Guinea Pig Animal Model Research Articles

Mannose-Functionalized Isoniazid-Loaded Nanostructured Lipid Carriers for Pulmonary Delivery: In Vitro Prospects and In Vivo Therapeutic Efficacy Assessment.

Resistance to isoniazid (INH) is common and increases the possibility of acquiring multidrug-resistant tuberculosis. For this study, isoniazid-loaded nanostructured lipid carriers (INH-NLCs) were developed and effectively functionalized with mannose (Man) to enhance the residence time of the drug within the lungs via specific delivery and increase the therapeutic efficacy of the formulation. The mannose-functionalized isoniazid-loaded nanostructured lipid carrier (Man-INH-NLC) formulation was evaluated with respect to various formulation parameters, namely, encapsulation efficiency (EE), drug loading (DL), average particle size (PS), zeta potential (ZP), polydispersity index (PDI), in vitro drug release (DR), and release kinetics. The in vitro inhalation behavior of the developed formulation after nebulization was investigated using an Andersen cascade impactor via the estimation of the mass median aerosolized diameter (MMAD) and geometric aerodynamic diameter (GAD) and subsequently found to be suitable for effective lung delivery. An in vivo pharmacokinetic study was carried out in a guinea pig animal model, and it was demonstrated that Man-INH-NLC has a longer residence time in the lungs with improved pharmacokinetics when compared with unfunctionalized INH-NLC, indicating the enhanced therapeutic efficacy of the Man-INH-NLC formulation. Histopathological analysis led us to determine that the extent of tissue damage was more severe in the case of the pure drug solution of isoniazid compared to the Man-INH-NLC formulation after nebulization. Thus, the nebulization of Man-INH-NLC was found to be safe, forming a sound basis for enhancing the therapeutic efficacy of the drug for improved management in the treatment of pulmonary tuberculosis.

Cough response in specific pathogen-free guinea pig animal model

Laboratory animal science associations recommend the usage of specific pathogen-free (SPF) animals in experiments to achieve appropriate results. However, their non-natural microbiome might represent an obstacle in the successful translation of obtained results into clinical practice, since the microbiome contributes to the regulation of the host’s physiology. Inconsistent results, even in repeated experiments in separate animal groups, irrespective of the season or sex led us to assess the cough response of SPF animal variables and compare it to wild-type animals. The dose-response curves in citric acid and capsaicin cough challenge construction shows significantly increased cough threshold in SPF animals compared to wild-type animals of both sexes. The cause of cough response alteration in SPF animals is not presently known and thus their usage in basic cough research remains questionable. The relationship between airway reflexes and the airway microbiome has never been studied hence we propose that it might be microbiome-related.

Analysis of Bone Histomorphometry in Rat and Guinea Pig Animal Models Subject to Hypoxia.

Hypoxia may be associated with alterations in bone remodeling, but the published results are contradictory. The aim of this study was to characterize the bone morphometry changes subject to hypoxia for a better understanding of the bone response to hypoxia and its possible clinical consequences on the bone metabolism. This study analyzed the bone morphometry parameters by micro-computed tomography (μCT) in rat and guinea pig normobaric hypoxia models. Adult male and female Wistar rats were exposed to chronic hypoxia for 7 and 15 days. Additionally, adult male guinea pigs were exposed to chronic hypoxia for 15 days. The results showed that rats exposed to chronic constant and intermittent hypoxic conditions had a worse trabecular and cortical bone health than control rats (under a normoxic condition). Rats under chronic constant hypoxia were associated with a more deteriorated cortical tibia thickness, trabecular femur and tibia bone volume over the total volume (BV/TV), tibia trabecular number (Tb.N), and trabecular femur and tibia bone mineral density (BMD). In the case of chronic intermittent hypoxia, rats subjected to intermittent hypoxia had a lower cortical femur tissue mineral density (TMD), lower trabecular tibia BV/TV, and lower trabecular thickness (Tb.Th) of the tibia and lower tibia Tb.N. The results also showed that obese rats under a hypoxic condition had worse values for the femur and tibia BV/TV, tibia trabecular separation (Tb.Sp), femur and tibia Tb.N, and BMD for the femur and tibia than normoweight rats under a hypoxic condition. In conclusion, hypoxia and obesity may modify bone remodeling, and thus bone microarchitecture, and they might lead to reductions in the bone strength and therefore increase the risk of fragility fracture.

Evaluating the Immunogenicity of recombinant VP1 protein from the foot-and-mouth disease virus encapsulated in nanoliposome in guinea pig animal model

Foot-and-mouth disease (FMD) is considered as contagious in livestock, which is caused by the Picornavridae virus family known as FMD virus (FMDV). In the present study, the VP1 gene from FMDV (O strain) was expressed and purified. In addition, nanoliposomes were utilized as an adjuvant. After formulating the nanoliposomes with DMPC, DMPG, and cholesterol, the recombinant VP1 protein was encapsulated in the nanoliposomes. Further, the intended nanoliposomes in the sizes of 400 and 200 nm, nanoliposome-inactivated FMDV, Freund's adjuvant-inactivated FMDV, and Freund's adjuvant-recombinant VP1 mixtures, and PBS buffer (negative control) were injected to six groups of five guinea pigs. Furthermore, the guinea pig serums were analyzed through using ELISA and serum neutralization tests after four boosting vaccinations. Based on the results, the immunogenicity of the 200 nm-nanoliposomes encapsulating recombinant VP1 protein was more than that of 400 nm-ones so that 200 nm-nanoliposomes could trigger the immune response against FMDV in guinea pigs.

Updates to the guinea pig animal model for in-vivo auditory neuroscience in the low-frequency hearing range

For gaining insight into general principles of auditory processing, it is critical to choose model organisms whose set of natural behaviors encompasses the processes being investigated. This reasoning has led to the development of a variety of animal models for auditory neuroscience research, such as guinea pigs, gerbils, chinchillas, rabbits, and ferrets; but in recent years, the availability of cutting-edge molecular tools and other methodologies in the mouse model have led to waning interest in these unique model species. As laboratories increasingly look to include in-vivo components in their research programs, a comprehensive description of procedures and techniques for applying some of these modern neuroscience tools to a non-mouse small animal model would enable researchers to leverage unique model species that may be best suited for testing their specific hypotheses. In this manuscript, we describe in detail the methods we have developed to apply these tools to the guinea pig animal model to answer questions regarding the neural processing of complex sounds, such as vocalizations. We describe techniques for vocalization acquisition, behavioral testing, recording of auditory brainstem responses and frequency-following responses, intracranial neural signals including local field potential and single unit activity, and the expression of transgenes allowing for optogenetic manipulation of neural activity, all in awake and head-fixed guinea pigs. We demonstrate the rich datasets at the behavioral and electrophysiological levels that can be obtained using these techniques, underscoring the guinea pig as a versatile animal model for studying complex auditory processing. More generally, the methods described here are applicable to a broad range of small mammals, enabling investigators to address specific auditory processing questions in model organisms that are best suited for answering them.

A putative short-chain dehydrogenase Rv0148 of Mycobacterium tuberculosis affects bacterial survival and virulence.

During infection, Mycobacterium tuberculosis combats the stress generated by the host cells through the action of short-chain dehydrogenases/reductases (SDRs). Rv0148 belongs to the oxidoreductase family with the SDRs domain, which regulates the homeostasis of M. tuberculosis. In our earlier studyusing knockout mutant strain (∆0148), we reported that Rv0148 is involved in intermediary metabolism, drug resistance and cell homeostasis of M. tuberculosis. In the current study, we explored the functional role of Rv0148 using gene knockout mutant in-vitro and in-vivo models of infection. We report the ∆0148 is attenuated for virulence of M. tuberculosis. During human monocyte (THP-1) cell line infection, M. tuberculosis Δ0148 displayed reduced intracellular survival compared to the wild type at successive time points. Similarly, in a guinea pig animal model of aerosol infection, Δ0148 displayed a growth attenuation at 5- and 10-week post-infection in the lungs and spleen compared to the wild-type M. tuberculosis and Rv0148-complemented Δ0148 strains. Our study suggest that Rv0148 has a distinct role in the intracellular virulence of M. tuberculosis.

Effects of water-filtered infrared A and visible light (wIRA/VIS) radiation on heat- and stress-responsive proteins in the retina and cornea of guinea pigs.

Water-filtered infrared A and visible light (wIRA/VIS), shown to reduce chlamydial infections in vitro and in vivo, might represent an innovative therapeutic approach against trachoma, a neglected tropical disease caused by ocular infection with the bacterium C. trachomatis. In this in vivo study, we assessed the impact of wIRA radiation in combination with VIS (wavelength range 595-1400 nm, intensity 2100 W/m2) on the retina and cornea in a guinea pig animal model of inclusion conjunctivitis. We investigated the effects 19 days after wIRA/VIS irradiation by comparing a single and double wIRA/VIS treatment with a sham control. By immunolabeling and western blot analyses of critical heat- and stress-responsive proteins, we could not detect wIRA/VIS-induced changes in their expression pattern. Also, immunolabeling of specific retinal marker proteins revealed no changes in their expression pattern caused by the treatment. Our preclinical study suggests wIRA/VIS as a promising and safe therapeutic tool to treat ocular chlamydial infections.

Estimating the Pose of a Guinea-pig Cochlea Without Medical Imaging.

The pose (i.e., position and orientation) of a guinea-pig cochlea can be accurately estimated using externally observable features, without requiring computed-tomography (CT) scans. Guinea pigs are frequently used in otologic research as animal models of cochlear-implant surgery. In robot-assisted surgical insertion of cochlear-implant electrode arrays, knowing the cochlea pose is required. A preoperative CT scan of the guinea-pig anatomy can be labeled and registered to the surgical system, however, this process can be expensive and time consuming. Anatomical features from both sides of 11 guinea-pig CT scans were labeled and registered, forming sets. Using a groupwise point-set registration algorithm, errors in cochlea position and modiolar-axis orientation were estimated for 11 iterations of registration where each feature set was used as a hold-out set containing a reduced number of features that could all be touched by a motion-tracking probe intraoperatively. The method was validated on 2000 simulated guinea-pig cochleae and six physical guinea-pig-skull cochleae. Validation on simulated cochleae resulted in cochlea-position estimates with a maximum error of 0.43 mm and modiolar-axis orientation estimates with a maximum error of 8.1 degrees for 96.7% of cochleae. Physical validation resulted in cochlea-position estimates with a maximum error of 0.80 mm and modiolar-axis orientation estimates with a maximum error of 12.4 degrees. This work enables researchers conducting robot-assisted surgical insertions of cochlear-implant electrode arrays using a guinea-pig animal model to estimate the pose of a guinea-pig cochlea by locating six externally observable features on the guinea pig, without the need for CT scans.

Assessment of the Pathogenicity of Rickettsia amblyommatis, Rickettsia bellii, and Rickettsia montanensis in a Guinea Pig Model.

Members of the genus Rickettsia range from nonpathogenic endosymbionts to virulent pathogens such as Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever. Many rickettsiae are considered nonpathogenic because they have been isolated from ticks but not vertebrate hosts. We assessed the ability of three presumed endosymbionts: Rickettsia amblyommatis, Rickettsia bellii, and Rickettsia montanensis, to infect a guinea pig animal model. These species were chosen because of their high prevalence in respective tick vectors or published reports suggestive of human or animal pathogenicity. Following intraperitoneal (IP) inoculation of cell culture suspensions of R. rickettsii, R. amblyommatis, R. bellii, or R. montanensis into guinea pigs, animals were monitored for signs of clinical illness for 13 days. Ear biopsies and blood samples were taken at 2- to 3-day intervals for detection of rickettsial DNA by PCR. Animals were necropsied and internal organ samples were also tested using PCR assays. Among the six guinea pigs inoculated with R. amblyommatis, fever, orchitis, and dermatitis were observed in one, one, and three animals respectively. In R. bellii-exposed animals, we noted fever in one of six animals, orchitis in one, and dermatitis in two. No PCR-positive tissues were present in either the R. amblyommatis- or R. bellii-exposed groups. In the R. montanensis-exposed group, two of six animals became febrile, two had orchitis, and three developed dermatitis in ears or footpads. R. montanensis DNA was detected in ear skin biopsies collected on multiple days from three animals. Also, a liver specimen from one animal and spleen specimens of two animals were PCR positive. The course and severity of disease in the three experimental groups were significantly milder than that of R. rickettsii. This study suggests that the three rickettsiae considered nonpathogenic can cause either subclinical or mild infections in guinea pigs when introduced via IP inoculation.

Lipopolysaccharide decreases cochlear blood flow dose dependently in a guinea pig animal model via TNF signaling.

To evaluate the effect of Lipopolysaccharide (LPS), a bacterial endotoxin on cochlear microcirculation, and its mode of action. Twenty-five Dunkin-Hartley guinea pigs were divided into five groups of five animals each. After surgical preparation, cochlear microcirculation was quantified by in vivo fluorescence microscopy. Placebo or LPS (1mg, 10µg, and 100ng) was applied topically, and microcirculation was measured before and twice after application. A fifth group was pretreated with etanercept, a tumor necrosis factor (TNF) antagonist, and afterward the lowest LPS concentrations that yielded significant results (10µg) were applied. In the groups that had been treated with 1mg and 10µg LPS, a significant drop in cochlear microcirculation was observed after 30 (.791±.089 Arbitrary Units (AU), compared to baseline, and .888±.071AU) and 60 (.756±.101 AU and .817±.124 AU, respectively) minutes. The groups that had been treated with 100ng LPS and that had been pretreated with etanercept showed no significant change in cochlear blood flow compared to placebo. Lipopolysaccharide shows a dose-dependent effect on cochlear microcirculation; this effect can already be observed after 30min. Pretreatment with etanercept can abrogate this effect, indicating that TNF mediates the effect of LPS on cochlear microcirculation.

Diabetes Increases the Vulnerability of the Cardiac Mitochondrial Network to Criticality.

Mitochondrial criticality describes a state in which the mitochondrial cardiac network under intense oxidative stress becomes very sensitive to small perturbations, leading from local to cell-wide depolarization and synchronized oscillations that may escalate to the myocardial syncytium generating arrhythmias. Herein, we describe the occurrence of mitochondrial criticality in the chronic setting of a metabolic disorder, type 1 diabetes (T1DM), using a streptozotocin (STZ)-treated guinea pig (GP) animal model. Using wavelet analysis of mitochondrial networks from two-photon microscopy imaging of cardiac myocytes loaded with a fluorescent probe of the mitochondrial membrane potential, we show that cardiomyocytes from T1DM GPs are closer to criticality, making them more vulnerable to cell-wide mitochondrial oscillations as can be judged by the latency period to trigger oscillations after a laser flash perturbation, and their propensity to oscillate. Insulin treatment of T1DM GPs rescued cardiac myocytes to sham control levels of susceptibility, a protective condition that could also be attained with interventions leading to improvement of the cellular redox environment such as preincubation of diabetic cardiac myocytes with the lipid palmitate or a cell-permeable form of glutathione, in the presence of glucose.

Altered pulmonary capillary permeability in immunosuppressed guinea pigs infected with Legionella pneumophila serogroup 1.

In immunosuppressed hosts, Legionella pneumophila (Lp) infection usually develops into severe pneumonia, which is pathologically characterized by increased vascular permeability and pulmonary edema. At present, mechanisms associated with changes in pulmonary capillary permeability (PCP) and the pathogenesis of pulmonary edema in immunosuppressed hosts with Lp infection are unclear. Therefore, in the present study an animal model of normal and immunosuppressed guinea pigs infected with Lp was established. An isolated perfused lung system was used to investigate the extent of changes in PCP. Pathological and immunofluorescence examinations were performed to explore the mechanism underlying these changes. The results indicated that PCP increased with the highest magnitude in immunosuppressed guinea pigs infected with Lp, with repeated ANOVA indicating synergism between infection and immunosuppression (P=0.0444). Hematoxylin and eosin staining and electron microscopy revealed more severe morphological damages in the lung tissues and pulmonary capillaries of the immunosuppressed animals infected with Lp compared with normal animals infected with Lp. Immunofluorescence analysis showed that immunosuppression reduced the expression of the vascular endothelial cell junction protein VE-cadherin (P=0.027). Following Lp infection, VE-cadherin expression was significantly lower in the immunosuppressed guinea pigs compared with their immunocompetent counterparts (P=0.001). These results suggest that immunosuppression combined with Lp infection induces more significant damage to pulmonary capillaries compared with Lp infection alone, resulting in a significantly increased PCP.

Expression of CD63 in Lung Tissue of Guinea Pigs Dying of Anaphylactic Shock.

Objective To study the protein expression of cluster of differentiation 63 （CD63） in lung tissues of guinea pigs that died of anaphylactic shock and discuss the diagnostic value of CD63 for death from anaphylactic shock. Methods Twenty guinea pigs were randomly divided into control group, anaphylactic shock immediate death group, cold storage group （4 ℃ for 48 h） and frozen group （-20 ℃ for 7 d）. The animal model of guinea pigs that died of anaphylactic shock was established with human mixed serum injection. The expression changes of CD63 protein and CD63 mRNA in lung tissues were detected by hematoxylin-eosin （HE） staining, immunohistochemical staining, Western blotting, enzyme-linked immunosorbent assay （ELISA） and real-time RT-PCR. Results HE staining results showed congestion, and edema of lung tissues, and eosinophil infiltration in the anaphylactic shock groups. Western blotting analysis results showed that the expression of CD63 protein in the lung tissues of guinea pigs that died of anaphylactic shock was significantly higher than that in the control group （P<0.05）. Comparison between the anaphylactic shock groups was made, and the differences had no statistical significance. The results of immunohistochemical staining and real-time RT-PCR were consistent with that of Western blotting. ELISA results showed that CD63 protein expression in the immediate death group was higher than that in the control group （P<0.05）. Conclusion The expression of CD63 protein and CD63 mRNA in the lung tissues of guinea pigs that died of anaphylactic shock is significantly enhanced. Animal carcasses which were put in cold storage for 48 h and frozen for 7 d do not affect the examination of the above indicators. CD63 protein is expected to become an auxiliary diagnostic indicator of death from anaphylactic shock.

A Physicochemical Assessment of Acid-induced Post-inhalation Cough in a Guinea Pig Animal Model

A study was conducted with a Guinea Pig (GP) cough model to demonstrate that post-inhalation (PI) cough can be correlated and predicted with the acidity constant of the chemical stimulant. The test animals were exposed to nebulized solutions of citric acid and maleic acid. Cough responses were measured by audio, video, and respiratory flow signals via whole-body plethysmography. Nonparametric one-way ANOVA (Kruskal-Wallis) of cough counts showed statistically significant dose dependence for both citric acid (p<0.0001) and maleic acid (p<0.0001). For citric acid, post-hoc Dunn’s test indicated elevated cough response at the higher concentrations (p ≤ 0.0001 for 200 mM, and 300 mM) compared to control, i.e., isotonic saline (SL). The cough count at 100 mM citric acid was not significantly different from SL (p>0.05). Similar results were obtained for maleic acid exposures, with cough response at the higher concentrations significantly different compared to SL (p=0.0039 for 50 mM, p<0.0001 for 100 mM), while cough counts at 30 mM were not different compared to SL. The GP model is able to differentiate the cough response of maleic acid vs. citric acid, and the threshold of cough (1-2 coughs in 2 min) for maleic acid (~30 mM) is lower than that for citric acid (~100 mM). The lower threshold of cough for maleic acid as compared to citric acid is consistent with the mechanism of action mediated by protons, in a dose dependent way. A prediction of the cough response from citric acid to maleic acid was confirmed by this study. Experiments with nebulized acids confirmed expectations that the threshold of cough for citric acid in GP is at 100 mM and for maleic acid at 10- 30 mM. The lower cough threshold for maleic vs. citric acid is consistent with proton-mediated mechanism of action.

Development of an Animal Model for Inducing Various Degrees of Severity of Incontinence-Associated Dermatitis.

The purpose of this study was to describe the biological changes after incontinence-associated dermatitis (IAD) induction by pancreatin in the guinea pigs and to explore the potentially appropriate timing and pancreatin concentration for IAD induction with different severity. In vivo, experimental study. An experimental animal model (guinea pig) in a controlled laboratory setting was used for investigation. We developed an IAD model in guinea pigs by occluded application of 1%, 5%, and 10% pancreatin solutions for 1, 3, and 5 days, respectively. The irritant was applied to the posterior aspect of shaved guinea pigs. We used an adapted visual scoring system to evaluate IAD and its severity. We also measured differences of the fluid absorption rate as a proxy for transepidermal water loss and enzyme-linked immunosorbent assays of interleukin 2 and interferon-γ expression as indicators of IAD-related inflammation. Analysis of variance (ANOVA) was used to examine group differences. Higher pancreatin concentrations led to more severe skin responses and higher mean visual scale scores, yet the statistically score differences were only observed in the 1% and 5% pancreatin groups after 3 and 5 days of exposure compared with 1 day of exposure (P < .05). The average absorbed fluid rate increased from 1 to 3 days of exposure and reached a plateau at 3 days; significant differences were observed in 3 and 5 days of exposure (P < .05) when compared with 1 day of exposure but not between 3 and 5 days of exposure. Exposure of a guinea pig animal model to 1%, 5%, and 10% pancreatin solutions over a 3-day period induced IAD with different levels of severity. Additional studies using this model are warranted.

The effect of infectious dose on humoral and cellular immune responses in Chlamydophila caviae primary ocular infection.

Following infection, the balance between protective immunity and immunopathology often depends on the initial infectious load. Several studies have investigated the effect of infectious dose; however, the mechanism by which infectious dose affects disease outcomes and the development of a protective immune response is not known. The aim of this study was to investigate how the infectious dose modulates the local and systemic humoral and the cellular immune responses during primary ocular chlamydial infection in the guinea pig animal model. Guinea pigs were infected by ocular instillation of a Chlamydophila caviae-containing eye solution in the conjunctival sac in three different doses: 1×102, 1×104, and 1×106 inclusion forming units (IFUs). Ocular pathology, chlamydial clearance, local and systemic C. caviae-specific humoral and cellular immune responses were assessed. All inocula of C. caviae significantly enhanced the local production of C. caviae-specific IgA in tears, but only guinea pigs infected with the higher doses showed significant changes in C. caviae-specific IgA levels in vaginal washes and serum. On complete resolution of infection, the low dose of C. caviae did not alter the ratio of CD4+ and CD8+ cells within guinea pigs’ submandibular lymph node (SMLN) lymphocytes while the higher doses increased the percentages of CD4+ and CD8+ cells within the SMLN lymphocytes. A significant negative correlation between pathology intensity and the percentage of CD4+ and CD8+ cells within SMLN lymphocyte pool at selected time points post-infection was recorded for both 1×104, and 1×106 IFU infected guinea pigs. The relevance of the observed dose-dependent differences on the immune response should be further investigated in repeated ocular chlamydial infections.

Whole transcriptomic and proteomic analyses of an isogenic M. tuberculosis clinical strain with a naturally occurring 15 Kb genomic deletion.

Tuberculosis remains one of the most difficult to control infectious diseases in the world. Many different factors contribute to the complexity of this disease. These include the ability of the host to control the infection which may directly relate to nutritional status, presence of co-morbidities and genetic predisposition. Pathogen factors, in particular the ability of different Mycobacterium tuberculosis strains to respond to the harsh environment of the host granuloma, which includes low oxygen and nutrient availability and the presence of damaging radical oxygen and nitrogen species, also play an important role in the success of different strains to cause disease. In this study we evaluated the impact of a naturally occurring 12 gene 15 Kb genomic deletion on the physiology and virulence of M. tuberculosis. The strains denominated ON-A WT (wild type) and ON-A NM (natural mutant) were isolated from a previously reported TB outbreak in an inner city under-housed population in Toronto, Canada. Here we subjected these isogenic strains to transcriptomic (via RNA-seq) and proteomic analyses and identified several gene clusters with differential expression in the natural mutant, including the DosR regulon and the molybdenum cofactor biosynthesis genes, both of which were found in lower abundance in the natural mutant. We also demonstrated lesser virulence of the natural mutant in the guinea pig animal model. Overall, our findings suggest that the ON-A natural mutant is less fit to cause disease, but nevertheless has the potential to cause extended transmission in at-risk populations.

Drug-induced Defibrinogenation as New Treatment Approach of Acute Hearing Loss in an Animal Model for Inner Ear Vascular Impairment.

Disturbance of cochlear microcirculation is considered to be the final common pathway of various inner ear diseases. Hyperfibrinogenemia causing increased plasma viscosity is a known risk factor for sudden sensorineural hearing loss and may lead to a critical reduction of cochlear blood flow. The aim of this study was to evaluate the effect of a substantial reduction of plasma fibrinogen levels by drug-induced defibrinogenation for the treatment of acute hearing loss in vivo. Acute hearing loss was induced by hyperfibrinogenemia (i.v. injection of 330 mg/kg BW fibrinogen), using a guinea pig animal model. Parameters of cochlear microcirculation and hearing thresholds were quantified by intravital microscopy and evoked response audiometry. After obtaining baseline values, the course of hearing loss and disturbances of microcirculation were investigated under influence of intravenous defibrinogenation therapy (ancrod), corticosteroid, or placebo treatment, using 5 animals/group. Acute hyperfibrinogenemia caused hearing loss from 10 ± 7 to 26 ± 10 dB SPL at baseline. Drug-induced reduction of fibrinogen levels showed a significant increase of cochlear microcirculation (1.6-fold) and recovered hearing threshold (11 ± 6 dB SPL). Placebo or corticosteroid treatment had no effect on hearing loss (35 ± 7 dB SPL and 32 ± 18 dB SPL, respectively). Acute hyperfibrinogenemia resulted in hearing loss. Drug-induced reduction of elevated fibrinogen levels caused an increase in cochlear blood flow and a decrease in hearing thresholds. Placebo or corticosteroid treatment had no effect. Reduction of plasma fibrinogen levels could serve as a clinical treatment option for acute hearing loss.

A novel live attenuated anthrax spore vaccine based on an acapsular Bacillus anthracis Sterne strain with mutations in the htrA, lef and cya genes.

We recently reported the development of a novel, next-generation, live attenuated anthrax spore vaccine based on disruption of the htrA (High Temperature Requirement A) gene in the Bacillus anthracis Sterne veterinary vaccine strain. This vaccine exhibited a highly significant decrease in virulence in murine, guinea pig and rabbit animal models yet preserved the protective value of the parental Sterne strain. Here, we report the evaluation of additional mutations in the lef and cya genes, encoding for the toxin components lethal factor (LF) and edema factor (EF), to further attenuate the SterneΔhtrA strain and improve its compatibility for human use. Accordingly, we constructed seven B. anthracis Sterne-derived strains exhibiting different combinations of mutations in the htrA, cya and lef genes. The various strains were indistinguishable in growth in vitro and in their ability to synthesise the protective antigen (PA, necessary for the elicitation of protection). In the sensitive murine model, we observed a gradual increase (ΔhtrA<ΔhtrAΔcya<ΔhtrAΔlef<ΔhtrAΔlefΔcya) in attenuation - up to 108-fold relative to the parental Sterne vaccine strain. Most importantly, all various SterneΔhtrA derivative strains did not differ in their ability to elicit protective immunity in guinea pigs. Immunisation of guinea pigs with a single dose (109 spores) or double doses (>107spores) of the most attenuated triple mutant strain SterneΔhtrAlefMUTΔcya induced a robust immune response, providing complete protection against a subsequent respiratory lethal challenge. Partial protection was observed in animals vaccinated with a double dose of as few as 105spores. Furthermore, protective immune status was maintained in all vaccinated guinea pigs and rabbits for at least 40 and 30weeks, respectively.

Pregnancy-related listeriosis.

About one in seven cases of listeriosis occurs in pregnant women, and, although listeriosis is rare, it is the third leading cause of death from food-borne infections. Pregnancy-related listeriosis increases the risk for fetal and neonatal mortality by approximately 21%. During pregnancy, infections are more likely to occur in the third trimester (66%) than the first trimester (3%). However, fetal and neonatal adverse effects are less common as gestational age increases or with older gestational age at birth. Pregnant women seem highly susceptible in some listeriosis outbreaks making up a large percentage of cases, whereas others contain very few. Whether this results from differences in strains of L. monocytogenes, exposures, or other factors remains to be determined. Food and Agriculture Organization of United Nations/World Health Organization (FAO/WHO) estimates the human lethal dose for 50% (LD50 ) for fetal/neonatal loss is 1.9 × 106 colony forming units (CFUs) L. monocytogenes. Animal models have been developed for pregnancy-related listeriosis showing similar susceptibility and clinical outcomes as in humans. Nonhuman primate and guinea pig animal models have similar (LD50 ) values to the estimated human LD50 . Additional animal studies are needed to understand the pathways leading to fetal and neonatal listeriosis in humans. More information is needed to understand dose response, to model risk for listeriosis at lower concentrations, and to determine why some pregnant women may be more susceptible than others. To better treat listeriosis during pregnancy, biomarkers for early diagnosis of listeriosis are also needed. Last, pregnant women need to be educated about avoiding high-risk foods, like Mexican-style cheese and ready-to-eat meats. Birth Defects Research 109:324-335, 2017.© 2017 Wiley Periodicals, Inc.