Pathways of antigen processing

EBV-microRNAs as Potential Biomarkers in EBV-related Fever: A Narrative Review

At present, timely and accurate diagnosis and effective treatment of Epstein- Barr Virus (EBV) infection-associated fever remain a difficult challenge. EBV encodes 44 mature microRNAs (miRNAs) that inhibit viral lysis, adjust inflammatory response, regulate cellular apoptosis, promote tumor genesis and metastasis, and regulate tumor cell metabolism. Herein, we have collected the specific expression data of EBV-miRNAs in EBV-related fevers, including infectious mononucleosis (IM), EBVassociated hemophagocytic lymphohistiocytosis (EBV-HLH), chronic active EBV infection (CAEBV), and EBV-related tumors, and proposed the potential value of EBVmiRNAs as biomarkers to assist in the identification, diagnosis, and prognosis of EBVrelated fever, as well as therapeutic targets for drug development.

Nanotechnology-facilitated vaccine development during the coronavirus disease 2019 (COVID-19) pandemic

Coronavirus disease 2019 (COVID-19) continually poses a significant threat to the human race, and prophylactic vaccination is the most potent approach to end this pandemic. Nanotechnology is widely adopted during COVID-19 vaccine development, and the engineering of nanostructured materials such as nanoparticles has opened new possibilities in innovative vaccine development by improving the design and accelerating the development process. This review aims to comprehensively understand the current situation and prospects of nanotechnology-enabled vaccine development against the COVID-19 pandemic, with an emphasis on the interplay between nanotechnology and the host immune system.

A Review About Pembrolizumab in First-Line Treatment of Advanced NSCLC: Focus on KEYNOTE Studies

 Lung cancer is currently the malignant tumor with the highest incidence and mortality in the world, while non-small cell lung cancer (NSCLC) is the most common pathological type of lung caner. In the past few decades, the only treatment options available for advanced NSCLC patients have been targeted therapy or chemotherapy, but these therapies are inevitably tolerated by tumors.  The discovery of immune checkpints that mediate the immune escape of tumor cells have been promoting a series of immune checkpoint inhibitors to be used in cancer treatment and achieved great results. Among them, pembrolizumab is currently the only PD-1 inhibitor approved for first-line treatment of NSCLC, whether it is monotherapy or combination therapy, for creditable performance in KEYNOTE studies. In this review, we systematically integrate the latest series of clinical trial results, pharmacological mechanisms, adverse events (AEs) and predictive biomarkers in the first-line treatment of NSCLC. We hope pembrolizumab could become a better choice for more clinicians and benefit more patients with advanced NSCLC.

Epstein-Barr virus-encoded microRNAs as regulators in host immune responses

Epstein-Barr virus (EBV) is an oncogenic virus that infects over 90% of the world's adult population. EBV can establish life-long latent infection in host due to the balance between EBV and host immune system. EBV latency is associated with various malignancies such as nasopharyngeal carcinoma, gastric carcinoma and Burkitt's lymphoma. EBV is the first human virus that has the capability to encode microRNAs (miRNAs). Remarkably, EBV-encoded miRNAs are abundantly expressed in latently-infected cells and serve important function in viral infection and pathogenesis. Increasing evidence indicates that EBV miRNAs target the host mRNAs involved in cell proliferation, apoptosis and transformation. EBV miRNAs also inhibit the expression of viral antigens, thereby enabling infected cells to escape immune recognition. Intriguingly, EBV miRNAs directly suppress host antiviral immunity by interfering with antigen presentation and immune cell activation. This review will update the current knowledge about EBV miRNAs implicated in host immune responses. An in-depth understanding of the functions of EBV miRNAs in host antiviral immunity will shed light on the EBV-host interactions and provide potential therapeutic targets for the treatment of EBV-associated malignancies.

In silico predicted epitopes from the COOH-terminal extension of cysteine proteinase B inducing distinct immune responses during Leishmania (Leishmania) amazonensis experimental murine infection

BACKGROUND

Leishmania parasites have been reported to interfere and even subvert their host immune responses to enhance their chances of survival and proliferation. Experimental Leishmania infection in mice has been widely used in the identification of specific parasite virulence factors involved in the interaction with the host immune system. Cysteine-proteinase B (CPB) is an important virulence factor in parasites from the Leishmania (Leishmania) mexicana complex: it inhibits lymphocytes Th1 and/or promotes Th2 responses either through proteolytic activity or through epitopes derived from its COOH-terminal extension. In the present study we analyzed the effects of Leishmania (Leishmania) amazonensis CPB COOH-terminal extension-derived peptides on cell cultures from murine strains with distinct levels of susceptibility to infection: BALB/c, highly susceptible, and CBA, mildly resistant.

RESULTS

Predicted epitopes, obtained by in silico mapping, displayed the ability to induce cell proliferation and expression of cytokines related to Th1 and Th2 responses. Furthermore, we applied in silico simulations to investigate how the MHC/epitopes interactions could be related to the immunomodulatory effects on cytokines, finding evidence that specific interaction patterns can be related to in vitro activities.

CONCLUSIONS

Based on our results, we consider that some peptides from the CPB COOH-terminal extension may influence host immune responses in the murine infection, thus helping Leishmania survival.

The Delta fbpA mutant derived from Mycobacterium tuberculosis H37Rv has an enhanced susceptibility to intracellular antimicrobial oxidative mechanisms, undergoes limited phagosome maturation and activates macrophages and dendritic cells

Mycobacterium tuberculosis H37Rv (Mtb) excludes phagocyte oxidase (phox) and inducible nitric oxide synthase (iNOS) while preventing lysosomal fusion in macrophages (MPhis). The antigen 85A deficient (Delta fbpA) mutant of Mtb was vaccinogenic in mice and the mechanisms of attenuation were compared with MPhis infected with H37Rv and BCG. Delta fbpA contained reduced amounts of trehalose 6, 6, dimycolate and induced minimal levels of SOCS-1 in MPhis. Blockade of oxidants enhanced the growth of Delta fbpA in MPhis that correlated with increased colocalization with phox and iNOS. Green fluorescent protein-expressing strains within MPhis or purified phagosomes were analysed for endosomal traffick with immunofluorescence and Western blot. Delta fbpA phagosomes were enriched for rab5, rab11, LAMP-1 and Hck suggesting enhanced fusion with early, recycling and late endosomes in MPhis compared with BCG or H37Rv. Delta fbpA phagosomes were thus more mature than H37Rv or BCG although, they failed to acquire rab7 and CD63 preventing lysosomal fusion. Finally, Delta fbpA infected MPhis and dendritic cells (DCs) showed an enhanced MHC-II and CD1d expression and primed immune T cells to release more IFN-gamma compared with those infected with BCG and H37Rv. Delta fbpA was thus more immunogenic in MPhis and DCs because of an enhanced susceptibility to oxidants and increased maturation.

Fusogenic liposome can be used as an effective vaccine carrier for peptide vaccination to induce cytotoxic T lymphocyte (CTL) response

We reported previously that fusogenic liposome (FL) introduced antigen protein encapsulated in the liposome directly into the cytoplasm of the antigen presenting cells, and that it induced immune responses. In the present study, we encapsulated TAX38-46, an HTLV-I derived protein and an antigen peptide model, into FL. The ability to induce effective cytotoxic T lymphocytes (CTL) responses in immunized mice was evaluated. Results showed FL could induce CTL response effectively and suggested that FL is a potential peptide vaccine carrier.

The use of bovine MHC class I allele-specific peptide motifs and proteolytic cleavage specificities for the prediction of potential cytotoxic T lymphocyte epitopes of bovine viral diarrhea virus

Cell mediated immunity (CMI) is crucial for the defense against viruses. Cytotoxic T lymphocytes (CTLs) play a major role in CMI. They recognize endogenous antigenic peptides presented by antigen presenting cells in association with the major histocompatibility complex (MHC) class I molecules. The elucidation of the sequence of CTL epitopes of viruses should help in designing better vaccines. In this study, we have identified candidate epitopes restricted by five bovine MHC class I molecules that are potentially available for presentation to CTLs. The candidate peptide epitopes were identified by using the computer programs available as a part of the Genetics Computer Group package and applying the information on allele-specific peptide motifs and intracellular enzymatic cleavage patterns to the bovine viral diarrhea virus polyprotein. Several candidate peptides were found for each of the bovine lymphocyte antigens (BoLA)-A11, -A20, -HD1, and -HD6 whereas no peptide was found for BoLA-HD7. Based on this finding, the probable contribution of genomic segments of BVDV to the CTL response and strategies for recombinant vaccines are discussed.

Prediction of potential cytotoxic T lymphocyte epitopes of bovine herpesvirus 1 based on allele-specific peptide motifs and proteolytic cleavage specificities

Major histocompatibility complex (MHC) class I molecules present endogenous peptides to cytotoxic T lymphocytes (CTLs). Elucidation of CTL epitopes of intracellular pathogens helps in designing better vaccines to control economically important human and animal diseases. In this study, candidate epitopes that are potentially available for presentation to the CTLs via five bovine MHC class I molecules have been identified. This was accomplished by using the computer programs "Find-patterns" and "Peptidestructure" of GCG package and applying the information on cleavage patterns of cytosolic and endoplasmic reticulum proteases and peptidases as well as MHC class I allele-specific peptide motifs on 23 bovine herpesvirus-1 (BHV-1) proteins available on protein sequence database. Several candidate peptides were found for each of the bovine lymphocyte antigens (BoLA)-A11, -A20, -HD1, and -HD6 whereas no peptide was found for BoLA-HD7. Majority of the candidate peptides were from the viral glycoproteins. The contribution of such studies towards the identification of CTL epitopes of BHV-1 and other intracellular pathogens is discussed.

Immunogenicity of the Escherichia coli fimbrial antigen K99 when expressed by Salmonella enteritidis 11RX

Salmonella strains expressing the Escherichia coli fimbrial protein K99 were used to immunize adult mice, and the resulting anti-K99 T-cell responses were examined. Immunized animals displayed delayed-type hypersensitivity responses when challenged with K99 in the footpad. Lymphoid cells from immunized animals proliferated and released cytokines when cultured in vitro with K99 or peptides generated by cyanogen bromide treatment; the T cells which responded had the CD4+ phenotype.

Rat intestinal M cells contain acidic endosomal-lysosomal compartments and express class II major histocompatibility complex determinants

BACKGROUND

It is generally believed that M cells do not modify the antigens they transport from the intestinal lumen to underlying immunocompetent cells because it has been reported that M cells contain few elements of the lysosomal system.

METHODS

We used specific cytochemical and immunocytochemical probes to examine whether M cells in jejunal Peyer's patches of adult rats contain the requisite intracellular components to process and potentially present endocytosed antigens.

RESULTS

M cells contained acid phosphatase-enriched prelysosomelike and lysosomelike structures. A basic congener of dinitrophenol, which concentrates in acidic cell compartments, is localized following its instillation into Peyer's patch-containing ligated jejunal loops to the endosomal-lysosomal system of M cells. Prelysosomelike and lysosomelike structures in ultrathin cryosections of M cells reacted with polyclonal antibody to a membrane glycoprotein (lgp120) enriched in prelysosomes and lysosomes. Using monoclonal antibody OX6 as a probe, M cells expressed the major histocompatibility complex (MHC) class II determinant, Ia, on the basolateral plasma membrane and in organelles with structural features of endosomes, prelysosomes, and lysosomes. Expression was enhanced by pretreatment with interferon gamma.

CONCLUSIONS

M cells possess acidic endosomal and acid phosphatase-containing prelysosomal and lysosomal compartments and express MHC class II determinants. Hence, M cells may have the capacity to process and present endocytosed antigens to adjacent intraepithelial T lymphocytes.

Cellular studies on antigen presentation by class II MHC molecules

Particularly prominent during the past year was the analysis of the subcellular compartment in which MHC class II molecules are located. Some investigators also analyzed the site where peptides are generated for MHC class II binding. Studies of invariant chain were particularly important in trying to establish the functional significance of this molecule.

Antigen processing for presentation by MHC class I molecules

The association of peptide fragments with MHC class I molecules is believed to be a requirement for the assembly of the MHC class I molecules in the endoplasmic reticulum, and transportation of the MHC molecules from the endoplasmic reticulum to the cell surface. Recently, investigators have begun to elucidate the mechanisms of fragmentation and transport of peptide fragments within antigen-presenting cells, and to define size and structure of naturally processed peptides bound to MHC complexes.