Aerosol delivery of SARS-CoV-2 human monoclonal antibodies in macaques limits viral replication and lung pathology

Passively administered monoclonal antibodies (mAbs) given before or after viral infection can prevent or blunt disease. Here, we examine the efficacy of aerosol mAb delivery to prevent infection and disease in rhesus macaques inoculated with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant via intranasal and intratracheal routes. SARS-CoV-2 human mAbs or a human mAb directed to respiratory syncytial virus (RSV) are nebulized and delivered using positive airflow via facemask to sedated macaques pre- and post-infection. Nebulized human mAbs are detectable in nasal, oropharyngeal, and bronchoalveolar lavage (BAL) samples. SARS-CoV-2 mAb treatment significantly reduces levels of SARS-CoV-2 viral RNA and infectious virus in the upper and lower respiratory tracts relative to controls. Reductions in lung and BAL virus levels correspond to reduced BAL inflammatory cytokines and lung pathology. Aerosolized antibody therapy for SARS-CoV-2 could be effective for reducing viral burden and limiting disease severity.

Blood-brain barrier penetration of non-replicating SARS-CoV-2 and S1 variants of concern induce neuroinflammation which is accentuated in a mouse model of Alzheimer's disease

COVID-19 and especially Long COVID are associated with severe CNS symptoms and may place persons at risk to develop long-term cognitive impairments. Here, we show that two non-infective models of SARS-CoV-2 can cross the blood-brain barrier (BBB) and induce neuroinflammation, a major mechanism underpinning CNS and cognitive impairments, even in the absence of productive infection. The viral models cross the BBB by the mechanism of adsorptive transcytosis with the sugar N-acetylglucosamine being key. The delta and omicron variants cross the BB B faster than the other variants of concern, with peripheral tissue uptake rates also differing for the variants. Neuroinflammation induced by icv injection of S1 protein was greatly enhanced in young and especially in aged SAMP8 mice, a model of Alzheimer's disease, whereas sex and obesity had little effect.

Titration and neutralizing antibody quantification by focus forming assay for Powassan virus

The development of high-throughput assays measuring Powassan virus (POWV) lineage I and II represents an important step in virological and immunological studies. By adapting focus-forming assays previously optimized for West Nile virus and Zika virus, this protocol is able to determine viral load, evaluate antivirals, and measure neutralizing antibodies. Although limited by its requirement of a detection antibody, this protocol includes a rapid and high-throughput assay for measuring viral titer. By utilizing a baby hamster kidney cell line and a 96-well plate format, this protocol allows for more sensitivity in the detection of POWV lineage I.

For complete details on the use and execution of this protocol, please refer to Stone et al. (2022).

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Powassan virus focus forming assay for evaluation of antivirals

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Antibody focus reduction neutralization assay (FRNT) for Powassan virus

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Steps describing Powassan virus lineage I and II titration

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Balanced T and B cell responses are required for immune protection against Powassan virus in virus-like particle vaccination

Powassan virus (POWV) is a tick-borne pathogen for which humans are an incidental host. POWV infection can be fatal or result in long-term neurological sequelae; however, there are no approved vaccinations for POWV. Integral to efficacious vaccine development is the identification of correlates of protection, which we accomplished in this study by utilizing a murine model of POWV infection. Using POWV lethal and sub-lethal challenge models, we show that (1) robust B and T cell responses are necessary for immune protection, (2) POWV lethality can be attributed to both viral- and host-mediated drivers of disease, and (3) knowledge of the immune correlates of protection against POWV can be applied in a virus-like particle (VLP)-based vaccination approach that provides protection from lethal POWV challenge. Identification of these immune protection factors is significant as it will aid in the rational design of POWV vaccines.

Targeting Chikungunya Virus Replication by Benzoannulene Inhibitors

A benzo[6]annulene, 4-(tert-butyl)-N-(3-methoxy-5,6,7,8-tetrahydronaphthalen-2-yl) benzamide (1a), was identified as an inhibitor against Chikungunya virus (CHIKV) with antiviral activity EC₉₀ = 1.45 μM and viral titer reduction (VTR) of 2.5 log at 10 μM with no observed cytotoxicity (CC₅₀ = 169 μM) in normal human dermal fibroblast cells. Chemistry efforts to improve potency, efficacy, and drug-like properties of 1a resulted in a novel lead compound 8q, which possessed excellent cellular antiviral activity (EC₉₀ = 270 nM and VTR of 4.5 log at 10 μM) and improved liver microsomal stability. CHIKV resistance to an analog of 1a, compound 1c, tracked to a mutation in the nsP3 macrodomain. Further mechanism of action studies showed compounds working through inhibition of human dihydroorotate dehydrogenase in addition to CHIKV nsP3 macrodomain. Moderate efficacy was observed in an in vivo CHIKV challenge mouse model for compound 8q as viral replication was rescued from the pyrimidine salvage pathway.

Zika Virus Causes Acute and Chronic Prostatitis in Mice and Macaques

BACKGROUND

Sexual transmission and persistence of Zika virus (ZIKV) in the male reproductive tract has raised concerned for potential damaging effects on function. Animal studies have demonstrated that ZIKV virus can infect and damage the testis and epididymis, and these results has been correlated to lower sperm counts in ZIKV-infected humans. The prostate plays a vital role in the male reproductive tract, with acute and chronic prostatitis linked to male infertility.

METHODS

In this study, we evaluated the effects of ZIKV virus on the prostate in mice and nonhuman primates.

RESULTS

In mice, ZIKV infected the prostate and triggered inflammation that persisted even after virus clearance. Evidence of chronic prostatitis associated with ZIKV infection remained for several months. Similar histological findings were observed in the prostate of ZIKV-infected rhesus macaques.

CONCLUSIONS

These studies establish that ZIKV replicates in the prostate and can cause acute and chronic inflammatory and proliferative changes in mouse and nonhuman primate models.

The E3 Ubiquitin Ligase SIAH1 Targets MyD88 for Proteasomal Degradation During Dengue Virus Infection

The dengue virus presents a serious threat to human health globally and can cause severe, even life-threatening, illness. Dengue virus (DENV) is endemic on all continents except Antarctica, and it is estimated that more than 100 million people are infected each year. Herein, we further mine the data from a previously described screen for microRNAs (miRNAs) that block flavivirus replication. We use miR-424, a member of the miR-15/16 family, as a tool to further dissect the role of host cell proteins during DENV infection. We observed that miR-424 suppresses expression of the E3 ubiquitin ligase SIAH1, which is normally induced during dengue virus 2 (DENV2) infection through activation of the unfolded protein response (UPR). Specific siRNA-mediated knockdown of SIAH1 also results in inhibition of DENV replication, demonstrating that this target is at least partly responsible for the antiviral activity of miR-424. We further show that SIAH1 binds to and ubiquitinates the innate immune adaptor protein MyD88 and that the antiviral effect of SIAH1 knockdown is reduced in cells in which MyD88 has been deleted by CRISPR/Cas9 gene editing. Additionally, MyD88-dependent signaling, triggered either by DENV2 infection or the Toll-like receptor 7 (TLR7) ligand imiquimod, is increased in cells in which SIAH1 has been knocked down by miR-424 or a SIAH1-specific siRNA. These observations suggest an additional pathway by which DENV2 harnesses aspects of the UPR to dampen the host innate immune response and promote viral replication.

A neonatal nonhuman primate model of gestational Zika virus infection with evidence of microencephaly, seizures and cardiomyopathy

Zika virus infection during pregnancy is associated with miscarriage and with a broad spectrum of fetal and neonatal developmental abnormalities collectively known as congenital Zika syndrome (CZS). Symptomology of CZS includes malformations of the brain and skull, neurodevelopmental delay, seizures, joint contractures, hearing loss and visual impairment. Previous studies of Zika virus in pregnant rhesus macaques (Macaca mulatta) have described injury to the developing fetus and pregnancy loss, but neonatal outcomes following fetal Zika virus exposure have yet to be characterized in nonhuman primates. Herein we describe the presentation of rhesus macaque neonates with a spectrum of clinical outcomes, including one infant with CZS-like symptoms including cardiomyopathy, motor delay and seizure activity following maternal infection with Zika virus during the first trimester of pregnancy. Further characterization of this neonatal nonhuman primate model of gestational Zika virus infection will provide opportunities to evaluate the efficacy of pre- and postnatal therapeutics for gestational Zika virus infection and CZS.

Defects in Antiviral T Cell Responses Inflicted by Aging-Associated miR-181a Deficiency

Generation of protective immunity to infections and vaccinations declines with age. Studies in healthy individuals have implicated reduced miR-181a expression in T cells as contributing to this defect. To understand the impact of miR-181a expression on antiviral responses, we examined LCMV infection in mice with miR-181ab1-deficient T cells. We found that miR-181a deficiency delays viral clearance, thereby biasing the immune response in favor of CD4 over CD8 T cells. Antigen-specific CD4 T cells in mice with miR-181a-deficient T cells expand more and have a broader TCR repertoire with preferential expansion of high-affinity T cells than in wild-type mice. Importantly, generation of antigen-specific miR-181a-deficient CD8 effector T cells is particularly impaired, resulting in lower frequencies of CD8 T cells in the liver even at time points when the infection has been cleared. Consistent with the mouse model, CD4 memory T cells in individuals infected with West Nile virus at older ages tend to be more frequent and of higher affinity.

Miscarriage and stillbirth following maternal Zika virus infection in nonhuman primates

Zika virus (ZIKV) infection in humans has been associated with severe congenital defects (i.e. microcephaly) and pregnancy loss. Here we show that 26% of nonhuman primates infected with Asian/American ZIKV in early gestation experienced fetal demise later in pregnancy despite few clinical signs of infection. Pregnancy loss due to asymptomatic ZIKV infection may therefore be a common but under-recognized adverse outcome related to maternal ZIKV infection.

A Novel Agonist of the TRIF Pathway Induces a Cellular State Refractory to Replication of Zika, Chikungunya, and Dengue Viruses

The ongoing concurrent outbreaks of Zika, Chikungunya, and dengue viruses in Latin America and the Caribbean highlight the need for development of broad-spectrum antiviral treatments. The type I interferon (IFN) system has evolved in vertebrates to generate tissue responses that actively block replication of multiple known and potentially zoonotic viruses. As such, its control and activation through pharmacological agents may represent a novel therapeutic strategy for simultaneously impairing growth of multiple virus types and rendering host populations resistant to virus spread. In light of this strategy's potential, we undertook a screen to identify novel interferon-activating small molecules. Here, we describe 1-(2-fluorophenyl)-2-(5-isopropyl-1,3,4-thiadiazol-2-yl)-1,2-dihydrochromeno[2,3-c]pyrrole-3,9-dione, which we termed AV-C. Treatment of human cells with AV-C activates innate and interferon-associated responses that strongly inhibit replication of Zika, Chikungunya, and dengue viruses. By utilizing genome editing, we investigated the host proteins essential to AV-C-induced cellular states. This showed that the compound requires a TRIF-dependent signaling cascade that culminates in IFN regulatory factor 3 (IRF3)-dependent expression and secretion of type I interferon to elicit antiviral responses. The other canonical IRF3-terminal adaptor proteins STING and IPS-1/MAVS were dispensable for AV-C-induced phenotypes. However, our work revealed an important inhibitory role for IPS-1/MAVS, but not TRIF, in flavivirus replication, implying that TRIF-directed viral evasion may not occur. Additionally, we show that in response to AV-C, primary human peripheral blood mononuclear cells secrete proinflammatory cytokines that are linked with establishment of adaptive immunity to viral pathogens. Ultimately, synthetic innate immune activators such as AV-C may serve multiple therapeutic purposes, including direct antimicrobial responses and facilitation of pathogen-directed adaptive immunity.IMPORTANCE The type I interferon system is part of the innate immune response that has evolved in vertebrates as a first line of broad-spectrum immunological defense against an unknowable diversity of microbial, especially viral, pathogens. Here, we characterize a novel small molecule that artificially activates this response and in so doing generates a cellular state antagonistic to growth of currently emerging viruses: Zika virus, Chikungunya virus, and dengue virus. We also show that this molecule is capable of eliciting cellular responses that are predictive of establishment of adaptive immunity. As such, this agent may represent a powerful and multipronged therapeutic tool to combat emerging and other viral diseases.

Zika Virus infection of rhesus macaques leads to viral persistence in multiple tissues

Zika virus (ZIKV), an emerging flavivirus, has recently spread explosively through the Western hemisphere. In addition to symptoms including fever, rash, arthralgia, and conjunctivitis, ZIKV infection of pregnant women can cause microcephaly and other developmental abnormalities in the fetus. We report herein the results of ZIKV infection of adult rhesus macaques. Following subcutaneous infection, animals developed transient plasma viremia and viruria from 1-7 days post infection (dpi) that was accompanied by the development of a rash, fever and conjunctivitis. Animals produced a robust adaptive immune response to ZIKV, although systemic cytokine response was minimal. At 7 dpi, virus was detected in peripheral nervous tissue, multiple lymphoid tissues, joints, and the uterus of the necropsied animals. Notably, viral RNA persisted in neuronal, lymphoid and joint/muscle tissues and the male and female reproductive tissues through 28 to 35 dpi. The tropism and persistence of ZIKV in the peripheral nerves and reproductive tract may provide a mechanism of subsequent neuropathogenesis and sexual transmission.

High-content assay to identify inhibitors of dengue virus infection

Dengue virus (DENV) infections are vectored by mosquitoes and constitute one of the most prevalent infectious diseases in many parts of the world, affecting millions of people annually. Current treatments for DENV infections are nonspecific and largely ineffective. In this study, we describe the adaptation of a high-content cell-based assay for screening against DENV-infected cells to identify inhibitors and modulators of DENV infection. Using this high-content approach, we monitored the inhibition of test compounds on DENV protein production by means of immunofluorescence staining of DENV glycoprotein envelope, simultaneously evaluating cytotoxicity in HEK293 cells. The adapted 384-well microtiter-based assay was validated using a small panel of compounds previously reported as having inhibitory activity against DENV infections of cell cultures, including compounds with antiviral activity (ribavirin), inhibitors of cellular signaling pathways (U0126), and polysaccharides that are presumed to interfere with virus attachment (carrageenan). A screen was performed against a collection of 5,632 well-characterized bioactives, including U.S. Food and Drug Administration-approved drugs. Assay control statistics show an average Z' of 0.63, indicative of a robust assay in this cell-based format. Using a threshold of >80% DENV inhibition with <20% cellular cytotoxicity, 79 compounds were initially scored as positive hits. A follow-up screen confirmed 73 compounds with IC₅₀ potencies ranging from 60 nM to 9 μM and yielding a hit rate of 1.3%. Over half of the confirmed hits are known to target transporters, receptors, and protein kinases, providing potential opportunity for drug repurposing to treat DENV infections. In summary, this assay offers the opportunity to screen libraries of chemical compounds, in an effort to identify and develop novel drug candidates against DENV infections.

The use of RNAi-based screens to identify host proteins involved in viral replication

The recent development of RNAi-based techniques for protein knockdown in mammalian cells has allowed for unprecedented flexibility in the study of protein function. Currently, large siRNA libraries are available that allow the knockdown of all proteins known to be encoded by the human genome. These libraries have been used to identify the host proteins required for the replication of several clinically important viruses, including HIV, flaviviruses and influenza. This review summarizes the methods used in RNAi-based screening for host factors involved in virus replication, and discusses published examples of such screens.

West Nile virus infection activates the unfolded protein response, leading to CHOP induction and apoptosis

West Nile virus (WNV)-mediated neuronal death is a hallmark of WNV meningitis and encephalitis. However, the mechanisms of WNV-induced neuronal damage are not well understood. We investigated WNV neuropathogenesis by using human neuroblastoma cells and primary rat hippocampal neurons. We observed that WNV activates multiple unfolded protein response (UPR) pathways, leading to transcriptional and translational induction of UPR target genes. We evaluated the role of the three major UPR pathways, namely, inositol-requiring enzyme 1-dependent splicing of X box binding protein 1 (XBP1) mRNA, activation of activating transcription factor 6 (ATF6), and protein kinase R-like endoplasmic reticulum (ER) kinase-dependent eukaryotic initiation factor 2alpha (eIF2alpha) phosphorylation, in WNV-infected cells. We show that XBP1 is nonessential or can be replaced by other UPR pathways in WNV replication. ATF6 was rapidly degraded by proteasomes, consistent with induction of ER stress by WNV. We further observed a transient phosphorylation of eIF2alpha and induction of the proapoptotic cyclic AMP response element-binding transcription factor homologous protein (CHOP). WNV-infected cells exhibited a number of apoptotic phenotypes, such as (i) induction of growth arrest and DNA damage-inducible gene 34, (ii) activation of caspase-3, and (iii) cleavage of poly(ADP-ribose) polymerase. The expression of WNV nonstructural proteins alone was sufficient to induce CHOP expression. Importantly, WNV grew to significantly higher viral titers in chop(-)(/)(-) mouse embryonic fibroblasts (MEFs) than in wild-type MEFs, suggesting that CHOP-dependent premature cell death represents a host defense mechanism to limit viral replication that might also be responsible for the widespread neuronal loss observed in WNV-infected neuronal tissue.

Sultam thiourea inhibition of West Nile virus

We have identified sultam thioureas as novel inhibitors of West Nile virus (WNV) replication. One such compound inhibited WNV, with a 50% effective concentration of 0.7 microM, and reduced reporter expression from cells that harbored a WNV-based replicon. Our results demonstrate that sultam thioureas can block a postentry, preassembly step of WNV replication.

The Src family kinase c-Yes is required for maturation of West Nile virus particles

The role of cellular genes in West Nile virus (WNV) replication is not well understood. Examination of cellular transcripts upregulated during WNV infection revealed an increase in the expression of the src family kinase (SFK) c-Yes. WNV-infected cell lines treated with the SFK inhibitor PP2 demonstrated a 2- to 4-log decrease in viral titers, suggesting that SFK activity is required for completion of the viral replication cycle. RNA interference mediated knock-down of c-Yes, but not c-Src, and similarly reduced virus yield, specifically implicating c-Yes in WNV production. Interestingly, PP2 treatment did not reduce intracellular levels of either viral RNA or protein, suggesting that the drug does not act on the early stages of replication. However, endoglycosidase H (endoH) digestion of the viral envelope (E) glycoprotein revealed that the acquisition of endoH-resistant glycans by E, but not endogenous major histocompatibility complex class I, was reduced in PP2-treated cells, demonstrating that E specifically does not traffic beyond the endoplasmic reticulum in the absence of SFK activity. Electron microscopy further revealed that PP2-treated WNV-infected cells accumulated an increased number of virions in the ER compared to untreated cells. Therefore, we conclude that inhibition of SFK activity did not interfere with virus assembly but prevented transit of virions through the secretory pathway. These results identify c-Yes as a cellular protein that is involved in WNV assembly and egress.

Human cytomegalovirus-encoded G protein-coupled receptor US28 mediates smooth muscle cell migration through Galpha12

Coupling of G proteins to ligand-engaged chemokine receptors is the paramount event in G-protein-coupled receptor signal transduction. Previously, we have demonstrated that the human cytomegalovirus-encoded chemokine receptor US28 mediates human vascular smooth muscle cell (SMC) migration in response to either RANTES or monocyte chemoattractant protein 1. In this report, we identify the G proteins that couple with US28 to promote vascular SMC migration and identify other signaling molecules that play critical roles in this process. US28-mediated cellular migration was enhanced with the expression of the G-protein subunits Galpha12 and Galpha13, suggesting that US28 may functionally couple to these G proteins. In correlation with this observation, US28 was able to activate RhoA, a downstream effector of Galpha12 and Galpha13 in cell types with these G proteins but not in those without them and activation of RhoA was dependent on US28 stimulation with RANTES. In addition, inactivation of RhoA or the RhoA-associated kinase p160ROCK with a dominant-negative mutant of RhoA or the small molecule inhibitor Y27632, respectively, abrogated US28-induced SMC migration. The data presented here suggest that US28 functionally signals through Galpha12 family G proteins and RhoA in a ligand-dependent manner and these signaling molecules are important for the ability of US28 to induce cellular migration.

Human cytomegalovirus inhibits transcription of the CC chemokine MCP-1 gene

In primary human diploid fibroblasts, infection with an unpurified stock of human cytomegalovirus induced accumulation of the CC chemokine MCP-1 in the cell culture medium. By 24 h postinfection, the level of MCP-1 returned to that in uninfected cultures. When cells were infected with UV-inactivated human cytomegalovirus, the induction of MCP-1 was still observed, but no reduction was seen by 24 h postinfection or later. This effect was the result of a decrease in the level of MCP-1 mRNA present within the infected cell. Infection with purified virus revealed that the induction of MCP-1 was due to an activity found in the medium of infected cells; purified virions did not induce the expression of MCP-1. However, infection with purified virions repressed the level of MCP-1 mRNA below that found in uninfected cells. Additionally, infection with human cytomegalovirus prevented the induction of MCP-1 expression by tumor necrosis factor alpha and interleukin-1beta. The CC chemokine receptor encoded by the human cytomegalovirus US28 open reading frame (ORF) did not appear to play a role in this process, since a mutant virus in which the US28 ORF had been deleted downregulated MCP-1 in the same manner.

A novel basic helix-loop-helix protein is expressed in muscle attachment sites of the Drosophila epidermis

We have found that a novel basic helix-loop-helix (bHLH) protein is expressed almost exclusively in the epidermal attachments sites for the somatic muscles of Drosophila melanogaster. A Drosophila cDNA library was screened with radioactively labeled E12 protein, which can dimerize with many HLH proteins. One clone that emerged from this screen encoded a previously unknown protein of 360 amino acids, named delilah, that contains both basic and HLH domains, similar to a group of cellular transcription factors implicated in cell type determination. Delilah protein formed heterodimers with E12 that bind to the muscle creatine kinase promoter. In situ hybridization with the delilah cDNA localized the expression of the gene to a subset of cells in the epidermis which form a distinct pattern involving both the segmental boundaries and intrasegmental clusters. This pattern was coincident with the known sites of attachment of the somatic muscles to tendon cells in the epidermis. delilah expression persists in snail mutant embryos which lack mesoderm, indicating that expression of the gene was not induced by attachment of the underlying muscles. The similarity of this gene to other bHLH genes suggests that it plays an important role in the differentiation of epidermal cells into muscle attachment sites.

Homologous sensitisation of embryonic chick atrial myocytes to adenosine: mediation by adenosine A1 receptor and guanine nucleotide binding protein

OBJECTIVE

The aim was to characterise the process and the mechanisms of sensitisation of the atrial myocyte to adenosine receptor agonist.

METHODS

The ability of adenosine A1 receptor to mediate inhibition of adenylyl cyclase activity and myocyte contractility was determined in atrial myocytes cultured from 14 d chick embryos. Under conditions in which the myocytes were sensitised to the effects of A1 agonist, changes in the levels of adenosine A1 receptor and pertussis toxin sensitive G proteins were determined and correlated with alterations in the adenylyl cyclase activity and contractile responses of the myocyte to the A1 agonist.

RESULTS

Removal of adenosine from the culture medium with adenosine deaminase resulted in an enhanced ability of the adenosine A1 receptor agonist R-N6-(2-phenylisopropyl)-adenosine to exert a direct, negative inotropic effect and to inhibit isoprenaline stimulated adenylyl cyclase activity. The increase in the extent of maximum inhibition of adenylyl cyclase activity and of myocyte contractility was 215(30), n = 5, and 90(10)%, n = 14, respectively. Binding of the antagonist radioligand [3H]-8-cyclopentyl-1,3-dipropylxanthine in membranes from myocytes pre-exposed to adenosine deaminase showed a 70% increase in the adenosine A1 receptor density and a 54% increase in the proportion of the high affinity adenosine A1 receptor: control 33(5)%, n = 5, versus sensitised 49(3)%, n = 5, p < 0.01. The increase in the total number of adenosine receptors and the proportion of the high affinity form was associated with a similar increase in the level of pertussis toxin sensitive G protein(s), as determined by pertussis toxin mediated 32P-ADP ribosylation and by immunoblotting. Prior exposure of the culture to the adenosine receptor antagonist 8-(p-sulphophenyl)theophylline also led to similar results.

CONCLUSIONS

The data indicate that the increased level of pertussis toxin sensitive G protein(s) results in an enhanced coupling to form the high affinity adenosine A1 receptor, that newly formed high affinity receptors are linked to an enhanced sensitivity of atrial myocytes to A1 adenosine agonist stimulation, and that upregulation of the G protein is a mechanism mediating the homologous sensitisation of cardiac adenosine A1 receptor pathway.