Type I (IFN-α/β) and type III (IFN-λ) interferons (IFNs) exert shared antiviral activities through distinct receptors. However, their relative importance for antiviral protection of different organ systems against specific viruses remains to be fully explored. We used mouse strains deficient in type-specific IFN signaling, STAT1 and Rag2 to dissect distinct and overlapping contributions of type I and type III IFNs to protection against homologous murine (EW-RV strain) and heterologous (non-murine) simian (RRV strain) rotavirus infections in suckling mice. Experiments demonstrated that murine EW-RV is insensitive to the action of both types of IFNs, and that timely viral clearance depends upon adaptive immune responses. In contrast, both type I and type III IFNs can control replication of the heterologous simian RRV in the gastrointestinal (GI) tract, and they cooperate to limit extra-intestinal simian RRV replication. Surprisingly, intestinal epithelial cells were sensitive to both IFN types in neonatal mice, although their responsiveness to type I, but not type III IFNs, diminished in adult mice, revealing an unexpected age-dependent change in specific contribution of type I versus type III IFNs to antiviral defenses in the GI tract. Transcriptional analysis revealed that intestinal antiviral responses to RV are triggered through either type of IFN receptor, and are greatly diminished when receptors for both IFN types are lacking. These results also demonstrate a murine host-specific resistance to IFN-mediated antiviral effects by murine EW-RV, but the retention of host efficacy through the cooperative action by type I and type III IFNs in restricting heterologous simian RRV growth and systemic replication in suckling mice. Collectively, our findings revealed a well-orchestrated spatial and temporal tuning of innate antiviral responses in the intestinal tract where two types of IFNs through distinct patterns of their expression and distinct but overlapping sets of target cells coordinately regulate antiviral defenses against heterologous or homologous rotaviruses with substantially different effectiveness.

Immunizing infants against measles at the youngest age possible has the potential to reduce morbidity and mortality. The ability of infants at 6, 9, or 12 months to respond to measles and mumps vaccines was evaluated by measuring T cell proliferation, interferon-gamma production, and neutralizing antibody titers before and after vaccination. Infants in all age groups had equivalent cellular immune responses to measles or mumps viruses, with or without passive antibodies when immunized. In contrast, 6-month-old infants without passive antibodies had low geometric mean titers of antibody to measles or mumps viruses and low seroconversion rates. Geometric mean titers of antibody to measles virus increased if infants were revaccinated at 12 months. Six-month-old infants had limited humoral responses to paramyxovirus vaccines, whereas cellular immunity was equivalent to that of older infants. T cell responses can be established by immunization with these live attenuated virus vaccines during the first year, despite the presence of passive antibodies.

and the VA Palo Alto Health Care System, Palo Alto, California, USA Homologous rotaviruses (RV) are, in general, more virulent and replicate more efficiently than heterologous RV in the intestine of the homologous host. The genetic basis for RV host range restriction is not fully understood and is likely to be multigenic. In previous studies, RV genes encoding VP3, VP4, VP7, nonstructural protein 1 (NSP1), and NSP4 have all been implicated in strain-and host species-specific infection. These studies used different RV strains, variable measurements of host range, and different animal hosts, and no clear consensus on the host range restriction determinants emerged. We used a murine model to demonstrate that enteric replication of murine RV EW is 1,000-to 10,000-fold greater than that of a simian rotavirus (RRV) in suckling mice. Intestinal replication of a series of EW ؋ RRV reassortants was used to identify several RV genes that influenced RV replication in the intestine. The role of VP4 (encoded by gene 4) in enteric infection was strain specific. RRV VP4 reduced murine RV infectivity only slightly; however, a reassortant expressing VP4 from a bovine RV strain (UK) severely restricted intestinal replication in the suckling mice. The homologous murine EW NSP1 (encoded by gene 5) was necessary but not sufficient for promoting efficient enteric growth. Efficient enteric replication required a constellation of murine genes encoding VP3, NSP2, and NSP3 along with NSP1. Group A rotaviruses (RVs) are segmented double-stranded RNA viruses that replicate primarily in mature epithelial cells on the tips of the small intestinal villi (1). Rotavirus infection is ubiquitous among mammals; however, viral strains isolated from one host species tend to have diminished replication capacity and virulence in heterologous species. This host range restriction was the basis for two modified "Jennerian" RV vaccines, RotaShield and RotaTeq; animal rotaviruses that are naturally restricted for replication and virulence in humans were used as genetic backbones to produce these attenuated, live viral human vaccines. In the pentavalent RV vaccine Rotateq, for example, human rotavirus genes encoding VP7 of serotypes G 1, 2, 3, 4, and VP4 of serotype P1A (P[8]) were incorporated into bovine RV strain WC3. It was thought that the multivalent nature of this vaccine would induce neutralizing antibodies against the most common human RV serotypes but that it would be attenuated in susceptible infants because of host range restriction elements in its bovine (heterologous) RV backbone (2).Direct experimental evidence for host range restriction has been best demonstrated in the murine system, where all known heterologous RV strains replicate orders of magnitude less efficiently in suckling mice than do homologous murine strains (3, 4). On the other hand, experimental studies in gnotobiotic piglets have been interpreted to indicate that some human RV strains can be adapted to replicate very efficiently in piglets, although direct comparison to wild-t...

An entirely plasmid-based reverse genetics (RG) system was recently developed for rotavirus (RV), opening new avenues for in-depth molecular dissection of RV biology, immunology, and pathogenesis. Several improvements to further optimize the RG efficiency have now been described. However, only a small number of individual RV strains have been recovered to date. None of the current methods have supported the recovery of murine RV, impeding the study of RV replication and pathogenesis in an in vivo suckling mouse model. Here, we describe useful modifications to the RG system that significantly improve rescue efficiency of multiple RV strains. In addition to the 11 RVA segment-specific (+)ssRNAs, a chimeric plasmid was transfected, from which the capping enzyme NP868R of African swine fever virus (ASFV) and the T7 RNA polymerase were expressed. Secondly, a genetically modified MA104 cell line was used in which several compounds of the innate immune were degraded. Using this RG system, we successfully recovered the simian RV RRV strain, the human RV CDC-9 strain, a reassortant between murine RV D6/2 and simian RV SA11 strains, and several reassortants and reporter RVs. All these recombinant RVs were rescued at a high efficiency (≥80% success rate) and could not be reliably rescued using several recently published RG strategies (<20%). This improved system represents an important tool and great potential for the rescue of other hard-to-recover RV strains such as low replicating attenuated vaccine candidates or low cell culture passage clinical isolates from humans or animals. IMPORTANCE Group A rotavirus (RV) remains as the single most important cause of severe acute gastroenteritis among infants and young children worldwide. An entirely plasmid-based reverse genetics (RG) system was recently developed opening new ways for in-depth molecular study of RV. Despite several improvements to further optimize the RG efficiency, it has been reported that current strategies do not enable the rescue of all cultivatable RV strains. Here, we described helpful modification to the current strategies and established a tractable RG system for the rescue of the simian RRV strain, the human CDC-9 strain and a murine-like RV strain, which is suitable for both in vitro and in vivo studies. This improved RV reverse genetics system will facilitate study of RV biology in both in vitro and in vivo systems that will facilitate the improved design of RV vaccines, better antiviral therapies and expression vectors.