Human annexin A6 interacts with influenza a virus protein M2 and negatively modulates infection

Copyright © 2012, American Society for Microbiology. All Rights ReservedThe influenza A virus M2 ion channel protein has the longest cytoplasmic tail (CT) among the three viral envelope proteins and is well conserved between different viral strains. It is accessible to the host cellular machinery after fusion with the endosomal membrane and during the trafficking, assembly, and budding processes. We hypothesized that identification of host cellular interactants of M2 CT could help us to better understand the molecular mechanisms regulating the M2-dependent stages of the virus life cycle. Using yeast two-hybrid screening with M2 CT as bait, a novel interaction with the human annexin A6 (AnxA6) protein was identified, and their physical interaction was confirmed by coimmunoprecipitation assay and a colocalization study of virus-infected human cells. We found that small interfering RNA (siRNA)-mediated knockdown of AnxA6 expression significantly increased virus production, while its overexpression could reduce the titer of virus progeny, suggesting a negative regulatory role for AnxA6 during influenza A virus infection. Further characterization revealed that AnxA6 depletion or overexpression had no effect on the early stages of the virus life cycle or on viral RNA replication but impaired the release of progeny virus, as suggested by delayed or defective budding events observed at the plasma membrane of virus-infected cells by transmission electron microscopy. Collectively, this work identifies AnxA6 as a novel cellular regulator that targets and impairs the virus budding and release stages of the influenza A virus life cycle.This work was supported by the Research Fund for the Control of Infectious Disease (project 09080892) of the Hong Kong Government, the Area of Excellence Scheme of the University Grants Committee (grant AoE/M-12/-06 of the Hong Kong Special Administrative Region, China), the French Ministry of Health, the RESPARI Pasteur Network

Endogenous antigen processing drives the primary CD4+ T cell response to influenza.

By convention, CD4+ T lymphocytes recognize foreign and self peptides derived from internalized antigens in combination with major histocompatibility complex class II molecules. Alternative pathways of epitope production have been identified, but their contributions to host defense have not been established. We show here in a mouse infection model that the CD4+ T cell response to influenza, critical for durable protection from the virus, is driven principally by unconventional processing of antigen synthesized within the infected antigen-presenting cell, not by classical processing of endocytosed virions or material from infected cells. Investigation of the cellular components involved, including the H2-M molecular chaperone, the proteasome and γ-interferon-inducible lysosomal thiol reductase revealed considerable heterogeneity in the generation of individual epitopes, an arrangement that ensures peptide diversity and broad CD4+ T cell engagement. These results could fundamentally revise strategies for rational vaccine design and may lead to key insights into the induction of autoimmune and anti-tumor responses

Macroautophagy in Dendritic Cells Controls the Homeostasis and Stability of Regulatory T Cells.

Regulatory T cells (Tregs) play a crucial role in controlling autoimmune and inflammatory responses. Recent studies have demonstrated that dendritic cells (DCs) contribute to the homeostasis of peripheral Tregs. Autophagy, a critical pathway for cellular homeostasis, is active in DCs and is upregulated in different inflammatory conditions. We have shown that Tregs are expanded and have phenotypic alterations and impaired suppressive functions in mice with autophagy-deficient DCs. RNA profiling of Tregs revealed that autophagy in DCs is required to stabilize Treg expression signatures. This phenotype is linked to the downregulation of ICOS-Ligand expression in autophagy-deficient DCs, a consequence of the accumulation of ADAM10, the metalloproteinase responsible for its cleavage. Upon inflammation, in antigen-induced arthritis, mice with autophagy-deficient DCs exhibit increased synovial inflammation and cartilage and bone erosion correlating with Treg-to-Th17 conversion. Our data reveal a mechanism that couples autophagy deficiency in DCs to the function, homeostasis, and stability of Tregs

A Comparative Study of Human TLR 7/8 Stimulatory Trimer Compositions in Influenza A Viral Genomes

Background: Variation in the genomes of single-stranded RNA viruses affects their infectivity and pathogenicity in two ways. First, viral genome sequence variations lead to changes in viral protein sequences and activities. Second, viral genome sequence variation produces diversity at the level of nucleotide composition and diversity in the interactions between viral RNAs and host toll-like receptors (TLRs). A viral genome-typing method based on this type of diversity has not yet been established. Methodology/Principal Findings: In this study, we propose a novel genomic trait called the ‘‘TLR stimulatory trimer composition’ ’ (TSTC) and two quantitative indicators, Score S and Score N, named ‘‘TLR stimulatory scores’ ’ (TSS). Using the complete genome sequences of 10,994 influenza A viruses (IAV) and 251 influenza B viruses, we show that TSTC analysis reveals the diversity of Score S and Score N among the IAVs isolated from various hosts. In addition, we show that low values of Score S are correlated with high pathogenicity and pandemic potential in IAVs. Finally, we use Score S and Score N to construct a logistic regression model to recognize IAV strains that are highly pathogenic or have high pandemic potential. Conclusions/Significance: Results from the TSTC analysis indicate that there are large differences between human and avian IAV genomes (except for segment 3), as illustrated by Score S. Moreover, segments 1, 2, 3 and 4 may be majo

Baculovirus Infection Triggers a Shift from Amino Acid Starvation-Induced Autophagy to Apoptosis

Autophagy plays a central role in regulating important cellular functions such as cell survival during starvation and control of infectious pathogens. On the other hand, many pathogens have evolved mechanisms of inhibition of autophagy such as blockage of the formation of autophagosomes or the fusion of autophagosomes with lysosomes. Baculoviruses are important insect pathogens for pest control, and autophagy activity increases significantly during insect metamorphosis. However, it is not clear whether baculovirus infection has effects on the increased autophagy. In the present study, we investigated the effects of the Autographa californica nucleopolyhedrovirus (AcMNPV) infection on autophagy in SL-HP cell line from Spodoptera litura induced under amino acid deprivation. The results revealed that AcMNPV infection did not inhibit autophagy but triggered apoptosis under starvation pressure. In the early stage of infection under starvation, mitochondrial dysfunction was detected, suggesting the organelles might be involved in cell apoptosis. The semi-quantitative PCR assay revealed that the expression of both p35 and ie-1 genes of AcMNPV had no significant difference between the starved and unstarved SL-HP cells. The western blot analysis showed that no cleavage of endogenous Atg6 occurred during the process of apoptosis in SL-HP cells. These data demonstrated that some permissive insect cells may defend baculovirus infection via apoptosis under starvation and apoptosis is independent of the cleavage of Atg6 in SL-HP cells

Parenting Culture(s): Ideal-Parent Beliefs Across 37 Countries

What is it to be “an ideal parent”? Does the answer differ across countries and social classes? To answer these questions in a way that minimizes bias and ethnocentrism, we used open-ended questions to explore ideal-parent beliefs among 8,357 mothers and 3,517 fathers from 37 countries. Leximancer Semantic Network Analysis was utilized to first determine parenting culture zones (i.e., countries with shared ideal-parent beliefs) and then extract the predominant themes and concepts in each culture zone. The results yielded specific types of ideal-parent beliefs in five parenting culture zones: being “responsible and children/family-focused” for Asian parents, being “responsible and proper demeanor-focused” for African parents, and being “loving and responsible” for Hispanic-Italian parents. Although the most important themes and concepts were the same in the final two zones—being “loving and patient,” there were subtle differences: English-speaking, European Union, and Russian parents emphasized “being caring,” while French-speaking parents valued “listening” or being “present.” Ideal-parent beliefs also differed by education levels within culture zones, but no general pattern was discerned across culture zones. These findings suggest that the country in which parents were born cannot fully explain their differences in ideal-parent beliefs and that differences arising from social class or education level cannot be dismissed. Future research should consider how these differences affect the validity of the measurements in question and how they can be incorporated into parenting intervention research within and across cultures

Parental Burnout Around the Globe: a 42-Country Study

High levels of stress in the parenting domain can lead to parental burnout, a condition that has severe consequences for both parents and children. It is not yet clear, however, whether parental burnout varies by culture, and if so, why it might do so. In this study, we examined the prevalence of parental burnout in 42 countries (17,409 parents; 71% mothers; M_{age} = 39.20) and showed that the prevalence of parental burnout varies dramatically across countries. Analyses of cultural values revealed that individualistic cultures, in particular, displayed a noticeably higher prevalence and mean level of parental burnout. Indeed, individualism plays a larger role in parental burnout than either economic inequalities across countries, or any other individual and family characteristic examined so far, including the number and age of children and the number of hours spent with them. These results suggest that cultural values in Western countries may put parents under heightened levels of stress

Profiles of Parental Burnout Around the Globe: Similarities and Differences Across 36 Countries

Parental burnout (PB) is a pervasive phenomenon. Parenting is embedded in cultural values, and previous research has shown the role of individualism in PB. In this paper, we reanalyze previously collected data to identify profiles based on the four dimensions of PB, and explore whether these profiles vary across countries’ levels of collectivistic-individualistic (COL-IND) values. Our sample comprised 16,885 individuals from 36 countries (73% women; 27% men), and we used a latent profile approach to uncover PB profiles. The findings showed five profiles: Fulfilled, Not in PB, Low risk of PB, High risk of PB and Burned out. The profiles pointed to climbing levels of PB in the total sample and in each of the three country groups (High COL/Low IND, Medium COL-IND, Low COL/High IND). Exploratory analyses revealed that distinct dimensions of PB had the most prominent roles in the climbing pattern, depending on the countries’ levels of COL/IND. In particular, we found contrast to be a hallmark dimension and an indicator of severe burnout for individualistic countries. Contrary to our predictions, emotional distance and saturation did not allow a clear differentiation across collectivistic countries. Our findings support several research avenues regarding PB measurement and intervention