Validation of Home Visual Acuity Tests for Telehealth in the COVID-19 Era.

Importance: Visual acuity (VA) is one of the most important clinical data points in ophthalmology. However, few options for validated at-home VA assessments are currently available. Objective: To validate 3 at-home visual acuity tests in comparison with in-office visual acuity. Design, Setting, and Participants: Between July 2020 and April 2021, eligible participants with VA of 20/200 or better were recruited from 4 university-based ophthalmology clinics (comprehensive, cornea, glaucoma, and retina clinics). Participants were prospectively randomized to self-administer 2 of 3 at-home VA tests (printed chart, mobile phone app, and website) within 3 days before their standard-of-care clinic visit. Participants completed a survey assessing usability of the at-home tests. At the clinic visit, best-corrected Snellen distance acuity was measured as the reference standard. Main Outcomes and Measures: The at-home VA test results were compared with the in-office VA test results using paired and unpaired t tests, Pearson correlation coefficients, analysis of variance, χ2 tests, and Cohen κ agreement. The sensitivity, specificity, positive predictive value, and negative predictive value of each at-home test were calculated to detect significant VA changes (≥0.2 logMAR) from the in-office baseline. Results: A total of 121 participants with a mean (SD) age of 63.8 (13.0) years completed the study. The mean in-office VA was 0.11 logMAR (Snellen equivalent 20/25) with similar numbers of participants from the 4 clinics. Mean difference (logMAR) between the at-home test and in-office acuity was -0.07 (95% CI, -0.10 to -0.04) for the printed chart, -0.12 (95% CI, -0.15 to -0.09) for the mobile phone app, and -0.13 (95% CI, -0.16 to -0.10) for the website test. The Pearson correlation coefficient for the printed chart was 0.72 (95% CI, 0.62-0.79), mobile phone app was 0.58 (95% CI, 0.46-0.69), and website test was 0.64 (95% CI, 0.53-0.73). Conclusions and Relevance: The 3 at-home VA test results (printed chart, mobile phone app, and website) appeared comparable within 1 line to in-office VA measurements. Older participants were more likely to have limited access to digital tools. Further development and validation of at-home VA testing modalities is needed with the expansion of teleophthalmology care.

Diabetic eye disease: A review of screening and management recommendations.

The prevalence of diabetes is rapidly increasing, and it is now the leading cause of blindness worldwide. Although early detection of diabetic retinopathy is key to preventing vision loss, many patients do not receive appropriate examinations. Using a multidisciplinary approach, primary care physicians and eye care providers should follow evidence-based recommendations for screening and monitoring diabetic patients while working to improve patients' glycaemic index, blood pressure, and metabolic risk factors. Anti-vascular endothelial growth factor intravitreal injections in combination with panretinal photocoagulation and focal laser treatment remain the cornerstones of modern therapy. The many landmark studies for diabetic eye disease management should guide counselling and decision making for treating diabetic macular oedema, proliferative retinopathy and other diabetes-related eye diseases.

New horizons in adjuvants for vaccine development.

Adjuvant molecules, particularly toll like receptor (TLR) agonists have been in development for decades, though until now only a natural TLR 4 ligand (mono-phosphoryl lipid A, MPL) has been incorporated into licensed vaccine products, in formulations than enhance and complement the MPL activity. The inclusion of MPL-based formulations into vaccines has been based on enhancing antibody responses to subunit antigens, and has provided important proof-of-concept for enhancing desired immune responses to defined molecular targets. Challenges remain in adjuvant development, particularly for those that stimulated effective T cell responses for both preventative and therapeutic vaccines. The discovery of molecules, many based on RNA, that stimulate innate and adaptive immune responses and have the ability to stimulate potent CD8 T cell responses, has opened the door for development of a new generation of vaccines.

Repeatability of Adaptive Optics Automated Cone Measurements in Subjects With Retinitis Pigmentosa and Novel Metrics for Assessment of Image Quality.

PURPOSE: We determine the intersession repeatability of cone measurements via flood-illuminated adaptive optics (AO) imaging in patients with retinitis pigmentosa (RP), to better differentiate variation due to imaging inaccuracies versus pathology-driven change. METHODS: A total of 25 4° × 4° AO images were acquired three times on the same day in 10 subjects with RP, registered in i2K Retina, and cones were identified using a custom-built MATLAB algorithm. Nine equally spaced regions of interest were selected for each imaging set. A subset of subjectively "poor" and "good" quality images was selected by three independent graders, analyzed using cone density, cone location similarity (CLS) and cone spacing, and compared to age-matched normals. RESULTS: The coefficient of variation (CoV), repeatability, and percent repeatability of automated cone density were slightly higher in patients with RP compared to age-matched normals, but showed no statistically significant difference. The standard deviation of CLS and cone spacing of nearest-neighbor distance demonstrated a statistically significant difference between good- and poor-quality images. CONCLUSIONS: Repeatability of automated cone density measurements in patients with RP is comparable to normals. Misidentification of cones due to image quality variability is a major limitation of automated cone counting algorithms in patients with RP. Our study suggests that CLS and cone spacing metrics could be used to help define image quality and, thus, increase confidence in automated cone counts in patients with RP. TRANSLATIONAL RELEVANCE: The novel AO image quality assessment metrics described in our study could help to improve patient image interpretation, prognosis, and longitudinal care.

Correlation of Outer Retinal Degeneration and Choriocapillaris Loss in Stargardt Disease Using En Face Optical Coherence Tomography and Optical Coherence Tomography Angiography.

PURPOSE: This study measured and correlated degeneration of the junction between the inner and outer segments (IS/OS), the retinal pigment epithelium (RPE), and the choriocapillaris (CC) in Stargardt disease (STGD). DESIGN: Prospective cross-sectional study. METHODS: This study was conducted at the Casey Eye Institute. A total of 23 patients with STGD were enrolled and underwent optical coherence tomography angiography (OCTA). Scans were centered on the fovea. OCT slab projections and en face boundary maps were used to create masks to measure total IS/OS loss or RPE atrophy as well as regions of isolated IS/OS loss, isolated RPE atrophy, and matched IS/OS and RPE degeneration or intact IS/OS junction and RPE. CC vascular density (CCVD) was quantified from the CC angiogram. Outcomes included the area of loss, and the CCVD of degeneration in different areas was quantified and correlated. RESULTS: The total area of IS/OS loss was strongly correlated with the total area of RPE atrophy (r = 0.96; P < 0.0001) by a 1.6:1 ratio (r2 = 0.90). CCVD within regions of matched degeneration (85.6% ± 2.7%; P < 0.0001), isolated IS/OS junction loss (93.6% ± 1.0%; P = 0.0011), and isolated RPE atrophy (94.1% ± 1.1%; P = 0.0065) were all significantly lower than normal (99.0% ± 0.17%). There was a trend for CCVD within intact areas (97.6% ± 0.38%) to decline as the area diminished (r = 0.68). CONCLUSIONS: Photoreceptor and RPE degeneration exhibited a strong relationship wherein the IS/OS loss was 1.6-fold greater than that of RPE atrophy, supporting the theory that photoreceptor degeneration precedes RPE in STGD. Both the photoreceptors and the RPE degeneration contributed synergistically to CCVD attenuation, but extralesional CCVD also tended to be abnormal. The findings and techniques in this study may be of utility in developing endpoints for clinical trials.

Longitudinal ophthalmic findings in a child with Helsmoortel-Van der Aa Syndrome.

PURPOSE: We present the first detailed ophthalmic description of a child with Helsmoortel-Van der Aa Syndrome (HVDAS), including longitudinal follow-up and analysis. OBSERVATIONS: After extensive workup, a young child with poor visual behavior, hypotonic cerebral palsy, intellectual disability, and global developmental delay was found to have a heterozygous de novo mutation in the ADNP gene and diagnosed with HVDAS. Ophthalmic findings were remarkable for progressive nystagmus, macular pigment mottling, mild foveal hypoplasia with abnormal macular laminations, persistent rod dysfunction with electronegative waveform, and progressive cone degeneration. CONCLUSIONS AND IMPORTANCE: Patients with HVDAS are known to have abnormal visual behavior due to refractive or cortical impairment. However, we present the first description, to our knowledge, of an association with retinal mal-development and degeneration. Thus, patients with HVDAS should be referred for ophthalmic genetics evaluation, and HVDAS should be on the differential diagnosis for young children with global developmental delay who present with nystagmus, rod and cone dysfunction with electronegative waveform, and relative lack of severe structural degeneration on optical coherence tomography.

Evidence of cardiac involvement in the fetal inflammatory response syndrome: disruption of gene networks programming cardiac development in nonhuman primates.

BACKGROUND: Most early preterm births are associated with intraamniotic infection and inflammation, which can lead to systemic inflammation in the fetus. The fetal inflammatory response syndrome describes elevations in the fetal interleukin-6 level, which is a marker for inflammation and fetal organ injury. An understanding of the effects of inflammation on fetal cardiac development may lead to insight into the fetal origins of adult cardiovascular disease. OBJECTIVE: The purpose of this study was to determine whether the fetal inflammatory response syndrome is associated with disruptions in gene networks that program fetal cardiac development. STUDY DESIGN: We obtained fetal cardiac tissue after necropsy from a well-described pregnant nonhuman primate model (pigtail macaque, Macaca nemestrina) of intrauterine infection (n=5) and controls (n=5). Cases with the fetal inflammatory response syndrome (fetal plasma interleukin-6 >11 pg/mL) were induced by either choriodecidual inoculation of a hypervirulent group B streptococcus strain (n=4) or intraamniotic inoculation of Escherichia coli (n=1). RNA and protein were extracted from fetal hearts and profiled by microarray and Luminex (Millipore, Billerica, MA) for cytokine analysis, respectively. Results were validated by quantitative reverse transcriptase polymerase chain reaction. Statistical and bioinformatics analyses included single gene analysis, gene set analysis, Ingenuity Pathway Analysis (Qiagen, Valencia, CA), and Wilcoxon rank sum. RESULTS: Severe fetal inflammation developed in the context of intraamniotic infection and a disseminated bacterial infection in the fetus. Interleukin-6 and -8 in fetal cardiac tissues were elevated significantly in fetal inflammatory response syndrome cases vs controls (P<.05). A total of 609 probe sets were expressed differentially (>1.5-fold change, P<.05) in the fetal heart (analysis of variance). Altered expression of select genes was validated by quantitative reverse transcriptase polymerase chain reaction that included several with known functions in cardiac injury, morphogenesis, angiogenesis, and tissue remodeling (eg, angiotensin I converting enzyme 2, STEAP family member 4, natriuretic peptide A, and secreted frizzled-related protein 4; all P<.05). Multiple gene sets and pathways that are involved in cardiac morphogenesis and vasculogenesis were downregulated significantly by gene set and Ingenuity Pathway Analysis (hallmark transforming growth factor beta signaling, cellular morphogenesis during differentiation, morphology of cardiovascular system; all P<.05). CONCLUSION: Disruption of gene networks for cardiac morphogenesis and vasculogenesis occurred in the preterm fetal heart of nonhuman primates with preterm labor, intraamniotic infection, and severe fetal inflammation. Inflammatory injury to the fetal heart in utero may contribute to the development of heart disease later in life. Development of preterm labor therapeutics must also target fetal inflammation to lessen organ injury and potential long-term effects on cardiac function.

Parafoveal cone abnormalities and recovery on adaptive optics in posterior uveitis.

PURPOSE: To determine if adaptive optics (AO) flood illumination imaging can detect subclinical changes in 4 cases of posterior uveitis affecting the outer retina. OBSERVATIONS: In all 4 cases, the affected eye showed altered areas in the photoreceptor mosaic on AO that corresponded to changes on other imaging modalities. Abnormalities not apparent on other imaging modalities were also noted. In one case of multifocal choroiditis with acute outer retinal atrophy, AO revealed decreased visualization of photoreceptors in the unaffected eye that was not noted on spectral domain-optical coherence tomography. In the patient with multiple evanescent white dot syndrome, focal photoreceptor abnormalities were more apparent on AO compared to other imaging modalities, and these areas normalized on AO during follow-up. Five weeks after initiation of high dose prednisone and azathioprine in a patient with serpiginous choroidopathy, AO images showed recovery in apparent parafoveal cone density. CONCLUSIONS AND IMPORTANCE: AO detects subclinical changes in the photoreceptor layer in posterior uveitis that can recover over time. AO may be useful in following outer retinal inflammatory conditions.

Interpretation of Flood-Illuminated Adaptive Optics Images in Subjects with Retinitis Pigmentosa.

The purpose of this study was to correlate features on flood-illuminated adaptive optics (AO) images with color fundus, fundus autofluorescence (FAF) and spectral domain optical coherence tomography (SD-OCT) images in patients with retinitis pigmentosa (RP). We imaged 39 subjects diagnosed with RP using the rtx1™ flood-illuminated AO camera from Imagine Eyes (Orsay, France). We observed a correlation between hyper-autofluoresence changes on FAF, disruption of the interdigitation zone (IZ) on SD-OCT and loss of reflective cone profiles on AO. Four main patterns of cone-reflectivity were seen on AO: presumed healthy cone mosaics, hypo-reflective blurred cone-like structures, higher frequency disorganized hyper-reflective spots, and lower frequency hypo-reflective spots. These regions were correlated to progressive phases of cone photoreceptor degeneration observed using SD-OCT and FAF. These results help provide interpretation of en face images obtained by flood-illuminated AO in subjects with RP. However, significant ambiguity remains as to what truly constitutes a cone, especially in areas of degeneration. With further refinements in technology, flood illuminated AO imaging has the potential to provide rapid, standardized, longitudinal and lower cost imaging in patients with retinal degeneration.

INSIGHTS INTO AUTOSOMAL DOMINANT STARGARDT-LIKE MACULAR DYSTROPHY THROUGH MULTIMODALITY DIAGNOSTIC IMAGING.

PURPOSE: Autosomal dominant Stargardt-like macular dystrophy is a rare juvenile macular dystrophy most commonly because of mutations in ELOVL4 and PROM1 genes. In this study, we review a series of cases of Stargardt-like macular dystrophy and use advanced imaging techniques to describe pathophysiologic manifestations. METHODS: A retrospective medical record review was performed for five patients from two families with ELOVL4 mutation and one patient with PROM1 mutation including reviewing diagnostic imaging, such as fundus photography, spectral domain optical coherence tomography, fundus autofluorescence, and adaptive optics flood-illuminated photography. RESULTS: All patients had reduced central visual acuity with varying degree of foveal atrophy. In the ELOVL4 group, best-corrected visual acuity ranged from 20/25 to 20/200. Early pathologic changes included thickening of the external limiting membrane and outer nuclear atrophy followed by retinal pigment epithelium loss in later stages. Adaptive optics imaging revealed photoreceptor loss even in early stages with good visual acuity. The PROM1 patient also had similar central vision loss with significant outer nuclear atrophy. In contrast to ELOVL4 mutation, there was more diffuse and patchy retinal pigment epithelium loss throughout the macula. CONCLUSION: Both ELOVL4- and PROM1-related maculopathies are characterized by progressive photoreceptor atrophy and central vision loss. Using advanced diagnostic imaging, early disease changes and disease progression can be characterized.

Assessment of Different Sampling Methods for Measuring and Representing Macular Cone Density Using Flood-Illuminated Adaptive Optics.

PURPOSE: To describe a standardized flood-illuminated adaptive optics (AO) imaging protocol suitable for the clinical setting and to assess sampling methods for measuring cone density. METHODS: Cone density was calculated following three measurement protocols: 50 × 50-µm sampling window values every 0.5° along the horizontal and vertical meridians (fixed-interval method), the mean density of expanding 0.5°-wide arcuate areas in the nasal, temporal, superior, and inferior quadrants (arcuate mean method), and the peak cone density of a 50 × 50-µm sampling window within expanding arcuate areas near the meridian (peak density method). Repeated imaging was performed in nine subjects to determine intersession repeatability of cone density. RESULTS: Cone density montages could be created for 67 of the 74 subjects. Image quality was determined to be adequate for automated cone counting for 35 (52%) of the 67 subjects. We found that cone density varied with different sampling methods and regions tested. In the nasal and temporal quadrants, peak density most closely resembled histological data, whereas the arcuate mean and fixed-interval methods tended to underestimate the density compared with histological data. However, in the inferior and superior quadrants, arcuate mean and fixed-interval methods most closely matched histological data, whereas the peak density method overestimated cone density compared with histological data. Intersession repeatability testing showed that repeatability was greatest when sampling by arcuate mean and lowest when sampling by fixed interval. CONCLUSIONS: We show that different methods of sampling can significantly affect cone density measurements. Therefore, care must be taken when interpreting cone density results, even in a normal population.

Sarpogrelate, a 5-HT2A Receptor Antagonist, Protects the Retina From Light-Induced Retinopathy.

PURPOSE: To determine if sarpogrelate, a selective 5-HT2A receptor antagonist, is protective against light-induced retinopathy in BALB/c mice. METHODS: BALB/c mice were dosed intraperitoneally with 5, 15, 30, 40, or 50 mg/kg sarpogrelate 48, 24, and 0 hours prior to bright light exposure (10,000 lux) as well as 24 and 48 hours after exposure. Additionally, a single injection regimen was evaluated by injecting mice with 50 mg/kg sarpogrelate once immediately prior to light exposure. To investigate the potential for additive effects of serotonin receptor agents, a combination therapy consisting of sarpogrelate (15 mg/kg) and 8-OH-DPAT (1 mg/kg) was evaluated with the 5-day treatment regimen. Neuroprotection was characterized by the preservation of retinal thickness and function, measured by spectral-domain optical coherence tomography (SD-OCT) and electroretinography (ERG), respectively. RESULTS: Mice that were light damaged and injected with saline had significantly reduced outer retinal thickness, total retinal thickness, and ERG amplitudes compared with naïve mice. A 5-day administration of 15, 30, or 40 mg/kg of sarpogrelate was able to partially protect retinal morphology and full protection of retinal morphology was achieved with a 50 mg/kg dose. Both 15 and 30 mg/kg doses of sarpogrelate partially preserved retinal function measured by ERG, whereas 40 and 50 mg/kg doses fully preserved retinal function. Additionally, a single administration of 50 mg/kg sarpogrelate was able to fully preserve both retinal morphology and function. Administration of 15 mg/kg of sarpogrelate and 1 mg/kg of 8-OH-DPAT together demonstrated an additive effect and fully preserved retinal morphology. CONCLUSIONS: A 5- or 1-day treatment with 50 mg/kg sarpogrelate can completely protect the retina of BALB/c mice from light-induced retinopathy. Partial protection can be achieved with lower doses starting at 15 mg/kg and protection increases in a dose-dependent manner. Treatment with low doses of sarpogrelate and 8-OH-DPAT elicits an additive effect that results in full protection of retinal morphology.

Hepatitis C virus core protein inhibits interferon production by a human plasmacytoid dendritic cell line and dysregulates interferon regulatory factor-7 and signal transducer and activator of transcription (STAT) 1 protein expression.

Plasmacytoid Dendritic Cells (pDCs) represent a key immune cell population in the defense against viruses. pDCs detect viral pathogen associated molecular patterns (PAMPs) through pattern recognition receptors (PRR). PRR/PAMP interactions trigger signaling events that induce interferon (IFN) production to initiate local and systemic responses. pDCs produce Type I and Type III (IFNL) IFNs in response to HCV RNA. Extracellular HCV core protein (Core) is found in the circulation in chronic infection. This study defined how Core modulates PRR signaling in pDCs. Type I and III IFN expression and production following exposure to recombinant Core or ß-galactosiade was assessed in human GEN2.2 cells, a pDC cell line. Core suppressed type I and III IFN production in response to TLR agonists and the HCV PAMP agonist of RIG-I. Core suppression of IFN induction was linked with decreased IRF-7 protein levels and increased non-phosphorylated STAT1 protein. Circulating Core protein interferes with PRR signaling by pDCs to suppress IFN production. Strategies to define and target Core effects on pDCs may serve to enhance IFN production and antiviral actions against HCV.

Rapid generation of a mouse model for Middle East respiratory syndrome.

In this era of continued emergence of zoonotic virus infections, the rapid development of rodent models represents a critical barrier to public health preparedness, including the testing of antivirus therapy and vaccines. The Middle East respiratory syndrome coronavirus (MERS-CoV) was recently identified as the causative agent of a severe pneumonia. Given the ability of coronavirus to rapidly adapt to new hosts, a major public health concern is that MERS-CoV will further adapt to replication in humans, triggering a pandemic. No small-animal model for this infection is currently available, but studies suggest that virus entry factors can confer virus susceptibility. Here, we show that mice were sensitized to MERS-CoV infection by prior transduction with adenoviral vectors expressing the human host-cell receptor dipeptidyl peptidase 4. Mice developed a pneumonia characterized by extensive inflammatory-cell infiltration with virus clearance occurring 6-8 d after infection. Clinical disease and histopathological changes were more severe in the absence of type-I IFN signaling whereas the T-cell response was required for virus clearance. Using these mice, we demonstrated the efficacy of a therapeutic intervention (poly I:C) and a potential vaccine [Venezuelan equine encephalitis replicon particles expressing MERS-CoV spike protein]. We also found little protective cross-reactivity between MERS-CoV and the severe acute respiratory syndrome-CoV. Our results demonstrate that this system will be useful for MERS-CoV studies and for the rapid development of relevant animal models for emerging respiratory viral infections.

Long-term characterization of retinal degeneration in rd1 and rd10 mice using spectral domain optical coherence tomography.

PURPOSE: We characterize the in vivo changes over time in the retinal structure of wild-type mice alongside two lines of mice deficient in the ß-subunit of phosphodiesterase (rd1 and rd10 mice) using spectral domain optical coherence tomography (SD-OCT). METHODS: SD-OCT images were obtained using the Bioptigen spectral domain ophthalmic imaging system (SDOIS). Wild-type C57BL/6J, rd1 and rd10 mice ranging in age from P14 to P206 were sedated with 1% isoflurane. Horizontal and vertical linear scans through the optic nerve, and annular scans around the optic nerve were obtained. RESULTS: SD-OCT imaging of wild-type mice demonstrated visibility of the inner segment/outer segment (IS/OS) junction, external limiting membrane (ELM), outer nuclear layer (ONL), and outer plexiform layer (OPL). At P14, most rd10 mice exhibited normal SD-OCT profiles, but some displayed changes in the IS/OS junction. At the same time point, rd1 mice had severe outer retinal degeneration. In rd10 mice, imaging revealed loss of the IS/OS junction by P18, hyperreflective changes in the ONL at P20, hyperreflective vitreous opacities, and shallow separation of the neural retina from the RPE. Retinal separations were not observed in rd1 mice. Segmentation analysis in wild-type mice demonstrated relatively little variability between animals, while in rd10 and rd1 mice there was a steady decline in outer retinal thickness. Histologic studies demonstrated correlation of retinal features with those seen on SD-OCT scans. Segmentation analysis provides a quantitative and reproducible method for measuring in vivo retinal changes in mice. CONCLUSIONS: SD-OCT provides a non-invasive method of following long-term retinal changes in mice in vivo. Although rd10 and rd1 mice have mutations in the same gene, they demonstrate significantly different features on SD-OCT.

Effects of the hepatitis C virus core protein on innate cellular defense pathways.

The hepatitis C virus (HCV) core protein is thought to contribute to HCV pathogenesis through its interaction with various signal transduction pathways. In this study, we explored the interaction of the core protein with innate defense pathways (interferon [IFN] regulatory factor [IRF], Jak-Stat, and inducible nitric oxide synthase [iNOS]) in HeLa and Huh7 human cell lines. Expression of a patient-derived genotype 1b core protein activated human IRF-1 and guanylate-binding protein-2 (GBP-2) promoters, induced IRF-1 mRNA, but failed to induce IRF-3 phosphorylation. HCV core protein caused dose-dependent induction of the IFN-beta promoter and IFN-beta mRNA but not the IFN-alpha1 and IFN-alpha4 promoters. In the presence of IFN-alpha, core expression was associated with increased IFN-stimulated gene factor 3 (ISGF3) binding to the IFN-stimulated response element (ISRE) and tyrosine phosphorylation of Stat1. Core expression resulted in dose-dependent activation of the ISRE and gamma activated sequence (GAS) promoters, in both the absence and the presence of either IFN-alpha or IFN-gamma. Core stimulated the human iNOS promoter and induced iNOS protein. The data indicate that HCV core can modulate IRF, Jak-Stat, and iNOS pathways and suggest mechanisms by which core could affect HCV persistence and pathogenesis.

Inactivation of the PKR protein kinase and stimulation of mRNA translation by the cellular co-chaperone P58(IPK) does not require J domain function.

P58(IPK) was discovered as an inhibitor of the interferon-induced, protein kinase, PKR. Upon virus infection, PKR can, as part of the host defense system, inhibit mRNA translation by phosphorylating the alpha subunit of protein synthesis eukaryotic initiation factor 2 (eIF-2alpha). We previously found that influenza virus recruits the cellular P58(IPK) co-chaperone to inhibit PKR activity and thus facilitate viral protein synthesis. P58(IPK) contains nine tetratricopeptide repeat (TPR) motifs in addition to the highly conserved J domain found in all DnaJ chaperone family members. To define the role of molecular chaperones in regulating cell growth in addition to PKR regulation, we performed a detailed analysis of the P58(IPK) J domain. Using growth rescue assays, we found that the P58(IPK) J domain substituted for the J domains of other DnaJ proteins, including DnaJ in Escherichia coli and Ydj1 in Saccharomyces cerevisiae. This is the first time a cellular J domain from a mammalian DnaJ family member was shown to be functional in both prokaryotic DnaJ and eukaryotic Ydj1 constructs. Furthermore, point mutations within the conserved HPD residue cluster of the P58(IPK) J domain disrupted P58(IPK) J function including stimulation of ATPase activity of Hsp70. However, the P58(IPK) HPD mutants still inhibited PKR activity and thus supported cell growth in a yeast rescue assay. Overexpression of the HPD mutants of P58(IPK), similar to their wild-type counterpart, also stimulated mRNA translation in a mammalian cell system. Taken together, our data necessitate a model of P58(IPK) inhibition of PKR kinase activity and stimulation of mRNA translation, which does not require classical J domain function found in the DnaJ molecular chaperone family.