Heat shock protein and heat shock factor 1 expression and localization in vaccinia virus infected human monocyte derived macrophages

A Practical Framework for ASFV Disinfectant Evaluation: Differentiating Cytopathic Effects from Cytotoxicity via Integrated Analytical Methods

African swine fever virus (ASFV) is a highly virulent DNA virus that has spread globally since its introduction into Georgia in 2007, causing substantial economic losses in the swine industry. In the absence of an effective vaccine, chemical disinfection remains a key strategy for disease control. However, in cell-based disinfectant efficacy testing, distinguishing between disinfectant-induced cytotoxicity and virus-induced cytopathic effects (CPEs) remains a major challenge, leading to the potential misinterpretation of results. To address this, we developed a multi-step analytical framework to differentiate CPEs from cytotoxicity using a Vero cell-adapted ASFV strain. Virkon® S was tested at three dilutions-375×, 275× (manufacturer-recommended), and 175×-and evaluated through CPE observation, lactate dehydrogenase (LDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, and antigen detection via lateral flow immunoassay (p30) and immunofluorescence (p54). Notably, the 375× dilution achieved effective viral inactivation with significantly lower cytotoxicity, demonstrating that this framework can facilitate a more refined determination of disinfectant working dilutions. Furthermore, increased p30 signals after disinfection and the observation of lower cytotoxicity in virus-plus-disinfectant groups compared to disinfectant-only groups highlight the complexity of virus-disinfectant interactions and the potential for misinterpretation. This study provides a standardized and interpretable strategy for assessing ASFV disinfectant efficacy and offers a practical basis for evaluating other enveloped viruses in future disinfection studies.

Bacteria in hypertrophic scars promote scar formation through HSBP1-mediated autophagy

Bacterial colonisation in hypertrophic scars (HSs) has been reported, yet the precise mechanism of their contribution to scar formation remains elusive. To address this, we examined HS and normal skin (NS) tissues through Gram staining and immunofluorescence. We co-cultured fibroblasts with heat-inactivated Staphylococcus aureus (S. aureus) and evaluated their levels of apoptosis and proliferation by flow cytometry and Cell Counting Kit-8 assay, respectively. Additionally, we performed proteomic analysis and western blotting to identify upregulated proteins. To assess autophagy levels, we examined light chain 3 (LC3) expression through western blotting and immunofluorescence, and transmission electron microscopy (TEM) was performed to detect autophagy-associated vesicles. Our results demonstrated a notable increase in bacterial load, primarily S. aureus, in HS tissues. Furthermore, S. aureus promoted fibroblast proliferation and enhanced the expression of profibrotic markers such as transforming growth factor β1 (TGF-β1), vascular endothelial growth factor (VEGF), collagen I, collagen III and α smooth muscle actin (α-SMA). Proteomic analysis highlighted heat shock factor-binding protein 1 (HSBP1) as a key upregulated protein mediating the profibrotic effects induced by S. aureus. Knockdown of HSBP1 reversed these effects. Intriguingly, HSBP1 also upregulated LC3 and Beclin-1 expression and increased the number of autophagosomes in fibroblasts. Finally, when fibroblasts stimulated by S. aureus were treated with HSBP1 siRNA, autophagy levels decreased significantly. Collectively, our findings suggest that S. aureus, via HSBP1, stimulates fibroblast proliferation and promotes their transition into myofibroblasts, triggering autophagy and fibrosis. These results underscore the potential of HSBP1 as a therapeutic target for the management of HSs.

Genotype-environment associations reveal genes potentially linked to avian malaria infection in populations of an endemic island bird

Patterns of pathogen prevalence are, at least partially, the result of coevolutionary host-pathogen interactions. Thus, exploring the distribution of host genetic variation in relation to infection by a pathogen within and across populations can provide important insights into mechanisms of host defence and adaptation. Here, we use a landscape genomics approach (Bayenv) in conjunction with genome-wide data (ddRADseq) to test for associations between avian malaria (Plasmodium) prevalence and host genetic variation across 13 populations of the island endemic Berthelot's pipit (Anthus berthelotii). Considerable and consistent spatial heterogeneity in malaria prevalence was observed among populations over a period of 15 years. The prevalence of malaria infection was also strongly positively correlated with pox (Avipoxvirus) prevalence. Multiple host loci showed significant associations with malaria prevalence after controlling for genome-wide neutral genetic structure. These sites were located near to or within genes linked to metabolism, stress response, transcriptional regulation, complement activity and the inflammatory response, many previously implicated in vertebrate responses to malarial infection. Our findings identify diverse genes - not just limited to the immune system - that may be involved in host protection against malaria and suggest that spatially variable pathogen pressure may be an important evolutionary driver of genetic divergence among wild animal populations, such as Berthelot's pipit. Furthermore, our data indicate that spatio-temporal variation in multiple different pathogens (e.g. malaria and pox in this case) may have to be studied together to develop a more holistic understanding of host pathogen-mediated evolution.

Tumor Temperature: Friend or Foe of Virus-Based Cancer Immunotherapy

The temperature of a solid tumor is often dissimilar to baseline body temperature and, compared to healthy tissues, may be elevated, reduced, or a mix of both. The temperature of a tumor is dependent on metabolic activity and vascularization and can change due to tumor progression, treatment, or cancer type. Despite the need to function optimally within temperature-variable tumors, oncolytic viruses (OVs) are primarily tested at 37 °C in vitro. Furthermore, animal species utilized to test oncolytic viruses, such as mice, dogs, cats, and non-human primates, poorly recapitulate the temperature profile of humans. In this review, we discuss the importance of temperature as a variable for OV immunotherapy of solid tumors. Accumulating evidence supports that the temperature sensitivity of OVs lies on a spectrum, with some OVs likely hindered but others enhanced by elevated temperatures. We suggest that in vitro temperature sensitivity screening be performed for all OVs destined for the clinic to identify potential hinderances or benefits with regard to elevated temperature. Furthermore, we provide recommendations for the clinical use of temperature and OVs.

Genomic associations with poxvirus across divergent island populations in Berthelot's pipit

Understanding the mechanisms and genes that enable animal populations to adapt to pathogens is important from an evolutionary, health and conservation perspective. Berthelot's pipit (Anthus berthelotii) experiences extensive and consistent spatial heterogeneity in avian pox infection pressure across its range of island populations, thus providing an excellent system with which to examine how pathogen-mediated selection drives spatial variation in immunogenetic diversity. Here we test for evidence of genetic variation associated with avian pox at both an individual and population-level. At the individual level, we find no evidence that variation in MHC class I and TLR4 (both known to be important in recognising viral infection) was associated with pox infection within two separate populations. However, using genotype-environment association (Bayenv) in conjunction with genome-wide (ddRAD-seq) data, we detected strong associations between population-level avian pox prevalence and allele frequencies of single nucleotide polymorphisms (SNPs) at a number of sites across the genome. These sites were located within genes involved in cellular stress signalling and immune responses, many of which have previously been associated with responses to viral infection in humans and other animals. Consequently, our analyses indicates that pathogen-mediated selection may play a role in shaping genomic variation among relatively recently colonised island bird populations and highlights the utility of genotype-environment associations for identifying candidate genes potentially involved in host-pathogen interactions.

Comparison of Multiplexed Immunofluorescence Imaging to Chromogenic Immunohistochemistry of Skin Biomarkers in Response to Monkeypox Virus Infection

Over the last 15 years, advances in immunofluorescence-imaging based cycling methods, antibody conjugation methods, and automated image processing have facilitated the development of a high-resolution, multiplexed tissue immunofluorescence (MxIF) method with single cell-level quantitation termed Cell DIVETM. Originally developed for fixed oncology samples, here it was evaluated in highly fixed (up to 30 days), archived monkeypox virus-induced inflammatory skin lesions from a retrospective study in 11 rhesus monkeys to determine whether MxIF was comparable to manual H-scoring of chromogenic stains. Six protein markers related to immune and cellular response (CD68, CD3, Hsp70, Hsp90, ERK1/2, ERK1/2 pT202_pY204) were manually quantified (H-scores) by a pathologist from chromogenic IHC double stains on serial sections and compared to MxIF automated single cell quantification of the same markers that were multiplexed on a single tissue section. Overall, there was directional consistency between the H-score and the MxIF results for all markers except phosphorylated ERK1/2 (ERK1/2 pT202_pY204), which showed a decrease in the lesion compared to the adjacent non-lesioned skin by MxIF vs an increase via H-score. Improvements to automated segmentation using machine learning and adding additional cell markers for cell viability are future options for improvement. This method could be useful in infectious disease research as it conserves tissue, provides marker colocalization data on thousands of cells, allowing further cell level data mining as well as a reduction in user bias.

Identification of Vaccinia Virus Inhibitors and Cellular Functions Necessary for Efficient Viral Replication by Screening Bioactives and FDA-Approved Drugs

Four decades after the eradication of smallpox, poxviruses continue to threaten the health of humans and other animals. Vaccinia virus (VACV) was used as the vaccine that successfully eradicated smallpox and is a prototypic member of the poxvirus family. Many cellular pathways play critical roles in productive poxvirus replication. These pathways provide opportunities to expand the arsenal of poxvirus antiviral development by targeting the cellular functions required for efficient poxvirus replication. In this study, we developed and optimized a secreted Gaussia luciferase-based, simplified assay procedure suitable for high throughput screening. Using this procedure, we screened a customized compound library that contained over 3200 bioactives and FDA (Food and Drug Administration)-approved chemicals, most having known cellular targets, for their inhibitory effects on VACV replication. We identified over 140 compounds that suppressed VACV replication. Many of these hits target cellular pathways previously reported to be required for efficient VACV replication, validating the effectiveness of our screening. Importantly, we also identified hits that target cellular functions with previously unknown roles in the VACV replication cycle. Among those in the latter category, we verified the antiviral role of several compounds targeting the janus kinase/signal transducer and activator of transcription-3 (JAK/STAT3) signaling pathway by showing that STAT3 inhibitors reduced VACV replication. Our findings identify pathways that are candidates for use in the prevention and treatment of poxvirus infections and additionally provide a foundation to investigate diverse cellular pathways for their roles in poxvirus replications.

Heat shock factor 1 suppresses the HIV-induced inflammatory response by inhibiting nuclear factor-κB

The persistent inflammation aggravated by a disordered immune response is considered to be the major cause of CD4⁺ T cell depletion in lymphoid tissue, which impels the progression of AIDS. Here, we report that heat shock factor 1 (HSF1) works as an innate repressor of HIV-induced inflammation. The activation of HSF1 was found to accompany inflammation during HIV infection. Further research uncovered that HSF1 activation inhibited HIV-induced inflammation. In addition, HSF1 overexpression suppressed the inflammatory response induced by HIV, while HSF1 deficiency exacerbated that inflammation. Mechanistically, HSF1 was found to compete with nuclear factor-κB (NF-κB) in the nucleus. Generally, our report highlights that HSF1 is an important host factor in regulating HIV-induced inflammation and may work as a potential target for curing AIDS.

Targeting heat shock factor 1 as an antiviral strategy against dengue virus replication in vitro and in vivo

Fever onset is correlated with viremia in dengue virus (DENV) patients. Heat shock factor 1 (HSF1), a heat stress response host transcription factor, plays a crucial role in regulating multiple cellular functions, as well as the onset of infectious diseases. This study evaluated the role of HSF1 in DENV replication as a means of regulating DENV infection in vitro and in vivo. DENV infection activated HSF1 in both Ca²⁺ and protein kinase A-dependent manners. Inhibiting HSF1 effectively reduced DENV replication, not only in THP-1 cells but also in primary human monocytes. Activated HSF1 contributed to DENV replication by upregulating autophagy-related protein (Atg) 7, as autophagy is crucial for virus replication. Heat stress also activated HSF1, which in turn facilitated DENV replication. Activated HSF1, the increased Atg7, and autophagic induction were founded in the DENV-infected brains and pharmacologically inhibiting HSF1 reduced autophagy, viral protein expression, neuropathy, and mortality. These results provide new insight into HSF1 as a novel host factor for DENV infection through its role in facilitating autophagy-regulated viral replication in the brains.

Regulation of Viral Replication, Apoptosis and Pro-Inflammatory Responses by 17-AAG during Chikungunya Virus Infection in Macrophages

Chikungunya virus (CHIKV) infection has re-emerged as a major public health concern due to its recent worldwide epidemics and lack of control measures. Although CHIKV is known to infect macrophages, regulation of CHIKV replication, apoptosis and immune responses towards macrophages are not well understood. Accordingly, the Raw264.7 cells, a mouse macrophage cell line, were infected with CHIKV and viral replication as well as new viral progeny release was assessed by flow cytometry and plaque assay, respectively. Moreover, host immune modulation and apoptosis were studied through flow cytometry, Western blot and ELISA. Our current findings suggest that expression of CHIKV proteins were maximum at 8 hpi and the release of new viral progenies were remarkably increased around 12 hpi. The induction of Annexin V binding, cleaved caspase-3, cleaved caspase-9 and cleaved caspase-8 in CHIKV infected macrophages suggests activation of apoptosis through both intrinsic and extrinsic pathways. The pro-inflammatory mediators (TNF and IL-6) MHC-I/II and B7.2 (CD86) were also up-regulated during infection over time. Further, 17-AAG, a potential HSP90 inhibitor, was found to regulate CHIKV infection, apoptosis and pro-inflammatory cytokine/chemokine productions of host macrophages significantly. Hence, the present findings might bring new insight into the therapeutic implication in CHIKV disease biology.

Mechanism of Inhibition of Hsp90 Dimerization by Gyrase B Inhibitor Coumermycin A1 (C-A1) Revealed by Molecular Dynamics Simulations and Thermodynamic Calculations

Heat shock protein (Hsp) 90 an emerging and attracting target in the anti-HIV drug discovery process due to the key role it plays in the pathogenicity of HIV-1 virus. In this research study, long-range all-atom molecular dynamics simulations were engaged for the bound and the unbound proteins to enhance the understanding of the molecular mechanisms of the Hsp90 dimerization and inhibition. Results evidently showed that coumermycin A1 (C-A1), a recently discovered Hsp90 inhibitor, binds at the dimer's active site of the Hsp90 protein and leads to a substantial parting between dimeric opposed residues, which include Arg591.B, Lys594.A, Ser663.A, Thr653.B, Ala665.A, Thr649.B, Leu646.B and Asn669.A. Significant differences in magnitudes were observed in radius of gyration, root-mean-square deviation and root-mean-square fluctuation, which confirms a reasonably more flexible state in the apo conformation associated with it dimerization. In contrast, the bound conformer of Hsp90 showed less flexibility. This visibly highpoints the inhibition process resulting from the binding of the ligand. These findings were further validated by principal component analysis. We believe that the detailed dynamic analyses of Hsp90 presented in this study, would give an imperative insight and better understanding to the function and mechanisms of inhibition. Furthermore, information obtained from the binding mode of the inhibitor would be of great assistance in the design of more potent inhibitors against the HIV target Hsp90.

The virus-induced HSPs regulate the apoptosis of operatus APCs that result in autoimmunity, not in homeostasis

The viruses stand salient as environmental factors that trigger autoimmunity. The virus realizes its effects through induction of heat-shock proteins (HSPs) as well as by the viral IE-axis-mediated conversion of organ epithelial cells into virgin de novo professional antigen-presenting cells (APCs). The HSP is the accomplished operator in homeostasis by the logic of it being the regulator of apoptosis. By virtue of its regulation of apoptosis, the HSP is also involved in autoimmunity: (1) adornment of viral IE-axis-generated virgin de novo professional APCs with HSP-induced co-stimulatory molecules which transform these otherwise epithelial cells to competent antigen presenters, the operatus APCs, liable to apoptosis that becomes the initiator of organ damages; (2) molecular mimicry mechanism: epitopes on the HSP may be mistaken for viral peptides and be presented by operatus APCs to autoreactive TCRs resulting in the apoptosis of the operatus APCs; (3) regulation of MHC class II DR-mediated apoptosis of operatus APCS which can result in organ-specific autoimmune syndromes. We should remember, however, that Nature's intended purpose for apoptosis of the professional APCs is benevolence: as a principal regulator of immune homeostasis. But the apoptosis of our postulated operatus APCs can result in autoimmunity. The transformation of virgin de novo professional APCs to operatus APCs mirrors the maturation of DCs through their acquisition of HSP-induced costimulatory molecules. What happens to mature DCs as antigen presenters that end in homeostasis is replicated by what happens to operatus APCs that ends instead in autoimmunity.

The heat shock response restricts virus infection in Drosophila

Innate immunity is the first line of defence against pathogens and is essential for survival of the infected host. The fruit fly Drosophila melanogaster is an emerging model to study viral pathogenesis, yet antiviral defence responses remain poorly understood. Here, we describe the heat shock response, a cellular mechanism that prevents proteotoxicity, as a component of the antiviral immune response in Drosophila. Transcriptome analyses of Drosophila S2 cells and adult flies revealed strong induction of the heat shock response upon RNA virus infection. Dynamic induction patterns of heat shock pathway components were characterized in vitro and in vivo following infection with different classes of viruses. The heat shock transcription factor (Hsf), as well as active viral replication, were necessary for the induction of the response. Hsf-deficient adult flies were hypersensitive to virus infection, indicating a role of the heat shock response in antiviral defence. In accordance, transgenic activation of the heat shock response prolonged survival time after infection and enabled long-term control of virus replication to undetectable levels. Together, our results establish the heat shock response as an important constituent of innate antiviral immunity in Drosophila.

Subversion of cellular stress responses by poxviruses

Cellular stress responses are powerful mechanisms that prevent and cope with the accumulation of macromolecular damage in the cells and also boost host defenses against pathogens. Cells can initiate either protective or destructive stress responses depending, to a large extent, on the nature and duration of the stressing stimulus as well as the cell type. The productive replication of a virus within a given cell places inordinate stress on the metabolism machinery of the host and, to assure the continuity of its replication, many viruses have developed ways to modulate the cell stress responses. Poxviruses are among the viruses that have evolved a large number of strategies to manipulate host stress responses in order to control cell fate and enhance their replicative success. Remarkably, nearly every step of the stress responses that is mounted during infection can be targeted by virally encoded functions. The fine-tuned interactions between poxviruses and the host stress responses has aided virologists to understand specific aspects of viral replication; has helped cell biologists to evaluate the role of stress signaling in the uninfected cell; and has tipped immunologists on how these signals contribute to alert the cells against pathogen invasion and boost subsequent immune responses. This review discusses the diverse strategies that poxviruses use to subvert host cell stress responses.

The master regulator of the cellular stress response (HSF1) is critical for orthopoxvirus infection

The genus Orthopoxviridae contains a diverse group of human pathogens including monkeypox, smallpox and vaccinia. These viruses are presumed to be less dependent on host functions than other DNA viruses because they have large genomes and replicate in the cytoplasm, but a detailed understanding of the host factors required by orthopoxviruses is lacking. To address this topic, we performed an unbiased, genome-wide pooled RNAi screen targeting over 17,000 human genes to identify the host factors that support orthopoxvirus infection. We used secondary and tertiary assays to validate our screen results. One of the strongest hits was heat shock factor 1 (HSF1), the ancient master regulator of the cytoprotective heat-shock response. In investigating the behavior of HSF1 during vaccinia infection, we found that HSF1 was phosphorylated, translocated to the nucleus, and increased transcription of HSF1 target genes. Activation of HSF1 was supportive for virus replication, as RNAi knockdown and HSF1 small molecule inhibition prevented orthopoxvirus infection. Consistent with its role as a transcriptional activator, inhibition of several HSF1 targets also blocked vaccinia virus replication. These data show that orthopoxviruses co-opt host transcriptional responses for their own benefit, thereby effectively extending their functional genome to include genes residing within the host DNA. The dependence on HSF1 and its chaperone network offers multiple opportunities for antiviral drug development.

Heat shock transcription factor 1 is activated as a consequence of lymphocyte activation and regulates a major proteostasis network in T cells critical for cell division during stress

Heat shock transcription factor 1 (HSF1) is a major transcriptional regulator of the heat shock response in eukaryotic cells. HSF1 is evoked in response to a variety of cellular stressors, including elevated temperatures, oxidative stress, and other proteotoxic stressors. Previously, we demonstrated that HSF1 is activated in naive T cells at fever range temperatures (39.5°C) and is critical for in vitro T cell proliferation at fever temperatures. In this study, we demonstrated that murine HSF1 became activated to the DNA-binding form and transactivated a large number of genes in lymphoid cells strictly as a consequence of receptor activation in the absence of apparent cellular stress. Microarray analysis comparing HSF1(+/+) and HSF1(-/-) gene expression in T cells activated at 37°C revealed a diverse set of 323 genes significantly regulated by HSF1 in nonstressed T cells. In vivo proliferation studies revealed a significant impairment of HSF1(-/-) T cell expansion under conditions mimicking a robust immune response (staphylococcal enterotoxin B-induced T cell activation). This proliferation defect due to loss of HSF1 is observed even under nonfebrile temperatures. HSF1(-/-) T cells activated at fever temperatures show a dramatic reduction in cyclin E and cyclin A proteins during the cell cycle, although the transcription of these genes was modestly affected. Finally, B cell and hematopoietic stem cell proliferation from HSF1(-/-) mice, but not HSF1(+/+) mice, were also attenuated under stressful conditions, indicating that HSF1 is critical for the cell cycle progression of lymphoid cells activated under stressful conditions.

HIV-1 induces telomerase activity in monocyte-derived macrophages, possibly safeguarding one of its reservoirs

Monocyte-derived macrophages (MDM) are widely distributed in all tissues and organs, including the central nervous system, where they represent the main part of HIV-infected cells. In contrast to activated CD4(+) T lymphocytes, MDM are resistant to cytopathic effects and survive HIV infection for a long period of time. The molecular mechanisms of how HIV is able to persist in macrophages are not fully elucidated yet. In this context, we have studied the effect of in vitro HIV-1 infection on telomerase activity (TA), telomere length, and DNA damage. Infection resulted in a significant induction of TA. This increase was directly proportional to the efficacy of HIV infection and was found in both nuclear and cytoplasmic extracts, while neither UV light-inactivated HIV nor exogenous addition of the viral protein Tat or gp120 affected TA. Furthermore, TA was not modified during monocyte-macrophage differentiation, MDM activation, or infection with vaccinia virus. HIV infection did not affect telomere length. However, HIV-infected MDM showed less DNA damage after oxidative stress than noninfected MDM, and this resistance was also increased by overexpressing telomerase alone. Taken together, our results suggest that HIV induces TA in MDM and that this induction might contribute to cellular protection against oxidative stress, which could be considered a viral strategy to make macrophages better suited as longer-lived, more resistant viral reservoirs. In the light of the clinical development of telomerase inhibitors as anticancer therapeutics, inhibition of TA in HIV-infected macrophages might also represent a novel therapeutic target against viral reservoirs.

Molecular and functional characterization of HdHSP20: a biomarker of environmental stresses in disk abalone Haliotis discus discus

Heat shock proteins (HSPs) production in cell is inducible by many physical and chemical stressors, providing adaptive significance for organisms when faced with environmental changes. In this study, we characterized a novel small HSP gene from disk abalone, designated as HdHSP20, and investigated its temporal expression by different environmental stimuli. The full-length genome sequence of HdHSP20 is composed of three exons and two introns. The 5' flanking region contains multiple putative transcription factor binding sites related to stress response. The open reading frame of the HdHSP20 cDNA is 480 bp and encodes 160 amino acid residues with 18.76 kDa molecular mass. The deduced amino acid sequence shares highest similarity with HSP20 genes from other invertebrates. HdHSP20 also shows several structural signatures of small HSP, including the conserved α-crystallin domain, the absence of cysteine residues, a high number of Glx/Asx residues and the compact β-sandwich structure in the C-terminal region. Overexpression of recombinant HdHSP20 protein conveyed enhanced thermotolerance to Escherichia coli cells, suggesting its functional activity in the cellular chaperone network. qRT-PCR measurements of HdHSP20 mRNA level have shown rapid and drastic induction by extreme temperatures, extreme salinities, heavy metals and the microbial infections. Collectively, our results suggest that HdHSP20 gene is likely involved in the stress resistant mechanisms in disk abalone. Its expression may serve as a potential biomarker capable to indicate a stress state in abalone due to extreme environmental change and pathogen infection.

Role of Heat Shock Proteins in Viral Infection

One of the most intriguing and less known aspects of the interaction between viruses and their host is the impact of the viral infection on the heat shock response (HSR). While both a positive and a negative role of different heat shock proteins (HSP) in the control of virus replication has been hypothesized, HSP function during the virus replication cycle is still not well understood. This chapter describes different aspects of the interactions between viruses and heat shock proteins during infection of mammalian cells: the first part focuses on the modulation of the heat shock response by human viral pathogens; the second describes the interactions of HSP and other chaperones with viral components, and their function during different steps of the virus replication cycle; the last part summarizes our knowledge on the effect of hyperthermia and HSR modulators on virus replication.

Incapacitating the evolutionary capacitor: Hsp90 modulation of disease

The nature-nurture argument surrounding the mechanisms of disease causation cannot be resolved, as the roles of genes and environment are inextricably entwined. Environmental fluctuation is clearly a major modifier of phenotype, as well as a promoter of evolutionary change. Both types of variability can be mediated by the stress response pathway, with the Hsp90 chaperone family as key components. Hsp90 has been hailed as a capacitor for evolutionary change, because partial inhibition of its functions can uncover cryptic mutations, leading to unexpected phenotypes that, although generally deleterious, will under rare new environmental conditions provide improved survival to the carrier of that variant. There is, therefore, a strong environmentally elicited link between the capacity to reveal hidden variation as human disease phenotype and as novel morphological forms for evolutionary selection.

Human esophageal microvascular endothelial cells respond to acidic pH stress by PI3K/AKT and p38 MAPK-regulated induction of Hsp70 and Hsp27

The heat shock response maintains cellular homeostasis following sublethal injury. Heat shock proteins (Hsps) are induced by thermal, oxyradical, and inflammatory stress, and they chaperone denatured intracellular proteins. Hsps also chaperone signal transduction proteins, modulating signaling cascades during repeated stress. Gastroesophageal reflux disease (GERD) affects 7% of the US population, and it is linked to prolonged esophageal acid exposure. GERD is characterized by enhanced and selective leukocyte recruitment from esophageal microvasculature, implying activation of microvascular endothelium. We investigated whether phosphatidylinositol 3-kinase (PI3K)/Akt and MAPK regulate Hsp induction in primary cultures of human esophageal microvascular endothelial cells (HEMEC) in response to acid exposure (pH 4.5). Inhibitors of signaling pathways were used to define the contribution of PI3K/Akt and MAPKs in the heat shock response and following acid exposure. Acid significantly enhanced phosphorylation of Akt and MAPKs in HEMEC as well as inducing Hsp27 and Hsp70. The PI3K inhibitor LY-294002, and Akt small interfering RNA inhibited Akt activation and Hsp70 expression in HEMEC. The p38 MAPK inhibitor (SB-203580) and p38 MAPK siRNA blocked Hsp27 and Hsp70 mRNA induction, suggesting a role for MAPKs in the HEMEC heat shock response. Thus acidic pH exposure protects HEMEC through induction of Hsps and activation of MAPK and PI3 kinase pathway. Acidic exposure increased HEMEC expression of VCAM-1 protein, but not ICAM-1, which may contribute to selective leukocyte (i.e., eosinophil) recruitment in esophagitis. Activation of esophageal endothelial cells exposed to acidic refluxate may contribute to GERD in the setting of a disturbed mucosal squamous epithelial barrier (i.e., erosive esophagitis, peptic ulceration).