Jpn. J. Infect. Dis., 53, 2000

Laboratory and Epidemiology Commumications

Possible Enhancement of GB Virus C Infection in Cultured Cells

by Addition ofAnti‑E 1 Antibodies
Min*o Hijikata*, Yohko K. Shimizu, Tomoko Kiyoharal,
Shunj i Mishiro2 and Hiroshi Yoshikura
Department ofRespiratoyy Diseases, Resewch Institute, International Medical Center ofJapan,
Toyama 1‑21‑1, Shinjuku‑ku, TobJo 162‑8655,
JDepartment of Viral Disease and Vaccine Conty10l, National Institute of Infectious Diseases,
Musashimurqyama‑shi. Too,0 208‑0011 and2Department ofMedical Sciences, Toshiba General Hospital.
Shinagawa‑ku, Too/0 140‑8522
Communicated by Hiroshi Yoshikura(Accepted July 10, 2000)

Recently, a novel member of the virus family FIaviviridae
was identified as a causative agent for human non‑A‑E
hepatitis, called GB vims C (GBV‑C) or hepatitis G virus

E I peptide (amino acid number 61 ‑80) in Freund's adjuvant,and a serum sample was obtained 6 weeks a触r the last lnJeC‑tion. Enzyme‑linked immunosorbent assay (ELISA) revealed(HGV). GBVIC is distantly related to hepatitis C virus (HCV).

that the immune serum was reactive with the homologous

HCVvirions are bound to anti‑HCV antibodies as immune

peptide. Double irrmunoprecipitatiOn uslng GBV‑Cand HCV
positive plasma #53 (3) revealed that the majorityofGBV‑C

complexes in the circulation of chronically infected hosts, andthis phenomenon is related to the antibody‑escapemutations
inthe hypervariable reg10n OfE2 protein. However, GBV‑C hasvirions were brought by the immune serum to the pellet.

no hypervariable region Within envelope proteins. Therefore,56oC for 30 minand diluted 10‑fold. One hundred microliters

the mechanism for GBV‑C to establish persistent infection
may be different from that for HCV.

ofdiluted sera were mixed with an equal volume of 1:100

We obtained serial sera from a Japanese patientwith acutewere inoculated into 1 ml ofH‑903 cell (3) suspension (5 X

lymphatic leukemia who had developed hepatitis after105/cells) and incubated for 2 h at 37oC. After being washedonce, the cells were culturedfurtherinthe continuouspresence

The immune and control pre‑immune sera were heated atdilution of #53 serum and incubated at 40C ovemight. They

repeated blood transfusions. The patient was found to be
infected with GBV‑C. Immunoprecipitation of the serawithof immune or pre‑immune serum at a rlnal concentration ofanti‑human lgG fわllowed by detection of GI】V‑C RNA by

10‑2. presence of the viral sequence in the cells and in theRT‑PCR (I) revealed that, in the rlrSt Sample, GBVIC RNA

supernatants was monitored for 32 days by the RTIPCR

was present only in the supernatant, while from the second
sample on, GBV‑C RNA was present in thepellet as well;method as describedina previous report (3).Asshowninthei.e., from the second point On, the antibody was present. In

spite of the presence of the antibody, however, GBV‑C RNA

Table. Detection ofGBV‑C RNA by RT‑PCR in cell culture

continued toincrease; i.e.,theandbody did not suppI℃SS GBVIC

Pre‑immune serum Immune serum

replication (Figure). This observation led us to the hypothesis

CellSupCellSupthat the antibody was enhancing even the infection, as371 31 72 2732

reported for otherflaviviruses (2).

十十十十+ + +In order to test this possibility, we examined the effect ofEl antibody on GBV‑Cinfection in cultured cells. A rabbit
was injected intradermally twice (at a 1‑month interval)

with500 LLg keyhole limpet hemocyanin‑conjugated synthetic+*Corresponding author: Fax: + 8 1 ‑3‑3207‑1 038, E‑mail: minakoh
PI: post inoculation, Sup: supematant@ri. imcj. go.jp
133++++十一十++++十+Jpn. J. Infect. Dig., 53, 2000
010

101Ol

LJlO

200120(【L POtdo3)YNtJU･>凸9･S i

7/9

8/1 1 8/18

8/25

9/25 (Month/Date)

Figure. Agarose gel electrophoresis of PCR products after immunoprecIPltationwith anti‑human lgG. Nucleic acids extracted
from supematants orpeIlets were diluted serially I 0‑fold and subjected to RT‑PCR (0, undiluted; 1 , 10‑fold diluted; 2, 1 02‑
fold diluted; 3, 1 03‑diluted). Arrows indicate serum‑sampling points. Sup: supematant, ALT: alanine aminotransferase.

Table, both immune and pre‑immune sera did not inhibit

REFERENCES

detection of GBV‑C RNA during culture. Rather, Viral RNA

1. Hijikata, M. and Mishiro, S. (1996): Circulating immune

tended to persist longer in the culture treated with immune

complexes that containHCV but not GBV‑C in co‑infected
hosts. Int. Hepatol. Commun., 5, 339‑344.

serum (27 days vs. 13 days in the supematant).

2. Porterfield, J. S. ( 1 986):Antibody‑dependent enhancement

This work was supported, in part, by a grant‑in‑aid &om theMinistry of Health and Welfare of Japan for a Comprehensive

ofviral infectivity. Adv. Virus Res., 3 1 , 335‑355.

3. Shimizu, Y. K., Hijikata, M., Kiyohara, T., Kitamura, Y.

10‑year Strategy fわr Cancer Control to H. Yand Yoshikura, H. (1999): Replication of GB vims C(hepatitis G virus) in interferon‑resistant Daudi cells･ J･
Viro1., 73, 841 I‑8414.

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