Host and viral determinants for MxB restriction of HIV-1 infection

MxB restricts HIV-1 infection by directly interacting with the HIV-1 core, which is made of viral capsid; however, the contribution of MxB to the HIV-1 restriction observed in alpha interferon (IFN-␣)-treated human cells is unknown. To understand this contribution, we used HIV-1 bearing the G208R capsid mutant (HIV-1-G208R), which overcomes the restriction imposed by cells expressing MxB. Here we showed that the reason why MxB does not block HIV-1-G208R is that MxB does not interact with HIV-1 cores bearing the mutation G208R. M yxovirus resistance proteins represent a family of interferon-inducible factors with a wide range of antiviral activities (1-3). The myxovirus B (MxB) gene was originally cloned from a human glioblastoma cell line treated with alpha interferon (IFN-␣) (4, 5). MxB as well as the related protein MxA belong to the dynamin-like family of proteins, which have diverse functions ranging from vesicle transport to antiviral activity (1, 6-11). The most studied dynamin-like protein that exhibits antiviral activity is MxA (1, 2). Contrary to MxB, the antiviral role of MxA has been extensively studied for viruses including influenza virus (1, 12-15), tick-borne Thogoto virus (16), African swine fever virus (17), hepatitis B virus (18), and La Crosse virus (19,20). The antiviral activity of the long form of MxB was recently described (9, 21-23); these investigations led to the discovery that the IFN-␣-inducible protein MxB blocks HIV-1 infection.Genetic evidence suggested that the HIV-1 capsid is the determinant for the ability of MxB to block HIV-1 infection (9,22,23). In agreement with these findings, we recently demonstrated that MxB binds to the HIV-1 capsid and correlated the ability of MxB to block HIV-1 infection with inhibition of uncoating (24). We also showed that the ability of MxB to block infection requires a capsid binding domain and an oligomerization domain provided by the 90 N-terminal and the 143 C-terminal amino acids of MxB, respectively (24). In addition, the work of others and our work showed that the 90 N-terminal amino acids of MxB are important for its ability to bind capsid and restrict HIV-1 infection (24)(25)(26).MxB contains a previously described putative nuclear localization signal on its N-terminal 25 amino acids (4). Deletion of the N-terminal 25 amino acids annihilates the ability of MxB to block HIV-1 infection and to bind to the HIV-1 core (23,24,27). Mutagenic studies have revealed that the N-terminal 25 amino acids of MxB exhibit a triple-arginine motif ( 11 RRR 13 ) that is important for restriction and the ability of MxB to bind to the HIV-1 core (28, 29). HIV-1 CA-NC expression and purification. The CA-NC proteins of HIV-1 and HIV-1 bearing the G208R capsid mutant (HIV-1-G208R) were expressed, purified, and assembled as previously described (30). MATERIALS AND METHODS CellMxB binding to in vitro-assembled HIV-1 and HIV-1-G208R CA-NC complexes. HEK 293T cells were transfected with a plasmid expressing the wild-type MxB protein. Forty-eight hours after t...

Section: Fig 5 Ifn-␣ Treatment Of Thp-1 Cells Prevents the Formationsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

MxB Is Not Responsible for the Blocking of HIV-1 Infection Observed in Alpha Interferon-Treated Cells

Opp

Vieira

Schulte

et al. 2016

“…Genomic DNA was extracted from HEK293T cells infected with HIV-1 NLX.Luc.RϪ in the presence of 1.39 M PF74 or dimethyl sulfoxide (DMSO) 5 days after infection using the DNeasy blood and tissue kit (Qiagen) for integration site analysis. Illumina sequencing of DNA libraries generated from ligation-mediated (LM)-PCR amplification of genomic DNA was used to determine HIV-1 integration sites essentially as described previously (46,47). Briefly, DNA digestion by MseI and BglII was performed overnight, followed by purification by using the QIAquick PCR purification kit (Qiagen).…”

Section: Methodsmentioning

confidence: 99%

“…Sequences were mapped to the hg19 version of the human genome using BLAT, ensuring that the genomic match started immediately after GGAAAATCTCTAGCA, which corresponds to the integrase-processed HIV-1 U5 end. Bioinformatics analysis of HIV-1 integration sites was performed as described previously (46,47).…”

Section: Methodsmentioning

confidence: 99%

Roles of Capsid-Interacting Host Factors in Multimodal Inhibition of HIV-1 by PF74

Saito

Ferhadian

Sowd

et al. 2016

Self Cite

The viral capsid of HIV-1 interacts with a number of host factors to orchestrate uncoating and regulate downstream events, such as reverse transcription, nuclear entry, and integration site targeting. PF-3450074 (PF74), an HIV-1 capsid-targeting low-molecular-weight antiviral compound, directly binds to the capsid (CA) protein at a site also utilized by host cell proteins CPSF6 and NUP153. Here, we found that the dose-response curve of PF74 is triphasic, consisting of a plateau and two inhibitory phases of different slope values, consistent with a bimodal mechanism of drug action. High PF74 concentrations yielded a steep curve with the highest slope value among different classes of known antiretrovirals, suggesting a dose-dependent, cooperative mechanism of action. CA interactions with both CPSF6 and cyclophilin A (CypA) were essential for the unique dose-response curve. A shift of the steep curve at lower drug concentrations upon blocking the CA-CypA interaction suggests a protective role for CypA against high concentrations of PF74. These findings, highlighting the unique characteristics of PF74, provide a model in which its multimodal mechanism of action of both noncooperative and cooperative inhibition by PF74 is regulated by interactions of cellular proteins with incoming viral capsids. IMPORTANCEPF74, a novel capsid-targeting antiviral against HIV-1, shares its binding site in the viral capsid protein (CA) with the host factors CPSF6 and NUP153. This work reveals that the dose-response curve of PF74 consists of two distinct inhibitory phases that are differentially regulated by CA-interacting host proteins. PF74's potency depended on these CA-binding factors at low doses. In contrast, the antiviral activity of high PF74 concentrations was attenuated by cyclophilin A. These observations provide novel insights into both the mechanism of action of PF74 and the roles of host factors during the early steps of HIV-1 infection.T he emergence of HIV-1 variants resistant to currently approved antiretrovirals necessitates the development of novel classes of inhibitors that possess high levels of genetic barriers to resistance (1). Among viral proteins that are not exploited as an antiviral target, the viral capsid (CA) protein is an attractive target for antiviral interventions (2, 3). CA, a genetically fragile protein (4), exhibits limited tolerance to genetic changes and, hence, would predictably temper the evolution of drug resistance (5). The mutational intolerance of CA is caused by structural and functional constraints (6-8). CA, which is the major virion core structural protein, generated by protease-mediated cleavage of the precursor Gag Pr55 protein, plays essential roles during both particle assembly and disassembly (9, 10). Perhaps it is this genetic fragility that makes CA highly vulnerable to host immune responses, such as CD8-specific adaptive immunity (11) and TRIM5␣-mediated intrinsic immunity (12), both of which target highly conserved portions of CA.Recent work discovered several novel smal...

“…Correlations of integration site distributions relative to various genomic features were conducted using BEDTools (36). Statistical analysis of resulting integration frequencies was determined using R (37,38), with statistical significance being calculated by Fisher's exact test and a Wilcoxon rank sum test. …”

Section: Purification Of T N and T CM Cd4mentioning

confidence: 99%

Establishment and Reversal of HIV-1 Latency in Naive and Central Memory CD4⁺T CellsIn Vitro

Zerbato

Serrao

Lenzi

et al. 2016

Self Cite

The latent HIV-1 reservoir primarily resides in resting CD4؉ T cells which are a heterogeneous population composed of both naive (T N ) and memory cells. In HIV-1-infected individuals, viral DNA has been detected in both naive and memory CD4 ؉ T cell subsets although the frequency of HIV-1 DNA is typically higher in memory cells, particularly in the central memory (T CM ) cell subset. T N and T CM cells are distinct cell populations distinguished by many phenotypic and physiological differences. In this study, we used a primary cell model of HIV-1 latency that utilizes direct infection of highly purified T N and T CM cells to address differences in the establishment and reversal of HIV-1 latency. Consistent with what is seen in vivo, we found that HIV-1 infected T N cells less efficiently than T CM cells. However, when the infected T N cells were treated with latency-reversing agents, including anti-CD3/CD28 antibodies, phorbol myristate acetate/phytohemagglutinin, and prostratin, as much (if not more) extracellular virion-associated HIV-1 RNA was produced per infected T N cell as per infected T CM cell. There were no major differences in the genomic distribution of HIV-1 integration sites between T N and T CM cells that accounted for these observed differences. We observed decay of the latent HIV-1 cells in both T cell subsets after exposure to each of the latency-reversing agents. Collectively, these data highlight significant differences in the establishment and reversal of HIV-1 latency in T N and T CM CD4؉ T cells and suggest that each subset should be independently studied in preclinical and clinical studies. IMPORTANCE The latent HIV-1 reservoir is frequently described as residing within resting memory CD4؉ T cells. This is largely due to the consistent finding that memory CD4 ؉ T cells, specifically the central (T CM )