HHV 6,7 Flashcards
HHV6 and 7- belong to which subfamily
beta herpes
differentiate hhv 6a, 6b and 7 based on
nucleotide sequence homology
receptor
seropositivity in 1 yr
2 yrs
adult
exanthem subitum by
infection spread by
integration
infects
latent in
salivary presence
congenital infection
reactivation in HSCT, SOT
more prediliction for
IP
MC cf
febrile seizure %
other neuro features
see notes
HHV-6 in transplant- risk factors; when reactivate
within the first month after transplant, and reactivation is increased with reduced cellular immunity, particularly in patients receiving anti-CD3 antibody or corticosteroids, and in those who have undergone allogeneic or cord blood transplants
HHV6 and HIV
HHV-6 induces expression of CD4 on the surface of T cells, which can increase susceptibility to HIV infection. However, infection of cells with HHV-6 results in reduced expression of the HIV coreceptor CXCR4 on the surface of cells and increased expression of the RANTES (regulated on activation, normal T-cell expressed and secreted) chemokine, which can inhibit replication of CCR5 tropic HIV strains in HHV-6-infected cells.
exanthem subitum - cf
high fever that usually lasts for 3 to 4 days.
At the time of defervescence, patients develop a macular or maculopapular rash that begins on the neck or trunk, spreads to the extremities, and persists for a few hours to 2 days
The disease may be accompanied by cough, cervical and occipital lymphadenopathy, erythema of the tympanic membranes, conjunctivitis, eyelid edema, bulging fontanelles, lymphadenopathy, diarrhea, or Nagayama spots (red papules on the soft palate or base of the uvula). The median duration of symptoms is 9 days.
Congenital Infection due to hhv 6
%
symptoms
diagnosed by
HHV-6 congenital infections (defined by detection of virus in cord blood) occurred in 1% (57/5638) of births and, unlike infections later in life, were asymptomatic.
In a follow-up study, neurodevelopmental scores were significantly lower at 1 year of age in infants who had HHV-6 congenital infection.
HHV 6 in immunocompromissed
1) fever and rash early on
2) delayed monocyte and platelet engraftment
3) limbic encephalitis- in cord blood transplant, GVHD, mismatched; 2-6 weeks after HSCT, medial aspect of temporal lobes, elevated protein in CSF
4) myelitis
5) encephalitis
6) pneumonitis
7) giant cell hepatitis
8) kidney
diagnosis of exanthem subitum
clinically
diagnosis of hhv 6,7
best: viral RNA / protein in tissue or site of infection (gp60 in hhv6)
DNA - pro: very early infection before serology
con: 1) cant differentiate latent infection and primary infection (high level or rising level of DNA or RNA- indicates new inf - >10^3 copies per 10^6 PBMC; DNA in serum or plasma more indicative than in whole blood; present in 1/3rd of healthy csf)
2) 1-2% have integrated (overcome by : do from nail and hair to see somatic cells and see; >320000 copies/ml of whole blood or >1 copy/leucocyte or persistent - suggestive of ciHHV6; ddPCR- copy/cell 1)
serology- rises 1 week after inf- peaks 2 weeks- persist for life- cross react with hhv 7
treatment of hhv 6 and 7
ganciclovir, foscarnet and cidofovir
