HHV7

Question 1

HHV7 structure and classification

Answer 1

Betaherpesvirus
Linear dsDNA

3 main structural elements shared by all herpes viruses:

1. Nucleocapsid - icosahedral contains viral DNA genome
2. Envelope with embedded viral glycoproteins
3. Tegument - protein mixture occupying space between nucleocapsid and envelope

Baltimore: I

Question 2

HHV7 tropism & viral entry

Answer 2

lymphotropic virus that replicates in CD4 T lymphocytes. It can be induced from latency within T cells by cell activation

HHV-7, unlike HHV-6, utilizes CD4 as a cellular receptor for entry into cells. Thus, HHV-7 infection interferes with HIV-1 infection. HHV-7 does not require CXCR4 for entry but may downregulate its expression with potential implications for HIV-1 coinfection.

Question 3

HHV7 epidemiology

Answer 3

HHV-7 is ubiquitous. More than 95 percent of adults are seropositive. Infection with HHV-7 generally occurs during childhood but peaks at a later age than infection with HHV-6, usually around 3 years of age.

Shed in saliva and other bodily fluids.

Question 4

HHV7 clinical manifestations

Answer 4

1. Generally asymptomatic.
2. Primary infection: fever & rash, febrile seizures, exanthem subitum & roseola infantum, hepatitis, IMN.

Rare: encephalitis, meningitis, lichen planus.

HSCT transplant: HHV-7 DNA in peripheral blood lymphocytes was associated with a longer time to neutrophil engraftment and with symptomatic CMV disease.

Question 5

HHV7 diagnostics & treatment

Answer 5

PCR
Serology - reasearch assays

In vitro, foscarnet and cidofovir inhibit HHV-7 replication by achievable concentrations. The virus is relatively resistant to acyclovir, penciclovir, and ganciclovir.

Small clinical studies suggest that HHV-7 is resistant to ganciclovir at levels that were effective for prevention and treatment of CMV. Sensitivity of HHV-7 to the guanine analogs was different from HHV6, suggesting a difference in selectivity of specific viral enzymes.