Propagation & characterization of human herpesvirus-7 (HHV-7) isolates in a continuous T-lymphoblastoid cell line (SupT1)

After initial culture of HHV-7 in PHA-stimulated human cord
blood mononuclear cells (HCBMC), six HHV-7 isolates were
propagated successfully in an immature continuous
T-lymphoblastoid cell line SupT1. All six isolates infected
efficiently the SupT1 cells, and the infected cells became
grossly enlarged and multinucleated 7-21 days post-infection.
Various stages of HHV-7 morphogenesis were detected. Cell-free
supernatants from HHV-7-infected SupT1 cells were infectious
to HCBMC as well as to SupT1 cells. The HHV-7-infected SupT1
and HCBMC cell lysates contained more infectious virus than
the centrifuged cell culture fluid supernates from the same
culture. The HHV-7 isolates H7- 2, H7-3, JHC, and JB,
concentrated 500 times, had average infectivity titers of
10(3.0) TCID50/ml while strains H7-4 and KHR titered
approximately 1-2 logs higher.

When all six HHV-7 isolates were propagated in SupT1 and culture
fluid supernatants were examined 14-21 days post-infection by negative
stain electron microscopy they contained an average of 1.9 x 10(9)
virus particles/liter. IFA and ELISA, using HHV-7/SupT1 cell lysate
as an antigen, seem to correlate well in detecting high and
low HHV-7 antibody in sera from chronic fatigue patients and
healthy donors as controls. HHV-7 from SupT1 cell culture was
free of HHV-6 and other human herpesviruses as tested by PCR,
and the HHV-7 PCR signal was still strong when the viral
preparation was diluted to 4.82 x 10(2) genome copies. Since
HCBMC are expensive to obtain and available in only small
amounts, it is difficult to obtain large quantities of HHV-7
antigen. On the other hand, the SupT1 cell is an excellent
source to produce consistently sufficient quantities of HHV-7
for purification studies, development of immunodiagnostics, in
vivo infectivity studies, evaluation of antiviral drugs, and
molecular biological studies.

Ablashi DV, Handy M, Bernbaum J, Chatlynne LG, Lapps W, Kramarsky B, 

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