Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.305
Filtrar
1.
Elife ; 112022 12 14.
Artigo em Inglês | MEDLINE | ID: mdl-36515978

RESUMO

Malaria parasites avoid immune clearance through their ability to systematically alter antigens exposed on the surface of infected red blood cells. This is accomplished by tightly regulated transcriptional control of individual members of a large, multicopy gene family called var and is the key to both the virulence and chronic nature of malaria infections. Expression of var genes is mutually exclusive and controlled epigenetically, however how large populations of parasites coordinate var gene switching to avoid premature exposure of the antigenic repertoire is unknown. Here, we provide evidence for a transcriptional network anchored by a universally conserved gene called var2csa that coordinates the switching process. We describe a structured switching bias that shifts overtime and could shape the pattern of var expression over the course of a lengthy infection. Our results provide an explanation for a previously mysterious aspect of malaria infections and shed light on how parasites possessing a relatively small repertoire of variant antigen-encoding genes can coordinate switching events to limit antigen exposure, thereby maintaining chronic infections.


Malaria causes severe illness and deaths in hundreds of thousands of people each year. Most of them are young children in Sub-Saharan Africa. The disease is transmitted when a mosquito carrying single-celled Plasmodium parasites bites a human, introducing the parasites into the bloodstream, where they enter red blood cells. When a red blood cell becomes infected, the parasite presents a protein on the cell's surface that the immune system can recognize to start fighting the infection. Immune cells then produce antibodies that flag infected cells for destruction, relieving the symptoms of the disease. To avoid being destroyed in this manner, the parasites repeatedly 'change' the protein that ends up on the surface of the red blood cells. With each change, the number of parasites rebounds, symptoms return, and the immune system must produce new antibodies. As the parasites and immune system battle it out, patients may experience repeated flare-ups of symptoms for well over a year. To change the protein that is presented on the surface of red blood cells, Plasmodium parasites switch the genes in the var gene family on and off one at a time. Each of these genes encodes a different surface protein, and the parasites may cycle through the entire var gene family during an infection. However, it remains a mystery how the millions of infecting parasites coordinate to produce the same surface protein each time. Zhang et al. show that a gene from Plasmodium parasites called var2csa is responsible for coordinating protein switching through a set pattern that allows the parasites to synchronize which protein they switch to next. Deleting the var2csa gene in malaria parasites blocks protein switching and disables this coordinated immune evasion tactic. Zhang et al.'s experiments provide new insights about protein switching in malaria parasites. Further research may help scientists characterize each step in the process and identify which steps can be targeted to treat malaria. While not a cure, treatments that disable protein switching could reduce the number of times patients relapse and relieve symptoms. More generally, the results of Zhang et al. describe a mechanism for coordinated gene expression that may be used in organisms other than Plasmodium, including humans.


Assuntos
Malária Falciparum , Malária , Parasitos , Animais , Humanos , Malária Falciparum/parasitologia , Plasmodium falciparum , Proteínas de Protozoários/metabolismo , Variação Antigênica/genética , Antígenos
2.
Proc Natl Acad Sci U S A ; 119(42): e2211616119, 2022 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-36215486

RESUMO

Influenza B virus primarily infects humans, causing seasonal epidemics globally. Two antigenic variants-Victoria-like and Yamagata-like-were detected in the 1980s, of which the molecular basis of emergence is still incompletely understood. Here, the antigenic properties of a unique collection of historical virus isolates, sampled from 1962 to 2000 and passaged exclusively in mammalian cells to preserve antigenic properties, were determined with the hemagglutination inhibition assay and an antigenic map was built to quantify and visualize the divergence of the lineages. The antigenic map revealed only three distinct antigenic clusters-Early, Victoria, and Yamagata-with relatively little antigenic diversity in each cluster until 2000. Viruses with Victoria-like antigenic properties emerged around 1972 and diversified subsequently into two genetic lineages. Viruses with Yamagata-like antigenic properties evolved from one lineage and became clearly antigenically distinct from the Victoria-like viruses around 1988. Recombinant mutant viruses were tested to show that insertions and deletions (indels), as observed frequently in influenza B virus hemagglutinin, had little effect on antigenic properties. In contrast, amino-acid substitutions at positions 148, 149, 150, and 203, adjacent to the hemagglutinin receptor binding site, determined the main antigenic differences between the Early, Victoria-like, and Yamagata-like viruses. Surprisingly, substitutions at two of the four positions reverted in recent viruses of the Victoria lineage, resulting in antigenic properties similar to viruses circulating ∼50 y earlier. These data shed light on the antigenic diversification of influenza viruses and suggest there may be limits to the antigenic evolution of influenza B virus.


Assuntos
Influenza Humana , Animais , Variação Antigênica/genética , Sítios de Ligação , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Hemaglutininas , Humanos , Vírus da Influenza B/genética , Mamíferos , Filogenia
3.
Curr Opin Microbiol ; 70: 102209, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36215868

RESUMO

Survival of the African trypanosome within its mammalian hosts, and hence transmission between hosts, relies upon antigenic variation, where stochastic changes in the composition of their protective variant-surface glycoprotein (VSG) coat thwart effective removal of the pathogen by adaptive immunity. Antigenic variation has evolved remarkable mechanistic complexity in Trypanosoma brucei, with switching of the VSG coat executed by either transcriptional or recombination reactions. In the former, a single T. brucei cell selectively transcribes one telomeric VSG transcription site, termed the expression site (ES), from a pool of around 15. Silencing of the active ES and activation of one previously silent ES can lead to a co-ordinated VSG coat switch. Outside the ESs, the T. brucei genome contains an enormous archive of silent VSG genes and pseudogenes, which can be recombined into the ES to execute a coat switch. Most such recombination involves gene conversion, including copying of a complete VSG and more complex reactions where novel 'mosaic' VSGs are formed as patchworks of sequences from several silent (pseudo)genes. Understanding of the cellular machinery that directs transcriptional and recombination VSG switching is growing rapidly and the emerging picture is of the use of proteins, complexes and pathways that are not limited to trypanosomes, but are shared across the wider grouping of kinetoplastids and beyond, suggesting co-option of widely used, core cellular reactions. We will review what is known about the machinery of antigenic variation and discuss if there remains the possibility of trypanosome adaptations, or even trypanosome-specific machineries, that might offer opportunities to impair this crucial parasite-survival process.


Assuntos
Trypanosoma brucei brucei , Trypanosoma , Animais , Glicoproteínas Variantes de Superfície de Trypanosoma/genética , Variação Antigênica/genética , Trypanosoma/genética , Trypanosoma brucei brucei/genética , Genoma , Mamíferos/genética
4.
Curr Opin Microbiol ; 70: 102207, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36183663

RESUMO

A commonly observed survival strategy in protozoan parasites is the sequential expression of clonally variant-surface antigens to avoid elimination by the host's immune response. In malaria-causing P. falciparum, the immunovariant erythrocyte-membrane protein-1 (PfEMP1) adhesin family, encoded by var genes, is responsible for both antigenic variation and cytoadherence of infected erythrocytes to the microvasculature. Until recently, the biological function of these variant genes was believed to be restricted to intraerythrocytic developmental stages. With the advent of new technologies, var gene expression has been confirmed in transmission and pre-erythrocytic stages. Here, we discuss how repurposing of var gene expression beyond chronic blood-stage infection may be critical for successful transmission.


Assuntos
Antígenos de Protozoários , Malária Falciparum , Plasmodium falciparum , Humanos , Variação Antigênica , Antígenos de Protozoários/genética , Eritrócitos/parasitologia , Genes de Protozoários , Malária Falciparum/parasitologia , Plasmodium falciparum/genética , Proteínas de Protozoários/genética
5.
Biochemistry (Mosc) ; 87(9): 965-982, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36180987

RESUMO

Neisseria gonorrhoeae (a Gram-negative diplococcus) is a human pathogen and causative agent of gonorrhea, a sexually transmitted infection. The bacterium uses various approaches for adapting to environmental conditions and multiplying efficiently in the human body, such as regulation of expression of gene expression of surface proteins and lipooligosaccharides (e.g., expression of various forms of pilin). The systems of DNA repair play an important role in the bacterium ability to survive in the host body. This review describes DNA repair systems of N. gonorrhoeae and their role in the pathogenicity of this bacterium. A special attention is paid to the mismatch repair system (MMR) and functioning of the MutS and MutL proteins, as well as to the role of these proteins in regulation of the pilin antigenic variation of the N. gonorrhoeae pathogen.


Assuntos
Proteínas de Fímbrias , Neisseria gonorrhoeae , Variação Antigênica , Reparo do DNA , Proteínas de Fímbrias/metabolismo , Humanos , Proteínas MutL/metabolismo , Neisseria gonorrhoeae/genética , Neisseria gonorrhoeae/metabolismo
6.
Microbiol Spectr ; 10(5): e0174322, 2022 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-36150043

RESUMO

VlsE (variable major protein-like sequence, expressed) is an outer surface protein of the Lyme disease pathogen (Borreliella species) responsible for its within-host antigenic variation and a key diagnostic biomarker of Lyme disease. However, the high sequence variability of VlsE poses a challenge to the development of consistent VlsE-based diagnostics and therapeutics. In addition, the standard diagnostic protocols detect immunoglobins elicited by the Lyme pathogen, not the presence of the pathogen or its derived antigens. Here, we described the development of recombinant monoclonal antibodies (rMAbs) that bound specifically to conserved epitopes on VlsE. We first quantified amino-acid sequence variability encoded by the vls genes from 13 B. burgdorferi genomes by evolutionary analyses. We showed broad inconsistencies of the sequence phylogeny with the genome phylogeny, indicating rapid gene duplications, losses, and recombination at the vls locus. To identify conserved epitopes, we synthesized peptides representing five long conserved invariant regions (IRs) on VlsE. We tested the antigenicity of these five IR peptides using sera from three mammalian host species including human patients, the natural reservoir white-footed mouse (Peromyscus leucopus), and VlsE-immunized New Zealand rabbits (Oryctolagus cuniculus). The IR4 and IR6 peptides emerged as the most antigenic and reacted strongly with both the human and rabbit sera, while all IR peptides reacted poorly with sera from natural hosts. Four rMAbs binding specifically to the IR4 and IR6 peptides were identified, cloned, and purified. Given their specific recognition of the conserved epitopes on VlsE, these IR-specific rMAbs are potential novel diagnostic and research agents for direct detection of Lyme disease pathogens regardless of strain heterogeneity. IMPORTANCE Current diagnostic protocols of Lyme disease indirectly detect the presence of antibodies produced by the patient upon infection by the bacterial pathogen, not the pathogen itself. These diagnostic tests tend to underestimate early-stage bacterial infections before the patients develop robust immune responses. Further, the indirect tests do not distinguish between active or past infections by the Lyme disease bacteria in a patient sample. Here, we described novel monoclonal antibodies that have the potential to become the basis of direct and definitive diagnostic detection of the Lyme disease pathogen, regardless of its genetic heterogeneity.


Assuntos
Borrelia burgdorferi , Doença de Lyme , Humanos , Coelhos , Animais , Borrelia burgdorferi/genética , Borrelia burgdorferi/metabolismo , Epitopos/genética , Antígenos de Bactérias , Anticorpos Monoclonais , Lipoproteínas/metabolismo , Proteínas de Bactérias/genética , Doença de Lyme/diagnóstico , Doença de Lyme/microbiologia , Variação Antigênica , Proteínas de Membrana/genética , Peptídeos/genética , Biomarcadores , Anticorpos Antibacterianos , Mamíferos/metabolismo
7.
Genomics ; 114(5): 110462, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35998788

RESUMO

Giardia lamblia encodes several families of cysteine-rich proteins, including the Variant-specific Surface Proteins (VSPs) involved in the process of antigenic variation. Their characteristics, definition and relationships are still controversial. An exhaustive analysis of the Cys-rich families including organization, features, evolution and levels of expression was performed, by combining pattern searches and predictions with massive sequencing techniques. Thus, a new classification for Cys-rich proteins, genes and pseudogenes that better describes their involvement in Giardia's biology is presented. Moreover, three novel characteristics exclusive to the VSP genes, comprising an Initiator element/Kozak-like sequence, an extended polyadenylation signal and a unique pattern of mutually exclusive transcript accumulation are presented, as well as the finding that High Cysteine Membrane Proteins, upregulated under stress, may protect the parasite during VSP switching. These results allow better interpretation of previous reports providing the basis for further studies of the biology of this early-branching eukaryote.


Assuntos
Giardia lamblia , Variação Antigênica/genética , Antígenos de Protozoários , Antígenos de Superfície/genética , Cisteína/genética , Giardia lamblia/genética , Giardia lamblia/metabolismo , Proteínas de Membrana/genética , Proteínas de Protozoários/genética
9.
Methods Mol Biol ; 2470: 211-220, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35881348

RESUMO

One of the key mechanisms contributing to the virulence of Plasmodium falciparum is its ability to undergo antigenic switching among antigenically distinct variants of the PfEMP1 adhesive proteins, encoded by the var gene family. To avoid premature exposure of its antigenic repertoire, the parasite transcribes its var genes in a mutually exclusive manner, and switch expression at a very slow rate. This process is epigenetically regulated and it relies on "epigenetic memory," which imprints the single active var gene to remain active for multiple replication cycles. Erasing this epigenetic memory in parasites grown in culture resembles parasites, which egress from the liver. It could therefore be of interest for investigating var switching patterns at the onset of malaria infections. In addition, this procedure could be used for creating heterogeneity of var expression among parasite populations. The methodology described here for resetting of var gene expression is based on promoter titration, also known as molecular sponging.


Assuntos
Malária Falciparum , Plasmodium falciparum , Variação Antigênica , Regulação da Expressão Gênica , Humanos , Malária Falciparum/parasitologia , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/metabolismo , Transcrição Genética
10.
Methods Mol Biol ; 2470: 241-253, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35881350

RESUMO

The virulence of Plasmodium falciparum has been attributed in large part to the expression on the surface of infected red blood cells of the variant surface antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). Different forms of this protein are encoded by individual members of the multicopy gene family called var. Two attributes of the var gene family are key to the pathogenesis of malaria caused by P. falciparum; the hyperrecombinogenic nature of the var gene family that continuously generates antigenic diversity within parasite populations, and the ability of parasites to express only a single var gene at a time and to switch which gene is expressed over the course of an infection. The unique attributes of CRISPR-Cas9 have been applied to help decipher the molecular mechanisms underlying these unusual properties of the var gene family, both as a source of the DNA double strand breaks that initiate var gene recombination and as a way to recruit molecular probes to specific regions of the genome. In this chapter, we describe these somewhat unusual applications of the CRISPR-Cas9 system.


Assuntos
Malária Falciparum , Parasitos , Animais , Variação Antigênica , Sistemas CRISPR-Cas/genética , Regulação da Expressão Gênica , Malária Falciparum/genética , Malária Falciparum/parasitologia , Parasitos/metabolismo , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/metabolismo
11.
Methods Mol Biol ; 2470: 537-543, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35881373

RESUMO

The var genes encoding the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) mediating adhesion of infected erythrocytes (IEs) are clonally variant and confer the parasite the ability to evade the host immune response by enabling switching among expression of different PfEMP1 variants. This method of antigenic variation allows the parasite to adhere to a variety of proteins to escape splenic clearance. Enriching IE populations for expression of a specific PfEMP1 variant is crucial for the study of specific var genes PfEMP1 proteins and their role in pathogenicity. Selection of parasites using cell monolayers requires large-volume cultures (>5 mL). This chapter describes a method, which rapidly selects for adhesive phenotypes of interest using small-volume cultures (<1 mL) under physiological flow conditions.


Assuntos
Malária Falciparum , Parasitos , Animais , Variação Antigênica , Antígenos de Protozoários/genética , Eritrócitos/metabolismo , Malária Falciparum/parasitologia , Parasitos/metabolismo , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/metabolismo
12.
Nat Microbiol ; 7(8): 1280-1290, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35879525

RESUMO

Variant surface glycoprotein (VSG) coats bloodstream form Trypanosoma brucei parasites, and monoallelic VSG expression underpins the antigenic variation necessary for pathogenicity. One of thousands of VSG genes is transcribed by RNA polymerase I in a singular nuclear structure called the expression site body (ESB), but how monoallelic VSG transcription is achieved remains unclear. Using a localization screen of 153 proteins we found one, ESB-specific protein 1 (ESB1), that localized only to the ESB and is expressed only in VSG-expressing life cycle stages. ESB1 associates with DNA near the active VSG promoter and is necessary for VSG expression, with overexpression activating inactive VSG promoters. Mechanistically, ESB1 is necessary for recruitment of a subset of ESB components, including RNA polymerase I, revealing that the ESB has separately assembled subdomains. Because many trypanosomatid parasites have divergent ESB1 orthologues yet do not undergo antigenic variation, ESB1 probably represents an important class of transcription regulators.


Assuntos
Trypanosoma brucei brucei , Variação Antigênica/genética , Glicoproteínas de Membrana/metabolismo , RNA Polimerase I/genética , RNA Polimerase I/metabolismo , Fatores de Transcrição/genética , Glicoproteínas Variantes de Superfície de Trypanosoma/metabolismo
13.
Vet Res ; 53(1): 43, 2022 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-35706014

RESUMO

Based on differences in the amino acid sequence of the protein haemagglutinin (HA), the H9N2 avian influenza virus (H9N2 virus) has been clustered into multiple lineages, and its rapidly ongoing evolution increases the difficulties faced by prevention and control programs. The HA protein, a major antigenic protein, and the amino acid mutations that alter viral antigenicity in particular have always been of interest. Likewise, it has been well documented that some amino acid mutations in HA alter viral antigenicity in the H9N2 virus, but little has been reported regarding how these antibody escape mutations affect antigenic variation. In this study, we were able to identify 15 HA mutations that were potentially relevant to viral antigenic drift, and we also found that a key amino acid mutation, A180V, at position 180 in HA (the numbering for mature H9 HA), the only site of the receptor binding sites that is not conserved, was directly responsible for viral antigenic variation. Moreover, the recombinant virus with alanine to valine substitution at position 180 in HA in the SH/F/98 backbone (rF/HAA180V virus) showed poor cross-reactivity to immune sera from animals immunized with the SH/F/98 (F/98, A180), SD/SS/94 (A180), JS/Y618/12 (T180), and rF/HAA180V (V180) viruses by microneutralization (MN) assay. The A180V substitution in the parent virus caused a significant decrease in cross-MN titres by enhancing the receptor binding activity, but it did not physically prevent antibody (Ab) binding. The strong receptor binding avidity prevented viral release from cells. Moreover, the A180V substitution promoted H9N2 virus escape from an in vitro pAb-neutralizing reaction, which also slightly affected the cross-protection in vivo. Our results suggest that the A180V mutation with a strong receptor binding avidity contributed to the low reactors in MN/HI assays and slightly affected vaccine efficacy but was not directly responsible for immune escape, which suggested that the A180V mutation might play a key role in the process of the adaptive evolution of H9N2 virus.


Assuntos
Vírus da Influenza A Subtipo H9N2 , Influenza Aviária , Influenza Humana , Substituição de Aminoácidos , Aminoácidos , Animais , Variação Antigênica , Antígenos Virais/genética , Galinhas , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Hemaglutininas , Humanos , Vírus da Influenza A Subtipo H9N2/genética , Vacinas contra Influenza , Mutação
14.
mSphere ; 7(4): e0012222, 2022 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-35727016

RESUMO

African trypanosomes evade the immune system of the mammalian host by the antigenic variation of the predominant glycosylphosphatidylinositol (GPI)-anchored surface protein, variant surface glycoprotein (VSG). VSG is a very stable protein that is turned over from the cell surface with a long half-life (~26 h), allowing newly synthesized VSG to populate the surface. We have recently demonstrated that VSG turnover under normal growth is mediated by a combination of GPI hydrolysis and direct shedding with intact GPI anchors. VSG synthesis is tightly regulated in dividing trypanosomes, and when subjected to RNA interference (RNAi) silencing, cells display rapid cell cycle arrest in order to conserve VSG density on the cell surface (K. Sheader, S. Vaughan, J. Minchin, K. Hughes, et al., Proc Natl Acad Sci U S A 102:8716-8721, 2005, https://doi.org/10.1073/pnas.0501886102). Arrested cells also display an altered morphology of secretory organelles-engorgement of the trans-Golgi cisternae-that may reflect a disruption of post-Golgi secretory transport. We now ask whether trypanosomes under VSG silencing also reduce the rate of VSG turnover to further conserve coat density. Our data indicate that trypanosomes do not regulate VSG turnover according to VSG protein abundance, nor was there any effect on the post-Golgi transport of soluble or GPI-anchored secretory cargo. However, the surface morphology of silenced cells was altered from a typically rugose topology to a smoother profile, consistent with reduced overall membrane trafficking to the cell surface. IMPORTANCE African trypanosomes evade the host immune system by altering the expression of variant surface glycoproteins (VSGs) in a process called antigenic variation. VSG is essential, and when its synthesis is ablated by RNAi silencing, cells enter precytokinesis growth arrest as a means to maintain constant cell surface VSG levels. We have investigated whether arrested cells also alter the rate of natural VSG turnover as a means to conserve the surface coat. This work provides insights into the natural biology of the glycocalyx of this important human and veterinary parasite.


Assuntos
Trypanosoma brucei brucei , Animais , Variação Antigênica , Glicosilfosfatidilinositóis , Humanos , Mamíferos , Glicoproteínas de Membrana/genética , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/metabolismo , Glicoproteínas Variantes de Superfície de Trypanosoma/genética , Glicoproteínas Variantes de Superfície de Trypanosoma/metabolismo
15.
Transfusion ; 62(7): 1347-1354, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35588314

RESUMO

BACKGROUND: The therapeutic benefit of convalescent plasma (CP) therapy to treat COVID-19 may derive from neutralizing antibodies (nAbs) to SARS-CoV-2. To investigate the effects of antigenic variation on neutralization potency of CP, we compared nAb titers against prototype and recently emerging strains of SARS-CoV-2, including Delta and Omicron, in CP donors previously infected with SARS-CoV-2 before and after immunization. METHODS AND MATERIALS: Samples were assayed from previously SARS-CoV-2 infected donors before (n = 17) and after one (n = 43) or two (n = 71) doses of Astra-Zeneca or Pfizer vaccinations. Ab titers against Wuhan/wild type (WT), Alpha, Beta, and Delta SARS-CoV-2 strains were determined by live virus microneutralization assay while titers to Omicron used a focus reduction neutralization test. Anti-spike antibody was assayed by Elecsys anti-SARS-CoV-2 quantitative spike assay (Roche). RESULTS: Unvaccinated donors showed a geometric mean titer (GMT) of 148 against WT, 80 against Alpha but mostly failed to neutralize Beta, Delta, and Omicron strains. Contrastingly, high GMTs were observed in vaccinated donors against all SARS-CoV-2 strains after one vaccine dose (WT:703; Alpha:692; Beta:187; Delta:215; Omicron:434). By ROC analysis, reactivity in the Roche quantitative Elecsys spike assay of 20,000 U/mL was highly predictive of donations with nAb titers of ≥1:640 against Delta (90% sensitivity; 97% specificity) and ≥1:320 against Omicron (89% sensitivity; 81% specificity). DISCUSSION: Vaccination of previously infected CP donors induced high levels of broadly neutralizing antibodies against circulating antigenic variants of SARS-CoV-2. High titer donations could be reliably identified by automated quantitative anti-spike antibody assay, enabling large-scale preselection of high-titer convalescent plasma.


Assuntos
Anticorpos Neutralizantes , COVID-19 , Anticorpos Antivirais , Variação Antigênica , COVID-19/terapia , Humanos , Imunização , Imunização Passiva , SARS-CoV-2 , Vacinação
17.
PLoS Pathog ; 18(5): e1010511, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35605029

RESUMO

Hematogenous dissemination is a critical step in the evolution of local infection to systemic disease. The Lyme disease (LD) spirochete, which efficiently disseminates to multiple tissues, has provided a model for this process, in particular for the key early event of pathogen adhesion to the host vasculature. This occurs under shear force mediated by interactions between bacterial adhesins and mammalian cell-surface proteins or extracellular matrix (ECM). Using real-time intravital imaging of the Lyme spirochete in living mice, we previously identified BBK32 as the first LD spirochetal adhesin demonstrated to mediate early vascular adhesion in a living mouse; however, deletion of bbk32 resulted in loss of only about half of the early interactions, suggesting the existence of at least one other adhesin (adhesin-X) that promotes early vascular interactions. VlsE, a surface lipoprotein, was identified long ago by its capacity to undergo rapid antigenic variation, is upregulated in the mammalian host and required for persistent infection in immunocompetent mice. In immunodeficient mice, VlsE shares functional overlap with OspC, a multi-functional protein that displays dermatan sulfate-binding activity and is required for joint invasion and colonization. In this research, using biochemical and genetic approaches as well as intravital imaging, we have identified VlsE as adhesin-X; it is a dermatan sulfate (DS) adhesin that efficiently promotes transient adhesion to the microvasculature under shear force via its DS binding pocket. Intravenous inoculation of mice with a low-passage infectious B. burgdorferi strain lacking both bbk32 and vlsE almost completely eliminated transient microvascular interactions. Comparative analysis of binding parameters of VlsE, BBK32 and OspC provides a possible explanation why these three DS adhesins display different functionality in terms of their ability to promote early microvascular interactions.


Assuntos
Adesinas Bacterianas , Variação Antigênica , Antígenos de Bactérias , Proteínas de Bactérias , Borrelia burgdorferi , Lipoproteínas , Doença de Lyme , Microvasos , Adesinas Bacterianas/genética , Adesinas Bacterianas/imunologia , Animais , Variação Antigênica/genética , Variação Antigênica/imunologia , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Aderência Bacteriana/genética , Aderência Bacteriana/imunologia , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/imunologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/imunologia , Borrelia burgdorferi/genética , Borrelia burgdorferi/imunologia , Dermatan Sulfato/imunologia , Lipoproteínas/genética , Lipoproteínas/imunologia , Doença de Lyme/genética , Doença de Lyme/imunologia , Doença de Lyme/microbiologia , Mamíferos , Camundongos , Microvasos/imunologia , Microvasos/microbiologia , Resistência ao Cisalhamento
18.
Front Cell Infect Microbiol ; 12: 869696, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35493746

RESUMO

Apicomplexan parasites live in hostile environments in which they are challenged chemically and their hosts attempt in many ways to kill them. In response, the parasites have evolved multiple mechanisms that take advantage of these challenges to enhance their survival. Perhaps the most impressive example is the evolutionary co-option of DNA repair mechanisms by the parasites as a means to rapidly manipulate the structure, antigenicity, and expression of the products of specific multigene families. The purpose of variant proteins that mediate cytoadhesion has long been thought to be primarily the avoidance of splenic clearance. Based upon known biology, I present an alternative perspective in which it is survival of the oxidative environment within which Babesia spp. parasites live that has driven integration of DNA repair, antigenic variation, and cytoadhesion, and speculate on how genome organization affects that integration. This perspective has ramifications for the development of parasite control strategies.


Assuntos
Babesia , Parasitos , Animais , Variação Antigênica/genética , Babesia/genética , Reparo do DNA , Família Multigênica
19.
Microbes Infect ; 24(6-7): 104982, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35487471

RESUMO

Trypanosoma cruzi, the etiological agent of Chagas disease (CD), is a heterogeneous species with high genetic and phenotypic diversity. MASP is the second largest multigene family of T. cruzi. The high degree of polymorphism of the family associated with its location at the surface of infective forms of T. cruzi suggests that MASP participates in mechanisms of host-parasite interaction. In this work, MASP members were divided into 7 subgroups based on protein sequence similarity, and one representative member from each subgroup was chosen to be expressed recombinantly. Immunogenicity of recombinant MASP proteins (rMASP) was investigated using different sera panels from T. cruzi infected mice. To mimic a natural condition in which different MASP members are expressed at the same time in the parasite population, a multiplex bead-based flow cytometry assay was also standardized. Results showed that rMASPs are poorly recognized by sera from mice infected with Colombiana strain, whereas sera from mice infected with CL Brener and Y display high reactivity against the majority of rMASPs tested. Flow cytometry showed that MASP recognition profile changes 10 days after infection. Also, multiplex assay suggests that MASP M1 and M2 are more immunogenic than the other MASP members evaluated that may play an immunodominant role during infection.


Assuntos
Doença de Chagas , Trypanosoma cruzi , Animais , Variação Antigênica , Doença de Chagas/parasitologia , Serina Proteases Associadas a Proteína de Ligação a Manose/genética , Serina Proteases Associadas a Proteína de Ligação a Manose/metabolismo , Camundongos , Proteínas de Protozoários/metabolismo , Trypanosoma cruzi/genética , Trypanosoma cruzi/metabolismo
20.
PLoS One ; 17(3): e0266198, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35344562

RESUMO

The growing risk of new variants of the influenza A virus is the most significant to public health. The risk imposed from new variants may have been lethal, as witnessed in the year 2009. Even though the improvement in predicting antigenicity of influenza viruses has rapidly progressed, few studies employed deep learning methodologies. The most recent literature mostly relied on classification techniques, while a model that generates the HA protein of the antigenic variant is not developed. However, the antigenic pair of influenza virus A can be determined in a laboratory setup, the process needs a tremendous amount of time and labor. Antigenic shift and drift which are caused by changes in surface protein favored the influenza A virus in evading immunity. The high frequency of the minor changes in the surface protein poses a challenge to identifying the antigenic variant of an emerging virus. These changes slow down vaccine selection and the manufacturing process. In this vein, the proposed model could help save the time and efforts exerted to identify the antigenic pair of the influenza virus. The proposed model utilized an end-to-end learning methodology relying on deep sequence-to-sequence architecture to generate the antigenic variant of a given influenza A virus using surface protein. Employing the BLEU score to evaluate the generated HA protein of the antigenic variant of influenza virus A against the actual variant, the proposed model achieved a mean accuracy of 97.57%.


Assuntos
Glicoproteínas de Hemaglutininação de Vírus da Influenza , Vírus da Influenza A Subtipo H1N1 , Variação Antigênica , Antígenos Virais/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Humanos , Vírus da Influenza A Subtipo H1N1/genética , Influenza Humana/virologia , Proteínas de Membrana
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...