Simian Foamy Viruses in Central and South America: A New World of Discovery

Clinical and Translational Landscape of Viral Gene Therapies

Gene therapies hold significant promise for treating previously incurable diseases. A number of gene therapies have already been approved for clinical use. Currently, gene therapies are mostly limited to the use of adeno-associated viruses and the herpes virus. Viral vectors, particularly those derived from human viruses, play a critical role in this therapeutic approach due to their ability to efficiently deliver genetic material to target cells. Despite their advantages, such as stable gene expression and efficient transduction, viral vectors face numerous limitations that hinder their broad application. These limitations include small cloning capacities, immune and inflammatory responses, and risks of insertional mutagenesis. This review explores the current landscape of viral vectors used in gene therapy, discussing the different types of DNA- and RNA-based viral vectors, their characteristics, limitations, and current medical and potential clinical applications. The review also highlights strategies to overcome existing challenges, including optimizing vector design, improving safety profiles, and enhancing transgene expression both using molecular techniques and nanotechnologies, as well as by approved drug formulations.

Diversity and prevalence of zoonotic infections at the animal-human interface of primate trafficking in Peru

Wildlife trafficking creates favorable scenarios for intra- and inter-specific interactions that can lead to parasite spread and disease emergence. Among the fauna affected by this activity, primates are relevant due to their potential to acquire and share zoonoses - infections caused by parasites that can spread between humans and other animals. Though it is known that most primate parasites can affect multiple hosts and that many are zoonotic, comparative studies across different contexts for animal-human interactions are scarce. We conducted a multi-parasite screening targeting the detection of zoonotic infections in wild-caught monkeys in nine Peruvian cities across three contexts: captivity (zoos and rescue centers, n = 187); pet (households, n = 69); and trade (trafficked or recently confiscated, n = 132). We detected 32 parasite taxa including mycobacteria, simian foamyvirus, bacteria, helminths, and protozoa. Monkeys in the trade context had the highest prevalence of hemoparasites (including Plasmodium malariae/brasilianum, Trypanosoma cruzi, and microfilaria) and enteric helminths and protozoa were less common in pet monkeys. However, parasite communities showed overall low variation between the three contexts. Parasite richness (PR) was best explained by host genus and the city where the animal was sampled. Squirrel (genus Saimiri) and wooly (genus Lagothrix) monkeys had the highest PR, which was ~2.2 times the PR found in tufted capuchins (genus Sapajus) and tamarins (genus Saguinus/Leontocebus) in a multivariable model adjusted for context, sex, and age. Our findings illustrate that the threats of wildlife trafficking to One Health encompass exposure to multiple zoonotic parasites well-known to cause disease in humans, monkeys, and other species. We demonstrate these threats continue beyond the markets where wildlife is initially sold; monkeys trafficked for the pet market remain a reservoir for and contribute to the translocation of zoonotic parasites to households and other captive facilities where contact with humans is frequent. Our results have practical applications for the healthcare of rescued monkeys and call for urgent action against wildlife trafficking and ownership of monkeys as pets.

Occurrence of Equine Foamy Virus Infection in Horses from Poland

Equine foamy virus (EFVeca) is a foamy virus of non-primate origin and among the least-studied members of this retroviral subfamily. By sequence comparison, EFVeca shows the highest similarity to bovine foamy virus. In contrast to simian, bovine or feline foamy viruses, knowledge about the epidemiology of EFVeca is still limited. Since preliminary studies suggested EFVeca infections among horses in Poland, we aimed to expand the diagnostics of EFVeca infections by developing specific diagnostic tools and apply them to investigate its prevalence. An ELISA test based on recombinant EFVeca Gag protein was developed for serological investigation, while semi-nested PCR for the detection of EFVeca DNA was established. 248 DNA and serum samples from purebred horses, livestock and saddle horses, Hucul horses and semi-feral Polish primitive horses were analyzed in this study. ELISA was standardized, and cut off value, sensitivity and specificity of the test were calculated using Receiver Operating Characteristic and Bayesian estimation. Based on the calculated cut off, 135 horses were seropositive to EFVeca Gag protein, while EFVeca proviral DNA was detected in 85 animals. The rate of infected individuals varied among the horse groups studied; this is the first report confirming the existence of EFVeca infections in horses from Poland using virus-specific tools.

Viral Safety Issues in the Production and Manufacturing of Human Immunoglobulin Preparations from Equine Plasma/Serum

The current Russian and foreign pharmacopoeias either do not provide any information about existing types of viral diseases in horses or do not present it in full. Data of modern domestic and foreign literature was used to prepare the most complete list of viruses that cause equine diseases including 36 infectious agents, 25 of which are pathogenic for humans, 13 of the 25 of which are widespread throughout Russia. Information is provided on the magnitudes of the disease incubation periods (which are most often within one month), the external clinical signs of these diseases (which can also be asymptomatic), and the maximum possible concentrations of viruses in the blood of horses with these diseases (which can reach 8 log conventional units/mL of blood). This information is offered for use in critical production stages of heterologous immunoglobulin drugs for medical use to assure viral safety.

Plasma antibodies from humans infected with zoonotic simian foamy virus do not inhibit cell-to-cell transmission of the virus despite binding to the surface of infected cells

Zoonotic simian foamy viruses (SFV) establish lifelong infection in their human hosts. Despite repeated transmission of SFV from nonhuman primates to humans, neither transmission between human hosts nor severe clinical manifestations have been reported. We aim to study the immune responses elicited by chronic infection with this retrovirus and previously reported that SFV-infected individuals generate potent neutralizing antibodies that block cell infection by viral particles. Here, we assessed whether human plasma antibodies block SFV cell-to-cell transmission and present the first description of cell-to-cell spreading of zoonotic gorilla SFV. We set-up a microtitration assay to quantify the ability of plasma samples from 20 Central African individuals infected with gorilla SFV and 9 uninfected controls to block cell-associated transmission of zoonotic gorilla SFV strains. We used flow-based cell cytometry and fluorescence microscopy to study envelope protein (Env) localization and the capacity of plasma antibodies to bind to infected cells. We visualized the cell-to-cell spread of SFV by real-time live imaging of a GFP-expressing prototype foamy virus (CI-PFV) strain. None of the samples neutralized cell-associated SFV infection, despite the inhibition of cell-free virus. We detected gorilla SFV Env in the perinuclear region, cytoplasmic vesicles and at the cell surface. We found that plasma antibodies bind to Env located at the surface of cells infected with primary gorilla SFV strains. Extracellular labeling of SFV proteins by human plasma samples showed patchy staining at the base of the cell and dense continuous staining at the cell apex, as well as staining in the intercellular connections that formed when previously connected cells separated from each other. In conclusion, SFV-specific antibodies from infected humans do not block cell-to-cell transmission, at least in vitro, despite their capacity to bind to the surface of infected cells.

Trial registration: Clinical trial registration: www.clinicaltrials.gov, https://clinicaltrials.gov/ct2/show/NCT03225794/.

Foamy viruses are the oldest known retroviruses and have been mostly described to be nonpathogenic in their natural animal hosts. Simian foamy viruses (SFVs) can be transmitted to humans, in whom they establish persistent infection, as have the simian viruses that led to the emergence of two major human pathogens, human immunodeficiency virus type 1 (HIV-1) and human T lymphotropic virus type 1 (HTLV-1). Such cross-species transmission of SFV is ongoing in many parts of the world where humans have contact with nonhuman primates. We previously showed high titers of neutralizing antibodies in the plasma of most SFV-infected individuals. These antiviral antibodies can inhibit cell-free virus entry. However, SFV efficiently spread from one cell to another. Here, we demonstrate that plasma antibodies do not block such cell-to-cell transmission, despite their capacity to bind to the surface of infected cells. In addition, we document for the first time the cell-to-cell spread of primary zoonotic gorilla SFV.

Transmission of infectious viruses in the natural setting at human-animal interface

Most viral pathogens causing epidemics and pandemics are zoonotic, emerging from wildlife reservoirs like SARS CoV2 causing the global Covid-19 pandemic, although animal origin of this virus remains a mystery. Cross-species transmission of pathogens from animals to humans is known as zoonosis. However, pathogens are also transmitted from humans to animals in regions where there is a close interaction between animals and humans by 'reverse transmission' (anthroponosis). Molecular evidence for the transmission of two zoonotic RNA viruses at the human-monkey interface in Rajasthan forests is presented here: a) the apathogenic Simian Foamy Viruses (SFV), and b): Influenza A viruses (IAV)-like virus, etiologic agent for human flu infecting wild Indian rhesus monkeys inhabiting Rajasthan forests. The data provide critical information on ecology and evolution of viruses of Public Health relevance. During replication, viral genomes mutate along the transmission route to adapt to the new hosts, generating new variants that are likely to have properties different from the founder viruses. Wild Indian monkeys are under-sampled for monitoring infectious diseases mainly because of the difficulties with sample collection. Monkeys are perceived as religious icons by the Hindus in India. It is extremely difficult to obtain permission from the Forest and Wildlife Department government authorities to collect wild simian blood samples for surveillance of infectious diseases caused by viral pathogens. Reducing animal-human contact and affordable vaccination are two relevant anti-viral strategies to counteract the spread of infectious zoonotic pathogens. Genbank Accession numbers: Indian SFVmac: ADN94420, IAV like virus: MZ298601.

Foamy Viruses, Bet, and APOBEC3 Restriction

Non-human primates (NHP) are an important source of viruses that can spillover to humans and, after adaptation, spread through the host population. Whereas HIV-1 and HTLV-1 emerged as retroviral pathogens in humans, a unique class of retroviruses called foamy viruses (FV) with zoonotic potential are occasionally detected in bushmeat hunters or zookeepers. Various FVs are endemic in numerous mammalian natural hosts, such as primates, felines, bovines, and equines, and other animals, but not in humans. They are apathogenic, and significant differences exist between the viral life cycles of FV and other retroviruses. Importantly, FVs replicate in the presence of many well-defined retroviral restriction factors such as TRIM5α, BST2 (Tetherin), MX2, and APOBEC3 (A3). While the interaction of A3s with HIV-1 is well studied, the escape mechanisms of FVs from restriction by A3 is much less explored. Here we review the current knowledge of FV biology, host restriction factors, and FV-host interactions with an emphasis on the consequences of FV regulatory protein Bet binding to A3s and outline crucial open questions for future studies.