HHV-6 Flashcards
What cells does HHV-6 infect and where is it latent?
Preferentially replicates in active CD4 cells, latent in monocytes of salivary glands
Which of the HHV-6 variants is associated with disease? Which can be detected in ciHHV-6?
HHV-6B is associated with clinical disease.
Both HHV-6A and HHV-6B can integrate and be detected in ciHHV-6
How would you investigate possible ciHHV-6 in HSCT patient?
Be suspicious in samples with high viral loads. Quantify in whole blood - if >5.5 log then this is strongly suggestive of ciHHV-6.
Test a pre-transplant sample from the recipient +/- a sample from the donor
What is the suggested cut-off viral load that is suggestive of ciHHV-6?
Log 5.5 copies/ml in whole blood, or log 4.5 in serum (don’t use plasma as this is only useful for detecting lytic virus!)
What are the clinical syndromes associated with HHV-6?
Roseola
Febrile seizures
Encephalitis
What are the clinical syndromes associated with HHV-6 in immunosuppressed?
Rash
Fever
Seizures
Encephalopathy
Limbic encephalitis
Cognitive dysfunction, amnesia, mental status changes)
Lymphadenopathy
Colitis
Hepatitis
CMV reactivation
GVHD
If a HSCT recipient has ciHHV-6 and the donor does not, what would you expect to see post engraftment?
HHV-6 VL will decrease as engraftment occurs. Haemopoetic cells will not have ciHHV-6, but HHV-6 will still be detected in their other cells
What testing for HHV-6 is performed pre- and post- HSCT? And is there prophylactic treatment?
None and no (studies have not shown benefit of prophylactic/pre-emptive treatment)
What are the symptoms of HHV-6 encephalitis in HSCT?
What is the most common presentation?
When does this most often occur?
What type of HSCT is the highest risk?
Delirium, amnesia, ataxia, and neurocognitive decline. Myelitis associated with severe pain in extremities and systemic pruritus. Seizures are common.
Post transplant limbic encephalitis (PALE)
2-6 weeks post transplant
Cord blood
What is the diagnostic criteria for HHV-6 encephalitis post HSCT?
DNA detected in CSF and acute onset encephalopathy, seizures or memory loss AND exclusion of other aetiology and ciHHV-6 excluded
What testing can be performed to confirm ciHHV-6?
Serial whole blood PCR which demonstrates >5.5 log copies/ml
FISH on nails and hair
Droplet digital PCR to show 1:1 ratio of HHV-6 genomes to cells
Treatment of HHV-6 encephalitis in HSCT
Reduction of immunosuppression should be considered (however very rarely used in this group)
Antivirals - ganciclovir or foscarnet, or dual therapy with both - choice will depend on side effects
