Experimental respiratory Marburg virus haemorrhagic fever infection in the common marmoset (Callithrix jacchus)

Marmosets as models of infectious diseases

Animal models of infectious disease often serve a crucial purpose in obtaining licensure of therapeutics and medical countermeasures, particularly in situations where human trials are not feasible, i.e., for those diseases that occur infrequently in the human population. The common marmoset (Callithrix jacchus), a Neotropical new-world (platyrrhines) non-human primate, has gained increasing attention as an animal model for a number of diseases given its small size, availability and evolutionary proximity to humans. This review aims to (i) discuss the pros and cons of the common marmoset as an animal model by providing a brief snapshot of how marmosets are currently utilized in biomedical research, (ii) summarize and evaluate relevant aspects of the marmoset immune system to the study of infectious diseases, (iii) provide a historical backdrop, outlining the significance of infectious diseases and the importance of developing reliable animal models to test novel therapeutics, and (iv) provide a summary of infectious diseases for which a marmoset model exists, followed by an in-depth discussion of the marmoset models of two studied bacterial infectious diseases (tularemia and melioidosis) and one viral infectious disease (viral hepatitis C).

Toxicological Evaluation of a Probiotic-Based Delivery System for P8 Protein as an Anti-Colorectal Cancer Drug

Purpose

This study aimed to toxicological evaluate a probiotics-based delivery system for p8 protein as an anti-colorectal cancer drug.

Introduction

Lactic acid bacteria (LAB) have been widely ingested for many years and are regarded as very safe. Recently, a Pediococcus pentosaceus SL4 (PP) strain that secretes the probiotic-derived anti-cancer protein P8 (PP-P8) has been developed as an anti-colorectal cancer (CRC) biologic by Cell Biotech. We initially identified a Lactobacillus rhamnosus (LR)-derived anti-cancer protein, P8, that suppresses CRC growth. We also showed that P8 penetrates specifically into CRC cells (DLD-1 cells) through endocytosis. We then confirmed the efficacy of PP-P8, showing that oral administration of this agent significantly decreased tumor mass (~42%) relative to controls in a mouse CRC xenograft model. In terms of molecular mechanism, PP-P8 induces cell-cycle arrest in G₂ phase through down-regulation of Cyclin B1 and Cdk1. In this study, we performed in vivo toxicology profiling to obtain evidence that PP-P8 is safe, with the goal of receiving approval for an investigational new drug application (IND).

Methods

Based on gene therapy guidelines of the Ministry of Food and Drug Safety (MFDS) of Korea, the potential undesirable effects of PP-P8 had to be investigated in intact small rodent or marmoset models prior to first-in-human (FIH) administration. The estimated doses of PP-P8 for FIH are 1.0×10¹⁰ – 1.0×10¹¹ CFU/person (60 kg). Therefore, to perform toxicological investigations in non-clinical animal models, we orally administered PP-P8 at doses of 3.375 × 10¹¹, 6.75 × 10¹¹, and 13.5×10¹¹ CFU/kg/day; thus the maximum dose was 800–8000-fold higher than the estimated dose for FIH.

Results

In our animal models, we observed no adverse effects of PP-P8 on clinicopathologic findings, relative organ weight, or tissue pathology. In addition, we observed no inflammation or ulceration during pathological necropsy.

Conclusion

These non-clinical toxicology studies could be used to furnish valuable data for the safety certification of PP-P8.

Marmosets: Welfare, Ethical Use, and IACUC/Regulatory Considerations

Use of marmosets in biomedical research has increased dramatically in recent years due, in large part, to their suitability for transgenic applications and utility as models for neuroscience investigations. This increased use includes the establishment of new colonies and involvement of people new to marmoset research. To facilitate the use of the marmoset as a research model, we provide an overview of issues surrounding the ethics and regulations associated with captive marmoset research, including discussion of the history of marmosets in research, current uses of marmosets, ethical considerations related to marmoset use, issues related to importation of animals, and recommendations for regulatory oversight of gene-edited marmosets. To understand the main concerns that oversight bodies have regarding captive biomedical research with marmosets, we developed a brief, 15-question survey that was then sent electronically to academic and biomedical research institutions worldwide that were believed to house colonies of marmosets intended for biomedical research. The survey included general questions regarding the individual respondent's colony, status of research use of the colony and institutional oversight of both the colony itself and the research use of the colony. We received completed surveys from a total of 18 institutions from North America, Europe, and Asia. Overall, there appeared to be no clear difference in regulatory oversight body concerns between countries/regions. One difference that we were able to appreciate was that while biomedical research with marmosets was noted to be either stable or decreasing in Europe, use was clearly increasing elsewhere.

Comparative Pathology and Pathogenesis of African Swine Fever Infection in Swine

African Swine Fever (ASF) is a viral disease that affects animals of the Suidae family, and soft ticks from the genus Ornithodoros can also be infected by the ASF virus (ASFV). The disease was first described in Africa at the beginning of the twentieth century as an acute disease characterized by high mortality and fatal hemorrhages. ASF has caused outbreaks in numerous countries and it continues to be devastating nowadays for the porcine sector in those countries affected, and a massive threat for those free of the disease. ASF can follow clinical courses from peracute to chronic in domestic pigs (Sus scrofa) depending on a variety of factors, including the immune status of the animals and the virulence of the ASFV strain. The key features of the pathogenesis of the disease in domestic swine are a) a severe lymphoid depletion including lymphopenia and a state of immunodeficiency, and b) hemorrhages. However, African wild swine like bushpigs (Potamochoerus larvatus), red river hogs (Potamochoerus porcus), and warthogs (Phacochoerus africanus) can be infected by ASFV showing no clinical signs of disease and acting as natural reservoir hosts. In this article we review the key features of the gross and microscopic pathology together with a description of the pathogenesis of ASFV infection in domestic pigs following the different clinical courses. The pathogenesis of ASF in wild and domestic swine is also described, what can provide important information for the design of control strategies, such as vaccines.

Marburg virus pathogenesis - differences and similarities in humans and animal models

Marburg virus (MARV) is a highly pathogenic virus associated with severe disease and mortality rates as high as 90%. Outbreaks of MARV are sporadic, deadly, and often characterized by a lack of resources and facilities to diagnose and treat patients. There are currently no approved vaccines or treatments, and the chaotic and infrequent nature of outbreaks, among other factors, makes testing new countermeasures during outbreaks ethically and logistically challenging. Without field efficacy studies, researchers must rely on animal models of MARV infection to assess the efficacy of vaccines and treatments, with the limitations being the accuracy of the animal model in recapitulating human pathogenesis. This review will compare various animal models to the available descriptions of human pathogenesis and aims to evaluate their effectiveness in modeling important aspects of Marburg virus disease.

Recent advances in marburgvirus research

Marburgviruses are closely related to ebolaviruses and cause a devastating disease in humans. In 2012, we published a comprehensive review of the first 45 years of research on marburgviruses and the disease they cause, ranging from molecular biology to ecology. Spurred in part by the deadly Ebola virus outbreak in West Africa in 2013-2016, research on all filoviruses has intensified. Not meant as an introduction to marburgviruses, this article instead provides a synopsis of recent progress in marburgvirus research with a particular focus on molecular biology, advances in animal modeling, and the use of Egyptian fruit bats in infection experiments.

Experimental Infections of the Common Marmoset (Callithrix jacchus)

Interest in the use of marmosets for experimental infectious disease has dramatically increased in the last decade. These animals are native to the Atlantic coastal forests in northeastern Brazil. The majority of experimental animals come from the National Primate Research Centers and other breeding facilities. They are advantageous because of their relative small size, weighting 350–400 g as adults, their life span is compact compared with other nonhuman primate (NHP), and they produce offspring by 3 years of age. They are free of Herpes B virus and, it is believed, to date, other dangerous human pathogens (Abbot et al., 2003) [1]. We describe here the experimental infections of marmosets to human pathogens. While it is always interesting to compare various NHPs with each other, the importance of an animal model is always in comparing its similarities to human infections.

Nonhuman Primate Models of Ebola Virus Disease

Ebola virus disease (EVD) in humans is associated with four ebolaviruses: Ebola virus (EBOV), Sudan virus (SUDV), Bundibugyo virus (BDBV), and Taï Forest virus. To date, no documented cases of human disease have been associated with Reston virus. Here, we describe the nonhuman primate (NHP) models that currently serve as gold standards for testing ebolavirus vaccines and therapeutic agents and elucidating underlying mechanisms of pathogenesis. Although multiple models have been explored over the past 50 years, the predominance of published work has been performed in macaque models. This chapter will focus on the most commonly used models.

A hamster model for Marburg virus infection accurately recapitulates Marburg hemorrhagic fever

Marburg virus (MARV), a close relative of Ebola virus, is the causative agent of a severe human disease known as Marburg hemorrhagic fever (MHF). No licensed vaccine or therapeutic exists to treat MHF, and MARV is therefore classified as a Tier 1 select agent and a category A bioterrorism agent. In order to develop countermeasures against this severe disease, animal models that accurately recapitulate human disease are required. Here we describe the development of a novel, uniformly lethal Syrian golden hamster model of MHF using a hamster-adapted MARV variant Angola. Remarkably, this model displayed almost all of the clinical features of MHF seen in humans and non-human primates, including coagulation abnormalities, hemorrhagic manifestations, petechial rash, and a severely dysregulated immune response. This MHF hamster model represents a powerful tool for further dissecting MARV pathogenesis and accelerating the development of effective medical countermeasures against human MHF.

Neglected filoviruses

Eight viruses are currently assigned to the family Filoviridae Marburg virus, Sudan virus and, in particular, Ebola virus have received the most attention both by researchers and the public from 1967 to 2013. During this period, natural human filovirus disease outbreaks occurred sporadically in Equatorial Africa and, despite high case-fatality rates, never included more than several dozen to a few hundred infections per outbreak. Research emphasis shifted almost exclusively to Ebola virus in 2014, when this virus was identified as the cause of an outbreak that has thus far involved more than 28 646 people and caused more than 11 323 deaths in Western Africa. Consequently, major efforts are currently underway to develop licensed medical countermeasures against Ebola virus infection. However, the ecology of and mechanisms behind Ebola virus emergence are as little understood as they are for all other filoviruses. Consequently, the possibility of the future occurrence of a large disease outbreak caused by other less characterized filoviruses (i.e. Bundibugyo virus, Lloviu virus, Ravn virus, Reston virus and Taï Forest virus) is impossible to rule out. Yet, for many of these viruses, not even rudimentary research tools are available, let alone medical countermeasures. This review summarizes the current knowledge on these less well-characterized filoviruses.

Experimental Respiratory Infection of Marmosets (Callithrix jacchus) With Ebola Virus Kikwit

Ebola virus (EBOV) causes a highly infectious and lethal hemorrhagic fever in primates with high fatality rates during outbreaks and EBOV may be exploited as a potential biothreat pathogen. There is therefore a need to develop and license appropriate medical countermeasures against this virus. To determine whether the common marmoset (Callithrix jacchus) would be an appropriate model to assess vaccines or therapies against EBOV disease (EVD), initial susceptibility, lethality and pathogenesis studies were performed. Low doses of EBOV-Kikwit, between 4 and 27 times the 50% tissue culture infectious dose, were sufficient to cause a lethal, reproducible infection. Animals became febrile between days 5 and 6, maintaining a high fever before succumbing to EVD between 6 and 8 days after challenge. Typical signs of EVD were observed. Pathogenesis studies revealed that virus was isolated from the lungs of animals beginning on day 3 after challenge and from the liver, spleen and blood beginning on day 5. The most striking features were observed in animals that succumbed to infection, including high viral titers in all organs, increased levels of liver function enzymes and blood clotting times, decreased levels of platelets, multifocal moderate to severe hepatitis, and perivascular edema.

Tissue and cellular tropism, pathology and pathogenesis of Ebola and Marburg viruses

Ebola viruses and Marburg viruses include some of the most virulent and fatal pathogens known to humans. These viruses cause severe haemorrhagic fevers, with case fatality rates in the range 25-90%. The diagnosis of filovirus using formalin-fixed tissues from fatal cases poses a significant challenge. The most characteristic histopathological findings are seen in the liver; however, the findings overlap with many other viral and non-viral haemorrhagic diseases. The need to distinguish filovirus infections from other haemorrhagic fevers, particularly in areas with multiple endemic viral haemorrhagic agents, is of paramount importance. In this review we discuss the current state of knowledge of filovirus infections and their pathogenesis, including histopathological findings, epidemiology, modes of transmission and filovirus entry and spread within host organisms. The pathogenesis of filovirus infections is complex and involves activation of the mononuclear phagocytic system, with release of pro-inflammatory cytokines, chemokines and growth factors, endothelial dysfunction, alterations of the innate and adaptive immune systems, direct organ and endothelial damage from unrestricted viral replication late in infection, and coagulopathy. Although our understanding of the pathogenesis of filovirus infections has rapidly increased in the past few years, many questions remain unanswered.

Comparative experimental subcutaneous glanders and melioidosis in the common marmoset (Callithrix jacchus)

Glanders and melioidosis are caused by two distinct Burkholderia species and have generally been considered to have similar disease progression. While both of these pathogens are HHS/CDC Tier 1 agents, natural infection with both these pathogens is primarily through skin inoculation. The common marmoset (Callithrix jacchus) was used to compare disease following experimental subcutaneous challenge. Acute, lethal disease was observed in marmosets following challenge with between 26 and 1.2 × 10(8) cfu Burkholderia pseudomallei within 22-85 h. The reproducibility and progression of the disease were assessed following a challenge of 1 × 10(2) cfu of B. pseudomallei. Melioidosis was characterised by high levels of bacteraemia, focal microgranuloma progressing to non-necrotic multifocal solid lesions in the livers and spleens and multi-organ failure. Lethal disease was observed in 93% of animals challenged with Burkholderia mallei, occurring between 5 and 10.6 days. Following challenge with 1 × 10(2) cfu of B. mallei, glanders was characterised with lymphatic spread of the bacteria and non-necrotic, multifocal solid lesions progressing to a multifocal lesion with severe necrosis and pneumonia. The experimental results confirmed that the disease pathology and presentation is strikingly different between the two pathogens. The marmoset provides a model of the human syndrome for both diseases facilitating the development of medical countermeasures.

Exploring the innate immunological response of an alternative nonhuman primate model of infectious disease; the common marmoset

The common marmoset (Callithrix jacchus) is increasingly being utilised as a nonhuman primate model for human disease, ranging from autoimmune to infectious disease. In order to fully exploit these models, meaningful comparison to the human host response is necessary. Commercially available reagents, primarily targeted to human cells, were utilised to assess the phenotype and activation status of key immune cell types and cytokines in naive and infected animals. Single cell suspensions of blood, spleen, and lung were examined. Generally, the phenotype of cells was comparable between humans and marmosets, with approximately 63% of all lymphocytes in the blood of marmosets being T cells, 25% B-cells, and 12% NK cells. The percentage of neutrophils in marmoset blood were more similar to human values than mouse values. Comparison of the activation status of cells following experimental systemic or inhalational infection exhibited different trends in different tissues, most obvious in cell types active in the innate immune response. This work significantly enhances the ability to understand the immune response in these animals and fortifies their use as models of infectious disease.

Potential for introduction of bat-borne zoonotic viruses into the EU: a review

Bat-borne viruses can pose a serious threat to human health, with examples including Nipah virus (NiV) in Bangladesh and Malaysia, and Marburg virus (MARV) in Africa. To date, significant human outbreaks of such viruses have not been reported in the European Union (EU). However, EU countries have strong historical links with many of the countries where NiV and MARV are present and a corresponding high volume of commercial trade and human travel, which poses a potential risk of introduction of these viruses into the EU. In assessing the risks of introduction of these bat-borne zoonotic viruses to the EU, it is important to consider the location and range of bat species known to be susceptible to infection, together with the virus prevalence, seasonality of viral pulses, duration of infection and titre of virus in different bat tissues. In this paper, we review the current scientific knowledge of all these factors, in relation to the introduction of NiV and MARV into the EU.

Development of novel mechanisms for housing, handling, and remote monitoring of common marmosets at animal biosafety level 3

The use of common marmosets as an alternative non-human primate model for infectious disease research using BSL-3 viruses such as Rift Valley fever virus (RVFV) presents unique challenges with respect to housing, handling, and safety. Subject matter experts from veterinary care, animal husbandry, biosafety, engineering, and research were consulted to design a pilot experiment using marmosets infected with RVFV. This paper reviews the caging, handling, and safety-related adaptations and modifications that were required to humanely utilize marmosets as a model for high-hazard BSL-3 viral diseases.

A novel nonhuman primate model for influenza transmission

Studies of influenza transmission are necessary to predict the pandemic potential of emerging influenza viruses. Currently, both ferrets and guinea pigs are used in such studies, but these species are distantly related to humans. Nonhuman primates (NHP) share a close phylogenetic relationship with humans and may provide an enhanced means to model the virological and immunological events in influenza virus transmission. Here, for the first time, it was demonstrated that a human influenza virus isolate can productively infect and be transmitted between common marmosets (Callithrix jacchus), a New World monkey species. We inoculated four marmosets with the 2009 pandemic virus A/California/07/2009 (H1N1pdm) and housed each together with a naïve cage mate. We collected bronchoalveolar lavage and nasal wash samples from all animals at regular intervals for three weeks post-inoculation to track virus replication and sequence evolution. The unadapted 2009 H1N1pdm virus replicated to high titers in all four index animals by 1 day post-infection. Infected animals seroconverted and presented human-like symptoms including sneezing, nasal discharge, labored breathing, and lung damage. Transmission occurred in one cohabitating pair. Deep sequencing detected relatively few genetic changes in H1N1pdm viruses replicating in any infected animal. Together our data suggest that human H1N1pdm viruses require little adaptation to replicate and cause disease in marmosets, and that these viruses can be transmitted between animals. Marmosets may therefore be a viable model for studying influenza virus transmission.