The role of heat shock proteins in HIV-1 pathogenesis: a systematic review investigating HSPs-HIV-1 correlations and interactions

Introduction

Human immunodeficiency virus (HIV) is a retrovirus that targets CD4 T cells in particular, which infection may result in severe immunodeficiency characterized by the failure of host adaptive immune defense to combat opportunistic infections and malignancies (Waymack & Sundareshan, 2023). Based on its genetic variation, HIV is categorized into two distinct types: HIV type 1 (HIV-1) and type 2 (HIV-2) (Esbjörnsson et al., 2019). Compared to HIV-2, which is primarily confined to West Africa, HIV-1 is more virulent and widespread and responsible for a pandemic that has been ongoing for over forty years. The HIV-1 pandemic is a significant public health emergency since the associated immunodeficiency allows a myriad of infectious diseases that may spread within and between different countries and geographic regions (Esbjörnsson et al., 2019; Waymack & Sundareshan, 2023).

Left untreated, HIV-1 insidiously replicates T cells and establishes latency, leading to chronic progression and severe disruption of the immune system, presenting as acquired immunodeficiency syndrome (AIDS) (Justiz Vaillant & Gulick, 2023). Around 40.4 million individuals have died from HIV, and 85.6 million have been infected ever since the beginning of the pandemic. At the end of 2022, 39 million people were living with HIV/AIDS worldwide. It is estimated that 0.7% (0.6%–0.8%) of adults between 15 and 49 are infected with HIV, even if the pandemic’s prevalence and severity considerably vary between different countries and regions (World Health Organization, 2023).

The pathophysiology of HIV-1 is intricate, involving viral entry, replication, integration, and latency establishment. HIV-1 uses different strategies in targeting various immune cells, such as macrophages and T cells, and tissues, such as the mucosal gut barrier and brain tissue (Vidya Vijayan et al., 2017; Masenga et al., 2023). The virus has to navigate through the complexities of cellular machinery to support its life cycle, hijacking host physiological processes while evading restriction factors with its accessory proteins, such as the HIV-1 Vpr protein that hijacks E3 ubiquitin ligases, Vif protein that antagonizes APOBEC3G-mediated hypermutation, and Vpu that counteracts viral release inhibition by CD317/Tetherin (Simon, Bloch & Landau, 2015; Yamashita & Engelman, 2017). The sheer number and amount of details in HIV-1-host interactions underscore the decades worth of scientific efforts to understand the cellular pathophysiology of HIV-1, and understanding these various viral-host processes that influence infection, replication, and latency is paramount to approach closer to the discovery of vaccine or cure for this virus (Masenga et al., 2023).

The management of HIV-1 infection mainly relies on antiretroviral therapy (ART), which typically includes three medications from two ARV drug classes (Tyler & Peter, 2023). ART is thought to be effective in suppressing viral replication and support the recovery of CD4 T-cell counts (Bahemana et al., 2020; Megasari & Wijaksana, 2023). However, despite the availability of ART, the management of HIV-1 infection currently faces several challenges, including the emergence of drug resistant strains which might reduce the effectiveness of various ARV drug classes. HIV drug resistance might affect both ART-naïve and experienced individuals (Megasari et al., 2019b; Megasari et al., 2019a; Khairunisa et al., 2020b; Khairunisa et al., 2020a; Khairunisa et al., 2020c; Khairunisa et al., 2023; World Health Organization, 2021; Bertagnolio et al., 2022); therefore, exploring novel therapeutic strategies for the management of HIV-1 infection is urgent.

Heat shock proteins (HSPs) are ubiquitous and conserved family of proteins which maintains cell proteostasis and protects cells from stresses (Iyer et al., 2021; Hu et al., 2022; Zhang & Yu, 2022). They function as molecular chaperones and have been frequently highlighted in cell physiological studies due to their multifaceted roles in many processes, including protein folding and refolding, complex assembly, and degradation (Hu et al., 2022; Zhang & Yu, 2022). HSPs are categorized based on molecular weight, where each member displays distinct functions and is implicated in various diseases like cancer and infection (Hu et al., 2022). In viral infection, HSPs have been suggested as one of the critical actors in antigen presentation and antiviral innate immunity response and have been implicated in several viral replication processes, including dengue, influenza, and hepatitis C virus (Ujino et al., 2009; Manzoor et al., 2014; Taguwa et al., 2015; Wan et al., 2020). A previous review study reported that several cellular HSPs interact with HIV-1 proteins and virions, and thus may be involved in the progression of HIV-1 infection, such as HSP40 and HIV-1 Nef protein to enhance viral translocation into the nucleus, HSP70 and HIV-1 virions as well as HIV-1 gag protein, and may be involved in the viral uncoating process, HSP90 blocks p-TEFb to suppress reactivation from latency. Other HSP family members appear to interact with HIV-1, but the mechanism or function remains unclear (Iyer et al., 2021).

HSPs have been known to catalyze cytokine secretion in antigen-presenting cells (Moré, Breloer & Von Bonin, 2001), but at the same time, HSPs also modulate different immune cells, such as T cells and regulatory T cells (Hauet-Broere et al., 2006; Brenu et al., 2013). Meanwhile, the involvement of HSPs in viral pathogen recognition, viral immune response modulation, and even direct interactions with viral proteins indicate that they are crucial to how an infection turns out (Wan et al., 2020; Zhang & Yu, 2022).

Recent studies have hinted at a significant connection between HSPs and HIV-1 infection pathogenesis (Iyer et al., 2021; Zhang & Yu, 2022). Given the significance of HSPs in cellular processes yet their enigmatic role in the framework of HIV-1 infection, a comprehensive review of their interplay is essential. Herein, we aim to delve into the current literature to clarify the role of HSPs in HIV-1 pathogenesis, offering insights that might pave the way to a deeper understanding of HIV-1-host interactions and possible novel therapeutic strategies.

Materials & Methods

Results

Search and screening results

We found 119 articles in PubMed, 204 in Scopus, 1,082 in Science Direct, 101 in Web of Science, 1,733 in SpringerLink, 13 in ProQuest, 17 in Google Scholar, and 63 in Sage. In total, 3,332 articles were identified. After deleting duplicate reports, we continued with the reading of 3,075 titles and abstracts, whereafter 37 articles were identified to read in full following exclusion of studies which are out-of-scope or not adhering to inclusion criteria. Finally, 33 studies were assessed for eligibility, in which 14 studies were included in this review (Joshi et al., 2013; Urano, Morikawa & Komano, 2013; Mercier et al., 2013; Anderson et al., 2014; Xia et al., 2015; Chaudhary et al., 2016; Joshi, Maidji & Stoddart, 2016; Painter, Zaikos & Collins, 2017; Mbonye et al., 2018; Ko et al., 2019; Priyanka Wadhwa et al., 2020; Chand, Iyer & Mitra, 2021; Iyer, Mitra & Mitra, 2022; Chand et al., 2023). The article collection, screening, and eligibility assessment process is shown in Fig. 1.

Discussion

Our review shows that, in the molecular process for HIV-1 infection, HSPs role as critical molecular chaperone implicated in different stages of viral infection. They play a role via direct interactions with viral proteins and indirect responses to cellular stress induced by viral infection (Neckers & Tatu, 2008). Such functions were exhibited by several HSP families studied in articles included in this review, particularly HSP40, HSP70, HSPBP1, and HSP90.

The HSP40 family,the most studied among all HSP isoforms, is involved in the viral entry and replication stages of HIV-1. The HSP40 family member B6/DNAJB6 is divided into two distinct isoforms based on the length of exons: the MRJ-L (large) and the MRJ-S (small) isoforms. The MRJ-L was recognized for its interaction with HIV−1 Vpr, which promotes viral nuclear entry and replication (Hanai & Mashima, 2003). It has been established that the expression level of the MRJ-L exhibits a positive correlation with HIV-1 replication (Ko et al., 2019). Notably, Chand et al. (2023) conducted a study indicating that other specific isoforms of the HSP40 family, namely DNAJB3, DNAJB6, DNAJB8, and DNAJC5, interacts with the HIV-1 Vif protein, which causes degradation and consequently reduces HIV-1 infectivity. In contrast, most other isoforms studied, such as DNAJA3, DNAJB1, DNAJB7, DNAJC4, DNAJC5B, DNAJC5G, DNAJC6, DNAJC22, and DNAJC30, which bind to the same contact site, increase viral entry and replication, suggesting conflicting roles within the HSP40 family (Chand et al., 2023). These findings complement those of an earlier study by the same research group, which followed the progress of infection from the onset of viral infection, the time when the number of viruses peaks, to the decline phase. It showed that the majority of HSP40 isoforms respond to stress during the early to peak stages of HIV-1 infection (days 1–7), with the exception of DNAJB6a, which decreases during the peak stage. This fluctuation contrasts with certain HSP70 isoforms, where the expression of HSPA1A, HSPA1B, HSPA6 decreased on days 1–7, while other isoforms HSPA1L, HSPA2, HSPA5, HSPA9, HSPA12, and HSPA13 increased on and after day 7 (Chand, Iyer & Mitra, 2021). Additionally, during the early phases of HIV-1 infection, the former isoforms exhibit a significant increase, except DNAJB6, which later declined in the peak and late phase of infection. This fluctuation contrasts with certain HSP70 isoforms, where several are upregulated (e.g., HSPA1L, HSPA2, HSPA5, HSPA9, HSPA12, and HSPA13), while others from the HSP70 family are downregulated post-peak infection phase (Chand, Iyer & Mitra, 2021). Furthermore, in neurons transfected with HIV-1 gp120 protein, HSP70 expression appeared to be decreased. Although the study did not specifically examine specific HSP70 isoforms, it supported the evidence that HIV-1 potentially suppresses HSP70 expression during the acute phase (Xia et al., 2015). Additional research on astrocytes infected with HIV-1 Tat has corroborated the results of this study. Mortalin, a specific member of the HSP70 family, exhibits a direct interaction with Tat, leading to its degradation. This interaction results in a reduction of Tat cytotoxic effects within the astrocytes (Priyanka Wadhwa et al., 2020). Further investigation is needed to characterize specific alterations in the expression of isoforms within the HSP40 and HSP70 families throughout the different phases of HIV-1 infection to identify potential biomarkers.

Another essential feature of the HSP40 and HSP70 is the ability of the two families to form complexes. The N-terminal J domain of HSP40 interacts with HSP70, which binds ATP and then catalyzes the hydrolysis of ATP to ADP. Client proteins bound to other domains of HSP40 are transferred to HSP70 and become substrates fixed by the structure of this chaperone complex (Alderson, Kim & Markley, 2016). Although not yet physically demonstrated, HIV-1 Rev is thought to be a client protein bound to one of the HSP40 domains. The resulting HSP40-HSP70 complex can inhibit the translation of the Rev protein, a regulatory protein that ensures viral RNA accumulation inside the host cell, thus preventing virus production (Urano, Morikawa & Komano, 2013).

HSP70 possesses an essential co-chaperone known as HSP70 binding protein 1 (HSPBP1), that serves as a nucleotide exchange factor, catalyzes ADP and ATP exchange on HSP70, a key step in the chaperone cycle. In addition, HSPBP1 exhibits independent functions in regulating cellular proteins (Mahboubi et al., 2020). HSPBP1 also interacts with HSP70 and HSP40. Whether in conjunction with HSP70 or alone, HSPBP1 suppresses virus production mediated by HSP40. Moreover, independent HSPBP1 expression negatively correlates with LTR-driven gene expression in HIV-1 in the presence of Tat, affecting the nuclear factor pathway of kappa B (NF-κB) and reducing LTR interaction with p50/p65, thereby inhibiting viral transcription (Chaudhary et al., 2016). A decrease in HSPBP1 expression due to HIV-1 infection mediated by Tat through its binding to cellular gene promoters is identified. The downregulation of HSPBP1 enhances LTR-driven gene expression, promoting HIV-1 infection (Iyer, Mitra & Mitra, 2022). Based on these findings provides insight into the role of HSPBP1 as a suppressor of HIV-1 replication by inhibiting LTR-driven gene expression, either independently or as a co-chaperone. However, this suppressive effect can be counteracted by HIV-1 Tat, which suppresses HSPBP1 gene promoter activity (Chaudhary et al., 2016; Iyer, Mitra & Mitra, 2022).

The final HSP we examined is HSP90, which is a prominent member of the family. It roles multifaceted in different stages of HIV-1 infection, including viral transmission, uncoating, and latency reactivation. HSP90 has two different isoforms, HSP90α and HSP90β, expressed in HIV-1 microvesicles. Both isoforms stimulated the maturation of microvesicle-infected dendritic cells, with HSP90β being more potent than the former, and increased ICAM-1 expression, thereby facilitating HIV-1 transfer to T cells and enhancing the cell-to-cell spread of infection (Mercier et al., 2013). In another study, HSP90β/HSP90AB1 was found inside HIV-1 virions but outside the viral core. Here, HSP90AB1 inhibition rendered HIV-1 non-infectious, while both wild-type and capsid-mutated HIV-1 could infect target cells expressing HSP90AB1 (Joshi et al., 2013). This finding confirmed previous research, which showed the role of HSP90 as a host factor that supports HIV uncoating and rescues impaired HIV replication, making the virus more resistant to antiretroviral drugs (Joshi & Stoddart, 2011). In this case, HSP90, especially the HSP90β isoform, is thought to be a positive regulator of HIV-1 infection, which warrants further investigation.

In a latent state, HIV-1 remains inactive within cellular reservoirs without replicating or expressing viral proteins. Reactivation of latent HIV-1 occurs when infected cells are activated, which involves complex cellular and molecular mechanisms. In particular, HSP90 is a chaperone that interacts with specific molecular factors in this process (Siliciano & Greene, 2011; Anderson et al., 2014). HSP90 plays a critical role in activating the NF-κB pathway, particularly in activating the inhibitor of NF-κB kinase (IKK) complex and facilitating the nuclear translocation of RelA/p65. It is also indirectly involved in activating protein kinase C (PKC). Inhibition of HSP90 disrupts activation of the IKK complex and positively correlated with reduced HIV-1 reactivation from latency, suggesting that HSP90 acts as a chaperone facilitating viral resurgence (Anderson et al., 2014). In a separate study headed by Joshi, Maidji & Stoddart (2016), it was found that blocking HSP activity effectively inhibits the transcription of HIV-1 within long-lasting viral reservoirs, thereby preventing the virus from reactivating.

Two independent studies present the relationship between HSP90 and HIV-1 transcription factor, the positive transcription elongation factor P-TEFb and its components, cyclin-dependent kinase 9 (CDK9) and cyclin T1, which are required for reactivating latent provirus (Painter, Zaikos & Collins, 2017; Mbonye et al., 2018). HIV-1 Tat recruits P-TEFb to regulate transcriptional elongation by RNA polymerase I (Asamitsu, Fujinaga & Okamoto, 2018). HSP90 serves as a chaperone in the P-TEFb assembly. Inhibiting HSP90 leads to the degradation of cyclin T1, blocking P-TEFb formation and suppressing HIV-1 transcription. In HIV-1-infected T cells, the suppression of viral transcription reduces the reactivation of latent provirus (Mbonye et al., 2018). This finding aligns with other studies on HIV-1 latency in quiescent progenitor cells, where quiescent cells display minimal proliferation, differentiation, and cell cycle progression, ultimately increasing HIV-1 latency. In this context, inhibiting HSP90 enhances quiescence and latency. Additionally, it has been discovered that PKC stimulation is responsible for keeping latency in dormant cells, which aligns with findings by Anderson et al., suggesting the potential involvement of HSP90 in the PKC stimulation pathway to facilitate transcription during the reactivation of latent HIV-1 (Anderson et al., 2014; Painter, Zaikos & Collins, 2017). A summary of the HSPs involvement in HIV-1 infection and life cycle is presented in Fig. 2.

Nevertheless, there are several limitations to be considered in our review. Firstly, our analysis exclusively encompassed full-text articles in English, thereby omitting potentially valuable data from articles in other languages, locally published, or inaccessible articles, which may introduce evidence selection bias into our review. Secondly, there is no existing quality assessment tool that covers all the critical aspects of an in vitro systematic review, including the quality assessment tool we used, the ToxRTool, which is originally designed for the assessment of in vitro toxicological data. A recent systematic review also highlighted the need for a comprehensive review guideline and quality assessment tool for in vitro systematic reviews and meta-analyses (Schneider et al., 2009; Tran et al., 2021). However, most of the ToxRTool criteria are suitable to assess the reliability level of the studies and further substantiate our conclusions.

Our review systematically summarized the currently available literature on the interactions between HSPs and HIV-1 pathogenesis as an effort to approach the necessary steps in discovering new anti-HIV-1 strategies via host-virus interactions. Nevertheless, as all studies included in this review were conducted in vitro, the clinical implications remain to be determined. We hope that in vivo studies to validate the clinical significance of these interactions and their potential as targets for therapeutic intervention are within reach.

Conclusions

This systematic review summarized the complex relationship between HSPs and HIV-1 infection, suggesting that these proteins have critical roles in the HIV-1 life cycle and anti-HIV-1 immune response. Further research is required to determine the clinical significance of this interaction and their potential as targets for future HIV-1 therapies.

Supplemental Information