Infection with Asian-lineage Zika virus (ZIKV) has been associated with Guillain–Barré syndrome and fetal abnormalities, but the underlying mechanisms remain poorly understood. Animal models of infection are thus urgently needed. Here we show that rhesus macaques are susceptible to infection by an Asian-lineage ZIKV closely related to strains currently circulating in the Americas. Following subcutaneous inoculation, ZIKV RNA is detected in plasma 1 day post infection (d.p.i.) in all animals (N=8, including 2 pregnant animals), and is also present in saliva, urine and cerebrospinal fluid. Non-pregnant and pregnant animals remain viremic for 21 days and for up to at least 57 days, respectively. Neutralizing antibodies are detected by 21 d.p.i. Rechallenge 10 weeks after the initial challenge results in no detectable virus replication, indicating protective immunity against homologous strains. Therefore, Asian-lineage ZIKV infection of rhesus macaques provides a relevant animal model for studying pathogenesis and evaluating potential interventions against human infection, including during pregnancy.

Within the first three weeks of human immunodeficiency virus (HIV) infection, virus replication peaks in peripheral blood. Despite the critical, causal role of virus replication in determining transmissibility and kinetics of progression to acquired immune deficiency syndrome (AIDS), there is limited understanding of the conditions required to transform the small localized transmitted founder virus population into a large and heterogeneous systemic infection. Here we show that during the hyperacute “pre-peak” phase of simian immunodeficiency virus (SIV) infection in macaques, high levels of microbial DNA transiently translocate into peripheral blood. This, heretofore unappreciated, hyperacute-phase microbial translocation was accompanied by sustained reduction of lipopolysaccharide (LPS)-specific antibody titer, intestinal permeability, increased abundance of CD4+CCR5+ T cell targets of virus replication, and T cell activation. To test whether increasing gastrointestinal permeability to cause microbial translocation would amplify viremia, we treated two SIV-infected macaque ‘elite controllers’ with a short-course of dextran sulfate sodium (DSS)–stimulating a transient increase in microbial translocation and a prolonged recrudescent viremia. Altogether, our data implicates translocating microbes as amplifiers of immunodeficiency virus replication that effectively undermine the host’s capacity to contain infection.

Human Pegivirus (HPgV) – formerly known as GB virus C and hepatitis G virus – is a poorly characterized RNA virus that infects approximately one-sixth of the global human population and is transmitted frequently in the blood supply. Here, we create an animal model of HPgV infection by infecting macaque monkeys with a new simian pegivirus (SPgV) discovered in wild baboons. Using this model, we provide a high-resolution, longitudinal picture of SPgV viremia where the dose, route, and timing of infection are known. We detail the highly-variable acute-phase of SPgV infection, showing that the viral load trajectory early in infection is dependent upon the infecting dose, whereas the chronic-phase viremic set-point is not. We also show that SPgV has an extremely low propensity for accumulating sequence variation, with no consensus-level variants detected during the acute phase of infection and an average of only 1.5 variants generated per 100 infection days. Finally, we show that SPgV RNA is highly concentrated in only two tissues: spleen and bone marrow, with bone marrow likely producing the majority of virus detected in plasma. Together, these results reconcile several paradoxical observations from cross-sectional analyses of HPgV in humans and provide an animal model for studying pegivirus biology.

Understanding the relationship between invasive species density and ecological impact is a pressing topic in ecology, with implications for environmental management and policy. Although it is widely assumed that invasive species impact will increase with density, theory suggests interspecific competition may diminish at high densities due to increased intraspecific interactions. To test this theory, we experimentally examined intra- and interspecific interactions between a globally invasive fish, round goby (Neogobius melanostomus), and three native species at different round goby densities in a tributary of the Laurentian Great Lakes. Eighteen 2.25 m2 enclosures were stocked with native fish species at natural abundances, while round gobies were stocked at three different densities: 0 m−2, 2.7 m−2, and 10.7 m−2. After 52 days, native fish growth rate was significantly reduced in the low density goby treatment, while growth in the high density goby treatment mirrored the goby-free treatment for two of three native species. Invertebrate density and gut content weight of native fishes did not differ among treatments. Conversely, gut content weight and growth of round gobies were lower in the high goby density treatment, suggesting interactions between round gobies and native fishes are mediated by interference competition amongst gobies. Our experiment provides evidence that invasive species effects may diminish at high densities, possibly due to increased intraspecific interactions. This is consistent with some ecological theory, and cautions against the assumption that invasive species at moderate densities have low impact.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-014-2899-5) contains supplementary material, which is available to authorized users.

Few studies have evaluated the impact of the viral challenge route on protection against a heterologous simian immunodeficiency virus (SIV) challenge. We vaccinated seven macaques with a live attenuated SIV that differed from SIVmac239⌬nef by 24 amino acids, called m3KO⌬nef. All animals were protected from an intrarectal SIVmac239 challenge, whereas only four animals were protected from subsequent intravenous SIVmac239 challenge. These data suggest that immune responses elicited by vaccination with live attenuated SIV in an individual animal can confer protection from intrarectal challenge while remaining insufficient for protection from intravenous challenge. IMPORTANCEOur study is important because we show that vaccinated animals can be protected from a mucosal challenge with a heterologous SIV, but the same animals are not necessarily protected from intravenous challenge with the same virus. This is unique because in most studies, either vaccinated animals are challenged multiple times by the same route or only a single challenge is performed. An individually vaccinated animal is rarely challenged multiple times by different routes, so protection from different challenge routes cannot be measured in the same animal. Our data imply that vaccine-elicited responses in an individual animal may be insufficient for protection from intravenous challenge but may be suitable for protection from a mucosal challenge that better approximates human immunodeficiency virus (HIV) exposure.T wo important variables that can influence the apparent efficacy of preclinical human immunodeficiency virus (HIV)/ simian immunodeficiency virus (SIV) vaccines are the route of infection and the sequence of the challenge virus. For example, live attenuated SIV offers effective and consistent protection from intravenous challenge with a homologous virus but incomplete protection from intravenous challenge with a heterologous virus. This incomplete protection from heterologous challenge was observed after vaccination with several live attenuated SIV strains (e.g., SIVmac239⌬nef, SIVmac239⌬3, SIVsmE543⌬nef, and SIVmacC8), followed by challenge with different pathogenic SIV stocks (e.g., SIVsmE660, SHIV89.6p, SIV239/EnvE543, and SIVmac239) (1-6). Although those studies were each different, incomplete protection from an intravenous heterologous challenge was observed for both rhesus and cynomolgus macaques.The failure to offer complete protection from an intravenous challenge with a heterologous virus may be because some immune responses elicited by live attenuated SIV are localized to the mucosa and are not mobilized systemically at the time of challenge, making an intravenous challenge too stringent for testing of the efficacy of live attenuated SIV vaccines (7,8). Perhaps, immune responses elicited by a vaccine in an individual animal are sufficient to protect from mucosal challenge with a high dose of a heterologous virus, even if they cannot protect from intravenous challenge with the same virus.In this study, we wanted to test th...