Lecture 1

Viral Replication & Pathogenesis

HIV/AIDS: uma visão geral e patogeneses

HIV/AIDS: Overview and Pathogenesis.

HIV/AIDS: uma visão geral e patogeneses

Suggested literature:Stevenson M HIV-1 Pathogenesis. Nat Med. 2003 9:853-60

Shattock RJ, Moore JP. Inhibiting sexual transmission of HIV-1 infection. Nat Rev Microbiol. 2003 1:25-34

Stebbing J, Gazzard B, Douek DC. Where does HIV live? N. Engl J Med. 2004 350:1872-80

Haase AT. Perils at mucosal front lines for HIV and SIV and their hosts. Nat Rev Immunol. 2005 5:783-92.Gonzalez-Scarano F, Martin-Garcia J.The neuropathogenesis of AIDS. Nat Rev Immunol. 2005 5:69-81.

The course of HIV infectionO Curso da Infecção pelo HIV

The course of HIV infection

O Curso da Infecção pelo HIV

1. Acute Phase (fase aguda)

2. Intermediate (asymptomatic) phase -viral load stabilizes at a “set point”. (Fase Intermediária (assintomático). Carga viral estabiliza em um limiar).

3. Late (symptomatic) phase (Fase tardia-sintomática).

The acute phase of replicationA fase aguda da replicação

1. Massive replication occurs in gut lymphoid tissue

1. Replicação maciça ocorre no tecido linfóide do intestino.2.CD4+ CCR5+ memory T-cells are main

targets for infection.2. Células de memória CD4+CCR5+ são os principais alvos da infecção. 3.Replication spills out into lymph nodes

and blood.3. A Replicação espalha-se para linfonodos e sangue.

The importance of gut-associated lymphoid tissue (GALT)A importância dos tecidos linfóides associados ao intestino (GALT)

• GALT is the body’s major reservoir of activated, CD4 CCR5+ T-cells, the preferred targets for R5 virus replication. GALT é o maior reservatório de células T CD4+CCR5+. Os alvos preferidos para replicação do vírus R5.

• Rapid depletion of these T-cells from the GALT occurs after infection of macaques by R5 viruses - SIVmac, SHIV-162P (R. Veazey, A. Lackner; J. Harouse, C. Cheng-Mayer).Rápida depleção dessas células T do GALT ocorre após a infecção de

macacos por virus R5- SIVmac, SHIV-162P

Depletion of Human Gut CD4+ T Cells

• Gut biopsies from >50 individuals

• CCR5+ CD4 T cells are massively depleted from gut

• High frequency of infected cells at all stages of disease

What can this look like?

• There is a marked reduction in mucosal lymphoid tissue even in acute infection Ha uma reducao marcada de mucosal lymphoid tecido ate na infeccao aguda

HIV- HIV+

Courtesy of Rick Koup

The course of HIV infection

O Curso da Infecção pelo HIV

1. Acute Phase (Fase aguda)

2. Intermediate (asymptomatic) phase -viral load stabilizes at a “set point”. (Fase intermediária (assintomática)-carga viral estabiliza em um limiar.

3. Late (symptomatic) phase. Fase tardia (sintomática)

.

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Viral "Set Point" as a Predictor of Disease

Time

% of patients with AIDSat 5 years

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The course of HIV infection

O Curso da infecção pelo HIV

1. Acute Phase (Fase aguda)2. Intermediate (asymptomatic) phase -viral load stabilizes at a “set point”. (Fase intermediária (assintomática)-carga viral estabiliza em limiar.3. Late (symptomatic) phase. Fase tardia (sintomática)

HIV Associated Dementia

• About 30% AIDS patients suffer severe neurological disorders known as AIDS dementia complex (ADC) or HIV-associated dementia (HAD).Cerca de 30% dos pacientes com AIDS sofrem graves alterações conhecidas como Complexo demencial da AIDS (ADC) ou Demencia associada ao HIV (HAD).

• Cognitive, behavioral, and motor deficits resulting from HIV-1 infection within the brain. Deficites cognitivo, comportamental e motor resultam da infecção pelo HIV-1 dentro do cérebro.

What causes AIDS ?

How are CD4+ T-cells lost?Como as celulas T CD4+ sao perdidas?

Is it the virus? E o virus?

Or an indirect mechanism?Ou um mecanismo indireto?

What causes AIDS?O que causa AIDS?

• There is a direct relationship between virus set-point and progression to AIDS.Existe uma relação indireta entre o limiar do vírus e a progressão para a AIDS.

• AIDS is a direct consequence of CD4 lymphocyte depletion.AIDS é uma consequência da depleção de linfócitos CD4.

• HIV-1 is cytopathic for CD4 lymphocytes.HIV-1é citopático para linfócitos CD4

What causes AIDS?O que causa AIDS?

• Logically therefore, high level virus replication and lymphocyte destruction must be the cause.Logicamente, então, o alto nível da replicação do virus e a

destruição de linfócitos devem ser as causas.• This view is not supported by studies of

non-pathogenic SIV infection. Esse visão não é confirmada por estudos de infecção de SIV não patogênico.

SIVsm in Sooty

Mangabeys

SIVmac in Rhesus macaques

HIV-2 in Humans

SIVcpz in Chimps

HIV-1 in Humans

AIDSNo disease

Sooty Mangabeys do not develop diseaseSooty Mangabeys não desenvolvem doença

---High levels of virus replication.Altos níveis de replicação viral.

---Continuous rounds of viral replication with infected cells dying as quickly as in HIV infections.Contínuo círculo de replicação viral com células infectadas morrendo tão rápido quanto na infecção pelo HIV.

---Bystander apoptosis is low.Apoptose “bystander” é baixa

---Immune activation is low.A ativação imunológica é baixa

Conclusion: Viral killing of lymphocytes may be necessary but not sufficient for immunodeficiency. Conclusão: morte viral dos linfócitos pode ser necessária, mas não suficiente para causar imunodeficiência.

Sousa, Giorgi et al. 02

CD4+ T-cell depletion correlates more closely with levels of immune activation than viral load.

Depleção de células T CD4+é melhor correlacionada com os níveis

de ativação imunológica que a carga viral

Cause of pathogenic primate lentivirus infections:

Causas de infeccões patogênicas de lentivirus de primatas.

• Pathogenic: Immunodeficiency, profound viremia, CD4 cell turnover, immune activation, neuropathogenicity.

Patogenica: imunodeficiência, intensa viremia, renovação de células CD4, ativação imunológica, neuropatogênicidade.

• Non-pathogenic: profound viremia, CD4 cell turnover.

Não-patogênica: intensa viremia, renovação de células CD4.

Therefore, it is the extent of immune activation that determines pathogenicity.

Assim, é a extensão da ativação imunológica que determina a patogenicidade.

Cause of disease? O que causa AIDS?

• Hypothesis: Massive acute replication produces viral proteins which damage the integrity of the gut wall. Hipotese: a replica aguda produz a proteina viral que danifica a integridade da parede da tripa.

• Bacterial products (LPS) are able to cross the mucosa and cause inflammation/activation of underlying cells. May promote eventual destruction of lymphoid tissue. Os produtos bacterianos (LPS) sao capazes de cruzar a mucosa e a inflamacao/ativacao de causa da celulas subjacentes. Pode promover a destruicao eventual do tecido lymphoid

0 dpi 14 dpi

The Gut and Immune Activation in HIV

Does microbial translocation occur as a result of HIV-induced CD4 T cell depletion of the gut mucosa, thereby causing systemic immune activation?

Courtesy of Rick Koup

YesPlasma LPS levels are a quantitative indicator of microbial translocation

Increased plasma LPS levels in HIV+ individuals

Courtesy of Rick Koup

No evidence for microbial translocation in non-pathogenic natural SIV infection of sooty mangabeys

Non-Pathogenic Natural SIV Infection

Natural SIV infection — non-pathogenic, high VL, low immune activation

Do they have less microbial translocation?

Courtesy of Rick Koup

CD4+ T cell depletion allows bacteria to cross

the mucosa?Since when are CD4+ T

cells involved in control of bacteria?

Control of Extracellular Microbial Pathogens

•Neutrophils

•Th17 cells

•Memory CD4 T cells that produce IL-17 and IL-22 (not IFN or IL-4)

•IL-17 is thought to be important for anti-bacterial immunity

•Recruits neutrophils

•Induces proliferation of GI enterocytes

•Induces production of anti-bacterial defensins

•What is the status of Th17 cells in HIV-infection?• Quantity, phenotype, infection frequency, antigen specificity, functionality in blood and GI tracts of HIV-infected and uninfected individuals

Antigen specificity of Th17 cells

Th17 cells are specific for bacterial and fungal but not common viral antigens (even those in

mucosa) As celulas Th17 sao especificas para bacterias e fungos mas nao antigenos virais comuns (ate aquela mucosa)

Courtesy of Rick Koup

Th17 Cells in GI Tract: HIV-Negative

Th17 cells are more prevalent in the GI tract than the blood As Celulas Th17 sao mais prevalentes na via GI do que no sangue Courtesy of Rick Koup

Th17 cells are preferentially lost from the GI tract of HIV-infected

individuals

Th17 Cells in GI Tract: HIV-Infected

anti-CD3

PMA/iono

Cause of Disease?

• Destruction of Th17 cells undermines ability to control microbial agents resulting in immune activation.

• Does immune activation undermine CD4 homeostasis?

• Why is mucosal integrity undermined only in pathogenic infection?

How do we stop it?

• Very early therapy to stop massive viral onslaught

• Preservation of mucosal integrity

• Anti-inflammatory strategies to prevent chronic damage.