Single Dose of Recombinant Chimeric Horsepox Virus (TNX-801) Vaccination Protects Macaques from Lethal Monkeypox Challenge.

The ongoing global Monkeypox outbreak that started in the spring of 2022 has reinforced the importance of protecting the population using live virus vaccines based on the vaccinia virus (VACV). Smallpox also remains a biothreat and although some U.S. military personnel are immunized with VACV, safety concerns limit its use in other vulnerable groups. Consequently, there is a need for an effective and safer, single dose, live replicating vaccine against both viruses. One potential approach is to use the horsepox virus (HPXV) as a vaccine. Contemporary VACV shares a common ancestor with HPXV, which from the time of Edward Jenner and through the 19th century, was extensively used to vaccinate against smallpox. However, it is unknown if early HPXV-based vaccines exhibited different safety and efficacy profiles compared to modern VACV. A deeper understanding of HPXV as a vaccine platform may allow the construction of safer and more effective vaccines against the poxvirus family. In a proof-of-concept study, we vaccinated cynomolgus macaques with TNX-801, a recombinant chimeric horsepox virus (rcHPXV), and showed that the vaccine elicited protective immune responses against a lethal challenge with monkeypox virus (MPXV), strain Zaire. The vaccine was well tolerated and protected animals from the development of lesions and severe disease. These encouraging data support the further development of TNX-801.

Characterization of Three Variants of SARS-CoV-2 In Vivo Shows Host-Dependent Pathogenicity in Hamsters, While Not in K18-hACE2 Mice.

Animal models are used in preclinical trials to test vaccines, antivirals, monoclonal antibodies, and immunomodulatory drug therapies against SARS-CoV-2. However, these drugs often do not produce equivalent results in human clinical trials. Here, we show how different animal models infected with some of the most clinically relevant SARS-CoV-2 variants, WA1/2020, B.1.617.2/Delta, B.1.1.529/Omicron, and BA5.2/Omicron, have independent outcomes. We show that in K18-hACE2 mice, B.1.617.2 is more pathogenic, followed by WA1, while B.1.1.529 showed an absence of clinical signs. Only B.1.1.529 was able to infect C57BL/6J mice, which lack the human ACE2 receptor. B.1.1.529-infected C57BL/6J mice had different T cell profiles compared to infected K18-hACE2 mice, while viral shedding profiles and viral titers in lungs were similar between the K18-hACE2 and the C57BL/6J mice. These data suggest B.1.1.529 virus adaptation to a new host and shows that asymptomatic carriers can accumulate and shed virus. Next, we show how B.1.617.2, WA1 and BA5.2/Omicron have similar viral replication kinetics, pathogenicity, and viral shedding profiles in hamsters, demonstrating that the increased pathogenicity of B.1.617.2 observed in mice is host-dependent. Overall, these findings suggest that small animal models are useful to parallel human clinical data, but the experimental design places an important role in interpreting the data. Importance: There is a need to investigate SARS-CoV-2 variant phenotypes in different animal models due to the lack of reproducible outcomes when translating experiments to the human population. Our findings highlight the correlation of clinically relevant SARS-CoV-2 variants in animal models with human infections. Experimental design and understanding of correct animal models are essential to interpreting data to develop antivirals, vaccines, and other therapeutic compounds against COVID-19.

A Novel Oral GyrB/ParE Dual Binding Inhibitor Effective against Multidrug-Resistant Neisseria gonorrhoeae and Other High-Threat Pathogens.

Drug-resistant Neisseria gonorrhoeae is a serious global health concern. New drugs are needed that can overcome existing drug resistance and limit the development of new resistances. Here, we describe the small molecule tricyclic pyrimidoindole JSF-2414 [8-(6-fluoro-8-(methylamino)-2-((2-methylpyrimidin-5-yl)oxy)-9H-pyrimido[4,5-b]indol-4-yl)-2-oxa-8-azaspiro[4.5]decan-3-yl)methanol], which was developed to target both ATP-binding regions of DNA gyrase (GyrB) and topoisomerase (ParE). JSF-2414 displays potent activity against N. gonorrhoeae, including drug-resistant strains. A phosphate pro-drug, JSF-2659, was developed to facilitate oral dosing. In two different animal models of Neisseria gonorrhoeae vaginal infection, JSF-2659 was highly efficacious in reducing microbial burdens to the limit of detection. The parent molecule also showed potent in vitro activity against high-threat Gram-positive organisms, and JSF-2659 was shown in a deep tissue model of vancomycin-resistant Staphylococcus aureus (VRSA) and a model of Clostridioides difficile-induced colitis to be highly efficacious and protective. JSF-2659 is a novel preclinical drug candidate against high-threat multidrug resistant organisms with low potential to develop new resistance.

Evidence of simian virus 40 exposure in a colony of captive baboons.

Simian virus 40 (SV40) is a polyomavirus for which non-human primates are the permissive host. The baboon (Papio spp.) is an old world monkey that is used in a variety of research investigations; however, natural infection of SV40 among baboons has not been thoroughly examined or reported. Initially, we were interested in determining the prevalence of SV40 infection among a captive colony of baboons based on the presence of antibodies to SV40 large T-antigen (Tag). An overall seroprevalence rate of >50% was found after screening sera from 142 baboons in the colony based on ELISA. Endpoint titer values for serum antibody binding to SV40 Tag reached as high as 1280 for 5 out of 142 baboons. Peptide binding assays revealed that a range of SV40 Tag epitopes are immunogenic in the baboon, and that individual animals differ in their humoral immune responses to SV40 Tag based on epitope recognition. Specificity to SV40 Tag and not some other primate polyomavirus encoded large Tag was further examined by serologic reactivity to peptide epitopes unique to SV40 Tag. Additional serology was performed to assess SV40 Tag reactivity by Western blot and whether antibodies were capable of neutralizing SV40 infectivity in vitro. Although antibodies with high levels of SV40 neutralization were observed in a number of the baboons, there was a lack of correlation between viral neutralization and antibodies to SV40 Tag. Further examination using molecular-based diagnosis and SV40 Tag specific real-time quantitative PCR determined that some of the baboons appeared to be exposed to SV40. DNA sequence analysis of the PCR products confirmed that SV40 Tag specific sequences were detected in baboons.

mvaT mutation modifies the expression of the Pseudomonas aeruginosa multidrug efflux operon mexEF-oprN.

Pseudomonas aeruginosa carries several multidrug efflux operons, including mexEF-oprN, that contribute to its resistance to multiple antibiotics. mvaT affects the expression of several P. aeruginosa genes. In this study, we show that the mvaT mutant PAODeltamvaT is more resistant than its parent PAO1 strain to chloramphenicol and norfloxacin but more sensitive to imipenem; yet both were less resistant to chloramphenicol, norfloxacin, and imipenem than 'typical'nfxC-type mutants. Neither strain carries the deletion described for nfxC-type mutants in mexT, the mexEF-oprN regulatory gene. Expression of mexEF-oprN is increased by five- to sixfold in PAODeltamvaT, while the expression of oprD is reduced by approximately twofold. mvaT mutation had no effect on the expression of other multidrug resistance operons, although it increased the expression of several ATP-binding cassette transporter genes. We show that mvaT mutation does not affect mexEF-oprN expression through mexT or mexS. We also explored several other potential mechanisms.

The Pseudomonas aeruginosa global regulator MvaT specifically binds to the ptxS upstream region and enhances ptxS expression.

Exotoxin A production in Pseudomonas aeruginosa is regulated positively or negatively by several genes. Two such regulatory genes, ptxR and ptxS, which are divergently transcribed from each other, have been described previously. While computer analysis suggested that the ptxR-ptxS intergenic region contains potential binding sites for several regulatory proteins, the mechanism that regulates the expression of either ptxR or ptxS in P. aeruginosa is not known. The presence of a P. aeruginosa protein complex that specifically binds to a segment within this region was determined. In this study the binding region was localized to a 150 bp fragment of the intergenic region and the proteins that constitute the binding complex were characterized as P. aeruginosa HU and MvaT. Recombinant MvaT was purified as a fusion protein (MAL-MvaT) and shown to specifically bind to the ptxR-ptxS intergenic region. A PAO1 isogenic mutant defective in mvaT, PAODeltamvaT, was constructed and characterized. The lysate of PAODeltamvaT failed to bind to the 150 bp probe. The effect of mvaT on ptxS and ptxR expression was examined using real-time PCR experiments. The expression of ptxS was lower in PAODeltamvaT than in PAO1, but no difference was detected in ptxR expression. These results suggest that MvaT positively regulates ptxS expression by binding specifically to the ptxS upstream region.