Despite dramatic ART-mediated reductions in AIDS-related mortality, HIV persists because proviral DNA integrates into long-lived cell populations and establishes transcriptional latency. In 2024, an estimated 40.8 million people were living with HIV, with approximately 65% of cases in the WHO African Region, and 630,000 AIDS-related deaths were reported globally (Global HIV & AIDS statistics, 2025). This latent reservoir cannot be cleared by ART and represents the primary barrier to a cure. Consequently, cure research has increasingly focused on host biological systems that govern latency, transcriptional reactivation, cell survival, and stress adaptation, rather than exclusively targeting viral enzymes. Among these, cellular stress response pathways, including heat shock proteins (HSPs), have emerged as critical modulators of proviral transcriptional competence and reservoir stability (Nastiti et al., 2024).

HIV-1 is globally dominant, highly replication-competent, and exhibits transcriptionally active LTRs responsive to NF-κB and NFAT signaling. In contrast, HIV-2 is less transmissible, maintains lower steady-state viremia, and often exhibits deeper baseline latency. In regions of West Africa, dual HIV-1/HIV-2 infections have been reported, though literature on HSP involvement in HIV-2 and dual infection remains limited. These biological distinctions are mechanistically important because viral exploitation of chaperone networks, co-factor dependency, and stress response wiring may differ across HIV types. Preliminary evidence suggests Vpx-mediated interactions with HSP40 (DNAJB6) in HIV-2 may constitute a differential latency architecture not present in HIV-1, highlighting the need for comparative evaluation of HSP-mediated regulation (Kerkau et al., 1997; Berger and Cimarelli, 2014; Nastiti et al., 2024).

HIV cure strategies include sterilizing (eradication) cures, functional cures, and hybrid approaches combining reservoir reduction with immune-mediated clearance (Cillo and Mellors, 2016). Sterilizing cures aim to eliminate all replication-competent HIV. Prominent examples include the Berlin, London, and Düsseldorf patients, who achieved ART-free remission after hematopoietic stem cell transplantation from CCR5Δ32 homozygous donors (Gupta et al., 2020; Jensen et al., 2023); the New York patient, who remained off ART for over 14 months after a dual umbilical cord and adult stem cell transplant from a CCR5Δ32 (Hsu et al., 2023); and the Geneva patient, demonstrating prolonged remission via host-directed mechanisms beyond CCR5Δ32 editing (Sáez-Cirión et al., 2024).

Functional cures seek durable viral control without elimination, often via CRISPR-mediated modification of viral or host genes (Ophinni et al., 2018; Gao et al., 2020; Nguyen et al., 2021; Fan et al., 2022). The “Mississippi baby” exemplifies this, maintaining an undetectable viral load after early ART initiation before eventual rebound (Persaud et al., 2013).

Hybrid approaches combine reservoir reduction with immune boosting. “Shock and kill” uses latency-reversing agents (LRAs) to expose latent viruses, while “block and lock” enforces deep latency (Kula-Pacurar et al., 2021). Heat shock proteins (HSPs) and HSF1 now emerge as central regulators of proviral silencing versus activation, with HSP40 and related pathways representing promising, underexplored targets for host-directed cure strategies (Persaud et al., 2013; Berger and Cimarelli, 2014; Brown, 2015; Cillo and Mellors, 2016; Ophinni et al., 2018; Brown, 2020; Gao et al., 2020; Kula-Pacurar et al., 2021; Nguyen et al., 2021; Fan et al., 2022; First case of HIV cure in a woman after stem cell transplantation reported at CROI-2022, 2022; Nastiti et al., 2024; Tioka et al., 2025).

Heat shock proteins (HSPs) are not only vital for cellular homeostasis but also play multifaceted roles during viral infections. They interact with both host and viral components, making them central to the viral life cycle, influencing viral entry, replication, assembly, immune evasion, and latency regulation in both DNA and RNA viruses (Lubkowska et al., 2021).

HSPs play a dual role in viral infections. They can promote immune recognition and host protection by facilitating viral antigen presentation via MHC molecules (Li et al., 2002; Furuta and Eguchi, 2020). They, particularly, the extracellular HSPs can also, act as danger signals, activating dendritic cells and stimulating cytokine production through toll-like receptors (TLRs), particularly TLR2 and TLR4 (Hu et al., 2022). Conversely, viruses can subvert HSP functions to inhibit host immunity, to disrupt antigen processing, prevent apoptosis of infected cells and block proteasomal degradation (Iyer et al., 2021). Thus, HSPs may have both virus-supportive and host-protective roles in viral infections, making them attractive targets for antiviral strategies, particularly for complex viruses like HIV, which establish lifelong latency and evade immune clearance.

Furthermore, HSP may have roles in HIV latency. Chaudhary et al. (2016) in 2016 found that HSP70-binding protein 1 (HSPBP1), a co-chaperone of HSP70, is highly expressed during HIV latency and inhibits reactivation of HIV through the NF-κB pathway. Downregulation of HSPBP1 during reactivation highlights its possible role in maintaining latency. Similarly in 2023, Iyer et al. (2023) discovered that the HIV Tat protein suppresses HSPBP1 expression by interfering with its promoter, further emphasizing the intricate regulation of HSPs during the viral life cycle.

HIV-1 and HIV-2 differ not only in clinical outcomes and geographic prevalence but also in how they interface with host molecular chaperone systems. HIV-1 extensively utilizes HSP70, HSP90, and HSP40 families to fold viral proteins, stabilize replication complexes, and support transcriptional activation through interactions with Tat, Rev, Nef, and Vif to promote viral gene expression and replication (Agnew et al., 2003; Kumar and Mitra, 2005; Ko et al., 2019). Mechanistically, these patterns are consistent with broader HSP pro-viral roles seen in multiple viral systems (Lubkowska et al., 2021) and HIV-1 isoform-specific function mapping (Iyer et al., 2021).

In contrast, HIV-2 mechanistic chaperone data remain limited, but emerging evidence demonstrates differential architecture. HIV-2 uses the accessory protein Vpx to antagonize SAMHD1, and this function is facilitated by interaction with the HSP40 isoform DNAJB6, which enhances nuclear import of the HIV-2 pre-integration complex in non-dividing cells (Cheng et al., 2008). HIV-2’s promoter structure contains fewer NF-κB binding sites, potentially rendering it less responsive to stress-induced transcriptional programs mediated by HSF1 and HSP90, contributing to deeper basal latency states (Nastiti et al., 2024). These divergent patterns of HSP chaperone utilization may therefore contribute to the slower progression and distinct reservoir phenotype seen in HIV-2.

HIV-1/2 dual infections occur predominantly in West Africa, where both viral types co-circulate. Clinical studies suggest viral interference, sequential dominance, and context-dependent shifts over time, with HIV-1 often eventually becoming the predominant replicating strain in the absence of ART (van der Loeff et al., 2006; Campbell-Yesufu and Gandhi, 2011). HIV-1 demonstrates stronger reliance on HSP90, HSP70, and HSF1 as reactivation scaffolds, aligning with its greater transcriptional responsiveness to inflammatory signaling (Iyer et al., 2021; Lubkowska et al., 2021). In contrast, HIV-2 may use an alternative chaperone axis via HSP40 isoforms such as DNAJB6 to support Vpx-mediated PIC trafficking (Cheng et al., 2008), resulting in reduced reliance on canonical HSP90/HSF1-dependent reactivation circuits.

Whether these differential HSP dependency profiles translate into selective reactivation or functional competition between viral types in vivo is not yet known. At present, there are no direct comparative functional studies examining HSP isoform competition or HSP-mediated selective latency reversal in dually infected individuals. This remains a mechanistically plausible (yet untested) hypothesis that warrants directed investigation.

These considerations have implications for the design of therapeutic strategies. For example, HSP90/HSF1-driving LRAs may theoretically show differential efficacy against HIV-1 versus HIV-2; however, this has not been experimentally demonstrated and requires explicit testing in dual-infection systems.

A concise comparative summary of HSP utilization across HIV-1, HIV-2 and HIV-1/2 dual infection contexts is provided in Table 2.

As summarized in Table 2, current evidence for differential HSP utilization between HIV-1, HIV-2, and HIV-1/2 dual infection is uneven, with almost all characterized mechanistic HSP studies derived from HIV-1, and no direct dual-infection HSP comparative studies available. Despite growing recognition of HSP involvement in HIV biology, significant gaps remain in understanding how these interactions differ between HIV-1, HIV-2, and dual infections. The bulk of published data focuses on HIV-1 (Joshi et al., 2013; Mercier et al., 2013; Urano et al., 2013; Anderson et al., 2014; Xia et al., 2015; Chaudhary et al., 2016; Joshi et al., 2016; Mbonye et al., 2018; Priyanka et al., 2020; Chand et al., 2021; Chand et al., 2023; Iyer et al., 2023; Nastiti et al., 2024), leaving HIV-2 vastly understudied. Only a few HSP isoforms, such as DNAJB6, have been linked to HIV-2-specific processes. Comprehensive profiling of HSP expression and binding partners in HIV-2-infected cells is lacking.

Key areas where knowledge is limited include the mechanisms by which HSPs influence viral replication, latency, stress responses, and virion composition in HIV-2 and dual infections. In particular, the roles of specific HSP isoforms in HIV-2 infection remain largely undefined, and it is unclear whether HSP-mediated processes differ fundamentally from those in HIV-1. Moreover, no studies have examined HSP signatures in individuals dually infected with HIV-1 and HIV-2, nor how HSP-targeting latency-reversing strategies perform in these contexts. Proteomic and transcriptomic studies of latent reservoirs from such patients could illuminate type-specific stress responses and chaperone utilization.

Bridging these knowledge gaps is essential for developing pan-HIV cure strategies. Future research should employ high-resolution techniques, such as single-cell transcriptomics, isoform-specific knockdowns, and CRISPR-Cas9 editing, to delineate the precise roles of HSPs in HIV-2 and HIV-1/2 infections. Integrative approaches that combine virology, molecular chaperone biology, and latency modelling will be crucial for translating these insights into effective therapeutic interventions (Joshi et al., 2013; Urano et al., 2013; Anderson et al., 2014; Xia et al., 2015; Mbonye et al., 2018; Chand et al., 2021; Iyer et al., 2023; Nastiti et al., 2024).

Heat Shock Factor 1 (HSF1) is the master transcriptional regulator of the heat shock response. Under non-stress conditions, HSF1 remains monomeric and inactive in the cytoplasm, bound by molecular chaperones such as HSP70 and HSP90. Upon exposure to stress, including heat, oxidative stress, or viral infection, HSF1 undergoes trimerization, phosphorylation, and translocation to the nucleus. Once in the nucleus, it binds to heat shock elements (HSEs) within the promoter regions of heat shock protein genes, driving their expression (Åkerfelt et al., 2010; Hartl et al., 2011)​. More recent systematic interrogation confirms stress-induced HSF1 activation as a conserved trigger for chaperone upregulation in human T-cell systems (Nastiti et al., 2024). Figure 1 depicts the canonical HSF1 activation pathway and its role in driving transcription from the HIV LTR.

Recent findings have expanded the role of HSF1 beyond regulating chaperone genes, identifying its involvement in viral gene regulation, most notably in HIV. Pan and colleagues have provided compelling evidence that HSF1 binds directly to a conserved region within the HIV-1 LTR (Pan et al., 2016), leading to the recruitment of co-activators such as the histone acetyltransferase p300 and the P-TEFb complex, which is composed of CDK9 and cyclin T1. Together, they initiate and elongate transcription from the LTR, effectively reactivating latent virus. More recent data further reinforce that HSF1 activity is a decisive upstream determinant of LRA potency, where inhibition of HSF1 reduces latency reversal induced by several LRA classes in vitro and ex vivo (Timmons et al., 2020).

Additionally, HSF1 is upregulated in latently infected T cells subjected to heat stress (Pan et al., 2016). It is one of the most differentially expressed and functionally enriched transcriptional regulators during latency reversal. The knockdown of HSF1 significantly diminishes the reactivation of latent HIV, whereas HSF1 overexpression alone is sufficient to induce LTR activity, even in the absence of external inducers (Iyer et al., 2021; Xu et al., 2021). Complementarily, new mechanistic work expands pathway integration of HSF1 with cellular stress buffering that connects HSF1-regulated chromatin remodeling to inducible reservoir destabilization (Nastiti et al., 2024).

The exact binding motif of HSF1 within the LTR remains under investigation, but its close proximity to known NF-κB and Sp1 binding sites suggests a collaborative regulatory model. HSF1 may act synergistically with other transcription factors that are commonly involved in LTR activation, such as NFAT and AP-1 (Pan et al., 2016). These interactions suggest a broader stress-sensing module embedded within the LTR that responds to environmental or intracellular cues by triggering viral reactivation. Most of the research has focused on HIV-1, and it is imperative to determine if HSF1 binds similarly to the HIV-2 LTR.

The ability of HSF1 to bind the HIV-1 LTR and induce transcriptional reactivation has significant implications for HIV cure research, particularly within the context of the “shock and kill” strategy. This approach aims to purge the latent reservoir by pharmacologically or physiologically inducing proviral transcription “shock”, followed by immune- or drug-mediated clearance of reactivated cells “kill” (Margolis et al., 2016).

HSF1-mediated reactivation is unique, and physiologically relevant for the “shock” phase. Heat stress, febrile illness, or pharmacologic activators of HSF1 can increase its activity, triggering the transcription of latent HIV. Pan and colleagues have demonstrated that mild heat stress could induce reactivation in latent HIV models via HSF1, pointing to stress-induced reactivation as a viable therapeutic strategy (Pan et al., 2016). Based on this converging evidence, HSF1 is increasingly recognized as a therapeutically actionable stress-responsive transcriptional axis that can be leveraged for latency reversal, rather than simply a secondary consequence of stress biology.

Importantly, HSF1 appears to coordinate other latency-reversing pathways, serving as a multifaceted activator also integrates horizontally with other stress-responsive transcription modules by promoting chromatin remodeling through p300 recruitment and stimulating transcriptional elongation via P-TEFb., HSF1. These mechanisms align closely with current pharmacological approaches employing histone deacetylase inhibitors (HDACis), BET bromodomain inhibitors, and protein kinase C agonists. Some of these compounds may act in part by indirectly modulating HSF1 activity or its upstream signaling cascades (Zelin and Freeman, 2015). This aligns with current cure-directed LRAs that incorporate HSF1 axis contribution into potency predictions and failure modes (Tioka et al., 2025).

Nevertheless, the use of HSF1 as a therapeutic target presents several challenges. Systemic activation of HSF1 may upregulate other stress-response genes, potentially leading to off-target effects or unwanted immune activation. Furthermore, as HSF1 controls the expression of numerous cytoprotective proteins, including HSP70 and HSP90, indiscriminate activation may promote cell survival, thereby reducing the efficacy of the “kill” phase.

To circumvent these concerns, future approaches may involve the use of targeted HSF1 modulators or LTR-specific mimetics that activate transcription without triggering a complete stress response. Alternatively, heat shock mimetics or localized hyperthermia could be investigated as physical tools to induce site-specific HSF1 activation. Recent translational forward-looking analyses specifically recommend precision biophysical modulation over global pharmacologic activation (Tioka et al., 2025).

In HIV-2 and dual infections, where latency is more deeply entrenched and transcriptional activity is lower (Saleh et al., 2017; Bruggemans et al., 2023), HSF1-based strategies may face additional hurdles. It is unclear whether HIV-2 LTRs are as responsive to HSF1 activation, and whether other viral or host regulatory factors override HSF1-driven transcription in these contexts. Identifying and comparing stress response pathways in HIV-1 vs. HIV-2-infected cells will be key to adapting HSP-1 in the shock and kill approach for broader use.

Heat shock proteins also contribute to latency maintenance. Several HSP isoforms can suppress viral transcription, restrict essential viral protein stability, or reinforce antiviral host factors, rather than promote reactivation. For example, recent evidence confirms that isoform-selective HSP70 interactors can down-modulate NF-κB-driven proviral transcriptional activity in primary T cell models under physiologic stress states (Nastiti et al., 2024). Isoform-specific HSP40 family members, including DNAJB subclades, can reinforce host restriction factor efficiency and promote selective degradation of viral accessory proteins (Iyer et al., 2021). These isoform-specific suppressive effects provide a mechanistic basis for HSP-centered “block and lock” strategies in which selective reinforcement of protective chaperone subnetworks would stabilize latency.

HSP70 and HSP40 families are diverse and exhibit substantial functional redundancy. Different isoforms regulate distinct viral steps, and their effects vary across cell types, metabolic states, and reservoir compartments (Iyer et al., 2021). A recent systematic review of HSP–HIV interactions highlights that isoform patterns differ across reservoir phenotypes, suggesting that therapeutic latency stabilization could be targeted without inducing a global stress program (Nastiti et al., 2024). This contrasts with broad activation of the heat shock response, which risks inducing HSF1-dependent transcriptional rebound.

Pharmacologic data supports this model. Inhibition of HSF1 reduces the efficacy of multiple latency-reversing agents in vitro and ex vivo (Timmons et al., 2020). This indicates that selective dampening of stress transcription factor signaling could stabilize latency, particularly in inflammatory microenvironments where subthreshold activation cues persist. Forward-looking translational cure frameworks propose pairing isoform-targeted HSP modulatory strategies with immune-state-aligned containment to enforce reservoir suppression post-ART (Tioka et al., 2025). Future therapeutic development may therefore integrate isoform-specific HSP70/HSP40 enhancers with immune surveillance optimization and post-ART viral containment strategies (Tioka et al., 2025).

Previous studies have shown that heat shock proteins are intimately involved in controlling HIV-1 transcriptional activity and latency states. HSP70 family modulators can suppress HIV-1 replication through inhibition of NF-κB-mediated activation of viral gene expression, reinforcing transcriptional silencing (Chaudhary et al., 2016). HSP90 is also deeply involved in HIV latency biology. Rather than functioning as direct LRAs, HSP90 supports the host transcriptional machinery required for efficient LTR activation, and therefore HSP90 inhibition blocks reactivation rather than promotes it (Anderson et al., 2014). Multiple independent studies have demonstrated that HSP90 activity is permissive for latency reversal, whereas HSP90 inhibition prevents viral rebound following LRA exposure (Anderson et al., 2014; Joshi et al., 2016; Janssens et al., 2024; Noorsaeed et al., 2025). Moreover, because HSP90 signaling intersects directly with the HSF1 stress transcriptional axis, inhibition of HSF1 has been shown to attenuate the magnitude of latency reversal across diverse LRAs (Timmons et al., 2020). Taken together, these data reposition HSP90 (and upstream stress regulators such as HSF1) as host co-factors required for efficient latency reactivation, thereby aligning HSP90/HSF1 pharmacologic inhibition more closely with “block and lock” concepts rather than conventional “shock and kill” conceptualization.

Beyond latency reversal, modulating HSP activity could contribute to reducing the size or persistence of the HIV reservoir. For instance, suppression of HSPs that promote the survival of infected cells, such as HSP70 and HSP90, may sensitize latent reservoirs to immune clearance or apoptosis following reactivation (Rodina et al., 2007). Moreover, combining HSP modulation with immune-based approaches such as therapeutic vaccines, broadly neutralizing antibodies (bNAbs), or cytotoxic T lymphocyte (CTL) enhancement could improve the “kill” phase of “the shock and kill” strategy. Further, HSPs such as HSP60 and extracellular HSP70 are known to function as danger signals, activating innate immune receptors like TLR4 and stimulating cytokine production (Davies et al., 2006). This immunostimulatory property could be harnessed to enhance immune recognition of reactivated HIV-infected cells.

Recent findings demonstrate that HSP-mediated effects in HIV latency biology are bidirectional and not exclusively aligned with shock-and-kill paradigms. HSP70 family members can enforce latency via NF-κB suppression (Chaudhary et al., 2016), while HSP90 is required to maintain transcriptional competency necessary for reactivation, such that HSP90 inhibition blocks rather than induces latency reversal (Anderson et al., 2014; Joshi et al., 2016; Noorsaeed et al., 2025). These positions selected HSP modulators also within a “block and lock” conceptual space—where silencing is stabilized rather than reversed, suggesting that isoform-selective HSP targeting could serve both reservoir reduction and latency maintenance therapeutic objectives depending on context.

However, this approach has challenges as immune cell function impairment or induction of compensatory stress responses that support viral persistence may occur. Therefore, combinatorial regimens that include isoform-selective HSP modulators and immune-enhancing therapies may offer the best balance between efficacy and safety (Davies et al., 2006; Rodina et al., 2007; Anderson et al., 2014; Haase and Fitze, 2015; Chaudhary et al., 2016).

Targeting host proteins like HSPs introduces several inherent complexities. Unlike direct-acting antivirals that target viral enzymes, host-directed therapies risk off-target effects and cellular toxicity. Many HSPs are ubiquitously expressed and essential for basic cell functions, especially under stress. Long-term or systemic inhibition of HSP90, for example, may lead to hepatotoxicity, gastrointestinal symptoms, or suppression of other essential signaling pathways (Okamoto et al., 2008).

Furthermore, HSPs play dual roles in HIV biology, supporting both viral replication and host defenses. For instance, HSP70 can stabilize apolipoprotein B mRNA editing enzyme, catalytic polypeptide 3G (APOBEC3G), a host restriction factor, while also assisting in viral protein folding (Sugiyama et al., 2011). Similarly, HSP40 isoforms show isoform-specific activity: some promote transcription, while others suppress it (Ko et al., 2019). This functional duality makes selective targeting, rather than broad inhibition, a critical goal for future drug development.

Another layer of complexity lies in HIV subtype diversity and dual HIV-1 and HIV-2 infection contexts. As already discussed, because HIV-2 and HIV-1/2 dual infections may engage HSPs differently, cure strategies targeting HSP pathways may need to be type-optimized.

To advance this field, novel tools and models are required to unravel the precise roles of HSPs in different stages of HIV infection. These include:

Furthermore, drug screening platforms using HSP–HIV interaction assays could help identify small molecules that either disrupt proviral HSP functions or enhance antiviral HSP activities. These compounds could form the basis of next-generation LRAs, latency stabilizers, or virion disruptors.

HSPs and their regulatory networks are rich, underexplored targets for HIV cure strategies. From latency reversal to reservoir sensitization and immune activation, they occupy multiple strategic nodes in host-virus interaction. With careful modulation and targeted delivery, they may help bridge the gap between current antiretroviral therapy and functional or sterilizing cures. However, realizing this potential requires addressing the biological complexity and therapeutic challenges of targeting host proteins, particularly in diverse viral subtypes and dual infection scenarios.

It is important to interpret HSP-centered therapeutic hypotheses within the limitations of current experimental systems. Many mechanistic data sets on HSP–HIV interactions are derived from transformed T-cell lines or acute infection models, which may not fully recapitulate primary reservoir biology (Siliciano and Greene, 2011). Reservoir composition also varies across tissue compartments, age, sex, genetic background, and HIV subtype, factors that may differentially shape HSP pathway dependency. Targeting host stress systems carries distinct safety considerations because HSPs regulate essential cellular proteostasis across multiple physiological processes (Haase and Fitze, 2015). Therefore, translation of chaperone-directed interventions will require isoform-specific pharmacology, primary cell validation, and integrated immunometabolic modeling to avoid broad stress toxicity while exploiting latency control potential (Joshi et al., 2016).