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Background: Although cross-reactions between Epstein-Barr virus (EBV) and human systemic lupus erythematosus (SLE) autoantigens occur, a complete analysis of the potential EBV peptide cross-reactome has not been performed., Objectives: To analyze the whole EBV proteome searching for peptides common to SLE-related proteins and endowed with an immunological potential., Methods: Fifty-one SLE-related proteins were analyzed for hexapeptide sharing with EBV proteome using publicly available databases., Results: An extremely high number of hexapeptides are shared between 34 human SLE autoantigens and EBV proteins. The peptide sharing mostly occurs with complement components C4 and Interleukin-10 (IL-10)., Conclusions: This study thoroughly describes the EBV vs. SLE autoantigens peptide overlap and powerfully supports cross-reactivity as a major mechanism in EBV-associated SLE etiopathogenesis.

This study documents that mumps virus shares several peptide sequences with human proteins that, when altered, may be involved in oligospermia/azoospermia, sterility and testicular atrophy. Examples are sperm flagellar protein 2 and spermatogenesis and centriole-associated protein 1. The data invite to further investigate crossreactivity as a potential mechanism linking anti-mumps immune responses, alterations of spermatogenesis-associated antigens and male fertility disorders.

The primary amino acid sequence of West Nile virus (WNV) polyprotein, GenBank accession number M12294, was analyzed by computional biology. WNV is a mosquito-borne neurotropic flavivirus that has emerged globally as a significant cause of viral encephalitis in humans. Using pentapeptides as scanning units and the perfect peptide match program from PIR International Protein Sequence Database, we compared the WNV polyprotein and the human proteome. WNV polyprotein showed significant sequence similarities to a number of human proteins. Several of these proteins are involved in embryogenesis, neurite outgrowth, cortical neuron branching, formation of mature synapses, semaphorin interactions, and voltage dependent L-type calcium channel subunits. The biocomputional study suggest that common amino acid segments might represent a potential platform for further studies on the neurological pathophysiology of WNV infections., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Aim: To explore the molecular basis of the relationship between Bordetella pertussis infection and sudden death., Methods: B. pertussis proteins were analyzed for amino acid sequence identity to a set of 67 human proteins that, when altered, have been associated with sudden death., Results: More than 82,000 pentapeptides are shared between B. pertussis proteins and sudden death-associated antigens., Conclusion: Results suggest that a possible link between B. pertussis infection and sudden death might be represented by potential immunological cross-reactions occurring between B. pertussis proteins and human proteins associated to sudden death.

In the present study, we analyze the peptide commonality between poliovirus polyprotein and the human proteins. We report on the following findings: (1) the extent of polio peptide overlap on the human proteome is high, and involves the entire viral polyprotein; (2) viral peptide matching affects human proteins linked to fundamental cellular functions. The data may help to further our understanding of the relationships between poliovirus and the human host.

This paper defines potential peptide cross-reactivity between HIV-1 and the human host. Specifically, the amino acid primary sequence of HIV-1, isolate CDC-451, was analyzed for potential immunopathological relationships with the human proteome. The results revealed that: 1) HIV-1 shares 50 heptapeptides and three octapeptides with the human proteome; 2) 34 of the 50 shared heptapeptides are experimentally validated epitopes targeted by immune responses following HIV-1 infection; 3) the viral heptapeptide epitopes are present in human proteins that, when altered, are associated with disease characteristics of acquired immunodeficiency syndrome (AIDS) such as CD4+ cell loss, encephalopathy, schizophrenia, myopathy, cardiovascular disorders, hypertension, corneal diseases, diarrhea, lymphoma, and bladder cancer; 4) at the pentapeptide level, the viral-versus-human overlap is extensive (14,227 matches), with the viral pentapeptides disseminated throughout 10,312 human proteins. The findings are discussed in relationship to HIV-1 escape from immune surveillance, adjuvant-induced HIV-1 immunogenicity, autoimmune cross-reactions following human hyperimmune responses against HIV-1, and AIDS.

Cross-reactivity may affect diagnostic tests and cause harmful autoimmune reactions following immunotherapy. To predict potential cross-reactivity and search for safe immunotherapeutic approaches, we analyzed sequence identity between microbial antigens and the human proteome. Using diphtheria toxin (DT) as a model, we examined its patterns of identity with human proteins at the pentapeptide level. DT shares 503 pentapeptides with the human proteome, while only 31 pentapeptides are unique to the toxin. DT pentapeptide identity involves multiple/repeated matches in human proteins (a total of 4966 occurrences). Human proteins containing bacterial peptide matches include antigens linked to fundamental cellular functions, such as cell cycle control, proliferation, development and differentiation. The data presented in this article offer a rational basis for designing peptide-based vaccines that specifically target DT and thus eliminate the potential risk of cross-reactivity with human proteins. More generally, this study proposes a methodological approach for avoiding cross-reactivity in immune reactions.

In exploring the primary sequence of the human papilloma virus (HPV) 16 major capsid L1 protein for peptide sharing with human proteins, we find that 34 pentamers from the viral capsid protein are shared with human proteins that, when altered, have been linked to short QT syndrome, arrhythmogenic cardiac disorders, cardiovascular diseases and sudden death. In particular, nine out of the 34 viral pentamers are present in a human protein, titin, alterations of which have been linked to cardiac failure and sudden cardiac death. The present data may help evaluate the potential crossreactivity risks in anti-tumor vaccination protocols based on HPV16 L1 protein.

The proteomes catalogued in the UniRef100 database were collected into a single proteome set and examined for actual versus theoretical pentapeptide occurrences. We found a highly diversified degree of pentapeptide redundancy. Numerically, 953 pentamers are expressed only once in the protein world, whereas 103 pentamers occur more than 50,000 times. Moreover, it seems that 417 potentially possible pentapeptides are not present in the protein world. On the whole, tracing the redundancy profile of the protein world as a function of pentapeptide occurrences reveals a quasi-Gaussian curve, with tails representing scarcely and repeatedly occurring 5-mers. Analysis of physico-chemical-biological parameters shows that codon number is the main factor influencing and favoring specific pentapeptide frequencies in the universal proteome composition. That is, when compared to the set of never-expressed 5-mers, the pentapeptides frequently represented in the universal proteome are endowed with a higher number of multi-codonic amino acids. In contrast, the bulkiness degree and the hydrophobicity level play a smaller role. Unexpectedly, the heat of formation of pentapeptide appears to have the least influence.

The specific definition of the immunogenic peptide repertoire from tumor-associated-antigens (TAAs) is of crucial importance for designing effective immunotherapeutical treatments. Multiple mechanisms, at different levels and in complementary manners, contribute to the generation of immunogenic peptides. Using as an experimental model the prostate specific antigen (PSA) and a murine monoclonal antibody (MAb) raised against human PSA, the role of PSA peptide 1) similarity to the murine proteome, 2) affinity to H2-Ad/Ed molecules, and 3) proteasomal cleavage pattern were investigated. We report that the core of the interaction between the anti-PSA MAb ER-PR8 and the prostatic antigen is located in the pentapeptide motif PSA(27-31)GGWEC. The pentapeptide motif is characterized by having no sequence similarity to the murine proteome and a low number of potential proteolytic sites.

Background: A structured analysis of the literature indicates that a low level of sequence similarity to the host proteome modulates the B cell epitope pool in the humoral immune response toward protein antigens. From a clinical point of view, low-similarity peptides might have strong repercussions for the rational development of peptide-based treatments for cancer, autoimmunity and infectious diseases. The most attractive feature of the similarity concept is that it appears to guarantee the highest specificity and lowest cross-reactivity when designing effective, safe and theoretically infallible (immuno)therapeutic tools., Objective/methods: This review describes the research pathway from protein- to peptide-based therapies., Results/conclusions: Using the breast-cancer-associated BRCA2 protein as a model, the principle of sequence uniqueness is defined as the rationale for a pharmacological platform that might yield improved results in both patient survival and quality of life.

We propose low-similarity P-170 peptide-based antibodies to neutralize the multidrug resistance phenomenon and, consequently, improve the treatment regimens for cancer chemotherapy. As a first step in the experimental validation of this approach, we report on the similarity analysis of the P-170 primary amino acid structure versus the human proteome and describe peptide motifs uniquely owned by the human P-170 glycoprotein.

Thirty viral proteomes were examined for amino acid sequence similarity to the human proteome, and, in parallel, a control of 30 sets of human proteins was analyzed for internal human overlapping. We find that all of the analyzed 30 viral proteomes, independently of their structural or pathogenic characteristics, present a high number of pentapeptide overlaps to the human proteome. Among the examined viruses, human T-lymphotropic virus 1, Rubella virus, and hepatitis C virus present the highest number of viral overlaps to the human proteome. The widespread and ample distribution of viral amino acid sequences through the human proteome indicates that viral and human proteins are formed of common peptide backbone units and suggests a fluid compositional chimerism in phylogenetic entities canonically classified distantly as viruses and Homo sapiens. Importantly, the massive viral to human peptide overlapping calls into question the possibility of a direct causal association between virus-host sharing of amino acid sequences and incitement to autoimmune reactions through molecular recognition of common motifs.

We describe immune-proteome structures using libraries of protein fragments that define a structural immunological alphabet. We propose and validate such an alphabet as i) composed of letters of five consecutive amino acids, pentapeptide units being sufficient minimal antigenic determinants in a protein, and ii) characterized by low-similarity to human proteins, so representing structures unknown to the host and potentially able to evoke an immune response. In this context, we have thoroughly sifted through the entire human proteome searching for non-redundant protein motifs. Here, for the first time, a complete sequence redundancy dissection of the human proteome has been conducted. The non-redundant peptide islands in the human proteome have been quantified and catalogued according to the amino acid length. The library of uniquely occurring n-peptide sequences that was obtained is characterized by a logarithmic decrease of the number of non-redundant peptides as a function of the peptide length. This library represents a highly specific catalogue of molecular protein signatures, the possible use of which in cancer/autoimmunity research is discussed, with a major focus on non-redundant dodecamer sequences.

Alignment of protein sequences is fundamental in analyzing homology, evolutionary events and functional relationships. Searching for the epitopic peptide platform underlying hepatitis C virus (HCV) infection and autoimmune phenomena, we have used sequence-sequence peptide matching to compare the HCV polyprotein sequence to the human proteome. The following results were obtained: (1) pentamers from HCV polyprotein have a widespread and high level of similarity to a large number of human proteins (19,605 human proteins, that is 57.6% of the human proteome); (2) remarkable similarity between the two proteomes persists even using longer peptide motifs as probes for identity scanning; (3) only a limited number of HCV pentameric fragments have no similarity to the human host, so representing molecular sequence signatures of the virus. We conclude that the widespread sharing of numerous perfect exact matches between HCV and human proteomes might explain HCV persistence in humans.

Experimental analyses and literature survey reveal low-redundancy to the host proteins as a common denominator of immunogenic sequences mapped along tumor-, autoimmune-, and infectious disease-associated-proteins. The hypothesis that immunogenicity of peptide sequences is linked to proteomic redundancy is discussed.