Safety, Tolerability, and Pharmacokinetics of Anti-SARS-CoV-2 Immunoglobulin Intravenous (Human) Investigational Product (COVID-HIGIV) in Healthy Adults: a Randomized, Controlled, Double-Blinded, Phase 1 Study.

Anti-SARS-CoV-2 immunoglobulin (human) investigational product (COVID-HIGIV) is a purified immunoglobulin preparation containing SARS-CoV-2 polyclonal antibodies. This single-center clinical trial aimed to characterize the safety and pharmacokinetics of COVID-HIGIV in healthy, adult volunteers. Participants were enrolled to receive one of three doses of COVID-HIGIV (100, 200, 400 mg/kg) or placebo in a 2:2:2:1 randomization scheme. Between 24 December 2020 and 27 July 2021, 28 participants met eligibility and were randomized with 27 of these 28 (96.4%) being administered either COVID-HIGIV (n = 23) or placebo (n = 4). Only one SAE was observed, and it occurred in the placebo group. A total of 18 out of 27 participants (66.7%) reported 50 adverse events (AEs) overall. All COVID-HIGIV-related adverse events were mild or moderate in severity and transient. The most frequent AEs (>5% of participants) reported in the safety population were headache (n = 6, 22.2%), chills (n = 3, 11.1%), increased bilirubin (n = 2, 7.4%), muscle spasms (n = 2, 7.4%), seasonal allergies (n = 2, 7.4%), pyrexia (n = 2, 7.4%), and oropharyngeal pain (n = 2, 7.4%). Using the SARS-CoV-2 binding IgG immunoassay (n = 22, specific for pharmacokinetics), the geometric means of Cmax (AU/mL) for the three COVID-HIGIV dose levels (low to high) were 7.69, 17.02, and 33.27 AU/mL; the average values of Tmax were 7.09, 7.93, and 5.36 h, respectively. The half-life of COVID-HIGIV per dose level was 24 d (583 h), 31 d (753 h), and 26 d (619 h) for the 100 mg/kg, 200 mg/kg, and 400 mg/kg groups, respectively. The safety and pharmacokinetics of COVID-HIGIV support its development as a single-dose regimen for postexposure prophylaxis or treatment of COVID-19.

Protection Induced by Oral Vaccination with a Recombinant Yersinia pseudotuberculosis Delivering Yersinia pestis LcrV and F1 Antigens in Mice and Rats against Pneumonic Plague.

A newly attenuated Yersinia pseudotuberculosis strain (designated Yptb1) with triple mutation Δasd ΔyopK ΔyopJ and chromosomal insertion of the Y. pestis caf1R-caf1M-caf1A-caf1 operon was constructed as a live vaccine platform. Yptb1 tailored with an Asd+ plasmid (pYA5199) (designated Yptb1[pYA5199]) simultaneously delivers Y. pestis LcrV and F1. The attenuated Yptb1(pYA5199) localized in the Peyer's patches, lung, spleen, and liver for a few weeks after oral immunization without causing any disease symptoms in immunized rodents. An oral prime-boost Yptb1(pYA5199) immunization stimulated potent antibody responses to LcrV, F1, and Y. pestis whole-cell lysate (YPL) in Swiss Webster mice and Brown Norway rats. The prime-boost Yptb1(pYA5199) immunization induced higher antigen-specific humoral and cellular immune responses in mice than a single immunization did, and it provided complete short-term and long-term protection against a high dose of intranasal Y. pestis challenge in mice. Moreover, the prime-boost immunization afforded substantial protection for Brown Norway rats against an aerosolized Y. pestis challenge. Our study highlights that Yptb1(pYA5199) has high potential as an oral vaccine candidate against pneumonic plague.

Modification of the Pulmonary MyD88 Inflammatory Response Underlies the Role of the Yersinia pestis Pigmentation Locus in Primary Pneumonic Plague.

Pneumonic plague, caused by Yersinia pestis, is a rapidly progressing bronchopneumonia involving focal bacterial growth, neutrophilic congestion, and alveolar necrosis. Within a short time after inhalation of Y. pestis, inflammatory cytokines are expressed via the Toll/interleukin-1 (IL-1) adaptor myeloid differentiation primary response 88 (MyD88), which facilitates the primary lung infection. We previously showed that Y. pestis lacking the 102-kb chromosomal pigmentation locus (pgm) is unable to cause inflammatory damage in the lungs, whereas the wild-type (WT) strain induces the toxic MyD88 pulmonary inflammatory response. In this work, we investigated the involvement of the pgm in skewing the inflammatory response during pneumonic plague. We show that the early MyD88-dependent and -independent cytokine responses to pgm- Y. pestis infection of the lungs are similar yet distinct from those that occur during pgm+ infection. Furthermore, we found that MyD88 was necessary to prevent growth of the iron-starved pgm- Y. pestis despite the presence of iron chelators lactoferrin and transferrin. However, while this induced neutrophil recruitment, there was no hyperinflammatory response, and pulmonary disease was mild without MyD88. In contrast, growth in blood and tissues progressed rapidly in the absence of MyD88, due to an almost total loss of serum interferon gamma (IFN-γ). We further show that the expression of MyD88 by myeloid cells is important to control bacteremia but not the primary lung infection. The combined data indicate distinct roles for myeloid and nonmyeloid MyD88 and suggest that expression of the pgm is necessary to skew the inflammatory response in the lungs to cause pneumonic plague.

Safety and Clinical Outcomes of an Equine-derived Heptavalent Botulinum Antitoxin Treatment for Confirmed or Suspected Botulism in the United States.

BACKGROUND: Botulism is a rare, life-threatening paralytic illness. Botulism Antitoxin Heptavalent (A,B,C,D,E,F,G)-(Equine) (BAT) manufactured by Emergent BioSolutions Canada Inc is an equine-derived heptavalent botulinum antitoxin product indicated for the treatment of symptomatic botulism following documented or suspected exposure to botulinum neurotoxin serotypes A-G in adults and pediatric patients. BAT product was US-licensed in 2013. METHODS: In the United States, from October 2014 through July 2017, safety and clinical outcomes data were collected under a registry for patients treated with BAT product. RESULTS: Registry patients had a median age of 51 years (range, 32 days to 92 years). Among 162 patients, 7 (4.3%) experienced BAT product-related serious adverse events, including 1 (0.6%) report each of pneumonia, pneumonia aspiration, ventricular tachycardia, upper gastrointestinal hemorrhage, anaphylactic reaction, acute kidney injury, and acute myocardial infarction. Thirty-one (19.1%) patients had 41 BAT product-related adverse events. Six (3.7%) deaths were reported in the registry. All deaths were attributed to the underlying illness and were assessed as unlikely related to BAT product. Among 113 (69.8%) patients with a final diagnosis of botulism, those treated early (≤2 days) spent fewer days in the hospital (5 vs 15.5 days), in the intensive care unit (ICU) (4 vs 12 days), and on mechanical ventilation (6 vs 14.5 days) than those treated late (>2 days), respectively. CONCLUSIONS: BAT product was well tolerated in patients. Treatment with BAT product at ≤2 days of symptom onset was associated with shorter hospital and ICU stays, and shorter duration and need for mechanical ventilation, showing clinical benefit associated with early treatment.

Activation of Heme Oxygenase Expression by Cobalt Protoporphyrin Treatment Prevents Pneumonic Plague Caused by Inhalation of Yersinia pestis.

Pneumonic plague, caused by the Gram-negative bacteria Yersinia pestis, is an invasive, rapidly progressing disease with poor survival rates. Following inhalation of Y. pestis, bacterial invasion of the lungs and a tissue-damaging inflammatory response allows vascular spread of the infection. Consequently, primary pneumonic plague is a multiorgan disease involving sepsis and necrosis of immune tissues and the liver, as well as bronchopneumonia and rampant bacterial growth. Given the likely role of the hyperinflammatory response in accelerating the destruction of tissue, in this work we evaluated the therapeutic potential of the inducible cytoprotective enzyme heme oxygenase 1 (HO-1) against primary pneumonic plague. On its own, the HO-1 inducer cobalt protoporphyrin IX (CoPP) provided mice protection from lethal challenge with Y. pestis CO92 with improved pulmonary bacterial clearance and a dampened inflammatory response compared to vehicle-treated mice. Furthermore, CoPP treatment combined with doxycycline strongly enhanced protection in a rat aerosol challenge model. Compared to doxycycline alone, CoPP treatment increased survival, with a 3-log decrease in median bacterial titer recovered from the lungs and the general absence of a systemic hyperinflammatory response. In contrast, treatment with the HO-1 inhibitor SnPP had no detectable impact on doxycycline efficacy. The combined data indicate that countering inflammatory toxicity by therapeutically inducing HO-1 is effective in reducing the rampant growth of Y. pestis and preventing pneumonic plague.

Yersinia pestis Exploits Early Activation of MyD88 for Growth in the Lungs during Pneumonic Plague.

Yersinia pestis causes bubonic, pneumonic, and septicemic plague. Although no longer responsible for pandemic outbreaks, pneumonic plague continues to be a challenge for medical treatment and has been classified as a reemerging disease in some parts of the world. In the early stage of infection, inflammatory responses are believed to be suppressed by Y. pestis virulence factors in order to prevent clearance, while later, the hyperactivation of inflammation contributes to the progression of disease. In this work, we sought to identify the host factors that mediate this process and studied the role of the Toll/interleukin 1 (IL-1) receptor adapter and major inflammatory mediator myeloid differentiation primary response 88 (MyD88) in pneumonic plague. We show that pulmonary challenge of Myd88-/- mice with wild-type (WT) Y. pestis results in significant loss of pro- and anti-inflammatory cytokines and chemokines, especially gamma interferon (IFN-γ) and KC, in the lungs compared to that in WT mice. Bacterial growth in the lungs occurred more rapidly in the WT mice, however, indicating a role for the MyD88 response in facilitating the primary lung infection. Nevertheless, Myd88-/- mice were more sensitive to lethality from secondary septicemic plague. Together these findings indicate a central role for MyD88 during the biphasic inflammatory response to pulmonary Y. pestis infection. In the early phase, low-level MyD88-dependent chemokine expression limits initial growth but facilitates Y. pestis access to a protected replicative niche. The later hyperinflammatory phase is partially MyD88 dependent and ineffective in the lungs but controls systemic infection and reduces the progression of secondary septicemic plague.

Induction of Type I Interferon through a Noncanonical Toll-Like Receptor 7 Pathway during Yersinia pestis Infection.

Yersinia pestis causes bubonic, pneumonic, and septicemic plague, diseases that are rapidly lethal to most mammals, including humans. Plague develops as a consequence of bacterial neutralization of the host's innate immune response, which permits uncontrolled growth and causes the systemic hyperactivation of the inflammatory response. We previously found that host type I interferon (IFN) signaling is induced during Y. pestis infection and contributes to neutrophil depletion and disease. In this work, we show that type I IFN expression is derived from the recognition of intracellular Y. pestis by host Toll-like receptor 7 (TLR7). Type I IFN expression proceeded independent of myeloid differentiation factor 88 (MyD88), which is the only known signaling adaptor for TLR7, suggesting that a noncanonical mechanism occurs in Y. pestis-infected macrophages. In the murine plague model, TLR7 was a significant contributor to the expression of serum IFN-ß, whereas MyD88 was not. Furthermore, like the type I IFN response, TLR7 contributed to the lethality of septicemic plague and was associated with the suppression of neutrophilic inflammation. In contrast, TLR7 was important for defense against disease in the lungs. Together, these data demonstrate that an atypical TLR7 signaling pathway contributes to type I IFN expression during Y. pestis infection and suggest that the TLR7-driven type I IFN response plays an important role in determining the outcome of plague.

Early apoptosis of macrophages modulated by injection of Yersinia pestis YopK promotes progression of primary pneumonic plague.

Yersinia pestis causes pneumonic plague, a disease characterized by inflammation, necrosis and rapid bacterial growth which together cause acute lung congestion and lethality. The bacterial type III secretion system (T3SS) injects 7 effector proteins into host cells and their combined activities are necessary to establish infection. Y. pestis infection of the lungs proceeds as a biphasic inflammatory response believed to be regulated through the control of apoptosis and pyroptosis by a single, well-conserved T3SS effector protein YopJ. Recently, YopJ-mediated pyroptosis, which proceeds via the NLRP3-inflammasome, was shown to be regulated by a second T3SS effector protein YopK in the related strain Y. pseudotuberculosis. In this work, we show that for Y. pestis, YopK appears to regulate YopJ-mediated apoptosis, rather than pyroptosis, of macrophages. Inhibition of caspase-8 blocked YopK-dependent apoptosis, suggesting the involvement of the extrinsic pathway, and appeared cell-type specific. However, in contrast to yopJ, deletion of yopK caused a large decrease in virulence in a mouse pneumonic plague model. YopK-dependent modulation of macrophage apoptosis was observed at 6 and 24 hours post-infection (HPI). When YopK was absent, decreased populations of macrophages and dendritic cells were seen in the lungs at 24 HPI and correlated with resolution rather than progression of inflammation. Together the data suggest that Y. pestis YopK may coordinate the inflammatory response during pneumonic plague through the regulation of apoptosis of immune cells.

Opposing roles for interferon regulatory factor-3 (IRF-3) and type I interferon signaling during plague.

Type I interferons (IFN-I) broadly control innate immunity and are typically transcriptionally induced by Interferon Regulatory Factors (IRFs) following stimulation of pattern recognition receptors within the cytosol of host cells. For bacterial infection, IFN-I signaling can result in widely variant responses, in some cases contributing to the pathogenesis of disease while in others contributing to host defense. In this work, we addressed the role of type I IFN during Yersinia pestis infection in a murine model of septicemic plague. Transcription of IFN-ß was induced in vitro and in vivo and contributed to pathogenesis. Mice lacking the IFN-I receptor, Ifnar, were less sensitive to disease and harbored more neutrophils in the later stage of infection which correlated with protection from lethality. In contrast, IRF-3, a transcription factor commonly involved in inducing IFN-ß following bacterial infection, was not necessary for IFN production but instead contributed to host defense. In vitro, phagocytosis of Y. pestis by macrophages and neutrophils was more effective in the presence of IRF-3 and was not affected by IFN-ß signaling. This activity correlated with limited bacterial growth in vivo in the presence of IRF-3. Together the data demonstrate that IRF-3 is able to activate pathways of innate immunity against bacterial infection that extend beyond regulation of IFN-ß production.

Pathogenicity and virulence of Yersinia.

The genus Yersinia includes human, animal, insect, and plant pathogens as well as many symbionts and harmless bacteria. Within this genus are Yersinia enterocolitica and the Yersinia pseudotuberculosis complex, with four human pathogenic species that are highly related at the genomic level including the causative agent of plague, Yersinia pestis. Extensive laboratory, field work, and clinical research have been conducted to understand the underlying pathogenesis and zoonotic transmission of these pathogens. There are presently more than 500 whole genome sequences from which an evolutionary footprint can be developed that details shared and unique virulence properties. Whereas the virulence of Y. pestis now seems in apparent homoeostasis within its flea transmission cycle, substantial evolutionary changes that affect transmission and disease severity continue to ndergo apparent selective pressure within the other Yersiniae that cause intestinal diseases. In this review, we will summarize the present understanding of the virulence and pathogenesis of Yersinia, highlighting shared mechanisms of virulence and the differences that determine the infection niche and disease severity.

Integrative analysis highlights molecular and immune responses of tick Amblyomma americanum to Escherichia coli challenge.

Ticks are ectoparasites that can transmit various pathogens capable of causing life-threatening illnesses in people and animals, making them a severe public health threat. Understanding how ticks respond to bacterial infection is crucial for deciphering their immune defense mechanisms and identifying potential targets for controlling tick-borne diseases. In this study, an in-depth transcriptome analysis was used to investigate the molecular and immune responses of Amblyomma americanum to infection caused by the microinjection of Escherichia coli. With an abundance of differentially expressed genes discovered at different times, the analysis demonstrated significant changes in gene expression profiles in response to E. coli challenge. Notably, we found alterations in crucial immune markers, including the antimicrobial peptides defensin and microplusin, suggesting they may play an essential role in the innate immune response. Furthermore, KEGG analysis showed that following E. coli exposure, a number of key enzymes, including lysosomal alpha-glucosidase, fibroblast growth factor, legumain, apoptotic protease-activating factor, etc., were altered, impacting the activity of the lysosome, mitogen-activated protein kinase, antigen processing and presentation, bacterial invasion, apoptosis, and the Toll and immune deficiency pathways. In addition to the transcriptome analysis, we constructed protein interaction networks to elucidate the molecular interactions underlying the tick's response to E. coli challenge. Hub genes were identified, and their functional enrichment provided insights into the regulation of cytoskeleton rearrangement, apoptotic processes, and kinase activity that may occur in infected cells. Collectively, the findings shed light on the potential immune responses in A. americanum that control E. coli infection.

Equine Polyclonal Antibodies Prevent Acute Chikungunya Virus Infection in Mice.

Chikungunya virus (CHIKV) is a mosquito-transmitted pathogen that causes chikungunya disease (CHIK); the disease is characterized by fever, muscle ache, rash, and arthralgia. This arthralgia can be debilitating and long-lasting, seriously impacting quality of life for years. Currently, there is no specific therapy available for CHIKV infection. We have developed a despeciated equine polyclonal antibody (CHIKV-EIG) treatment against CHIKV and evaluated its protective efficacy in mouse models of CHIKV infection. In immunocompromised (IFNAR-/-) mice infected with CHIKV, daily treatment for five consecutive days with CHIKV-EIG administered at 100 mg/kg starting on the day of infection prevented mortality, reduced viremia, and improved clinical condition as measured by body weight loss. These beneficial effects were seen even when treatment was delayed to 1 day after infection. In immunocompetent mice, CHIKV-EIG treatment reduced virus induced arthritis (including footpad swelling), arthralgia-associated cytokines, viremia, and tissue virus loads in a dose-dependent fashion. Collectively, these results suggest that CHIKV-EIG is effective at preventing CHIK and could be a viable candidate for further development as a treatment for human disease.

Expression hierarchy in the Yersinia type III secretion system established through YopD recognition of RNA.

The Yersinia type III secretion system (T3SS) is environmentally responsive to enable its rapid induction upon contact with host cells and is necessary for Yersiniae to establish a replicative niche and cause disease. YopD, a translocator protein, represses the expression of T3SS genes until signalled by environmental cues, a mechanism known as the low calcium response. In this work, we investigated recognition of target genes by Yersinia pestis YopD. Expression of all genes of the T3SS was induced in a yopD mutant, though not to the same degree, with effector Yops most affected. Two, short AU-rich sequence elements up- and downstream of start codons of target genes were necessary but not sufficient for YopD mediated repression. Purified YopD-LcrH bound specifically to target RNAs in vitro with different relative affinities, with effector Yops having greater affinity. Together, the data suggest YopD binds to T3SS transcripts where it may prevent ribosome binding causing accelerated mRNA degradation. This regulatory mechanism may ensure an expression hierarchy during the low calcium response as low affinity YopD targets such as chaperones would be translated prior to high affinity targets such as effector Yops allowing the bacteria another layer of control over Yop translocation during infection.

Chemokine receptor CXCR2 mediates bacterial clearance rather than neutrophil recruitment in a murine model of pneumonic plague.

Pulmonary infection by Yersinia pestis causes pneumonic plague, a necrotic bronchopneumonia that is rapidly lethal and highly contagious. Acute pneumonic plague accompanies the up-regulation of pro-inflammatory cytokines and chemokines, suggesting that the host innate immune response may contribute to the development of disease. To address this possibility, we sought to understand the consequences of neutrophil recruitment during pneumonic plague, and we studied the susceptibility of C3H-HeN mice lacking the CXC chemokine KC or its receptor CXC receptor 2 (CXCR2) to pulmonary Y. pestis infection. We found that without Kc or Cxcr2, disease progression was accelerated both in bacterial growth and development of primary bronchopneumonia. When examined in an antibody clearance model, Cxcr2(-/-) mice were not protected by neutralizing Y. pestis antibodies, yet bacterial growth in the lungs was delayed in a manner associated with a neutrophil-mediated inflammatory response. After this initial delay, however, robust neutrophil recruitment in Cxcr2(-/-) mice correlated with bacterial growth and the development of fulminant pneumonic and septicemic plague. In contrast, attenuated Y. pestis lacking the conserved pigmentation locus could be cleared from the lungs in the absence of Cxcr2 indicating virulence factors within this locus may inhibit CXCR2-independent pathways of bacterial killing. Together, the data suggest CXCR2 uniquely induces host defense mechanisms that are effective against virulent Y. pestis, raising new insight into the activation of neutrophils during infection.

Human immune globulin treatment controls Zika viremia in pregnant rhesus macaques.

There are currently no approved drugs to treat Zika virus (ZIKV) infection during pregnancy. Hyperimmune globulin products such as VARIZIG and WinRho are FDA-approved to treat conditions during pregnancy such as Varicella Zoster virus infection and Rh-incompatibility. We administered ZIKV-specific human immune globulin as a treatment in pregnant rhesus macaques one day after subcutaneous ZIKV infection. All animals controlled ZIKV viremia following the treatment and generated robust levels of anti-Zika virus antibodies in their blood. No adverse fetal or infant outcomes were identified in the treated animals, yet the placebo control treated animals also did not have signs related to congenital Zika syndrome (CZS). Human immune globulin may be a viable prophylaxis and treatment option for ZIKV infection during pregnancy, however, more studies are required to fully assess the impact of this treatment to prevent CZS.

Interrelationship of soil moisture and temperature to sylvatic plague cycle among prairie dogs in the Western United States.

Plague, caused by Yersinia pestis, is a flea-borne disease that is endemic in areas throughout the world due to its successful maintenance in a sylvatic cycle, mainly in areas with temperate climates. Burrowing rodents are thought to play a key role in the enzootic maintenance as well as epizootic outbreaks of plague. In the United States, prairie dogs (Cynomys), rodents (Muridae), and ground squirrels (Spermophilus) are susceptible to infection and are parasitized by fleas that transmit plague. In particular, prairie dogs can experience outbreaks that rapidly spread, which can lead to extirpation of colonies. A number of ecological parameters, including climate, are associated with these epizootics. In this study, we asked whether soil parameters, primarily moisture and temperature, are associated with outbreaks of plague in black-tailed prairie dogs and Gunnison's prairie dogs in the Western United States, and at what depth these associations were apparent. We collected publicly available county-level information on the occurrence of population declines or colony extirpation, while historical soil data was collected from SCAN and USCRN stations in counties and states where prairie dogs have been located. The analysis suggests that soil moisture at lower depths correlates with colony die-offs, in addition to temperature near the surface, with key differences within the landscape ecology that impact the occurrence of plague. Overall, the model suggests that the burrow environment may play a significant role in the epizootic spread of disease amongst black-tailed and Gunnison's prairie dogs.

Results of a Double-Blind, Randomized, Placebo-Controlled Phase 1 Study to Evaluate the Safety and Pharmacokinetics of Anti-Zika Virus Immunoglobulin.

Zika virus (ZIKV) is transmitted primarily through infected Aedes aegypti or Aedes albopictus mosquitoes. ZIKV infection during pregnancy was linked to adverse fetal/infant outcomes, including microcephaly, brain anomalies, ocular disorders, intrauterine growth restriction, and other congenital malformations. Human anti-Zika virus immunoglobulin (ZIKV-Ig) is being developed for prophylaxis of ZIKV in at-risk populations, including women of childbearing potential and pregnant women. A phase 1 single-center, double-blind, randomized, placebo-controlled study was conducted to assess the safety and pharmacokinetics (PK) of a single 50.0-mL ZIKV-Ig intravenous dose in healthy adult male or non-pregnant female subjects 18 to 55 years of age. Subjects received either ZIKV-Ig (n = 19) or saline placebo (n = 11). Safety was evaluated based on adverse events (AEs), laboratory test results, physical examinations, and vital signs. Overall, there were 11 subjects (36.7%) with treatment-related AEs including eight subjects (42.1%) in the ZIKV-Ig group and three subjects (27.3%) in the placebo group. Of the AEs considered treatment related, three subjects (15.8%) experienced headache (mild). There were no serious AEs, no deaths, and no discontinuations resulting from AEs. Overall, the safety profile of ZIKV-Ig in this study population of healthy adult subjects appeared to be safe and well tolerated. The results of the pharmacokinetic analysis determined that ZIKV-Ig had a maximum observed concentration of 182.3 U/mL (coefficient of variation, 21.3%), the time at which Cmax occurred of 2.3 hours ± 1.0 (SD), an area under the concentration-time curve0-∞ of 77,224 h × U/mL (coefficient of variation, 17.9%), and a half-life of 28.1 days, which is similar to other human-derived commercial Ig intravenous products.

Use of Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)-(Equine) (BAT®) in Clinical Study Subjects and Patients: A 15-Year Systematic Safety Review.

Botulism is a rare, sometimes fatal paralytic illness caused by botulinum neurotoxins. BAT® (Botulism Antitoxin Heptavalent (A, B, C, D, E, F, G)-(Equine)) is an equine-derived heptavalent botulinum antitoxin indicated for the treatment of symptomatic botulism in adult and pediatric patients. This review assesses the cumulative safety profile for BAT product from 2006 to 2020, using data received from clinical studies, an expanded-access program, a post-licensure registry, spontaneous and literature reports. The adverse event (AE) incidence rate for BAT product was calculated conservatively using only BAT product exposures for individuals with a record (512) and was alternatively estimated using all BAT product exposure data, including post-licensure deployment information (1128). The most frequently reported BAT product-related AEs occurring in greater than 1% of the 512-1128 BAT product-exposed individuals were hypersensitivity, pyrexia, tachycardia, bradycardia, anaphylaxis, and blood pressure increase reported in 2.3-5.1%, 1.8-3.9%, 1.0-2.2%, 0.89-2.0%, 0.62-1.4%, and 0.62-1.4%, respectively. For patients properly managed in an intensive care setting, the advantages of BAT product appear to outweigh potential risks in patients due to morbidity and mortality of botulism. AEs of special interest, including bradycardia, hemodynamic instability, hypersensitivity, serum sickness, and febrile reactions in the registry, were specifically solicited.

Absence of inflammation and pneumonia during infection with nonpigmented Yersinia pestis reveals a new role for the pgm locus in pathogenesis.

Yersinia pestis causes primary pneumonic plague in many mammalian species, including humans, mice, and rats. Virulent Y. pestis strains undergo frequent spontaneous deletion of a 102-kb chromosomal DNA fragment, known as the pigmentation (pgm) locus, when grown in laboratory media, yet this locus is present in every virulent isolate. The pgm locus encodes, within a high-pathogenicity island, siderophore biosynthesis genes that are required for growth in the mammalian host when inoculated by peripheral routes. Recently, higher challenge doses of nonpigmented Y. pestis were reported to cause fatal pneumonic plague in mice, suggesting a useful model for studies of virulence and immunity. In this work, we show that intranasal infection of BALB/c mice with nonpigmented Yersinia pestis does not result in pneumonic plague. Despite persistent bacterial colonization of the lungs and the eventual death of infected mice, pulmonary inflammation was generally absent, and there was no disease pathology characteristic of pneumonic plague. Iron given to mice at the time of challenge, previously shown to enhance the virulence of pgm-deficient strains, resulted in an accelerated disease course, with less time to bacteremia and lethality, but lung inflammation and pneumonia were still absent. We examined other rodent models and found differences in lung inflammatory responses, some of which led to clearance and survival even when high challenge doses were used. Together, the results suggest that the Y. pestis pgm locus encodes previously unappreciated virulence factors required for the induction of pneumonic plague that are independent of iron scavenging from the mammalian host.

Pneumonic plague pathogenesis and immunity in Brown Norway rats.

The Brown Norway rat was recently described as a bubonic plague model that closely mimics human disease. We therefore evaluated the Brown Norway rat as an alternative small animal model for pneumonic plague and characterized both the efficacy and potency of vaccine candidates. When infected by intranasal instillation, these rats rapidly developed fatal pneumonic plague within 2 to 4 days of infection. Plague disease was characterized by severe alveolar edema and vascular hemorrhage in the lung in addition to fulminant necrotizing pneumonia caused by massive bacterial replication and inflammation. Twenty-four hours before death, animals developed systemic disease with an apparent delayed inflammatory response. We evaluated the ability of the protective antigen, LcrV, and a mutant derivative, V10, to protect these rats from pneumonic plague. Both were highly effective vaccines because complete protection was observed at challenge doses of 7500 LD(50). Antibody analyses suggested stronger potency of V10 immune sera compared with LcrV in the passive transfer of immunity to bubonic plague, with multiple neutralizing epitopes in LcrV. Taken together, these data demonstrate the effectiveness of inhibiting type III secretion in the prevention of pneumonic plague in rats and reveal critical contributions from both the cellular and humoral immune systems. Thus, the Brown Norway rat is an appealing alternative small animal model for the study of pneumonic plague pathogenesis and immunity.