Rabies virus (RABV) is a highly neurotropic pathogen that typically leads to mortality of infected animals and humans. The precise etiology of rabies neuropathogenesis is unknown, though it is hypothesized to be due either to neuronal death or dysfunction. Analysis of human brains post-mortem reveals surprisingly little tissue damage and neuropathology considering the dramatic clinical symptomology, supporting the neuronal dysfunction model. However, whether or not neurons survive infection and clearance and, provided they do, whether they are functionally restored to their pre-infection phenotype has not been determined in vivo for RABV, or any neurotropic virus. This is due, in part, to the absence of a permanent “mark” on once-infected cells that allow their identification long after viral clearance. Our approach to study the survival and integrity of RABV-infected neurons was to infect Cre reporter mice with recombinant RABV expressing Cre-recombinase (RABV-Cre) to switch neurons constitutively expressing tdTomato (red) to expression of a Cre-inducible EGFP (green), permanently marking neurons that had been infected in vivo. We used fluorescence microscopy and quantitative real-time PCR to measure the survival of neurons after viral clearance; we found that the vast majority of RABV-infected neurons survive both infection and immunological clearance. We were able to isolate these previously infected neurons by flow cytometry and assay their gene expression profiles compared to uninfected cells. We observed transcriptional changes in these “cured” neurons, predictive of decreased neurite growth and dysregulated microtubule dynamics. This suggests that viral clearance, though allowing for survival of neurons, may not restore them to their pre-infection functionality. Our data provide a proof-of-principle foundation to re-evaluate the etiology of human central nervous system diseases of unknown etiology: viruses may trigger permanent neuronal damage that can persist or progress in the absence of sustained viral antigen.

Recombinant rabies virus (RV)-based vectors have demonstrated their efficacy in generating long-term,antigen-specific immune responses in murine and monkey models. However, replication-competent viral vectors pose significant safety concerns due to vector pathogenicity. RV pathogenicity is largely attributed to its glycoprotein (RV-G), which facilitates the attachment and entry of RV into host cells. We have developed a live, single-cycle RV by deletion of the G gene from an RV vaccine vector expressing HIV-1 Gag (SPBN-⌬G-Gag). Passage of SPBN-⌬G-Gag on cells stably expressing RV-G allowed efficient propagation of the G-deleted RV. The in vivo immunogenicity data comparing single-cycle RV to a replication-competent control (BNSPGag) showed lower RV-specific antibodies; however, the overall isotype profiles (IgG2a/IgG1) were similar for the two vaccine vectors. Despite this difference, mice immunized with SPBN-⌬G-Gag and BNSP-Gag mounted similar levels of Gag-specific CD8؉ T-cell responses as measured by major histocompatibility complex class I Gag-tetramer staining, gamma interferon-enzyme-linked immunospot assay, and cytotoxic T-cell assay. Moreover, these cellular responses were maintained equally at immunization titers as low as 10 3 focus-forming units for both RV vaccine vectors. CD8؉ T-cell responses were significantly enhanced by a boost with a single-cycle RV complemented with a heterologous vesicular stomatitis virus glycoprotein. These findings demonstrate that single-cycle RV is an effective alternative to replication-competent RV vectors for future development of vaccines for HIV-1 and other infectious diseases.

Background Protection against human respiratory syncytial virus (RSV) remains an unmet need potentially addressable by maternal immunization. This phase 1/2 study evaluated a bivalent prefusion F vaccine (RSVpreF) with antigens from RSV subgroups A and B. Methods Adults 18–49 years old (N=618) were randomized to receive placebo or 60, 120, or 240 µg RSVpreF with or without Al(OH)3. Safety and immunogenicity were evaluated. Results RSVpreF recipients more frequently reported local reactions and systemic events than placebo recipients; these were mostly mild or moderate. No vaccine-related serious adverse events occurred through 12 months postvaccination. All RSVpreF formulations induced 1-month postvaccination virus-neutralizing titers higher than those associated with protection of high-risk infants by palivizumab, the only prophylactic currently available for RSV. Geometric mean fold rises (GMFRs) across RSVpreF doses/formulations were 10.6–16.9 for RSV A and 10.3–19.8 for RSV B at 1 month postvaccination, greater than those historically elicited by postfusion F vaccines. GMFRs were 3.9–5.2 and 3.7–5.1, respectively, at 12 months postvaccination. Conclusions RSVpreF formulations were safe, well tolerated, and induced robust neutralizing responses in adults. These findings support development of RSVpreF, which is being evaluated in a pivotal phase 3 study for maternal immunization.

Until recently, single-stranded negative sense RNA viruses (ssNSVs) were one of only a few important human viral pathogens, which could not be created from cDNA. The inability to manipulate their genomes hindered their detailed genetic analysis. A key paper from Conzelmann's laboratory in 1994 changed this with the publication of a method to recover rabies virus (RABV) from cDNA. This discovery not only dramatically changed the broader field of ssNSV biology but also opened a whole new avenue for studying RABV pathogenicity, developing novel RABV vaccines as well a new generation of RABV-based vaccine vectors, and creating research tools important in neuroscience such as neuronal tracing.

Background Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in older adults and adults with comorbidities. An effective vaccine is needed. An investigational bivalent prefusion F vaccine (RSVpreF) was assessed in healthy adults. Methods This phase 1/2 study randomized adults 18–85 years old to receive placebo or 60, 120, or 240 µg RSVpreF (with or without Al[OH]3) alone or concomitantly with seasonal inactivated influenza vaccine (SIIV). Safety and immunogenicity were assessed. Results In older adults, reactogenicity events were predominantly mild or moderate among RSVpreF recipients; adverse events through 1 month postvaccination were similar across formulations. Coadministration with SIIV did not appear to affect safety among younger or older adults. All RSVpreF formulations with or without concomitant SIIV elicited robust RSV serum neutralizing responses in adults 50–85 years 1 month postvaccination. Neutralizing titers 1 and 12 months postvaccination were 6.9–14.9- and 2.9–4.5-times, respectively, those before vaccination. SIIV immune responses trended lower when coadministered with RSVpreF. Conclusions RSVpreF formulations administered alone or with SIIV were well tolerated and highly immunogenic in older adults, supporting the potential for RSVpreF to protect older adults from RSV disease.