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International audience; Human immunodeficiency virus (HIV) infection is associated with an increased risk of non-Hodgkin lymphoma (NHL). Even in the era of suppressive antiretroviral treatment, HIV-infected individuals remain at higher risk of developing NHL compared to the general population. To identify potential genetic risk loci, we performed case-control genome-wide association studies and a meta-analysis across three cohorts of HIV+ patients of European ancestry, including a total of 278 cases and 1924 matched controls. We observed a significant association with NHL susceptibility in the C-X-C motif chemokine ligand 12 (CXCL12) region on chromosome 10. A fine mapping analysis identified rs7919208 as the most likely causal variant (P = 4.77e-11), with the G>A polymorphism creating a new transcription factor binding site for BATF and JUND. These results suggest a modulatory role of CXCL12 regulation in the increased susceptibility to NHL observed in the HIV-infected population.

Genome-wide association studies (GWAS) have been successful in identifying and confirming novel genetic variants that are associated with diverse HIV phenotypes. However, these studies have predominantly focused on European cohorts. HLA molecules have been consistently associated with HIV outcomes, some of which have been found to be population specific, underscoring the need for diversity in GWAS. Recently, there has been a concerted effort to address this gap that leads to health care (disease prevention, diagnosis, treatment) disparities with marginal improvement. As precision medicine becomes more utilized, non-European individuals will be more and more disadvantaged, as the genetic variants identified in genomic research based on European populations may not accurately reflect that of non-European individuals. Leveraging pre-existing, large, multiethnic cohorts, such as the UK Biobank, 23andMe, and the National Institute of Health's All of Us Research Program, can contribute in raising genomic research in non-European populations and ultimately lead to better health outcomes.

Vaccines against SARS-CoV-2 have shown high efficacy in clinical trials, yet a full immunologic characterization of these vaccines, particularly within the upper respiratory tract, remains lacking. We enumerated and phenotyped T cells in nasal mucosa and blood before and after vaccination with the Pfizer-BioNTech COVID-19 vaccine (n =21). Tissue-resident memory (Trm) CD8+ T cells expressing CD69+CD103+ expanded ∼12 days following the first and second doses, by 0.31 and 0.43 log10cells per swab respectively (p=0.058 and p=0.009 in adjusted linear mixed models). CD69+CD103+CD8+ T cells in the blood decreased post-vaccination. Similar increases in nasal CD8+CD69+CD103-T cells were observed, particularly following the second dose. CD4+ Th17 cells were also increased in abundance following both doses. Following stimulation with SARS-CoV-2 spike peptides, CD8+ T cells increased expression of CD107a and CD154. These data suggest that nasal T cells may be induced and contribute to the protective immunity afforded by this vaccine.

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Objective Both HIV infection and identifying as MSM have been linked to altered rectal microbiota composition, but few studies have studied sexual behavioural associations with rectal microbiota within MSM. In addition, most rectal microbiota studies in MSM have been limited geographically to Europe and North America, and replication of findings in lower and middle-income countries is lacking. Design A cross-sectional study. Methods We enrolled MSM from Nairobi, Kenya, and determined their HIV/sexually transmitted infection status. Rectal specimens were obtained for 16s rRNA sequencing of the rectal microbiota, and sexual behaviour was characterized using a standardized questionnaire. Microbiome differences were modelled using nonparametric statistics, Bray-Curtis ecological distance metrics and analyses of differential taxa abundance. Multivariable linear regression was used to model HIV status and recent sexual activity as predictors of alpha diversity, controlling for a range of covariates. Results Alpha diversity was consistently lower in Kenyan HIV-infected MSM (n = 80), including those on antiretroviral therapy (ART) compared with HIV-uninfected MSM. A statistical trend was observed for clustering of HIV status by Prevotella or Bacteroides dominance (P = 0.13). Several taxa were enriched in HIV-positive men, including Roseburia, Lachnospira, Streptococcus and Granulicatella. Receptive anal sex with several types of sexual partners (paying, regular, casual) was associated with lower Chao1 and Simpson diversity, independent of HIV status, while HIV infection was associated lower Chao1 (P = 0.030) but not Simpson diversity (P = 0.049). Conclusion Both HIV infection and sexual behaviour were associated with rectal microflora alpha diversity, in particular richness, but not Prevotella spp. dominance, in Kenyan MSM. Associations were more robust for sexual behaviour.

Epstein-Barr virus (EBV) is one of the most common viruses latently infecting humans. Little is known about the impact of human genetic variation on the large inter-individual differences observed in response to EBV infection. To search for a potential imprint of host genomic variation on the EBV sequence, we jointly analyzed paired viral and human genomic data from 268 HIV-coinfected individuals with CD4+ T cell count 3 and elevated EBV viremia. We hypothesized that the reactivated virus circulating in these patients could carry sequence variants acquired during primary EBV infection, thereby providing a snapshot of early adaptation to the pressure exerted on EBV by the individual immune response. We searched for associations between host and pathogen genetic variants, taking into account human and EBV population structure. Our analyses revealed significant associations between human and EBV sequence variation. Three polymorphic regions in the human genome were found to be associated with EBV variation: one at the amino acid level (BRLF1:p.Lys316Glu); and two at the gene level (burden testing of rare variants in BALF5 and BBRF1). Our findings confirm that jointly analyzing host and pathogen genomes can identify sites of genomic interactions, which could help dissect pathogenic mechanisms and suggest new therapeutic avenues.

Epstein–Barr virus (EBV) is one of the most common viruses latently infecting humans. Little is known about the impact of human genetic variation on the large inter-individual differences observed in response to EBV infection. To search for a potential imprint of host genomic variation on the EBV sequence, we jointly analyzed paired viral and human genomic data from 268 HIV-coinfected individuals with CD4 + T cell count 3 and elevated EBV viremia. We hypothesized that the reactivated virus circulating in these patients could carry sequence variants acquired during primary EBV infection, thereby providing a snapshot of early adaptation to the pressure exerted on EBV by the individual immune response. We searched for associations between host and pathogen genetic variants, taking into account human and EBV population structure. Our analyses revealed significant associations between human and EBV sequence variation. Three polymorphic regions in the human genome were found to be associated with EBV variation: one at the amino acid level (BRLF1:p.Lys316Glu); and two at the gene level (burden testing of rare variants in BALF5 and BBRF1). Our findings confirm that jointly analyzing host and pathogen genomes can identify sites of genomic interactions, which could help dissect pathogenic mechanisms and suggest new therapeutic avenues.

The identification of individuals with null alleles enables studying how the loss of gene function affects infection. We previously described a non‐functional variant in SIGLEC1, which encodes the myeloid‐cell receptor Siglec‐1/CD169 implicated in HIV‐1 cell‐to‐cell transmission. Here we report a significant association between the SIGLEC1 null variant and extrapulmonary dissemination of Mycobacterium tuberculosis (Mtb) in two clinical cohorts comprising 6,256 individuals. Local spread of bacteria within the lung is apparent in Mtb‐infected Siglec‐1 knockout mice which, despite having similar bacterial load, developed more extensive lesions compared to wild type mice. We find that Siglec‐1 is necessary to induce antigen presentation through extracellular vesicle uptake. We postulate that lack of Siglec‐1 delays the onset of protective immunity against Mtb by limiting antigen exchange via extracellular vesicles, allowing for an early local spread of mycobacteria that increases the risk for extrapulmonary dissemination.

BACKGROUND Although nonoptimal vaginal bacteria and inflammation have been associated with increased HIV risk, the upstream drivers of these phenotypes are poorly defined in young African women. SETTING Mombasa, Kenya. METHODS We characterized vaginal microbiome and cytokine profiles of sexually active young women aged 14-24 years (n = 168) in 3 study groups: those engaging in formal sex work, in transactional sex, and nonsex workers. Vaginal secretions were collected using self-inserted SoftCup, and assayed for cytokines and vaginal microbiome through multiplex ELISA and 16S rRNA sequencing, respectively. Epidemiological data were captured using a validated questionnaire. RESULTS The median age of participants was 20 years (interquartile range: 18-22 years). Approximately two-thirds of young women (105/168) had vaginal microbial communities characterized by Gardnerella and/or Prevotella spp. dominance; a further 29% (49/168) were predominantly Lactobacillus iners. Microbiome clustering explained a large proportion of cytokine variation (>50% by the first 2 principal components). Age was not associated with vaginal microbial profiles in bivariable or multivariable analyses. Women self-identifying as sex workers had increased alpha (intraindividual) diversity, independent of age, recent sexual activity, HIV, and other sexually transmitted infections (beta = 0.47, 95% confidence interval: 0.05 to 0.90, P = 0.03). Recent sex (number of partners or sex acts last week, time since last vaginal sex) correlated with increased alpha diversity, particularly in participants who were not involved in sex work. CONCLUSION Nonoptimal vaginal microbiomes were common in young Kenyan women and associated with sex work and recent sexual activity, but independent of age. Restoring optimal vaginal microflora may represent a useful HIV prevention strategy.

Pathogen-mediated balancing selection is regarded as a key driver of host immunogenetic diversity. A hallmark for balancing selection in humans is the heterozygote advantage at genes of the human leukocyte antigen (HLA), resulting in improved HIV-1 control. However, the actual mechanism of the observed heterozygote advantage is still elusive. HLA heterozygotes may present a broader array of antigenic viral peptides to immune cells, possibly resulting in a more efficient cytotoxic T-cell response. Alternatively, heterozygosity may simply increase the chance to carry the most protective HLA alleles, as individual HLA alleles are known to differ substantially in their association with HIV-1 control. Here, we used data from 6,311 HIV-1-infected individuals to explore the relative contribution of quantitative and qualitative aspects of peptide presentation in HLA heterozygote advantage against HIV. Screening the entire HIV-1 proteome, we observed that heterozygous individuals exhibited a broader array of HIV-1 peptides presented by their HLA class I alleles. In addition, viral load was negatively correlated with the breadth of the HIV-1 peptide repertoire bound by an individual’s HLA variants, particularly at HLA-B. This suggests that heterozygote advantage at HLA-B is at least in part mediated by quantitative peptide presentation. We also observed higher HIV-1 sequence diversity among HLA-B heterozygous individuals, suggesting stronger evolutionary pressure from HLA heterozygosity. However, HLA heterozygotes were also more likely to carry certain HLA alleles, including the highly protective HLA-B*57:01 variant, indicating that HLA heterozygote advantage ultimately results from a combination of quantitative and qualitative effects in antigen presentation.

Introduction Despite the life-prolonging effects of Highly Active Antiretroviral Therapy (HAART), persons with HIV are still prone to higher rates of non-AIDS related morbidity (such as heart, kidney, and liver disease) than the general public. This is likely due to chronic immune activation and inflammation that persists in HIV-positive persons despite virological suppression. What remains undetermined, however, is whether a link exists between chronic inflammation/immune activation and suboptimal immune recovery on HAART. The hypothesis of the present study is that higher levels of systemic subclinical inflammation and immune activation are linked with suboptimal immune recovery on HAART. Methods Fifteen eligible patients from the Manitoba HIV program were enrolled and followed for up to two years; blood samples were drawn at 4 timepoints each, and concentrations of 21 proinflammatory markers were measured. Patients were grouped according to CD4:CD8 recovery at viral suppression, and the inflammatory profiles of the two groups were compared. Results and conclusions APRIL and BAFF are higher in those with poor recovery at the point of viral suppression, but were also higher in this group at the onset of therapy and through the three additional follow-up visits. TNF-R1, CD163, and Osteopontin, were also in higher concentrations at the outset of therapy and beyond. These five molecules could thus see potential use in the future as biomarkers of likely poor immune recovery. Future work should focus on replicating these findings with larger cohorts.

Common single-nucleotide variation in the host accounts for 25% of the variability in the plasma levels of HIV during the clinical latency stage (viral load set point). However, the role of rare variants and copy number variants remains relatively unexplored. Previous work has suggested copy number variation of a cluster of beta-defensin genes affects HIV load in treatment-na " ive sub-Saharan Africans and rate of response to antiretroviral treatment. Here we analyse a total of 1827 individuals from two cohorts of HIV-infected individuals from Europe and sub-Saharan Africa to investigate the role of beta-defensin copy number variation on HIV load at set point. We find no evidence for association of copy number with viral load. We also compare distribution of beta-defensin copy number between European cases and controls and find no differences, arguing against a role of beta-defensin copy number in HIV acquisition. Taken together, our data argue against an effect of copy number variation of the beta-defensin region in the spontaneous control of HIV infection.

Human immunodeficiency virus (HIV) infection is associated with a substantially increased risk of non-Hodgkin lymphoma (NHL). High plasma viral load, low CD4+ T cell counts and absence of antiretroviral treatment (ART) are known predictive factors for NHL. Even in the era of suppressive ART, HIV-infected individuals remain at increased risk of developing NHL compared to the general population. To search for human genetic determinants of HIV-associated NHL, we performed case-control genome-wide association studies (GWAS) in three cohorts of HIV+ patients of European ancestry and meta-analyzed the results. In total, 278 cases and 1924 matched controls were included. We observed a significant association with NHL susceptibility in the C-X-C motif chemokine ligand 12 (CXCL12) region on chromosome 10. A fine mapping analysis identified rs7919208 as the most likely causal variant (P = 4.77e-11). The G>A polymorphism creates a new transcription factor binding site for BATF and JUND. Analyses of topologically associating domains and promoter capture Hi-C data revealed significant interactions between the rs7919208 region and the promoter of CXCL12, also known as stromal-derived factor 1 (SDF-1). These results suggest a modulatory role of CXCL12 regulation in the increased susceptibility to NHL observed in the HIV-infected population.

Individual differences in HIV-1 control and progression to AIDS have been pinpointed to genetic variation in the HLA, coding for antigen-presenting molecules. However, our understanding of the corresponding antigens is still incomplete. Here we developed an approach that combines HLA genotypes and viral load data of HIV-infected individuals to screen the entire HIV-1 proteome for disease-relevant peptides. Our PepWAS approach identified a limited manageable core set of peptides, accounting for the entire variation in viral load previously associated with genetic variation in the HLA. This core set of disease-relevant antigens thus provides a functional link between HLA genetic variation and HIV-1 control, confirming several known antigens, but also prioritizing previously undescribed antigens as potential therapeutic targets.Genetic variation in the peptide-binding groove of the highly polymorphic HLA class I molecules has repeatedly been associated with HIV-1 control and progression to AIDS, accounting for up to 12% of the variation in HIV-1 set point viral load (spVL). This suggests a key role in disease control for HLA presentation of HIV-1 epitopes to cytotoxic T cells. However, a comprehensive understanding of the relevant HLA-bound HIV epitopes is still elusive. Here we describe a peptidome-wide association study (PepWAS) approach that integrates HLA genotypes and spVL data from 6,311 HIV-infected patients to interrogate the entire HIV-1 proteome (3,252 unique peptides) for disease-relevant peptides. This PepWAS approach predicts a core set of epitopes associated with spVL, including known epitopes but also several previously uncharacterized disease-relevant peptides. More important, each patient presents only a small subset of these predicted core epitopes through their individual HLA-A and HLA-B variants. Eventually, the individual differences in these patient-specific epitope repertoires account for the variation in spVL that was previously associated with HLA genetic variation. PepWAS thus enables a comprehensive functional interpretation of the robust but little-understood association between HLA and HIV-1 control, prioritizing a short list of disease-associated epitopes for the development of targeted therapy.

Background: Certain cervicovaginal microbiota and inflammatory cytokines are strongly associated with each other and with HIV acquisition, but the upstream drivers of this "risk milieu" remain partially defined. Methods: We characterized the vaginal microbiome and cytokine profiles of sexually active young women aged 14-24 years from Mombasa, Kenya (n=168) who were recruited from venues or "hotspots" associated with sex work. Vaginal secretions were collected via self-inserted SoftCupTM, and assayed for cytokines and vaginal microbiome via multiplex ELISA and 16S rRNA sequencing, respectively. Findings: The median age of participants was 20 (IQR: 18-22). In 63% of women (105/168) the vaginal microbial communities were characterized by Gardnerella and/or Prevotella spp.-dominance; a further 29% (49/168) were predominantly Lactobaccillus iners. Microbiome cluster explained a large proportion of cytokine variation (>50% by the first 2 principle components). Age was not associated with vaginal microbial profiles in univariate or multivariate analyses. Women self-identifying as sex workers had increased alpha (intra-individual) diversity, independent of age, recent sexual activity, HIV and other STIs (beta = 0.55, 95% CI: 0.13-0.97, p = 0.01). Recent sex (number of partners or vaginal sex acts last week, time since last vaginal sex) correlated with increased alpha diversity, even in participants who were not involved in sex work. Interpretation: HIV risk-associated vaginal microbial profiles and inflammation were highly associated with each other and both highly prevalent in young women from Mombasa, Kenya. These risk profiles did not differ by age, but were increased in those engaging in formal sex work, and in all participants engaging in recent and/or more frequent sexual activity. Funding Statement: The Transitions study was funded by an operating grant (MOP-13044) from the Canadian Institutes of Health Research (CIHR). Biological aspects of the study were funded by the Canadian Institute of Health Research (CIHR), grant numbers TMI 138658 and PJT-148796. AS is funded by the European & Developing Countries Clinical Trials Partnership (EDCTP) Career Development Fellowship; SM is supported by a CIHROHTN New Investigator Award; MB and LRM are supported by CIHR New Investigator Awards. Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: The study was approved by the ethical review boards of the University of Manitoba and Kenyatta National Hospital.

Multiple genome-wide studies have identified associations between outcome of human immunodeficiency virus (HIV) infection and polymorphisms in and around the gene encoding the HIV co-receptor CCR5, but the functional basis for the strongest of these associations, rs1015164A/G, is unknown. We found that rs1015164 marks variation in an activating transcription factor 1 binding site that controls expression of the antisense long noncoding RNA (lncRNA) CCR5AS. Knockdown or enhancement of CCR5AS expression resulted in a corresponding change in CCR5 expression on CD4+ T cells. CCR5AS interfered with interactions between the RNA-binding protein Raly and the CCR5 3' untranslated region, protecting CCR5 messenger RNA from Raly-mediated degradation. Reduction in CCR5 expression through inhibition of CCR5AS diminished infection of CD4+ T cells with CCR5-tropic HIV in vitro. These data represent a rare determination of the functional importance of a genome-wide disease association where expression of a lncRNA affects HIV infection and disease progression.

The outcome after infection with the human immunodeficiency virus type 1 (HIV-1) is a complex phenotype determined by interactions among the pathogen, the human host and the surrounding environment. An impact of host genetic variation on HIV-1 susceptibility was identified early in the pandemic, with a major role attributed to the genes encoding class I human leukocyte antigens (HLA) and the chemokine receptor CCR5. Studies using genome-wide data sets have underscored the strength of these associations relative to variants located throughout the rest of the genome. However, the extent to which additional polymorphisms influence HIV-1 disease progression, and how much of the variability in outcome can be attributed to host genetics, remain largely unclear. Here we discuss findings concerning the functional impact of associated variants, outline methods for quantifying the host genetic component and examine how available genome-wide data sets may be leveraged to discover gene variants that affect the outcome of HIV-1 infection.

PURPOSE OF REVIEW: Rapid expansion of genomic technologies has resulted in an unprecedented ability to interrogate the impact of human genetic variation on disease. HIV-1 infection is a unique model for studying this impact because host genetic variation influences both clinical outcome and the genetic sequence and evolution of the pathogen itself. RECENT FINDINGS: Several candidate gene studies have proposed novel associations with HIV acquisition and/or disease progression; however, many of these are not supported by larger genome-wide association studies. Thus, controversy remains as to which host and viral genetic factors truly impact HIV infection. Novel methods for assessing the genetic (viral and host) component of disease progression are becoming important areas of investigation. SUMMARY: To fully understand the impact of human genetic variation in HIV disease, the field will need to come together to set a standard for discovery of new genes. Additionally, novel avenues of investigation such as sequencing studies (to define the role of rare variants), studies of epistasis and host/viral genome interaction will be of great value

Purpose Protecting patient privacy is a major obstacle for the implementation of genomic-based medicine. Emerging privacy-enhancing technologies can become key enablers for managing sensitive genetic data. We studied physicians’ attitude toward this kind of technology in order to derive insights that might foster their future adoption for clinical care. Methods We conducted a questionnaire-based survey among 55 physicians of the Swiss HIV Cohort Study who tested the first implementation of a privacy-preserving model for delivering genomic test results. We evaluated their feedback on three different aspects of our model: clinical utility, ability to address privacy concerns and system usability. Results 38/55 (69%) physicians participated in the study. Two thirds of them acknowledged genetic privacy as a key aspect that needs to be protected to help building patient trust and deploy new-generation medical information systems. All of them successfully used the tool for evaluating their patients’ pharmacogenomics risk and 90% were happy with the user experience and the efficiency of the tool. Only 8% of physicians were unsatisfied with the level of information and wanted to have access to the patient’s actual DNA sequence. Conclusion This survey, although limited in size, represents the first evaluation of privacy-preserving models for genomic-based medicine. It has allowed us to derive unique insights that will improve the design of these new systems in the future. In particular, we have observed that a clinical information system that uses homomorphic encryption to provide clinicians with risk information based on sensitive genetic test results can offer information that clinicians feel sufficient for their needs and appropriately respectful of patients’ privacy. The ability of this kind of systems to ensure strong security and privacy guarantees and to provide some analytics on encrypted data has been assessed as a key enabler for the management of sensitive medical information in the near future. Providing clinically relevant information to physicians while protecting patients’ privacy in order to comply with regulations is crucial for the widespread use of these new technologies.

Polygenic approaches using genome-wide data have been hugely successful in confirming and quantifying the heritability of complex human traits. Here, we highlight their ability to identify potential novel risk variants by looking for variants with pleiotropic effect in genetically overlapping phenotypes.We used LD Score Regression in a sample of 6,315 HIV+ European individuals and 7,247 controls to test for phenotypes genetically overlapping with susceptibility to HIV-1 infection. Using LD Hub, a web tool that performs LD Score Regression, identified two phenotypes with significant genetic overlap: schizophrenia (rG =0.19, p=0.0007 and ulcerative colitis (rG=0.22, p= 0.0061). We further showed that the genetic overlap between HIV acquisition and schizophrenia is likely driven in part by their shared overlap with cannabis use and sexual behavior. BUMHBOX analyses suggested that these genetic overlaps were driven by genome-wide pleiotropy with HIV acquisition rather than heterogeneity within the HIV acquisition sample. The two diseases identified as genetically overlapping with HIV-1 acquisition have >100 associated variants, and we tested if any of them significantly associated with HIV acquisition. We observed three variants that exceeded our threshold for statistical significance. Two of these were eQTLs in whole blood for genes coding for proteins suspected to be involved in HIV biology: rs1819333 in CCR6 (p=0.0002) and rs4932178 in FURIN (p=0.00033). However, no signal was found for these variants in two smaller African samples totaling 1015 cases and 963 controls, though the mode of acquisition and genetic architecture of these populations differed.These results highlight the ability to use polygenic methods to gain new insights into complex diseases and identify potential associations with individual variants. Crucially, the leveraging of existing, publically available data makes these methods a cost-effective approach. In this case, our results add to the evidence for the role of risk taking behavior and inflammation of the bowel in HIV acquisition.Author SummaryThe biology of what puts certain individuals at greater risk of HIV acquisition is poorly understood. Using several novel polygenic methods, we identify supporting evidence for two important factors leading to acquisition. First, the role of an individual’s genetic predisposition to risk taking behaviours such as number of sexual partners, age at first sexual intercourse drug use, and mental health problems. Second, the role of gut inflammation, in particular a genetic overlap between HIV acquisition with inflammatory bowel disease and the potential role of CCR6 during infection.

Giant cell arteritis (GCA) is the most common form of vasculitis in individuals older than 50 years in Western countries. To shed light onto the genetic background influencing susceptibility for GCA, we performed a genome-wide association screening in a well-powered study cohort. After imputation, 1,844,133 genetic variants were analyzed in 2,134 case subjects and 9,125 unaffected individuals from ten independent populations of European ancestry. Our data confirmed HLA class II as the strongest associated region (independent signals: rs9268905, p = 1.94 × 10−54, per-allele OR = 1.79; and rs9275592, p = 1.14 × 10−40, OR = 2.08). Additionally, PLG and P4HA2 were identified as GCA risk genes at the genome-wide level of significance (rs4252134, p = 1.23 × 10−10, OR = 1.28; and rs128738, p = 4.60 × 10−9, OR = 1.32, respectively). Interestingly, we observed that the association peaks overlapped with different regulatory elements related to cell types and tissues involved in the pathophysiology of GCA. PLG and P4HA2 are involved in vascular remodelling and angiogenesis, suggesting a high relevance of these processes for the pathogenic mechanisms underlying this type of vasculitis.

Viral respiratory infections are usually mild and self-limiting; still they exceptionally result in life-threatening infections in previously healthy children. To investigate a potential genetic cause, we recruited 120 previously healthy children requiring support in intensive care because of a severe illness caused by a respiratory virus. Using exome and transcriptome sequencing, we identified and characterized three rare loss-of-function variants in IFIH1, which encodes an RIG-I-like receptor involved in the sensing of viral RNA. Functional testing of the variants IFIH1 alleles demonstrated that the resulting proteins are unable to induce IFN-β, are intrinsically less stable than wild-type IFIH1, and lack ATPase activity. In vitro assays showed that IFIH1 effectively restricts replication of human respiratory syncytial virus and rhinoviruses. We conclude that IFIH1 deficiency causes a primary immunodeficiency manifested in extreme susceptibility to common respiratory RNA viruses.

A recent genome-wide association study (GWAS) involving patients with hemophilia A who were exposed to but uninfected with human immunodeficiency virus type 1 (HIV-1) did not reveal genetic variants associated with resistance to HIV-1 infection, beyond homozygosity for CCR5-Δ32. Since variation in HLA class I and KIR genes is not well interrogated by standard GWAS techniques, we tested whether these 2 loci were involved in protection from HIV-1 infection in the same hemophilia cohort, using controls from the general population. Our data indicate that HLA class I alleles, presence or absence of KIR genes, and functionally relevant combinations of the HLA/KIR genotypes are not involved in resistance to parenterally transmitted HIV-1 infection.

Numerous in vitro studies attribute to human TRIM5α some modest anti-HIV-1 activity and human population studies suggest some differential effect of TRIM5α polymorphisms on disease progression. If the activity of TRIM5α were relevant in vivo, it could result in positive selection on the viral capsid. To address this issue, we identified 10 positively selected sites in HIV-1 capsid from multiple viral strains and generated 17 clade B viruses carrying a minor (i.e. low frequency) residue or an alanine at those positions. All recombinant viruses were susceptible to the modest effect of common human TRIM5α and allelic variants R136Q, and H419Y; H43Y and G249D TRIM5α were generally inactive. Increased sensitivity to TRIM5α was observed for some capsid variants, suggesting that minor residues are selected against in human populations. On the other hand, the modest potency of human TRIM5α does not translate in escape mutations in the viral capsid.

Common single-nucleotide variation in the host accounts for 25% of the variability in the plasma levels of HIV during the clinical latency stage (viral load set point). However, the role of rare variants and copy number variants remains relatively unexplored. Previous work has suggested copy number variation of a cluster of β-defensin genes affects HIV load in treatment-naïve sub-Saharan Africans and rate of response to antiretroviral treatment. Here we analyse a total of 1827 individuals from two cohorts of HIV-infected individuals from Europe and sub-Saharan Africa to investigate the role of β-defensin copy number variation on HIV load at set point. We find no evidence for association of copy number with viral load. We also compare distribution of β-defensin copy number between European cases and controls and find no differences, arguing against a role of β-defensin copy number in HIV acquisition. Taken together, our data argue against an effect of copy number variation of the β-defensin region in the spontaneous control of HIV infection.

One out of three pediatric sepsis deaths in high income countries occur in previously healthy children. Primary immunodeficiencies have been postulated to underlie fulminant sepsis, but this concept remains to be confirmed in clinical practice. Pseudomonas aeruginosa (P. aeruginosa) is a common bacterium mostly associated with healthcare-related infections in immunocompromised individuals. However, in rare cases, it can cause sepsis in previously healthy children. We used exome sequencing and bioinformatic analysis to systematically search for genetic factors underpinning severe P. aeruginosa infection in the pediatric population. We collected blood samples from 11 previously healthy children, with no family history of immunodeficiency, who presented with severe sepsis due to community-acquired P. aeruginosa bacteremia. Genomic DNA was extracted from blood or tissue samples obtained intravitam or postmortem. We obtained high-coverage exome sequencing data and searched for rare loss-of-function variants. After rigorous filtrations, 12 potentially causal variants were identified. 2 out of 8 (25%) fatal cases were found to carry novel pathogenic variants in primary immunodeficiency genes, including BTK and DNMT3B. This study demonstrates that exome sequencing allows to identify rare, deleterious human genetic variants responsible for fulminant sepsis in apparently healthy children. Diagnosing primary immunodeficiencies in such patients is of high relevance to survivors and affected families. We propose that unusually severe and fatal sepsis cases in previously healthy children should be considered for exome/genome sequencing to search for underlying primary immunodeficiencies.