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Flashcards in HIV Deck (61):
1

Classification of Retroviruses

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Simple retroviruses encode

gag, pol, and env genes

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Complex viruses also encode

accessory genes (HIV: tat, rev, nef, vif, vpu)

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slow viruses assoc. with neurologic and immunosuppressive disease

Lentiviruses

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Gag

group-specific antigen (core and capsid proteins)

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Pol

 polymerase (reverse transcriptase, protease and integrase)

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Env

envelope (glycoproteins)

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HIV characteristics 

RNA Viruses, ss, (+) sense, RT

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HIV pic 

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4 accessory genes HIV

(vif, vpr, vpu, nef)

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2 regulatory genes (virus-host interactions) HIV

tat 

rev 

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Binding and Fusion HIV characteristics 

begins by binding to a CD4 receptor and co-receptor on the surface of a CD4+ T-lymphocyte fuses with the host cell releases RNA into host cell

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Integration HIV 

Newly formed HIV DNA enters the host cell's nucleus

→ HIV integrase helps insert the HIV DNA within the host cell's own DNA

integrated HIV DNA: provirus

→ The provirus may remain inactive for several years, producing few / no new copies of HIV

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Transcription HIV 

Host cell receives a signal to become active provirus uses a host RNA polymerase to copy the HIV genomic material and mRNA

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Assembly HIV

HIV protease “cuts” the long chains of HIV proteins into smaller individual proteins (smaller HIV proteins assemble with copies of HIV genome  new virus particle)

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Budding HIV

Newly assembled virus buds from the host cell

- takes part of the cell's outer envelope (is studded with HIV glycoproteins)

- HIV glycoproteins: necessary for virus to bind CD4 and co-receptors, allowing them to move on to infect other cells

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Which HIV subtype is found in the US 

HIV-B 

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HIV replication cycle 

1. Fusion

2. Entry

3. Viral DNA via RT

4. Viral DNA: transport to nucleus, integration 5. New vRNA  genomic RNA, viral proteins

6. New vRNA + proteins move to cell surface  new, immature, HIV virus

7. Virus matures by protease releasing individual HIV proteins

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HIV – Transmission

• Infected individual’s blood, semen or vaginal fluid

– Unprotected anal, vaginal, oral sex w/ infected individuals

– Share needles / syringes w/ infected individuals

• Increased risk with other STI infections

• HIV does not survive for long periods of time outside host

20

characteristics of newly infected HIV pts 

 

 About 97% are in low and middle income countries

 About 1000 are in children under 15 years of age

 About 6000 are in adults aged 15 years and older, of whom:

─ almost 48% are among women

─ about 42% are among young people (15-24)

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HIV – Pathogenesis

virus tropism for CD4- expressing T cells and macrophage lineage cells

– multipotent hematopoietic stem and progenitor cells

 Dendritic cells

– Accumulate the virus particles on their surfaces, but do not usually internalize them

– carry virus to lymph nodes resulting in efficient infection of CD4+ T cells

22

Mechanisms of immune evasion HIV

– antigenic variation

– carbohydrate masking of target epitopes

– conformational changes

by viral envelope to mask neutralization targets

– downregulation of host HLA

– viral latency in resting T cells and antigen- presenting cells

23

HIV encephalopathy CPEs

Cells appear to be the result of syncytial fusion of HIV-infected macrophages and microglia

Virus spread  cell to cell; immune circulatory antibodies cannot have an effect

Syncytia often seen in the brain

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HIV - Diagnosis methods

Antibody or antigen testing (usually within a few weeks of infection), ELISA / Western Blot

25

After CDC reccomendations, how much of a reduction in AIDS was seen over years 

95% rate drop

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Mortality and highly active antiretroviral therapy (HAART) use 

Significant drops in HIV deaths 

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Percentage of people eligible who are receiving antiretroviral therapy highest in what nations 

Latin america 

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Course of HIV Progression

Typical/rapid/ nonprogression

• Typical progression – 80%, 7-10 yrs

• Rapid progression – 5-10%, within 2 yrs

• Non-progression

– 10-15%, no disease ~7-10+ yrs

– CD4 count stays high, viral load not detectable (no medications)

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Course of HIV Progression graph

• Window period

– Negative HIV test (primary infection to sero- conversion)

– Viral load very high,  high transmission risk

• Acute retroviral syndrome

– Symptoms can have a huge range – WIDE DIFFERENTIAL DIAGNOSIS

• Opportunistic infections

– GOAL is to prevent these from occurring – Greatly increase chance of death

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Acquired Immunodeficiency Syndrome (AIDS)

• final stage of HIV infection

– virus has weakened the immune system to the point at which the body has a difficult time fighting infection

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Progression of AIDS

1) acute infection

2) strong anti-HIV immune defense

3) a latent reservoir

4) loss of CD4+ cells and loss of immune response

5) onset of AIDS

32

Bacterial pneumonia in AIDS cause

Common cause is Streptococcus pneumoniae

33

Streptococcus pneumoniae, Virulence

colonize oropharynx (surface protein adhesions),

spread into normally sterile tissues

(pneumolysin, IgA protease), stimulate

local inflammatory response (teichoic acid, peptidoglycan fragments, pneumolysin), and evade phagocytic killing (polysaccharide capsule)

34

Mycobacterium avium complex (MAC) in AIDS

CD4 count?

species?

CD4 <50

M. avium and M. intracellulare

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Mycobacterium avium complex characteristics 

Weakly Gram +, strongly acid-fast aerobic rods

• Disease: host response to infection

– asymptomatic colonization, chronic localized pulmonary disease, solitary nodule

– disseminated disease (particularly in patients w/ AIDS)

• Tissues can be filled w/ Mycobacteria; 100s – 1000s

bacteria / ml of blood

36

Mycobacterium avium complex infection types/progess

(1) pulmonary MAC: immunocompetent hosts

(2) disseminated MAC: individuals w/ advanced AIDS

(3) MAC lymphadenitis in children

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leading cause of death among people living with AIDS

Tuberculosis (TB)

– common opportunistic infection associated w/ HIV

38

infection pretty common in HIV + people 

Salmonellosis

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Bartonella henselae characteristics 

(Gram – rod)

– Bacillary angiomatosis: vascular proliferative

disease in immunocompromised patients

– Infection primarily involves skin, lymph nodes, or liver and spleen

– Subacute endocarditis

– Cat-scratch disease: chronic regional lymphadenopathy assoc. w/ cat scratch

40

Bacillary angiomatosis

appears as purplish to bright red skin patches, often resembling Kaposi's sarcoma

Bacillary angiomatosis:

reactive vascular proliferation

secondary to infection by

Bartonella henselae

41

 HIV infection + hepatitis, -> more likely to develop

liver toxicity from medications

42

 

most common viral

cause of congenital defects

CMV 

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CMV Establishes latent infection in

mononuclear lymphocytes, stromal cells of bone marrow

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CMV member of 

Member of Betaherpesvirinae,

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CMV damages 

Weakened immune system: virus can cause damage to eyes through infection and inflammation

• retina (CMV retinitis, untreated leads to blindness)

• digestive tract

• lungs or other organs

46

Human Herpesvirus (HHV-1 and -2) in AIDS patients 

– HIV increases the probability that infection is more severe, sores may take longer to heal, systemic symptoms may also be more severe (may cause brain damage and blindness)

– Immunocompromised people and neonates are at risk for disseminated, life-threatening disease

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Human Papillomavirus (HPV) in AIDS

 

– Infection w/ both HPV and HIV increases a woman's risk even further: cervical cancer occurs more often, more aggressively in women who are HIV-positive

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Progressive multifocal leukoencephalopathy (PML)/ JC virus

Serious brain infection caused by the human polyomavirus JC virus

• speech problems

• weakness on one side of the body • loss of vision in one eye

• numbness in one arm or leg

– PML usually occurs only when the immune system has been severely damaged

49

Progressive multifocal leukoencephalopathy

grossly as irregular areas of granularity in white matter, which bear some resemblance to the plaques of

demyelination with multiple sclerosis

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Kaposi's sarcoma, HHV-8 (KSHV) characteristics 

– Tumor of the blood vessel walls

– Rare in people not infected with HIV

– Usually appears as pink, red or purple lesions on the skin and mouth (with darker skin, the lesions may look dark brown or black)

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THE MOST FREQUENTLY DETECTED TUMORS IN AIDS PATIENTS

Kaposi's sarcoma, HHV-8 (KSHV)

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Non-Hodgkin's lymphoma: most common w/

inherited immune

deficiency, autoimmune disease, or HIV

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Viral infections: HTLV-1, Hep C, and EBV, ↑ risk of

developing

non-Hodgkin's lymphoma

54

Fungi that leads to pneumonia in aids patients 

Candidiasis

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common central nervous system infection

associated with HIV

Cryptococcal meningitis

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– caused by a fungus that is present in soil or associated with bird or bat droppings

– does not seem to spread person to person

Cryptococcal meningitis

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Cryptococcal meningitis CD4 count

CD4 cell counts are below 100

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Major virulence factors Cryptococcus neoformans

polysaccharide capsule, phenol oxidase enzyme, ability to grow at 37°C

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Pneumocystis jirovecii (formerly P. carinii, PCP)

– Previously considered to be a protozoan parasite

– Infection almost exclusively in debilitated and immunosupressed patients

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Toxoplasmosis

 parasite spread primarily by cats

• humans can contract by touching their mouths with their hands after changing cat litter

• eating raw or undercooked meat, especially pork, lamb and venison

– Leads to encephalitis in many patients with AIDS

61

Cryptosporidiosis

– Infection → intestinal parasite commonly found in animals (ingestion of contaminated food, water)

– Leads to severe, chronic diarrhea in people w/ AIDS

self-limited syndrome in HIV-infected individuals w/ CD4 counts > 200, disease refractory to therapy in individuals w/ suppressed CD4 counts