S10, A to C). This was attributed to an expansion
in the number of conventional CD49b+ NK cells
while the number of liver-resident CD49a+ NK
cells (15) remained stable, leading to a substantial change in the hepatic CD49b+ to CD49a+ NK
cell ratio over the course of infection (fig. S10, D
and E). NK cell depletion resulted in significantly
elevated viremia at day 3 p.i.. However, the kinetics
of viral clearance and the extent of liver injury
were similar in NK cell–depleted mice and controls
(fig. S10, F and G). Thus, NK cells may contribute
to the control of NrHV early in infection, but they
are not required for NrHV clearance.
Chronic viral hepatitis in humans and chronic
LCMV infection in mice are characterized by
antigen-specific T cell dysfunction and exhaustion
(10, 11). Mechanisms contributing to this phenomenon include the up-regulation of checkpoint
inhibitors (e.g., PD-1 (programmed cell death 1))
or suppression by regulatory Foxp3+CD4+ T cells
(Tregs) (10, 11). After transient CD4+ T cell depletion, NrHV established a long-term chronic infection in immune-competent mice (Fig. 3A) that
was associated with mild liver inflammation (fig.
S11). We found that chronic infection, in contrast
to acute clearance, coincided with the emergence
of intrahepatic Tregs that remained at high levels
throughout infection (Fig. 4, A and B). Thus, suppression of antiviral immune responses by Tregs
might play a role in the establishment of chronic
Chronic NrHV infection also displayed elevated frequencies of intrahepatic CD8+ T cells
with an exhausted phenotype characterized by
PD-1highCD44low surface expression (Fig. 4, C and D),
coexpression of the inhibitory receptors 2B4 and
Tim-3, and high expression levels of the transcription factor eomesodermin (fig. S12A) (16, 17).
The frequencies of these cells were lower in acute
resolving mice, suggesting that chronic NrHV
infection may lead to T cell exhaustion (Fig. 4C).
Checkpoint inhibitor blockade [e.g., the inhibition of PD-1:PD-1 ligand (PD-1L) interactions]
is a promising immunotherapy that can invigorate exhausted T cells (18). PD-1/PD-1L blockade
showed mixed results when tested in HCV-infected
chimpanzees and patients, so its efficacy in the
setting of chronic viral hepatitis is still unclear
(19, 20). We thus tested whether PD-1L blockade
could reduce viremia during chronic NrHV infection in mice (fig. S6D). Blockade at day 42 p.i.
significantly reduced viremia (0.5 to 1 log) at day
14 after start of treatment, whereas blockade at
day 84 p.i. reduced viremia only at day 21 after
start of treatment. At an even later time point
(day 140 p.i.), no decrease in viremia was observed (Fig. 4, E to G, and fig. S12, B and C). These
results suggest that blockade of the PD-1:PD1-L
pathway can reduce NrHV viral loads only during
early chronic infection.
In this study, we have developed an immune-
competent inbred mouse model of an HCV-related
hepacivirus. Because NrHV can adapt to infect
mice with diverse genetic backgrounds, this model
can potentially help unravel mechanisms of hepa-
civirus host adaptation, immune evasion, and the
development of liver disease. It can also be used
to select for viral variants that can establish chronic
infection in immune-competent mice. Given the
similarities between NrHV infection in mice and
HCV infection in humans, this model might prove
valuable in the future for the development and
testing of HCV vaccines.
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We thank M. MacDonald, M. Saeed, and W. Schneider for
manuscript editing. This work was supported by the NIH (grants
R01AI072613, R01CA057973, and R01AI131688-01), The Starr
Foundation, the Greenberg Medical Research Institute, and several
generous donors (C.M.R.); NIH grant AI107631 and the Nationwide
Children’s Hospital Research Institute (A.K); the Danish Council
for Independent Research [grants 6110-00595 and 6111-00314
(T.K.H.S); grant 4004-00598 (J.B.)]; The Novo Nordisk Foundation
[grants NNF15OC0017404 (T.K.H.S.) and NNF14OC0012533
(J.B.)]; The Lundbeck Foundation [grants R192-2015-1154
(T.K.H.S), R221-2016-1455 (J.B.)]; and NIH grant R01A193244
(K.G). The HCV-related hepacivirus NrHV is available from the
authors under a material transfer agreement. The ORF consensus
sequence of the NrHV rat inoculum was deposited at GenBank
(accession no. MF113386). The authors declare no conflict
Material and Methods
Figs. S1 to S12
Tables S1 and S2
References (21, 22)
11 October 2016; resubmitted 3 April 2017
Accepted 5 June 2017
Guanine glycation repair by DJ-1/
Park7 and its bacterial homologs
Gilbert Richarme,1,2 Cailing Liu,3† Mouadh Mihoub,1† Jad Abdallah,1,4†
Thibaut Leger,5† Nicolas Joly,6 Jean-Claude Liebart,1 Ula V. Jurkunas,3 Marc Nadal,7
Philippe Bouloc,8 Julien Dairou,2 Aazdine Lamouri9
DNA damage induced by reactive carbonyls (mainly methylglyoxal and glyoxal), called DNA
glycation, is quantitatively as important as oxidative damage. DNA glycation is associated with
increased mutation frequency, DNA strand breaks, and cytotoxicity. However, in contrast to
guanine oxidation repair, how glycated DNA is repaired remains undetermined. Here, we found
that the parkinsonism-associated protein DJ-1 and its bacterial homologs Hsp31, YhbO, and YajL
could repair methylglyoxal- and glyoxal-glycated nucleotides and nucleic acids. DJ-1–depleted
cells displayed increased levels of glycated DNA, DNA strand breaks, and phosphorylated p53.
Deglycase-deficient bacterial mutants displayed increased levels of glycated DNA and RNA
and exhibited strong mutator phenotypes. Thus, DJ-1 and its prokaryotic homologs constitute
a major nucleotide repair system that we name guanine glycation repair.
DNA repair systems undo DNA damage produced by reactive oxygen species, reactive carbonyls, alkylating agents, ultraviolet (UV) radiation, deoxyuracil incorporation, and replication errors. DNA repair mechanisms
include nucleotide pool sanitization, direct repair,
base excision repair (BER), nucleotide excision
repair (NER), mismatch repair (MMR), homol-
ogous recombination repair, and nonhomologous
end joining (1, 2). Nucleic acids undergo perma-
nent glycation by glyoxal (GO) (CHO-CHO) and
methylglyoxal (MGO) (CH3-CO-CHO), which are
ubiquitously present in cells as by-products of
sugar metabolism and constitute their major
glycating agents (3). The most susceptible nucleo-
tides are guanosine (G) and deoxyguanosine (dG)
(3). Cellular amounts of dG glycated by MGO
(dG-MG) are similar to those of the major oxidized
nucleotide, 8-oxo-dG (3). Thus, glycation is an important source of DNA damage in vivo and is
associated with increased mutation frequency,
DNA strand breaks, and cytotoxicity (3, 4). However, whereas oxidized nucleotides are repaired by
the guanine oxidation repair system, no dedicated
system is known for glycated nucleotide repair,
although it may be mediated by NER and MMR (3).
208 14 JULY 2017 • VOL 357 ISSUE 6347 sciencemag.org SCIENCE
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