Virus-infected monocytes can initiate coagulation and promote inflammation. An in vitro study found that monocytes infected with cytomegalovirus, influenza A virus, or Chlamydia pneumoniae expressed tissue factor and reduced clotting time, indicating initiation of coagulation. The viruses also stimulated monocytes to produce inflammatory cytokines like IL-6 and IL-8. While all three viruses infected monocytes, influenza A most strongly induced cytokine production. This suggests virus-infected monocytes may contribute to both acute coronary events by promoting plaque instability and the chronic atherosclerosis process through sustained inflammation and coagulation.

1. Procoagulant And Inflammatory Response of
Virus-Infected Monocyes
Provided by:
Enrique Gurfinkel , MD, PhD
Fundación Favaloro, Capital Federal, Buenos Aires, Argentina
Editorial Slides
VP Watch – November 13, 2002 - Volume 2, Issue 45

2. Introduction
• Atherosclerosis is thought to be an inflammatory
disease, but its origin still remains unanswered.
• Chronic low-grade inflammation and combination
of classical risk factors, plus novel risk factors
such as the infectious burden seem to contribute
to promote atherosclerosis.

3. Introduction
• Monocytes play a prominent role in
inflammation, coagulation and the ability to
produce tissue factor and cytokines.
• All of these factors, particularly the production of
cytokines may contribute to acute coronary
syndromes by eliciting plaque instability.

4. Background
• During viral infections monocytes predominantly
produce inflammatory cytokines.
• In addition, continuing viral infection may sustain
excess tissue factor production and exhaust the
inhibitory effects of tissue factor pathway
inhibitor.

5. As highlighted in VP Watch of this week,
• Bouwman and co-workers tried to establish
whether virus-infected monocytes initiate
coagulation.
And
• To detect if the production of cytokines by
monocytes may contribute to the chronic
process of atherosclerosis in an in-vitro model.

6. Methods
• Isolation of monocytes:
monocytes obtained from fresh
blood of healthy volunteers.

7. Methods
• Preparation of virus stocks: Human embryonic
lung, human epidermoid larynx carcinoma, and
LLC-MK2 cells were cultured in Eagles´s
minimum essential medium with Earle´s salts.
• A clinical isolete of CMV was propagated in HEL
cells
• Chlamydia pneumoniae strain AR 39 was
propagated in HEP-2 cells
• Influenza A HIN1 86 Singapore was propagated
in LLC-MK2 cells

8. Methods
• Coagulation assay: Normal pooled plasma
was prepared from the blood of nine
healthy donors.
• Cytokine assays: IL 6, 8, and 10 were
measured in the supernatants of virus-
infected monocytes.

9. It appeared that all strains could infect monocytes, but in all cases the infection
was below 5% when undiluted virus stocks were used.
 Fluorescence microscopy images of virus-
infected monocytes. Magnification 200x after
overnight incubation; Red background: uninfected
monocytes. Green areas: virus-infected monocytes
stained with FITC-labeled anti-virus antibodies.
(a) CMV, specific staining of CMV in the nuclei
of the infected cells. (b) Influenza A, smooth
staining pattern of influenza A in monocytes. (c)
Cp, more dense staining pattern of Cp in the
cytoplasm of monocytes.

10. 80% of the monocytes were covered with
activated CD41+ CD42+
Ficoll + VPT+ VPT+
Depletion Depletion Positive Selection
CD41+ CD42+ 46% 78% 3%

11. CMV and Cp, like influenza, reduced the clotting time.
The inititation of coagulation by virus-infected monocyes
was a result of the expression of TF.
Clottingtime(seconds)
Uninfected monocytes Infected monocytes
140+-22.1 s
333+-22.1s

12. Infection with CMV and Cp induced the production of
modest levels of IL6 and IL8, whereas infection with influenza A
strongly stimulated the production of IL6 and 8.
IL-6IL-8(pgml)
CMV & Cp
IL 6
1000
IL-8
H1N1
2000

13. Discussion
• The results of the present study
indicate that only small quantities of an
infectious virus are needed to stimulate
monocytes to exert considerable
immunological effects.

14. Conclussions
• The procoagulant activity of virus-
infected monocytes is TF-dependent.
• Influenza infection induced a
pronounced expression of IL-6 and IL-
8, which could be associated with
plaque rupture.

15. Questions
• Is there any differences between the
bacterial and viral infectious burden in
promoting procoagulant activity?
• Is it plausible to think that this could
explain a systemic pro-thrombotic
process after infection?

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3. Mosorin et al. Detection of Chlamydia pneumoniae-Reactive T lymphocytes in human
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4. Blankenberg S, Rupprecht HJ, Bickel C, Espinola-Klein C, Rippin G et al.
Cytomegalovirus infection with interleukine 6 response predicts cardiac mortality
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6. Frostegard J, Ulfgren A, Nyberg P, Hedin U, Swedenborg J et al. Cytokine expression in advanced
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7. Neumann FJ, Ott I, Marx N, Luther T, Kenngott S et al.
Effect of human recombinant Interleukin-6 and Interleukin-8 on Monocyte Procoagulant activity.
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8. Bouwman J. J. M. et al,. Eur J Clin Invest 2002; 32 (10): 759-766
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