Vaccination evokes gender-dependent protection against tularemia infection in C57BL/6Tac mice

Francisella tularensis (Ft) is a Category A biothreat agent for which there currently is no FDA-approved vaccine. Thus, there is a substantial effort underway to develop an effective tularemia vaccine. While it is well established that gender can significantly impact susceptibility to primary infection, the impact of gender on vaccine efficacy is not well established. Thus, development of a successful vaccine against tularemia will require an understanding of the impact gender has on vaccine-induced protection against this organism. In this study, a role for gender in vaccine-induced protection following Ft challenge is identified for the first time. In the present study, mucosal vaccination with inactivated Ft (iFt) LVS elicited gender-based protection in C57BL/6Tac mice against respiratory challenge with Ft LVS. Specifically, vaccinated male mice were more susceptible to subsequent Ft LVS challenge. This increased susceptibility in male mice correlated with increased bacterial burden, increased tissue inflammation, and increased proinflammatory cytokine production late in post-challenge infection. In contrast, improved survival of iFt-vaccinated female mice correlated with reduced bacterial burden and enhanced levels of Ft-specific Abs in serum and broncho-alveolar lavage (BAL) fluid post-challenge. Furthermore, vaccination with a live attenuated vaccine consisting of an Ft LVS superoxide dismutase (SodB) mutant, which has proven efficacious against the highly virulent Ft SchuS4 strain, demonstrated similar gender bias in protection post-Ft SchuS4 challenge. Of particular significance is the fact that these are the first studies to demonstrate that gender differences impact disease outcome in the case of lethal respiratory tularemia following mucosal vaccination. In addition, these studies further emphasize the fact that gender differences must be a serious consideration in any future tularemia vaccine development studies.     

Multiple Francisella tularensis Subspecies and Clades, Tularemia Outbreak, Utah

In July 2007, a deer fly–associated outbreak of tularemia occurred in Utah. Human infections were caused by 2 clades (A1 and A2) of Francisella tularensis subsp. tularensis. Lagomorph carcasses from the area yielded evidence of infection with A1 and A2, as well as F. tularensis subsp. holarctica. These findings indicate that multiple subspecies and clades can cause disease in a localized outbreak of tularemia.     

Immunoproteomic analysis of the human antibody response to natural tularemia infection with Type A or Type B strains or LVS vaccination

Francisella tularensis is pathogenic for many mammalian species including humans, causing a spectrum of diseases called tularemia. The highly virulent Type A strains have associated mortality rates of up to 60% if inhaled. An attenuated live vaccine strain (LVS) is the only vaccine to show efficacy in humans, but suffers several barriers to licensure, including the absence of a correlate of protection. An immunoproteomics approach was used to survey the repertoire of antibodies in sera from individuals who had contracted tularemia during two outbreaks and individuals from two geographical areas who had been vaccinated with NDBR Lot 11 or Lot 17 LVS. These data showed a large overlap in the antibodies generated in response to tularemia infection or LVS vaccination. A total of seven proteins were observed to be reactive with 60% or more sera from vaccinees and convalescents. A further four proteins were recognised by 30–60% of the sera screened. These proteins have the potential to serve as markers of vaccination or candidates for subunit vaccines.     

Safety,reactogenicity and immunogenicity of Francisella tularensis live vaccine strain in humans

We evaluated the safety, reactogenicity and immunogenicity of escalating doses of a new Francisella tularensis Live Vaccine Strain (LVS) lot by scarification (SCAR) or subcutaneously (SQ) in humans. Subjects (N = 10/group) received one dose of LVS via SCAR at 10⁵,10⁷ or 10⁹ cfu/ml or SQ at 10², 10³,10⁴ or 10⁵ cfu/ml; 14 subjects received placebo. All doses/routes were well tolerated. When compared to placebo, vaccination with 10⁷ SCAR and 10⁹ SCAR resulted in significantly higher serologic response frequencies, as measured by ELISA for IgG, IgM, IgA and microagglutination; whereas vaccination with 10⁵ SCAR, 10⁷ SCAR 10⁹ SCAR and 10⁵ SQ elicited a significantly higher interferon-γ response frequency.     

Identification of Francisella tularensis outer membrane protein A (FopA) as a protective antigen for tularemia

Francisella tularensis is a highly pathogenic gram negative bacterium that infects multiple sites in a host, including the skin and the respiratory tract, which can lead to the onset of a deadly disease with a 50% mortality rate. The live vaccine strain (LVS) of F. tularensis, while attenuated in humans but still virulent in mice, is not an option for vaccine use in the United States due to safety concerns, and currently no FDA approved vaccine exists. The purpose of the present work was to assess the ability of recombinant Francisella outer membrane protein A (FopA) to induce a protective response in mice. The gene encoding FopA from F. tularensis LVS was cloned and expressed in Escherichia coli. The resulting recombinant protein was affinity-purified from the E. coli outer membrane, incorporated into liposomes and administered to mice via multiple routes. FopA-immunized mice produced FopA-specific antibodies and were protected against both lethal intradermal and intranasal challenges with F. tularensis LVS. The vaccinated mice had reduced bacterial numbers in their lungs, livers and spleens during infection, and complete bacterial clearance was observed by day 28 post infection. Passive transfer of FopA-immune serum protected naïve mice against lethal F. tularensis LVS challenge, showing that humoral immunity played an important role in vaccine efficacy. FopA-immunization was unable to protect against challenge with the fully virulent SchuS4 strain of F. tularensis; however, the findings demonstrate proof of principle that an immune response generated against a component of a subunit vaccine is protective against lethal respiratory and intradermal tularemia.     

Tularemia in children

Objective  Tularemia, an infection caused by the coccobacilus Francisella tularensis, can be a difficult disease process to diagnose and treat. The aim of this study was to evaluate an epidemic of tularemia in Bursa. Methods  In this study, we included only pediatric cases. All the cases were diagnosed on clinical and serological grounds. Results  During an epidemic of tularemia in a village of Bursa on December 2004, 70 people (60 adults, 10 children) fell ill. In children with tularemia, the oropharyngeal form predominated which was diagnosed 70% of cases. Most of the patients (80%) who had older than 10 years old, were treated with doxycycline. All patients recovered without complications. Conclusion  The epidemic was thought to be waterborne. The vehicle of the infections was inadequately treated water which was used by the patient in the village.     

Tularemia in Bursa, Turkey: 205 cases in ten years

Tularemia is a zoonotic disease caused by the coccobacillus F. tularensis. Small epidemics and sporadic cases were seen around Bursa since November 1988. In this study, a total of 205 cases of tularemia were observed. All the cases were diagnosed on clinical, bacteriological and serological grounds. The epidemics were thought to be waterborne. The majority of the patients were young and female. In most of the cases the disease presented itself in oropharyngeal form (83%). Analysing sera from the patients with microagglutination method demonstrated that titers were 1:160 in approximately 85% of the cases, including the ones in subclinical form. Five of ten patients from who the bacteria was isolated were seronegative. Streptomycin was given to the most of the patients by combining with tetracycline, doxycycline or chloramphenicol. The early administration of these antibiotics (before the third week of disease) was found to be much more effective to resolve the infection. As a result, the main mode of transmission of F. tularensis is waterborne in our region. In our region, tularemia should be considered in differential diagnosis for the cases with fever, tonsillopharyngitis and cervical lymphadenopathy to make an early diagnosis and to design relevant treatment.     

Anthrax, tularemia, plague, ebola or smallpox as agents of bioterrorism: recognition in the emergency room

Bioterrorism has become a potential diagnostic consideration in infectious diseases. This article reviews the clinical presentation and differential diagnosis of potential bioterrorist agents when first presenting to the hospital in the emergency room setting. The characteristic clinical features of inhalation anthrax, tularemic pneumonia, plague pneumonia, including laboratory and radiographic finding, are discussed. Ebola vieus and smallpox are also discussed as potential bioterrorist-transmitted infections from the clinical and epidemiologic standpoint. In addition to the clinical features of the infectious diseases mentioned, the artical discusses the infectious disease control and epidemiologic implications of these agents when employed as bioterrorist agents. The review concludes with suggestions for postexposure prophylaxis and therapy.     

Detoxified Endotoxin Vaccine (J5dLPS/OMP) Protects Mice Against Lethal Respiratory Challenge with Francisella tularensis SchuS4

Francisella tularensis is a category A select agent. J5dLPS/OMP is a novel vaccine construct consisting of detoxified, O-polysaccharide side chain-deficient, lipopolysaccharide non-covalently complexed with the outer membrane protein of N. meningitidis group B. Immunization elicits high-titer polyclonal antibodies specific for the highly-conserved epitopes expressed within the glycolipid core that constitutes gram-negative bacteria (e.g., F. tularensis). Mice immunized intranasally with J5dLPS/OMP exhibited protective immunity to intratracheal challenge with the live vaccine strain, as well as the highly-virulent SchuS4 strain, of F. tularensis. The efficacy of J5dLPS/OMP vaccine suggests its potential utility in immunizing the general population against several different gram-negative select agents concurrently.