HIV

Question 1

Type I transmission pattern (North America, Europe)

Answer 1

M:F ratio 10:1, HOMOSEXUAL MEN, IVDAs, rarely prenatal, seroprevalence <1%. The prevalence of HIV in women and heterosexual transmission are both rising in the US.

Question 2

Type II transmission pattern (Sub-Saharan Africa, Haiti)

Answer 2

M:F ratio 1:1, HETEROSEXUAL TRANSMISSION, blood, dirty needles, significant prenatal spread, seroprevalence >1%.

Question 3

HIV risk of transmission:

Answer 3

2x increased risk for each 1 log increase in HIV viral load
Overall risk is ~1/900 for insertive intercourse
Risk higher for receptive partner, and anal sex is more risky than vaginal sex. Perinatal infection occurs in 1% of cases when treatment is given.
In general: IDU > anal sex > vaginal sex > oral sex

Question 4

Types of HIV:

Answer 4

HIV-1 (more common) and HIV-2 (less common).
HIV-1 has subtypes A, B, C (and other rarer subtypes).
HIV-1 subtype B is most common in the United States.

Question 5

Stages of HIV infection: INFECTION:

Answer 5

M(macrophage)-trophic phenotype infects macrophages and dendritic cells using CD4 and CCR5 receptors. Infection spread to regional lymph nodes.

Question 6

Stages of HIV infection: SEROCONVERSION:

Answer 6

Burst of viremia accompanied by mono-like seroconversion syndrome in half of patients. CD8+ T-cells (expressing granzyme and perforin) and antibodies to the viral envelope reduce viral replication to a “setpoint” (which tends to be lower in women).

Question 7

Stages of HIV infection: CLINICAL LATENCY:

Answer 7

Most patients remain free of symptoms for 10-12 years and viral load remains stable. CD4 count falls at a rate of 50-75/year. Development of numerous resistant quasi-species.

Question 8

Stages of HIV infection: AIDS:

Answer 8

CD4+ count less than <200 (the definition of AIDS). Clinical immunodeficiency becomes apparent with susceptibility to numerous opportunistic infections, and death results in 2-3 years.

Question 9

CDC recommendation for HIV screening:

Answer 9

All adults should be screened once for HIV infection REGARDLESS OF RISK.

Question 10

Risk of perinatal HIV infection:

Answer 10

25% without therapy (same risk with breastfeeding). Risk reduced to 1% with treatment.

Question 11

Risk of transmitting HIV based largely on:

Answer 11

HIV viral load. Higher in patients with acute infection than chronic infection. MUCOSAL ULCERATION (or other damage) also increases the risk of acquiring or transmitting HIV.

Question 12

Diagnosis of ACUTE HIV infection:

Answer 12

Check a viral load and HIV serology. Initially, viral load will be high while HIV serology is negative. HIV VIRAL LOAD is the cornerstone of the diagnosis of acute infection.

Question 13

What makes HIV difficult to cure:

Answer 13

HIV DNA can remain integrated in the DNA of host CD4+ T-cells without causing damage to the cell.

Question 14

HIV preferentially infects:

Answer 14

HIV-specific T-cells, leading to the death of the very cells that are produced to destroy the infection. However, while HIV infects these cells, it usually does not cause their destruction. Overwhelming IMMUNE ACTIVATION is thought to play a role in this process.

Question 15

Acute HIV symptoms:

Answer 15

Mono-like illness. Fever, headaches, fatigue, and rash. CNS symptoms are relatively common, pharyngitis is less common.

Question 16

Viral escape

Answer 16

The process of mutation that renders the HIV virus unrecognizable to the immune system.

Question 17

Non-immunologic problems associated with HIV:

Answer 17

HIV infects neurons (causing neurological symptoms), and induces a chronic inflammatory state, which gives rise to enhanced risk of cardiovascular disease. Due to its random integration into the genome, it may also produce cancer.

Question 18

Viral load helps to predict:

Answer 18

Prognosis. Persons with a higher viral load progress to AIDS faster than patients with low viral loads.

Question 19

HIV diagnosis:

Answer 19

First with an ELISA (99.9% sensitive) followed by a confirmatory western blot.

Question 20

Value of HIV viral load vs. CD4 count:

Answer 20

The HIV viral load is a measure of how QUICKLY the patient is likely to progress to AIDS. The CD4 count is a measure of the current functional status of the immune system.

Question 21

The CD4 count below which it is appropriate to begin anti-retroviral treatment:

Answer 21

500. Strongly recommended below 350, mandatory below 200.

Question 22

HIV patients are at risk for:

Answer 22

A variety of COMMON infections: bacterial pneumonia (pneumococcus and haemophilus), tuberculosis (leading cause of death in HIV patients WORLDWIDE), viral hepatitis, herpes and herpes zoster, Candida, psychiatric disease and many kinds of cancer.

Question 23

CD4 count <200:

Answer 23

PCP leading to bilateral pneumonia w/ DYSPNEA. Lactate dehydrogenase is elevated (due to hypoxia). Diagnosis is by induced sputum or specimens acquired through bronchoscopy (silver stains, immunofluorescent stains).
It is both treated and prophylaxed with TMP/SMX. Steroids are indicated if the patient is not exchanging air well.

Question 24

CD4 count <100:

Answer 24

Most individuals have been exposed by adulthood.
Toxoplasmosis leads to encephalitis with ring-enhancing lesions in the brain. Symptoms include personality changes, headaches, and seizures.
It is treated with pyrimethamine-sulfadiazine + leucovorin and prophylaxed with TMP/SMX.

Question 25

CD4 count <50:

Answer 25

1) MAC can cause a febrile wasting syndrome.
Prophylaxis with azithromycin.
Treatment with clarithromycin, ethambutol, rifabutin.
2) Cryptococcus can cause pneumonia and meningitis. It causes extremely HIGH OPENING PRESSURES on lumbar puncture. Diagnosis is by cryptococcal antigen in blood or CSF.
Treatment with amphotericin B and flucytosine.
Prophylaxis with fluconazole.
3) CMV retinitis presents with blurry vision, flashes, or scotoma. ONLY CMV-positive patients are at risk.
Treatment with IV ganciclovir or oral vanganciclovir.
Prophyaxis only for those who have had CMV retinitis before.

Question 26

Patient infected with HIV are likely to be coinfected with:

Answer 26

Hepatitis B and C. Patients are less likely to spontaneously clear either of these viruses. In the developed world, LIVER DISEASE is a leading cause of death among HIV patients.

Question 27

Cancers that are common in HIV infected patients:

Answer 27

Those caused by chronic viral infections: lymphoma (EBV-associated), cervical and anal cancers (HPV-associated), etc.