Culture media affect sex after IVF treatment-a detailed analysis of explanatory variables.

PURPOSE: The purpose of this study was to provide a detailed analysis of clinical and laboratory factors associated with skewed secondary sex ratio (SSR) after ART. METHOD: Retrospective cohort study of embryos resulting in live births, from frozen and fresh single blastocyst transfers. Embryos were cultured in either G-TL (n = 686) or Sage media (n = 685). Data was analyzed using a multivariate logistic regression model and a mixed model analysis. RESULTS: Significantly more male singletons were born after culture in Sage media compared to G-TL media (odds ratio (OR) 1.34, 95% CI (1.05, 1.70), P = 0.02). Inner cell mass grade B vs A (OR 1.36 95% CI (1.05, 1.76), P = 0.02) and one previous embryo transfer (OR 1.49, 95% CI (1.03, 2.16), P = 0.03) were associated with a significantly higher probability of male child at birth. Factors associated with a reduced probability of male child were expansion grade 3 vs 5 (OR 0.66, 95% CI (10.45, 0.96), P = 0.03) and trophectoderm grade B vs A (OR 0.57, 95% CI (0.44, 0.74), P = 0.00). Male embryos developed significantly faster in Sage media compared to G-TL media for the stages of blastocyst (- 1.12 h, 95% CI (- 2.12, - 0.12)), expanded blastocyst (- 1.35 h, 95% CI (- 2.34, - 0.35)), and hatched blastocyst (- 1.75 h, 95% CI (- 2.99, - 0.52)). CONCLUSION: More male children were born after culture in Sage media compared to G-TL media. Male embryo development was affected by culture media. Our observations suggest that culture media impact male embryo quality selectively, thus potentially favoring the selection of male embryos.

Idiopathic early ovarian ageing: risk of miscarriage and chance of delivery following ART in a nationwide cohort study.

STUDY QUESTION: Is idiopathic reduced ovarian reserve in young women, quantified as low response to ovarian stimulation in ART, associated with a concomitant loss of oocyte quality as determined by risk of pregnancy loss and chance of clinical pregnancy and live birth? SUMMARY ANSWER: Young women with idiopathic accelerated loss of follicles exhibit a similar risk of pregnancy loss as young women with normal ovarian reserve. WHAT IS KNOWN ALREADY: Normal ovarian ageing is described as a concomitant decline in oocyte quantity and quality with increasing age. Conflicting results exist with regard to whether a similar decline in oocyte quality also follows an accelerated loss of follicles in young women. STUDY DESIGN, SIZE, DURATION: This national register-based, historical cohort study included treatment cycles from young women (≤37 years) after ART treatment in Danish public or private fertility clinics during the period 1995-2014. The women were divided into two groups dependent on their ovarian reserve status: early ovarian ageing (EOA) group and normal ovarian ageing (NOA) group. There were 2734 eligible cycles in the EOA group and 22 573 in the NOA group. Of those, 1874 (n = 1213 women) and 19 526 (n = 8814 women) cycles with embryo transfer were included for analyses in the EOA and NOA group, respectively. PARTICIPANTS/MATERIALS, SETTING, METHODS: EOA was defined as ≤5 oocytes harvested in both the first and second cycle stimulated with FSH. The NOA group should have had at least two FSH-stimulated cycles with ≥8 oocytes harvested in either the first or the second cycle. Cases with known causes influencing the ovarian reserve (endometriosis, ovarian surgery, polycystic ovary syndrome, chemotherapy, etc.) were excluded. The oocyte quality was evaluated by the primary outcome defined as the overall risk of pregnancy loss (gestational age (GA) ≤22 weeks) following a positive hCG and further stratified into: non-visualized pregnancy loss, early miscarriage (GA ≤ 12 weeks) and late miscarriage (GA > 12 weeks). Secondary outcomes were chance of clinical pregnancy and live birth per embryo transfer. Cox regression models were used to assess the risk of pregnancy loss. Time-to-event was measured from the day of embryo transfer from the second cycle and subsequent cycles. Logistic regression models were used to assess the chance of clinical pregnancy and live birth. MAIN RESULTS AND THE ROLE OF CHANCE: The overall risk of pregnancy loss for the EOA group was comparable with the NOA group (adjusted hazard ratio: 1.04, 95% CI: 0.86; 1.26). Stratifying by pregnancy loss types showed comparable risks in the EOA and NOA group. The odds of achieving a clinical pregnancy or live birth per embryo transfer was lower in the EOA group compared to the NOA group (adjusted odds ratio: 0.77 (0.67; 0.88) and 0.78 (0.67; 0.90), respectively). LIMITATIONS, REASONS FOR CAUTION: Only women with at least two ART cycles were included. We had no information on the total doses of gonadotropin administered in each cycle. WIDER IMPLICATIONS OF THE FINDINGS: The present findings may indicate that mechanism(s) other than aneuploidy may explain the asynchrony between the normal-for-age risk of miscarriage and the reduced chance of implantation found in our patients with EOA. The results of this study could be valuable when counselling young patients with low ovarian reserve. STUDY FUNDING/COMPETING INTERESTS(S): The study was funded by the Health Research Fund of Central Denmark Region. The authors have no conflict of interest to declare. TRIAL REGISTRATION NUMBER: N/A.

Early ovarian ageing: is a low number of oocytes harvested in young women associated with an earlier and increased risk of age-related diseases?

STUDY QUESTION: Do young women with early ovarian ageing (EOA), defined as unexplained, and repeatedly few oocytes harvested in ART have an increased risk of age-related events? SUMMARY ANSWER: At follow-up, women with idiopathic EOA had an increased risk of age-related events compared to women with normal ovarian ageing (NOA). WHAT IS KNOWN ALREADY: Early and premature menopause is associated with an increased risk of cardiovascular diseases (CVDs), osteoporosis and death. In young women, repeated harvest of few oocytes in well-stimulated ART cycles is a likely predictor of advanced menopausal age and may thus serve as an early marker of accelerated general ageing. STUDY DESIGN, SIZE, DURATION: A register-based national, historical cohort study. Young women (≤37 years) having their first ART treatment in a public or private fertility clinic during the period 1995-2014 were divided into two groups depending on ovarian reserve status: EOA (n = 1222) and NOA (n = 16 385). Several national registers were applied to assess morbidity and mortality. PARTICIPANTS/MATERIALS, SETTING, METHODS: EOA was defined as ≤5 oocytes harvested in a minimum of two FSH-stimulated cycles and NOA as ≥8 oocytes in at least one cycle. Cases with known causes influencing the ovarian reserve (endometriosis, ovarian surgery, polycystic ovary syndrome, chemotherapy etc.) were excluded. To investigate for early signs of ageing, primary outcome was an overall risk of ageing-related events, defined as a diagnosis of either CVD, osteoporosis, type 2 diabetes, cancer, cataract, Alzheimer's or Parkinson's disease, by death of any-cause as well as a Charlson comorbidity index score of ≥1 or by registration of early retirement benefit. Cox regression models were used to assess the risk of these events. Exposure status was defined 1 year after the first ART cycle to assure reliable classification, and time-to-event was measured from that time point. MAIN RESULTS AND THE ROLE OF CHANCE: Median follow-up time from baseline to first event was 4.9 years (10/90 percentile 0.7/11.8) and 6.4 years (1.1/13.3) in the EOA and NOA group, respectively. Women with EOA had an increased risk of ageing-related events when compared to women with a normal oocyte yield (adjusted hazard ratio 1.24, 95% CI 1.08 to 1.43). Stratifying on categories, the EOA group had a significantly increased risk for CVD (1.44, 1.19 to 1.75) and osteoporosis (2.45, 1.59 to 3.90). Charlson comorbidity index (1.15, 0.93 to 1.41) and early retirement benefit (1.21, 0.80 to 1.83) was also increased, although not reaching statistical significance. LIMITATIONS, REASONS FOR CAUTION: Cycles never reaching oocyte aspiration were left out of account in the inclusion process and we may therefore have missed women with the most severe forms of EOA. We had no information on the total doses of gonadotrophin administered in each cycle. WIDER IMPLICATIONS OF THE FINDINGS: These findings indicate that oocyte yield may serve as marker of later accelerated ageing when, unexpectedly, repeatedly few oocytes are harvested in young women. Counselling on life-style factors as a prophylactic effort against cardiovascular and other age-related diseases may be essential for this group of women. STUDY FUNDING/COMPETING INTEREST(S): No external funding was received for this study. All authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Elective embryo transfers on Day 6 reduce implantation compared with transfers on Day 5.

STUDY QUESTION: Is there a difference in pregnancy rates between embryos transferred electively on Day 5 and Day 6, respectively? SUMMARY ANSWER: The chance of pregnancy is significantly reduced (odds ratio (OR): 0.34; 95% CI 0.22-0.52) if transfer is performed on Day 6 compared with Day 5. WHAT IS KNOWN ALREADY: Several studies report that Day 5 transfers have higher implantation rates (IRs) when compared with Day 6 transfers. These studies were based on non-elective Day 6 transfers, where transfers on Day 6 were performed with developmentally delayed embryos. Traditionally, difference in IRs has therefore been explained by an impaired embryo quality. An alternative explanation is that endometrial receptivity is higher on Day 5 compared with Day 6. STUDY DESIGN, SIZE, DURATION: The study was conducted as a retrospective cohort follow-up study on single blastocyst transfers from February 2011 until August 2015 in patients aged <38 years, with ≥eight oocytes retrieved and no diagnosis of endometriosis. Non-elective Day 6 transfers were excluded. Post hoc power-calculations (two-sided level of significance 0.05, power of 0.80) indicate that 91 embryos were needed in each group to detect a reduction in IR (primary outcome) from 40 to 20%. PARTICIPANTS/MATERIALS, SETTING, METHODS: Day 5 or Day 6 transfers were implemented accordingly: from 2011 till 2013, transfers were performed on Day 6. If Day 6 was a Sunday, patients received Day 5 transfers. From 2013 onward, blastocysts were transferred on Day 5. If Day 5 was a Sunday, the transfer was delayed to Day 6. Univariable logistic regression analysis was performed to identify potential confounders. Factors with a P-value <0.1 were included in the multivariable logistic regression analysis. MAIN RESULTS AND THE ROLE OF CHANCE: We included 334 single elective Day 5 and 268 elective Day 6 transfers. The unadjusted odds for implantation between Day 5 and Day 6 groups were 0.35 (95% CI 0.25-0.49). A univariable logistic regression analysis identified maternal age, BMI, cumulative FSH dose, number of cryopreserved embryos, score of inner cell mass and trophectoderm and day of transfer as predictors of clinical pregnancy. When adjusting for these variables in a multivariable logistic regression analysis, the implantation odds for Day 5 transfer remained significantly higher than Day 6 (OR 0.34; 95% CI 0.22-0.52). LIMITATIONS, REASONS FOR CAUTION: The study was conducted on good prognosis patients. The majority of Day 6 transfers were performed in the beginning of the study period. Day 5 transfers were generally performed in the end of the study period. This difference in time of recruitment may cause a minor variation in the data but a subanalysis indicates that this potential variation is negligible. Day 5 scores were higher in the Day 5 transfer group. WIDER IMPLICATIONS OF THE FINDINGS: Based on the findings in this study, transfers should be performed on Day 5. If Day 5 transfers are logistically impossible to perform, it is be preferable to cryopreserve the blastocyst and transfer in another cycle on Day 5, as Day 6 transfers should be avoided. STUDY FUNDING/COMPETING INTEREST(S): None.

Timing of human preimplantation embryonic development is confounded by embryo origin.

STUDY QUESTION: To what extent do patient- and treatment-related factors explain the variation in morphokinetic parameters proposed as embryo viability markers? SUMMARY ANSWER: Up to 31% of the observed variation in timing of embryo development can be explained by embryo origin, but no single factor elicits a systematic influence. WHAT IS KNOWN ALREADY: Several studies report that culture conditions, patient characteristics and treatment influence timing of embryo development, which have promoted the perception that each clinic must develop individual models. Most of the studies have, however, treated embryos from one patient as independent observations, and only very few studies that evaluate the influence from patient- and treatment-related factors on timing of development or time-lapse parameters as predictors of viability have controlled for confounding, which implies a high risk of overestimating the statistical significance of potential correlations. STUDY DESIGN, SIZE, DURATION: Infertile patients were prospectively recruited to a cohort study at a hospital fertility clinic from February 2011 to May 2013. Patients aged <38 years without endometriosis were eligible if ≥8 oocytes were retrieved. Patients were included only once. All embryos were monitored for 6 days in a time-lapse incubator. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 1507 embryos from 243 patients were included. The influence of fertilization method, BMI, maternal age, FSH dose and number of previous cycles on timing of t2-t5, duration of the 2- and 3-cell stage, and development of a blastocoel (tEB) and full blastocoel (tFB) was tested in multivariate, multilevel linear regression analysis. Predictive parameters for live birth were tested in a logistic regression analysis for 223 single transferred blastocysts, where time-lapse parameters were investigated along with patient and embryo characteristics. MAIN RESULTS AND THE ROLE OF CHANCE: Moderate intra-class correlation coefficients (0.16-0.31) were observed for all parameters except duration of the 3-cell stage, which demonstrates that embryos from one patient elicit clustering at a patient level. No single patient- and treatment-related factor was found to systematically influence the timing from cleavage to blastocyst stage, which indicates that no individual patient-related factor can be identified that separately explains the clustering throughout the entire developmental stages. The blastocyst parameters were more affected by patient-related factors than cleavage stage parameters, as tEB occurred significantly later with older age (0.29 h/year (95% confidence interval: CI 0.03; 0.56)), while both tEB and tFB occurred significantly later with increasing dose of FSH (tEB: 0.12 h/100 IU FSH (95% CI 0.01;0.24); tFB 0.14 h/100 IU FSH (95% CI 0.03;0.27)) and with more previous attempts (tEB: 1.2 h/attempt (95% CI 0.01;2.5); tFB 1.4 h/attempt (0.10;2.7)). Fertilization method affected timing of the first division, with ICSI embryos cleaving significantly faster than IVF embryos (-3.6% (95% CI -6.4; -0.77)), whereas no difference was found in the subsequent divisions. The univariable regression analysis identified female age, cumulative FSH dose, degree of blastocyst expansion, score of the inner cell mass and timing of full blastocyst formation as predictors of live birth. The timing of full blastocyst formation (tFB) did not remain significant when adjusting for age, number of previous cycles and cumulative FSH dose, which were the parameters shown to influence tFB in the mixed regression model. LIMITATIONS, REASONS FOR CAUTION: Only good prognosis patients were enrolled, so these results may not be generalized to all infertile women. Not all patient-related factors were investigated. WIDER IMPLICATIONS OF THE FINDINGS: Our findings underline the importance of treating embryos as dependent observations and suggest a high risk of patient-based confounding in retrospective studies. The impact of confounders and the embryo origin needs to be addressed in order to apply appropriate statistical models in observational studies. Furthermore, this observation emphasizes the need for RCTs for evaluating use of time-lapse parameters for embryo selection. STUDY FUNDING/COMPETING INTERESTS: Funding for the cohort study was provided by the Lippert Foundation, the Toyota Foundation, the Aase og Einar Danielsen foundation and NordicInfu Care research grant. Research at the Fertility Clinic, Aarhus University Hospital is supported by an unrestricted grant from MSD and Ferring. K.K. is funded by a grant from the Danish Council for Independent Research Medical Sciences. The authors declare no competing interest.

Nuclear magnetic resonance metabolomic profiling of Day 3 and 5 embryo culture medium does not predict pregnancy outcome in good prognosis patients: a prospective cohort study on single transferred embryos.

STUDY QUESTION: Does the metabolomic profile, obtained with nuclear magnetic resonance (NMR), of spent culture media from human embryos correlate with reproductive potential in a cohort of good prognosis patients? SUMMARY ANSWER: In a large cohort of single transferred blastocysts from a homogeneous group of good prognosis patients, we find a high degree of individual variation in the metabolome that, however, has no relation to pregnancy outcome. WHAT IS KNOWN ALREADY: Differences among various specific metabolites have been linked to reproductive potential. Although results from retrospective near infrared (NIR) spectroscopy analyses of spent culture medias from transferred embryos were promising, randomized controlled trials were unable to demonstrate that NIR analysis improved pregnancy rates. Therefore, a more detailed investigation of the relation between embryo metabolism and reproductive potential is required. NMR is a powerful technique that provides detailed structural and dynamic information. STUDY DESIGN, SIZE, DURATION: A prospective cohort study was conducted at the Fertility Clinic, Aarhus University Hospital between February 2011 and July 2012. Infertile patients aged <38 years without endometriosis were offered participation and their embryos were included if greater than or equal to eight oocytes were retrieved. In total, 161 infertile patients were included in the cohort. PARTICIPANTS/MATERIALS, SETTING, METHODS: Spent culture media was collected on Days 3 and 5 after oocyte retrieval from 148 single transferred embryos. NMR spectra were obtained from 12 µl of spent media. Data were quantitatively analysed using multivariate analysis with respect to pregnancy outcome, defined as a live fetus by ultrasound in gestational Week 8, along with patient and treatment related variables such as embryo score, age, BMI, fertilization method and cause of infertility. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 148 cycles were included in the analysis [embryo transfer cancelled (n = 12), no media collected (n = 1)]. Clinical pregnancy was confirmed in 47 patients (32%). We obtained high quality NMR spectra for 141 Day 3 and 137 Day 5 samples. Our spectra show a high degree of individual variation. Multivariate data analysis was performed on spectral data with several different pre-processing combinations, i.e. binning, alignment, normalization and scaling in the attempt to develop a valid prediction model. Different strategies of multivariate analysis showed, however, no correlation between the NMR profiles and pregnancy outcome, patient or treatment characteristics. No model could therefore be developed for prediction of pregnancy outcome. We conclude that within this group of good prognosis patients, large-scale metabolic variations between embryos detected with NMR have no apparent association with pregnancy outcome. LIMITATIONS, REASONS FOR CAUTION: Although this study is the largest we know of using NMR to investigate metabolomic profiles of single-transferred embryos, there may be differences that would be detected with a larger study. When analysing such a small sample volume, even small variations in the amount of media and dilution may introduce a large uncertainty in the results. WIDER IMPLICATIONS OF THE FINDINGS: Our study questions the usefulness of the entire metabolome for embryo selection, which should direct the search for viability markers in the culture media towards individual components. STUDY FUNDING/COMPETING INTERESTS: Funding was provided by Aarhus University, the Lippert Foundation, the Toyota Foundation, the Aase og Einar Danielsen foundation. Research at the Fertility Clinic, Aarhus Universtity Hospital is supported by an unrestricted grant from MSD and Ferring. The authors declare no competing interest. TRIAL REGISTRATION NUMBER: NCT01139268.

Time-lapse parameters as predictors of blastocyst development and pregnancy outcome in embryos from good prognosis patients: a prospective cohort study.

STUDY QUESTION: Do early time-lapse parameters predict which embryos will develop to high-quality blastocysts and does timing of development differ between embryos that implant and those that do not. SUMMARY ANSWER: Development to high-quality blastocysts could be predicted within the first 48 h of culture, whereas time-lapse parameters could not predict pregnancy. WHAT IS KNOWN ALREADY: Historical cohort studies on embryos from unselected groups of patients have suggested several putative kinetic markers of viability. Before well-designed randomized studies can be conducted, relevant selection models based on solid data must be developed. So far conclusions from the previous studies are ambiguous. STUDY DESIGN, SIZE, DURATION: A prospective cohort study conducted from February 2011 to June 2012. A total of 571 ICSI embryos from 92 patients were included in the blastocyst development analysis and 84 single embryo transfers were included in the pregnancy outcome analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: Embryos from women aged <38 years, with no endometriosis and ≥ 8 oocytes retrieved. University affiliated clinic. Embryos were cultured in a time-lapse incubator till Day 6. Logistic regression analysis was performed with variables selected based on indication. MAIN RESULTS AND THE ROLE OF CHANCE: Duration of the first cytokinesis, duration of the 3-cell stage and direct cleavage to 3-cells predicted development to high-quality blastocyst. We found no difference in timing between implanted and non-implanted embryos. LIMITATIONS, REASONS FOR CAUTION: A larger study might detect differences in timing between implanted and non-implanted embryos. The cohort consisted of good prognosis patients only and may not be representative of the entire IVF population. WIDER IMPLICATIONS OF THE FINDINGS: Our results in context with the lack of consistency in previous studies and the presumed influences of different external factors indicate that a universal algorithm for optimal timing of development might not be feasible. The apparent negative significance of division patterns that differ from the expected may imply that time-lapse will facilitate de-selection of embryos. STUDY FUNDING/COMPETING INTEREST(S): Funding for the present study was provided by Aarhus University, the Lippert Foundation, the Toyota Foundation, the Aase og Einar Danielsen foundation and by an unrestricted grant from MSD and Ferring. The authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: The study was registered at ClinicalTrial.gov with accession number NCT01139268.

SorCS3 does not require propeptide cleavage to bind nerve growth factor.

The functional properties of the Vps10p-domain receptor SorCS3 are undescribed. Here, we examine its processing and sorting in cellular transfectants, and analyze the binding of potential ligands to the purified receptor. We show that SorCS3 is synthesized as a proprotein and converted to its mature form by N-terminal propeptide cleavage in distal Golgi compartments. The propeptide is not a requirement for normal processing of the receptor and does not prevent ligands from binding to the SorCS3 precursor form. Expression of wt and chimeric receptors further suggests that SorCS3 predominates on the plasma membrane, exhibits slow internalization and does not engage in intracellular trafficking. SorCS3 emerges as a new neurotrophin binding Vps10p-domain receptor functionally distinct from its relatives Sortilin and SorLA.

Poliovirus 3A protein limits interleukin-6 (IL-6), IL-8, and beta interferon secretion during viral infection.

During viral infections, the host secretory pathway is crucial for both innate and acquired immune responses. For example, the export of most proinflammatory and antiviral cytokines, which recruit lymphocytes and initiate antiviral defenses, requires traffic through the host secretory pathway. To investigate potential effects of the known inhibition of cellular protein secretion during poliovirus infection on pathogenesis, cytokine secretion from cells infected with wild-type virus and with 3A-2, a mutant virus carrying an insertion in viral protein 3A which renders the virus defective in the inhibition of protein secretion, was tested. We show here that cells infected with 3A-2 mutant virus secrete greater amounts of cytokines interleukin-6 (IL-6), IL-8, and beta interferon than cells infected with wild-type poliovirus. Increased cytokine secretion from the mutant-infected cells can be attributed to the reduced inhibition of host protein secretion, because no significant differences between 3A-2- and wild-type-infected cells were observed in the inhibition of viral growth, host cell translation, or the ability of wild-type- or 3A-2-infected cells to support the transcriptional induction of beta interferon mRNA. We surmise that the wild-type function of 3A in inhibiting ER-to-Golgi traffic is not required for viral replication in tissue culture but, by altering the amount of secreted cytokines, could have substantial effects on pathogenesis within an infected host. The global inhibition of protein secretion by poliovirus may reflect a general mechanism by which pathogens that do not require a functional protein secretory apparatus can reduce the native immune response and inflammation associated with infection.

Oligomeric structures of poliovirus polymerase are important for function.

Central to the replication of poliovirus and other positive-strand RNA viruses is the virally encoded RNA-dependent RNA polymerase. Previous biochemical studies have suggested that direct polymerase- polymerase interactions might be important for polymerase function, and the structure of poliovirus polymerase has revealed two regions of extensive polymerase-polymerase interaction. To explore potential functional roles for the structurally observed polymerase-polymerase interactions, we have performed RNA binding and extension studies of mutant polymerase proteins in solution, disulfide cross-linking studies, mutational analyses in cells, in vitro activity analyses and RNA substrate modeling studies. The results of these studies indicate that both regions of polymerase-polymerase interaction observed in the crystals are indeed functionally important and, furthermore, reveal specific functional roles for each. One of the two regions of interaction provides for efficient substrate RNA binding and the second is crucial for forming catalytic sites. These studies strongly support the hypothesis that the polymerase- polymerase interactions discovered in the crystal structure provide an exquisitely detailed structural context for poliovirus polymerase function and for poliovirus RNA replication in cells.

MHC I-dependent antigen presentation is inhibited by poliovirus protein 3A.

The effects of poliovirus 3A protein expression and poliovirus infection on the presentation of hepatitis C virus antigens in cultured chimpanzee cells were examined. Expression of poliovirus 3A protein inhibits protein secretion when expressed in isolation and was sufficient to protect chimpanzee cells from lysis by hepatitis C virus-specific cytotoxic T cells in standard (51)Cr-release assays. Poliovirus infection also inhibited antigen presentation, as determined by decreased cytotoxic T cell activation. A mutation in 3A that abrogates the inhibition of protein secretion also abolished the effects of poliovirus on antigen presentation. These results demonstrate that the inhibition of secretion observed in poliovirus-infected cells substantially reduces the presentation of new antigens on the cell surface. These observations may reflect a general mechanism by which nonenveloped viruses such as poliovirus and other viruses that do not require a functional protein secretory apparatus can evade detection by the cellular immune response.

Remodeling the endoplasmic reticulum by poliovirus infection and by individual viral proteins: an autophagy-like origin for virus-induced vesicles.

All positive-strand RNA viruses of eukaryotes studied assemble RNA replication complexes on the surfaces of cytoplasmic membranes. Infection of mammalian cells with poliovirus and other picornaviruses results in the accumulation of dramatically rearranged and vesiculated membranes. Poliovirus-induced membranes did not cofractionate with endoplasmic reticulum (ER), lysosomes, mitochondria, or the majority of Golgi-derived or endosomal membranes in buoyant density gradients, although changes in ionic strength affected ER and virus-induced vesicles, but not other cellular organelles, similarly. When expressed in isolation, two viral proteins of the poliovirus RNA replication complex, 3A and 2C, cofractionated with ER membranes. However, in cells that expressed 2BC, a proteolytic precursor of the 2B and 2C proteins, membranes identical in buoyant density to those observed during poliovirus infection were formed. When coexpressed with 2BC, viral protein 3A was quantitatively incorporated into these fractions, and the membranes formed were ultrastructurally similar to those in poliovirus-infected cells. These data argue that poliovirus-induced vesicles derive from the ER by the action of viral proteins 2BC and 3A by a mechanism that excludes resident host proteins. The double-membraned morphology, cytosolic content, and apparent ER origin of poliovirus-induced membranes are all consistent with an autophagic origin for these membranes.