The broad-spectrum antiviral favipiravir protects guinea pigs from lethal Lassa virus infection post-disease onset

With up to 500,000 infections annually, Lassa virus (LASV), the cause of Lassa fever, is one of the most prevalent etiological agents of viral hemorrhagic fever (VHF) in humans. LASV is endemic in several West African countries with sporadic cases and prolonged outbreaks observed most commonly in Sierra Leone, Liberia, Guinea and Nigeria. Additionally several cases of Lassa fever have been imported into North America, Europe and Asia making LASV a global threat to public health. Despite this, currently no approved therapeutic or vaccine exists to treat or prevent LASV infections. Here, using a passaged strain of LASV that is uniformly lethal in Hartley guinea pigs, we demonstrate that favipiravir, a broad-spectrum antiviral agent and leading treatment option for influenza, has potent activity against LASV infection. In this model, once daily treatment with favipiravir significantly reduced viral titers in tissue samples and reduced mortality rates when compared with animals receiving vehicle-only or ribavirin, the current standard of care for Lassa fever. Favipiravir remained highly effective against lethal LASV infection when treatments were initiated nine days post-infection, a time when animals were demonstrating advanced signs of disease. These results support the further preclinical evaluation of favipiravir for Lassa fever and other VHFs

UK B.1.1.7 variant exhibits increased respiratory replication and shedding in nonhuman primates.

The continuing emergence of SARS-CoV-2 variants calls for regular assessment to identify differences in viral replication, shedding and associated disease. In this study, African green monkeys were infected intranasally with either a contemporary D614G or the UK B.1.1.7 variant. Both variants caused mild respiratory disease with no significant differences in clinical presentation. Significantly higher levels of viral RNA and infectious virus were found in upper and lower respiratory tract samples and tissues from B.1.1.7 infected animals. Interestingly, D614G infected animals showed significantly higher levels of viral RNA and infectious virus in rectal swabs and gastrointestinal tract tissues. Our results indicate that B.1.1.7 infection in African green monkeys is associated with increased respiratory replication and shedding but no disease enhancement similar to human B.1.1.7 cases. ONE-SENTENCE SUMMARY: UK B.1.1.7 infection of African green monkeys exhibits increased respiratory replication and shedding but no disease enhancement

Comparative Pathogenesis of Three Human and Zoonotic SARS-CoV Strains in Cynomolgus Macaques

The severe acute respiratory syndrome (SARS) epidemic was characterized by increased pathogenicity in the elderly due to an early exacerbated innate host response. SARS-CoV is a zoonotic pathogen that entered the human population through an intermediate host like the palm civet. To prevent future introductions of zoonotic SARS-CoV strains and subsequent transmission into the human population, heterologous disease models are needed to test the efficacy of vaccines and therapeutics against both late human and zoonotic isolates. Here we show that both human and zoonotic SARS-CoV strains can infect cynomolgus macaques and resulted in radiological as well as histopathological changes similar to those seen in mild human cases. Viral replication was higher in animals infected with a late human phase isolate compared to a zoonotic isolate. While there were significant differences in the number of host genes differentially regulated during the host responses between the three SARS-CoV strains, the top pathways and functions were similar and only apparent early during infection with the majority of genes associated with interferon signaling pathways. This study characterizes critical disease models in the evaluation and licensure of therapeutic strategies against SARS-CoV for human use

Noise Cancellation: Viral Fine Tuning of the Cellular Environment for Its Own Genome Replication

Productive replication of DNA viruses elicits host cell DNA damage responses, which cause both beneficial and detrimental effects on viral replication. In response to the viral productive replication, host cells attempt to attenuate the S-phase cyclin-dependent kinase (CDK) activities to inhibit viral replication. However, accumulating evidence regarding interactions between viral factors and cellular signaling molecules indicate that viruses utilize them and selectively block the downstream signaling pathways that lead to attenuation of the high S-phase CDK activities required for viral replication. In this review, we describe the sophisticated strategy of Epstein-Barr virus to cancel such “noisy” host defense signals in order to hijack the cellular environment

HtrA2/Omi Terminates Cytomegalovirus Infection and Is Controlled by the Viral Mitochondrial Inhibitor of Apoptosis (vMIA)

Viruses encode suppressors of cell death to block intrinsic and extrinsic host-initiated death pathways that reduce viral yield as well as control the termination of infection. Cytomegalovirus (CMV) infection terminates by a caspase-independent cell fragmentation process after an extended period of continuous virus production. The viral mitochondria-localized inhibitor of apoptosis (vMIA; a product of the UL37x1 gene) controls this fragmentation process. UL37x1 mutant virus-infected cells fragment three to four days earlier than cells infected with wt virus. Here, we demonstrate that infected cell death is dependent on serine proteases. We identify mitochondrial serine protease HtrA2/Omi as the initiator of this caspase-independent death pathway. Infected fibroblasts develop susceptibility to death as levels of mitochondria-resident HtrA2/Omi protease increase. Cell death is suppressed by the serine protease inhibitor TLCK as well as by the HtrA2-specific inhibitor UCF-101. Experimental overexpression of HtrA2/Omi, but not a catalytic site mutant of the enzyme, sensitizes infected cells to death that can be blocked by vMIA or protease inhibitors. Uninfected cells are completely resistant to HtrA2/Omi induced death. Thus, in addition to suppression of apoptosis and autophagy, vMIA naturally controls a novel serine protease-dependent CMV-infected cell-specific programmed cell death (cmvPCD) pathway that terminates the CMV replication cycle

Establishment of a Genetically Confirmed Breeding Colony of Mastomys natalensis from Wild-Caught Founders from West Africa

Mastomys natalensis are a ubiquitous and often dominant rodent across sub-Saharan Africa. Importantly, they are a natural reservoir for microbial pathogens including Lassa virus (LASV), the etiological agent of Lassa fever in humans. Lassa-infected rodents have been documented across West Africa and coincide with regions where annual outbreaks occur. Zoonotic transmission to humans most often occurs directly from infected rodents. Little is known about LASV infection kinetics and transmissibility in M.natalensis, primarily due to available animals. Here, we describe the establishment of a laboratory breeding colony of genetically confirmed M.natalensis from wild-captured rodents. This colony will provide a convenient source of animals to study LASV and other emerging pathogens that utilize M. natalensis in their enzootic lifecycles

Vaccine Protection against Multidrug-Resistant Klebsiella pneumoniae in a Nonhuman Primate Model of Severe Lower Respiratory Tract Infection

Multidrug-resistant bacteria continue to be a major problem worldwide, especially among individuals with significant comorbidities and other risk factors for infection. K. pneumoniae is among the leading causes of health care-associated infections, and the organism is often resistant to multiple classes of antibiotics. A carbapenem-resistant K. pneumoniae strain known as multilocus sequence type 258 (ST258) is the predominant carbapenem-resistant Enterobacteriaceae in the health care setting in the United States. Infections caused by ST258 are often difficult to treat and new prophylactic measures and therapeutic approaches are needed. To that end, we developed a lower respiratory tract infection model in cynomolgus macaques in which to test the ability of ST258 CPS to protect against severe ST258 infection.Klebsiella pneumoniae is a human gut communal organism and notorious opportunistic pathogen. The relative high burden of asymptomatic colonization by K. pneumoniae is often compounded by multidrug resistance—a potential problem for individuals with significant comorbidities or other risk factors for infection. A carbapenem-resistant K. pneumoniae strain classified as multilocus sequence type 258 (ST258) is widespread in the United States and is usually multidrug resistant. Thus, treatment of ST258 infections is often difficult. Inasmuch as new preventive and/or therapeutic measures are needed for treatment of such infections, we developed an ST258 pneumonia model in cynomolgus macaques and tested the ability of an ST258 capsule polysaccharide type 2 (CPS2) vaccine to moderate disease severity. Compared with sham-vaccinated animals, those vaccinated with ST258 CPS2 had significantly less disease as assessed by radiography 24 h after intrabronchial installation of 108 CFU of ST258. All macaques vaccinated with CPS2 ultimately developed ST258-specific antibodies that significantly enhanced serum bactericidal activity and killing of ST258 by macaque neutrophils ex vivo. Consistent with a protective immune response to CPS2, transcripts encoding inflammatory mediators were increased in infected lung tissues obtained from CPS-vaccinated animals compared with control, sham-vaccinated macaques. Taken together, our data provide support for the idea that vaccination with ST258 CPS can be used to prevent or moderate infections caused by ST258. As with studies performed decades earlier, we propose that this prime-boost vaccination approach can be extended to include multiple capsule types

Isolation and genome sequencing of cytomegaloviruses from Natal multimammate mice (Mastomys natalensis)

Distinct cytomegaloviruses (CMVs) are widely distributed across their mammalian hosts in a highly host species-restricted pattern. To date, evidence demonstrating this has been limited largely to PCR-based approaches targeting small, conserved genomic regions, and only a few complete genomes of isolated viruses representing distinct CMV species have been sequenced. We have now combined direct isolation of infectious viruses from tissues with complete genome sequencing to provide a view of CMV diversity in a wild animal population. We targeted Natal multimammate mice (Mastomys natalensis), which are common in sub-Saharan Africa, are known to carry a variety of zoonotic pathogens, and are regarded as the primary source of Lassa virus (LASV) spillover into humans. Using transformed epithelial cells prepared from M. natalensis kidneys, we isolated CMVs from the salivary gland tissue of 14 of 37 (36 %) animals from a field study site in Mali. Genome sequencing showed that these primary isolates represent three different M. natalensis CMVs (MnatCMVs: MnatCMV1, MnatCMV2 and MnatCMV3), with some animals carrying multiple MnatCMVs or multiple strains of a single MnatCMV presumably as a result of coinfection or superinfection. Including primary isolates and plaque-purified isolates, we sequenced and annotated the genomes of two MnatCMV1 strains (derived from sequencing 14 viruses), six MnatCMV2 strains (25 viruses) and ten MnatCMV3 strains (21 viruses), totalling 18 MnatCMV strains isolated as 60 infectious viruses. Phylogenetic analysis showed that these MnatCMVs group with other murid viruses in the genus Muromegalovirus (subfamily Betaherpesvirinae, family Orthoherpesviridae), and that MnatCMV1 and MnatCMV2 are more closely related to each other than to MnatCMV3. The availability of MnatCMV isolates and the characterization of their genomes will serve as the prelude to the generation of a MnatCMV-based vaccine to target LASV in the M. natalensis reservoir.</jats:p