Dormant yet dangerous: the role of cell rest in perseverance

ABSTRACT

Dormancy is a vital survival strategy employed by cells to endure stressful environments. It is characterized by a significant reduction in metabolic and proliferative activity and can be triggered by various conditions, including low humidity, hypoxia, nutrient deprivation, and pressure from the host immune response. Here, we highlight how tumor cells remain dormant in tissue and how fungi employ this strategy to survive and spread throughout the environment. However, we primarily discuss the dormancy mechanisms of Mycobacterium tuberculosis and Cryptococcus neoformans. These pathogens can enter a dormant state, allowing them to persist within the host for long periods. We emphasize the role of fatty acid metabolism and the genes associated with it in supporting dormancy under these stress conditions. Considering that dormancy is a reversible condition, it can occur with a viral co-infection, and the host is in a state of immunosuppression. Understanding the adaptation mechanisms of these pathogens is crucial for developing effective therapeutic approaches. Finally, we discuss some potential strategies for treating the disease, focusing on both active and dormant cells, which is essential for achieving long-term control and possibly eradicating the disease caused by these persistent pathogens.

Plain Language Summary

Wake up the dangerous cell

Dormancy is the term used to describe a cell that is alive but becomes inactive, exhibiting minimal activity or growth. This is a survival strategy that maintains cell activity in stressful environments, such as those lacking sufficient oxygen or nutrients. Dormant cells can be wake up and become active again if conditions improve or if other infections happen nearby. In this review, we look at two important human diseases, both of which can stay hidden in the body for a long time in this dormant state. One well-studied example is Mycobacterium tuberculosis, which causes tuberculosis. Another example is Cryptococcus neoformans, the fungus that causes meningitis, which is an inflammation in the membrane that surrounds the brain and spinal cord. We focus on how these organisms remain dormant, what conditions help them survive during this period of infection, and how we might target both active and dormant cells in future treatments. The study of dormancy is important in discovering new ways to prevent and treat these serious diseases more effectively.

GRAPHICAL ABSTRACT

1. Introduction

Across all biological kingdoms, cells exposed to environmental stressors can transition into distinct physiological states to ensure their survival. The cells maintain their potential for cultivation, although they exhibit a reduction in growth. They remain detectable in the host or environment for long periods without inducing the manifestation of overt diseases. In both bacteria and fungi, this mechanism is employed to tolerate antibiotics, antifungals, and host defenses while maintaining the ability to be cultured. Despite the well-known biological phenomenon, the terms persistence, latency, dormancy, and quiescence can be misused.

Cell persistence occurs when a subpopulation of cells survives exposure to high doses of antimicrobial agents or biofilm formation. This represents a short-term stress condition, not associated with mutations, that selectively supports cells capable of withstanding these conditions. Fungal biofilm, particularly described for Candida albicans, consists of a subgroup of cells known as antifungal-tolerant persistent cells, which can grow rapidly after being removed from the biofilm. Cell latency occurs under long-term adverse conditions, such as nutrient deprivation and hypoxia, where these cells reduce their metabolic activity, replication rate, and expression of immunogenic components. In a deeper state of latency, they may become viable but non-cultivable cells. There is no consensus in the literature that biofilm formation is the only condition to induce cell latency. Functionally, latency represents an overarching term that encompasses both quiescence and dormancy [1–4].

Several experimental models of latency have been developed to investigate the temporary state of inactivity in which cells can remain silent before resuming proliferation, potentially contributing to disease progression. Models for inducing dormancy and quiescence may include both in vivo and in vitro techniques as described in Table 1. Among the best-known models are yeast cells, bacterial cells, immune cells, structural cells like fibroblasts, and cancer cells. However, these models have limitations, as immortalized cell lines do not accurately reflect the biology and responses of primary human cells. Another point is the primary cells, which exhibit different responses depending on the age at which the peripheral population is produced; the data translated from experimental models to humans is not always directly applicable [5–13].

Table 1.

Cellular dormancy and quiescence in different in vivo and/or in vitro models induced through various mechanisms.

Cellular type	Species	Induction	Mechanism	Reference
Yeast	Cryptococcus neoformans	In vitro	Nutrient deprivation and hypoxia	[4]
Fission yeast	Schizosaccharomyces pombe	In vitro	Nitrogen restriction	[5]
Fetal human lung fibroblasts	CCL153	In vitro	Mitogen deprivation, growth at high cell density (“contact inhibition”), and disruption of cell-substratum adhesions	[6]
Naive peripheral T cells	Mouse splenocytes	In vitro e in vivo	Absence of TCR stimulation	[7]
Bacteria	Mycobacterium smegmatis	In vivo e in vitro	Immune response	[8]
Bacteria	Mycobacterium tuberculosis	In vivo	Immune response in mice and rabbits	[9,10]
Conidia	Aspergillus fumigatus	In vitro	Hypoxia, nutrient deprivation, and temperature	[11]
Breast cancer cell lines	BCCs MCF7, T47D, ZR75-1, 293T, U2OS e MG63	In vitro	Co-culture of breast cancer cell lines with bone marrow cells	[12]

So, cell persistence is more relevant in the context of drug tolerance and treatment failure or relapse, while latency refers to long-term survival in host environments with non-active infection and a risk of reactivation. Albeit they may share some interpretations, they serve distinct biological and clinical purposes. These reviews will focus more on latency, especially in the role of a dormant cell.

2. Latency strategies and mechanisms

Quiescence is a tightly regulated, reversible state of cellular latency characterized by withdrawal from the cell cycle, typically at the G0 phase, while maintaining basal metabolic activity. In stem cells, quiescence serves as a critical protective mechanism, enabling these cells to preserve their long-term regenerative capacity by avoiding replicative stress, DNA damage, and premature exhaustion. This state allows stem cells to remain poised for activation in response to physiological cues, such as tissue injury or homeostatic demand, ensuring prompt reentry into the cell cycle when required. Moreover, quiescence contributes to tissue integrity and longevity by minimizing the accumulation of replication-associated mutations and reducing oxidative stress [14–17]. Regulation of quiescence is orchestrated by a complex interplay of intrinsic factors, including transcriptional repressors, epigenetic modifications, and metabolic reprogramming, as well as extrinsic signals from the microenvironment, such as cytokines, growth factors, and extracellular matrix components. Dysregulation of quiescence can lead to pathological outcomes, as excessive quiescence may impair tissue regeneration, whereas loss of quiescence may result in stem cell depletion, accelerated aging, or malignant transformation [1–3,14–17].

On the other hand, cellular dormancy is a more profound and prolonged state of latency, characterized by a significant reduction in metabolic activity, which helps the organism conserve energy [2], even under favorable environmental conditions. It is a state of reversible growth arrest, characterized by cell cycle arrest in the G0/G1 phase, induction of CDK inhibitors, reduction of proliferation markers (such as Ki-67 and PCNA), activation of the p38 MAPK pathway, a compacted chromatin structure, and reduced cellular metabolism. Cells, such as stem cells, cancer cells, or bacterial and fungal cells, enter a state of metabolic inactivity, where their proliferation is minimal and cell death is also low. Dormant cells may be more resistant to conventional treatments that target proliferating cells, such as chemotherapy [17–23].

There are two main types of cellular dormancy inducers: (i) angiogenic dormancy, where cell proliferation and death are balanced based on the level of oxygen and nutrients supplied by preexisting blood vessels and angiogenesis induction, and (ii) immunogenic dormancy, where a state of balanced cell death and proliferation occurs due to surveillance by the host immune system. The study of cellular dormancy has expanded our understanding of the mechanisms by which microorganisms and cancer cells evade the immune system [14,24].

The tumor dormancy can be induced by both mechanisms, but the immunogenic dormancy is the main factor. In cases when minimal residual disease occurs, resistant dormant cells can move through the bloodstream or lymphatic system, survive environmental stresses and the immune system’s circulation, and then colonize distant organs, eventually forming a disseminated tumor. A much-discussed mechanism is the action of interferon-γ, produced by Th1, CD8+, and NK cells, which induces dormancy in cancer cells through pathways that are either dependent or independent of signal transducer and activator of transcription 1 (STAT1), wherein IFN-γ induces IRF1, a tumor suppressor gene, which in turn reduces Bcl2 and increases Bak, thereby facilitating the release of cytochrome c from mitochondria and the activation of caspases, resulting in apoptosis. Furthermore, TGF-β ligands expressed by tumor cells or niche cells in the tumor microenvironment control dormancy in several cancer models by activating protein kinases such as MAPK, which is involved in cell cycle arrest and stress responses, thereby promoting dormancy. Dormancy is also influenced by CXCL1, which is expressed by cancer-associated fibroblasts and negatively regulates the expression of differentiated embryonic chondrocyte gene 2 (DEC2) in oral squamous cell carcinoma cells, thereby awakening dormant cells and contributing to tumor recurrence [1,24–28].

Likewise, the ability to enter dormancy is also observed in cells of various microorganisms, including bacteria, viruses, and fungi. Various stressful conditions can induce microorganisms to enter a persistent state of dormancy after host infection, known as the viable but nonculturable cell (VBNC), allowing them to survive in adverse conditions. The VBNC state, first described in 1982 in Escherichia coli and Vibrio cholerae, was identified after these bacteria were cultured under stressed conditions. This maintained the cells’ viability with intact cell walls, but they could no longer be recovered by culture methods. Subsequent studies have shown that VBNC cells exhibit lower metabolic activity compared to quiescent cells, have a thicker peptidoglycan layer on their cell membranes, and display a spherical cell morphology [2,5,14,17,29,30].

Dormancy is a strategy employed by some microorganisms to evade or modulate the host immune response, allowing them to persist within the host and potentially reactivate under favorable conditions. One well-known example is the tubercle bacillus, which forms granulomas that can contain but not eliminate the infection. Immune activation and hypoxia within granulomas favor a shift in the microorganism’s physiology to a dormant, low-metabolism, and potentially non-replicating state, which can persist for decades, as described below [30–35].

3. Dormancy as a clever escape mechanism of Mycobacterium tuberculosis

The Mycobacterium tuberculosis (Mtb) dormancy mechanism is the one best characterized in the literature, as approximately 1.7 billion individuals in the global population present with the latent form of the infection (LTBI). There is the possibility of disease activation in immunosuppression, especially in immunocompromised individuals infected with HIV, resulting in a high mortality rate in these patients [36,37].

Mtb replication is controlled through effective host cellular immunity and via microbicidal mechanisms, such as the production of reactive oxygen and nitrogen species. Furthermore, granuloma formation creates a hypoxic environment characterized by nutrient and mineral depletion, as well as a reduced pH. These factors induce mechanisms that favor the development of the dormant form of Mtb, resulting in morphological changes, characterized by elevated levels of free mycolic acids and lipoarabinomannan (LAM) alongside a marked decrease in trehalose-6,6’-dimycolate (TDM) and a change in the ratio of arabinose to mannose over time, thickening of the bacterial cell wall, and favoring its survival, although compromising its infectivity. Additionally, negative regulation of metabolic genes and induction of genes related to lipid and fatty acid biosynthesis are observed in this scenario [38–42].

One crucial factor that contributes to Mtb dormancy is the utilization of fatty acids as a carbon source, obtained from lipid-rich macrophages present in the granuloma, which are converted to triacylglycerols (TAG) by the activation of the DosS-DosT/DosR dual-component system. The glyoxylate pathway, which involves the enzymes isocitrate lyase (ICL) and malate synthase, enables Mtb to metabolize, store, and release fatty acids, generating intermediates that are utilized in biomass synthesis and energy production. In addition, the proteins resulting from the expression of the gene mce1, as well as the protein Rv3723/LucA, play crucial roles in the transport and uptake of cholesterol and fatty acids from the host to the bacteria. This strategy ensures an essential energy source during dormancy and facilitates long-term survival within the host. Interestingly, the literature suggests that trehalose dimycolate, a lipid found in the cell wall of Mtb, along with the stimulation of microRNA (miR)-33 and its host strand, plays a crucial role in promoting granuloma formation and lipid accumulation in macrophages. These infected foam macrophages display impaired autophagy and lysosomal acidification, which impede the elimination of the bacteria. The pro-granulomatous inflammatory response, characterized by a predominance of T lymphocytes and interferon-inducible proteins (IFN-Is), is associated with the necrotic death of foam macrophages, a process that releases both lipids and Mtb within the caseous granuloma. In this context, the bacteria enhance the expression of genes related to lipid sequestration and metabolism, thereby contributing to the survival of extracellular Mtb. In a study with pckA-deficient Mtb bacteria, the gene of enzyme phosphoenolpyruvate carboxykinase (PEPCK), which catalyzes one of the initial steps in the conversion of precursors to glucose, did not grow in media containing fatty acids but remained viable in media containing glycerol, highlighting the importance of gluconeogenesis for the utilization of fatty acids as a carbon source and for maintaining bacterial viability during dormancy. The acquisition of host lipids compromises the efficacy of tuberculosis treatment, as it is correlated with the development of bacterial tolerance to combined antibiotic treatment [43–51].

In humans and murine models, genes activated by the DosS-DosT/DosR system have been identified as potent inducers of T and B cell responses, as well as stimulators of IFN-γ and TNF-α secretion, associated with granuloma formation. In primate models, it has been observed that these genes play a crucial role in the negative regulation of the immune response, favoring bacterial survival and eventual reactivation through this mechanism. These findings underscore the urgent need for the investigation and development of therapeutic strategies that address both the induction and regulation of immunity mediated by the DosS-DosT/DosR system during bacterial dormancy [52–54].

The complex interaction between Mtb and the immune system is one of the key challenges in tuberculosis control, especially in cases of inflammatory diseases such as Crohn’s disease, ulcerative colitis, psoriasis, and rheumatoid arthritis. Furthermore, with the use of immunosuppressive therapies, the activation of latent tuberculosis becomes a relevant issue to consider [55–57].

In patients receiving immunosuppressive therapy, especially those using TNF inhibitors, the immune mechanisms that maintain the bacterium in a dormant state are compromised. To mitigate the risk of reactivation, it is crucial to perform screening for latent infection using diagnostic tools such as the tuberculin skin test (TST) and interferon gamma release assays (IGRA). Patients diagnosed with LTBI should be evaluated for prophylactic treatment, typically with isoniazid (INH). In cases of INH tolerance, rifampin may be used as an alternative, with monthly monitoring during the treatment period [58,59].

4. Dormancy as a survival mechanism in fungal infection

Fungi are another example of dormant cells, a primary strategy for adapting to adverse conditions, leading to the formation of metabolically inactive spores or yeast. In Saccharomyces cerevisiae spores, specific biophysical properties have been observed. These include a highly viscous and acidic cytosol that alters the solubility of proteins, particularly metabolic enzymes, which become more soluble as the spore transitions to active cell proliferation following nutrient replenishment. A key regulator of this transition is heat shock protein Hsp42, which is essential for cytoplasmic transformation during germination. Talaromyces macrosporus ascospores, on the other hand, are constitutively dormant and germinate in response to a strong external shock, typically through heat treatment. The spores of Ustilaginoidea virens, a phytopathogen, can form chlamydospores, whose dormancy is broken by the Sphingomonadaceae family from the rhizosphere [60–64].

The conidia of three species of filamentous fungi, Aspergillus nidulans, Aspergillus fumigatus, and Talaromyces marneffei, undergo adjustments in their mRNA transcription in response to hostile environmental changes, which affect the fitness and capabilities of fungal cells after germination. For Aspergillus spp, it is a strategy for distributing conidia throughout the environment. When inhaled by immunocompromised individuals, it can germinate inside the respiratory tract, resulting in invasive pulmonary aspergillosis. The dormancy conidia may lead to resistance to antifungal drugs, the production of mycotoxins and secondary metabolites, and increased fungal virulence [12].

Regarding yeast, one of the main fungi capable of dormancy is Cryptococcus neoformans, whose infection can be compared to that of Mtb, as both pathogens share notable characteristics related to the dormant state, since the reactivation frequently occurs in contexts of immunosuppression, especially in HIV patients, and those with immunosenescence conditions. Thus, the comparison between these two infections not only elucidates the mechanisms underlying pathogenicity but also highlights the importance of effective prevention and treatment strategies for populations at risk [65–68].

The description of C. neoformans dormancy began with studies that characterized the fungal genetic profiles and the geographic origins of patients, corroborating the theory that patients acquired the infection years previously. Moreover, patients with preexisting serological reactivity developed cryptococcosis significantly earlier after transplantation, highlighting the potential utility of serological testing in predicting cases of cryptococcosis related to reactivation. Such testing then allows for preventive interventions such as antifungal prophylaxis in the case of immunosuppressed patients. As observed in Mtb, dormant C. neoformans exhibits a significant reduction in its stress response, as evidenced by decreased intracellular glutathione levels (Figure 1). The fungus exhibits a decline in metabolic activity and global transcriptional activity, as well as an increase in proteins associated with fatty acid degradation and metabolism. Despite this, the fungal cells maintain a high number of active, albeit depolarized, mitochondria, which preserve their viability. In addition, the protein profiles of the secretome and proteome of VBNC yeasts of C. neoformans reveal overproduction of cellular proteins related to intracellular processes, fatty acid metabolism, the cell cycle, and regulatory pathways, such as mTOR, as well as hypothetical proteins with no known function. Furthermore, the VBNC of C. neoformans promotes the accumulation of fatty acids by increasing their uptake and the expression of lipid transporters, which is related to the modulation of the macrophage immune response and the persistence of the fungus in the host [5,69,70].

Figure 1.

Mechanisms of dormancy maintenance. Similar mechanisms are responsible for the dormancy of Mtb and C. neoformans, activating specific pathways during this process. Both induce the formation of granulomas, which create a microenvironment favorable to dormancy. C. neoformans reduces the expression of β-glucan, decreasing its immunogenic capacity, but still stimulates chemotactic factors that maintain dormancy. Mtb increases lipoarabinomannan (LAM) and alters the ratio of arabinose and mannose. Dormancy is characterized by a decrease in metabolic activity and the utilization of fatty acids as an energy source, which is imported from lipid-laden macrophages within the granuloma. The DosS-DosT/DosR signaling system is activated, converting fatty acids into triacylglycerols (TAG), which are stored and used in biomass synthesis and energy production. Meanwhile, the fungus enhances the uptake of fatty acids and the expression of lipid transporters in macrophages. Among the mechanisms to maintain dormancy, Mtb utilizes gluconeogenesis to synthesize glucose from fatty acids, while fungal cells maintain active, albeit depolarized, mitochondria, ensuring their viability. Components created in BioRender. Bocca A. (2025) https://BioRender.com/nylrprk.

The interaction between macrophages and dormant C. neoformans alters the cell wall components, specifically reducing β-glucan expression, which results in a low immunogenic capacity. The reactivation of the dormant state was directly associated with interactions between non-polarized macrophages, which enabled the non-lytic exocytosis of the fungal cell, the absence of nitric oxide production, and the release of macrophage extracellular vesicles. These findings highlighted the role of macrophages in maintaining and reactivating cryptococcal infections. Besides, macrophages increased the expression of chemotactic factors, such as CCL4, indicating the induction of an immune response that, although unable to eliminate the fungus, can maintain its dormancy through cell recruitment and granuloma formation [71].

Immunocompetent individuals control C. neoformans infection through the formation of granulomas, which maintain the fungus in a dormant but viable state within lung structures. The interaction between the granuloma and the dormant fungus is crucial for understanding disease reactivation caused by immunosuppression and immunosenescence. Reactivation was primarily associated with structural disorganization of the granuloma containing the dormant fungus and the polarization of macrophages toward the M2 profile within it, as described by in vitro studies. The reactivation of C. neoformans has been described after treatment with FTY720 (Gilenya), a sphingosine-1-phosphate (S1P) analog that acts on the S1PR3 receptor, which is responsible for reducing the production of important cytokines for the differentiation of M1-like macrophages, such as IL-2 and IL-15. The same receptor also causes the abnormal displacement of macrophages outside the fibrous layer of the granuloma, reactivating the infection and resulting in a reduction in the survival of treated mice. Furthermore, FTY720 reduced the phagocytic capacity and the production of reactive oxygen species (ROS) by alveolar macrophages, which further facilitated fungal reactivation [29,72,73].

5. Dormancy is a cell state that can be broken

Different mechanisms capable of inducing microorganisms to break dormancy in the environment are described, including the “scout model,” which is an adaptive strategy for long-term survival and is strictly stochastic. Recently, a new strategy, named the “comfort timing” strategy, has been proposed. This strategy utilizes two mechanisms: increasing nutrient availability, which enables cell growth, and the reestablishment of physiological conditions, such as temperature, pH, and oxygen levels. Another mechanism proposed is the decrease in unfavorable conditions (Figure 2) [14,17,25,65,74]

Figure 2.

Mechanisms for breaking dormancy. The breaking of dormancy and the reestablishment of cellular growth can occur when specific signals converge, such as the availability of additional nutrients and the restoration of physiological conditions of temperature, pH, and oxygen. In the Scout model, randomly, some cells may break dormancy regardless of the microenvironment they are in, potentially colonizing new environments. Changes in the inflammatory profile or immunosuppression in the host can lead to the loss of granuloma integration, thereby favoring the reactivation of dormancy in contained microorganisms. Additionally, viral co-infections are also associated with reactivation, mainly from tumor cells. Fungi in a dormant state typically require additional stimuli to reactivate. C. neoformans needs pantothenic acid for in vitro reactivation, while A. fumigatus requires degradable carbon, along with water. In contrast, A. nidulans only needs glucose. Furthermore, quorum-sensing molecules play a complex role in fungi, contributing to the regulation of dormancy and germination through the exchange of opposing chemical signals, based on cell density and environmental conditions.

Within the host, cell reactivation is also linked to the host response. The inflammatory conditions are described as an important factor in Mtb reactivation, as well as immune suppression, whether through therapy or changes in immune system status. The loss of granuloma structure, when the mechanical stress is relieved, allows the cells to grow and spread. The viral infection induces cell reactivation, as described for breast cancer cell metastases [57–59,75]

A significant difference between VBNCs and quiescent fungal cells is the need for reactivation. Quiescent cells can quickly return to their culturable state once unfavorable stress is removed, while VBNCs require additional stimuli, such as specific growth conditions, reactivation-promoting factors, prolonged time, or additional nutrients, to regain their culturability. C. neoformans cells require the presence of pantothenic acid to be restored to an active state in vitro. However, there is no evidence regarding the necessary factors required to break the dormant cell in vivo, despite host’s immunosuppression. For A. fumigatus, exposure to a degradable carbon source in the presence of water and air is necessary. In contrast, for A. nidulans, only the presence of glucose is required in the host immunosuppression condition. Activation of Aspergillus dormant conidia increases intracellular osmotic pressure, leading to water uptake. During this process, the conidia begin to swell, a phenomenon also known as isotropic growth [5,12,23,30,66].

Another possible mechanism that facilitates fungi dormancy breakage is the quorum-sensing signal. The quorum-sensing molecules (QS) are low-molecular-weight, hormone-like secreted molecules that affect the regulation of morphogenesis, biofilm production, initiation of cellular apoptosis, and virulence. When its concentration reaches a threshold, it can trigger gene expression that, under certain conditions, induces cell proliferation, as described for C. albicans with farnesol and tyrosol, and for C. neoformans with Qsp1 and panthothenic acid. However, in some conditions, the QS inhibitors can prevent fungal growth. There is no consensus on the importance of QS in fungal dormancy breakage in biofilm, as the major studies focus on C. albicans, a commensal fungus that does not clearly produce dormant cells [5,76,77].

6. Perspectives on fighting cell dormancy

Understanding the biology of the cell’s dormant state is crucial to understanding its ability to reactivate in response to changes in the immune system. The persistence of the dormant cells poses a significant public health challenge, especially in immunocompromised individuals. Investigating the mechanisms that regulate dormancy and subsequent reactivation may offer valuable insights for the development of new therapeutic approaches and prevention strategies.

By exploring the mechanisms involved in the dormant state, it has also become possible to develop vaccine candidates that consider not only the antigens expressed during the replication stages but also those present in the dormant state. For Mtb, there are some candidates under development, such as the H56, ID93, and M72/AS01E vaccines, which have already demonstrated promising results. This approach ensures a robust and long-lasting immune response, surpassing the efficacy of the live – attenuated Bacillus Calmette – Guérin (BCG) vaccine [77–79].

Another approach to preventing the reactivation of dormant Mtb is the development of new therapeutic strategies targeting cell-specific dormancy markers, which aim to eradicate the infection and significantly reduce the required treatment time. In this end, several drugs are currently undergoing clinical trials, including the protein synthesis inhibitors Sutezolid and Delpazolid, the ATP synthesis inhibitor Telacebec, and the cell wall synthesis inhibitors OPC-167832 and SQ 109, all of which are in Phase II trials. Additionally, the ATP synthase proton pump inhibitor Bedaquiline, the mycolic acid synthesis inhibitor Delamanid, and Pretomanid, which inhibits mycolic acids through the generation of reactive nitrogen species and ATP depletion, are in Phase III trials. These studies demonstrate a significant ability to effectively target dormant Mtb. They advance the ability to prevent reactivation of the infection, offering a more effective solution in the fight against tuberculosis [35,80–86].

To understand fungal dormancy, it is essential to identify new compounds required for cell growth and germination. For A. fumigatus, there are many proteins that have been described only in the dormant state, like Grg1, RodA, CcpA, and MpdA, which are dramatically reduced after germination, and not detected in isotropically swelling conidia or hyphae stages. For C. neoformans, the differences between VBNC and conidia involved the global metabolism and specific pathways related to fatty acid metabolism, signal transduction, and proton transport. However, several proteins have been described as specific to spores; none of these are closely associated with dormancy [45,61,87,88].

Regarding the breakdown of dormancy by C. neoformans, developing effective therapeutic targets that do not affect host cells represents a significant challenge. It is essential not to overlook pathways that may offer good candidates for future investigations. A promising approach is the development of inhibitors that prevent the non-lytic exocytosis of fungal cells, helping to avoid the reactivation of the infection. Additionally, inhibitors of fungal metabolism during the dormant state can be considered, such as fatty acid degradation inhibitors, which hinder the fungus’s survival in this state. Another interesting strategy is the combination of antifungals with agents that modulate the immune response, aiming to increase the elimination of the fungus and prevent its reactivation. These approaches could open new perspectives in the treatment of infections caused by C. neoformans and in the management of fungal dormancy [29,89]

Further studies are needed to identify these targets that could contribute to novel fungal therapeutic strategies or the improvement of existing ones.

Funding Statement

This study was supported by (i) Conselho Nacional de Desenvolvimento Científico e Tecnológico [305584/2023–5], (ii) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and Fundação Coordenação de Aperfeiçoamento do Pessoal do Ensino Superior (CAPES), grant number [405934/2022–0] (The National Institute of Science and Technology—INCT Funvir), (iii) DPI/BCE of University of Brasilia [Edital nº 001/2025 DPI/BCE/UnB] and Fundação de Apoio a Pesquisa do Distrito Federal (FAPDF) [grant 193.00002346/2022–18]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Article highlights

• The differences between the states of persistence, quiescence, and dormancy are directly related to the conditions in which the cell is found and the extent of metabolic changes that affect its replication and cultivability. All these states are crucial for survival in hostile conditions and for evading the host’s immune response.

• Mycobacterium tuberculosis and Cryptococcus neoformans share similar mechanisms that induce and reactivate dormancy.

• The maintenance of dormancy involves changes in the cell wall, stress conditions as granuloma formation, and utilization of fatty acid metabolism pathways for energy supply.

• Some triggers for awakening from the dormant state include the restoration of nutrients, temperature, pH, and O₂, as well as immunosuppression, viral co-infections, and loss of granuloma integrity.

• Understanding the mechanisms of dormancy is crucial for the development of new vaccines and medications that aim to prevent relapses and achieve sterile cures, thereby preventing the reactivation of diseases.

Author contributions

Conceptualization, A.L.B.; writing – original draft preparation, A.L.B., R.L.L.S., G.B.T.; writing – review and editing, A.L.B., R.L.L.S., G.B.T., L.F. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.