblasts (OBs). The researchers focused on OBs because they play an
important role in bone metabolism. The bone is constantly reshaped known as
the remodeling process in which the OBs deposit new bone tissue whereas
osteoclasts (OCs) perform the opposite role and resorb bone tissue. OBs and
OCs constantly reshape the bone. Therefore, it is important to analysis if RRV
is concentrated in OBs and if so, what role it has.
The RANKL/OPG ratio makes sure that the process of creating and
destroying bone tissue is balanced. RANKL is a protein that activates OCs
while OPG is a decoy receptor to prevent and control RANKL from occurring.
This ratio is interfered by RRV which is an example of how RRV is
manipulating the immune system to perform detrimental actions towards the
body that it is suppose to protect.
By understanding what proteins are responsible for the decrease in
bone density, an antibody can be determined to prevent bone loss.
Fig. 4A & 4B: µCT analysis of the change in bone density
between untreated RRV-infected bone and treated RRV-
infected bone with antibody (Arrow is added for simplicity).
This shows clear evidence that IL-6 inhibition was
successful 10 day p.i..
*PBS (phosphate buffer saline) represents mock.
Summary
The goal of this research was to determine if arthritogenic alphaviruses
such as the Ross River virus (RRV) causes bone loss. The Ross River virus
disease (RRVD) is currently an outbreak in Australia. It is poorly defined on
how alphaviruses like RRV induce bone pathologies.
It was found in RRV-infected cultured human osteoblasts (hOBs) that
there was an increase in production of IL-6, a protein that induces bone loss.
Using a murine model, they discovered that the virus was concentrated in
osteoblasts (OBs) which are cells that deposit new bone tissue. There was also a
disruption of the ratio that balanced the creation and breaking down of bones.
The evidence found supports the claim that arthritogenic alphaviruses
such as RRV do cause bone loss and an antibody that inhibits the IL-6 protein
can help prevent bone loss.
- Bone volume in tibial epiphysis and vertebrae was reduced by 10% (Fig. 2A &
2B)
• Width of growth plate and cortical bone were reduced (impairment in
growth) (Fig. 3A)
- RRV stimulated the production of proinflammatory factor, IL-6, in hOBs.
- IL-6 inhibition in RRV-infected
4A
2B
Fig. 1: ELISA & qualitative RT-PCR (qRT-PCR)
analysis to show RANKL/OPG ratio elevated
: infected OBs
Virus Triggers Immune System to Cause Bone Loss
Amy Lin, Northeastern University, Boston MA
2A
- Infection caused by alphaviruses
triggers bone loss
• Preserved bone/tissue volume
• RANKL/OPG ratio was
significantly
- IL-6 causes bone loss and pain
m i c e w a s s u c c e s s f u l i n
ameliorating bone loss
(Fig. 4A & 4B)
- Antibody that neutralizes IL-6 only works in the beginning stages of RRVD and not
at the peak of RRVD. Using anti-IL-6R antibodies will likely be therapeutically
beneficial in preventing RRV induced bone loss.
4B
1.5mm 1.0mm 0.75mm
0.25mm 0.14mm 0.11mm
Chen W, Foo S, Rulli N, Taylor A, Sheng K, Herrero L, Herring B, Lidbury B, Li R, Walsh N, Sims N, Smith P,
Mahalingam S. (2014) Arthritogenic alphaviral infection perturbs osteoblast function and triggers pathologic bone loss
D.O.I. 10.1073/pnas.1318859111
3A
reduced compared
with infected control mice (the ratio did not differ from mock controls)