Antigenicity of chimeric and cyclic synthetic peptides based on nonstructural proteins of GBV-C/HGV

Advances in the diagnosis of autoimmune diseases based on citrullinated peptides/proteins

Introduction: Autoimmune diseases are still one of the hard obstacles associated with humanity. There are many exogenous and endogenous etiological factors behind autoimmune diseases, which may be combined or dispersed to stimulate the autoimmune responses. Protein citrullination represents one of these factors. Harnessing specific citrullinated proteins/peptides could early predict and/or diagnose some of the autoimmune diseases. Many generations of diagnostic tools based on citrullinated peptides with comparable specificity/sensitivity are available worldwide.Areas covered: In this review, we discuss the deimination reaction behind the citrullination of most known autoantigens targeted, different generations of diagnostic tools based on citrullinated probes with specificity/sensitivity of each as well as newly developed assays. Furthermore, the most advanced molecular analytical tools to detect the citrullinated residues in the biological fluid and their performance are also evaluated, providing new avenues to early detect autoimmune diseases with high accuracy.Expert opinion: With the current specificity/sensitivity tools available for autoimmune disease detection, emphasis must be placed on developing more advance and effective, early, rapid, and simple diagnostic devices for autoimmune disease monitoring (similar to a portable device for sugar test at home). The molecular analytical devices with dual and/or multiplexe functions should be more simplified and invested in clinical laboratories.

Development of a multiplex assay based on chimeric citrullinated peptides as proof of concept for diagnosis of rheumatoid arthritis

Anti-citrullinated peptide/protein antibodies (ACPAs) are the most specific serological biomarkers for rheumatoid arthritis (RA). They have both diagnostic and prognostic value, and are related to more aggressive joint disease in RA. However, a single biomarker cannot differentiate RA subtypes. So, simultaneous analysis of target citrullinated peptides, using a multiplex array based on chimeric peptides composed of several domains of human proteins, could be useful. In this work, eight chimeric peptides and the corresponding native arginine-containing control peptides were obtained by solid-phase peptide synthesis. The study included RA and psoriatic arthritis (PsA) patients attending the Rheumatology Unit of the Hospital Clinic in Barcelona, as well as healthy blood donors (BD) at the same hospital. Our main aim was to explore the diagnostic value of the novel multiplex array compared to a commercial ELISA-based ACPA assay in a serum-saving way. Using the combination of the eight chimeric peptide antigens in the multiplex array, 61.4% of the RA cohort were positive for 3 or more peptides; while, the healthy BD and PsA cohorts did not show any reactivity with the tested peptides. These results indicate that we have developed a highly specific multiplex assay based of chimeric citrullinated peptides derived from filaggrin, fibrin, vimentin and human enolase proteins for the detection of ACPAs in a serum-saving way.

Adenoviral vectors elicit humoral immunity against variable loop 2 of clade C HIV-1 gp120 via "Antigen Capsid-Incorporation" strategy

Adenoviral (Ad) vectors in combination with the "Antigen Capsid-Incorporation" strategy have been applied in developing HIV-1 vaccines, due to the vectors׳ abilities in incorporating and inducing immunity of capsid-incorporated antigens. Variable loop 2 (V2)-specific antibodies were suggested in the RV144 trial to correlate with reduced HIV-1 acquisition, which highlights the importance of developing novel HIV-1 vaccines by targeting the V2 loop. Therefore, the V2 loop of HIV-1 has been incorporated into the Ad capsid protein. We generated adenovirus serotype 5 (Ad5) vectors displaying variable loop 2 (V2) of HIV-1 gp120, with the "Antigen Capsid-Incorporation" strategy. To assess the incorporation capabilities on hexon hypervariable region1 (HVR1) and protein IX (pIX), 20aa or full length (43aa) of V2 and V1V2 (67aa) were incorporated, respectively. Immunizations with the recombinant vectors significantly generated antibodies against both linear and discontinuous V2 epitopes. The immunizations generated durable humoral immunity against V2. This study will lead to more stringent development of various serotypes of adenovirus-vectored V2 vaccine candidates, based on breakthroughs regarding the immunogenicity of V2.

The use of chimeric vimentin citrullinated peptides for the diagnosis of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes inflammation and, in many cases, destruction of the joints. To prevent progressive and irreversible structural damage, early diagnosis of RA is of paramount importance. The present study addresses the search of new RA citrullinated antigens that could supplement or complement diagnostic/prognostic existing tests. With this aim, the epitope anticitrullinated vimentin antibody response was mapped using synthetic peptides. To improve the sensitivity/specificity balance, a vimentin peptide that was selected, and its cyclic analogue, were combined with fibrin- and filaggrin-related peptides to render chimeric peptides. Our findings highlight the putative application of these chimeric peptides for the design of RA diagnosis systems and imply that more than one serological test is required to classify RA patients based on the presence or absence of ACPAs. Each of the target molecules reported here (fibrin, vimentin, filaggrin) has a specific utility in the identification of a particular subset of RA patients.

Antibodies against β-fibrin synthetic peptides: a study of their association with the immunogenetic background and disease course of rheumatoid arthritis patients

Preliminary studies have shown the potential application for the diagnosis of Rheumatoid Arthritis (RA) patients with a severe disease course of an epitopic domain of β-fibrin. The aim of the present work was the analysis of the presence of antibodies against several β-fibrin synthetic peptides in relation to the immunogenetic background and disease course in a clinically well-defined RA patient cohort. Our results indicated that positive patients against anti-β-fibrin synthetic peptides have a higher percentage of HLA-DRB1 shared epitope (SE) than negative patients. We also observed that the presence of SE alleles was significantly associated with a higher level of anti-[Cit(376)]βfib(365-383) antibodies. When analyzing the effect of different SE alleles, we found a significant positive association between carriers of QRRAA allele and [Cit(376)]βfib(365-383) (Odds ratio 3.77; CI95%: 1.41-10.08). These results suggest that the anti-β-fibrin status is associated with the immunogenetic background of RA patients.

Assessment of synthetic chimeric multiple antigenic peptides for diagnosis of GB virus C infection

The use of synthetic peptides of both structural and nonstructural proteins of GB virus C (GBV-C) has been studied for the development of new systems to diagnose infection caused by this virus. In an attempt to increase the antigenicity of linear peptide sequences, chimeric multiple antigenic peptides (MAPs) containing epitopes from E2, NS4, and NS5 GBV-C proteins have been synthesized. The synthetic constructs were evaluated by ELISA to establish whether the epitopes in chimeric branched peptides are more efficiently recognized by the specific antibodies compared to the monomeric linear sequences. Moreover, we have investigated the application of a commercial biosensor instrument for the detection of antibodies against the GBV-C in human serum samples. The results of the immunoassays reported in this work highlight the usefulness of synthetic tetrameric branched peptides containing sequences from envelope and nonstructural GBV-C proteins for the diagnosis of GBV-C infection. The potential clinical value of the MAP(4)(E2-NS5a) for the serodiagnosis of GBV-C infection was demonstrated, thus providing the basis for performing prevalence studies of the infection among the hemodialyzed and hepatitis C virus (HCV)-infected population.

Antibodies to citrullinated human fibrinogen synthetic peptides in diagnosing rheumatoid arthritis

Since aggressive therapy given early in the rheumatoid arthritis (RA) disease course has the greatest therapeutic potential, early diagnostic tests with both high specificity and sensitivity are desirable. Rheumatoid sera were found to contain antibodies against citrullinated peptides, which are considered to be highly specific markers of RA. In the present work several analogues of the alpha- and beta-chains of fibrin peptides containing different degrees of citrullination have been synthesized and analyzed by ELISA using 111 sera from RA patients. In addition, we have also investigated the synergistic effects of different presentation formats of the synthetic constructs. We have designed chimeric and cyclic peptides that bear different peptide sequences within the same molecule. Our results indicate that the synthesis of peptides bearing fibrinogen and filaggrin domains could be a robust method for the design of useful diagnostic strategies in RA.