Pathogenicity In Mice Research Articles

Irradiated whole cell Chlamydia vaccine confers significant protection in a murine genital tract challenge model.

Chlamydia trachomatis infections are the most common bacterial STIs globally and can lead to serious morbidity if untreated. Development of a killed, whole-cell vaccine has been stymied by coincident epitope destruction during inactivation. Here, we present a prototype Chlamydia vaccine composed of elementary bodies (EBs) from the related mouse pathogen, Chlamydia muridarum (Cm). EBs inactivated by gamma rays (Ir-Cm) in the presence of the antioxidant Mn2+-Decapeptide (DEHGTAVMLK) Phosphate (MDP) are protected from epitope damage but not DNA damage. Cm EBs gamma-inactivated with MDP retain their structure and provide significant protection in a murine genital tract infection model. Mice vaccinated with Ir-Cm (+MDP) exhibited elevated levels of Cm-specific IgG and IgA antibodies, reduced bacterial burdens, accelerated clearance, and distinctive cytokine responses compared to unvaccinated controls and animals vaccinated with EBs irradiated without MDP. Preserving EB epitopes with MDP during gamma inactivation offers the potential for a polyvalent, whole-cell vaccine against C. trachomatis.

Development of KSHV vaccine platforms and chimeric MHV68-K-K8.1 glycoprotein for evaluating the in vivo immunogenicity and efficacy of KSHV vaccine candidates.

Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8 is an etiological agent of Kaposi's Sarcoma, multicentric Castleman's disease, and primary effusion lymphoma. Considering the high seroprevalence reaching up to 80% in sub-Saharan Africa, an effective vaccine is crucial for preventing KSHV infection. However, vaccine development has been limited due to the lack of an effective animal model that supports KSHV infection. Murine Herpesvirus 68 (MHV68), a natural mouse pathogen persisting lifelong post-infection, presents a promising model for KSHV infection. In this study, we developed KSHV vaccine and a chimeric MHV68 carrying the KSHV glycoprotein, serving as a surrogate challenge virus for testing KSHV vaccines in a mouse model. Among KSHV virion glycoproteins, K8.1 is the most abundant envelope glycoprotein with the highest immunogenicity. We developed two K8.1 vaccines: K8.1 mRNA-lipid nanoparticle (LNP) vaccine and K8.126-87-Ferritin (FT) nanoparticle vaccines. Both induced humoral responses in immunized mice, whereas K8.1 mRNA LNP also induced T cell responses. Using BACmid-mediated homologous recombination, the MHV68 M7 (gp150) gene was replaced with KSHV K8.1 gene to generate chimeric MHV68-K-K8.1. MHV68-K-K8.1 established acute and latent infection in the lungs and spleens of infected mice, respectively. Mice immunized with K8.1 mRNA LNP or K8.126-87-FT showed a reduction of MHV68-K-K8.1 titer but not MHV68 wild type (WT) titer in the lung. In addition, viral reactivation of MHV68-K-K8.1 was also significantly reduced in K8.1 mRNA LNP-immunized mice. This study demonstrates the effectiveness of two vaccine candidates in providing immunity against KSHV K8.1 and introduces a surrogate MHV68 system for evaluating vaccine efficacy in vivo.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) is a prevalent virus that establishes lifelong persistent infection in humans and is linked to several malignancies. While antiretroviral therapy has reduced Kaposi's Sarcoma (KS) complications in people with HIV, KS still affects individuals with well-controlled HIV, older men without HIV, and transplant recipients. Despite its significant impact on human health, however, research on KSHV vaccine has been limited, mainly due to the lack of interest and the absence of a suitable animal model. This study addresses these challenges by developing KSHV K8.1 vaccine with two platforms, mRNA lipid nanoparticle (LNP) and FT nanoparticle. Additionally, chimeric virus, MHV68-K-K8.1, was created to evaluate KSHV vaccine efficacy in vivo. Vaccination of K8.1 mRNA LNP or K8.126-87-FT significantly reduced MHV68-K-K8.1 titers. Developing an effective KSHV vaccine requires an innovative approach to ensure safety and efficacy, especially for the immunocompromised population and people with limited healthcare resources. This study could be a potential blueprint for future KSHV vaccine development.

Two amino acid residues in the N-terminal region of the polymerase acidic protein determine the virulence of Eurasian avian-like H1N1 swine influenza viruses in mice.

Reassortant Eurasian avian-like H1N1 (rEA H1N1) viruses carrying the internal genes of H1N1/2009 virus have been circulating in pigs for more than 10 years and have caused sporadic human infections. The enhanced virulence phenotype of the rEA H1N1 viruses highlights potential risks to public health. However, the molecular mechanism underlying the viral pathogenicity of the currently circulating rEA H1N1 viruses remains unclear. In this study, we found that two naturally isolated rEA H1N1 swine influenza viruses, A/swine/Liaoning/FX38/2017 (FX38) and A/swine/Liaoning/SY72/2018 (SY72), possessed similar genetic characteristics but exhibited significantly different pathogenicity in a mouse model. Using reverse genetics, we demonstrated that amino acid mutations at positions 100 and 122 in the polymerase acidic (PA) protein had individual and synergistic effects on the polymerase activity and viral replication capacity in vitro, as well as the viral pathogenicity in mice. Furthermore, we revealed that amino acid residue 100 in PA influenced the transcription of viral RNA (vRNA) by altering the endonuclease activity, and amino acid residue 122 affected the synthesis of complementary RNA and messenger RNA by altering the RNA-binding ability and endonuclease activity of the PA protein. Taken together, we identified that two naturally occurring amino acid mutations in PA derived from H1N1/2009 virus are crucial determinants of the virulence of rEA H1N1 viruses and revealed the differential mechanism by which these two mutations affect the transcription and replication of vRNA. These findings will extend our understanding of the roles of PA in the virulence of influenza A viruses.IMPORTANCEMultiple genetic determinants are involved in the virulence of influenza A viruses. In this study, we identified two naturally occurring amino acid mutations, located at residues 100 and 122 in the polymerase acidic (PA) protein, which are associated with viral polymerase activity, replication competence, and pathogenicity in mice. In particular, we clarified the specific mechanism by which the two residues play an important role in viral transcription and replication. These findings will help to improve understanding the functions of amino acid residues in the N-terminal region of the PA protein involved in the pathogenicity of influenza A viruses.

Inter and Intraserotype Variations of Streptococcus Pneumoniae Pathogenicity in Mice and Rabbits

The small mammalian labratory animals, the mice and the rabbits were tempted to be pathogenicity models for S. pneumoniae serotypes 1 and 6, the infecting doses were 0.3ml for mice and 0.5 ml for rabbits. These infectious doses were rated to a count of 1X 10 to 7 CFU/ml. The infection routes were intrapreritoneal for mice and intranasal for rabbits. The gold standard criteria for pathogenicity were the death end point DEP.DEP was up to 24hr for mice and ranged from four to 14 days in rabbits. Mice was more susciptable than rabbits for S. pneumoniae serotypes infections. Autopsy cultures of blood, lungs, liver and kideys were producing same infecting serotype both from mice and rabbits. This isolation profile was indicating bacterimic state induced by infection. Different serotypes have shown different death end points duration time. There were inter and intraserotype variations in DEP. Moderate to severe respiratory disease conditions RDC was noted in mice while mild RDC in rabbits. Both of the tested models were similar lung histology to man. The histological features of this experimental infections have shown that the infected mice and rabbits were of bronchopneumonia type. It appears that both mice and rabbits were standing as valid laboratory animal models for these local clinical isolates of S. pneumoniae serotypes.

In situ deposition of nanobodies by an engineered commensal microbe promotes survival in a mouse model of enterohemorrhagic E. coli.

Engineered smart microbes that deliver therapeutic payloads are emerging as treatment modalities, particularly for diseases with links to the gastrointestinal tract. Enterohemorrhagic Escherichia coli (EHEC) is a causative agent of potentially lethal hemolytic uremic syndrome. Given concerns that antibiotic treatment increases EHEC production of Shiga toxin (Stx), which is responsible for systemic disease, novel remedies are needed. EHEC encodes a type III secretion system (T3SS) that injects Tir into enterocytes. Tir inserts into the host cell membrane, exposing an extracellular domain that subsequently binds intimin, one of its outer membrane proteins, triggering the formation of attaching and effacing (A/E) lesions that promote EHEC mucosal colonization. Citrobacter rodentium (Cr), a natural A/E mouse pathogen, similarly requires Tir and intimin for its pathogenesis. Mice infected with Cr(ΦStx2dact), a variant lysogenized with an EHEC-derived phage that produces Stx2dact, develop intestinal A/E lesions and toxin-dependent disease. Stx2a is more closely associated with human disease. By developing an efficient approach to seamlessly modify the C. rodentium genome, we generated Cr_Tir-MEHEC(ΦStx2a), a variant that expresses Stx2a and the EHEC extracellular Tir domain. We found that mouse precolonization with HS-PROT3EcT-TD4, a human commensal E. coli strain (E. coli HS) engineered to efficiently secrete an anti-EHEC Tir nanobody, delayed bacterial colonization and improved survival after challenge with Cr_Tir-MEHEC(ΦStx2a). This study suggests that commensal E. coli engineered to deliver payloads that block essential virulence determinants can be developed as a new means to prevent and potentially treat infections including those due to antibiotic resistant microbes.

Performance of three multiplex real-time PCR assays for simultaneous detection of 12 infectious pathogens in mice affected with respiratory and digestive diseases.

Research quality can be improved with reliable and reproducible experimental results when animal experiments are conducted using laboratory animals with guaranteed microbiological and genetic quality through health monitoring. Therefore, health monitoring requires the rapid and accurate diagnosis of infectious diseases in laboratory animals. This study presents a performance evaluation of a commercially available multiplex real-time PCR (mRT-PCR) assay for the rapid detection of 12 infectious pathogens (Set 1: Sendai virus [SeV, formally murine respirovirus], Mycoplasma spp., Rodentibacter pneumotropicus, and Rodentibacter heylii; Set 2: Helicobacter spp., Murine norovirus [MNV], Murine hepatitis virus [MHV], and Salmonella spp.; Set 3: Staphylococcus aureus, Streptobacillus moniliformis, Corynebacterium kutscheri, and Pseudomonas aeruginosa). To evaluate the efficacy of the mRT-PCR assay, 102 clinical samples encompassing fecal and cecal specimens were analyzed. The resulting data were then compared with the findings from sequence analysis for validation. The assay's detection limit ranged from 1 to 100 copies per reaction. Specificity testing involving various viruses and bacteria indicated no cross-reactivity between strains. Additionally, the assay exhibited good reproducibility, with mean coefficients of variation for inter- and intra assay variation below 3%. The overall positive rate was 52.9% (n = 54), with the mRT-PCR assay findings matching sequence analysis results (κ = 1). MHV (n = 29, 28.4%) was the most prevalent pathogen, followed by Helicobacter spp. (n = 28, 27.5%), R. heylii (n = 18, 17.6%), Mycoplasma spp. (n = 14, 13.7%), MNV (n = 12, 11.8%), S. aureus (n = 9, 8.8%), P. aeruginosa (n = 4, 3.9%), and R. pneumotropicus (n = 1, 0.9%). This assay offers a rapid turnaround time of 100 min, including 30 min for DNA preparation and 70 min for target DNA/RNA amplification. It ensures accuracy, minimizing false positives or negatives, making it a convenient tool for the simultaneous detection of infectious diseases in many samples. Overall, the propose‑d assay holds promise for the effective detection of the most important pathogens in laboratory animal health monitoring.

The PB2 I714S mutation influenced mammalian adaptation of the H3N2 canine influenza virus by interfering with nuclear import efficiency and RNP complex assembly

ABSTRACT Avian influenza viruses (AIVs) are the origin of multiple mammal influenza viruses. The genetic determinants of AIVs adapted to humans have been widely elucidated, however, the molecular mechanism of cross-species transmission and adaptation of AIVs to canines are still poorly understood. In this study, two H3N2 influenza viruses isolated from a live poultry market (A/environment/Guangxi/13431/2018, GX13431) and a swab sample from a canine (A/canine/Guangdong/0601/2019, GD0601) were used to investigate the possible molecular basis that determined H3N2 AIV adapting to canine. We found that GD0601 exhibited more robust polymerase activity in cells and higher pathogenicity in mice compared with its evolution ancestor H3N2 AIV GX13431. A series of reassortments of the ribonucleoprotein (RNP) complex showed that the PB2 subunit was the crucial factor that conferred high polymerase activity of GD0601, and the substitution of I714S in the PB2 subunit of GD0601 attenuated the replication and pathogenicity in mammal cells and the mouse model. Mechanistically, the reverse mutation of I714S in the PB2 polymerase subunit which was identified in AIV GX13431 reduced the nuclear import efficiency of PB2 protein and interfered with the interactions of PB2-PA/NP that affected the assembly of the viral RNP complex. Our study reveals amino acid mutation at the position of 714 in the nuclear localization signal (NLS) area in PB2 plays an important role in overcoming the barrier from poultry to mammals of the H3N2 canine influenza virus and provides clues for further study of mammalian adaptation mechanism of AIVs.

Amino Acids at Positions 156 and 332 in the E Protein of the West Nile Virus Subtype Kunjin Virus Classical Strain OR393 Are Involved in Plaque Size, Growth, and Pathogenicity in Mice.

The West Nile virus (WNV) subtype Kunjin virus (WNVKUN) is endemic to Australia. Here, we characterized the classical WNVKUN strain, OR393. The original OR393 strain contained two types of viruses: small plaque-forming virus (SP) and large plaque-forming virus (LP). The amino acid residues at positions 156 and 332 in the E protein (E156 and E332) of SP were Ser and Lys (E156S/332K), respectively, whereas those in LP were Phe and Thr (E156F/332T). SP grew slightly faster than LP in vitro. The E protein of SP was N-glycosylated, whereas that of LP was not. Analysis using two recombinant single-mutant LP viruses, rKUNV-LP-EF156S and rKUNV-LP-ET332K, indicated that E156S enlarged plaques formed by LP, but E332K potently reduced them, regardless of the amino acid at E156. rKUNV-LP-EF156S showed significantly higher neuroinvasive ability than LP, SP, and rKUNV-LP-ET332K. Our results indicate that the low-pathogenic classical WNVKUN can easily change its pathogenicity through only a few amino acid substitutions in the E protein. It was also found that Phe at E156 of the rKUNV-LP-ET332K was easily changed to Ser during replication in vitro and in vivo, suggesting that E156S is advantageous for the propagation of WNVKUN in mammalian cells.

Development of an entirely cloned cDNA-based reverse genetics system for Tofla virus of orthonairovirus

The genus Orthonairovirus includes highly pathogenic tick-borne viruses such as the Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV). A reverse genetics system is an indispensable tool for determining the viral factors related to pathogenicity. Tofla orthonairovirus (TFLV) is a recently identified virus isolated from ticks in Japan and our research has suggested that TFLV is a useful model for studying pathogenic orthonairoviruses. In this study, we successfully established a reverse genetics system for TFLV using T7 RNA polymerase. Recombinant TFLV was generated by transfecting cloned complementary DNAs encoding the TFLV genome into BSR T7/5 cells expressing T7 RNA polymerase. We were able to rescue infectious recombinant TFLV mutant (rTFLVmt) and wild-type TFLV (rTFLVpt) viruses, which exhibited indistinguishable growth kinetics in mammalian cells and pathogenicity in A129 mice compared with the authentic virus. Our approach provides a valuable method for establishing reverse genetics system for orthonairoviruses.

Amino acid mutations PB1-V719M and PA-N444D combined with PB2-627K contribute to the pathogenicity of H7N9 in mice

H7N9 subtype avian influenza viruses (AIVs) cause 1567 human infections and have high mortality, posing a significant threat to public health. Previously, we reported that two avian-derived H7N9 isolates (A/chicken/Eastern China/JTC4/2013 and A/chicken/Eastern China/JTC11/2013) exhibit different pathogenicities in mice. To understand the genetic basis for the differences in virulence, we constructed a series of mutant viruses based on reverse genetics. We found that the PB2-E627K mutation alone was not sufficient to increase the virulence of H7N9 in mice, despite its ability to enhance polymerase activity in mammalian cells. However, combinations with PB1-V719M and/or PA-N444D mutations significantly enhanced H7N9 virulence. Additionally, these combined mutations augmented polymerase activity, thereby intensifying virus replication, inflammatory cytokine expression, and lung injury, ultimately increasing pathogenicity in mice. Overall, this study revealed that virulence in H7N9 is a polygenic trait and identified novel virulence-related residues (PB2-627K combined with PB1-719M and/or PA-444D) in viral ribonucleoprotein (vRNP) complexes. These findings provide new insights into the molecular mechanisms underlying AIV pathogenesis in mammals, with implications for pandemic preparedness and intervention strategies.

Lyssavirus matrix protein inhibits NLRP3 inflammasome assembly by binding to NLRP3

Lyssavirus is a kind of neurotropic pathogen that needs to evade peripheral host immunity to enter the central nervous system to accomplish infection. NLRP3 inflammasome activation is essential for the host to defend against pathogen invasion. This study demonstrates that the matrix protein (M)of lyssavirus can inhibit both the priming step and the activation step of NLRP3 inflammasome activation. Specifically, M of lyssavirus can compete with NEK7 for binding to NLRP3, which restricts downstream apoptosis-associated speck-like protein containing a CARD (ASC) oligomerization. The serine amino acid at the 158th site of M among lyssavirus is critical for restricting ASC oligomerization. Moreover, recombinant lab-attenuated lyssavirus rabies (rabies lyssavirus [RABV]) with G158S mutation at M decreases interleukin-1β (IL-1β) production in bone-marrow-derived dendritic cells (BMDCs) to facilitate lyssavirus invasion into the brain thereby elevating pathogenicity in mice. Taken together, this study reveals a common mechanism by which lyssavirus inhibits NLRP3 inflammasome activation to evade host defenses.

Swine Influenza Viruses Isolated from 2019 to 2022 in Shandong Province, China, Exemplify the Dominant Genotype.

Swine influenza viruses (SIVs) have been circulating in swine globally and are potential threats to human health. During the surveillance of SIVs in Shandong Province, China, from 2019 to 2022, 21 reassortant G4 genotype Eurasian avian-like (EA) H1N1 subtypes containing genes from the EA H1N1 (HA and NA), 2009 pandemic (pdm/09) H1N1 virus (PB2, PB1, PA, NP, and M), and classical swine (CS) H1N1 (NS) lineages were isolated. The analysis of the key functional amino acid sites in the isolated viruses showed that two mutation sites (190D and 225E) that preferentially bind to the human α2-6 sialic acid receptor were found in HA. In PB2, three mutation sites (271A, 590S, and 591R) that may increase mammalian fitness and a mutation site (431M) that increases pathogenicity in mice were found. A typical human signature marker that may promote infection in humans, 357K, was found in NP. The viruses could replicate efficiently in mouse lungs and turbinates, and one of the H1N1 isolates could replicate in mouse kidneys and brains without prior adaption, which indicates that the viruses potentially pose a threat to human health. Histopathological results showed that the isolated viruses caused typical bronchopneumonia and encephalitis in mice. The results indicate that G4 genotype H1N1 has potential transmissibility to humans, and surveillance should be enhanced, which could provide important information for assessing the pandemic potential of the viruses.

R229I substitution from oseltamivir induction in HA1 region significantly increased the fitness of a H7N9 virus bearing NA 292K

ABSTRACT The proportion of human isolates with reduced neuraminidase inhibitors (NAIs) susceptibility in highly pathogenic avian influenza (HPAI) H7N9 virus was high. These drug-resistant strains showed good replication capacity without serious loss of fitness. In the presence of oseltamivir, R229I substitution were found in HA1 region of the HPAI H7N9 virus before NA R292K appeared. HPAI H7N9 or H7N9/PR8 recombinant viruses were developed to study whether HA R229I could increase the fitness of the H7N9 virus bearing NA 292K. Replication efficiency was assessed in MDCK or A549 cells. Neuraminidase enzyme activity and receptor-binding ability were analyzed. Pathogenicity in C57 mice was evaluated. Antigenicity analysis was conducted through a two-way HI test, in which the antiserum was obtained from immunized ferrets. Transcriptomic analysis of MDCK infected with HPAI H7N9 24hpi was done. It turned out that HA R229I substitution from oseltamivir induction in HA1 region increased (1) replication ability in MDCK(P < 0.05) and A549(P < 0.05), (2) neuraminidase enzyme activity, (3) binding ability to both α2,3 and α2,6 receptor, (4) pathogenicity to mice(more weight loss; shorter mean survival day; viral titer in respiratory tract, P < 0.05; Pathological changes in pneumonia), (5) transcriptome response of MDCK, of the H7N9 virus bearing NA 292K. Besides, HA R229I substitution changed the antigenicity of H7N9/PR8 virus (>4-fold difference of HI titre). It indicated that through the fine-tuning of HA-NA balance, R229I increased the fitness and changed the antigenicity of H7N9 virus bearing NA 292K. Public health attention to this mechanism needs to be drawn.

NSUN2 mediates distinct pathways to regulate enterovirus 71 replication

Increasing evidences suggest that the methyltransferase NSUN2 catalyzes 5-methylcytosine (m5C) modifications on viral RNAs, which are essential for the replication of various viruses. Despite the function of m5C deposition is well characterized, other potential roles of NSUN2 in regulating viral replication remain largely unknown. In this study, the m5C modified residues catalyzed by NSUN2 on enterovirus 71 (EV71) RNAs were mapped. NSUN2, along with m5C modifications, played multiple roles during the EV71 life cycle. Functional m5C modified nucleotides increased the translational efficiency and stability of EV71 RNAs. Additionally, NSUN2 was found to target the viral protein VP1 for binding and promote its stability by inhibiting the ubiquitination. Furthermore, both viral replication and pathogenicity in mice were largely attenuated when functional m5C residues were mutated. Taken together, this study characterizes distinct pathways mediated by NSUN2 in regulating EV71 replication, and highlights the importance of its catalyzed m5C modifications on EV71 RNAs for the viral replication and pathogenicity.

Japanese Encephalitis Virus and Schizophyllum commune Co-Infection in a Harbor Seal in Japan.

The Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, has a wide host range, extending from pigs and ardeid birds to opportunistic dead-end hosts, such as humans and horses. However, JEV encephalitis infections in aquatic mammals are rare, with only two cases in seals reported to date. Here, we report a lethal case of JEV and Schizophyllum commune co-infection in an aquarium-housed harbor seal in Japan. We isolated JEV from the brain of the dead seal and characterized its phylogeny and pathogenicity in mice. The virus isolate from the seal was classified as genotype GIb, which aligns with recent Japanese human and mosquito isolates as well as other seal viruses detected in China and Korea, and does not exhibit a unique sequence trait distinct from that of human and mosquito strains. We demonstrated that the seal isolate is pathogenic to mice and causes neuronal symptoms. These data suggest that seals should be considered a susceptible dead-end host for circulating JEV in natural settings.

Further Evaluation of Enterohemorrhagic Escherichia coli Gold Nanoparticle Vaccines Utilizing Citrobacter rodentium as the Model Organism.

Enterohemorrhagic E. coli (EHEC) is a group of pathogenic bacteria that is associated with worldwide human foodborne diarrheal illnesses and the development of hemolytic uremic syndrome, a potentially deadly condition associated with Shiga toxins (Stxs). Currently, approved vaccines for human prophylaxis against infection do not exist, and one barrier preventing the successful creation of EHEC vaccines is the absence of dependable animal models, including mice, which are naturally resistant to EHEC infection and do not manifest the characteristic signs of the illness. Our lab previously developed gold nanoparticle (AuNP)-based EHEC vaccines, and assessed their efficacy using Citrobacter rodentium, which is the mouse pathogen counterpart of EHEC, along with an Stx2d-producing strain that leads to more consistent disease kinetics in mice, including lethality. The purpose of this study was to continue evaluating these vaccines to increase protection. Here, we demonstrated that subcutaneous immunization of mice with AuNPs linked to the EHEC antigens EscC and intimin (Eae), either alone or simultaneously, elicits functional robust systemic humoral responses. Additionally, vaccination with both antigens together showed some efficacy against Stx2d-producing C. rodentium while AuNP-EscC successfully limited infection with non-Stx2d-producing C. rodentium. Overall, the collected results indicate that our AuNP vaccines have promising potential for preventing disease with EHEC, and that evaluation of novel vaccines using an appropriate animal model, like C. rodentium described here, could be the key to finally developing an effective EHEC vaccine that can progress into human clinical trials.

Immune experiences alter tolerance in T cell-mediated autoimmunity.

Abstract Autoimmune diseases afflict &amp;gt;20M Americans and alarmingly the incidence of autoimmune diseases is increasing particularly in children. The hygiene hypothesis (HH) proposes that there is an inverse correlation between microbial exposure and subsequent development of autoimmunity, i.e., the “cleaner” the environment, the higher the probability that autoimmunity develops. Critically, how microbial exposures and infections alter self-antigen (Ag), a critical component of immune tolerance, is unknown. Our data show that immune-experienced mice have decreased self-specific CD8 T cell priming and organ pathology mediated by resident cells in lymph nodes (LN). Resident Ag-bearing LN stromal cells isolated from immune-experienced mice induced less self-specific CD8 T cell proliferation in vitro indicating changes in self-Ag. The HH determines that environmental stressors are important drivers of autoimmunity, yet the human immune experience is poorly modeled in SPF models of tolerance and autoimmunity. Therefore, we used mice exposed to natural mouse pathogens, "dirty" mice showed a decrease in T cell activity to self-Ag. The cohousing of NOD mice with pet shop mice resulted in zero mice developing autoimmune diabetes. Overall, our data suggest novel mechanisms by which self-antigen is altered in lymph nodes due to previous immune experiences addressing a critical mechanism behind the hygiene hypothesis, intersecting TCR reactivity with environmental impact.

Evaluation of a Novel Battery-Operated Tumbler Device for Use in the Detection of Mouse Pathogens for Rodent Health Monitoring.

The search for alternatives to live animal sentinels in rodent health monitoring programs is fundamental to the 3Rs (Reduction, Replacement, and Refinement) of animal research. We evaluated the efficacy of a novel battery-operated tumbler device that rotates soiled bedding in direct contact with sample media against the use of exhaust sample media and soiled bedding sentinel (SBS) mice. Four rodent racks were used, each with 3 test cages: a cage with a tumbler device that rotated for 10min twice a week (TUM10), a cage with a tumbler device that rotated for 60min twice a week (TUM60), and a cage housing 2 female Crl:CD1(ICR) mice. Every 2 wk, each test cage received soiled bedding collected from all cages on each respective rack. In addition to soiled bedding, the tumbler device contained various sample collection media: a contact Reemay filter (3mo-cRF) that remained in the tumbler for the duration of the study, a contact Reemay filter (1mo-cRF) that was replaced monthly, adhesive swabs (AS) that were added at every biweekly cage change, and an exhaust Reemay filter located at the exhaust outlet of the cage. All analyses were performed by direct PCR for both sample media in the animal-free methods, and fecal pellet, body swab, and oral swabs were collected from sentinel mice. Out of 16 total pathogens detected, assessment of 1mo-Crf from both TUM10 and TUM60 cages detected 84% and 79% of pathogens, respectively, while SBS samples detected only 47% of pathogens. AS in TUM60 and TUM10 cages detected the fewest pathogens (24% and 13%, respectively). These results indicate that the novel tumbler device is an effective and reliable tool for rodent health monitoring programs and a suitable replacement for live animal sentinels. In this study, 1mo-cRF in TUM10 cages detected the highest number of pathogens.

Comparison of gastric inflammation and metaplasia induced by Helicobacter pylori or Helicobacter felis colonization in mice.

Mouse infection models with Helicobacter species are widely used to study Helicobacter pathogenesis and gastric cancer initiation. However, Helicobacter pylori is not a natural mouse pathogen, and mouse-adapted H. pylori strains are poorly immunogenic. In contrast, Helicobacter felis is a natural mouse pathogen that induces robust gastric inflammation and is often used in mice to investigate gastric cancer initiation. Although both bacterial strains are widely used, their disease pathogenesis in mice differs dramatically. However, few studies have directly compared the pathogenesis of these bacterial species in mice, and the contrasting features of these two models are not clearly defined. This study directly compares the gastric inflammation, atrophy, and metaplasia development triggered by the widely used PMSS1 H. pylori and CS1 H. felis strains in mice. It serves as a useful resource for researchers to select the experimental model best suited for their studies.

Evolutionary dynamics and comparative pathogenicity of clade 2.3.4.4b H5 subtype avian influenza viruses, China, 2021–2022

The recent concurrent emergence of H5N1, H5N6, and H5N8 avian influenza viruses (AIVs) has led to significant avian mortality globally. Since 2020, frequent human-animal interactions have been documented. To gain insight into the novel H5 subtype AIVs (i.e., H5N1, H5N6 and H5N8), we collected 6102 samples from various regions of China between January 2021 and September 2022, and identified 41 H5Nx strains. Comparative analyses on the evolution and biological properties of these isolates were conducted. Phylogenetic analysis revealed that the 41 H5Nx strains belonged to clade 2.3.4.4b, with 13 related to H5N1, 19 to H5N6, and 9 to H5N8. Analysis based on global 2.3.4.4b viruses showed that all the viruses described in this study were likely originated from H5N8, exhibiting a heterogeneous evolutionary history between H5N1 and H5N6 during 2015–2022 worldwide. H5N1 showed a higher rate of evolution in 2021–2022 and more sites under positive selection pressure in 2015–2022. The antigenic profiles of the novel H5N1 and H5N6 exhibited notable variations. Further hemagglutination inhibition assay suggested that some A(H5N1) viruses may be antigenically distinct from the circulating H5N6 and H5N8 strains. Mammalian challenge assays demonstrated that the H5N8 virus (21GD001_H5N8) displayed the highest pathogenicity in mice, followed by the H5N1 virus (B1557_H5N1) and then the H5N6 virus (220086_H5N6), suggesting a heterogeneous virulence profile of H5 AIVs in the mammalian hosts. Based on the above results, we speculate that A(H5N1) viruses have a higher risk of emergence in the future. Collectively, these findings unveil a new landscape of different evolutionary history and biological characteristics of novel H5 AIVs in clade 2.3.4.4b, contributing to a better understanding of designing more effective strategies for the prevention and control of novel H5 AIVs.