HLA-B*57 and IFNL4-related polymorphisms are associated with protection against HIV-1 disease progression in controllers

Background

HIV-1-controllers maintain HIV-1 viremia at low levels (normally <2000 HIV-RNA copies/mL) without antiretroviral treatment. However, some HIV-1-controllers have evidence of immunologic progression with marked CD4⁺T-cell decline. We investigated host genetic factors associated with protection against CD4⁺T-cell loss in HIV-1-controllers.

Methods

We analysed the association of interferon lambda 4 (IFNL4)-related polymorphisms and HLA-B haplotypes within Long Term Non-Progressor HIV-1-controllers ((LTNP-C), defined by maintaining CD4⁺T-cells counts >500 cells/mm³ for more than 7 years after HIV-1 diagnosis) versus non-LTNP-C, who developed CD4⁺T-cells counts <500 cells/mm³ Both a Spanish study cohort (n=140) and an international validation cohort (n=914) were examined. Additionally, in a subgroup of individuals HIV-1-specific T-cell responses and soluble cytokines were analysed RESULTS: HLA-B*57 was independently associated with the LTNP-C phenotype (OR=3.056 (1.029-9.069) p=0.044 and OR=1.924 (1.252-2.957) p=0.003) while IFNL4 genotypes represented independent factors for becoming non-LTNP-C (TT/TT, ss469415590, OR=0.401 (0.171-0.942) p=0.036 or A/A, rs12980275, OR=0.637 (0.434-0.934) p=0.021) in the Spanish and validation cohort, respectively, after adjusting for sex, age at HIV-1 diagnosis, IFNL4-related polymorphisms and different HLA-B haplotypes. LTNP-C showed lower plasma IP-10 (p=0.019) and higher IFN-γ (p=0.02) levels than the HIV-1-controllers with diminished CD4⁺T-cell numbers. Moreover, LTNP-C exhibited higher quantities of IL2⁺CD57^- and IFN-γ⁺CD57^- HIV-1-specific CD8⁺T-cells (p=0.002 and 0.041, respectively) than non-LTNP-C.

Conclusions

We have defined genetic markers able to segregate stable HIV-1-controllers from those who experience CD4⁺T-cell decline. These findings allow for identification of HIV-1-controllers at risk for immunologic progression, and provide avenues for personalized therapeutic interventions and precision medicine for optimizing clinical care of these individuals.

Hepatitis C virus replication in Caucasian HIV controllers

Whether HIV controllers, patients who spontaneously control HIV viraemia, are able to control hepatitis C virus (HCV) infection, in terms of spontaneous clearance or lower HCV replication, is not well understood. To assess to what extent Caucasian HIV controllers are able to control HCV replication and potential associated factors, plasma HIV-1 and HCV RNA levels, anti-HCV antibodies, HCV genotype and human leucocyte antigens (HLA) typing were determined in samples from 75 HIV controllers (33 viraemic controllers, <1000 HIV-1 RNA copies/mL, and 42 elite controllers, <40 HIV-1 RNA copies/mL) and compared with 261 HIV-infected noncontrollers. We did not find differences in the HCV spontaneous clearance rates between groups. However, we interestingly found a lower HCV viral load in HIV controllers, alongside a different distribution of HCV genotypes in relation to the comparison group. In addition, HLA-B57 was associated with a lower HCV viral load in the control group and HIV controllers, and conversely, HLA-B35 with higher HCV viral load in HIV controllers. The subrepresentation of HCV genotype 1 and the overrepresentation of HLA-B57 only partly explained the lower HCV viral load found in HIV controllers. In fact, HIV controller status was independently associated with lower HCV viral load, together with HCV genotype non-1, the presence of HLA-B57 and absence of HLA-B35. Caucasian HIV controllers are able to better control HCV replication, in terms of lower HCV viral load levels. These findings support the idea that some common host mechanisms are involved in the defence against these two persistent infections.

HIV envelope protein inhibits MHC class I presentation of a cytomegalovirus protective epitope

CTL recognize peptides that derive from viral protein Ags by proteolytic processing and are presented by MHC class I molecules. In this study we tested whether coexpression of viral Ags in the same cell leads to competition between them. To this end, two L(d)-restricted epitopes derived from HIV-1 envelope gp160 (ENV) and from CMV pp89 phosphoprotein were coexpressed. HIV ENV strain IIIB, but not MN variant, impaired recognition by specific CTL of CMV pp89 epitope 9pp89. Susceptibility to inhibition after ENV coexpression was inversely related to the amount of antigenic 9pp89 peptide processed from different antigenic constructs. In line with it, competition decreased the yield of naturally processed antigenic 9pp89 peptide bound to MHC class I molecules in coinfected cells. Also, point mutants of the presenting MHC class I molecule differed in their competition pattern. Collectively, the data imply that competition operates at the step of MHC-peptide complex assembly or stabilization. We conclude that, although not the rule, in certain combinations there is interference between different Ags expressed in the same cell and presented by the same MHC class I allele. These studies have implications for vaccine development and for understanding immunodominance.

Generation of MHC class I peptide antigens by protein processing in the secretory route by furin

Cytosolic degradation of endogenously synthesized proteins by the proteasome and translocation of processed peptides to the endoplasmic reticulum by the transporters associated with antigen presentation constitutes the classical route for antigen presentation by MHC class I proteins. We have previously defined an alternative pathway in the secretory route involving proteolytic maturation of precursor proproteins for chimeric hepatitis B virus secretory core protein HBe containing a class I epitope at its carboxy-terminus. We extend those results by demonstrating that intracellular delivery of the trans-Golgi network protease furin increases both proteolytic maturation and antigen presentation of the chimeric HBe proteins. An additional class I epitope from the HIV envelope gp160 protein was inserted into this COOH-terminal region of two different chimeric HBe proteins. This epitope was also presented to CTL in a transporter-independent manner involving furin, and protein maturation and antigen presentation were also enhanced by furin over-expression. Presentation of this second epitope was restricted by a different class I allele, thus suggesting that antigen presentation by this new pathway may apply to any antigenic epitope and class I molecule. These results define the furin proteolytic maturation pathway of HBe in the secretory route as a general antigen processing route for MHC class I presentation.

Sequential cleavage by metallopeptidases and proteasomes is involved in processing HIV-1 ENV epitope for endogenous MHC class I antigen presentation

Antigenic peptides derived from viral proteins by multiple proteolytic cleavages are bound by MHC class I molecules and recognized by CTL. Processing predominantly takes place in the cytosol of infected cells by the action of proteasomes. To identify other proteases involved in the endogenous generation of viral epitopes, specifically those derived from proteins routed to the secretory pathway, we investigated presentation of the HIV-1 ENV 10-mer epitope 318RGPGRAFVTI327 (p18) to specific CTL in the presence of diverse protease inhibitors. Both metalloproteinase and proteasome inhibitors decreased CTL recognition of the p18 epitope expressed from either native gp160 or from a chimera based on the hepatitis B virus secretory core protein as carrier protein. Processing of this epitope from both native ENV and the hepatitis B virus secretory core chimeric protein appeared to proceed by a TAP-dependent pathway that involved sequential cleavage by proteasomes and metallo-endopeptidases; however, other protease activities could replace the function of the lactacystin-sensitive proteasomes. By contrast, in a second TAP-independent pathway we detected no contribution of metallopeptidases for processing the ENV epitope from the chimeric protein. These results show that, in the classical TAP-dependent MHC class I pathway, endogenous Ag processing of viral proteins to yield the p18 10-mer epitope requires metallo-endopeptidases in addition to proteasomes.

Intracellular rate-limiting steps in MHC class I antigen processing

Quantitative aspects of the endogenous pathway of Ag processing and presentation by MHC class I molecules to CD8+ CTL were analyzed over a wide range of Ag expression in recombinant vaccinia virus-infected cells expressing beta-galactosidase as model Ag. Only the amount of starting Ag was varied, leaving other factors unaltered. Below a certain level of Ag synthesis, increasing protein amounts led to a sharp rise in recognition by CTL. Higher levels of Ag expression led to a saturation point, which intracellularly limited the number of naturally processed peptides bound to MHC and thereby also CTL recognition. The rate-limiting step was located at the binding of the antigenic peptide to MHC inside the vaccinia virus-infected cell or before this event.

Major histocompatibility complex class I viral antigen processing in the secretory pathway defined by the trans-Golgi network protease furin

Classical antigen presentation by major histocompatibility complex class I molecules involves cytosolic processing of endogenously synthesized antigens by proteasomes and translocation of processed peptides into the endoplasmic reticulum (ER) by transporters associated with antigen presentation (TAP). Alternative pathways for processing of endogenous antigens, generally involving the ER, have been suggested but not fully proved. We analyzed the potential for class I presentation of proteolytic maturation of secretory antigens in the exocytic pathway. We found that hepatitis B (HB) virus secretory core protein HBe can efficiently deliver COOH-terminally located antigenic peptides for endogenous class I loading in the absence of TAP. Antigen presentation to specific cytotoxic T lymphocytes correlates with protein maturation at the COOH terminus, since modification of maturation and transport of HBe through the secretory pathway alters antigen presentation. Both maturation and a necessary processing step occur in the Golgi or post-Golgi compartment. Antigen presentation is independent of proteasome activity, but inhibitors of the trans-Golgi network resident protease furin inhibit both HBe maturation and antigen presentation. These results define a new antigen processing pathway located in the secretory route, with a central role for proteolytic maturation mediated by the subtilisin protease family member furin as an efficient source for antigen presentation.

Selective involvement of proteasomes and cysteine proteases in MHC class I antigen presentation

CTL recognize peptides derived from protein Ags bound to MHC-class I molecules. Proteasomes probably participate in the generation of these peptide epitopes. We investigated the role of proteasomes in the presentation of endogenously synthesized short viral proteins. To this end, we employed proteasome and cysteine protease inhibitors and two closely related recombinant vaccinia viruses that code for 17- and 19-amino acid-long products encompassing murine CMV 9pp89 epitope. Presentation of both minigene products required processing to shorter peptides and was independent of ubiquitination. Proteasomes were necessary for processing the 17-mer product, and cysteine proteases were not required. In contrast, the 19-mer product could be processed in parallel either by proteasomes or by cysteine proteases independently. These results highlight the diversity of alternative processing pathways even for short peptidic Ags, provide evidence for the involvement of cysteine proteases in MHC class I presentation, and show that cleavage by cysteine proteases is governed by sequences flanking the epitope.

Selective involvement of proteasomes and cysteine proteases in MHC class I antigen presentation

CTL recognize peptides derived from protein Ags bound to MHC-class I molecules. Proteasomes probably participate in the generation of these peptide epitopes. We investigated the role of proteasomes in the presentation of endogenously synthesized short viral proteins. To this end, we employed proteasome and cysteine protease inhibitors and two closely related recombinant vaccinia viruses that code for 17- and 19-amino acid-long products encompassing murine CMV 9pp89 epitope. Presentation of both minigene products required processing to shorter peptides and was independent of ubiquitination. Proteasomes were necessary for processing the 17-mer product, and cysteine proteases were not required. In contrast, the 19-mer product could be processed in parallel either by proteasomes or by cysteine proteases independently. These results highlight the diversity of alternative processing pathways even for short peptidic Ags, provide evidence for the involvement of cysteine proteases in MHC class I presentation, and show that cleavage by cysteine proteases is governed by sequences flanking the epitope.

Principles of cytomegalovirus antigen presentation in vitro and in vivo

Cytomegaloviruses are members of the ubiquitous family of herpesviruses. They escape immunological clearance and persist throughout life in the infected host. Yet, the stability of the balance of this virus-host interaction is dependent upon the state of the cellular immune response, and usually requires the function of specific CD8 T lymphocytes. In a mouse model, the major antigen that triggers protective CD8 T lymphocytes has been characterized as a nonameric amino acid motif of a nonstructural virus protein. Analysis of the naturally presented peptide has led to the conclusion that the sequence of an antigenic epitope is not the only parameter that decides upon its efficient presentation. Furthermore, the virus has developed regulatory functions that can prevent antigen presentation in productively infected cells. Contradictions between in vivo and in vitro findings are resolved in a hypothesis postulating an essential contribution of cytokines to the in vivo control of productive cytomegalovirus infection.

Efficient processing of an antigenic sequence for presentation by MHC class I molecules depends on its neighboring residues in the protein

Processing of endogenously synthesized proteins generates short peptides that are presented by MHC class I molecules to CD8 T lymphocytes. Here it is documented that not only the sequence of the presented peptide but also the residues by which it is flanked in the protein determine the efficiency of processing and presentation. This became evident when a viral sequence of proven antigenicity was inserted at different positions into an unrelated carrier protein. Not different peptides, but different amounts of the antigenic insert itself were retrieved by isolation of naturally processed peptides from cells expressing the different chimeric proteins. Low yield of antigenic peptide from an unfavorable integration site could be overcome by flanking the insert with oligo-alanine to space it from disruptive neighboring sequences. Notably, the degree of protection against lethal virus disease related directly to the amount of naturally processed antigenic peptide.

Protection against lethal cytomegalovirus infection by a recombinant vaccine containing a single nonameric T-cell epitope

The regulatory immediate-early (IE) protein pp89 of murine cytomegalovirus induces CD8+ T lymphocytes that protect against lethal murine cytomegalovirus infection. The IE1 epitope is the only epitope of pp89 that is recognized by BALB/c cytolytic T lymphocytes (CTL). Using synthetic peptides, the optimal and minimal antigenic sequences of the IE1 epitope have been defined. To evaluate the predictive value of data obtained with synthetic peptides, recombinant vaccines encoding this single T-cell epitope were constructed using as a vector the hepatitis B virus core antigen encoded in recombinant vaccinia virus. In infected cells expressing the chimeric proteins, only IE1 epitope sequences that were recognized as synthetic peptides at concentrations lower than 10(-6) M were presented to CTL. Vaccination of mice with the recombinant vaccinia virus that encoded a chimeric protein carrying the optimal 9-amino-acid IE1 epitope sequence elicited CD8+ T lymphocytes with antiviral activity and, furthermore, protected against lethal disease. The results thus show for the first time that recombinant vaccines containing a single foreign nonameric CTL epitope can induce T-lymphocyte-mediated protective immunity.

Presentation of CMV immediate-early antigen to cytolytic T lymphocytes is selectively prevented by viral genes expressed in the early phase

The regulation of antigen processing and presentation to MHC class I-restricted cytolytic T lymphocytes was studied in cells infected with murine cytomegalovirus. Recognition by cytolytic T lymphocytes of the phosphoprotein pp89, the immunodominant viral antigen expressed in the immediate-early phase of infection, was selectively prevented during the subsequent expression of viral early genes. The surface expression of MHC class I glycoproteins and their capacity to present externally added pp89-derived antigenic peptides were not affected. Because recognition of several other antigens occurred during the early phase, a general failure in processing and presentation was excluded. Since neither rate of synthesis, amount, stability, nor nuclear transport of pp89 was modified, the failure in recognition indicates a selective interference with pp89 antigen processing and presentation.

Dietary myo-inositol effect on sugar cataractogenesis

The lens myo-inositol (MI) content is known to be depleted during initial cataractogenesis in both streptozocin (STZ)-induced diabetic and 50% galactose-maintained rats. The objective of this study is to establish whether dietary MI supplementation protects lens transparency, MI content and individual fiber cell ultrastructure is both model systems of sugar cataract. In the diabetic study, after induction with STZ, rats were immediately placed on normal chow supplemented with 2% MI for 14 weeks while additional age-matched control and diabetic rats remained untreated. Within 14 weeks, untreated diabetic rat lenses were totally opaque with undetectable MI content; MI was undetectable by 1 month. These opaque lenses were devoid of fiber cells and exhibited only acellular, amorphous cortical regions between 0 and 500 microns from the capsule. In contrast, 14-week, MI-treated diabetic rat lenses exhibited only cortical vacuolation indicative of initial cataractogenesis; MI content was 0.41 +/- 0.26 mumol/g wet weight of lens. Scanning electron micrographs indicated a granulated, acellular region subadjacent to the capsule and confirmed the presence of cortical fiber cells, approximately 100 microns from the capsule. In 50% galactose-maintained rats, daily administration of MI for 1 month was unable to prevent total opacification or reverse initial cataractogenesis indicating that in rapidly progressing galactose cataracts, MI was unable to protect lens transparency, MI content and cortical fiber ultrastructure. The combined results suggest that MI may exert a protective effect on the slowly developing diabetic cataract. Of the 2 models, the time course and polyol content in STZ diabetic lenses more closely correlate to the human diabetic lens which has a low activity of aldose reductase; therefore, it is possible that MI may exert a protective effect in human diabetic cataract.

Molecular basis for cytolytic T-lymphocyte recognition of the murine cytomegalovirus immediate-early protein pp89

The murine cytomegalovirus protein pp89, which is encoded by gene ieI, is a nonstructural regulatory protein expressed in the immediate-early phase of the viral replication cycle and located mainly in the nucleus of infected cells. Protection of BALB/c (H-2d) mice against a lethal murine cytomegalovirus challenge infection is achieved by vaccination with a recombinant vaccinia virus, MCMV-ieI-VAC, expressing pp89 as the only murine cytomegalovirus gene product. The protection is entirely mediated by T lymphocytes of the CD8+ subset. In the present report, we analyzed the molecular basis of the recognition of pp89 by BALB/c CD8+ cytolytic T lymphocytes. A series of internal and terminal deletion mutants of gene ieI was constructed and cloned in vaccinia virus, and the antigenicity and immunogenicity of the fragments of pp89 expressed by the recombinants were studied. A region of only one-sixth of the protein, from amino acids 154 to 249 and encoded by the fourth exon of gene ieI, was sufficient for both the recognition in vitro of the protein by pp89-specific cytotoxic T lymphocytes and the induction in vivo of pp89-specific cytotoxic T lymphocytes. By using synthetic peptides, the sequence between residues 161 and 179, which is located within the defined domain, was identified as an epitope presented to BALB/C cytotoxic T lymphocytes by the class I major histocompatibility antigen Ld.

Proteinuria associated with hypertension and diabetes mellitus

Proteinuria, a complication of both diabetes mellitus and hypertension, was compared in 2 genetically induced models: insulin-dependent diabetic BB rat (BB), and Okamoto-Aoki spontaneously hypertensive Wistar rats (SHR). Both disease states were clearly distinguished from each other and their respective age-matched controls by analysis of 24-hour urine samples for glucose, urobilinogen, bilirubin and total protein. Then individual protein components between 15,000 and 120,000 daltons were separated by molecular weight and quantitated by laser densitometric analysis. The results indicated that insulin-dependent diabetic BB rats excreted urine having elevation of glucose (100-250 mg/dl), bilirubin (0.05 +/- 0.03 mg/dl) and urobilinogen (6.6 +/- 3.8 Ehrlich units/dl) in contrast to all age-matched SHR and normotensive Wistar-Kyoto (WKY) and nondiabetic controls, which excreted urine having normal urobilinogen and no detectable glucose or bilirubin. Both SHR and insulin-dependent BB rats exhibited proteinuria, urinary protein excretion being increased approximately 4-5 times that of their age-matched controls. BB rats excreted 18.80 +/- 2.62 mg protein/day attributed to an increase in albumin and an entire array of proteins between 30,000 and 120,000 daltons not present in controls which primarily excreted proteins below 20,000 daltons. In the SHR, proteinuria did not include an array of proteins; the increase in excreted protein (39.20 +/- 16 mg/day) was primarily attributed to albumin and another protein having a higher molecular weight. The SHR urinary proteins were similar to proteins excreted by streptozocin-induced, noninsulin-dependent diabetic rats treated with the aldose reductase inhibitor sorbinil. If hypertension is associated with diabetic nephropathy, our preclinical results suggest that coadministration of sorbinil with antihypertensive therapy may promote a positive synergistic effect further diminishing proteinuria.

Reversal of proteinuria by sorbinil, an aldose reductase inhibitor in spontaneously diabetic (BB) rats

Sorbinil, an aldose reductase inhibitor, was examined as a therapeutic agent to arrest and/or reverse proteinuria in 'type 1' insulin-dependent BB rats having spontaneous diabetes mellitus. Prior to sorbinil treatment, diabetic rats exhibited hyperglycemia and increased urinary excretion of urobilinogen, glucose and protein. To assess proteinuria, 24-hour urine samples were analyzed for both total protein and individual components between 30,000 and 100,000 daltons. Daily oral administration of sorbinil (20 mg/kg body weight) was initiated and the aforementioned parameters reevaluated after 1, 2 and 4 months. Results indicated that after 1 month of sorbinil treatment, urobilinogen was normalized in all diabetic BB rats (n = 12), whereas urinary protein excretion was either diminished (67%) or remained constant (16%), despite persistence of hyperglycemia and glycosuria. These therapeutic effects were sustained after 2 months of sorbinil treatment. After 4 months, protein excretion was normalized (6.56 +/- 3.34 mg/24 h), despite persistence of hyperglycemia and glycosuria (n = 12); in marked contrast, 6 untreated rats continued to exhibit proteinuria (17.76 +/- 2.59 mg/day). Sorbinil diminished albumin and a series of urinary proteins between 30,000 and 100,000 daltons, suggesting that sorbinil may represent a therapeutic approach to manage diabetic nephropathy as indicated by diminution of proteinuria.