Search Results (9)

Feline leukaemia virus (FeLV) is a member of the Gammaretrovirus genus, which has two genotypes in cats: endogenous (replication-defective provirus) and exogenous (replication-competent). In this study, 550 cats were examined, and 112 of them (20.36%) were found to have the endogenous FeLV (enFeLV) genotype. EnFeLV-positive animals were also tested for additional viral infections, and 48 cats (42.85%) were discovered to be co-infected with other viruses. According to co-infection data, these cats were infected with feline coronavirus (FCoV) (27/112, 24.1%), feline panleukopenia virus (FPV) (14/112, 12.5%), feline immunodeficiency virus (FIV) (0/112, 0%), and domestic cat hepadnavirus (DCH) (13/112, 11.6%). Their age, sex, breed, clinical state, lifestyle (in/outdoor), and immunization data against FeLV were also evaluated. In line with our results, the prevalence of enFeLV and co-infection with other pathogens in cats admitted to the clinic for various reasons were discussed. The majority of positive animals in terms of FeLV (94/112, 83.93%) had clinical findings. We emphasized that the FeLV-positive situation of cats should be taken into consideration by veterinarians when planning treatment and vaccination programs. Additionally, in this study, we questioned the group in which our enFeLVs were phylogenetically located. Therefore, we performed a phylogenetic analysis based on a comparison with global FeLV sequences obtained from the GenBank database. The sequenced positive samples were in the AGTT subgroup within Group-II. Full article

Despite remarkable progress, a cure for HIV-1 infection remains elusive. Rebound competent latent and transcriptionally active reservoir cells persevere despite antiretroviral therapy and rekindle infection due to inefficient proviral silencing. We propose a novel “block-lock-stop” approach, entailing long term durable silencing of viral expression towards an irreversible transcriptionally inactive latent provirus to achieve long term antiretroviral free control of the virus. A graded transformation of remnant HIV-1 in PLWH from persistent into silent to permanently defective proviruses is proposed, emulating and accelerating the natural path that human endogenous retroviruses (HERVs) take over millions of years. This hypothesis was based on research into delineating the mechanisms of HIV-1 latency, lessons from latency reversing agents and advances of Tat inhibitors, as well as expertise in the biology of HERVs. Insights from elite controllers and the availability of advanced genome engineering technologies for the direct excision of remnant virus set the stage for a rapid path to an HIV-1 cure. Full article

A cure for HIV-1 (HIV) remains unrealized due to a reservoir of latently infected cells that persist during antiretroviral therapy (ART), with reservoir size associated with adverse health outcomes and inversely with time to viral rebound upon ART cessation. Once established during ART, the HIV reservoir decays minimally over time; thus, understanding factors that impact the size of the HIV reservoir near its establishment is key to improving the health of people living with HIV and for the development of novel cure strategies. Yet, to date, few correlates of HIV reservoir size have been identified, particularly in pediatric populations. Here, we employed a cross-subtype intact proviral DNA assay (CS-IPDA) to quantify HIV provirus between one- and two-years post-ART initiation in a cohort of Kenyan children (n = 72), which had a median of 99 intact (range: 0–2469), 1340 defective (range: 172–3.84 × 10⁴), and 1729 total (range: 178–5.11 × 10⁴) HIV proviral copies per one million T cells. Additionally, pre-ART plasma was tested for HIV Env-specific antibody-dependent cellular cytotoxicity (ADCC) activity. We found that pre-ART gp120-specific ADCC activity inversely correlated with defective provirus levels (n = 68, r = −0.285, p = 0.0214) but not the intact reservoir (n = 68, r = −0.0321, p-value = 0.800). Pre-ART gp41-specific ADCC did not significantly correlate with either proviral population (n = 68; intact: r = −0.0512, p-value = 0.686; defective: r = −0.109, p-value = 0.389). This suggests specific host immune factors prior to ART initiation can impact proviruses that persist during ART. Full article

HIV-associated cognitive dysfunction during combination antiretroviral therapy (cART) involves mitochondrial dysfunction, but the impact of contemporary cART on chronic metabolic changes in the brain and in latent HIV infection is unclear. We interrogated mitochondrial function in a human microglia (hμglia) cell line harboring inducible HIV provirus and in SH-SY5Y cells after exposure to individual antiretroviral drugs or cART, using the MitoStress assay. cART-induced changes in protein expression, reactive oxygen species (ROS) production, mitochondrial DNA copy number, and cellular iron were also explored. Finally, we evaluated the ability of ROS scavengers or plasmid-mediated overexpression of the antioxidant iron-binding protein, Fth1, to reverse mitochondrial defects. Contemporary antiretroviral drugs, particularly bictegravir, depressed multiple facets of mitochondrial function by 20–30%, with the most pronounced effects in latently infected HIV+ hμglia and SH-SY5Y cells. Latently HIV-infected hμglia exhibited upregulated glycolysis. Increases in total and/or mitochondrial ROS, mitochondrial DNA copy number, and cellular iron accompanied mitochondrial defects in hμglia and SH-SY5Y cells. In SH-SY5Y cells, cART reduced mitochondrial iron–sulfur-cluster-containing supercomplex and subunit expression and increased Nox2 expression. Fth1 overexpression or pre-treatment with N-acetylcysteine prevented cART-induced mitochondrial dysfunction. Contemporary cART impairs mitochondrial bioenergetics in hμglia and SH-SY5Y cells, partly through cellular iron accumulation; some effects differ by HIV latency. Full article

Bovine leukemia virus (BLV) infects cattle and integrates into host DNA, causing enzootic bovine leukosis (EBL), an aggressive B-cell lymphoma. Here, we developed a novel proviral DNA-capture sequencing (proviral DNA-capture-seq) method investigating BLV proviral integration in two B-cell lymphoma lines, BLSC-KU1 and BLSC-KU17, derived from BLV-infected cattle with EBL. We designed BLV-specific biotinylated probes to capture the provirus genome and enrich libraries for next-generation sequencing. Validation showed high specificity and efficient enrichment of target sequence reads as well as identification of three BLV proviral integration sites on BLV persistently infected FLK-BLV cells as a positive control. We successfully detected a single BLV proviral integration site on chromosome 19 of BLSC-KU1 and chromosome 9 of BLSC-KU17, which were confirmed by standard PCR and Sanger sequencing. Further, a defective provirus in BLSC-KU1 and complete BLV proviral sequence in BLSC-KU17 were confirmed using long PCR and sequencing. This is the first study to provide comprehensive information on BLV proviral structure and viral integration in BLSC-KU1 and BLSC-KU17. Moreover, the proposed method can facilitate understanding of the detailed mechanisms underlying BLV-induced leukemogenesis and may be used as an innovative tool to screen BLV-infected cattle at risk at an earlier stage than those that have already developed lymphoma. Full article

HIV infection is not curable with current antiretroviral therapy (ART) because a small fraction of CD4+ T cells infected prior to ART initiation persists. Understanding the nature of this latent reservoir and how it is created is essential to development of potentially curative strategies. The discovery that a large fraction of the persistently infected cells in individuals on suppressive ART are members of large clones greatly changed our view of the reservoir and how it arises. Rather than being the products of infection of resting cells, as was once thought, HIV persistence is largely or entirely a consequence of infection of cells that are either expanding or are destined to expand, primarily due to antigen-driven activation. Although most of the clones carry defective proviruses, some carry intact infectious proviruses; these clones comprise the majority of the reservoir. A large majority of both the defective and the intact infectious proviruses in clones of infected cells are transcriptionally silent; however, a small fraction expresses a few copies of unspliced HIV RNA. A much smaller fraction is responsible for production of low levels of infectious virus, which can rekindle infection when ART is stopped. Further understanding of the reservoir will be needed to clarify the mechanism(s) by which provirus expression is controlled in the clones of cells that constitute the reservoir. Full article

Combination antiretroviral therapy (cART) controls but does not eradicate HIV infection; HIV persistence is the principal obstacle to curing infections. The proportion of defective proviruses increases during cART, but the dynamics of this process are not well understood, and a quantitative analysis of how the proviral landscape is reshaped after cART is initiated is critical to understanding how HIV persists. Here, we studied longitudinal samples from HIV infected individuals undergoing long term cART using multiplexed Droplet Digital PCR (ddPCR) approaches to quantify the proportion of deleted proviruses in lymphocytes. In most individuals undergoing cART, HIV proviruses that contain gag are lost more quickly than those that lack gag. Increases in the fraction of gag-deleted proviruses occurred only after 1–2 years of therapy, suggesting that the immune system, and/or toxicity of viral re-activation helps to gradually shape the proviral landscape. After 10–15 years on therapy, there were as many as 3.5–5 times more proviruses in which gag was deleted or highly defective than those containing intact gag. We developed a provirus-specific ddPCR approach to quantify individual clones. Investigation of a clone of cells containing a deleted HIV provirus integrated in the HORMAD2 gene revealed that the cells underwent a massive expansion shortly after cART was initiated until the clone, which was primarily in effector memory cells, dominated the population of proviruses for over 6 years. The expansion of this HIV-infected clone had substantial effects on the overall proviral population. Full article

Jan Svoboda triggered investigations on non-defective avian sarcoma viruses. These viruses were a critical factor in the genetic understanding of retroviruses. They provided the single and unique access to the field and facilitated the discovery of the first oncogene src and of the cellular origin of retroviral oncogenes. They continue to be of importance as singularly effective expression vectors that have provided insights into the molecular functions of numerous oncogenes. Combined with the contributions to the validation of the provirus hypothesis, Jan Svoboda’s investigations of non-defective avian sarcoma viruses have shaped a large and important part of retrovirology. Full article

Porcine endogenous retroviruses (PERVs) represent a risk factor if porcine cells, tissues, or organs were to be transplanted into human recipients to alleviate the shortage of human transplants; a procedure called xenotransplantation. In contrast to human endogenous retroviruses (HERVs), which are mostly defective and not replication-competent, PERVs are released from normal pig cells and are infectious. PERV-A and PERV-B are polytropic viruses infecting cells of several species, among them humans; whereas PERV-C is an ecotropic virus infecting only pig cells. Virus infection was shown in co-culture experiments, but also in vivo, in the pig, leading to de novo integration of proviruses in certain organs. This was shown by measurement of the copy number per cell, finding different numbers in different organs. In addition, recombinations between PERV-A and PERV-C were observed and the recombinant PERV-A/C were found to be integrated in cells of different organs, but not in the germ line of the animals. Here, the evidence for such in vivo activities of PERVs, including expression as mRNA, protein and virus particles, de novo infection and recombination, will be summarised. These activities make screening of pigs for provirus number and PERV expression level difficult, especially when only blood or ear biopsies are available for analysis. Highly sensitive methods to measure the copy number and the expression level will be required when selecting pigs with low copy number and low expression of PERV as well as when inactivating PERVs using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease (CRISPR/Cas) technology. Full article