Pathobiology of Dengue Virus Infection

Fadel Muhammad Garishah

Pathobiology of Infectious Diseases

Faculty of Medicine DIPONEGORO UNIVERSITY

2014

Clinical Vignette

A 5 years-old boy was referred from a public health centerto general hospital due to a rapidly decreasing of platelets.

The previous 3 days he experienced fever up to 38,9 C, hedidn’t have any URT/LRT infection or Urinary tractsymptoms, no neurological deficits.

Currently his body temperature is 36,7 C, with coldextremities.

Previous labwork showing a rapidly decreasing plateletscount from 102,000/mL and now 45,000/mL.

The GP in PHC referred the patient due to the prediction offalling into severe shock.

Original Case from Emergency Department General Hospital

Nature Reviews | Microbiology

Vascular symptoms:HypovolaemiaLow blood pressureShock

Hepatic injuryFluid pooling in body cavitiesGall bladder thickeningHaemorrhaging within organs

Infrequent complications:EncephalitisAcute pancreatitisRenal failureMyocarditisSplenic rupturePulmonary haemorrhage

Vascular symptoms:LeukopeniaThrombocytopeniaNeutropeniaLate eosinophiliaReduced coagulation

Skin symptoms:RashBruisingPetechiaePurpura

Joint pain

Altered haematopoiesis

Bleeding gums, nose and eyes

Headache, fever

VomitingIntestinal bleeding

pro-inflammatory response that is detectable

in the serum of patients with dengue32, it has

been postulated that immune factors act as

intermediaries in the response of endothe-

lial cells to DENV. In particular, cytokine

storm (elevated levels of many cytokines in

the serum) has been identified as a poten-

tial underlying mechanism of vascular

pathology21.

During DENV infection, copious amounts

of certain pro-inflammatory and vaso active

cytokines, including TNF and vascular

endothelial growth factor A (VEGFA), are

produced32. However, although these fac-

tors are frequently elevated in the serum

of patients with dengue, some studies have

raised questions about their direct role in

dengue pathology. For example, in spite of

the well-established role of TNF in promot-

ing vascular leakage in other diseases and

experimental contexts33,34, there has been no

clear correlation shown between levels of

TNF and the manifestation of dengue fever

versus DHF–DSS in humans. Some evidence

has been obtained for there being both lower

expression of TNF receptors on granulo-

cytes during DHF–DSS35 and an association

between DHF–DSS and certain TNF poly-

morphisms12. In one study, serum TNF

was elevated during both DHF–DSS and

dengue fever compared with levels in healthy

controls, but a significant difference in TNF

levels between DHF–DSS and dengue fever

groups was not detected36. Thus, it is possible

that TNF has a role in DENV infection, but

whether it is (or can be, in some instances)

a significant cause of DHF–DSS in humans

is still unclear. Multiple pro-inflammatory

factors might act in concert to promote

vasculopathy.

Drawbacks of in vitro analysis. Ultimately,

the mechanisms of many of the immune

changes that occur in response to DENV

infection, and the roles of these immune

changes in protection versus pathology, are

not yet explained. Unfortunately, the com-

plexity of the interactions between DENV

and the host cannot be adequately modelled

by in vitro manipulation of human cells and

biological products outside the organs and

systems that govern their responses to infec-

tion. Not only are the specific target cells of

DENV not clearly known, but also in vitro

analysis does not capture the responses

of cells that do not become infected but

might nonetheless respond to DENV and

to the inflammatory products in their

microenviron ment in vivo. As a further

complication, interactions between DENV

and host cells can change over the course of

infection, which begins as a localized cuta-

neous infection with innate immune activa-

tion and develops into a systemic infection

characterized by viral replication in target

organs (including the lymphoid system) and

high viral titres in the blood19. The most

severe pathologies associated with DENV

infection frequently manifest in patients

as viraemia resolves and fever begins to

subside27, but it is unclear at what stage of

infection these pathological processes are

initiated.

The role of immunological memory

Primary DENV infection results in long-

lasting immunity to the infecting serotype

and, potentially, partial immunity to subse-

quent infection with other serotypes. Many

individuals in dengue-endemic countries

have experienced DENV infection previ-

ously. Re-infection with the same serotype

as that which caused the primary infection

has not been documented, demonstrating

that immunity to a homologous DENV

strain can be highly protective and lifelong5.

Pre-existing neutralizing antibodies must

have a major role in preventing subsequent

infection with the same DENV serotype.

Secondary infection with a heterologous

serotype can cause a broad spectrum of

illnesses, ranging from asymptomatic infec-

tion to severe haemorrhagic disease. For

example, some epidemiological studies have

shown that patients with a secondary DENV

infection and babies born to mothers who

have previously been infected with DENV

are more likely to develop severe disease37,38.

One theory for why this occurs was first

described in reference to other flaviviruses

(Murray Valley encephalitis virus, West Nile

virus and Japanese encephalitis viruses)39

and is termed antibody-dependent enhance-

ment of infection (ADE). ADE involves

the binding of immune complexes of non-

neutralizing antibody and infectious virus

to the Fc receptors of immune cells29,40,41

Figure 1 | Dengue virus pathogenesis in humans. Systemic infection with dengue virus (DENV)

affects multiple organ systems. This diagram depicts the clinical symptoms and pathogenesis of

dengue in humans, across the spectrum of mild to severe disease. Clinical manifestations associated

with dengue fever are listed in blue boxes, those associated with dengue haemorrhagic fever are listed

in purple boxes, and more rare complications of DENV infection are listed in the green box.

PERSPECTIVES

NATURE REVIEWS | MICROBIOLOGY ADVANCE ONLI NE PUBLI CATI ON | 3

© 2013 Macmillan Publishers Limited. All rights reserved

Clinical Manifestations ofDENV Infection

John ALS, Abraham SN, Gubler DJ.Barriers to preclinical investigations of anti-dengue immunity and dengue pathogenesisNature Reviews Microbiology 11, 420–426 (2013)

Available from: http://www.nature.com/nrmicro/journal/v11/n6/full/nrmicro3030.html

Geographical Distribution of Dengue Virus Infection

Distributed in the tropics and subtropics, data shown as dengue infection (DF, and DHF) cases

Whitehead SS, Blaney JE, Durbin AP, Murphy BR. Prospects for a dengue virus vaccine. Nature Reviews Microbiology 5, 518-528 (1 July 2007)

Available from: http://www.nature.com/nrmicro/journal/v5/n7/full/nrmicro1690.html

How dengue is transmitted?

Because of the high level of viraemia resulting from dengue virus (DENV) infection of humans, the viruses are efficiently transmitted between mosquitoes and humans without the need for an enzootic amplification host.

Whitehead SS, Blaney JE, Durbin AP, Murphy BR. Prospects for a dengue virus vaccine. Nature Reviews Microbiology 5, 518-528 (1 July 2007)

Available from: http://www.nature.com/nrmicro/journal/v5/n7/full/nrmicro1690.html

Key of pathophysiology

What causes the vascular leakage?• Direct platelet/endothelial damage?• Immune mediated platelet/endothelial damage?

Picture taken from Kumar V et al. Robbin’s Pathologic Basis of Disease 8th Edition. 2011. Philadelphia: Elsevier Saunders

What causes what?

How DENV enter patient’s body?

Diamond, M. S. Evasion of innate and adaptive immunity by flaviviruses. Immunology and Cell Biology 81, 196–206 (2003).

What is the role of secondary infection of DENV?

• In the 1960s, Dr. Scott Halstead and his colleagues were studying the dengue virus in Thailand.

• They noticed that people who had been exposed to dengue a second time had an increased risk of severe dengue compared with those who had not been previously exposed.

• They wondered what makes a second dengue infection worse than the first.

Host Response to Dengue Infectionhttp://www.nature.com/scitable/topicpage/host-response-to-the-dengue-virus-22402106

The dengue virus tricks the immune system to get around its defenses and

infect more cells.

Non-neutralizing antibodies bind to FcGR of monocytes, inducing a large amount of viral ingestion in MO. Causing higher intraMacrophage multiplication, increasing viral loadand cytokines production, affecting the immune mediated storms.

Whitehead SS, Blaney JE, Durbin AP, Murphy BR. Prospects for a dengue virus vaccine. Nature Reviews Microbiology 5, 518-528 (1 July 2007)Available from: http://www.nature.com/nrmicro/journal/v5/n7/full/nrmicro1690.html

Mole BM. Bedeviled by Dengue/ The Scientist March 2013. http://www.the-scientist.com/?articles.view/articleNo/34434/title/Bedeviled-by-Dengue/

Vascular Leakage

A large infected cell mass results in elevated concentrations of acute-phase response proteins, cytokines, and chemokines; generation of immune complexes; and consumption of complement and release of split products.

Interactions between dengue nonstructural protein 1 (NS1) and the surface glycocalyx layer may result in release of heparan sulfate into the circulation, thereby altering the filtration characteristics of the layer and resulting in leakage of proteins.

Simmons CP, Farrar JJ, van Vinh Chau N, Wills B. Current Concepts: Dengue. N Engl J Med

2012;366:1423-32

Conclusion

“B cells produce antibodies that specifically recognize and neutralize the foreign viral particles, and cytotoxic T cells recognize and kill cells that are infected with the dengue virus.

People who are infected a subsequent time with a different type of the dengue virus may experience something called "antibody-dependent enhancement."

Host Response to Dengue Infectionhttp://www.nature.com/scitable/topicpage/host-response-to-the-dengue-virus-22402106