gene. Also, mutations in IZKF3, which also had
HIV integrations detected in two of our three
participants, was recently associated with a form
of acute lymphoblastic leukemia (35). Fourth, as
somatic mutations that “drive” cancers are
estimated to only convey a 0.4% growth advantage (36), HIV integration into genes with
subtle enhancement of cell proliferation may
be difficult to detect as clonal due to our limited sampling.
HIV-infected cells that express viral proteins
are likely to be eliminated by immune surveillance,
or virus replication may lead to cell lysis. Whether
the proliferating and persisting HIV-infected cells
that we describe harbor replication-competent
virus is critical to defining their role in perpetuating the infectious virus reservoir. Undoubtedly,
some clonal populations persist due to defects
in expression of the proviral genome (9, 10, 37).
Although we did not evaluate viral sequences for
replication competency, lethally hypermutated
viral genomes were linked to three integration
sites (Fig. 2). However, cells producing viremias
with identical env sequences have been shown
to harbor replication-competent virus (38). Also,
approximately 12% of proviruses refractory to
in vitro induction were found to have intact
genomes and may be infectious (27). Although
transcriptional interference was not detected
in the aforementioned noninduced viral transcripts (26, 27), others have observed that the
site of integration may cause transcriptional interference (34, 39–43).
In conclusion, HIV integration into genes
associated with cancer or cell cycle regulation
appears to confer a survival advantage that allows these cells to persist during suppressive
ART, with cell proliferation appearing to serve
as an important mechanism of HIV persistence.
To be defined are the mechanisms contributing
to cell proliferation, the role of proliferating cells
in perpetuating the infectious virus reservoir,
and whether therapies that target HIV-infected
proliferating cells, specific genes, or their products
may contribute to a curative strategy for HIV
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We wish to express gratitude to the study participants who
donated their time and provided specimens, and to N. H. Tobin,
A. J. Melvin, and K. M. Mohan for their contributions to this study.
Additionally, we thank Y. C. Ho, R. and J. Siliciano, H. Imamichi
and C. Lane, and N. Malani and F. Bushman for providing their HIV
integration site data. HIV env sequences generated from specific
integration sites were deposited in GenBank under accession
numbers (KM025062 to KM025124 and KM201287 to KM201295).
Additional HIV env sequences were deposited in GenBank under
accession numbers AY075701 to AY077450 (44), AY483287 to
AY484389 (2), and KC314011 to KC315287 (8). Sequences of
HIV-3′-LTR and adjacent chromosome integration sites are
available in table S3. Other data are tabulated in the main paper
and in the supplementary materials. Integration site sequences
and HIV sequence alignments are available for download at http://
html. These studies were funded by R01AI091550 (L.M.F.),
K23AI077357 (T.A. W.), R01 AI111806 (J.I.M.), the Molecular
Profiling and Computational Biology Core of the University of
Washington’s Center for AIDS Research (P30 AI027757), and the
Canadian Institutes of Health (HIV/AIDS Research Initiative award
201311CVI-322424-244686) (C. Y.K.C.). We wish to thank A. Embry
and D. Lawrence at the National Institutes of Health for their
support. The authors report no conflicts of interest related to this
Materials and Methods
Figs. S1 to S3
Tables S1 to S3
20 May 2014; accepted 27 June 2014
Published online 10 July 2014;
Helminth infection reactivates latent
g-herpesvirus via cytokine
competition at a viral promoter
T. A. Reese,1 B. S. Wakeman,2 H. S. Choi,3 M. M. Hufford,4 S. C. Huang,1 X. Zhang,1
M. D. Buck,1 A. Jezewski,1 A. Kambal,1 C. Y. Liu,1 G. Goel,5 P. J. Murray,6
R. J. Xavier,5† M. H. Kaplan,4† R. Renne,3† S. H. Speck,2† M. N. Artyomov,1
E. J. Pearce,1 H. W. Virgin1‡
Mammals are coinfected by multiple pathogens that interact through unknown
mechanisms. We found that helminth infection, characterized by the induction of the
cytokine interleukin-4 (IL-4) and the activation of the transcription factor Stat6,
reactivated murine g-herpesvirus infection in vivo. IL-4 promoted viral replication and
blocked the antiviral effects of interferon-g (IFNg) by inducing Stat6 binding to
the promoter for an important viral transcriptional transactivator. IL-4 also reactivated
human Kaposi’s sarcoma–associated herpesvirus from latency in cultured cells.
Exogenous IL-4 plus blockade of IFNg reactivated latent murine g-herpesvirus
infection in vivo, suggesting a “two-signal” model for viral reactivation. Thus, chronic
herpesvirus infection, a component of the mammalian virome, is regulated by the
counterpoised actions of multiple cytokines on viral promoters that have evolved to
sense host immune status.
Mammals are populated by many chronic viruses, termed the virome, which can regulate host physiology and disease sus- ceptibility (1). For example, more than 90% of humans are latently infected with
herpesviruses that, after clearance of acute infec-
tion, produce little infectious virus and often cause
no overt disease. Like the human g-herpesviruses
Epstein-Barr virus (EBV) and Kaposi’s sarcoma–
associated herpesvirus (KSHV), murine g-erpesvirus-
68 (MHV68) establishes lifelong latency. Studies
in this model system showed that the cytokine
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