Evaluation of the PrimeFlow RNA assay as a method of detection of SARS-CoV-2 single and dual Infections

Given the implications of increased transmissibility, virulence, host range, and immune escapes of emerging variants of SARS-CoV-2, developing in vitro models that allow for detection of variants and differences in infection dynamics is important. The objective of this study, was to evaluate the PrimeFlow RNA in-situ assay as a method of detection for multiple strains of SARS-CoV-2. Evaluation of detection and infection statuses included single infections with an Alpha, Delta, or Omicron variants and dual infections with Alpha/Omicron or Delta/Omicron. RNA probes specific for the Spike protein coding region, were designed (omicron or non-omicron specific). SARS-CoV-2 RNA was detected in greater frequency in the Vero E6 and minimally in the fetal deer testicle cell lines by flow cytometry using this approach for viral detection of multiple variants. Most evident in the Vero E6 cells, 24 h post infection both Alpha and Delta predominated over Omicron in dual infections. This is the first report using the PrimeFlow assay for the detection of SARS-CoV-2 at the single-cell level and as a potential model for competition of variants utilizing infection dynamics in cell culture.

Effect of selection genotype on immune response to Brucella abortus RB51 in Holstein cattle

Genetic selection for milk production traits in US Holsteins has affected numerous genes associated with reproduction and immunity. This study compares the transcriptomic response of peripheral blood mononuclear cells to an in vitro Brucella abortus strain RB51 (RB51) bacterial challenge between contemporary Holsteins and Holsteins that have not been selected for milk production traits since the mid-1960s. Total RNA was extracted from peripheral blood mononuclear cells from four contemporary and four unselected lactating, primiparous cows following 24-h incubation with or without stimulation with RB51 bacteria. RNA was sequenced and reads analyzed using tools from galaxy.scinet.usda.gov. A total of 412 differentially expressed genes (false discovery rate p < 0.05, log fold change > |1|) were identified. The upregulated genes (genes with higher expression in contemporary than unselected cattle) were enriched for 19 terms/pathways, including alanine, aspartate, and glutamate metabolism, indicating a cellular stress response. Downregulated genes (genes with higher expression in unselected than contemporary cows) were enriched for 37 terms/pathways, representing diverse immune responses, including natural killer cell-mediated immunity, interferon-γ production, negative regulation of interleukin-10 production, and cytokine receptor activity indicating a broad immune response with an emphasis on immune defense. These results provide evidence that differences exist between the two genotypes in response to in vitro bacterial challenge. This suggests that contemporary cows, genetically selected for milk production, may have reduced immune function, including limitations in response to intracellular bacteria.

The Many Hosts of Mycobacteria 9 (MHM9): A conference report

The Many Hosts of Mycobacteria (MHM) meeting series brings together basic scientists, clinicians and veterinarians to promote robust discussion and dissemination of recent advances in our knowledge of numerous mycobacterial diseases, including human and bovine tuberculosis (TB), nontuberculous mycobacteria (NTM) infection, Hansen's disease (leprosy), Buruli ulcer and Johne's disease. The 9th MHM conference (MHM9) was held in July 2022 at The Ohio State University (OSU) and centered around the theme of "Confounders of Mycobacterial Disease." Confounders can and often do drive the transmission of mycobacterial diseases, as well as impact surveillance and treatment outcomes. Various confounders were presented and discussed at MHM9 including those that originate from the host (comorbidities and coinfections) as well as those arising from the environment (e.g., zoonotic exposures), economic inequality (e.g. healthcare disparities), stigma (a confounder of leprosy and TB for millennia), and historical neglect (a confounder in Native American Nations). This conference report summarizes select talks given at MHM9 highlighting recent research advances, as well as talks regarding the historic and ongoing impact of TB and other infectious diseases on Native American Nations, including those in Southwestern Alaska where the regional TB incidence rate is among the highest in the Western hemisphere.

A pseudomolecule assembly of the Rocky Mountain elk genome

Rocky Mountain elk (Cervus canadensis) populations have significant economic implications to the cattle industry, as they are a major reservoir for Brucella abortus in the Greater Yellowstone area. Vaccination attempts against intracellular bacterial diseases in elk populations have not been successful due to a negligible adaptive cellular immune response. A lack of genomic resources has impeded attempts to better understand why vaccination does not induce protective immunity. To overcome this limitation, PacBio, Illumina, and Hi-C sequencing with a total of 686-fold coverage was used to assemble the elk genome into 35 pseudomolecules. A robust gene annotation was generated resulting in 18,013 gene models and 33,422 mRNAs. The accuracy of the assembly was assessed using synteny to the red deer and cattle genomes identifying several chromosomal rearrangements, fusions and fissions. Because this genome assembly and annotation provide a foundation for genome-enabled exploration of Cervus species, we demonstrate its utility by exploring the conservation of immune system-related genes. We conclude by comparing cattle immune system-related genes to the elk genome, revealing eight putative gene losses in elk.

Loci Associated With Antibody Response in Feral Swine (Sus scrofa) Infected With Brucella suis

Feral swine (Sus scrofa) are a destructive invasive species widespread throughout the United States that disrupt ecosystems, damage crops, and carry pathogens of concern for the health of domestic stock and humans including Brucella suis-the causative organism for swine brucellosis. In domestic swine, brucellosis results in reproductive failure due to abortions and infertility. Contact with infected feral swine poses spillover risks to domestic pigs as well as humans, companion animals, wildlife, and other livestock. Genetic factors influence the outcome of infectious diseases; therefore, genome wide association studies (GWAS) of differential immune responses among feral swine can provide an understanding of disease dynamics and inform management to prevent the spillover of brucellosis from feral swine to domestic pigs. We sought to identify loci associated with differential antibody responses among feral swine naturally infected with B. suis using a case-control GWAS. Tissue, serum, and genotype data (68,516 bi-allelic single nucleotide polymorphisms) collected from 47 feral swine were analyzed in this study. The 47 feral swine were culture positive for Brucella spp. Of these 47, 16 were antibody positive (cases) whereas 31 were antibody negative (controls). Single-locus GWAS were performed using efficient mixed-model association eXpedited (EMMAX) methodology with three genetic models: additive, dominant, and recessive. Eight loci associated with seroconversion were identified on chromosome 4, 8, 9, 10, 12, and 18. Subsequent bioinformatic analyses revealed nine putative candidate genes related to immune function, most notably phagocytosis and induction of an inflammatory response. Identified loci and putative candidate genes may play an important role in host immune responses to B. suis infection, characterized by a detectable bacterial presence yet a differential antibody response. Given that antibody tests are used to evaluate brucellosis infection in domestic pigs and for disease surveillance in invasive feral swine, additional studies are needed to fully understand the genetic component of the response to B. suis infection and to more effectively translate estimates of Brucella spp. antibody prevalence among feral swine to disease control management action.

Immune responses and clinical effects of experimental challenge of elk with Brucella abortus strain 2308

To assess the effects of challenge dose and stage of gestation on infection and abortion, 35 elk were conjunctivally challenged with virulent Brucella abortus strain 2308 (S2308) during pregnancy. Seventeen elk were experimentally challenged early in the second trimester of gestation (December) with high (approximately 10⁸ CFU) or low challenge (approximately 10⁷ CFU) treatments having 8 and 9 pregnant elk, respectively. Other pregnant elk were experimentally challenged at a later challenge time (approximately early third trimester, February), with high and low challenge treatments having 8 and 10 elk, respectively. Conjunctival swabs from all animals were culture positive for the S2308 strain at 7 days after experimental challenge. All animals seroconverted on a B. abortus ELISA but optical density readings were not influenced (P > 0.05) by time of challenge or by challenge dosage. In the early challenge group, abortions occurred in 2 of 9 (22%) in the low challenge treatment and 3 of 8 (37%) in the high challenge treatment, whereas in the later challenge group, 1 of 8 (12.5%) in the low challenge treatment and 2 of 10 (20%) in the high challenge treatment aborted. The ability to recover B. abortus from samples obtained at necropsy did not differ (P > 0.05) between early and late challenges or between high and low challenge treatments. Despite the lack of abortions observed after experimental challenge, recovery from maternal tissues ranged from 50% (low dose, late challenge) to 77% (low dose, early challenge). Our data suggests that naïve elk do not abort as frequently after experimental infection with B. abortus strain 2308 as compared to similar data in cattle and bison.

Bovine immune response to leptospira antigen in different novel adjuvants and vaccine delivery platforms

Leptospirosis is a global zoonosis causing significant economic losses for cattle production. Current cattle vaccines against leptospirosis need improvement to provide efficacy against multiple serovars, reduce shedding in urine, and to induce earlier and more robust immune responses. In this study, Leptospira borgpetersenii serovar Hardjo strain 203 antigen was combined with novel adjuvants (a biodegradable polyanhydride compressed rod implant (VPEAR), poly(diaminosulfide) microparticles, a water-oil-water emulsion adjuvant, and aluminum hydroxide) to develop novel vaccines. Cattle were immunized twice, at a 4 week interval, with inoculums containing adjuvants alone or leptospira antigens and immune responses were compared to responses of cattle receiving a commercial monovalent leptospirosis vaccine (Spirovac). All animals were inoculated with a single dose of Spirovac at 20 weeks to assess antigen recall responses. Serum antibody responses were increased (P > 0.05) at 8 and 20 weeks after vaccination in cattle receiving inoculums containing leptospira antigens combined with water-oil-emulsion, poly(diaminosulfide) microparticles (PNSN-MP), or aluminum hydroxide and in cattle vaccinated with Spirovac. Humoral responses were predominantly IgG1 isotypes. Antigen-specific proliferative responses were detected after initial vaccination in cattle vaccinated with Spirovac, PNSN-MP and water-oil-water treatments. Most proliferative responses occurring within CD4+ and gamma delta T cell populations expressing CD45RO and CD25 markers, a response consistent with an effector memory phenotype. Antigen-specific immune responses were not detected in cattle vaccinated with VPEAR after initial inoculation, but were detected in the antigen recall responses. PBMCs from cattle vaccinated with Spirovac, oil-water-oil, or PNSN-MP treatments had increased (P < 0.05) IL-17A release after in vitro stimulation with leptospirosis antigens, whereas all groups produced IFN-γ and IL-17A after in vitro stimulation during the antigen recall response. Our data demonstrates that combining leptospirosis antigens with these adjuvants enhances immunogenicity in cattle. Interpretative Summary: Vaccination of livestock is a key mechanism for minimizing transmission of leptospirosis, a zoonotic disease. Leptospirosis vaccines for cattle need to be improved to provide greater levels of protection from kidney colonization, better immune responses, and protection against multiple serovars. This could be accomplished using new vaccine adjuvants. In this study, several novel adjuvants were evaluated for their ability to induce effective immune responses in cattle to leptospira antigens as compared to currently available vaccines. Data suggested that vaccines containing biodegradable polymer microparticles and oil-emulsion adjuvants induced similar or greater immune responses as compared to a commercial vaccine. Our data suggest these new vaccine formulations warrant further investigation as new vaccine formulations for cattle and other livestock.

Lung deposition and cellular uptake behavior of pathogen-mimicking nanovaccines in the first 48 hours

Pulmonary immunization poses the unique challenge of balancing vaccine efficacy with minimizing inflammation in the respiratory tract. While previous studies have shown that mice immunized intranasally with F1-V-loaded polyanhydride nanoparticles are protected from a lethal challenge with Yersinia pestis, little is known about the initial interaction between the nanoparticles and immune cells following intranasal administration. Here, the deposition within the lung and internalization by phagocytic cells of polyanhydride nanovaccines encapsulating F1-V are compared with that of soluble F1-V alone or F1-V adjuvanted with monophosphoryl lipid A (MPLA). Encapsulation of F1-V into polyanhydride nanoparticles prolonged its presence while F1-V administered with MPLA is undetectable within 48 h. The inflammation induced by the polyanhydride nanovaccine is mild compared with the marked inflammation induced by the MPLA-adjuvanted F1-V. Even though F1-V delivered with saline is detected in the lung 48 h after administration, it is known that this regimen does not elicit a protective immune response. The prolonged F1-V presence in the lung in concert with the mild inflammatory response provided by the nanovaccine provides new insights into the development of protective immune responses with a single intranasal dose.

CD8 T cell exhaustion is influenced by genetic background (P6076)

Lymphocyte choriomeningitis virus (LCMV) induces a robust CD8 T cell response allowing for viral clearance and limited disease following an acute LCMV Armstrong (Arm) infection in both C57BL/6 (B6) and BALB/c mice. In contrast, infection of B6 mice with LCMV Clone-13 (Cl-13) results in CD8 T cell exhaustion leading to the establishment of a chronic infection. We examined Cl-13 infection of BALB/c mice and observed a does-dependent increase in disease following infection. BALB/c mice infected with either Arm or a low dose of Cl-13 induced a robust NP118-126-specific CD8 T cell response whereas infection with a high dose of Cl-13 significantly blunted the induction of the NP118-126-specific CD8 T cell response. In addition, BALB/c mice infected with a high dose of Cl-13 failed to control the infection with prolonged virus replication in multiple peripheral organs. The more focused immunodominant CD8 T cell response elicited by LCMV in BALB/c versus B6 mice does not appear to account for the increased disease following high dose Cl-13 infection. Cl-13 infected B10.D2 mice exhibit an increased NP118-126-specific CD8 T cell response as compared to BALB/c infected mice. Furthermore, BALB.B mice exhibit a reduced magnitude of CD8 T cells specific to the three immunodominant epitopes as compared to B6 mice. Our results indicate that non-MHC genes influence the rate of CD8 T cell exhaustion and subsequent disease following a chronic Cl-13 infection.