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2016 ; 90
(16
): 7469-7480
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Complex Interplay between HIV-1 Capsid and MX2-Independent Alpha
Interferon-Induced Antiviral Factors
#MMPMID27279606
Bulli L
; Apolonia L
; Kutzner J
; Pollpeter D
; Goujon C
; Herold N
; Schwarz SM
; Giernat Y
; Keppler OT
; Malim MH
; Schaller T
J Virol
2016[Aug]; 90
(16
): 7469-7480
PMID27279606
show ga
Type I interferons (IFNs), including IFN-?, upregulate an array of IFN-stimulated
genes (ISGs) and potently suppress Human immunodeficiency virus type 1 (HIV-1)
infectivity in CD4(+) T cells, monocyte-derived macrophages, and dendritic cells.
Recently, we and others identified ISG myxovirus resistance 2 (MX2) as an
inhibitor of HIV-1 nuclear entry. However, additional antiviral blocks exist
upstream of nuclear import, but the ISGs that suppress infection, e.g., prior to
(or during) reverse transcription, remain to be defined. We show here that the
HIV-1 CA mutations N74D and A105T, both of which allow escape from inhibition by
MX2 and the truncated version of cleavage and polyadenylation specific factor 6
(CPSF6), as well as the cyclophilin A (CypA)-binding loop mutation P90A, all
increase sensitivity to IFN-?-mediated inhibition. Using clustered regularly
interspaced short palindromic repeat (CRISPR)/Cas9 technology, we demonstrate
that the IFN-? hypersensitivity of these mutants in THP-1 cells is independent of
MX2 or CPSF6. As expected, CypA depletion had no additional effect on the
behavior of the P90A mutant but modestly increased the IFN-? sensitivity of
wild-type virus. Interestingly, the infectivity of wild-type or P90A virus could
be rescued from the MX2-independent IFN-?-induced blocks in THP-1 cells by
treatment with cyclosporine (Cs) or its nonimmunosuppressive analogue SDZ-NIM811,
indicating that Cs-sensitive host cell cyclophilins other than CypA contribute to
the activity of IFN-?-induced blocks. We propose that cellular interactions with
incoming HIV-1 capsids help shield the virus from recognition by antiviral
effector mechanisms. Thus, the CA protein is a fulcrum for the dynamic interplay
between cell-encoded functions that inhibit or promote HIV-1 infection.
IMPORTANCE: HIV-1 is the causative agent of AIDS. During acute HIV-1 infection,
numerous proinflammatory cytokines are produced, including type I interferons
(IFNs). IFNs can limit HIV-1 replication by inducing the expression of a set of
antiviral genes that inhibit HIV-1 at multiple steps in its life cycle, including
the postentry steps of reverse transcription and nuclear import. This is observed
in cultured cell systems, as well as in clinical trials in HIV-1-infected
patients. The identities of the cellular antiviral factors, their viral targets,
and the underpinning mechanisms are largely unknown. We show here that the HIV-1
Capsid protein plays a central role in protecting the virus from IFN-induced
inhibitors that block early postentry steps of infection. We further show that
host cell cyclophilins play an important role in regulating these processes, thus
highlighting the complex interplay between antiviral effector mechanisms and
viral survival.