scholarly journals MHC Variants Associated With Symptomatic Versus Asymptomatic SARS-CoV-2 Infection in Highly Exposed Individuals

2021 ◽  
Vol 12 ◽  
Author(s):  
Erick C. Castelli ◽  
Mateus V. de Castro ◽  
Michel S. Naslavsky ◽  
Marilia O. Scliar ◽  
Nayane S. B. Silva ◽  
...  
Keyword(s):  
Immune Modulation ◽  
Genetic Factors ◽  
Nk Cell ◽  
Asymptomatic Group ◽  
Whole Exome ◽  
Antigen Presentation Pathway ◽  
Presentation Pathway ◽  
Previous Infection ◽  
Discordant Couples ◽  
Number Of Individuals

Despite the high number of individuals infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who develop coronavirus disease 2019 (COVID-19) symptoms worldwide, many exposed individuals remain asymptomatic and/or uninfected and seronegative. This could be explained by a combination of environmental (exposure), immunological (previous infection), epigenetic, and genetic factors. Aiming to identify genetic factors involved in immune response in symptomatic COVID-19 as compared to asymptomatic exposed individuals, we analyzed 83 Brazilian couples where one individual was infected and symptomatic while the partner remained asymptomatic and serum-negative for at least 6 months despite sharing the same bedroom during the infection. We refer to these as “discordant couples”. We performed whole-exome sequencing followed by a state-of-the-art method to call genotypes and haplotypes across the highly polymorphic major histocompatibility complex (MHC) region. The discordant partners had comparable ages and genetic ancestry, but women were overrepresented (65%) in the asymptomatic group. In the antigen-presentation pathway, we observed an association between HLA-DRB1 alleles encoding Lys at residue 71 (mostly DRB1*03:01 and DRB1*04:01) and DOB*01:02 with symptomatic infections and HLA-A alleles encoding 144Q/151R with asymptomatic seronegative women. Among the genes related to immune modulation, we detected variants in MICA and MICB associated with symptomatic infections. These variants are related to higher expression of soluble MICA and low expression of MICB. Thus, quantitative differences in these molecules that modulate natural killer (NK) activity could contribute to susceptibility to COVID-19 by downregulating NK cell cytotoxic activity in infected individuals but not in the asymptomatic partners.

scholarly journals “Immunogenetics of resistance to SARS-CoV-2 infection in discordant couples”

2021 ◽  
Author(s):  
Erick C. Castelli ◽  
Mateus V. de Castro ◽  
Michel S. Naslavsky ◽  
Marilia O. Scliar ◽  
Nayane S. B. Silva ◽  
...  
Keyword(s):  
Immune Modulation ◽  
Nk Cell ◽  
Kir Genes ◽  
Whole Exome ◽  
Previous Infection ◽  
Discordant Couples ◽  
Infection Resistance ◽  
A Minor ◽  
Number Of Individuals ◽  
Ancestry Proportions

AbstractBackgroundDespite the high number of individuals infected by SARS-CoV-2 who develop COVID-19 symptoms worldwide, many exposed individuals remain asymptomatic and/or stay uninfected. This could be explained by a combination of environmental (exposure, previous infection), epigenetic, and genetic factors. Aiming to identify genetic variants involved in SARS-CoV-2 resistance, we analyzed 86 discordant Brazilian couples where one was infected and symptomatic while the partner remained asymptomatic and seronegative despite sharing the same bedroom during the infection. The discordant partners had comparable ages, and genetic ancestry proportions.MethodsWhole-exome sequencing followed by a state-of-the-art method to call genotypes and haplotypes across the highly polymorphic MHC and LRC.ResultsWe observed a minor impact in antigen-presentation genes and KIR genes associated with resistance. Interestingly, genes related to immune modulation, mainly involved in NK cell killing activation/inhibition harbor variants potentially contributing to infection resistance. We hypothesize that individuals prone to produce higher amounts of MICA (possibly soluble), LILRB1, LILRB2, and low amounts of MICB, would be more susceptible to infection.ConclusionAccording to this hypothesis, quantitative differences in these NK activity-related molecules could contribute to resistance to COVID-19 down regulating NK cell cytotoxic activity in infected individuals but not in resistant partners.

scholarly journals H2-M and H2-O as Targeting Vehicles for the MHC Class II Processing Compartment Promote Antigen-Specific CD4+ T Cell Activation

Vaccines ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1053
Author(s):  
Lucia Lapazio ◽  
Monika Braun ◽  
Kaj Grandien
Keyword(s):  
T Cell ◽  
Mhc Class Ii ◽  
T Cell Activation ◽  
Cell Activation ◽  
Class Ii ◽  
Cd4 T Cell ◽  
Antigen Presentation Pathway ◽  
Presentation Pathway ◽  
Class Ii Antigen ◽  
Mhc Class Ii Antigen

CD8 and CD4 T cell activation are both required for a strong and long-lasting T cell immune response. Endogenously expressed proteins are readily processed by the MHC class I antigen presentation pathway, enabling activation of CD8+ T cells. However, the MHC class II antigen presentation pathway, necessary for CD4+ T cell activation, is generally not sufficiently accessible to endogenously expressed proteins, limiting the efficiency of mRNA- or DNA-based vaccines. In the current study, we have evaluated the feasibility of using antigen sequences fused to sequences derived from the H2-M and H2-O proteins, two complexes known to participate in MHC class II antigen processing, for the enhancement of CD4 T-cell activation. We analyzed T cell activation after genetic immunization with mRNA-encoding fusion proteins with the model antigen ovalbumin and sequences derived from H2-M or H2-O. Our results show that H2-M- or H2-O-derived sequences robustly improve antigen-specific CD4 T-cell activation when fused to the antigen of interest and suggest that the approach could be used to improve the efficiency of mRNA- or DNA-based vaccines.

scholarly journals The self-peptide repertoire plays a critical role in transplant tolerance induction

2020 ◽  
Author(s):  
Eric T. Son ◽  
Pouya Faridi ◽  
Moumita Paul-Heng ◽  
Mario Leong ◽  
Kieran English ◽  
...  
Keyword(s):  
T Cells ◽  
Critical Role ◽  
Tolerance Induction ◽  
Genetically Engineered ◽  
Solid Organ ◽  
Transplant Tolerance ◽  
Mhc I ◽  
Definitive Evidence ◽  
Antigen Presentation Pathway ◽  
Presentation Pathway

AbstractWhile direct allorecognition underpins both solid organ allograft rejection and tolerance induction, the specific molecular targets of most directly-alloreactive CD8+T cells have not been defined. In this study, we used a combination of genetically-engineered MHC I constructs, mice with a hepatocyte-specific mutation in the class I antigen-presentation pathway and immunopeptidomic analysis to provide definitive evidence for the contribution of the peptide cargo of allogeneic MHC I molecules to transplant tolerance induction. We established a systematic approach for the discovery of directly-recognised pMHC epitopes, and identified 17 strongly immunogenic H-2Kb-associated peptides recognised by CD8+T cells from B10.BR (H-2k) mice, 13 of which were also recognised by BALB/c (H-2d) mice. As few as five different tetramers used together were able to identify almost 40% of alloreactive T cells within a polyclonal population, suggesting that there are immunodominant allogeneic MHC-peptide complexes that can account for a large proportion of the alloresponse.

Mutation of COL2A1 in a Chinese Family with Presentations of Legg-Calvé-Perthes Disease

2020 ◽  
Author(s):  
denglu yan ◽  
zhaojie Wang ◽  
Zhi Zhang
Keyword(s):  
Femoral Head ◽  
Sanger Sequencing ◽  
Structural Changes ◽  
Genetic Factors ◽  
Mutation Detection ◽  
Perthes Disease ◽  
Chinese Family ◽  
Col2a1 Gene ◽  
Whole Exome ◽  
Missense Substitution

Abstract Background: The aim of this study was to identify genetic factors and chromosomal regions contributing to osteonecrosis of the femoral head (ONFH) in a Chinese family with presentations of Legg-Calvé-Perthes Disease (LCDP). Methods: In this study, we performed whole exon sequencing of a Chinese family with LCPD for mutation detection. Ten members had ONFH in twenty-seven family members in four generations family, 5 unaffected members of the studied family and 5 normal peoples as control were underwent whole exome sequencing for mutation detection. Structural modeling test was applied to analyze the potential structural changes caused by the missense substitution. Results: In this Chinese family affected by LCPD, the mutation (c.3508 G>A, p. Gly1170Ser) in exon 50 of COL2A1 in the Gly–X–Y domain was present in 10 patients but absent in 5 unaffected members of the studied family and in 5 control chromosomes from unaffected individuals of matched geographical ancestry. The COL2A1 gene mutation was further validated by Sanger sequencing, confirmed that were heterozygous for the mutation. Then, we identified the p.Gly1170Ser mutation in exon 50 of COL2A1 in a Chinese family with LCPD. Conclusions: This study maps the mutation of mutation (c.3508 G>A, p. Gly1170Ser) in exon 50 of COL2A1 in the Gly–X–Y domain in a Chinese family of LCPD, which causes osteonecrosis of femoral head.

scholarly journals CTNNB1/β-catenin dysfunction contributes to adiposity by regulating the cross-talk of mature adipocytes and preadipocytes

2020 ◽  
Vol 6 (2) ◽  
pp. eaax9605 ◽  
Author(s):  
Maopei Chen ◽  
Peng Lu ◽  
Qinyun Ma ◽  
Yanan Cao ◽  
Na Chen ◽  
...  
Keyword(s):  
Cross Talk ◽  
High Fat Diet ◽  
Genetic Factors ◽  
Obesity Risk ◽  
High Fat ◽  
Diet Induced Obesity ◽  
Whole Exome ◽  
Obese Subjects ◽  
Mass Expansion ◽  
Transcription Factor Complex

Overnutrition results in adiposity and chronic inflammation with expansion of white adipose tissue (WAT). However, genetic factors controlling fat mass and adiposity remain largely undetermined. We applied whole-exome sequencing in young obese subjects and identified rare gain-of-function mutations in CTNNB1/β-catenin associated with increased obesity risk. Specific ablation of β-catenin in mature adipocytes attenuated high-fat diet–induced obesity and reduced sWAT mass expansion with less proliferated Pdgfrα+ preadipocytes and less mature adipocytes. Mechanistically, β-catenin regulated the transcription of serum amyloid A3 (Saa3), an adipocyte-derived chemokine, through β-catenin–TCF (T-Cell-Specific Transcription Factor) complex in mature adipocytes, and Saa3 activated macrophages to secrete several factors, including Pdgf-aa, which further promoted the proliferation of preadipocytes, suggesting that β-catenin/Saa3/macrophages may mediate mature adipocyte-preadipocyte cross-talk and fat expansion in sWAT. The identification of β-catenin as a key regulator in fat expansion and human adiposity provides the basis for developing drugs targeting Wnt/β-catenin pathway to combat obesity.

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