fever and lymphadenopathy

Question 1

causes of lymphadenopathy

Answer 1

• proliferation of lymphocytes in response to local infection
• malignant calls metastasis to node
• proliferation malignant lymphocytes
• inflammation within nodes resulting from killing of lymphocytes infected by a virus

Question 2

investigations of lymphadenopathy

Answer 2

• adjacent infection
• adjacent cancer
• features of lymph node cells (fine need aspiration)
• evidence of infection that targets lymphoid cells

Question 3

infections of lymph nodes (pathogens)

Answer 3

viral

• EBV
• CMV
• HIV

bacterial

• S. aureus
• M. TB

Question 4

Herpes

Answer 4

DNA viruses

• EBV (glandular fever)
• CMV (less severe GF-like symptoms)

acute infection followed by latent or chronic infection

Question 5

Acute EBV infection and symptoms

Answer 5

• infectious mononucleosis / kissing disease
• minor illness in children, more severe in adults
• virus transmitted in saliva
• incubation 4-6 weeks, illness 1-2 weeks

fever, sore throat, cervical adenopathy, malaise, fatigue

Question 6

diagnosis of EBV

Answer 6

• lymphocytosis (>50% of white cells)
• atypical lymphocytes
• abnormal LFTs
• monospot test
• specific EBV serology

Question 7

describe monospot test

Answer 7

infected individual produces heterophiles antibodies that bind to RBC membranes of guinea pigs, sheep, horses

Question 8

HIV structure and replication

Answer 8

1. GP120 binds to CD4 and co-receptor on cell surface
2. viral envelope fuses with cell membrane
3. viral RNA is copied into DNA by reverse transcriptase
4. HIV DNA is taken into host nucleus
5. HIV DNA is cut and integrated into host DNA
6. viral DNA copies into mRNA, translated into proteins
7. assemble into virus particles, which bud off gaining envelope = replication

Question 9

HIV pathogenesis

Answer 9

1. 10^9 T helper cells produced/day
2. HIV infects T helper cells
3. infected cells produce 10^9 HIV particles/day
4. helper cells infected are recognised by cytotoxic T cells and destroyed

Question 10

rapid evolution of HIV

Answer 10

• copies of DNA made, errors not corrected (no ‘proof reading’
• generation of mutant viruses everyday

Question 11

time course of untreated HIV

Answer 11

1. level of HIV increases for weeks after infection
2. cytotoxic T cells kill infected cells
3. killing of affected lymphocytes causes a brief ‘glandular-fever-like’ illness
4. B lymphocytes produce antibodies to HIV
5. level of HIV remains stable for many years
6. T helper lymphocyte numbers continue to fall
7. T lymphocyte depletion is severe there AIDS illnesses
8. level of HIV in blood increases further

Question 12

HIV diagnosis

Answer 12

1. detect antibodies in HIV blood
   a) screening test = ELISA
   b) confirming test = western bolt
2. detect HIV genome in blood
   - PCR

Question 13

ELISA test

Answer 13

Enzyme linked immunosorbent assay

1. HIV antigens stuck to base of Elisa well
2. serum added - antibodies in serum attach to HIV antigens
3. anti-human antibodies with adherent enzyme added, enzyme attaches to serum AB
4. reagent added - cleaved by enzyme on anti-human AB
   = colour change occurs

Question 14

AIDS defining illnesses

Answer 14

• pneumonia
• meningitis
• brain abscesses
• oesophagitis
• TB

Question 15

HIV treatment

Answer 15

targets

• transverse transcriptase
• protease
• HIV binding
• DNA integration

no effective vaccine