An overview of retrovirus replication and classification

Emerging Strategies in Mesenchymal Stem Cell-Based Cardiovascular Therapeutics

Cardiovascular diseases continue to challenge global health, demanding innovative therapeutic solutions. This review delves into the transformative role of mesenchymal stem cells (MSCs) in advancing cardiovascular therapeutics. Beginning with a historical perspective, we trace the development of stem cell research related to cardiovascular diseases, highlighting foundational therapeutic approaches and the evolution of cell-based treatments. Recognizing the inherent challenges of MSC-based cardiovascular therapeutics, which range from understanding the pro-reparative activity of MSCs to tailoring patient-specific treatments, we emphasize the need to refine the pro-regenerative capacity of these cells. Crucially, our focus then shifts to the strategies of the fourth generation of cell-based therapies: leveraging the secretomic prowess of MSCs, particularly the role of extracellular vesicles; integrating biocompatible scaffolds and artificial sheets to amplify MSCs' potential; adopting three-dimensional ex vivo propagation tailored to specific tissue niches; harnessing the promise of genetic modifications for targeted tissue repair; and institutionalizing good manufacturing practice protocols to ensure therapeutic safety and efficacy. We conclude with reflections on these advancements, envisaging a future landscape redefined by MSCs in cardiovascular regeneration. This review offers both a consolidation of our current understanding and a view toward imminent therapeutic horizons.

N123I mutation in the ALV-J receptor-binding domain region enhances viral replication ability by increasing the binding affinity with chNHE1

The subgroup J avian leukosis virus (ALV-J), a retrovirus, uses its gp85 protein to bind to the receptor, the chicken sodium hydrogen exchanger isoform 1 (chNHE1), facilitating viral invasion. ALV-J is the main epidemic subgroup and shows noteworthy mutations within the receptor-binding domain (RBD) region of gp85, especially in ALV-J layer strains in China. However, the implications of these mutations on viral replication and transmission remain elusive. In this study, the ALV-J layer strain JL08CH3-1 exhibited a more robust replication ability than the prototype strain HPRS103, which is related to variations in the gp85 protein. Notably, the gp85 of JL08CH3-1 demonstrated a heightened binding capacity to chNHE1 compared to HPRS103-gp85 binding. Furthermore, we showed that the specific N123I mutation within gp85 contributed to the enhanced binding capacity of the gp85 protein to chNHE1. Structural analysis indicated that the N123I mutation primarily enhanced the stability of gp85, expanded the interaction interface, and increased the number of hydrogen bonds at the interaction interface to increase the binding capacity between gp85 and chNHE1. We found that the N123I mutation not only improved the viral replication ability of ALV-J but also promoted viral shedding in vivo. These comprehensive data underscore the notion that the N123I mutation increases receptor binding and intensifies viral replication.

A metagenomic comparison of endemic viruses from broiler chickens with runting-stunting syndrome and from normal birds

Runting-stunting syndrome (RSS) in broiler chickens is an enteric disease that causes significant economic losses to poultry producers worldwide due to elevated feed conversion ratios, decreased body weight during growth, and excessive culling. Of specific interest are the viral agents associated with RSS which have been difficult to fully characterize to date. Past research into the aetiology of RSS has implicated a wide variety of RNA and DNA viruses however, to date, no individual virus has been identified as the main agent of RSS and the current opinion is that it may be caused by a community of viruses, collectively known as the virome. This paper attempts to characterize the viral pathogens associated with 2–3-week-old RSS-affected and unaffected broiler chickens using next-generation sequencing and comparative metagenomics. Analysis of the viromes identified a total of 20 DNA and RNA viral families, along with 2 unidentified categories, comprised of 31 distinct viral genera and 7 unclassified genera. The most abundant viral families identified in this study were the Astroviridae, Caliciviridae, Picornaviridae, Parvoviridae, Coronaviridae, Siphoviridae, and Myoviridae. This study has identified historically significant viruses associated with the disease such as chicken astrovirus, avian nephritis virus, chicken parvovirus, and chicken calicivirus along with relatively novel viruses such as chicken megrivirus and sicinivirus 1 and will help expand the knowledge related to enteric disease in broiler chickens, provide insights into the viral constituents of a healthy avian gut, and identify a variety of enteric viruses and viral communities appropriate for further study.

Linfossarcoma em bovinos no Agreste Meridional de Pernambuco

Neste trabalho são descritos os sinais clínicos, patologia clínica e patologia de 24 bovinos com leucose bovina enzoótica atendidos na Clínica de Bovinos de Garanhuns da Universidade Federal Rural de Pernambuco. Esses casos representaram 0,5% de 4.758 bovinos atendidos entre os anos de 2000 e 2010. A doença afetou 22 (91,7%) fêmeas e dois machos. Vinte e um animais (87,5%) eram de raças leiteras (seis Holandês, 13 Girolando, um Jersey e um Pardo Suíça) e três (12,5%) eram da raça Nelore. Vinte e três animais (95,8%) tinham idade entre 3 e 8 anos e um era mais jovem. Todos eram criados em regime de confinamento ou semi-confinamento. Clinicamente todos os animais apresentaram aumento dos linfonodos superficias. Outros sinais frequentes foram hiporexia, diminuição da produção de leite, emagrecimento progressivo, escore corporal baixo, desidratação, hipomotilidade dos pré-estômagos e fezes alteradas e em pouca quantidade. Com menor frequência foram observados exoftalmia, dispneia e aumento de volume do útero. No leucograma foi constatada leucocitose média de 34.082/µL, com linfocitose de 21.814/µL e neutrofilia de 10.906/µL. Treze animais foram necropsiados e os demais foram enviados pelos proprietários para o abate. Dos treze animais abatidos todos apresentaram lesões nos linfonodos superficiais, seis nos linfonodos mesentéricos, seis no intestino, três no abomaso, um no coração, um no fígado, um no rúmen, um no útero e um no rim. Diante da importância desta enfermidade e dos prejuízos causados pela mesma é necessário alertar produtores sobre os cuidados a serem tomados durante a aquisição de animais, assim como da necessidade de implantar medidas que evitem a difusão da doença entre as fazendas.

Proteolytic processing of the human T-cell lymphotropic virus 1 reverse transcriptase: identification of the N-terminal cleavage site by mass spectrometry

Human T-cell lymphotropic virus 1 (HTLV-1) is a type C human retrovirus, which is the causative agent of Adult T-cell Leukemia and other diseases. The reverse transcriptase of HTLV-1 (E.C. 2.7.7.49) is synthesized as part of a Gag--Pro--Pol precursor protein, and the mature Gag, Pro, and Pol proteins, including the reverse transcriptase, are created by proteolytic processing catalyzed by the viral protease. The location of the proteolytic cleavage site, which creates the N-terminus of mature HTLV-1 reverse transcriptase, has not been previously identified. By using sequence comparisons of several retroviral polymerases, as well as information about the location of the ribosomal frameshift, we tentatively identified this N-terminal processing site. PCR amplification was used to construct a clone, which spans a region of the pro--pol junction of HTLV-1, to produce a recombinant Pro--Pol protein spanning the locations of those cleavage sites proposed by others as well as the one identified by our sequence alignment. Cleavage of the recombinant Pro--Pol protein by HTLV-1 protease generated a 5.5-kDa fragment. Analysis of this fragment by capillary LC-MS and MS/MS revealed the N-terminal cleavage site to be between Leu(147)--Pro(148) of the pro ORF. This is the first physical identification of the authentic amino acid sequence of the reverse transcriptase of HTLV-1. The data reported here provides a basis for further investigation of the function and structural aspects of protein-nucleic interaction.

Preliminary analysis of the polypeptides of the salmon leukemia virus (SLV) and evidence for development of a bimodal viremia following SLV infection

A retrovirus, known as salmon leukemia virus (SLV), was purified from farm-reared chinook salmon (Oncorhynchus tshawytscha) with plasmacytoid leukemia (PL). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of purified SLV revealed the presence of 9 virus-associated polypeptides with molecular weights from 82 kDa to 15 kDa. Endoglycosidase digestion and alcian blue staining of viral polypeptides separated by SDS-PAGE, and immunoprecipitation experiments using hyperimmune antisera suggest that the non-glycosylated 27 kDa polypeptide may represent a capsid-associated protein and the 82 kDa glycoprotein may represent an envelope-associated protein, which appears to be composed of a 67 kDa protein moiety. Fish injected with PL-positive tissue homgenate developed a bimodal viremia, as indicated by the presence of cell-free, virus-associated reverse transcriptase activity and SLV in serum of fish from 1 to 3 wk post-injection and again from 7 wk on through the rest of the study. If horizontal transmission of SLV and PL occurs in infected chinook salmon, it is most likely to occur after the second viremic period begins.

Macroepidemiology of the HIVs-AIDS (HAIDS) pandemic. Insufficiently considered zoological and geopolitical aspects

The human immunodeficiency viruses (HIVs)-acquired immunodeficiency syndrome (AIDS) or HAIDS pandemic originated from lentiviruses of nonhuman primates (thus qualifying as a zoonosis) that moved into humans in Africa. The HAIDS patients eventually die of opportunistic infections, all potentially zoonotic. The HAIDS infection remained parochial, first endemically and then epidemically, until the African urbanization that occurred in each of the countries postindependence. The latter included wars and the massive movement of soldiers (virologically naive) from the American continent to Africa and back. The HAIDS viral ecology coincided with African swine fever (ASF) in the Americas. Haiti became the focal point for both infections. Some infected Haitians also became, together with some infected drug addicts in the United States, a source of contaminated human blood for transfusions and production of plasma derivatives.

Spatial visualization of the maturing HIV-1 core and its linkage to the envelope

The core of late states of maturing human immunodeficiency virus type 1 (HIV-1) has been visualized in three dimensions at approximately 7 nm resolution by electron microscopic tomography. After budding, approximately 25 nm thick precursor material is observed densely assembled inside the viral envelope. Upon proteolysis the core material is transported and condensed in the center of the virion. The core, 100 nm in length, spans the entire diameter of the virion showing a 40-60 nm wide free end and a narrow end approximately 20 nm. A model of the core is derived consisting of two fibers packed into a bilateral, elongated structure. Two ends of the fibers are compacted together, forming one narrow end of the core, while the two other fiber ends are situated more loosely together allowing for flexibility. Structural maturation of the virus could be reflected by the degree of compactness of the core. The narrow end of the core is observed attached to the envelope with a conspicuous core-envelope link (CEL).

Endogenous origin of defective retroviruslike particles from a recombinant Chinese hamster ovary cell line

The presence of budding C-type and intracytoplasmic A-type particles in Chinese hamster ovary (CHO) cells is well documented. However, extensive screening has failed to detect any evidence of infectivity. Continuous-flow ultracentrifugation has been used to concentrate extracellular particles from culture fluid of a recombinant CHO cell subclone for molecular characterization. Particles exhibiting reverse transcriptase activity and associated with mammalian C-type retrovirus structural proteins banded in sucrose gradients at a density characteristic of retroviruses. Examination of gradient-purified particles by electron microscopy revealed morphology and size similar to other retroviruses. Double-gradient-purified particles contained RNA which hybridized to probes for murine leukemia virus, and endogenous Chinese hamster intracisternal A-particle elements. DNA sequence analysis of a cDNA clone isolated from purified particles revealed multiple interruptions of the endonuclease reading frame, providing one possible explanation for the noninfectious nature of the observed particles. Sequences present as RNA in purified particles were also present as conserved, repetitive, provirus sequences in genomic DNA of all CHO cell lines examined and in Chinese hamster liver DNA. The observed particles are therefore likely to be the products of endogenous retroviruslike elements present in the germline of Chinese hamsters.