Growth differentiation factor-15 is a biomarker for all-cause mortality but less evident for cardiovascular outcomes: A prospective study

BACKGROUND

Previous studies have proposed growth differentiation factor-15 (GDF-15) as a predictor of adverse cardiovascular outcomes and mortality. The present study aimed to determine if such associations remain after accounting for death as a competing risk, and if GDF-15 provides superior prediction performance than other biomarkers.

METHODS

Plasma GDF-15 levels and cardiovascular risk factors were measured in individuals without cardiovascular diseases (n = 4,143, aged 57.4 ± 5.96 years, 38.6 % men) from Malmö Diet and Cancer-Cardiovascular Cohort and were followed up for more than 20 years. Incidence of coronary events, ischemic stroke, cardiovascular mortality, and all-cause mortality was studied in relation to GDF-15 using Cox proportional hazards regression, with adjustment for potential confounders. Confounding from death as competing risk was carefully checked using the Fine and Gray subdistribution hazard model. Predictive capabilities were further evaluated using C-statistics, continuous net reclassification improvement, and integrated discrimination improvement.

RESULTS

During follow-up, 424 coronary events, 327 ischemic stroke, 368 cardiovascular deaths, and 1,308 all-cause deaths occurred. After controlling for death from other causes as competing events, only all-cause mortality remained significantly related to GDF-15. The addition of GDF-15 significantly improved prediction for all-cause mortality in addition to the traditional risk factors, high-sensitive C-reactive protein and N-terminal prohormone of brain natriuretic peptide. Only N-terminal prohormone of brain natriuretic peptide improved prediction for CVD mortality.

CONCLUSIONS

GDF-15 is a robust biomarker for all-cause mortality but less reliable for coronary event, ischemic stroke or cardiovascular mortality. Competing risk from death is an important consideration when interpreting the results.

The Association between Plasma ERVWE1 Concentrations and Affective Symptoms during Pregnancy: Is This a Friendly Alien?

Human endogenous retroviruses (HERVs) comprise 8% of the human genome, and HERV DNA was reported to be essential in human embryonic development. Specifically, HERV-W encodes a protein, syncytin-1, alternatively known as ERVWE1 (Human Endogenous Retrovirus W EnvC7-1 Envelope Protein), participating in human placental morphogenesis and having a role in immune system regulation. Syncytin-1 activity is increased in neuropsychiatric disorders, autoimmune diseases, and cancer. In our study, forty-four women in the third trimester of pregnancy were tested for ERVWE1 plasma levels. In concomitance with blood samples the following rating scales were administered to women: the Edinburgh Postnatal Depression Scale (EPDS), State Anxiety Inventory (STAI-S), Trait Anxiety Inventory (STAI-T), and Prenatal Attachment Inventory (PAI). We found that higher ERVWE1 protein plasma levels were significantly associated with higher PAI scores (p = 0.02), an earlier gestational age at the time of blood collection (p = 0.01), a longer duration of symptoms (p = 0.03), and fewer lifetime attempted suicides (p = 0.02). Our results seem to support the role of ERVWE1 in maintaining clinical psychiatric symptoms as a result of potential prolonged inflammation. At the same time, this protein may have a protective role in pregnant women by a reduction of suicidal behavior and a better mother-fetus relationship.

A new therapeutic approach for type 1 diabetes: Rationale for GNbAC1, an anti-HERV-W-Env monoclonal antibody

We describe a newly identified therapeutic target for type 1 diabetes (T1D): an envelope protein of endogenous retroviral origin, human endogenous retrovirus W envelope (HERV-W-Env). HERV-W-Env was found to be detected in the blood of ~60% of patients with T1D and is expressed in acinar pancreatic cells of 75% of patients with T1D at post mortem examination. Preclinical experiments showed that this protein displays direct cytotoxicity on human β-islet cells. In vivo HERV-W-Env impairs the insulin and glucose metabolism in transgenic mice expressing HERV-W-Env. GNbAC1, an IgG4 monoclonal antibody, has been developed to specifically target HERV-W-Env and to neutralize the effect of HERV-W-Env in vitro and in vivo. GNbAC1 is currently in clinical development for multiple sclerosis and > 300 subjects have been administered with GNbAC1 so far. GNbAC1 is now being tested in T1D in the RAINBOW-T1D study, which is a randomized placebo-controlled study with the objective of showing the safety and pharmacodynamic response of GNbAC1 in patients who have had T1D with a maximum of 4 years' duration. GNbAC1 is being tested vs placebo at the dose of 6 mg/kg in 60 patients during six repeated administrations for 6 months; a 6-month open-label extension will follow. The primary endpoint is to assess safety, and secondary endpoints are the pharmacodynamic responses to GNbAC1. GNbAC1 targeting HERV-W-Env is currently in clinical development in T1D, with the first safety and pharmacodynamic study. If the study results are positive, this may open the door to the development of an innovative non-immunomodulatory disease-modifying treatment for T1D.

Expression of human endogenous retrovirus env genes in the blood of breast cancer patients

Human endogenous retroviruses (HERV) env proteins have been recently reported to be significantly up-regulated in certain cancers. Specifically, mRNA and protein levels of HERV-K (HML-2) are up-regulated in the blood plasma or serum of breast cancer patients. Here, we collected blood samples of 49 breast cancer patients and analyzed mRNA expressions of various HERVs env genes including HERV-R, HERV-H, HERV-K, and HERV-P by real-time PCR. The expression of env genes were significantly increased in the blood of primary breast cancer patients but were decreased in patients undergoing chemotherapy to a similar level with benign patients. When we compared the group currently undergoing chemotherapy and those patients undergoing chemotherapy simultaneously with radiotherapy, HERVs env genes were reduced more in the chemotherapy only group, suggesting that chemotherapy is more effective in reducing HERV env gene expression than is radiotherapy. Among chemotherapy groups, HERV env gene expression was the lowest in the taxotere- or taxol-treated group, suggesting that taxotere and taxol can reduce HERVs env expression. These data suggest the potential to use HERVs env genes as a diagnosis marker for primary breast cancer, and further studies are needed to identify the mechanism and physiological significance of the reduction of HERV env gene expression during chemotherapy.

R5 to X4 Switch of the Predominant HIV-1 Population in Cellular Reservoirs During Effective Highly Active Antiretroviral Therapy

HIV-1 coreceptor usage plays a critical role for virus tropism and pathogenesis. A switch from CCR5 to CXCR4-using viruses can occur in the natural course of infection and correlates with subsequent disease progression. To investigate whether HIV-1 genetic evolution might lead to changes in virus coreceptor usage during highly active antiretroviral therapy (HAART), a longitudinal genotypic analysis of the virus found in cellular reservoirs was conducted in 32 patients with undetectable viral loads on HAART for 5 years. The genotype of the 3rd variable region of the env gene predicting coreceptor usage was retrospectively determined in the plasma or in peripheral blood mononuclear cells (PBMC) at baseline and then in PBMCs at months 30 and 60 of HAART. There was a switch from R5 to X4 variants in 11 of the 23 patients who harbored a majority virus population of R5 variants at baseline. X4 variants remained predominant in the 9 patients who harbored mainly X4 variants at baseline. The patients harboring predominantly X4 variants during HAART, either from baseline or after an R5 to X4 switch, tended to have lower CD4+ T-cell counts on HAART than did patients harboring continuously a majority population of R5 variants. These results suggest that potent antiretroviral therapy produces the conditions necessary for the gradual emergence of X4 variants in cellular reservoirs.

Replication of simian immunodeficiency virus (SIV) in ex vivo lymph nodes as a means to assess susceptibility of macaques in vivo

Six macaques, apparently uninfected, following low-dose exposure to the pathogenic SIV(mac251) and SIV(SME660) by the mucosal route, were used in a pilot study to investigate whether infectability of ex vivo lymph nodes could predict resistance and/or susceptibility to SIV infection in vivo. Of six macaques exposed to the less-pathogenic virus SIV(MNE), four resisted viral infection. Analysis of the susceptibility of the PBMC of these four animals before SIV(MNE) challenge indicated that all of them were resistant to infection by the SIV(BK28) isolate and, in three of them, this resistance was dependent on CD8+ T cells. Blocks of lymph nodes of these four macaques were resistant to SIV(MNE) infection ex vivo following SIV(MNE) viral challenge exposure. However, the same blocks from the same animals were permissive to the more virulent SIV(251(32H)). Accordingly, three of these macaques were readily infected following challenge exposure with SIV(251(32H)). Lymphoproliferative responses in blood or lymph nodes, local C-C chemokine production in the lymph-node explants, and cytotoxic T-cell activity measured throughout the study did not correlate with ex vivo resistance or susceptibility to in vivo infection. In conclusion, PBMC and lymph-node resistance or susceptibility to infection ex vivo appeared to correlate with in vivo infectivity and, thus, these approaches should be further tested for their predictive value for in vivo infection.

Protective role of beta-chemokines associated with HIV-specific Th responses against perinatal HIV transmission

To examine the protective role of cellular immunity in the vertical transmission of HIV, we analyzed HIV-specific IL-2 and CTL responses, as well as beta-chemokine expression in HIV-infected and uninfected infants of HIV+ mothers. Our results showed that HIV envelope (env) peptide-specific IL-2 responses associated with beta-chemokine production were detectable at birth in the majority of uninfected infants of HIV+ mothers. The responses falling to background before the infants were 1 yr old were rarely associated with HIV-specific CTL activity. Conversely, HIV-specific Th and CTL cellular responses were absent at birth in HIV-infected infants. Infants with AIDS-related symptoms exhibited undetectable or very low levels of HIV-specific cellular immunity during the first year of life, whereas those with a slowly progressive disease showed evidence of such immunity between their second and ninth month. The latter group of infected infants tested negative for plasma HIV RNA levels shortly after birth, suggesting lack of intrauterine exposure to HIV. The presence of HIV-specific Th responses at birth in uninfected newborns of HIV+ mothers, but absence of such activities in HIV-infected infants without evidence of intrauterine HIV infection, suggests that in utero development of HIV-specific Th responses associated with beta-chemokines could mediate nonlytic inhibition of infection during vertical transmission of HIV.

Performance characteristics of recombinant enzyme immunoassay to detect antibodies to human immunodeficiency virus type 1 (HIV-1) and HIV-2 and to measure early antibody responses in seroconverting patients

We investigated the performance of a double-antigen sandwich recombinant enzyme immunoassay (EIA; Abbott Laboratories, North Chicago, Ill.) and compared it with that of a synthetic-peptide-based EIA (Biochem Immunosystems, Montreal, Quebec, Canada) for the detection of human immunodeficiency type 1 (HIV-1) and HIV-2 antibodies in 2,321 clinical serum samples. The results of both EIA methods and Western blot (immunoblot) were in agreement for 1,046 HIV-1 and 10 HIV-2 specimens from a panel of known positives. From a prospective panel of 1,085 specimens, 38 proved to be positive by both EIAs and Western blot, 3 were positive by the recombinant EIA only, and 9 were positive by the peptide EIA only, for calculated specificities of 99.71 and 99.04%, respectively. Of 180 specimens from a seroconversion panel collected from 77 patients, the results for 170 were in agreement by all antibody testing methods and 10 were found to be repeat reactive for HIV antibodies by the recombinant EIA only. All 10 were initial specimens of seroconverting patients; 7 were also reactive for HIV p24 antigen. An examination of four of these sera by radioimmunoprecipitation assay showed gp120 and gp160 bands in each. Analysis of the anti-Env antibody class in three of these samples showed that one consisted of immunoglobulin M (IgM) only and two contained both IgG and IgM antibodies. Although both EIA procedures were sensitive and specific in the detection of antibodies to HIV-1 and HIV-2 and both were capable of detecting early antibodies, the recombinant assay was more sensitive for antibody detection during early seroconversion.

Lack of induction of antibodies specific for conserved, discontinuous epitopes of HIV-1 envelope glycoprotein by candidate AIDS vaccines

We examined the humoral immune response in both HIV-1 infected and uninfected volunteers immunized with candidate HIV-1 recombinant envelope subunit vaccines (Genentech gp120IIIB, MicroGeneSys gp160IIIB, or ImmunoAG gp160IIIB). Immunization of both HIV-1 infected and uninfected volunteers with these immunogens resulted in the induction of Abs preferentially reactive with epitopes accessible on a denatured form of gp120. While sera from HIV-1 uninfected gp120/gp160IIIB vaccinees bound gp120/gp41, which was expressed on the surface of H9 cells infected with HIV-1IIIB, minimal binding to HIV-1MN or HIV-1RF infected cells was obtained. Induction of qualitatively similar immune responses by these immunogens would not have been predicted based on their different tertiary structures. These data indicate a restriction of the immune response to linear, conserved epitopes poorly accessible on both monomeric gp120 and cell-surface expressed oligomeric gp120/gp41 and a lack of Abs specific for conformational epitopes conserved across divergent HIV-1 strains. Poor recognition of HIV-1 envelope tertiary and quaternary structure may explain the restricted neutralization profiles of vaccinee sera against laboratory-adapted strains of HIV-1 and their inability to neutralize primary HIV-1 isolates. Alternate immunogens or reformulations with the capacity to elicit Abs that preferentially bind to natively folded gp120 should be investigated and correlated with their ability to neutralize more diverse laboratory-adapted and primary HIV-1 isolates.

Reactivity of five anti-HIV-1 subtype O specimens with six different anti-HIV screening ELISAs and three immunoblots

Five anti-subtype O specimens were tested by anti-HIV-1/2 screening and confirmatory assays. They can be divided into three specimens, reactive with all ELISAs, independent of the nature of the antigen (recombinant proteins or peptides) and test configuration (indirect ELISA or double antigen/sandwich ELISA). One specimen was not detected by one peptide based ELISA. One specimen was only recognized by two ELISAs and should be considered as a marker sample for the weakness of currently used ELISAs with anti-subtype O. Three different immunoblot assays available commercially detected two of the specimens with a major binding of gp160 and other viral bands, especially the integrase and reverse transcriptase. Another two specimens lacked reactivity with glycoproteins almost completely, but showed some staining with the enzymes of HIV, and would most probably be interpreted as indeterminate. The fifth specimen, which was also missed by most of the ELISAs, had very faint staining of the gp160 and a very weak staining of p24, and would most probably be interpreted as negative. Adaption of currently available tests to anti-subtype O is needed for the future reliability of anti-HIV diagnostic reagents.

Identification of a recombinant HTLV-II envelope protein for serological detection of HTLV-II carriers

To understand the pathogenic potential and the true extent of human T-cell leukemia virus type II (HTLV-II) infection, it is important to develop a specific HTLV-II antigen-based serological test. Plasmid pIIB was constructed and induced in Escherichia coli to express a recombinant protein (RP) containing 140 amino acids (amino acid residues 96 to 235) from the middle region of the HTLV-II exterior envelope glycoprotein gp52. Serum samples from polymerase chain reaction-confirmed HTLV-II-infected people, HTLV-I carriers, and adult T-cell leukemia (ATL) patients were tested for antibody reactivity to RP-IIB by Western blot assay. The results showed all 27 HTLV-II carriers, 10 of 20 HTLV-I carriers, and 4 of 17 (23.5%) ATL patients had antibody reactivities to RP-IIB. The difference in rates of seropositivity to RP-IIB between HTLV-II carriers (100%) and HTLV-I-infected people (carriers plus ATL patients) (37.8%) is statistically significant (Fisher's exact test, p = 4.30E-08).