miR-198 inhibits HIV-1 gene expression and replication in monocytes and its mechanism of action appears to involve repression of cyclin T1

MicroRNAs in HIV infection: dual regulators of viral replication and host immunity

MicroRNAs (miRNAs) are small non-coding RNAs that play a crucial role in regulating gene expression by binding to target messenger RNAs (mRNAs), leading to their degradation or translational repression. Over the past few years, significant progress has been made in understanding the role of miRNAs in various biological processes, including viral infections such as human immunodeficiency virus (HIV). HIV infection is characterized by a complex interaction between the virus and the host's immune system, where miRNAs have emerged as key regulators. MiRNAs influence HIV infection by modulating both viral replication and the host immune response. Researchers have identified several host miRNAs that suppress or enhance HIV replication by targeting viral genes or host factors essential for the virus life cycle. Conversely, HIV has evolved mechanisms to manipulate the host's miRNA machinery to its advantage. The virus can downregulate or upregulate specific host miRNAs to create a more favorable environment for replication and persistence. Moreover, HIV infection can alter the expression profiles of various miRNAs in infected cells, which can contribute to immune dysregulation and disease progression. Dysregulation of miRNAs is associated with HIV-associated complications, such as neurocognitive disorders and cardiovascular diseases. Understanding the specific roles of miRNAs in HIV pathogenesis could lead to the development of novel therapeutic strategies, such as miRNA-based therapies, to control HIV infection and its associated comorbidities. Understanding the role of miRNAs in HIV infection reveals their significant influence on the complex interactions between the virus and the host, impacting the course of infection and disease progression. Also, continued research in miRNA-mediated mechanisms in HIV holds the potential for uncovering new insights into viral pathogenesis and developing innovative therapeutic approaches.

Expression of microRNAs in the detection and therapeutic roles of viral infections: Mechanisms and applications

In recent years, microRNAs (miRNAs) are potential diagnostic and therapeutic agents for viral infections. Here, we aimed to investigate the expression of microRNAs in the identification and treatment of viral infections. MiRNAs are non-coding molecules that control gene expression and participate in numerous biological processes, including host immunity and pathogen duplication. MiRNAs have played a role in the pathogenesis of various viral infections, such as HIV and HCV. Their presence in the tissues and serum of infected patients has been demonstrated to help predict disease progression, identify disease subtypes, and evaluate treatment responses. Research has shown that miRNAs can detect viral infections by identifying specific miRNAs in serum. For example, miRNA expression profiling was recently used to distinguish between hepatitis C and hepatitis B viral infections precisely. Furthermore, miRNAs can be used to detect the presence of multiple viral infections simultaneously by assessing the expression levels of these miRNAs. Also, miRNAs can differentiate between different genetic variants of the same virus, which is useful for identifying emerging viral strains or drug-resistant ones. MiRNAs have been identified as being a factor in treating viral infections. For example, miRNA mimics have decreased gene expression and halted viral replication in HIV, HCV, and EBV. Moreover, microRNA antagonists have been utilized to inhibit pro-inflammatory cytokines, thereby modulating the immune response and the severity of infections.

A comprehensive overview on the crosstalk between microRNAs and viral pathogenesis and infection

Infections caused by viruses as the smallest infectious agents, pose a major threat to global public health. Viral infections utilize different host mechanisms to facilitate their own propagation and pathogenesis. MicroRNAs (miRNAs), as small noncoding RNA molecules, play important regulatory roles in different diseases, including viral infections. They can promote or inhibit viral infection and have a pro-viral or antiviral role. Also, viral infections can modulate the expression of host miRNAs. Furthermore, viruses from different families evade the host immune response by producing their own miRNAs called viral miRNAs (v-miRNAs). Understanding the replication cycle of viruses and their relation with host miRNAs and v-miRNAs can help to find new treatments against viral infections. In this review, we aim to outline the structure, genome, and replication cycle of various viruses including hepatitis B, hepatitis C, influenza A virus, coronavirus, human immunodeficiency virus, human papillomavirus, herpes simplex virus, Epstein-Barr virus, Dengue virus, Zika virus, and Ebola virus. We also discuss the role of different host miRNAs and v-miRNAs and their role in the pathogenesis of these viral infections.

Human microRNA miR-197-3p positively regulates HIV-1 virion infectivity through its target DDX52 by stabilizing Vif protein expression

MicroRNAs are a part of the integral regulatory mechanisms found in eukaryotic cells that help in maintaining cellular homeostasis by modulating the expression of target genes. However, during stress conditions like viral infection, the expression profile of the microRNAs change, thereby directly modulating the expression of viral genes and/or indirectly targeting the virus by regulating the host genes. The present study intends to identify previously uncharacterized cellular microRNAs, which are significantly modulated upon HIV-1 infection. With the available microarray data of five independent studies in the NCBI GEO database, 10 common yet functionally uncharacterized microRNAs that are deregulated during HIV-1 infection in humans were identified. Their expression profiles were validated in HIV-1 infected human peripheral blood mononuclear cells and a CD4+T cell line. Among them, miR-197-3p showed significant upregulation during HIV-1 infection in all the cell types tested and was selected for further characterization. We then found that miR-197-3p increases progeny virion infectivity through restricting the expression of DDX52. Interestingly, DDX52 showed a negative impact on virion infectivity by downregulating the HIV-1 viral infectivity factor (Vif) at the protein level. Mechanistically, our study also revealed that Vif, DDX52, and APOBEC3G form a complex, which might be responsible for Vif downregulation by proteasomal degradation. Taken together, our results demonstrate that miR-197-3p is a positive regulator of HIV-1 infectivity as it enhances the progeny virion infectivity by targeting DDX52, which is a negative regulator of Vif.

Non-Coding RNAs in HIV Infection, NeuroHIV, and Related Comorbidities

NeuroHIV affects approximately 30-60% of people living with HIV-1 (PLWH) and is characterized by varying degrees of cognitive impairments, presenting a multifaceted challenge, the underlying cause of which is chronic, low-level neuroinflammation. Such smoldering neuroinflammation is likely an outcome of lifelong reliance on antiretrovirals coupled with residual virus replication in the brains of PLWH. Despite advancements in antiretroviral therapeutics, our understanding of the molecular mechanism(s) driving inflammatory processes in the brain remains limited. Recent times have seen the emergence of non-coding RNAs (ncRNAs) as critical regulators of gene expression, underlying the neuroinflammatory processes in HIV infection, NeuroHIV, and their associated comorbidities. This review explores the role of various classes of ncRNAs and their regulatory functions implicated in HIV infection, neuropathogenesis, and related conditions. The dysregulated expression of ncRNAs is known to exacerbate the neuroinflammatory responses, thus contributing to neurocognitive impairments in PLWH. This review also discusses the diagnostic and therapeutic potential of ncRNAs in HIV infection and its comorbidities, suggesting their utility as non-invasive biomarkers and targets for modulating neuroinflammatory pathways. Understanding these regulatory roles could pave the way for novel diagnostic strategies and therapeutic interventions in the context of HIV and its comorbidities.

The Role of MicroRNAs in HIV Infection

MicroRNAs (miRNAs), a class of small, non-coding RNAs, play a pivotal role in regulating gene expression at the post-transcriptional level. These regulatory molecules are integral to many biological processes and have been implicated in the pathogenesis of various diseases, including Human Immunodeficiency Virus (HIV) infection. This review aims to cover the current understanding of the multifaceted roles miRNAs assume in the context of HIV infection and pathogenesis. The discourse is structured around three primary focal points: (i) elucidation of the mechanisms through which miRNAs regulate HIV replication, encompassing both direct targeting of viral transcripts and indirect modulation of host factors critical for viral replication; (ii) examination of the modulation of miRNA expression by HIV, mediated through either viral proteins or the activation of cellular pathways consequent to viral infection; and (iii) assessment of the impact of miRNAs on the immune response and the progression of disease in HIV-infected individuals. Further, this review delves into the potential utility of miRNAs as biomarkers and therapeutic agents in HIV infection, underscoring the challenges and prospects inherent to this line of inquiry. The synthesis of current evidence positions miRNAs as significant modulators of the host-virus interplay, offering promising avenues for enhancing the diagnosis, treatment, and prevention of HIV infection.

The extracellular vesicles in HIV infection and progression: mechanisms, and theranostic implications

Extracellular vesicles (EVs), these minute yet mighty cellular messengers are redefining our understanding of a spectrum of diseases, from cancer to cardiovascular ailments, neurodegenerative disorders, and even infectious diseases like HIV. Central to cellular communication, EVs emerge as both potent facilitators and insightful biomarkers in immune response and the trajectory of disease progression. This review ventures deep into the realm of EVs in HIV-unraveling their pivotal roles in diagnosis, disease mechanism unravelling, and therapeutic innovation. With a focus on HIV, we will highlights the transformative potential of EVs in both diagnosing and treating this formidable virus. Unveiling the intricate dance between EVs and HIV, the review aims to shed light on novel therapeutic strategies that could significantly benefit HIV therapy, potentially even leading to the eradication of HIV.

Targeting Viral Transcription for HIV Cure Strategies

Combination antiretroviral therapy (ART) suppresses viral replication to undetectable levels, reduces mortality and morbidity, and improves the quality of life of people living with HIV (PWH). However, ART cannot cure HIV infection because it is unable to eliminate latently infected cells. HIV latency may be regulated by different HIV transcription mechanisms, such as blocks to initiation, elongation, and post-transcriptional processes. Several latency-reversing (LRA) and -promoting agents (LPA) have been investigated in clinical trials aiming to eliminate or reduce the HIV reservoir. However, none of these trials has shown a conclusive impact on the HIV reservoir. Here, we review the cellular and viral factors that regulate HIV-1 transcription, the potential pharmacological targets and genetic and epigenetic editing techniques that have been or might be evaluated to disrupt HIV-1 latency, the role of miRNA in post-transcriptional regulation of HIV-1, and the differences between the mechanisms regulating HIV-1 and HIV-2 expression.

Targeting noncoding RNAs to reactivate or eliminate latent HIV reservoirs

PURPOSE OF REVIEW

Expression of noncoding RNAs (ncRNAs) is more tissue and cell type-specific than expression of protein-coding genes. Understanding the mechanisms of action of ncRNAs and their roles in HIV replication and latency may inform targets for the latent HIV reservoir reactivation or elimination with high specificity to CD4 + T cells latently infected with HIV.

RECENT FINDINGS

While the number of studies in the field of ncRNAs and HIV is limited, evidence points to complex interactions between different ncRNAs, protein-coding RNAs, and proteins. Latency-reversing agents modulate the expression of ncRNAs, with some effects being inhibitory for HIV reactivation. An important limitation of basic research on the ncRNA mechanisms of action is the reliance on cell lines. Because of cell type specificity, it is uncertain whether the ncRNAs function similarly in primary cells.

SUMMARY

Comprehensive functional screens to uncover all ncRNAs that regulate HIV expression and the detailed exploration of their mechanisms of action in relevant cell types are needed to identify promising targets for HIV reservoir clearance. Classes of ncRNAs as a whole rather than individual ncRNAs might represent an attractive target for reservoir elimination. Compound screens for latency reversal should factor in the complexity of their effects on ncRNAs.

MicroRNAs and long non-coding RNAs during transcriptional regulation and latency of HIV and HTLV

Human immunodeficiency virus (HIV) and human T cell leukemia virus (HTLV) have replicative and latent stages of infection. The status of the viruses is dependent on the cells that harbour them and on different events that change the transcriptional and post-transcriptional events. Non-coding (nc)RNAs are key factors in the regulation of retrovirus replication cycles. Notably, micro (mi)RNAs and long non-coding (lnc)RNAs are important regulators that can induce switches between active transcription-replication and latency of retroviruses and have important impacts on their pathogenesis. Here, we review the functions of miRNAs and lncRNAs in the context of HIV and HTLV. We describe how specific miRNAs and lncRNAs are involved in the regulation of the viruses' transcription, post-transcriptional regulation and latency. We further discuss treatment strategies using ncRNAs for HIV and HTLV long remission, reactivation or possible cure.

Action mechanisms and characteristics of miRNAs to regulate virus replication

MicroRNAs (miRNAs) have the potential to be explored as antiviral products. It is known that miRNAs have different kinds of target mRNAs and different target sites in mRNAs, and that the action-modes of miRNAs at different target sites may be different. But there is no evidence demonstrating the significance of the differences for the regulation of viruses by miRNAs, which might be crucial for the exploration of miRNA-based antiviral products. Here the experimental studies about the antiviral effects of miRNAs, with validated target mRNAs and target sites in the mRNAs, were systematically collected, based on which the mechanisms whereby miRNAs regulated virus replication were systematically reviewed. And miRNAs' down-regulation rates on target mRNAs and antiviral rates were compared among the miRNAs with different target sites, to analyze the characteristics of action-modes of miRNAs at different target sites during virus replication.

hsa-miR-181-5p inhibits human immunodeficiency virus type 1 replication by downregulating DDX3X expression

BACKGROUND

HIV-1 infection affects expression profiles of microRNA. miR-181 is found negatively correlated with HIV-1 viral load. This study aimed to explain that miR-181 targets DDX3X, a host factor involved in HIV-1 nuclear export, thereby inhibiting HIV-1 replication.

METHODS

To verify our hypothesis, first, the relationship between miR-181 expression, DDX3X expression, and HIV-1 viral load was analyzed. Second, miR-181 mimics were transfected into Jurkat cells infected with wild pNL4-3 strain or H9-IIIB cells with HIV-1 replication-competent for HIV-1 viral protein P24(Gag) detection. Besides the reporter gene plasmid containing the DDX3X mRNA sequence was transfected into 293T cells to demonstrate the targeting of miR-181 to the DDX3X mRNA. Finally, the spliced, unspliced, or incompletely spliced HIV-1 transcripts and HIV-1 Tat, Rev, and Gag mRNA were also detected after miR-181 transfection.

RESULTS

Our result proved that miR-181 significantly reduced the HIV-1 viral protein Gag(P24) level and targeted DDX3X mRNA 3'-UTR, inhibiting the unspliced or incompletely spliced HIV-1 mRNA's nuclear export.

CONCLUSION

Our results confirmed that miR-181 is involved in HIV-1 viral replication in lymphocytes by downregulating DDX3X expression. The research provides a research basis for future HIV-1 antiviral research.

In silico interrogation of the miRNAome of infected hematopoietic cells to predict processes important for human cytomegalovirus latent infection

Human cytomegalovirus (HCMV) latency in CD34+ progenitor cells is the outcome of a complex and continued interaction of virus and host that is initiated during very early stages of infection and reflects pro- and anti-viral activity. We hypothesized that a key event during early infection could involve changes to host miRNAs, allowing for rapid modulation of the host proteome. Here, we identify 72 significantly upregulated miRNAs and three that were downregulated by 6hpi of infection of CD34+ cells which were then subject to multiple in silico analyses to identify potential genes and pathways important for viral infection. The analyses focused on the upregulated miRNAs and were used to predict potential gene hubs or common mRNA targets of multiple miRNAs. Constitutive deletion of one target, the transcriptional regulator JDP2, resulted in a defect in latent infection of myeloid cells; interestingly, transient knockdown in differentiated dendritic cells resulted in increased viral lytic IE gene expression, arguing for subtle differences in the role of JDP2 during latency establishment and reactivation of HCMV. Finally, in silico predictions identified clusters of genes with related functions (such as calcium signaling, ubiquitination, and chromatin modification), suggesting potential importance in latency and reactivation. Consistent with this hypothesis, we demonstrate that viral IE gene expression is sensitive to calcium channel inhibition in reactivating dendritic cells. In conclusion, we demonstrate HCMV alters the miRNAome rapidly upon infection and that in silico interrogation of these changes reveals new insight into mechanisms controlling viral gene expression during HCMV latency and, intriguingly, reactivation.

The Synthetic Opioid Fentanyl Increases HIV Replication and Chemokine Co-Receptor Expression in Lymphocyte Cell Lines

BACKGROUND

In the United States, the illicit use of synthetic opioids such as fentanyl has led to a serious public health crisis. Synthetic opioids are known to enhance viral replication and to suppress immunologic responses, but their effects on HIV pathogenesis remain unclear. Thus, we examined the impact of fentanyl on HIV-susceptible and HIV-infected cell types.

METHODS

TZM-bl and HIV-infected lymphocyte cells were incubated with fentanyl at varying concentrations. Expression levels of the CXCR4 and CCR5 chemokine receptors and HIV p24 antigen were quantified with ELISA. HIV proviral DNA was quantified using SYBR RT-PCR. Cell viability was detected with the MTT assay. RNAseq was performed to characterize cellular gene regulation in the presence of fentanyl.

RESULTS

Fentanyl enhanced expression of both chemokine receptor levels in a dose-dependent manner in HIV-susceptible and infected cell lines. Similarly, fentanyl induced viral expression in HIV-exposed TZM-bl cells and in HIV-infected lymphocyte cell lines. Multiple genes associated with apoptosis, antiviral/interferon response, chemokine signaling, and NFκB signaling were differentially regulated.

CONCLUSIONS

Synthetic opioid fentanyl impacts HIV replication and chemokine co-receptor expression. Increased virus levels suggest that opioid use may increase the likelihood of transmission and accelerate disease progression.

Mapping CircRNA-miRNA-mRNA regulatory axis identifies hsa_circ_0080942 and hsa_circ_0080135 as a potential theranostic agents for SARS-CoV-2 infection

Non-coding RNAs (ncRNAs) can control the flux of genetic information; affect RNA stability and play crucial roles in mediating epigenetic modifications. A number of studies have highlighted the potential roles of both virus-encoded and host-encoded ncRNAs in viral infections, transmission and therapeutics. However, the role of an emerging type of non-coding transcript, circular RNA (circRNA) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has not been fully elucidated so far. Moreover, the potential pathogenic role of circRNA-miRNA-mRNA regulatory axis has not been fully explored as yet. The current study aimed to holistically map the regulatory networks driven by SARS-CoV-2 related circRNAs, miRNAs and mRNAs to uncover plausible interactions and interplay amongst them in order to explore possible therapeutic options in SARS-CoV-2 infection. Patient datasets were analyzed systematically in a unified approach to explore circRNA, miRNA, and mRNA expression profiles. CircRNA-miRNA-mRNA network was constructed based on cytokine storm related circRNAs forming a total of 165 circRNA-miRNA-mRNA pairs. This study implies the potential regulatory role of the obtained circRNA-miRNA-mRNA network and proposes that two differentially expressed circRNAs hsa_circ_0080942 and hsa_circ_0080135 might serve as a potential theranostic agents for SARS-CoV-2 infection. Collectively, the results shed light on the functional role of circRNAs as ceRNAs to sponge miRNA and regulate mRNA expression during SARS-CoV-2 infection.

An Evaluation on the Role of Non-Coding RNA in HIV Transcription and Latency: A Review

The existence of latent cellular reservoirs is recognized as the major barrier to an HIV cure. Reactivating and eliminating "shock and kill" or permanently silencing "block and lock" the latent HIV reservoir, as well as gene editing, remain promising approaches, but so far have proven to be only partially successful. Moreover, using latency reversing agents or "block and lock" drugs pose additional considerations, including the ability to cause cellular toxicity, a potential lack of specificity for HIV, or low potency when each agent is used alone. RNA molecules, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are becoming increasingly recognized as important regulators of gene expression. RNA-based approaches for combatting HIV latency represent a promising strategy since both miRNAs and lncRNAs are more cell-type and tissue specific than protein coding genes. Thus, a higher specificity of targeting the latent HIV reservoir with less overall cellular toxicity can likely be achieved. In this review, we summarize current knowledge about HIV gene expression regulation by miRNAs and lncRNAs encoded in the human genome, as well as regulatory molecules encoded in the HIV genome. We discuss both the transcriptional and post-transcriptional regulation of HIV gene expression to align with the current definition of latency, and describe RNA molecules that either promote HIV latency or have anti-latency properties. Finally, we provide perspectives on using each class of RNAs as potential targets for combatting HIV latency, and describe the complexity of the interactions between different RNA molecules, their protein targets, and HIV.

Overview of the role and action mechanism of microRNA-128 in viral infections

Recently in vivo and in vitro studies have provided evidence establishing the significance of microRNAs (miRNAs) in both physiological and pathological conditions. In this regard, the role of miRNA-128 (miR-128) in health and diseases has been found, and its critical regulatory role in the context of some viral diseases has been recently identified. For instance, it has been found that miR-128 can serve as an antiviral mediator and significantly limit the replication and dissemination of human immunodeficiency virus type 1 (HIV-1). Besides, it has been noted that poliovirus receptor-related 4 (PVRL4) is post-transcriptionally regulated by miR-128, representing possible miRNA targets that can modulate measles virus infection. Of note, the downregulation of seminal exosomes eca-miR-128 is associated with the long-term persistence of Equine arteritis virus (EAV) in the reproductive tract, and this particular miRNA is a putative regulator of chemokine ligand 16 (C-X-C motif) as determined by target prediction analysis. In this review, the latest information on the role and action mechanism of miR-128 in viral infections will be summarized and discussed in detail.

The diverse roles of miRNAs in HIV pathogenesis: Current understanding and future perspectives

Despite noteworthy progress made in the management and treatment of HIV/AIDS-related disease, including the introduction of the now almost ubiquitous HAART, there remains much to understand with respect to HIV infection. Although some roles that miRNAs play in some diseases have become more obvious of late, the roles of miRNAs in the context of HIV pathogenesis have not, as yet, been elucidated, and require further investigations. miRNAs can either be beneficial or harmful to the host, depending upon the genes they target. Some miRNAs target the 3' UTR of viral mRNAs to accomplish restriction of viral infection. However, upon HIV-1 infection, there are several dysregulated host miRNAs which target their respective host factors to either facilitate or abrogate viral infection. In this review, we discuss the miRNAs which play roles in various aspects of viral pathogenesis. We describe in detail the various mechanisms thereby miRNAs either directly or indirectly regulate HIV-1 infection. Moreover, the predictive roles of miRNAs in various aspects of the HIV viral life cycle are also discussed. Contemporary antiretroviral therapeutic drugs have received much attention recently, due to their success in the treatment of HIV/AIDS; therefore, miRNA involvement in various aspects of antiretroviral therapeutics are also elaborated upon herein. The therapeutic potential of miRNAs are discussed, and we also propose herein that the therapeutic potential of one specific miRNA, miR-34a, warrants further exploration, as this miRNA is known to target three host proteins to promote HIV-1 pathogenesis. Finally, future perspectives and some controversy around the expression of miRNAs by HIV-1 are also discussed.

Cytosolic DNA sensor activation inhibits HIV infection of macrophages

Cytosolic recognition of microbial DNA in macrophages results in the activation of the interferon (IFN)-dependent antiviral innate immunity. Here, we examined whether activating DNA sensors in peripheral blood monocyte-derived macrophages (MDMs) can inhibit human immunodeficiency virus (HIV). We observed that the stimulation of MDMs with poly(dA:dT) or poly(dG:dC) (synthetic ligands for the DNA sensors) inhibited HIV infection and replication. MDMs treated with poly(dA:dT) or poly(dG:dC) expressed higher levels of both type I and type III IFNs than untreated cells. Activation of the DNA sensors in MDMs also induced the expression of the multiple intracellular anti-HIV factors, including IFN-stimulated genes (ISGs: ISG15, ISG56, Viperin, OAS2, GBP5, MxB, and Tetherin) and the HIV restriction microRNAs (miR-29c, miR-138, miR-146a, miR-155, miR-198, and miR-223). In addition, the DNA sensor activation of MDM upregulated the expression of the CC chemokines (RANTES, MIP-1α, MIP-1β), the ligands for HIV entry coreceptor CCR5. These observations indicate that the cytosolic DNA sensors have a protective role in the macrophage intracellular immunity against HIV and that targeting the DNA sensors has therapeutic potential for immune activation-based anti-HIV treatment.

Forging a Functional Cure for HIV: Transcription Regulators and Inhibitors

Current antiretroviral therapy (ART) increases the survival of HIV-infected individuals, yet it is not curative. The major barrier to finding a definitive cure for HIV is our inability to identify and eliminate long-lived cells containing the dormant provirus, termed viral reservoir. When ART is interrupted, the viral reservoir ensures heterogenous and stochastic HIV viral gene expression, which can reseed infection back to pre-ART levels. While strategies to permanently eradicate the virus have not yet provided significant success, recent work has focused on the management of this residual viral reservoir to effectively limit comorbidities associated with the ongoing viral transcription still observed during suppressive ART, as well as limit the need for daily ART. Our group has been at the forefront of exploring the viability of the block-and-lock remission approach, focused on the long-lasting epigenetic block of viral transcription such that without daily ART, there is no risk of viral rebound, transmission, or progression to AIDS. Numerous studies have reported inhibitors of both viral and host factors required for HIV transcriptional activation. Here, we highlight and review some of the latest HIV transcriptional inhibitor discoveries that may be leveraged for the clinical exploration of block-and-lock and revolutionize the way we treat HIV infections.

P-TEFb is degraded by Siah1/2 in quiescent cells

P-TEFb, composed of CycT1 and CDK9, regulates the elongation of transcription by RNA polymerase II. In proliferating cells, it is regulated by 7SK snRNA in the 7SK snRNP complex. In resting cells, P-TEFb is absent, because CycT1 is dephosphorylated, released from CDK9 and rapidly degraded. In this study, we identified the mechanism of this degradation. We mapped the ubiquitination and degradation of free CycT1 to its N-terminal region from positions 1 to 280. This region is ubiquitinated at six lysines, where E3 ligases Siah1 and Siah2 bind and degrade these sequences. Importantly, the inhibition of Siah1/2 rescued the expression of free CycT1 in proliferating as well as resting primary cells. We conclude that Siah1/2 are the E3 ligases that bind and degrade the dissociated CycT1 in resting, terminally differentiated, anergic and/or exhausted cells.

The Effect of miRNA Gene Regulation on HIV Disease

Over many years, research on HIV/AIDS has advanced with the introduction of HAART. Despite these advancements, significant gaps remain with respect to aspects in HIV life cycle, with specific attention to virus-host interactions. Investigating virus-host interactions may lead to the implementation of novel therapeutic strategies against HIV/AIDS. Notably, host gene silencing can be facilitated by cellular small non-coding RNAs such as microRNAs paving the way for epigenetic anti-viral therapies. Numerous studies have elucidated the importance of microRNAs in HIV pathogenesis. Some microRNAs can either promote viral infection, while others can be detrimental to viral replication. This is accomplished by targeting the HIV-proviral genome or by regulating host genes required for viral replication and immune responses. In this review, we report on 1) the direct association of microRNAs with HIV infection; 2) the indirect association of known human genetic factors with HIV infection; 3) the regulation of human genes by microRNAs in other diseases that can be explored experimentally to determine their effect on HIV-1 infection; and 4) therapeutic interactions of microRNA against HIV infection.

Insights Into Persistent HIV-1 Infection and Functional Cure: Novel Capabilities and Strategies

Although HIV-1 replication can be efficiently suppressed to undetectable levels in peripheral blood by combination antiretroviral therapy (cART), lifelong medication is still required in people living with HIV (PLWH). Life expectancies have been extended by cART, but age-related comorbidities have increased which are associated with heavy physiological and economic burdens on PLWH. The obstacle to a functional HIV cure can be ascribed to the formation of latent reservoir establishment at the time of acute infection that persists during cART. Recent studies suggest that some HIV reservoirs are established in the early acute stages of HIV infection within multiple immune cells that are gradually shaped by various host and viral mechanisms and may undergo clonal expansion. Early cART initiation has been shown to reduce the reservoir size in HIV-infected individuals. Memory CD4+ T cell subsets are regarded as the predominant cellular compartment of the HIV reservoir, but monocytes and derivative macrophages or dendritic cells also play a role in the persistent virus infection. HIV latency is regulated at multiple molecular levels in transcriptional and post-transcriptional processes. Epigenetic regulation of the proviral promoter can profoundly regulate the viral transcription. In addition, transcriptional elongation, RNA splicing, and nuclear export pathways are also involved in maintaining HIV latency. Although most proviruses contain large internal deletions, some defective proviruses may induce immune activation by expressing viral proteins or producing replication-defective viral-like particles. In this review article, we discuss the state of the art on mechanisms of virus persistence in the periphery and tissue and summarize interdisciplinary approaches toward a functional HIV cure, including novel capabilities and strategies to measure and eliminate the infected reservoirs and induce immune control.

Stem Cell-Derived Exosome as Potential Therapeutics for Microbial Diseases

Exosomes, as the smallest extracellular vesicles that carry a cargo of nucleic acids, lipids, and proteins and mediate intercellular communication, have attracted much attention in diagnosis and treatment in the field of medicine. The contents of exosomes vary depending on the cell type and physiological conditions. Among exosomes derived from several cell types, stem cell-derived exosomes (stem cell-Exo) are increasingly being explored due to their immunomodulatory properties, regenerative capacity, anti-inflammatory and anti-microbial functions. Administration of stem cell-Exo, as a cell-free therapy for various diseases, has gained great promise. Indeed, the advantages of exosomes secreted from stem cells outweigh those of their parent cells owing to their small size, high stability, less immunogenicity, no risk of tumorigenesis, and easier condition for storage. Recently, the use of stem cell-Exo has been proposed in the field of microbial diseases. Pathogens including bacteria, viruses, fungi, and parasites can cause various diseases in humans with acute and chronic complications, sometimes resulting in mortality. On the other hand, treatments based on antibiotics and other chemical compounds have many side effects and the strains become resistant to drugs in some cases. Hence, this review aimed to highlight the effect of stem cell-derived extracellular vesicles including stem cell-Exo on microbial diseases. Although most published studies are preclinical, the avenue of clinical application of stem cell-Exo is under way to reach clinical applications. The challenges ahead of this cell-free treatment that might be applied as a therapeutic alternative to stem cells for translation from bench to bed were emphasized, as well.

Integrated miRNA and mRNA Expression Profiles Reveal Differentially Expressed miR-222a as an Antiviral Factor Against Duck Hepatitis A Virus Type 1 Infection

Duck hepatitis A virus 1 (DHAV-1) is a highly contagious etiological agent that causes acute hepatitis in young ducklings. MicroRNAs (miRNAs) play important regulatory roles in response to pathogens. However, the interplay between DHAV-1 infection and miRNAs remains ambiguous. We characterized and compared miRNA and mRNA expression profiles in duck embryo fibroblasts cells (DEFs) infected with DHAV-1. In total, 36 and 96 differentially expressed (DE) miRNAs, and 4110 and 2595 DE mRNAs, were identified at 12 and 24 h after infection. In particular, 126 and 275 miRNA-mRNA pairs with a negative correlation were chosen to construct an interaction network. Subsequently, we identified the functional annotation of DE mRNAs and target genes of DE miRNAs enriched in diverse Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which may be important for virus resistance, cell proliferation, and metabolism. Moreover, upregulated miR-222a could negatively regulate DHAV-1 replication in DEFs and downregulate integrin subunit beta 3 (ITGB3) expression by targeting the 3' untranslated region (3'UTR), indicating that miR-222a may modulate DHAV-1 replication via interaction with ITGB3. In conclusion, the results reveal changes of mRNAs and miRNAs during DHAV-1 infection and suggest miR-222a as an antiviral factor against DHAV-1.

Persistent Inflammation and Non-AIDS Comorbidities During ART: Coming of the Age of Monocytes

Monocytes are innate immune cells that serve as the first line of defense against pathogens by engulfing and destroying pathogens or by processing and presenting antigens to initiate adaptive immunity and stimulate immunological responses. Monocytes are classified into three types: classical, intermediate, and non-classical monocytes, each of which plays a particular function in response to pathogens. Human immunodeficiency virus type 1 (HIV-1) infection disrupts the balance of monocyte subsets, and the quantity and function of monocytes will not fully recover even with long-term antiretroviral therapy (ART). Monocytes are vital for the establishment and maintenance of HIV-1 latent viral reservoirs and are closely related to immune dysfunction even after ART. Therefore, the present review focuses on the phenotypic function of monocytes and their functions in HIV-1 infection to elucidate their roles in HIV patients.

Emerging role and function of miR-198 in human health and diseases

Ever since their discovery, microRNAs (miRNAs/miRs) have astonished us by the plethora of processes they regulate, and thus adding another dimension to the gene regulation. They have been implicated in several diseases affecting cardiovascular, neurodegenerative, hepatic, autoimmune and inflammatory functions. A primate specific exonic miRNA, miR-198 has been vastly studied during the past decade, and shown to have a critical role in wound healing. The aberrant expression of miR-198 was first reported in schizophrenia, linking it to neural development. Later, its dysregulation and tumor suppressive role was reported in hepatocellular carcinoma. However, this was just a beginning, and after which there was an explosion of reports linking miR-198 deregulation to cancers and other ailments. The first target to be identified for miR-198 was Cyclin T1 in monocytes affecting HIV1 replication. Depending on the type of cancer, miR-198 has been shown to function either as a tumor suppressor or an oncomir. Interestingly, miR-198 is not only known to regulate multiple targets and pathways, but also is itself regulated by several circular RNAs and long-non-coding RNAs, highlighting a complex regulatory network. This review highlights the currently understood mechanism and regulation of miR-198 in different diseases, and its possible diagnostic and therapeutic potential.

Reversible phosphorylation of cyclin T1 promotes assembly and stability of P-TEFb

The positive transcription elongation factor b (P-TEFb) is a critical coactivator for transcription of most cellular and viral genes, including those of HIV. While P-TEFb is regulated by 7SK snRNA in proliferating cells, P-TEFb is absent due to diminished levels of CycT1 in quiescent and terminally differentiated cells, which has remained unexplored. In these cells, we found that CycT1 not bound to CDK9 is rapidly degraded. Moreover, productive CycT1:CDK9 interactions are increased by PKC-mediated phosphorylation of CycT1 in human cells. Conversely, dephosphorylation of CycT1 by PP1 reverses this process. Thus, PKC inhibitors or removal of PKC by chronic activation results in P-TEFb disassembly and CycT1 degradation. This finding not only recapitulates P-TEFb depletion in resting CD4+ T cells but also in anergic T cells. Importantly, our studies reveal mechanisms of P-TEFb inactivation underlying T cell quiescence, anergy, and exhaustion as well as proviral latency and terminally differentiated cells.

Hsa-miR-31 Governs T-Cell Homeostasis in HIV Protection via IFN-γ-Stat1-T-Bet Axis

It remains poorly defined whether any human miRNAs play protective roles during HIV infection. Here, focusing on a unique cohort of HIV-infected former blood donors, we identified miR-31 (hsa-miR-31) by comparative miRNA profiling as the only miRNA inversely correlating with disease progression. We further validated this association in two prospective cohort studies. Despite conservation during evolution, hsa-miR-31, unlike its mouse counterpart (mmu-miR-31), was downregulated in human T cell upon activation. Our ex vivo studies showed that inhibiting miR-31 in naïve CD4+ T cells promoted a transcriptional profile with activation signature. Consistent with this skewing effect, miR-31 inhibition led to remarkably increased susceptibility to HIV infection. The suppressive nature of miR-31 in CD4+ T cell activation was pinpointed to its ability to decrease T-bet, the key molecule governing IFN-γ production and activation of CD4+ T cells, by directly targeting the upstream STAT1 transcriptional factor for downregulation, thus blunting Th1 response. Our results implicated miR-31 as a useful biomarker for tracking HIV disease progression and, by demonstrating its importance in tuning the activation of CD4+ T cells, suggested that miR-31 may play critical roles in other physiological contexts where the CD4+ T cell homeostasis needs to be deliberately controlled.

Induction of Autophagy to Achieve a Human Immunodeficiency Virus Type 1 Cure

Effective antiretroviral therapy has led to significant human immunodeficiency virus type 1 (HIV-1) suppression and improvement in immune function. However, the persistence of integrated proviral DNA in latently infected reservoir cells, which drive viral rebound post-interruption of antiretroviral therapy, remains the major roadblock to a cure. Therefore, the targeted elimination or permanent silencing of this latently infected reservoir is a major focus of HIV-1 research. The most studied approach in the development of a cure is the activation of HIV-1 expression to expose latently infected cells for immune clearance while inducing HIV-1 cytotoxicity—the “kick and kill” approach. However, the complex and highly heterogeneous nature of the latent reservoir, combined with the failure of clinical trials to reduce the reservoir size casts doubt on the feasibility of this approach. This concern that total elimination of HIV-1 from the body may not be possible has led to increased emphasis on a “functional cure” where the virus remains but is unable to reactivate which presents the challenge of permanently silencing transcription of HIV-1 for prolonged drug-free remission—a “block and lock” approach. In this review, we discuss the interaction of HIV-1 and autophagy, and the exploitation of autophagy to kill selectively HIV-1 latently infected cells as part of a cure strategy. The cure strategy proposed has the advantage of significantly decreasing the size of the HIV-1 reservoir that can contribute to a functional cure and when optimised has the potential to eradicate completely HIV-1.

The Involvement of MicroRNAs in SARS-CoV-2 Infection Comorbid with HIV-Associated Preeclampsia

Purpose of Review

This review investigated the potential role of microRNAs (miRNAs) in the synergy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, preeclampsia (PE), and human immunodeficiency virus (HIV) infection. Maternal health is a great concern when treating pregnant women fighting this triad of diseases, which is highly prevalent in South Africa. MicroRNAs are involved in fine-tuning of physiological processes. Disruptions to the balance of this minute protein can lead to various physiological changes that are sometimes pathological.

Recent Findings

MicroRNAs have recently been implicated in PE and have been linked to the anti-angiogenic imbalance evident in PE. Recent in silico studies have identified potential host miRNAs with anti-viral properties against SARS-CoV-2 infection. Studies have demonstrated dysregulated expression of several miRNAs in HIV-1 infection along with the ability of HIV-1 to downregulate anti-viral host microRNAs.

Summary

This review has highlighted the significant gap in literature on the potential of miRNAs in women with HIV-associated PE in synergy with the novel SARS-CoV-2 infection. In addition, this review has provided evidence of the critical role that the epigenetic regulatory mechanism of miRNA plays in viral infections and PE, thereby providing a foundation for further research investigating the potential of therapeutic miRNA development with fewer side-effects for pregnant women.

Combinatorial Use of Both Epigenetic and Non-Epigenetic Mechanisms to Efficiently Reactivate HIV Latency

The persistence of latent HIV provirus pools in different resting CD4+ cell subsets remains the greatest obstacle in the current efforts to treat and cure HIV infection. Recent efforts to purge out latently infected memory CD4+ T-cells using latency-reversing agents have failed in clinical trials. This review discusses the epigenetic and non-epigenetic mechanisms of HIV latency control, major limitations of the current approaches of using latency-reversing agents to reactivate HIV latency in resting CD4+ T-cells, and potential solutions to these limitations.

hsa-miR-191-5p inhibits replication of human immunodeficiency virus type 1 by downregulating the expression of NUP50

MicroRNAs (miRNAs) are important host molecules involved in human immunodeficiency virus type 1 (HIV-1) infection. Antiretroviral therapy (ART) can affect the miRNA expression profile, but differentially expressed miRNAs still remain to be identified. In this study, we used gene chips to analyze miRNA expression profiles in peripheral blood mononuclear cells from ART-naive HIV-1 patients and those receiving ART, as well as from uninfected individuals. We measured differences in miRNA expression by quantitative polymerase chain reaction (qPCR) in an expanded sample. We found significant differences in the expression of has-miR-191-5p among the three groups (P < 0.05). Furthermore, we showed that hsa-miR-191-5p has an inhibitory effect on HIV-1 replication in cell models in vitro. We identified CCR1 and NUP50 as target molecules of hsa-miR-191-5p and found that hsa-miR-191-5p inhibits the expression of CCR1 and NUP50. Knockdown of NUP50 resulted in significant inhibition of HIV-1 replication. In summary, our research shows that hsa-miR-191-5p expression is reduced in HIV-1-infected patients and acts an inhibitor of HIV-1 infection via a mechanism that may involve targeted repression of NUP50 expression.

HIV replication and latency in monocytes and macrophages

The relevance of monocyte and macrophage reservoirs in virally suppressed people with HIV (vsPWH) has previously been debatable. Macrophages were assumed to have a moderate life span and lack self-renewing potential. However, recent studies have challenged this dogma and now suggest an important role of these cell as long-lived HIV reservoirs. Lentiviruses have a long-documented association with macrophages and abundant evidence exists that macrophages are important target cells for HIV in vivo. A critical understanding of HIV infection, replication, and latency in macrophages is needed in order to determine the appropriate method of measuring and eliminating this cellular reservoir. This review provides a brief discussion of the biology and acute and chronic infection of monocytes and macrophages, with a more substantial focus on replication, latency and measurement of the reservoir in cells of myeloid origin.

Block-And-Lock: New Horizons for a Cure for HIV-1

HIV-1/AIDS remains a global public health problem. The world health organization (WHO) reported at the end of 2019 that 38 million people were living with HIV-1 worldwide, of which only 67% were accessing antiretroviral therapy (ART). Despite great success in the clinical management of HIV-1 infection, ART does not eliminate the virus from the host genome. Instead, HIV-1 remains latent as a viral reservoir in any tissue containing resting memory CD4⁺ T cells. The elimination of these residual proviruses that can reseed full-blown infection upon treatment interruption remains the major barrier towards curing HIV-1. Novel approaches have recently been developed to excise or disrupt the virus from the host cells (e.g., gene editing with the CRISPR-Cas system) to permanently shut off transcription of the virus (block-and-lock and RNA interference strategies), or to reactivate the virus from cell reservoirs so that it can be eliminated by the immune system or cytopathic effects (shock-and-kill strategy). Here, we will review each of these approaches, with the major focus placed on the block-and-lock strategy.

miRNA profiling of primate cervicovaginal lavage and extracellular vesicles reveals miR-186-5p as a potential antiretroviral factor in macrophages

Cervicovaginal secretions, or their components collected, are referred to as cervicovaginal lavage (CVL). CVL constituents have utility as biomarkers and play protective roles in wound healing and against HIV-1 infection. However, several components of cervicovaginal fluids are less well understood, such as extracellular RNAs and their carriers, for example, extracellular vesicles (EVs). EVs comprise a wide array of double-leaflet membrane extracellular particles and range in diameter from 30 nm to over one micron. The aim of this study was to determine whether differentially regulated CVL microRNAs (miRNAs) might influence retrovirus replication. To this end, we characterized EVs and miRNAs of primate CVL during the menstrual cycle and simian immunodeficiency virus (SIV) infection of macaques. EVs were enriched by stepped ultracentrifugation, and miRNA profiles were assessed with a medium-throughput stem-loop/hydrolysis probe qPCR platform. Whereas hormone cycling was abnormal in infected subjects, EV concentration correlated with progesterone concentration in uninfected subjects. miRNAs were present predominantly in the EV-depleted CVL supernatant. Only a small number of CVL miRNAs changed during the menstrual cycle or SIV infection, for example, miR-186-5p, which was depleted in retroviral infection. This miRNA inhibited HIV replication in infected macrophages in vitro. In silico target prediction and pathway enrichment analyses shed light on the probable functions of miR-186-5p in hindering HIV infections via immunoregulation, T-cell regulation, disruption of viral pathways, etc. These results provide further evidence for the potential of EVs and small RNAs as biomarkers or effectors of disease processes in the reproductive tract.

Regulation of Expression and Latency in BLV and HTLV

Human T-lymphotrophic virus type 1 (HTLV-1) and Bovine leukemia virus (BLV) belong to the Deltaretrovirus genus. HTLV-1 is the etiologic agent of the highly aggressive and currently incurable cancer adult T-cell leukemia (ATL) and a neurological disease HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). BLV causes neoplastic proliferation of B cells in cattle: enzootic bovine leucosis (EBL). Despite the severity of these conditions, infection by HTLV-1 and BLV appear in most cases clinically asymptomatic. These viruses can undergo latency in their hosts. The silencing of proviral gene expression and maintenance of latency are central for the establishment of persistent infection, as well as for pathogenesis in vivo. In this review, we will present the mechanisms that control proviral activation and retroviral latency in deltaretroviruses, in comparison with other exogenous retroviruses. The 5′ long terminal repeats (5′-LTRs) play a main role in controlling viral gene expression. While the regulation of transcription initiation is a major mechanism of silencing, we discuss topics that include (i) the epigenetic control of the provirus, (ii) the cis-elements present in the LTR, (iii) enhancers with cell-type specific regulatory functions, (iv) the role of virally-encoded transactivator proteins, (v) the role of repressors in transcription and silencing, (vi) the effect of hormonal signaling, (vii) implications of LTR variability on transcription and latency, and (viii) the regulatory role of non-coding RNAs. Finally, we discuss how a better understanding of these mechanisms may allow for the development of more effective treatments against Deltaretroviruses.

Expression profiling of human milk derived exosomal microRNAs and their targets in HIV-1 infected mothers

Despite the use of antiretroviral therapy (ART) in HIV-1 infected mothers approximately 5% of new HIV-1 infections still occur in breastfed infants annually, which warrants for the development of novel strategies to prevent new HIV-1 infections in infants. Human milk (HM) exosomes are highly enriched in microRNAs (miRNAs), which play an important role in neonatal immunity. Furthermore, HM exosomes from healthy donors are known to inhibit HIV-1 infection and transmission; however, the effect of HIV-1 on HM exosomal miRNA signatures remains unknown. In this study, we used nCounter NanoString technology and investigated miRNAs expression profiles in first week postpartum HM exosomes from HIV-1 infected and uninfected control mothers (n = 36). Our results indicated that HIV-1 perturbed the differential expression patterns of 19 miRNAs (13 upregulated and 6 downregulated) in HIV-1 infected women compared to healthy controls. DIANA-miR functional pathway analyses revealed that multiple biological pathways are involved including cell cycle, pathways in cancer, TGF-β signaling, FoxO signaling, fatty acid biosynthesis, p53 signaling and apoptosis. Moreover, the receiver operating characteristics (ROC) curve analyses of miR-630 and miR-378g yielded areas under the ROC curves of 0.82 (95% CI 0.67 to 0.82) and 0.83 (95% CI 0.67 to 0.83), respectively highlighting their potential to serve as biomarkers to identify HIV-1 infection in women. These data may contribute to the development of new therapeutic strategies in prevention of mother-to-child transmission (MTCT) of HIV-1.

MicroRNAs and exosomes: key players in HIV pathogenesis

OBJECTIVES

HIV infection is well known to cause impairment of the human immune system, and until recently was a leading cause of death. It has been shown that T lymphocytes are the main targets of HIV. The virus inactivates T lymphocytes by interfering with a wide range of cellular and molecular targets, leading to suppression of the immune system. The objective of this review is to investigate to what extent microRNAs (miRNAs) are involved in HIV pathogenesis.

METHODS

The scientific literature (Pubmed and Google scholar) for the period 1988-2019 was searched.

RESULTS

Mounting evidence has revealed that miRNAs are involved in viral replication and immune response, whether by direct targeting of viral transcripts or through indirect modulation of virus-related host pathways. In addition, exosomes have been found to act as nanoscale carriers involved in HIV pathogenesis. These nanovehicles target their cargos (i.e. DNA, RNA, viral proteins and miRNAs) leading to alteration of the behaviour of recipient cells.

CONCLUSIONS

miRNAs and exosomes are important players in HIV pathogenesis. Additionally, there are potential diagnostic applications of miRNAs as biomarkers in HIV infection.

Genetic and epigenetic regulation of natural resistance to HIV-1 infection: new approaches to unveil the HESN secret

Introduction: Since the identification of HIV, several studies reported the unusual case of small groups of subjects showing natural resistance to HIV infection. These subjects are referred to as HIV-1-exposed seronegative (HESN) individuals and include people located in different areas, with diverse ethnic backgrounds and routes of exposure. The mechanism/s responsible for protection from infection in HESN individuals are basically indefinite and most likely are multifactorial.Areas covered: Host factors, including genetic background as well as natural and acquired immunity, have all been associated with this phenomenon. Recently, epigenetic factors have been investigated as possible determinants of reduced susceptibility to HIV infection. With the advent of the OMICS era, the availability of techniques such as GWAS, RNAseq, and exome-sequencing in both bulk cell populations and single cells will likely lead to great strides in the understanding of the HESN mystery.Expert opinion: The employment of increasingly sophisticated techniques is allowing the gathering of enormous amounts of data. The integration of such information will provide important hints that could lead to the identification of viral and host correlates of protection against HIV infection, allowing the development of more effective preventative and therapeutic regimens.

Current Status of Latency Reversing Agents Facing the Heterogeneity of HIV-1 Cellular and Tissue Reservoirs

One of the most explored therapeutic approaches aimed at eradicating HIV-1 reservoirs is the "shock and kill" strategy which is based on HIV-1 reactivation in latently-infected cells ("shock" phase) while maintaining antiretroviral therapy (ART) in order to prevent spreading of the infection by the neosynthesized virus. This kind of strategy allows for the "kill" phase, during which latently-infected cells die from viral cytopathic effects or from host cytolytic effector mechanisms following viral reactivation. Several latency reversing agents (LRAs) with distinct mechanistic classes have been characterized to reactivate HIV-1 viral gene expression. Some LRAs have been tested in terms of their potential to purge latent HIV-1 in vivo in clinical trials, showing that reversing HIV-1 latency is possible. However, LRAs alone have failed to reduce the size of the viral reservoirs. Together with the inability of the immune system to clear the LRA-activated reservoirs and the lack of specificity of these LRAs, the heterogeneity of the reservoirs largely contributes to the limited success of clinical trials using LRAs. Indeed, HIV-1 latency is established in numerous cell types that are characterized by distinct phenotypes and metabolic properties, and these are influenced by patient history. Hence, the silencing mechanisms of HIV-1 gene expression in these cellular and tissue reservoirs need to be better understood to rationally improve this cure strategy and hopefully reach clinical success.

Host microRNAs and exosomes that modulate influenza virus infection

MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate over half of human protein-coding genes and play a vital role in cellular development, proliferation, metabolism, and homeostasis. Exosomes are rounded or cup-like extracellular vesicles that carry proteins, mRNAs, miRNAs, and lipids for release and exchange messages between cells involved in various cellular processes. Influenza virus is a substantial public health challenge. The expression of host miRNAs is altered in response to stimulation by influenza virus. These dysregulated miRNAs directly or indirectly target viral genes to regulate viral replication and stimulate or suppress innate immune responses and cell apoptosis during viral infection. Exosomes released by infected cells are associated with the transfer of antigens and key molecules that activate and modulate immune function. Dysregulation of miRNAs and secretion of exosomes are associated with pathogenicity and immune regulation during influenza infection. This review provides a comprehensive summary of the information available regarding host miRNAs and exosomes that are involved in the modulation of influenza virus infection and will facilitate the development of preventative or therapeutic strategies against influenza virus.

The Role of Macrophages in HIV-1 Persistence and Pathogenesis

Current antiretroviral therapy (ART) effectively suppresses Human Immunodeficiency Virus type 1 (HIV-1) in infected individuals. However, even long term ART does not eradicate HIV-1 infected cells and the virus persists in cellular reservoirs. Beside memory CD4⁺ T cells, cells of the myeloid lineage, especially macrophages, are believed to be an important sanctuary for HIV-1. Monocytes and macrophages are key players in the innate immune response to pathogens and are recruited to sites of infection and inflammation. Due to their long life span and ability to reside in virtually every tissue, macrophages have been proposed to play a critical role in the establishment and persistence of the HIV-1 reservoir. Current HIV-1 cure strategies mainly focus on the concept of “shock and kill” to purge the viral reservoir. This approach aims to reactivate viral protein production in latently infected cells, which subsequently are eliminated as a consequence of viral replication, or recognized and killed by the immune system. Macrophage susceptibility to HIV-1 infection is dependent on the local microenvironment, suggesting that molecular pathways directing differentiation and polarization are involved. Current latency reversing agents (LRA) are mainly designed to reactivate the HIV-1 provirus in CD4+ T cells, while their ability to abolish viral latency in macrophages is largely unknown. Moreover, the resistance of macrophages to HIV-1 mediated kill and the presence of infected macrophages in immune privileged regions including the central nervous system (CNS), may pose a barrier to elimination of infected cells by current “shock and kill” strategies. This review focusses on the role of monocytes/macrophages in HIV-1 persistence. We will discuss mechanisms of viral latency and persistence in monocytes/macrophages. Furthermore, the role of these cells in HIV-1 tissue distribution and pathogenesis will be discussed.

Morphine Withdrawal Enhances HIV Infection of Macrophages

Opioid withdrawal recurs at high rates in opioid use disorder and compromises the immune system. In general, there are two types of opioid withdrawal: abrupt withdrawal (AW) and precipitated withdrawal (PW). In this study, we examined the effect of morphine AW or morphine PW on HIV infection of human blood monocyte-derived macrophages. We observed that both morphine AW and PW enhanced the susceptibility of macrophages to HIV infection. In addition, both AW and PW activated HIV replication in the latently infected myeloid cells (U1 and OM10.1). Investigation of mechanisms responsible for these observations showed that both AW and PW could inhibit the expression of multiple intracellular HIV inhibitory factors, including APOBE3G/F, SAMHD1, MX2, and HIV restriction microRNAs (miR-28, miR-125b, and miR-150) in macrophages. These findings provide additional evidence to support the notion that opioid use compromises the intracellular anti-HIV immunity and facilitates HIV infection and persistence in macrophages.

Epigenetic regulation of macrophages: from homeostasis maintenance to host defense

Macrophages are crucial members of the innate immune response and important regulators. The differentiation and activation of macrophages require the timely regulation of gene expression, which depends on the interaction of a variety of factors, including transcription factors and epigenetic modifications. Epigenetic changes also give macrophages the ability to switch rapidly between cellular programs, indicating the ability of epigenetic mechanisms to affect phenotype plasticity. In this review, we focus on key epigenetic events associated with macrophage fate, highlighting events related to the maintenance of tissue homeostasis, responses to different stimuli and the formation of innate immune memory. Further understanding of the epigenetic regulation of macrophages will be helpful for maintaining tissue integrity, preventing chronic inflammatory diseases and developing therapies to enhance host defense.

Targeting HIV-1 proviral transcription

Despite the success of antiretroviral therapies, there is no cure for HIV-1 infection due to the establishment of a long-lived latent reservoir that fuels viral rebound upon treatment interruption. 'Shock-and-kill' strategies to diminish the latent reservoir have had modest impact on the reservoir leading to considerations of alternative approaches to target HIV-1 proviruses. This review explores approaches to target HIV-1 transcription as a way to block the provirus expression.

Interferon-Inducible MicroRNA miR-128 Modulates HIV-1 Replication by Targeting TNPO3 mRNA

The HIV/AIDS pandemic remains an important threat to human health. We have recently demonstrated that a novel microRNA (miR), miR-128, represses retrotransposon long interspaced element 1 (L1) by a dual mechanism, namely, by directly targeting the coding region of the L1 RNA and by repressing a required nuclear import factor (TNPO1). We have further determined that miR-128 represses the expression of all three TNPO proteins (transportins TNPO1, TNPO2, and TNPO3). Here, we establish that miR-128 also influences HIV-1 replication by repressing TNPO3, a factor that regulates HIV-1 nuclear import and viral; replication of TNPO3 is well established to regulate HIV-1 nuclear import and viral replication. Here, we report that type I interferon (IFN)-inducible miR-128 directly targets two sites in the TNPO3 mRNA, significantly downregulating TNPO3 mRNA and protein expression levels. Challenging miR-modulated Jurkat cells or primary CD4⁺ T-cells with wild-type (WT), replication-competent HIV-1 demonstrated that miR-128 reduces viral replication and delays spreading of infection. Manipulation of miR-128 levels in HIV-1 target cell lines and in primary CD4⁺ T-cells by overexpression or knockdown showed that reduction of TNPO3 levels by miR-128 significantly affects HIV-1 replication but not murine leukemia virus (MLV) infection and that miR-128 modulation of HIV-1 replication is reduced with TNPO3-independent HIV-1 virus, suggesting that miR-128-indued TNPO3 repression contributes to the inhibition of HIV-1 replication. Finally, we determine that anti-miR-128 partly neutralizes the IFN-mediated block of HIV-1. Thus, we have established a novel role of miR-128 in antiviral defense in human cells, namely inhibiting HIV-1 replication by altering the cellular milieu through targeting factors that include TNPO3.IMPORTANCE HIV-1 is the causative agent of AIDS. During HIV-1 infection, type I interferons (IFNs) are induced, and their effectors limit HIV-1 replication at multiple steps in its life cycle. However, the cellular targets of INFs are still largely unknown. In this study, we identified the interferon-inducible microRNA (miR) miR-128, a novel antiviral mediator that suppresses the expression of the host gene TNPO3, which is known to modulate HIV-1 replication. Notably, we observe that anti-miR-128 partly neutralizes the IFN-mediated block of HIV-1. Elucidation of the mechanisms through which miR-128 impairs HIV-1 replication may provide novel candidates for the development of therapeutic interventions.

gga-miR-21 modulates Mycoplasma gallisepticum (HS strain)-Induced inflammation via targeting MAP3K1 and activating MAPKs and NF-κB pathways

Mycoplasma gallisepticum (MG) can target host cells and cause chronic respiratory disease (CRD) in chickens that is characterized by pMGA and concomitant. Although microRNAs (miRNAs) have been manifested are crucial regulatory noncoding RNAs with important effects on microbial pathogenesis and inflammatory response, how miRNAs regulate MG-induced inflammation remains to be discovered. The results showed that gga-miR-21 was up-regulated in MG-infected chicken embryonic lungs and MG infection of chicken embryo fibroblast cells (DF-1) compared with the control group. Overexpression of gga-miR-21 increased the inflammatory cytokines production, including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8) after MG infection, knockdown of gga-miR-21 had thoroughly inverse effects. Gene expression data combined with bioinformatics analysis and luciferase reporter assays demonstrated that mitogen-activated protein kinase kinase kinase 1(MAP3K1) was a novel target of gga-miR-21. The inhibition of MAP3K1 by gga-miR-21 resulted in the accumulation of NF-κB in the nucleus, which in turn generate higher inflammatory cytokines. Furthermore, upregulation of gga-miR-21 significantly inhibited MG propagation and promoted MG-infected DF-1 cells proliferation by increasing the cell cycle progression and suppressing cell apoptosis. Our study provides evidence for proinflammatory effects of gga-miR-21 which is mediated at least in part by targeting MAP3K1 in the MG-infected DF-1 cells. gga-miR-21 activates MAPKs and NF-κB signaling pathways via targeting MAP3K1, and then promotes the production of inflammatory cytokines and cell proliferation by increasing the cell cycle progression and suppressing cell apoptosis to defend against MG infection.

Exosomes Carry microRNAs into Neighboring Cells to Promote Diffusive Infection of Newcastle Disease Virus

Newcastle disease virus (NDV), an avian paramyxovirus, was shown to prefer to replicate in tumor cells instead of normal cells; however, this mechanism has not been fully elucidated. Exosomes play a crucial role in intercellular communication due to the bioactive substances they carry. Several studies have shown that exosomes are involved in virus infections. However, the effect that exosomes have on NDV-infected tumor cells is not known. In this study, we focus on the role of exosomes secreted by NDV-infected HeLa cells in promoting NDV replication. Three miRNA candidates (miR-1273f, miR-1184, and miR-198) embraced by exosomes were associated with enhancing NDV-induced cytopathic effects on HeLa cells. Furthermore, luciferase assays, RT-qPCR, and enzyme-linked immunosorbent assay (ELISA) all demonstrated that these miRNAs could suppress interferon (IFN)-β gene expression. Enhanced NDV replication in HeLa cells was identified by Western blot and plaque assays. Based on these results, we speculate that NDV employed exosomes entry into neighboring cells, which carry miRNAs, resulting in inhibition of the IFN pathway and promotion of viral infection. To our knowledge, this is the first report on the involvement of NDV-employed exosomes in tumor cells, and as such, it provides new insights into the development of anti-tumor therapies.

Cat and Mouse: HIV Transcription in Latency, Immune Evasion and Cure/Remission Strategies

There is broad scientific and societal consensus that finding a cure for HIV infection must be pursued. The major barrier to achieving a cure for HIV/AIDS is the capacity of the HIV virus to avoid both immune surveillance and current antiretroviral therapy (ART) by rapidly establishing latently infected cell populations, termed latent reservoirs. Here, we provide an overview of the rapidly evolving field of HIV cure/remission research, highlighting recent progress and ongoing challenges in the understanding of HIV reservoirs, the role of HIV transcription in latency and immune evasion. We review the major approaches towards a cure that are currently being explored and further argue that small molecules that inhibit HIV transcription, and therefore uncouple HIV gene expression from signals sent by the host immune response, might be a particularly promising approach to attain a cure or remission. We emphasize that a better understanding of the game of "cat and mouse" between the host immune system and the HIV virus is a crucial knowledge gap to be filled in both cure and vaccine research.