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Pneumocystis jirovecii and Toxoplasma gondii:

A Tale of Two Parasites orOpportunistic Infections In Immuno-deficient Hosts

Charles Knirsch, MD, MPH

Protozoan Parasites1. Toxoplasma gondii

2. The MalariasPlasmodium falciparumPlasmodium vivaxPlasmodium ovalePlasmodium ovalePlasmodium malariae

3. Diarrheal disease-causing protozoa:Giardia lambliaEntameba histolyticaCryptosporidium parvumCyclospora cayetanensis

Toxoplasma gondii

and

Protozoa:

Pneumocystis jirovecii*formerly P. carinii

*actually an unusual fungus

Western & Central Europe

730 000730 000[580 000 [580 000 –– 1.0 million]1.0 million]

Middle East & North Africa

380 000380 000

Eastern Europe & Central Asia

1.5 million 1.5 million [1.1 [1.1 –– 1.9 million]1.9 million]

South & South East

North America1.2 million

[760 000 – 2.0 million]East Asia740 000740 000

[480 000 [480 000 –– 1.1 million]1.1 million]Caribbean230 000

Adults and children estimated to be living with HIV, 2007

Total: 33 million (30 – 36 million)

380 000380 000[280 000 [280 000 –– 510 000]510 000]Sub-Saharan Africa

22.0 million22.0 million[20.5 [20.5 –– 23.6 million]23.6 million]

South & South-East Asia

4.2 million4.2 million[3.5 [3.5 –– 5.3 million]5.3 million]Oceania

74 00074 000[66 000 [66 000 –– 93 000]93 000]

Latin America1.7 million1.7 million

[1.5 [1.5 –– 2.1 million]2.1 million]

230 000[210 000 – 270 000]

And the Band Played On• Politics, people and the AIDS epidemic• CDC April 1981: “This guy should go back

to medical school if he can’t find some simple neoplasm”

• June 1981 MMWR: Pneumocystis pneumonia in young men

• GRID

2

Opportunistic Infections Associated with Progressive

Immunodeficiency

cyte

s m

eter

500500450450400400350350

TBTBThrush & vaginal candidiasisThrush & vaginal candidiasis

CD

4+ T

-Lym

pho

per C

ubic

Mill

im 300300250250200200150150100100

505000

66 1212 1515Time After HIV Infection (Years)

PCP, Chronic or recurrent herpes infections

PCP, Chronic or recurrent herpes infections

Systemic fungal infections, CMV, Toxoplasmosis

Systemic fungal infections, CMV, Toxoplasmosis

MACMAC

1010

Pneumocystis jirovecii (PCP)

• Commensal organism and opportunistic pathogen

• Morphologically resembles protozoanMorphologically resembles protozoan• Difficult to grow in vitro• Life cycle???

– Cyst stage : 5 um in diameter with 4-8 sporozoites

– Trophozoite : 2-5 um in diameter – attach to cell surfaces

PABA (Para-aminobenzoic Acid)

Pteridine +

Sulfonamides /Dapsone

Folic acid

Dihydropteroate Synthetase

Folic Acid Inhibitors are Drugs of Choice for PCP

Pyrimethamine, Proguanil

Dihydrofolate reductase

Dihydrofolic acid

Tetrahydrofolic acid

3

Is P. carinii a Fungus or Protozoon?

Protozoon• Morphology• Inability to culture in vitro

R t ti t l d• Response to anti-protozoal drugsFungus• Ribosomal rRNA sequence homology• ELF3

AnimalsAnimals

PlantsPlants

ProtozoaProtozoaFungiFungiSlime moldsSlime molds

Algae (red, brown, green, others)Algae (red, brown, green, others)

Cyanophytes (blue-green algae)Cyanophytes (blue-green algae)

Higher protistsHigher protists

Lower protistsLower protists

Early protozoaEarly protozoa

??

??

BacteriaBacteria

Ancestral procaryotic group

Ancestral procaryotic group

Precellular forms Precellular forms

VirusesViruses

????

??

Toxoplasma gondii

Protozoa:

Toxoplasma gondii

Toxoplasma gondiiThe Plasmodia (malaria)Cryptosporidium hominis

The Apicomplexa

Toxoplasma gondii infects all mammalsand all tissues in each of them.

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Felines are the definitive hosts for Felines are the definitive hosts for Toxoplasma gondiiToxoplasma gondii

Oocysts of Toxoplasma gondii

Unsporulated

Sporulated

Rack of lamb is usually served rare

Macrophage Infected With Toxoplasma gondii*

* The hunter becomes the hunted

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Toxoplasma gondii in culture

Trophozoites (T) prevent fusionof lysosomal menebranes to thparasitophorous vacuole thereparasitophorous vacuole, thereescaping digestion

Toxoplasma gondii in culture

Heat-killed organisms cannotprevent fusion of lysosomal membranes with themembranes with the parasitophorous vacuole

Congenital

Adult acquired

Clinical Disease:

Adult-acquired

AIDS-related

Congenital Toxoplasmosis

Calcified Lesions Due To Congenital Toxoplasmosis

Congenital Toxoplasmosis

Photo courtsey: Gary Baumbach, M.D., Department of Pathology, University of Iowa College of Medicine

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Congenital Toxoplasmosis:

Still Birth

Chorioretinitis

Mental Retardation

Congenital Toxoplasmosis Following Maternal Infection During First and Second Trimester*

Not Infected 73%Subclinical Infection 13%Subclinical Infection 13%Mild Infection 7%Severe Infection 6%

* From Desmonts and Couvier, NEJM 290: 1110, 1974

Toxoplasma Ocular Disease

• Usually from congenital infection manifesting in adults– Episodic flares may destroy retinal tissueEpisodic flares may destroy retinal tissue– Specific treatment necessary

Adult-Acquired Toxoplasmosis

Infection by Blood or Organ Transplant

• Parasitemia (WBC’s) for up to 1 year post infection

• Heart bone marrow liver kidneyHeart, bone marrow, liver, kidney donors– Dangerous when recipient toxo (-)

• Myocarditis, diffuse lymphadenopathy

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Adult-Acquired Toxoplasmosis

Lymphadenopathy

F

Signs and symptoms:

Fever

Headache

Chronic Malaise

Differential Diagnosisof LymphadenopathyDifferential Diagnosisof Lymphadenopathy

ToxoplasmosisToxoplasmosis

+++

+

+++

+++

+

+++

Inf. MonoInf. Mono

+

+++

+

+

+++

+

LymphomaLymphoma

+++

+

+++

+++

+

+++

Lymphadenopathy WithoutOther Symptoms

Pharyngitis

Monocytosis, Eosinophilia

Lymphadenopathy WithoutOther Symptoms

Pharyngitis

Monocytosis, Eosinophilia

+

0

0

0

+

ReticulumCells

+

0

0

0

+

ReticulumCells

++++

+

++++

++++

+

Germinal Cells

++++

+

++++

++++

+

Germinal Cells

+

+++

0

++

+++

Bizarre Cells

+

+++

0

++

+++

Bizarre Cells

y , p

Atypical Lymphocytes

Anemia

Positive Heterophil

Altered Liver Function

Hilar Lymphadenopathy

Lymph Node Pathology

y p

Atypical Lymphocytes

Anemia

Positive Heterophil

Altered Liver Function

Hilar Lymphadenopathy

Lymph Node Pathology

Pseudocyst of Toxoplasma gondii in Liver

Pseudocyst

AIDS-related Disease

Pseudocysts of Toxoplasma gondii in a microglial nodule with a variety of inflammatory cell types

in an HIV/AIDS patient

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AIDS-related Disease:1. CD4 < 200 and reactivation of latent infection

2. Encephalitis1. Diffuse inflammation and swelling2. Localized ring enhancing lesions on CT scan3. Herniation4. Death if untreated

Toxoplasma abscess in the brain would appearas a ring-enhancing lesion with CT scan.

CT Scan

Diagnosis

Serological correlatesin acute and chronic infection

Indirect Fluorescent Antibody (IFA)Test

PABA (Para-aminobenzoic Acid)

Pteridine +

Sulfonamides /Dapsone

Folic acid

Dihydropteroate Synthetase

Folic Acid Inhibitors are Drugs of Choice

Pyrimethamine, Proguanil

Dihydrofolate reductase

Dihydrofolic acid

Tetrahydrofolic acid

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Prevention:

1. Prevent pregnant women from handling cat litter

2. Avoid eating raw or under-cooked meats

Automated litter collection boxTrained cat

Host status

• Pneumocystis carinii– No Life cycle!

• Toxoplasma gondii– Cat definitive hosty

– Lung disease in AIDS

– Malnourished children

– Organ Transplants

– Disease: Host status– CNS Disease in

AIDS– Congenital Infections– Organ Transplants

Disease Number of Cases Population at-risk

Ascariasis 807 million 4.2 billion

Trichuriasis 604 milion 3.2 billion

Hookworm 576 million 3.2 billion

Amebiasis 500 million ND

The Most Common Neglected Infections of Poor People

Schistosomiasis 200 million 0.6 billion

Lymphatic Filariasis 120 million 1.0 billionTrachoma 84 million 0.5 billion

Onchocerciasis 18 million 0.1 billionChagas Disease 16 million 0.1 billionLeishmaniasis 12 million 0.4 billionLeprosy 0.4 million ND

Dracunculiasis 0.01 million ND

Global Network for Neglected Tropical Diseaseshttp://www.GNNTDC.org

• Schistosomiasis Control Initiative • International Trachoma Initiative• Helen Keller International• Liverpool School - GAELF• Liverpool School - GAELF• Human Hookworm Vaccine Initiative• Earth Institute at Columbia Univ.• Task Force for Child Survival

– Mectizan Donation Program– Albendazole Donation Program– Mebendazole Donation Program