Immuno 3 - Secondary immune deficiencies and HIV 1 infection Flashcards
o Commonest cause of secondary immune deficiency worldwide
• Malnutrition
B cell lymphoproliferative disorders associated with immune deficiency include
MM CML NHL MGUS - monoclonal gammopathy of uncertain significance
Clinical features of immune deficiences
- Infections – severe, persistent, recurrent, unusual
- Autoimmune conditions (immune cytopaenias)
- Allergic disease
- Persistent inflammation
- Cancer (particularly viral associated EBV, HHV-8)
First line ix if suspecting secondary immune deficiency/ immunodeficiency
FISH for an immunodeficiency
• FBC
o Hb
o Neutrophil/Lymphocyte/Platelet count
• Immunoglobulins o IgG, IgA, IgM, IgE o Low gG: Protein losing enteropathy Prednisolone >10mg/day o Low IgG + Low IgM: Monitor for B cell neoplasm Hx of exposure to rituximab o Low IgG + Low IgA Primary antibody deficiency
• Serum Complement
o C3, C4
o Screens for C1 inhibitory deficiency, Immune complex disease, Lupus
• HIV test
o 18-80 years
What is Goods’ syndrome?
Goods’ syndrome
- Thymoma and antibody deficiency
- Combined T and B cell (absent) defect
- CMV PJP and muco-cutaneous candida
- Autoimmune disease (Pure red cell aplasia, Myasthenia gravis, Lichen planus)
Other ix in secondary immunodeficiencies
U+Es
LFTs
Bone profile + Ca
Total protein + Albumin
Urine Protein: creatinine
Serum protein electrophoresis
o Separation of serum proteins by charge
o Detection of discrete bands
Monoclonal identified by immunofixation with labelled IgG, IgM, IgA anti-sera
Monoclonal protein associated with MM, WMG, NHL and MGUS
o SPE can miss free light chain disease
Serum free light chains
o Free light chain disease seen in 20% of MM cases
o Essential for work up of B cell lymphoproliferative disorders (SPE can miss free light chain disease)
WMG = Waldenstorm macroglobulinaemia
Secondary investigations for immune deficiencies
• Concentration of vaccine antibodies
o Tetanus toxin – protein antigen
o Pneumovax vaccine – carbohydrate antigen (all 23 serotypes or to individual pneumococcal serotypes)
o If reduced vaccine antibody levels:
Offer test immunisation with Pneumovax II + tetanus to investigate immune function
Looking at T cell independent activity
Failure to respond to vaccination:
• Part of dx criteria for a number of primary antibody deficiency syndromes
• Criteria for receipt of IgG replacement therapy for secondary antibody deficiency syndromes
• Analysis + quantification of lymphocyte subsets using flow cytometry o CD3+CD4+ T cells o CD3+CD8+ T cells o CD3-CD56+CD16+ NK cells o CD19+ B cells
Third line investigations for secondary immunodeficiencies
- Analysis of naïve + memory T and B cell subsets
- Assessment of IgG subclasses
- Determination of anti-cytokine and anti-complement antibodies
• Genetics
o Whole exome/Whole genome sequencing - ?primary or ?secondary immune defect
Which antibodies are responsible for the following conditions
SARS-CoV-2 infection
disseminated NTM (non-tuberculous mycobacteria) infection
cryptococcal infection
B cell lymphoproliferative disorders + SLE
o Anti-type 1 IFN antibodies (IFN-α and IFN-ω) SARS-CoV-2 infection
o Anti-type 2 IFN antibodies (IFN-γ) disseminated NTM (non-tuberculous mycobacteria) infection
o Anti-GM-CSF antibodies cryptococcal infection
o Anti-C1 inhibitor antibodies + acquired late onset angioedema B cell lymphoproliferative disorders + SLE
Management of secondary immune deficiency
- Treat underlying cause
- Advise on measures to reduce exposure to infection
• Immunisation
o Against respiratory viruses + bacteria
o Offer vaccines to household contacts
• Education to treat bacterial infections promptly
o May require higher + longer therapies courses
• Prophylactic antibiotics
o For confirmed recurrent bacterial infection
criteria for
IgG replacement therapy for secondary antibody deficiency syndromes
• Underlying cause of hypogammaglobinaemia cannot be reversed or reversal is contraindicated
OR
• Hypogammaglobulinemia associated with
o Drugs
o Therapeutic monoclonal antibodies targeted at B cells and plasma cells
o Post-HSCT
o NHL, CLL, MM or other relevant B-cell malignancy
AND
- Recurrent or severe bacterial infection despite continuous oral antibiotic therapy for 6 months
- IgG <4.0g/L (excluding paraprotein/monoclonal protein)
- Failure of vaccine response to unconjugated pneumococcal or other polysaccharide vaccine challenge
HIV
Time period between infection to symptomatic disease/AIDS
Highest risk of transmission
10 years
risk of transmission highest within the first 6 months
Mechanism of action of HIV
- Targets CD4+ cells
- Gp120 (initial binding) and gp41 (conformational change) binds to CD4+ T cells + HIV co-receptors
- Binds to CD4 + then chemokine co-receptor CCR5 or CXCR4
• Replicates via a DNA intermediate using reverse transcriptase – converts RNA into DNA which can be integrated into host cell’s genes
- Integrates into host genome
- HIV DNA transcribed into viral mRNA transcribed into viral proteins package + release of mature virus
• Gag protein – intrastructural support for HIV
HIV1 lineages
HIV-1 consists of 4 distinct lineages M, N, O, and P
Each lineage arose from independent transmission from chimpanzees (Group M,N,O) and gorillas (O,P)
Group M virus is pandemic, consists of 9 subtypes and 40 recombinant forms
What happens in HIV during acute phase chronic phase AIDS to
CD4 T cell counts in the blood
Mucosal CD4 t cells
Immune activation
CD4 T cell counts in the blood
acute phase - drop
chronic phase - small rise
AIDS - dramatic decline
Mucosal CD4 t cells
drop in acute phase, never recover
Immune activation
significant increase
What predicts disease progression in HIV
Degree of immune activation
o Degree of immune activation can predict progression of infection (independent of CD4+) + response to ART
Initial viral burden (viral load set point)
• 3-6 months after initial infection a steady state HIV-1 viral concentration is observed in blood viral load set point
• Progression to symptomatic HIV-1 infection stratified by VL set point
• Viral load set point correlated with long-term outcome
• Magnitude of VL set point influenced by
o Viral genotype
o CD8 T cell immune
o Host genetics (HLA, CCR5)
o Immune activation
Characteristic features of the immunology of HIV-1 infection
• CD4 T cell depletion
• Impairment of CD4 + CD8 T cell function – “exhaustion”
o Present but don’t work very well – don’t secrete antiviral inhibitory cytokines/chemokines, are not cytotoxic
• Disruption of lymph node architecture + impaired ability to generate protective T and B cell immune responses
• Loss of antigen-specific humoral immune responses
o Recurrent bacterial infections in sub-sacharan Africa are the main drivers of infection
• Chronic immune activation
How long does HIV need to integrate into T cells?
• Integration of HIV provirus in memory T cells within 72 hours of infection formation of long-lived reservoir of latent infection does not respond to current ART
How does HIV survive?
• Error prone nature of HIV RT short generation time of viral cycle + length of infection driving force for viral diversity
• Viral mutation
o Evasion of the CTL (cytotoxic T lymphocyte) immune responses
o Emergence of drug resistant virus in patients with inadequate drug treatment
What happens during the acute phase of HIV infection?
• Significant increase in HIV-1 viral load in blood
• Flu like symptoms in 70% of cases
o Infectious mononucleosis type picture
- Transient reduction in blood CD4+ T cells
- C8 T cell activation (CD38+ and HLA-DR+)
- Increase in CD8 T cell immune response coincides with drop in VL
- Induction of HIV-1 specific antibodies
How does HIV damage the immune system?
- HIV remains infectious even when Ab coated
- Activated infected CD4+ helper T cells –> killed by CD8+ T cells and are anergised (disabled)
- CD4 T-cell memory lost & failure to activate memory CTL
- Monocytes and dendritic cells –> not activated by the CD4+ T cells –> cannot prime naïve CD8+ CTL (due to impaired antigen presenting functions)
- Infected monocytes dendritic cells –> killed by virus or CTL
- Quasispecies are produced due to error-prone reverse transcriptase = these escape from immune response
- Effective immunity requires antibodies to prevent infection and neutralize virus, and sufficient CTL to eliminate latently infected cells
Diagnosis of HIV infection (7)
• 4th generation combined HIV-1 antigen/antibody tests
o Will detect infection 1 month post acquisition
• rapid point of care HIV-1 tests
o Results available within 20 mins
o Less sensitive than 4th generation test
• Assay detect o p24 antigen – part of nuclear capsid o gp41 – from HIV-1 Group O o gp160 – envelop protein on HIV-` o gp36 – HIV 2
• HIV-1 RNA tests
o In cases where HIV-1 serological tests are negative but there is high clinical suspicion of acute HIV-1 infection
• HIV-1 RNA and/or DNA tests
o Used to diagnose infection in children <18 months
• Screening test – detects anti-HIV ab via ELISA
• Confirmation test – detects ab via Western Blot
o A positive test requires the patient to have seroconverted (i.e. started to produce ab)
o This happens after around 10 weeks incubation
HIV specific tests
• HIV-1
o Viral load
o Genotype (for ART drug resistance)
o Tropism test to confirm co-receptor use in HIV-1 in patients who may be candidates for treatment with CCR5 antagonists
• HLA-B*5701 blood test
o To avoid prescribing Abacavir
o Risk of severe hypersensitivity in those with this allele (can die from it)
o to prevent hypersensitivity reaction with protease inhibitors
• Analysis of T cell counts
o CD4 T cell count + percentage – to stratify risk of infection
o CD4: CD8 t cell ratio
Infections + CD4 count
500 cells/mm3
400 cells/mm3
300 cells/mm3
200 cells/mm3
100 cells/mm3
50 cells/mm3
> 500
Community acquired organisms - HSV, zoster, pneumonia, bacterial skin infections, oral, skin fungal infections
400 cells/mm3
Kaposi’s sarcoma
Cutanous kaposis
300
Hairy leukoplakia
TB
<200 PCP Cryptosporidium Candida Fungal pneumonia
<100
Toxoplasmosis
Cryptococcus
Candida, HSV, CMV oesophagitis
<50 CMV Cryptococcus Lymphoma MAC (mycobacterium avium complex) Toxoplasmosis Visceral Kaposis
At which CD4 levels do the following present + how do you treat?
PCP
Toxoplasma
MAC (mycobacterium avium complex)
PCP
<200 cells/mm3
Co-trimoxazole
Toxoplasma
<100 cells/mm3
Co-trimoxazole
MAC
<75 cells/mm3
Azithromycin
At which CD4 count should ART be considered
All HIV-1 infected individuals should consider ART irrespective of CD4 T cell count
Life cycle of HIV
Attachment + entry Reverse transcription + DNA synthesis Integration to host DNA Viral transcription Viral protein + synthesis Assembly + budding
Give an example of an attachment inhibitor
Maraviroc
CCR5 antagonist
Give an example of a fusion inhibitor + state 2 side effects
Enfuvirtide
Local reaction to injection
Hypersensitivity (0.1-1%)
Give 5 limitations of HAART
o Doesn’t eradicate latent HIV-1
o Fails to restore HIV-specific T cell responses
o Toxicities
o Cannot eliminate infection once HIV-1 has integrated into host DNA
o Does not reverse chronic immune inflammation – RF for CV, liver, bone, CNS disease
but
o Can prevent new cells from becoming infected
Give a few examples of NRTIs
Nucleoside reverse transcriptase inhibitor
Zidovudine (can also be given to pregnant women) Lamivudine Didanosine Stavudine Zalcitabine Emtricitabine
Abacavir
Combivir
Trizivir
Epzicom
NRTIs SE
rare
fever
headache
GI disturbance
NtRTI + SE
Nucleotide reverse transcriptase inhibitor
Tenofovir
Bone and renal toxicity
NNRTI + SE
Non nucleoside transcriptase inhibitors
Nevirapine (heaptitis + rash)
Delaviridine (rash)
Efavirenz (CNS effects)
Integrase inhibitors
Raltegravir
lvitegravir
Dolutegravir
Protease inhibitors
SE
Ritonavir Darunavir Indinavir Nelfinavir Amprenavir Fosamprenavir Lopinavir Atazanavir Saquinavir
SE
Hyperlipidaemias
Fat redistribution
T2DM
main reason why HIV-1 patients change HIV therapy
Drug toxicity rather than virological failure
ART in the UK consists of
2 NRTI (backbone regimen) and 1 NRTI or
2NRTI (backbone regimen) and 1 Integrase inhibitor
Give examples of drugs used in the backbone regimen
Abacavir + lamivudine
Emtricitabine + tenofovir
Give examples of drugs used for the third drug of choice in ART
Integrase inhibitors
Raltegravir
Dolutegravir
Life expectancy of HIV +ve individuals
If ART started before significant immune damage – similar life expectancy to age + sex matched to seronegative controls
After how long is the viral load detectable in blood once someone stops ART?
o If stopped, HIV-1 replication re-commences + will be readily detectible in blood 2-3 weeks later
Monitoring individuals on ART (5)
• Check for compliance with drug therapy + adverse SE
• Regular HIV-1 viral load
• Monitor liver, renal, bone, lipid toxicity
• CD4 T cell monitoring not needed fir counts >350 cells/ul
• Assess CV + osteoporosis RF – HIV drugs can increase bone loss
•
Describe the shock and kill strategy for treatment of HIV
SHOCK
drugs to reactivate HIV-1 virus
KILL
agents to eliminate HIV-1 infected cells
ART
prevent infection of new cells
Which immunoglobulin does prednisolone affect and at which doses
Prednisolone – selective depression in IgG, seen with higher doses >10mg/day
