Analysis of Aleutian disease virus infection in vitro and in vivo: demonstration of Aleutian disease virus DNA in tissues of infected mink.

Aleutian disease virus (ADV) infection was analyzed in vivo and in vitro to compare virus replication in cell culture and in mink. Initial experiments compared cultures of Crandell feline kidney (CRFK) cells infected with the avirulent ADV-G strain or the highly virulent Utah I ADV. The number of ADV-infected cells was estimated by calculating the percentage of cells displaying ADV antigen by immunofluorescence (IFA), and several parameters of infection were determined. Infected cells contained large quantities of viral DNA (more than 10(5) genomes per infected cell) as estimated by dot-blot DNA-DNA hybridization, and much of the viral DNA, when analyzed by Southern blot hybridization, was found to be of a 4.8-kilobase-pair duplex monomeric replicative form (DM DNA). Furthermore, the cultures contained 7 to 67 fluorescence-forming units (FFU) per infected cell, and the ADV genome per FFU ratio ranged between 2 X 10(3) and 164 X 10(3). Finally, the pattern of viral antigen detected by IFA was characteristically nuclear, although cytoplasmic fluorescence was often found in the same cells. Because no difference was noted between the two virus strains when cultures containing similar numbers of infected cells were compared, it seemed that both viruses behaved similarly in infected cell culture. These data were used as a basis for the analysis of infection of mink by virulent Utah I ADV. Ten days after infection, the highest levels of viral DNA were detected in spleen (373 genomes per cell), mesenteric lymph node (MLN; 750 genomes per cell), and liver (373 genomes per cell). In marked contrast to infected CRFK cells, the predominant species of ADV DNA in all tissues was single-stranded virion DNA; however, 4.8-kilobase-pair DM DNA was found in MLN and spleen. This observation suggested that MLN and spleen were sites of virus replication, but that the DNA found in liver reflected sequestration of virus produced elsewhere. A final set of experiments examined MLN taken from nine mink 10 days after Utah I ADV infection. All of the nodes contained ADV DNA (46 to 750 genomes per cell), and although single-stranded virion DNA was always the most abundant species, DM DNA was observed. All of the lymph nodes contained virus infectious for CRFK cells, but when the genome per FFU ratio was calculated, virus from the lymph nodes required almost 1,000 times more genomes to produce an FFU than did virus prepared from infected cell cultures.(ABSTRACT TRUNCATED AT 400 WORDS)     

Development and application of hepatitis C reporter viruses with genotype 1 to 7 core-nonstructural protein 2 (NS2) expressing fluorescent proteins or luciferase in modified JFH1 NS5A

To facilitate genotype-specific high-throughput studies of hepatitis C virus (HCV), we have developed reporter viruses using JFH1-based recombinants expressing core-nonstructural protein 2 (NS2) of genotype 1 to 7 prototype isolates. We introduced enhanced green fluorescent protein (EGFP) into NS5A domain III of the genotype 2a virus J6/JFH1 [2a(J6)]. During Huh7.5 cell culture adaptation, 2a(J6)-EGFP acquired a 40-amino-acid (aa) (Δ40) or 25-aa (Δ25) deletion in NS5A domain II, rescuing the impairment of viral assembly caused by the EGFP insertion. Δ40 conferred efficient growth characteristics to 2a(J6) tagged with EGFP, DsRed-Express2, mCherry, or Renilla luciferase (RLuc), yielding peak supernatant infectivity titers of 4 to 5 log(10) focus-forming units (FFU)/ml. 2a(J6) with Δ40 or Δ25 was fully viable in Huh7.5 cells. In human liver chimeric mice, 2a(J6)-EGFPΔ40 acquired various deletions in EGFP, while 2a(J6)Δ40 did not show an impaired viability. We further developed panels of JFH1-based genotype 1 to 7 core-NS2 recombinants expressing EGFP- or RLuc-NS5AΔ40 fusion proteins. In cell culture, the different EGFP recombinants showed growth characteristics comparable to those of the nontagged recombinants, with peak infectivity titers of 4 to 5 log(10) FFU/ml. RLuc recombinants showed slightly less efficient growth characteristics, with peak infectivity titers up to 10-fold lower. Overall, the EGFP and RLuc recombinants were genetically stable after one viral passage. The usefulness of these reporter viruses for high-throughput fluorescence- and luminescence-based studies of HCV-receptor interactions and serum-neutralizing antibodies was demonstrated. Finally, using RLuc viruses, we showed that the genotype-specific core-NS2 sequence did not influence the response to alfa-2b interferon (IFN-alfa-2b) and that genotype 1 to 7 viruses all responded to treatment with p7 ion channel inhibitors.     

Blood biochemical polymorphisms as markers for genetic characteristics of wild Spanish and domestic rabbits

Seventeen blood proteins were studied in a sample of 412 Spanish wild rabbits and in 598 domestic rabbits belonging to various breeds. The wild rabbit populations showed a high level of genetic polymorphism. Six loci were monomorphic, while the remaining ten loci were segregating for at least two alleles. Two of the loci that were polymorphic in the wild rabbits were monomorphic in the domestic ones. Wright's inbreeding coefficient in the total Spanish wild rabbit population was F=5.66, indicating subdivision of the total population. Inbreeding coefficients, estimated by Kidd et al.'s method (Anim. Blood Grps, Biochem. Genet. 11: 21–38), differed significantly from zero, being 15.62%, in wild rabbits and 6–12% in domestic breeds, indicating consanguinity.Genetic distances between wild rabbit populations showed that factors other than geographic distance (e.g., bottlenecks, barriers such as rivers, mountains, etc.) may explain the result that a northern population forms a cluster with two central populations whereas the northeastern populations form a different cluster with another central population. Populations of the first cluster are more closely related to the captive populations than others.There are three population clusters of domestic rabbits, namely (1) New Zealand White and a hybrid combination; (2) Spanish Common, Butterfly, Burgundy, and Californian; and (3) Spanish Giant.     

Changes in lipid pattern of HeLa cells exposed to immunoglobulin G and complement

1. Immunoglobulin G was isolated from sera of non-immunized rabbits or rabbits immunized with whole HeLa cell homogenate. The anti-HeLa immunoglobulin G and its Fab fragment precipitated the particulate 400000g-min. fraction of HeLa cell homogenate. 2. Immunoglobulin G from immunized or non-immunized rabbits and fresh or inactivated complement were added to HeLa cell cultures. Changes in the cell count and cellular contents of DNA, RNA, protein, total and individual phospholipids, cholesterol (and esters) and ganglioside were followed. 3. Addition of immunoglobulin G from non-immunized rabbits and guinea-pig serum (complement) caused a transient increase in DNA followed by a permanent increase in RNA, protein, dry weight and number of cells per culture. 4. Addition of anti-HeLa immunoglobulin G and active complement caused an increase in the cellular content of cholesterol, total phospholipids, lysophosphatidylcholine and lysophosphatidylethanolamine greater than the increase of the controls and a decrease in the molar percentages of phosphatidylcholine and phosphatidylethanolamine as compared with the controls. 5. The cholesterol/phospholipid ratio remained constant. 6. The appearance of lysophosphoglycerides was transient, reaching a maximum 3hr. after addition of anti-HeLa immunoglobulin G. 7. The content of lysophosphoglycerides in HeLa cultures exposed to immunoglobulin G from non-immunized rabbits ranged from 50% to 30% of the values obtained from cultures exposed to the anti-HeLa immunoglobulin G and complement. 8. The changes in the lipid pattern of the HeLa cells were associated with the appearance of juxta-nuclear vacuoles in cells, but were apparently not specifically related to the presence of active complement.     

A novel process for the production of a veterinary rabies vaccine in BHK-21 cells grown on microcarriers in a 20-l bioreactor

We studied BHK-21 cells growth in a 2-l bioreactor and investigated the effects of microcarrier concentration, type of growth medium, culture mode and serum concentration. The highest cell density reached was equal to 4x10(6) cells/ml and was achieved in minimum essential medium supplemented with Hanks' salts, non-essential amino acids and 5% fetal calf serum, using a perfusion culture mode and a microcarrier concentration of 4 g Cytodex 3/l. We studied rabies virus production (PV/BHK-21 strain) by BHK-21 cells grown at the optimal conditions determined previously. We analyzed the effects of multiplicity of infection (MOI) and type of medium used for virus multiplication in spinner-flasks and showed that the highest virus titer reached (when the cells were infected at a MOI of 0.3) in M199 medium supplemented with 0.2% of bovine serum albumin was equal to 8.2x10(7) Fluorescent Focus Units (FFU)/ml. When we grew the cells in a 2-l perfused bioreactor, we obtained a maximal virus titer of 3x10(8) FFU/ml. In addition, we scaled-up to a 20-l bioreactor and obtained similar results for cell density and virus titer. The experimental vaccine we developed meets WHO requirements for vaccine potency. Each run yielded about 40,000 doses of potent vaccine.     

Inter-laboratory comparison of the CD-1 neonatal mouse logistic dose-response model for Cryptosporidium parvum oocysts

cryptosporidium parvum oocyst viability can be determined by vital dyes, in vitro excystation, and cell culture; however, neonatal mouse infectivity assays are the reference method. Unfortunately, there have been few efforts to standardize methods for infectivity assays thus casting a veil of uncertainty over the significance and comparability of results. In order to address this issue, two laboratories proficient in measuring oocyst infectivity conducted independent dose titration studies with neonatal CD-1 mice using standardized protocols and a well-characterized isolate of Cryptosporidium parvum. The resulting independent logistic dose-response models derived by regression analysis were compared with each other and with a published model. The comparisons showed these dose-response functions to be reproducible under standardized conditions. It is important to standardize mouse strain, age of mice at inoculation and necropsy, oocyst isolate, and age of oocysts. However, other factors, including methods used to detect infectivity and to count oocyst doses, appear less critical. Adopting a standardized assay for oocyst infectivity will provide both a basis for comparing data from various oocyst disinfection studies and a suitable platform for evaluating new or existing in vitro viability surrogates such as excystation, vital dyes or cell culture.     

Candidate genes underlying heritable differences in reproductive seasonality between wild and domestic rabbits

Reproductive seasonality is a trait that often differs between domestic animals and their wild ancestors, with domestic animals showing prolonged or even continuous breeding seasons. However, the genetic basis underlying this trait is still poorly understood for most species, and because environmental factors and resource availability are known to play an important role in determining breeding seasons, it is also not clear in most cases to what extent this phenotypic shift is determined by the more lenient captive conditions or by genetic factors. Here, using animals resulting from an initial cross between wild and domestic rabbits followed by two consecutive backcrosses (BC1 and BC2) to wild rabbits, we evaluated the yearly distribution of births for the different generations. Similar to domestic rabbits, F1 animals could be bred all year round but BC1 and BC2 animals showed a progressive and significant reduction in the span of the breeding season, providing experimental evidence that reduced seasonal breeding in domestic rabbits has a clear genetic component and is not a simple by‐product of rearing conditions. We then took advantage of a recently published genome‐wide scan of selection in the domesticated lineage and searched for candidate genes potentially associated with this phenotypic shift. Candidate genes located within regions targeted by selection include well‐known examples of genes controlling clock functions (CRY1 and NR3C1) and reproduction (PRLR).     

Alpha-chloralose as a capture and restraint agent of birds: therapeutic index determination in the chicken

The median effective dose for capture (ED50) and the median lethal dose (LD50) of alpha-chloralose given orally to domestic chickens (Gallus domesticus) were determined by probit analysis to be 45 mg/kg and 300 mg/kg, respectively. The therapeutic index (TI = LD50/ED50) was 6.7. This indicates that alpha-chloralose is only a marginally safe capture agent in domestic species and particularly in field applications involving other wild avian species in which the amount of the drug ingested by an individual bird is not controlled.     

Herpesvirus sylvilagus in cottontail rabbits: antibody prevalence and flea burden relationships

A serologic survey of a wild cottontail rabbit (Sylvilagus floridanus) population in southern Wisconsin was conducted from November-March, 1971-72 and November-April, 1972-73, to determine prevalence of antibody against Herpesvirus sylvilagus. Flea burdens on each live-trapped cottontail were quantified by species. All but six of the 5029 fleas collected were Cediopsylla simplex. No correlation was found between flea infestation and viral antibody. Of 101 cottontail rabbits trapped, only six had specific antibody as determined by plaque neutralization in rabbit kidney cell culture. Three of the six developed antibody between January and March of the trapping season. Blood samples from 46 captured rabbits were negative for virus.     

Replication of a Nuclear Polyhedrosis Virus in a Continuous Cell Culture of Spodoptera frugiperda: Purification, Assay of Infectivity, and Growth Characteristics of the Virus

Nonoccluded virus, polyhedra, and occluded virus were purified from a continuous cell culture of Spodopera frugiperda infected with nuclear polyhedrosis virus. The optimal temperature for the replication and lateral transmission of infectivity for the nuclear polyhedrosis viruses (NPV) in cell culture was 27 C. End-point dilution and plaque assay procedures for the measurement of infectivity are described and compared. Dose-response data demonstrated that a single particle could initiate an infection, and the validity of the relationship of 0.7 PFU per mean tissue culture infective dose (TCID(5 0)) further substantiated the accuracy of these infectivity assays. Particle-infectious unit calculations gave a ratio of 62 to 310 nonoccluded virus particles TCID(5 0). Growth cycle and lateral transmission experiments indicated that infectious material was released from cells 12 h postinfection (p.i.) and approached a maximal titer 4 days p.i. The number of polyhedra, nonoccluded virions, and TCID(5 0) produced per cell was also presented. Typical yields of NPV produced per liter flask suggested that insect cell culture systems represent a feasible means by which the replication of these viruses could be investigated.     

含外源类蜗牛毒素基因的AcMNPV的虫体感染性研究

类蜗牛毒素基因(conotoxinlike,ctl)是在一些杆状病毒基因组中存在的与蜗牛毒素类似的一类基因,其功能尚不清楚。本文利用苜蓿银纹夜蛾核多角病毒(AcMNPV)bacmid表达系统构建了含油桐尺蠖核多角体病毒(BusuNPV)ctl基因的重组病毒AcBac-ph-ctl。在细胞水平上对ctl基因的RT-PCR分析表明,该基因转录出mRNA。在甜菜夜蛾体内进行了生物活性测定,结果表明AcBac-ph-ctl与对照野生型AcMNPV的LC50,ST50无显著性差异,表明在此系统中,外源的CTL无杀虫增效性能。     

Blind trials evaluating in vitro infectivity of Cryptosporidium oocysts using cell culture immunofluorescence

An optimized cell culture immunofluorescence (IFA) procedure, using the HCT-8 cell line, was evaluated in blind trials to determine the sensitivity and reproducibility of measuring the infectivity of flow-cytometry-prepared inocula of Cryptosporidium parvum oocysts. In separate trials, suspensions consisting of between 0% and 100% viable oocysts were prepared at the US Environmental Protection Agency, shipped to the American Water Laboratory, and analyzed blindly by cell culture IFA. Data indicated the control (100% live) oocyst suspensions yielded statistically similar results to cell culture dose-response curve data developed previously at the American Water Laboratory. For test samples containing oocyst suspensions of unknown infectivity, cell culture IFA analyses indicated a high degree of correlation (r2 = 0.89; n = 26) with the values expected by the US Environmental Protection Agency. Cell culture infectivity correlates well with neonatal mouse infectivity assays, and these blind validation trials provide credibility for the cell culture IFA procedure as a cost-effective and expedient alternative to mouse infectivity assays for determining in vitro infectivity of C. parvum oocysts.     

Optimization of virus yield as a strategy to improve rabies vaccine production by Vero cells in a bioreactor

To improve rabies vaccine production by Vero cells, we have developed a strategy based on high cell density culture and optimization of virus yield. We have first optimized cell growth in spinner flask using a Taguchi's L8 experimental design. We analyzed the effects of the following factors: initial glucose and glutamine concentrations, Cytodex 1 concentration and the regulation of glucose level at 1 g l(-1). We have also investigated the effect of the following factor interactions: Cytodex 1 concentration/glutamine concentration, Cytodex 1 concentration/glucose concentration and glucose concentration/glutamine concentration. Statistical analysis of the collected data pointed to the initial glucose concentration, the regulation of glucose level at 1 g l(-1) and the interactions between Cytodex 1 concentration/initial glucose concentration and Cytodex 1 concentration/initial glutamine concentration as the parameters that affected cell growth. Using the optimal conditions determined earlier, we have studied Vero cell growth in a 7-l bioreactor and in batch culture, and obtained a cell density level equal to 3.6 +/- 0.2 x 10(6) cells ml-1. Cell infection with rabies virus (LP 2061/Vero strain) at a multiplicity of infection (MOI) of 0.3 using M199 medium supplemented with 0.2% bovine serum albumin (BSA), yielded a maximal virus titer equal to 8 +/- 1.6 x 10(7) Fluorescent Focus Units (FFU) ml-1. We have also studied Vero cell growth in a 7-l bioreactor using recirculation as a perfusion culture mode during cell proliferation step and perfusion for virus multiplication phase. In comparison to batch culture, we reached a higher cell density level that was equal to 10.1 +/- 0.5 x 10(6) cells ml-1. Cell infection under the conditions previously indicated, yielded 14l of virus harvest that had a virus titer equal to 2.6 +/- 0.5 x 10(7) FFU ml-1. The activity of the inactivated virus harvest showed a protective activity that meets WHO requirements.     

Biodiversity and fermentative activity of caecal microbial communities in wild and farm rabbits from Spain

In order to study the microbial caecal ecosystem of wild and domestic rabbits through the fermentation characteristics and concentration and diversity of bacterial and archaeal communities, caecal samples from sixteen wild rabbits (WR) were contrasted with two groups (n = 4) of farm rabbits receiving low (LSF) or high (HSF) soluble fibre diets from 28 (weaning) to 51 days of age. DNA was extracted for quantifying bacteria and Archaea by qPCR and for biodiversity analysis of microbial communities by DGGE. Samples from WR had lower caecal pH and ammonia and higher volatile fatty acids concentration than farm animals. Lower acetate and higher butyrate proportions were detected in WR. Bacterial and archaeal DGGE profiles were clearly different between wild and farm rabbits, and diet-affected population of farm rabbits. Similarity index of bacteria was lower than 0.40 among WR, and 0.52 among farm rabbits. In conclusion, caecal fermentation characteristics differ between wild and farm rabbits, which harbour clearly different bacterial and archaeal communities. In farm rabbits, diversity is influenced by the dietary level of soluble fibre.     

Secondary metabolite content in rhizomes, callus cultures and in vitro regenerated plantlets of Solidago chilensis

An in vitro culture system leading to the formation of callus and plant regeneration, starting from nodal sections and shoot tips, was developed for Solidago chilensis (Asteraceae). The content of the gastroprotective diterpene solidagenone as well as the phenolics chlorogenic acid (CA) and rutin was determined either in rhizomes from wild growing plants and in callus and in in vitro regenerated plantlets by analytical HPLC. Additionally, total phenolic and flavonoid content was assessed in plant samples, callus and cell suspensions. In terms of dry starting material, the percentual solidagenone content in nine S. chilensis samples ranged from 0.5-3.5% for rhizomes from wild growing plants, 0.1-0.3% for callus and 0.3% for an in vitro regenerated plantlet, respectively. The highest solidagenone contents were found in the wild plant during the late summer in the months of March and April (3.5-2.2%) while highest values for chlorogenic acid (0.5%) and rutin (0.4%) were detected in May, before senescence. The callus tissue and cell suspensions contained some 1.8-2.0 and 1.2% of total phenolics, respectively. CA was the main phenolic in the cell suspension while only traces were found in the callus. Rutin was not detected in the callus nor cell culture.     

The deletion of the pif gene improves the biosafety of the baculovirus-based technologies

Our goal was to improve the biosafety of baculovirus-based technologies by deleting the pif (per os infectivity factor) gene from baculovirus expression vectors. Such a deletion would block transmission in nature without disturbing protein production. A pif deletion mutant of Autographa californica multiplecapsid nucleopolyhedrovirus (AcMNPV) was constructed and its infectivity to two host species was tested by oral or intrahemocoelic inoculation. Virus replication after oral inoculation was monitored using PCR. Oral inoculations with a mixture of the wild type and the pif deletion viruses were carried out. The pif deletion blocked oral infection but it did not hamper infectivity in cell culture. The blockage took place early after inoculation and could not be overcome by mixed inoculations with the wild type. The cat gene was inserted under the control of the polyhedrin promoter in the deletion mutant and the wild type CAT yield was measured in Spodoptera frugiperda insect cells (Sf9) infected with either recombinant. The pif deletion did not hamper CAT production. This deletion significantly improved CAT yields early in the infection. Hence, expression vectors lacking pif may produce higher quality protein. The pif deletion is a simple measure that dramatically reduces the chances of virus spread or gene transfer in nature.     

Megakaryocytes in rabbit pulmonary blood vessels

Semiserial sections of lung capillaries of seven rabbits were examined for megakaryocytes. Triads of serial sections of each lobe were examined, and megakaryocyte counts per cm2 were determined. Median megakaryocyte count was determined for each lobe. The lobal values were used to calculate the was determined for each lobe. The lobal values were used to calculate the median cell-counts for each experimental animal. Values of 0.16-0.64 megakaryocytes per cm2 were established as "normal".     

Cell culture and animal infection with distinct Trypanosoma cruzi strains expressing red and green fluorescent proteins

Different strains of Trypanosoma cruzi were transfected with an expression vector that allows the integration of green fluorescent protein (GFP) and red fluorescent protein (RFP) genes into the beta-tubulin locus by homologous recombination. The sites of integration of the GFP and RFP markers were determined by pulse-field gel electrophoresis and Southern blot analyses. Cloned cell lines selected from transfected epimastigote populations maintained high levels of fluorescent protein expression even after 6 months of in vitro culture of epimastigotes in the absence of drug selection. Fluorescent trypomastigotes and amastigotes were observed within Vero cells in culture as well as in hearts and diaphragms of infected mice. The infectivity of the GFP- and RFP-expressing parasites in tissue culture cells was comparable to wild type populations. Furthermore, GFP- and RFP-expressing parasites were able to produce similar levels of parasitemia in mice compared with wild type parasites. Cell cultures infected simultaneously with two cloned cell lines from the same parasite strain, each one expressing a distinct fluorescent marker, showed that at least two different parasites are able to infect the same cell. Double-infected cells were also detected when GFP- and RFP-expressing parasites were derived from strains belonging to two distinct T. cruzi lineages. These results show the usefulness of parasites expressing GFP and RFP for the study of various aspects of T. cruzi infection including the mechanisms of cell invasion, genetic exchange among parasites and the differential tissue distribution in animal models of Chagas disease.     

Detection and distribution of rotavirus in raw sewage and creeks in São Paulo, Brazil.

Rotaviruses were concentrated from 8-liter samples of raw domestic sewage and sewage-polluted creek water by adsorption to and elution from positively charged microporous filters (Zeta Plus 60S), followed by ultracentrifugation of the filter eluates. Indirect immunofluorescence and direct immunoperoxidase methods allowed detection and enumeration of rotavirus in 6 (20.6%) of 29 sewage samples and in 19 (34.5%) of 55 creek water samples. Levels of rotaviruses ranged from < 3 to 63 focus-forming units (FFU)/liter, and the geometric means were 2.2 FFU/liter in sewage, 2.9 FFU/liter at creek Tremembé, and 2.6 FFU/liter at creek Pirajussara. Wastewater samples examined during autumn and winter months showed a higher rate positivity for rotavirus than those collected in spring and summer, corresponding to the seasonal variation of rotaviral diarrhea in the city of São Paulo.     

Aerosolized Bacillus anthracis infection in New Zealand white rabbits: natural history and intravenous levofloxacin treatment

The natural history for inhalational Bacillus anthracis (Ames strain) exposure in New Zealand white rabbits was investigated to better identify potential, early biomarkers of anthrax. Twelve SPF Bordetella-free rabbits were exposed to 150 LD(50) aerosolized B. anthracis spores, and clinical signs, body temperature, complete blood count, bacteremia, and presence of protective antigen in the blood (that is, antigenemia) were examined. The development of antigenemia and bacteremia coincided and preceded both pyrexia and inversion of the heterophil:lymphocyte ratio, an indicator of infection. Antigenemia was determined within 1 h by electrochemiluminescence immunoassay, compared with the 24-h traditional culture needed for bacteremia determination. Rabbits appeared clinically normal until shortly before succumbing to anthrax approximately 47 h after challenge or approximately 22 h after antigenemia, which suggests a relatively narrow therapeutic window of opportunity. To evaluate the therapeutic rabbit model, B. anthracis-exposed rabbits were treated (after determination of antigenemia and later confirmed to be bacteremic) intravenously with the fluoroquinolone antibiotic levofloxacin for 5 d at a total daily dose of 25 or 12.5 mg/kg, resulting in nearly 90% and 70% survival, respectively, to the study end (28 d after challenge). The peak level for 12.5 mg/kg was equivalent to that observed for a 500-mg daily levofloxacin dose in humans. These results suggest that intravenous levofloxacin is an effective therapeutic against inhalational anthrax. Taken together, our findings indicate that antigenemia is a viable and early biomarker for B. anthracis infection that can be used as a treatment trigger to allow for timely intervention against this highly pathogenic disease.