Host genetic variation and HIV disease: from mapping to mechanism

The impact of micropolymorphism in Anpl-UAA on structural stability and peptide presentation

Micropolymorphism significantly shapes the peptide-binding characteristics of major histocompatibility complex class I (MHC-I) molecules, affecting the host's resistance to pathogens, which is particularly pronounced in avian species displaying the "minimal essential MHC" expression pattern. In this study, we compared two duck MHC-I alleles, Anpl-UAA*77 and Anpl-UAA*78, that exhibit markedly different peptide binding properties despite their high sequence homology. Through mutagenesis experiments and crystallographic analysis of complexes with the influenza virus-derived peptide AEAIIVAMV (AEV9), we identified a critical role for the residue at position 62 in regulating hydrogen-bonding interactions between the peptide backbone and the peptide-binding groove. This modulation affects the characteristics of the B pocket and the stability of the loop region between the 310 helix and the α1 helix, leading to significant changes in the structure and stability of the peptide-MHC-I complex (pMHC-I). Moreover, the proportion of different residues at position 62 among Anpl-UAAs may reflect the correlation between pAnpl-UAA stability and duck body temperature. This research not only advances our understanding of the Anpl-UAA structure but also deepens our insight into the impact of MHC-I micropolymorphism on peptide binding.

Insights into the mechanisms and structure of breakage-fusion-bridge cycles in cervical cancer using long-read sequencing

Cervical cancer is caused by human papillomavirus (HPV) infection, has few approved targeted therapeutics, and is the most common cause of cancer death in low-resource countries. We characterized 19 cervical and four head and neck cancer cell lines using long-read DNA and RNA sequencing and identified the HPV types, HPV integration sites, chromosomal alterations, and cancer driver mutations. Structural variation analysis revealed telomeric deletions associated with DNA inversions resulting from breakage-fusion-bridge (BFB) cycles. BFB is a common mechanism of chromosomal alterations in cancer, and our study applies long-read sequencing to this important chromosomal rearrangement type. Analysis of the inversion sites revealed staggered ends consistent with exonuclease digestion of the DNA after breakage. Some BFB events are complex, involving inter- or intra-chromosomal insertions or rearrangements. None of the BFB breakpoints had telomere sequences added to resolve the dicentric chromosomes, and only one BFB breakpoint showed chromothripsis. Five cell lines have a chromosomal region 11q BFB event, with YAP1-BIRC3-BIRC2 amplification. Indeed, YAP1 amplification is associated with a 10-year-earlier age of diagnosis of cervical cancer and is three times more common in African American women. This suggests that individuals with cervical cancer and YAP1-BIRC3-BIRC2 amplification, especially those of African ancestry, might benefit from targeted therapy. In summary, we uncovered valuable insights into the mechanisms and consequences of BFB cycles in cervical cancer using long-read sequencing.

Vaccinomics: Paving the Way for Personalized Immunization

Vaccines are one of the most important medical advancements in human history. They have been successfully used to control and limit the spread of many of the lethal diseases that have plagued us, such as smallpox and polio. Previous vaccine design methodologies were based on the model of "isolate-inactivateinject", which amounts to giving the same vaccine dose to everyone susceptible to infection. In recent years, the importance of how the host genetic background alters vaccine response necessitated the introduction of vaccinomics, which is aimed at studying the variability of vaccine efficacy by associating genetic variability and immune response to vaccination. Despite the rapid developments in variant screening, data obtained from association studies is often inconclusive and cannot be used to guide the new generation of vaccines. This review aims to compile the polymorphisms in HLA and immune system genes and examine the link with their immune response to vaccination. The compiled data can be used to guide the development of new strategies for vaccination for vulnerable groups. Overall, the highly polymorphic HLA locus had the highest correlation with vaccine response variability for most of the studied vaccines, and it was linked to variation in multiple stages of the immune response to the vaccines for both humoral and cellular immunity. Designing new vaccine technologies and immunization regiments to accommodate for this variability is an important step for reaching a vaccinomics-based approach to vaccination.

The HLA-B*57:01 allele corresponds to a very large MHC haploblock likely explaining its massive effect for HIV-1 elite control

Introduction

We have reanalyzed the genomic data of the International Collaboration for the Genomics of HIV (ICGH), centering on HIV-1 Elite Controllers.

Methods

We performed a genome-wide Association Study comparing 543 HIV Elite Controllers with 3,272 uninfected controls of European descent. Using the latest database for imputation, we analyzed 35,552 Single Nucleotide Polymorphisms (SNPs) within the Major Histocompatibility Complex (MHC) region.

Results

Our analysis identified 2,626 SNPs significantly associated (p<5. 10-8) with elite control of HIV-1 infection, including well-established MHC signals such as the rs2395029-G allele which tags HLA-B*57:01. A thorough investigation of SNPs in linkage disequilibrium with rs2395029 revealed an extensive haploblock spanning 1.9 megabases in the MHC region tagging HLA-B*57:01, comprising 379 SNP alleles impacting 72 genes. This haploblock contains damaging variations in proteins like NOTCH4 and DXO and is also associated with a strong differential pattern of expression of multiple MHC genes such as HLA-B, MICB, and ZBTB12. The study was expanded to include two cohorts of seropositive African-American individuals, where a haploblock tagging the HLA-B*57:03 allele was similarly associated with control of viral load. The mRNA expression profile of this haploblock in African Americans closely mirrored that in the European cohort.

Discussion

These findings suggest that additional molecular mechanisms beyond the conventional antigen-presenting role of class I HLA molecules may contribute to the observed influence of HLA-B*57:01/B*57:03 alleles on HIV-1 elite control. Overall, this study has uncovered a large haploblock associated with HLA-B*57 alleles, providing novel insights into their massive effect on HIV-1 elite control.

Genomic Factors and Therapeutic Approaches in HIV-Associated Neurocognitive Disorders: A Comprehensive Review

HIV-associated neurocognitive disorders (HANDs) still persist despite improved life expectancy, reduced viral loads, and decreased infection severity. The number of patients affected by HANDs ranges from (30 to 50) % of HIV-infected individuals. The pathological mechanisms contributing to HANDs and the most serious manifestation of the disease, HIV-associated dementia (HAD), are not yet well understood. Evidence suggests that these mechanisms are likely multifactorial, producing neurocognitive complications involving disorders such as neurogenesis, autophagy, neuroinflammation, and mitochondrial dysfunction. Over the years, multiple pharmacological approaches with specific mechanisms of action acting upon distinct targets have been approved. Although these therapies are effective in reducing viral loading to undetectable levels, they also present some disadvantages such as common side effects, the need for administration with a very high frequency, and the possibility of drug resistance. Genetic studies on HANDs provide insights into the biological pathways and mechanisms that contribute to cognitive impairment in people living with HIV-1. Furthermore, they also help identify genetic variants that increase susceptibility to HANDs and can be used to tailor treatment approaches for HIV-1 patients. Identification of the genetic markers associated with disease progression can help clinicians predict which individuals require more aggressive management and by understanding the genetic basis of the disorder, it will be possible to develop targeted therapies to mitigate cognitive impairment. The main goal of this review is to provide details on the epidemiological data currently available and to summarise the genetic (specifically, the genetic makeup of the immune system), transcriptomic, and epigenetic studies available on HANDs to date. In addition, we address the potential pharmacological therapeutic strategies currently being investigated. This will provide valuable information that can guide clinical care, drug development, and our overall understanding of these diseases.

Insights into the Mechanisms and Structure of Breakage-Fusion-Bridge Cycles in Cervical Cancer using Long-Read Sequencing

Cervical cancer is caused by human papillomavirus (HPV) infection, has few approved targeted therapeutics, and is the most common cause of cancer death in low-resource countries. We characterized 19 cervical and four head and neck cell lines using long-read DNA and RNA sequencing and identified the HPV types, HPV integration sites, chromosomal alterations, and cancer driver mutations. Structural variation analysis revealed telomeric deletions associated with DNA inversions resulting from breakage-fusion-bridge (BFB) cycles. BFB is a common mechanism of chromosomal alterations in cancer, and this is one of the first analyses of these events using long-read sequencing. Analysis of the inversion sites revealed staggered ends consistent with exonuclease digestion of the DNA after breakage. Some BFB events are complex, involving inter- or intra-chromosomal insertions or rearrangements. None of the BFB breakpoints had telomere sequences added to resolve the dicentric chromosomes and only one BFB breakpoint showed chromothripsis. Five cell lines have a Chr11q BFB event, with YAP1/BIRC2/BIRC3 gene amplification. Indeed, YAP1 amplification is associated with a 10-year earlier age of diagnosis of cervical cancer and is three times more common in African American women. This suggests that cervical cancer patients with YAP1/BIRC2/BIRC3-amplification, especially those of African American ancestry, might benefit from targeted therapy. In summary, we uncovered new insights into the mechanisms and consequences of BFB cycles in cervical cancer using long-read sequencing.

Inflammasome genetic variants are associated with tuberculosis, HIV-1 infection, and TB/HIV-immune reconstitution inflammatory syndrome outcomes

Background

Tuberculosis (TB) and AIDS are the leading causes of infectious diseases death worldwide. Here, we investigated the relationship between from single nucleotide polymorphisms (SNPs) of the NLRP3, CARD8, AIM2, CASP-1, IFI16, and IL-1β inflammasome genes, as well as the profiles of secreted proinflammatory cytokines (e.g., IL-1β, IL-18, IL-33, and IL-6) with the TB clinical profiles, TB-HIV coinfection, and IRIS onset.

Methods

The individuals were divided into four groups: TB-HIV group (n=88; 11 of them with IRIS), HIV-1 group (n=20), TB group (n=24) and healthy volunteers (HC) group (n=10), and were followed up at INI/FIOCRUZ and HGNI (Rio de Janeiro/Brazil) from 2006 to 2016. Real-time PCR was used to determine the genotypes of the Single Nucleotide Polymorphism (SNPs), and ELISA was used to measure the plasma cytokine levels. Unconditional logistic regression models were used to perform risk estimations.

Results

A higher risk for extrapulmonary TB was associated with the TT genotype (aOR=6.76; P=0.026) in the NLRP3 rs4612666 Single Nucleotide Polymorphism (SNP) and the C-C-T-G-C haplotype (aOR=4.99; P= 0.017) in the NLRP3 variants. This same Single Nucleotide Polymorphism (SNP) was associated with lower risk against extrapulmonary TB when the carrier allele C (aOR=0.15; P=0.021) was present. Among those with HIV-1 infections, a higher risk for TB onset was associated with the GA genotype (aOR=5.5; P=0.044) in the IL1-β rs1143634 Single Nucleotide Polymorphism (SNP). In contrast, lower risk against TB onset was associated with the A-G haplotype (aOR=0.17; P= 0.026) in the CARD8 variants. Higher IL-6 and IL-33 levels were observed in individuals with TB. A higher risk for IRIS onset was associated with CD8 counts ≤ 500 cells/mm3 (aOR=12.32; P=0.010), the presence of extrapulmonary TB (aOR=6.6; P=0.038), and the CT genotype (aOR=61.06; P=0.026) or carrier allele T (aOR=61.06; P=0.026) in the AIM2 rs2276405 Single Nucleotide Polymorphism (SNP), whereas lower risk against IRIS onset was associated with the AT genotype (aOR=0.02; P=0.033) or carrier allele T (aOR=0.02; P=0.029) in the CARD8 rs2043211 Single Nucleotide Polymorphism (SNP) and the T-G haplotype (aOR=0.07; P= 0.033) in the CARD8 variants. No other significant associations were observed.

Conclusions

Our results depict the involvement of genetic polymorphisms of crucial innate immunity genes and proinflammatory cytokines in the clinical outcomes related to TB-HIV coinfection.

Immunogenomics of Killer Cell Immunoglobulin-Like Receptor (KIR) and HLA Class I: Coevolution and Consequences for Human Health

Interactions of killer cell immunoglobin-like receptors (KIR) with human leukocyte antigens (HLA) class I regulate effector functions of key cytotoxic cells of innate and adaptive immunity. The extreme diversity of this interaction is genetically determined, having evolved in the ever-changing environment of pathogen exposure. Diversity of KIR and HLA genes is further facilitated by their independent segregation on separate chromosomes. That fetal implantation relies on many of the same types of immune cells as infection control places certain constraints on the evolution of KIR interactions with HLA. Consequently, specific inherited combinations of receptors and ligands may predispose to specific immune-mediated diseases, including autoimmunity. Combinatorial diversity of KIR and HLA class I can also differentiate success rates of immunotherapy directed to these diseases. Progress toward both etiopathology and predicting response to therapy is being achieved through detailed characterization of the extent and consequences of the combinatorial diversity of KIR and HLA. Achieving these goals is more tractable with the development of integrated analyses of molecular evolution, function, and pathology that will establish guidelines for understanding and managing risks. Here, we present what is known about the coevolution of KIR with HLA class I and the impact of their complexity on immune function and homeostasis.

Mechanism of Viral Suppression among HIV Elite Controllers and Long-Term Nonprogressors in Nigeria and South Africa

A subgroup among people living with HIV (PLHIV) experience viral suppression, sometimes to an undetectable level in the blood and/or are able to maintain a healthy CD4+ T-cell count without the influence of antiretroviral (ARV) therapy. One out of three hundred PLHIV fall into this category, and a large sample of this group can be found in areas with a high prevalence of HIV infection such as Nigeria and South Africa. Understanding the mechanism underpinning the nonprogressive phenotype in this subgroup may provide insights into the control of the global HIV epidemic. This work provides mechanisms of the elite control and nonprogressive phenotype among PLHIV in Nigeria and South Africa and identifies research gaps that will contribute to a better understanding on HIV controllers among PLHIV.

Evaluation of CCR5-Δ32 mutation and HIV-1 surveillance drug-resistance mutations in peripheral blood mononuclear cells of long-term non progressors of HIV-1-infected individuals

Aim: This study aimed to evaluate chemokine receptor 5 delta 32 (CCR5-Δ32) mutation and HIV-1 surveillance drug-resistance mutations (SDRMs) in peripheral blood mononuclear cells of long-term non progressors (LTNPs) of HIV-1-infected individuals. Materials and methods: This research was performed on 197 treatment-naive HIV-1-infected patients. After follow-up, it was determined that 15 (7.6%) of these people were LTNPs. The PCR assay was performed to identify the CCR5 genotype and HIV-1 SDRMs. Results: One (6.7%) of the LTNPs was heterozygous (wt/Δ32) for the CCR5 delta 32 (CCR5Δ32). However, none of the individuals was homozygous for this mutation (Δ32/Δ32). Moreover, none of the LTNPs showed HIV-1 SDRMs. The CRF35-AD subtype was the most dominant subtype, with a percentage of 93.3%. Conclusion: Iranian elite controllers are negative for CCR5-delta 32 homozygous genotype and drug resistance against antiretroviral drugs.

The Characteristics of the HIV-1 Env Glycoprotein Are Linked With Viral Pathogenesis

The understanding of HIV-1 pathogenesis and clinical progression is incomplete due to the variable contribution of host, immune, and viral factors. The involvement of viral factors has been investigated in extreme clinical phenotypes from rapid progressors to long-term non-progressors (LTNPs). Among HIV-1 proteins, the envelope glycoprotein complex (Env) has been concentrated on in many studies for its important role in the immune response and in the first steps of viral replication. In this study, we analyzed the contribution of 41 Envs from 24 patients with different clinical progression rates and viral loads (VLs), LTNP-Elite Controllers (LTNP-ECs); Viremic LTNPs (vLTNPs), and non-controller individuals contemporary to LTNPs or recent, named Old and Modern progressors. We studied the Env expression, the fusion and cell-to-cell transfer capacities, as well as viral infectivity. The sequence and phylogenetic analysis of Envs were also performed. In every functional characteristic, the Envs from subjects with viral control (LTNP-ECs and vLTNPs) showed significant lower performance compared to those from the progressor individuals (Old and Modern). Regarding sequence analysis, the variable loops of the gp120 subunit of the Env (i.e., V2, V4, and mainly V5) of the progressor individuals showed longer and more glycosylated sequences than controller subjects. Therefore, HIV-1 Envs from virus of patients presenting viremic control and the non-progressor clinical phenotype showed poor viral functions and shorter sequences, whereas functional Envs were associated with virus of patients lacking virological control and with progressor clinical phenotypes. These correlations support the role of Env genotypic and phenotypic characteristics in the in vivo HIV-1 infection and pathogenesis.

Will Host Genetics Affect the Response to SARS-CoV-2 Vaccines? Historical Precedents

Recent progress in genomics and bioinformatics technologies have allowed for the emergence of immunogenomics field. This intersection of immunology and genetics has broadened our understanding of how the immune system responds to infection and vaccination. While the immunogenetic basis of the huge clinical variability in response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is currently being extensively studied, the host genetic determinants of SARS-CoV-2 vaccines remain largely unknown. Previous reports evidenced that vaccines may not protect all populations or individuals equally, due to multiple host- and vaccine-specific factors. Several studies on vaccine response to measles, rubella, hepatitis B, smallpox, and influenza highlighted the contribution of genetic mutations or polymorphisms in modulating the innate and adaptive immunity following vaccination. Specifically, genetic variants in genes encoding virus receptors, antigen presentation, cytokine production, or related to immune cells activation and differentiation could influence how an individual responds to vaccination. Although such knowledge could be utilized to generate personalized vaccine strategies to optimize the vaccine response, studies in this filed are still scarce. Here, we briefly summarize the scientific literature related to the immunogenetic determinants of vaccine-induced immunity, highlighting the possible role of host genetics in response to SARS-CoV-2 vaccines as well.

TRIM22 genotype is not associated with markers of disease progression in children with HIV-1 infection

OBJECTIVE

Untreated perinatal HIV-1 infection is often associated with rapid disease progression in children with HIV (CWH), characterized by high viral loads and early mortality. TRIM22 is a host restriction factor, which directly inhibits HIV-1 transcription, and its genotype variation is associated with disease progression in adults. We tested the hypothesis that TRIM22 genotype is associated with disease progression in CWH.

DESIGN

ART-naive CWH, aged 6-16 years, were recruited from primary care clinics in Harare, Zimbabwe. We performed a candidate gene association study of TRIM22 genotype and haplotypes with markers of disease progression and indicators of advanced disease.

METHODS

TRIM22 exons three and four were sequenced by Sanger sequencing and single nucleotide polymorphisms were associated with markers of disease progression (CD4+ T-cell count and HIV viral load) and clinical indicators of advanced HIV disease (presence of stunting and chronic diarrhoea). Associations were tested using multivariate linear and logistic regression models.

RESULTS

A total of 241 children, median age 11.4 years, 50% female, were included. Stunting was present in 16% of participants. Five SNPs were analyzed including rs7935564, rs2291842, rs78484876, rs1063303 and rs61735273. The median CD4+ count was 342 (IQR: 195-533) cells/μl and median HIV-1 viral load 34 199 (IQR: 8211-90 662) IU/ml. TRIM22 genotype and haplotypes were not associated with CD4+ T-cell count, HIV-1 viral load, stunting or chronic diarrhoea.

CONCLUSION

TRIM22 genotype was not associated with markers of HIV disease progression markers or advanced disease in CWH.

Cohort profile: the Netherlands Cohort Study on Acute HIV infection (NOVA), a prospective cohort study of people with acute or early HIV infection who immediately initiate HIV treatment

PURPOSE

Initiation of combination antiretroviral therapy (cART) during acute or early HIV-infection (AEHI) limits the size of the viral reservoir and preserves immune function. This renders individuals who started cART during AEHI promising participants in HIV-cure trials. Therefore, we established a multicentre prospective cohort study in the Netherlands that enrols people with AEHI. In anticipation of future cure trials, we will longitudinally investigate the properties of the viral reservoir size and HIV-specific immune responses among cohort participants.

PARTICIPANTS

Participants immediately initiate intensified cART: dolutegravir, emtricitabine/tenofovir and darunavir/ritonavir (DRV/r). After 4 weeks, once baseline resistance data are available, DRV/r is discontinued. Three study groups are assembled based on the preparedness of individuals to participate in the extensiveness of sampling. Participants accepting immediate treatment and follow-up but declining additional sampling are included in study group 1 ('standard') and routine diagnostic procedures are performed. Participants willing to undergo blood, leukapheresis and semen sampling are included in study group 2 ('less invasive'). In study group 3 ('extended'), additional tissue (gut-associated lymphoid tissue, peripheral lymph node) and cerebrospinal fluid sampling are performed.

FINDINGS TO DATE

Between 2015 and 2020, 140 individuals with AEHI have been enrolled at nine study sites. At enrolment, median age was 36 (IQR 28-47) years, and 134 (95.7%) participants were men. Distribution of Fiebig stages was as follows: Fiebig I, 3 (2.1%); II, 20 (14.3%); III, 7 (5.0%); IV, 49 (35.0%); V, 39 (27.9%); VI, 22 (15.7%). Median plasma HIV RNA was 5.9 (IQR 4.7-6.7) log10 copies/mL and CD4 count 510 (IQR 370-700) cells/mm3. Median time from cART initiation to viral suppression was 8.0 (IQR 4.0-16.0) weeks.

FUTURE PLANS

The Netherlands Cohort Study on Acute HIV infection remains open for participant enrolment and for additional sites to join the network. This cohort provides a unique nationwide platform for conducting future in-depth virological, immunological, host genetic and interventional studies investigating HIV-cure strategies.

The influence of HLA/HIV genetics on the occurrence of elite controllers and a need for therapeutics geotargeting view

The interaction of HIV-1, human leukocyte antigen (HLA), and elite controllers (EC) compose a still intricate triad. Elite controllers maintain a very low viral load and a normal CD4 count, even without antiretrovirals. There is a lot of diversity in HIV subtypes and HLA alleles. The most common subtype in each country varies depending on its localization and epidemiological history. As we know EC appears to maintain an effective CD8 response against HIV. In this phenomenon, some alleles of HLAs are associated with a slow progression of HIV infection, others with a rapid progression. This relationship also depends on the virus subtype. Epitopes of Gag protein-restricted by HLA-B*57 generated a considerable immune response in EC. However, some mutations allow HIV to escape the CD8 response, while others do not. HLA protective alleles, like HLA-B*27, HLA-B*57 and HLA-B*58:01, that are common in Caucasians infected with HIV-1 Clade B, do not show the same protection in sub-Saharan Africans infected by HIV-1 Clade C. Endogenous pathway of antigen processing and presentation is used to present intracellular synthesized cellular peptides as well as viral protein fragments via the MHC class I molecule to the cytotoxic T-lymphocytes (CTLs). Some epitopes are immunodominant, which means that they drive the immune reaction to some virus. Mutation on an anchor residue of epitope necessary for binding on MHC class I is used by HIV to escape the immune system. Mutations inside or flanking an epitope may lead to T cell lack of recognition and CTL escape. Studying how immunodominance at epitopes drives the EC in a geographically dependent way with genetics and immunological elements orchestrating it may help future research on vaccines or immunotherapy for HIV.

Polymorphisms in MHC class I molecules influence their interactions with components of the antigen processing and presentation pathway

MHC class I (MHC-I) molecules undergo an intricate folding process in order to pick up antigenic peptide to present to the immune system. In recent years, the discovery of a new peptide editor for MHC-I has added an extra level of complexity in our understanding of how peptide presentation is regulated. On top of this, the incredible diversity in MHC-I molecules leads to significant variation in the interaction between MHC-I and components of the antigen processing and presentation pathway. Here, we review our current understanding regarding how polymorphisms in human leukocyte antigen class I molecules influence their interactions with key components of the antigen processing and presentation pathway. A deeper understanding of this may offer new insights regarding how apparently subtle variation in MHC-I can have a significant impact on susceptibility to disease.

Human immunotypes impose selection on viral genotypes through viral epitope specificity

BACKGROUND

Understanding the genetic interplay between human hosts and infectious pathogens is crucial for how we interpret virulence factors. Here, we tested for associations between HIV and host genetics, and interactive genetic effects on viral load (VL) in HIV+ ART-naive clinical trial participants.

METHODS

HIV genomes were sequenced and the encoded amino acid (AA) variants were associated with VL, human single nucleotide polymorphisms (SNPs) and imputed HLA alleles, using generalized linear models with Bonferroni correction.

RESULTS

Human (388,501 SNPs) and HIV (3,010 variants) genetic data was available for 2,122 persons. Four HIV variants were associated with VL (p-values<1.66×10 -5). Twelve HIV variants were associated with a range of 1-512 human SNPs (p-value<4.28×10 -11). We found 46 associations between HLA alleles and HIV variants (p-values<1.29×10 -7). We found HIV variants and immunotypes when analyzed separately, were associated with lower VL, whereas the opposite was true when analyzed in concert. Epitope binding prediction showed HLA alleles to be weaker binders of associated HIV AA variants relative to alternative variants on the same position.

CONCLUSIONS

Our results show the importance of immunotype specificity on viral antigenic determinants, and the identified genetic interplay puts emphasis that viral and human genetics should be studied in the context of each other.

Peptidomes and Structures Illustrate Two Distinguishing Mechanisms of Alternating the Peptide Plasticity Caused by Swine MHC Class I Micropolymorphism

The micropolymorphism of major histocompatibility complex class I (MHC-I) can greatly alter the plasticity of peptide presentation, but elucidating the underlying mechanism remains a challenge. Here we investigated the impact of the micropolymorphism on peptide presentation of swine MHC-I (termed swine leukocyte antigen class I, SLA-I) molecules via immunopeptidomes that were determined by our newly developed random peptide library combined with the mass spectrometry (MS) de novo sequencing method (termed RPLD–MS) and the corresponding crystal structures. The immunopeptidomes of SLA-1*04:01, SLA-1*13:01, and their mutants showed that mutations of residues 156 and 99 could expand and narrow the ranges of peptides presented by SLA-I molecules, respectively. R156A mutation of SLA-1*04:01 altered the charge properties and enlarged the volume size of pocket D, which eliminated the harsh restriction to accommodate the third (P3) anchor residue of the peptide and expanded the peptide binding scope. Compared with 99^Tyr of SLA-1*0401, 99^Phe of SLA-1*13:01 could not form a conservative hydrogen bond with the backbone of the P3 residues, leading to fewer changes in the pocket properties but a significant decrease in quantitative of immunopeptidomes. This absent force could be compensated by the salt bridge formed by P1-E and 170^Arg. These data illustrate two distinguishing manners that show how micropolymorphism alters the peptide-binding plasticity of SLA-I alleles, verifying the sensitivity and accuracy of the RPLD-MS method for determining the peptide binding characteristics of MHC-I in vitro and helping to more accurately predict and identify MHC-I restricted epitopes.

Does Antigen Glycosylation Impact the HIV-Specific T Cell Immunity?

It is largely unknown how post-translational protein modifications, including glycosylation, impacts recognition of self and non-self T cell epitopes presented by HLA molecules. Data in the literature indicate that O- and N-linked glycosylation can survive epitope processing and influence antigen presentation and T cell recognition. In this perspective, we hypothesize that glycosylation of viral proteins and processed epitopes contribute to the T cell response to HIV. Although there is some evidence for T cell responses to glycosylated epitopes (glyco-epitopes) during viral infections in the literature, this aspect has been largely neglected for HIV. To explore the role of glyco-epitope specific T cell responses in HIV infection we conducted in silico and ex vivo immune studies in individuals with chronic HIV infection. We found that in silico viral protein segments with potentially glycosylable epitopes were less frequently targeted by T cells. Ex vivo synthetically added glycosylation moieties generally masked T cell recognition of HIV derived peptides. Nonetheless, in some cases, addition of simple glycosylation moieties produced neo-epitopes that were recognized by T cells from HIV infected individuals. Herein, we discuss the potential importance of these observations and compare limitations of the employed technology with new methodologies that may have the potential to provide a more accurate assessment of glyco-epitope specific T cell immunity. Overall, this perspective is aimed to support future research on T cells recognizing glycosylated epitopes in order to expand our understanding on how glycosylation of viral proteins could alter host T cell immunity against viral infections.

Polymorphisms of SOCS-1 Are Associated With a Rapid HIV Progression Rate

OBJECTIVES

Immune activation, among others driven by interferon (IFN)-α and IFN-γ activation, is a main feature of progressive HIV infection. Suppressor of cytokine signaling (SOCS) 1 and 3 are negative feedback regulators of the IFN-α and IFN-γ axis. Here, we analyzed the role of 9 single-nucleotide polymorphisms (SNPs) within SOCS-1 and SOCS-3 genes for their association with an HIV progression rate in a cohort of 318 rapid vs 376 slow progressors from the Swiss HIV Cohort Study.

DESIGN AND METHODS

We analyzed 9 SNPs, which we have identified in Swiss blood donors, in a cohort of HIV-infected patients (n = 1144), which have been categorized according to the decline in CD4 T-cell counts. In all the conducted analyses, we focused on the comparison between rapid and slow progressors with regard to SNPs in SOCS-1 and SOCS-3 and with regard to haplotypes using multivariate logistic regression models.

RESULTS

Three SOCS-1 SNPs (rs193779, rs33989964, and rs4780355) are associated with a risk reduction for rapid progression. Two of these SNPs, rs33989964 and rs4780355, are in strong linkage disequilibrium, forming a frequent haplotype. Homozygous carriers of this haplotype are also associated with a risk reduction for rapid progression. By contrast, the minor TT genotype of rs33977706 is associated with twice the risk for rapid progression. No associations have been observed for the 4 SOCS-3 SNPs or the major SOCS-3 haplotypes.

CONCLUSIONS

Our data suggest that SNPs in SOCS-1 are associated with HIV disease progression and speak in favor that immune activation is causal for the progressive immunodeficiency.

HIV-1 and human genetic variation

Over the past four decades, research on the natural history of HIV infection has described how HIV wreaks havoc on human immunity and causes AIDS. HIV host genomic research, which aims to understand how human genetic variation affects our response to HIV infection, has progressed from early candidate gene studies to recent multi-omic efforts, benefiting from spectacular advances in sequencing technology and data science. In addition to invading cells and co-opting the host machinery for replication, HIV also stably integrates into our own genome. The study of the complex interactions between the human and retroviral genomes has improved our understanding of pathogenic mechanisms and suggested novel preventive and therapeutic approaches against HIV infection.

HLA tapasin independence: broader peptide repertoire and HIV control

Human leukocyte antigen (HLA) class I allotypes vary in their ability to present peptides in the absence of tapasin, an essential component of the peptide loading complex. We quantified tapasin dependence of all allotypes that are common in European and African Americans (n = 97), which revealed a broad continuum of values. Ex vivo examination of cytotoxic T cell responses to the entire HIV-1 proteome from infected subjects indicates that tapasin-dependent allotypes present a more limited set of distinct peptides than do tapasin-independent allotypes, data supported by computational predictions. This suggests that variation in tapasin dependence may impact the strength of the immune responses by altering peptide repertoire size. In support of this model, we observed that individuals carrying HLA class I genotypes characterized by greater tapasin independence progress more slowly to AIDS and maintain lower viral loads, presumably due to increased breadth of peptide presentation. Thus, tapasin dependence level, like HLA zygosity, may serve as a means to restrict or expand breadth of the HLA-I peptide repertoire across humans, ultimately influencing immune responses to pathogens and vaccines.

Chemokine receptor gene polymorphisms and COVID-19: Could knowledge gained from HIV/AIDS be important?

Emerging results indicate that an uncontrolled host immune response, leading to a life-threatening condition called cytokine release syndrome (also termed "cytokine storm"), is the major driver of pathology in severe COVID-19. In this pandemic, considerable effort is being focused on identifying host genomic factors that increase susceptibility or resistance to the complications of COVID-19 and translating these findings to improved patient care. In this regard, the chemokine receptor-ligand nexus has been reported as potentially important in severe COVID-19 disease pathogenesis and its treatment. Valuable genomic insights into the chemokine receptor-ligand nexus have been gained from HIV infection and disease progression studies. Applying that knowledge, together with newly discovered potential host genomic factors associated with COVID-19, may lead to a more comprehensive understanding of the pathogenesis and treatment outcomes in COVID-19 patients.

New Knowledge About CCR5, HIV Infection, and Disease Progression: Is "Old" Still Valuable?

C-C chemokine receptor (CCR) 5 (CCR5) is the main HIV-1 coreceptor involved in virus entry and cell-to-cell spread during acute and chronic infections: such CCR5 and T cell tropic viruses are adapted to and replicate in CD4⁺ memory T cells. Polymorphisms in CCR5 regulate CCR5 expression, which, in turn, influences HIV infection acquisition and subsequent disease progression. Among these polymorphisms, a 32-bp deletion in the CCR5 open reading frame (CCR5 Δ32) and a single nucleotide polymorphism (SNP) in the promoter (-2459G/A) are the most well-characterized polymorphisms. CCR5 Δ32 provides partial to full protection against HIV infection and, therefore, serves as a basis for gene deletion studies attempting to achieve a permanent HIV cure. Recent studies have discovered that certain SNPs in the CCR region, not within CCR5, also affect CCR5 expression, HIV infection, and disease progression. Although these studies provide further valuable information regarding the role of human genetic variation in HIV/AIDS, they did not incorporate -2459G/A. In this article, the author summarizes the knowledge gained through the discovery of these new SNPs and introduces the idea that by not incorporating -2459G/A, less comprehensive conclusions may have been reached. Until a strategy that delivers a cure to the millions is found, every piece of information that may help curtail the HIV/AIDS threat to public health should be considered useful.

An assessment of toll-like receptor 7 and 8 gene polymorphisms with susceptibility to HIV-1 infection, AIDS development and response to antiretroviral therapy

Toll-like receptors (TLRs) play an important role in activating the innate immune response, inducing inflammation and initiating the adaptive immune response. In this study, we assess the influence of TLR7 and TLR8 gene polymorphisms on HIV-1 susceptibility, AIDS development, and treatment outcomes. The TLR7 and TLR8 single nucleotide polymorphisms (SNPs) were genotyped through real-time PCR in 222 patients living with HIV-1 and 141 healthy controls. Frequencies of the TLR7-IVS2-151 G/A and TLR7-IVS1 + 1817 G/T genotypes and alleles were not significantly increased in patients with HIV-1 infection compared to healthy controls both in males and females. Whereas, males carrying TLR8 Met allele were twice susceptible to HIV-1 infection compared to subjects with A allele (OR = 2.04, 95 % CI 1.10-3.76; p = 0.021). Interestingly, for TLR8-129 G/C, both males and females carrying G allele and GG genotype, respectively were significantly associated with HIV-1 infection (p < 0.0001). Moreover, the TLR7 IVS1 + 1817 G/T and the TLR8 rs3764880 were associated with protection to progress the AIDS stage in male and female, respectively (p < 0.05). Males carrying TLR7 IVS2-151-A allele showed a significant increased level of HIV-1 viral load pre-treatment, in comparison with individuals carrying the G allele (p-value = 0.036). Additionally, males carrying TLR8 Met allele showed statistically higher HIV viral load at baseline (p-value = 0.04) and after treatment (p-value = 0.013). Regarding CD4 + T cell counts, no significant association was found with TLR7 and TLR8 SNPs before and after antiretroviral treatment. This data demonstrates that TLR8 polymorphisms could affect HIV-1 infection. Moreover, an association between TLR7 IVS2-151-A and TLR8 Met alleles and plasma HIV viral load level was found.

Polymorphisms of HLA-B: influences on assembly and immunity

The major histocompatibility class I (MHC-I) complex functions in innate and adaptive immunity, mediating surveillance of the subcellular environment. In humans, MHC-I heavy chains are encoded by three genes: the human leukocyte antigen (HLA)-A, HLA-B, and HLA-C. These genes are highly polymorphic, which results in the expression, typically, of six different HLA class I (HLA-I) proteins on the cell surface, and the presentation of diverse peptide antigens to CD8+ T cells for broad surveillance against many pathogenic conditions. Recent studies of HLA-B allotypes show that the polymorphisms, not surprisingly, also significantly impact protein folding and assembly pathways. The use of non-canonical assembly routes and the generation of non-canonical HLA-B conformers has consequences for immune receptor interactions and disease therapies.

Association Between Single-Nucleotide Polymorphisms in HLA Alleles and Human Immunodeficiency Virus Type 1 Viral Load in Demographically Diverse, Antiretroviral Therapy-Naive Participants From the Strategic Timing of AntiRetroviral Treatment Trial

The impact of variation in host genetics on replication of human immunodeficiency virus type 1 (HIV-1) in demographically diverse populations remains uncertain. In the current study, we performed a genome-wide screen for associations of single-nucleotide polymorphisms (SNPs) to viral load (VL) in antiretroviral therapy-naive participants (n = 2440) with varying demographics from the Strategic Timing of AntiRetroviral Treatment (START) trial. Associations were assessed using genotypic data generated by a customized SNP array, imputed HLA alleles, and multiple linear regression. Genome-wide significant associations between SNPs and VL were observed in the major histocompatibility complex class I region (MHC I), with effect sizes ranging between 0.14 and 0.39 log10 VL (copies/mL). Supporting the SNP findings, we identified several HLA alleles significantly associated with VL, extending prior observations that the (MHC I) is a major host determinant of HIV-1 control with shared genetic variants across diverse populations and underscoring the limitations of genome-wide association studies as being merely a screening tool.

Partner HIV Serostatus Impacts Viral Load, Genital HIV Shedding, and Immune Activation in HIV-Infected Individuals

Studies of seronegative individuals in HIV discordant relationships provide important insights into the effects of HIV exposure on the seronegative partner, but few have examined the impact of partner serostatus on disease progression in seropositive individuals. We investigated the impact of HIV serostatus on clinical and biological factors influencing HIV disease progression in 337 HIV-infected heterosexual individuals in stable long-term HIV-seroconcordant or HIV-serodiscordant relationships. Seroconcordant individuals had significantly higher plasma viral loads (pVLs) than HIV-infected partners in serodiscordant partnerships [4.4 log10 copies RNA/mL (interquartile range 3.7-5.0) versus 3.9 (3.3-4.5), P < 0.0001], irrespective of gender. pVLs correlated inversely with CD4 T-cell counts, although CD4 counts did not differ significantly between seroconcordant and serodiscordant individuals. HIV+ seroconcordant individuals had higher frequencies of CCR5 CD4 and CD8 T cells (P = 0.03 and P = 0.02, respectively) than HIV+ individuals in serodiscordant relationships and higher concentrations of plasma IL-1β (P = 0.04), TNF-α (P = 0.02), and IL-10 (P = 0.02). Activated CD4 T-cell frequencies and TNF-α were the most influential in determining variation in pVLs, independently of CD4 counts. In addition, HIV+ seroconcordant women had significantly higher genital VLs (gVLs) than HIV+ women in serodiscordant relationships (P < 0.001), with pVLs correlating significantly with gVLs (Rho = 0.65, P < 0.0001). Cervical and blood T-cell activation tended to correlate positively, although partner seroconcordance did not influence genital T-cell activation. We conclude that HIV+ seroconcordant individuals have higher frequencies of activated, CCR5-expressing T cells in blood and higher pVLs and gVLs than their HIV+ counterparts in discordant relationships, which could translate to faster disease progression or larger viral reservoir.

Differences in MHC-B diversity and KIR epitopes in two populations of wild chimpanzees

The major histocompatibility complex (MHC) class I genes play a critical role within the immune system, both by the presentation of antigens from intracellular pathogens to immunocompetent cells and by the interaction with killer cell immunoglobulin-like receptors (KIR) on natural killer cells (NK cells). Genes of the MHC are highly diverse, and MHC variation can have effects on the immune functionality of individuals; hence, comparisons of MHC diversity among closely related phylogenetic taxa may give insight into the factors responsible for the shaping of its diversity. The four geographically separated chimpanzee subspecies differ in their overall genetic diversity, have different population histories, and are confronted with different pathogens in their natural habitat, all of which may affect MHC class I DNA sequence diversity. Here, we compare the MHC-B exon two DNA sequence diversity from 24 wild western and 46 wild eastern chimpanzees using necropsy and noninvasively collected fecal samples, respectively. We found a higher MHC-B exon two nucleotide diversity, in our western than eastern chimpanzees. The inclusion of previously published MHC-B exon two data from other western and eastern chimpanzees supported this finding. In addition, our results confirm and extend the finding of a very low C1 epitope frequency at eastern chimpanzee MHC-B molecules, which likely affects the ability of these molecules to interact with NK cells. While the understanding of the differing pathogen environments encountered by disparate populations of a species is a challenging endeavor, these findings highlight the potential for these pathogens to selectively shape immune system variation.

Dual CCR5/CCR2 targeting: opportunities for the cure of complex disorders

The chemokine system mediates acute inflammation by driving leukocyte migration to damaged or infected tissues. However, elevated expression of chemokines and their receptors can contribute to chronic inflammation and malignancy. Thus, great effort has been taken to target these molecules. The first hint of the druggability of the chemokine system was derived from the role of chemokine receptors in HIV infection. CCR5 and CXCR4 function as essential co-receptors for HIV entry, with the former accounting for most new HIV infections worldwide. Not by chance, an anti-CCR5 compound, maraviroc, was the first FDA-approved chemokine receptor-targeting drug. CCR5, by directing leukocytes to sites of inflammation and regulating their activation, also represents an important player in the inflammatory response. This function is shared with CCR2 and its selective ligand CCL2, which constitute the primary chemokine axis driving the recruitment of monocytes/macrophages to inflammatory sites. Both receptors are indeed involved in the pathogenesis of several immune-mediated diseases, and dual CCR5/CCR2 targeting is emerging as a more efficacious strategy than targeting either receptor alone in the treatment of complex human disorders. In this review, we focus on the distinctive and complementary contributions of CCR5 and CCR2/CCL2 in HIV infection, multiple sclerosis, liver fibrosis and associated hepatocellular carcinoma. The emerging therapeutic approaches based on the inhibition of these chemokine axes are highlighted.

Human Genetic Variation and HIV/AIDS in Papua New Guinea: Time to Connect the Dots

PURPOSE OF REVIEW

Human genetic polymorphisms known to influence HIV acquisition and disease progression occur in Papua New Guinea (PNG). However, no genetic association study has been reported so far. In this article, we review research findings, with a view to stimulate genotype-to-phenotype research.

RECENT FINDINGS

PNG, a country in Oceania, has a high prevalence of HIV and many sexually transmitted infections. While limited data is available from this country regarding the distribution of human genetic polymorphisms known to influence clinical outcomes of HIV/AIDS, genetic association studies are lacking. Our studies, in the past decade, have revealed that polymorphisms in chemokine receptor-ligand (CCR2-CCR5, CXCL12), innate immune (Toll-like receptor, β-defensin), and antiretroviral drug-metabolism enzyme (CYP2B6, UGT2B7) genes are prevalent in PNG. Although our results need to be validated in further studies, it is urgent to pursue large-scale, comprehensive genetic association studies that include these as well as additional genetic polymorphisms.

Personal Genetic Information about HIV: Research Participants' Views of Ethical, Social, and Behavioral Implications

BACKGROUND

Personal genetic information (PGI) about HIV is produced in research and entering the clinic and direct-to-consumer market, but little consideration has been given to ethical and social issues, public perspectives, and potential behavioral implications.

OBJECTIVES

This research queried the views of research participants at risk for or infected with HIV, exploring their perspectives on HIV-related PGI and its ethical, social, and behavioral implications.

METHODS

We used focus groups to collect rich information about participants' perspectives on the ethical, social, and behavioral implications of PGI about HIV and host genetic research. We evaluated their reactions to three different types of genetic variants: those that made them more susceptible to HIV, more protected from or resistant to HIV, or more likely to transmit HIV to others.

RESULTS

Overall, participants wanted PGI about HIV. Their reasons included a mix of personal or family health benefit and benefit to others, which varied in emphasis depending on variant type. While susceptibility variant information was seen primarily in terms of personal or family health benefit, for transmissibility and protective variant information, benefit to others emerged as a major reason for wanting PGI about HIV. Participants thought transmissibility variant information would help them prevent others from becoming infected, and protective variant information would allow them to volunteer for targeted research to help treat, cure, or prevent HIV. Possible harms were raised regarding the tendencies among some individuals to increase risky behavior with modulations in perceived risk. Potential behavioral implications were seen as significant, though complex, reflecting multifaceted risk perceptions.

CONCLUSIONS

Our study adds to the evidence that participants in genetic research, across disease type, have a strong desire for PGI. For participants in research on the genetics of HIV, and potentially other infectious diseases, their desire for PGI is grounded in a perceived duty not to infect others, where they feel a moral responsibility regarding research participation and behavior change. Wider dissemination of HIV-related PGI may well increase research participation, but could have mixed effects on risk behavior. More research is needed on the implications of different variant types of PGI beyond susceptibility factors, especially protective variants or resistance factors.

CCR5AS lncRNA variation differentially regulates CCR5, influencing HIV disease outcome

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.

HIV-1 DNA sequence diversity and evolution during acute subtype C infection

Little is known about the genotypic make-up of HIV-1 DNA genomes during the earliest stages of HIV-1 infection. Here, we use near-full-length, single genome next-generation sequencing to longitudinally genotype and quantify subtype C HIV-1 DNA in four women identified during acute HIV-1 infection in Durban, South Africa, through twice-weekly screening of high-risk participants. In contrast to chronically HIV-1-infected patients, we found that at the earliest phases of infection in these four participants, the majority of viral DNA genomes are intact, lack APOBEC-3G/F-associated hypermutations, have limited genome truncations, and over one year show little indication of cytotoxic T cell-driven immune selections. Viral sequence divergence during acute infection is predominantly fueled by single-base substitutions and is limited by treatment initiation during the earliest stages of disease. Our observations provide rare longitudinal insights of HIV-1 DNA sequence profiles during the first year of infection to inform future HIV cure research.

Immune Control of HIV

The human immunodeficiency virus (HIV) infection of the immune cells expressing the cluster of differentiation 4 cell surface glycoprotein (CD4⁺ cells) causes progressive decline of the immune system and leads to the acquired immunodeficiency syndrome (AIDS). The ongoing global HIV/AIDS pandemic has already claimed over 35 million lives. Even after 37 years into the epidemic, neither a cure is available for the 37 million people living with HIV (PLHIV) nor is a vaccine discovered to avert the millions of new HIV infections that continue to occur each year. If left untreated, HIV infection typically progresses to AIDS and, ultimately, causes death in a majority of PLHIV. The recommended combination antiretroviral therapy (cART) suppresses virus replication and viremia, prevents or delays progression to AIDS, reduces transmission rates, and lowers HIV-associated mortality and morbidity. However, because cART does not eliminate HIV, and an enduring pool of infected resting memory CD4⁺ T cells (latent HIV reservoir) is established early on, any interruption to cART leads to a relapse of viremia and disease progression. Hence, strict adherence to a life-long cART regimen is mandatory for managing HIV infection in PLHIV. The HIV-1-specific cytotoxic T cells expressing the CD8 glycoprotein (CD8⁺ CTL) limit the virus replication in vivo by recognizing the viral antigens presented by human leukocyte antigen (HLA) class I molecules on the infected cell surface and killing those cells. Nevertheless, CTLs fail to durably control HIV-1 replication and disease progression in the absence of cART. Intriguingly, <1% of cART-naive HIV-infected individuals called elite controllers/HIV controllers (HCs) exhibit the core features that define a HIV-1 "functional cure" outcome in the absence of cART: durable viral suppression to below the limit of detection, long-term non-progression to AIDS, and absence of viral transmission. Robust HIV-1-specific CTL responses and prevalence of protective HLA alleles associated with enduring HIV-1 control have been linked to the HC phenotype. An understanding of the molecular mechanisms underlying the CTL-mediated suppression of HIV-1 replication and disease progression in HCs carrying specific protective HLA alleles may yield promising insights towards advancing the research on HIV cure and prophylactic HIV vaccine.

Delayed disease progression in HIV-2: the importance of TRIM5α and the retroviral capsid

HIV-2 is thought to have entered the human population in the 1930s through cross-species transmission of SIV from sooty mangabeys in West Africa. Unlike HIV-1, HIV-2 has not led to a global pandemic, and recent data suggest that HIV-2 prevalence is declining in some West African states where it was formerly endemic. Although many early isolates of HIV-2 were derived from patients presenting with AIDS-defining illnesses, it was noted that a much larger proportion of HIV-2-infected subjects behaved as long-term non-progressors (LTNP) than their HIV-1-infected counterparts. Many HIV-2-infected adults are asymptomatic, maintaining an undetectable viral load for over a decade. However, despite lower viral loads, HIV-2 progresses to clinical AIDS without therapeutic intervention in most patients. In addition, successful treatment with anti-retroviral therapy (ART) is more challenging than for HIV-1. HIV-2 is significantly more sensitive to restriction by host restriction factor tripartite motif TRIM5α than HIV-1, and this difference in sensitivity is linked to differences in capsid structure. In this review we discuss the determinants of HIV-2 disease progression and focus on the important interactions between TRIM5α and HIV-2 capsid in long-term viral control.

Risk Factors and Pathogenesis of HIV-Associated Neurocognitive Disorder: The Role of Host Genetics

Neurocognitive impairments associated with human immunodeficiency virus (HIV) infection remain a considerable health issue for almost half the people living with HIV, despite progress in HIV treatment through combination antiretroviral therapy (cART). The pathogenesis and risk factors of HIV-associated neurocognitive disorder (HAND) are still incompletely understood. This is partly due to the complexity of HAND diagnostics, as phenotypes present with high variability and change over time. Our current understanding is that HIV enters the central nervous system (CNS) during infection, persisting and replicating in resident immune and supporting cells, with the subsequent host immune response and inflammation likely adding to the development of HAND. Differences in host (human) genetics determine, in part, the effectiveness of the immune response and other factors that increase the vulnerability to HAND. This review describes findings from studies investigating the role of human host genetics in the pathogenesis of HAND, including potential risk factors for developing HAND. The similarities and differences between HAND and Alzheimer's disease are also discussed. While some specific variations in host genes regulating immune responses and neurotransmission have been associated with protection or risk of HAND development, the effects are generally small and findings poorly replicated. Nevertheless, a few specific gene variants appear to affect the risk for developing HAND and aid our understanding of HAND pathogenesis.

The CCR5-Delta32 Genetic Polymorphism and HIV-1 Infection Susceptibility: a Meta-analysis

The CC chemokine receptor 5 (CCR5) is a chemokine receptor which is widely expressed in several immune cells involved in the inflammatory responses. Previous published studies revealed the relation of the CCR5 gene (CCR5-delta32) with the risk of HIV-1 infection, but the results are debatable and inconclusive. Here by meta-analysis, we have systematically evaluated the relation between the CCR5-delta32 polymorphism and the risk of HIV-1 infection. A comprehensive search in PubMed, EMBASE, CNKI, Cochrane Library, and WanFang database was performed up to April 15, 2018. The pooled odds ratio (ORs) along with its 95% credible interval (95%CI) was used to evaluate the relation between the CCR5-delta32 polymorphism and HIV-1 infection risk. The study included 24 case-control studies involving 4,786 HIV-1 infection patients and 6,283 controls. Compared with the wild-type homozygous genotypes, the results showed that the CCR5-delta32 heterozygotes (OR=1.16, 95%CI=1.02-1.32) had an increased susceptibility to HIV-1 and the delta32 homozygous (OR=0.25, 95%CI=0.09-0.68) had significantly reduced the susceptibility to HIV-1 for healthy controls. Moreover, we have found the delta32 allele carriers (OR=0.71, 95%CI=0.54-0.94) had significantly cut down the HIV-1 infection susceptibility when using exposed uninfected (EU) as controls. We also conducted the stratified analysis by ethnicity, and there significant association was detected in Caucasian in delta32 allele carrier genotype. To summarize, our meta-analysis suggests that the CCR5-delta32 homozygous genotype (delta32/delta32) confer possible protection against HIV-1, especially the exposed uninfected groups.

Human CCL3L1 copy number variation, gene expression, and the role of the CCL3L1-CCR5 axis in lung function

Background: The CCL3L1-CCR5 signaling axis is important in a number of inflammatory responses, including macrophage function, and T-cell-dependent immune responses. Small molecule CCR5 antagonists exist, including the approved antiretroviral drug maraviroc, and therapeutic monoclonal antibodies are in development. Repositioning of drugs and targets into new disease areas can accelerate the availability of new therapies and substantially reduce costs. As it has been shown that drug targets with genetic evidence supporting their involvement in the disease are more likely to be successful in clinical development, using genetic association studies to identify new target repurposing opportunities could be fruitful. Here we investigate the potential of perturbation of the CCL3L1-CCR5 axis as treatment for respiratory disease. Europeans typically carry between 0 and 5 copies of CCL3L1 and this multi-allelic variation is not detected by widely used genome-wide single nucleotide polymorphism studies.  Methods: We directly measured the complex structural variation of CCL3L1 using the Paralogue Ratio Test and imputed (with validation) CCR5del32 genotypes in 5,000 individuals from UK Biobank, selected from the extremes of the lung function distribution, and analysed DNA and RNAseq data for CCL3L1 from the 1000 Genomes Project. Results: We confirmed the gene dosage effect of CCL3L1 copy number on CCL3L1 mRNA expression levels.  We found no evidence for association of CCL3L1 copy number or CCR5del32 genotype with lung function. Conclusions: These results suggest that repositioning CCR5 antagonists is unlikely to be successful for the treatment of airflow obstruction.

Human genetics of infectious diseases: Unique insights into immunological redundancy

For almost any given human-tropic virus, bacterium, fungus, or parasite, the clinical outcome of primary infection is enormously variable, ranging from asymptomatic to lethal infection. This variability has long been thought to be largely determined by the germline genetics of the human host, and this is increasingly being demonstrated to be the case. The number and diversity of known inborn errors of immunity is continually increasing, and we focus here on autosomal and X-linked recessive traits underlying complete deficiencies of the encoded protein. Schematically, four types of infectious phenotype have been observed in individuals with such deficiencies, each providing information about the redundancy of the corresponding human gene, in terms of host defense in natural conditions. The lack of a protein can confer vulnerability to a broad range of microbes in most, if not all patients, through the disruption of a key immunological component. In such cases, the gene concerned is of low redundancy. However, the lack of a protein may also confer vulnerability to a narrow range of microbes, sometimes a single pathogen, and not necessarily in all patients. In such cases, the gene concerned is highly redundant. Conversely, the deficiency may be apparently neutral, conferring no detectable predisposition to infection in any individual. In such cases, the gene concerned is completely redundant. Finally, the lack of a protein may, paradoxically, be advantageous to the host, conferring resistance to one or more infections. In such cases, the gene is considered to display beneficial redundancy. These findings reflect the current state of evolution of humans and microbes, and should not be considered predictive of redundancy, or of a lack of redundancy, in the distant future. Nevertheless, these observations are of potential interest to present-day biologists testing immunological hypotheses experimentally and physicians managing patients with immunological or infectious conditions.

Human CCL3L1 copy number variation, gene expression, and the role of the CCL3L1-CCR5 axis in lung function

Background: The CCL3L1-CCR5 signaling axis is important in a number of inflammatory responses, including macrophage function, and T-cell-dependent immune responses. Small molecule CCR5 antagonists exist, including the approved antiretroviral drug maraviroc, and therapeutic monoclonal antibodies are in development. Repositioning of drugs and targets into new disease areas can accelerate the availability of new therapies and substantially reduce costs. As it has been shown that drug targets with genetic evidence supporting their involvement in the disease are more likely to be successful in clinical development, using genetic association studies to identify new target repurposing opportunities could be fruitful. Here we investigate the potential of perturbation of the CCL3L1-CCR5 axis as treatment for respiratory disease. Europeans typically carry between 0 and 5 copies of CCL3L1 and this multi-allelic variation is not detected by widely used genome-wide single nucleotide polymorphism studies.  Methods: We directly measured the complex structural variation of CCL3L1 using the Paralogue Ratio Test and imputed (with validation) CCR5del32 genotypes in 5,000 individuals from UK Biobank, selected from the extremes of the lung function distribution, and analysed DNA and RNAseq data for CCL3L1 from the 1000 Genomes Project. Results: We confirmed the gene dosage effect of CCL3L1 copy number on CCL3L1 mRNA expression levels.  We found no evidence for association of CCL3L1 copy number or CCR5del32 genotype with lung function. Conclusions: These results suggest that repositioning CCR5 antagonists is unlikely to be successful for the treatment of airflow obstruction.

Biomarkers of Progression after HIV Acute/Early Infection: Nothing Compares to CD4⁺ T-cell Count?

Progression of HIV infection is variable among individuals, and definition disease progression biomarkers is still needed. Here, we aimed to categorize the predictive potential of several variables using feature selection methods and decision trees. A total of seventy-five treatment-naïve subjects were enrolled during acute/early HIV infection. CD4⁺ T-cell counts (CD4TC) and viral load (VL) levels were determined at enrollment and for one year. Immune activation, HIV-specific immune response, Human Leukocyte Antigen (HLA) and C-C chemokine receptor type 5 (CCR5) genotypes, and plasma levels of 39 cytokines were determined. Data were analyzed by machine learning and non-parametric methods. Variable hierarchization was performed by Weka correlation-based feature selection and J48 decision tree. Plasma interleukin (IL)-10, interferon gamma-induced protein (IP)-10, soluble IL-2 receptor alpha (sIL-2Rα) and tumor necrosis factor alpha (TNF-α) levels correlated directly with baseline VL, whereas IL-2, TNF-α, fibroblast growth factor (FGF)-2 and macrophage inflammatory protein (MIP)-1β correlated directly with CD4⁺ T-cell activation (p < 0.05). However, none of these cytokines had good predictive values to distinguish "progressors" from "non-progressors". Similarly, immune activation, HIV-specific immune responses and HLA/CCR5 genotypes had low discrimination power. Baseline CD4TC was the most potent discerning variable with a cut-off of 438 cells/μL (accuracy = 0.93, κ-Cohen = 0.85). Limited discerning power of the other factors might be related to frequency, variability and/or sampling time. Future studies based on decision trees to identify biomarkers of post-treatment control are warrantied.

The HLA-B landscape of Africa: Signatures of pathogen-driven selection and molecular identification of candidate alleles to malaria protection

Human leukocyte antigen (HLA) genes play a key role in the immune response to infectious diseases, some of which are highly prevalent in specific environments, like malaria in sub-Saharan Africa. Former case-control studies showed that one particular HLA-B allele, B*53, was associated with malaria protection in Gambia, but this hypothesis was not tested so far within a population genetics framework. In this study, our objective was to assess whether pathogen-driven selection associated with malaria contributed to shape the HLA-B genetic landscape of Africa. To that aim, we first typed the HLA-A and -B loci in 484 individuals from 11 populations living in different environments across the Sahel, and we analysed these data together with those available for 29 other populations using several approaches including linear modelling on various genetic, geographic and environmental parameters. In addition to relevant signatures of populations' demography and migrations history in the genetic differentiation patterns of both HLA-A and -B loci, we found that the frequencies of three HLA alleles, B*53, B*78 and A*74, were significantly associated with Plasmodium falciparum malaria prevalence, suggesting their increase through pathogen-driven selection in malaria-endemic environments. The two HLA-B alleles were further identified, by high-throughput sequencing, as B*53:01:01 (in putative linkage disequilibrium with one HLA-C allele, C*04:01:01:01) and B*78:01 in all but one individuals tested, making them appropriate candidates to malaria protection. These results highlight the role of environmental factors in the evolution of the HLA polymorphism and open key perspectives for functional studies focusing on HLA peptide-binding properties.