Safety and immunogenicity of a purified inactivated Zika virus vaccine candidate in adults primed with a Japanese encephalitis virus or yellow fever virus vaccine in the USA: a phase 1, randomised, double-blind, placebo-controlled clinical trial.

BACKGROUND: Zika virus infection is a threat to at-risk populations, causing major birth defects and serious neurological complications. Development of a safe and efficacious Zika virus vaccine is, therefore, a global health priority. Assessment of heterologous flavivirus vaccination is important given co-circulation of Japanese encephalitis virus and yellow fever virus with Zika virus. We investigated the effect of priming flavivirus naive participants with a licensed flavivirus vaccine on the safety and immunogenicity of a purified inactivated Zika vaccine (ZPIV). METHODS: This phase 1, placebo-controlled, double-blind trial was done at the Walter Reed Army Institute of Research Clinical Trials Center in Silver Spring, MD, USA. Eligible participants were healthy adults aged 18-49 years, with no detectable evidence of previous flavivirus exposure (by infection or vaccination), as measured by a microneutralisation assay. Individuals with serological evidence of HIV, hepatitis B, or hepatitis C infection were excluded, as were pregnant or breastfeeding women. Participants were recruited sequentially into one of three groups (1:1:1) to receive no primer, two doses of intramuscular Japanese encephalitis virus vaccine (IXIARO), or a single dose of subcutaneous yellow fever virus vaccine (YF-VAX). Within each group, participants were randomly assigned (4:1) to receive intramuscular ZPIV or placebo. Priming vaccinations were given 72-96 days before ZPIV. ZPIV was administered either two or three times, at days 0, 28, and 196-234. The primary outcome was occurrence of solicited systemic and local adverse events along with serious adverse events and adverse events of special interest. These data were analysed in all participants receiving at least one dose of ZPIV or placebo. Secondary outcomes included measurement of neutralizing antibody responses following ZPIV vaccination in all volunteers with available post-vaccination data. This trial is registered at ClinicalTrials.gov, NCT02963909. FINDINGS: Between Nov 7, 2016, and Oct 30, 2018, 134 participants were assessed for eligibility. 21 did not meet inclusion criteria, 29 met exclusion criteria, and ten declined to participate. 75 participants were recruited and randomly assigned. 35 (47%) of 75 participants were male and 40 (53%) were female. 25 (33%) of 75 participants identified as Black or African American and 42 (56%) identified as White. These proportions and other baseline characteristics were similar between groups. There were no statistically significant differences in age, gender, race, or BMI between those who did and did not opt into the third dose. All participants received the planned priming IXIARO and YF-VAX vaccinations, but one participant who received YF-VAX dropped out before receipt of the first dose of ZPIV. 50 participants received a third dose of ZPIV or placebo, including 14 flavivirus-naive people, 17 people primed with Japanese encephalitis virus vaccine, and 19 participants primed with yellow fever vaccine. Vaccinations were well tolerated across groups. Pain at the injection site was the only adverse event reported more frequently in participants who received ZPIV than in those who received placebo (39 [65%] of 60 participants, 95% CI 51·6-76·9 who received ZPIV vs three [21·4%] of 14 who received placebo; 4·7-50·8; p=0·006). No patients had an adverse event of special interest or serious adverse event related to study treatment. At day 57, the flavivirus-naive volunteers had an 88% (63·6-98·5, 15 of 17) seroconversion rate (neutralising antibody titre ≥1:10) and geometric mean neutralising antibody titre (GMT) against Zika virus of 100·8 (39·7-255·7). In the Japanese encephalitis vaccine-primed group, the day 57 seroconversion rate was 31·6% (95% CI 12·6-56·6, six of 19) and GMT was 11·8 (6·1-22·8). Participants primed with YF-VAX had a seroconversion rate of 25% (95% CI 8·7-49·1, five of 20) and GMT of 6·6 (5·2-8·4). Humoral immune responses rose substantially following a third dose of ZPIV, with seroconversion rates of 100% (69·2-100; ten of ten), 92·9% (66·1-99·8; 13 of 14), and 60% (32·2-83·7, nine of 15) and GMTs of 511·5 (177·6-1473·6), 174·2 (51·6-587·6), and 79 (19·0-326·8) in the flavivirus naive, Japanese encephalitis vaccine-primed, and yellow fever vaccine-primed groups, respectively. INTERPRETATION: We found ZPIV to be well tolerated in flavivirus naive and primed adults but that immunogenicity varied significantly according to antecedent flavivirus vaccination status. Immune bias towards the flavivirus antigen of initial exposure and the timing of vaccination may have impacted responses. A third ZPIV dose overcame much, but not all, of the discrepancy in immunogenicity. The results of this phase 1 clinical trial have implications for further evaluation of ZPIV's immunisation schedule and use of concomitant vaccinations. FUNDING: Department of Defense, Defense Health Agency; National Institute of Allergy and Infectious Diseases; and Division of Microbiology and Infectious Disease.

Immunogenicity of a Live-Attenuated Dengue Vaccine Using a Heterologous Prime-Boost Strategy in a Phase 1 Randomized Clinical Trial.

BACKGROUND: Dengue is a global health problem and the development of a tetravalent dengue vaccine with durable protection is a high priority. A heterologous prime-boost strategy has the advantage of eliciting immune responses through different mechanisms and therefore may be superior to homologous prime-boost strategies for generating durable tetravalent immunity. METHODS: In this phase 1 first-in-human heterologous prime-boost study, 80 volunteers were assigned to 4 groups and received a tetravalent dengue virus (DENV-1-4) purified inactivated vaccine (TDENV-PIV) with alum adjuvant and a tetravalent dengue virus (DENV-1-4) live attenuated vaccine (TDENV-LAV) in different orders and dosing schedules (28 or 180 days apart). RESULTS: All vaccination regimens had acceptable safety profiles and there were no vaccine-related serious adverse events. TDEN-PIV followed by TDEN-LAV induced higher neutralizing antibody titers and a higher rate of tetravalent seroconversions compared to TDEN-LAV followed by TDEN-PIV. Both TDEN-PIV followed by TDEN-LAV groups demonstrated 100% tetravalent seroconversion 28 days following the booster dose, which was maintained for most of these subjects through the day 180 measurement. CONCLUSIONS: A heterologous prime-boost vaccination strategy for dengue merits additional evaluation for safety, immunogenicity, and potential for clinical benefit. CLINICAL TRIALS REGISTRATION: NCT02239614.

Safety and Immunogenicity of an AS03B-Adjuvanted Inactivated Tetravalent Dengue Virus Vaccine Administered on Varying Schedules to Healthy U.S. Adults: A Phase 1/2 Randomized Study.

Dengue disease and its causative agents, the dengue viruses (DENV-1-4), cause high morbidity in tropical and subtropical regions. We evaluated three dosing regimens of the investigational tetravalent AS03B-adjuvanted dengue-purified inactivated vaccine (DPIV+AS03B). In this phase 1/2, observer-blind, placebo-controlled study (NCT02421367), 140 healthy adults were randomized 1:1:2 to receive DPIV+AS03B according to the following regimens: 0-1 month (M), 0-1-6 M, or 0-3 M. Participants received DPIV+AS03B or placebo at M0, M1, M3, and M6 according to their dosing schedule. Primary objectives were 1) to evaluate the safety of DPIV+AS03B for 28 days (D) after each dose; 2) to demonstrate the added value of a booster dose (0-1-6 M versus 0-1 M) based on neutralizing antibody titers to each DENV type (DENV-1-4) at 28 D after the last dose; and, if this objective was met, 3) to demonstrate the benefit of a longer interval between the first and second doses (0-1 M versus 0-3 M). Adverse events (AEs) within 7 D after vaccination tended to be more frequent after DPIV+AS03B doses than placebo; the number of grade 3 AEs was low (≤ 4.5% after DPIV+AS03B; ≤ 2.9% after placebo), with no obvious differences across groups. Within 28 D following each dose, the frequency of unsolicited AEs after DPIV+AS03B appeared higher for three-dose (0-1-6 M) than two-dose (0-1 M and 0-3 M) regimens. No serious AEs were considered related to vaccination, and no potential immune-mediated diseases were reported during the study. All three schedules were well tolerated. Both primary immunogenicity objectives were demonstrated. The 0-3 M and 0-1-6 M regimens were more immunogenic than the 0-1 M regimen.

Serologic Response of 2 Versus 3 Doses and Intradermal Versus Intramuscular Administration of a Licensed Rabies Vaccine for Preexposure Prophylaxis.

BACKGROUND: The World Health Organization recommends intradermal (ID) administration of rabies vaccine for preexposure prophylaxis. METHODS: In a randomized trial in adults assigned to 1 of 6 treatment groups (ID vs intramuscular [IM], 2 vs 3 doses, and controls), rabies neutralizing antibody titers were measured to 1 year postvaccination. RESULTS: ID vaccination produced acceptable antibody levels in all subjects (2- and 3-dose groups). At day 365, acceptable levels were 40% for IM and 50% for ID 2-dose schedule, and 70% for IM and 60% for ID 3-dose schedule. CONCLUSIONS: ID rabies vaccination induces acceptable antibody titers at a fraction of the dose. CLINICAL TRIALS REGISTRATION: NCT02374814.

Effect of Antimalarial Drugs on the Immune Response to Intramuscular Rabies Vaccination Using a Postexposure Prophylaxis Regimen.

BACKGROUND: Chloroquine can impair the immune responses to intradermal rabies vaccination. Current guidelines recommend an extra intramuscular dose be given for postexposure prophylaxis in previously unvaccinated persons taking any antimalarial drug. METHODS: We conducted a randomized, open-label, single-site study in 103 previously unvaccinated healthy adults age ≥18 to ≤60 years old to evaluate the effects of chloroquine, atovaquone/proguanil (Malarone), and doxycycline on the antibody response to a purified chick embryo cell vaccine, given on a postexposure prophylaxis schedule. All treatment groups received antimalarials 14 days prior to and during vaccination. RESULTS: All subjects achieved accepted neutralizing antibody titers of ≥0.5 IU/mL following the second rabies vaccination dose and maintained this protection through the duration of the study. We observed a reduction in rabies antibody geometric mean titer in the chloroquine versus control groups 28 days after vaccination: 2.3 versus 6.87 IU/mL, respectively (P < .001, t test). A significant difference was not observed for those taking Malarone or doxycycline. CONCLUSIONS: We conclude that there is no reduction of rabies antibody response in subjects taking Malarone or doxycycline, but a significant reduction in those taking chloroquine; however, accepted antibody levels were achieved for all 3 antimalarials. CLINICAL TRIALS REGISTRATION: NCT02564471.

Canine caliciviruses of four serotypes from military and research dogs recovered in 1963-1978 belong to two phylogenetic clades in the Vesivirus genus.

BACKGROUND: Vesiviruses (family Caliciviridae) had been shown capable of invading a variety of host species, raising concern of their zoonotic potential. Since the 1980's, several canine caliciviruses (CaCV) isolates have been reported and are phylogenetically related to the vesiviruses with features distinct from both Vesicular exanthema of swine virus (VESV) and Feline calicivirus (FCV) species in phylogeny, serology and cell culture specificities. Etiological studies of canine diseases in dogs used for military services and laboratory studies were conducted in 1963-1978 at the Walter Reed Army Institute of Research. Multiple known and unknown viral pathogens including caliciviruses were recovered. METHODS: Four unidentified isolates were recovered in Walter Reed Canine Cells (WRCC) from respiratory, fecal and penile specimens. Physicochemical tests, electron microscopy, viral cultivation in human and animal cells, antibody neutralization assays, and recently the genome sequencing were used to characterize the isolates. Sera from these dogs and their cohorts were tested with the isolates to determine origin and prevalence of the infections. RESULTS: The viral isolates were small non-enveloped spherical RNA virions, 27 to 42 nm in diameter with cup-like structures, indicating they are caliciviruses. They propagated in WRCC and MDCK cells, not in either other canine cells or human and other animal cells. Each isolate is antigenically distinct and react with dog sera in respective cohorts. The genomes have nucleotide identities ranging from 70.3% to 90.7% and encode the non-structural polyprotein (1810 amino acids), major capsid protein (691 amino acids) and minor structural protein (134 amino acids). They belong to two different phylogenetic clades in Vesivirus genus with close relation with canine calicivirus (CaCV). CONCLUSIONS: These CaCV isolates have restricted cell tropism, antigenic diversity and genetic variation. Further investigation will shed light on antigenic relation to other vesiviruses, and its pathogenicity for dogs and potential infectivity to other animals. Together with the previously reported CaCV strains provides significant evidence to support the formation of a new CaCV species in the Vesivirus genus.

Composition and variation of respiratory microbiota in healthy military personnel.

Certain occupational and geographical exposures have been associated with an increased risk of lung disease. As a baseline for future studies, we sought to characterize the upper respiratory microbiomes of healthy military personnel in a garrison environment. Nasal, oropharyngeal, and nasopharyngeal swabs were collected from 50 healthy active duty volunteers eight times over the course of one year (1107 swabs, completion rate = 92.25%) and subjected to pyrosequencing of the V1-V3 region of 16S rDNA. Respiratory bacterial taxa were characterized at the genus level, using QIIME 1.8 and the Ribosomal Database Project classifier. High levels of Staphylococcus, Corynebacterium, and Propionibacterium were observed among both nasal and nasopharyngeal microbiota, comprising more than 75% of all operational taxonomical units (OTUs). In contrast, Streptococcus was the sole dominant bacterial genus (approximately 50% of all OTUs) in the oropharynx. The average bacterial diversity was greater in the oropharynx than in the nasal or nasopharyngeal region at all time points. Diversity analysis indicated a significant overlap between nasal and nasopharyngeal samples, whereas oropharyngeal samples formed a cluster distinct from these two regions. The study produced a large set of pyrosequencing data on the V1-V3 region of bacterial 16S rDNA for the respiratory microbiomes of healthy active duty Service Members. Pre-processing of sequencing reads showed good data quality. The derived microbiome profiles were consistent both internally and with previous reports, suggesting their utility for further analyses and association studies based on sequence and demographic data.

Genome Sequence of a Novel Canine Picornavirus Isolated from an American Foxhound.

A candidate new canine picornavirus was isolated from a respiratory swab collected from an American foxhound (Canis lupus familiaris) in 1968. The assembled genome sequence of strain A128thr is 7,618 bases in length, comprising a complete protein-coding sequence of the 2,213-amino-acid polyprotein and partial terminal untranslated sequences.

Adenovirus type 4 respiratory infections with a concurrent outbreak of coxsackievirus A21 among United States Army Basic Trainees, a retrospective viral etiology study using next-generation sequencing.

Human adenoviruses (HAdV), in particular types 4 and 7, frequently cause acute respiratory disease (ARD) during basic military training. HAdV4 and HAdV7 vaccines reduced the ARD risk in U.S. military. It is important to identify other respiratory pathogens and assess their potential impact on military readiness. In 2002, during a period when the HAdV vaccines were not available, throat swabs were taken from trainees (n = 184) with respiratory infections at Fort Jackson, South Carolina. Viral etiology was investigated initially with viral culture and neutralization assay and recently in this study by sequencing the viral isolates. Viral culture and neutralization assays identified 90 HAdV4 isolates and 27 additional cultures that showed viral cytopathic effects (CPE), including some with picornavirus-like CPE. Next-generation sequencing confirmed these results and determined viral genotypes, including 77 HAdV4, 4 HAdV3, 1 HAdV2, 17 coxsackievirus A21 (CAV21), and 1 enterovirus D68. Two samples were positive for both HAdV4 and CAV21. The identified genotypes are phylogenetically close to but distinct from those found during other years or in other military/non-military sites. HAdV4 is the predominant respiratory pathogen in unvaccinated military trainee. HAdV4 has temporal and demographic variability. CAV21 is a significant respiratory pathogen and needs to be evaluated for its current significance in military basic trainees.

Meningococcal polysaccharide vaccine failure in a patient with C7 deficiency and a decreased anti-capsular antibody response.

A 20-y-old male presented with symptoms of meningococcal sepsis and died despite appropriate medical interventions. Blood cultures grew N. meningitidis serogroup Y. The patient had received the meningococcal quadrivalent (A,C,W-135,Y) polysaccharide vaccine 15 mo previously. Because the patient had a history of meningococcal meningitis at age 10, archived serum was obtained for further analysis. Complement component C7 was found to be deficient, and antibody levels to meningococcal polysaccharides were undetectable for two serogroups and low for the infecting serogroup 10 mo post-vaccination. This case highlights the fact that some individuals with terminal complement component deficiencies mount an impaired or short-lived response to vaccination with meningococcal capsular polysaccharides, and underscores the appropriateness of a more aggressive vaccination strategy in this patient population.

Importance of antibodies to lipopolysaccharide in natural and vaccine-induced serum bactericidal activity against Neisseria meningitidis group B.

Analysis of the specificity of bactericidal antibodies in normal, convalescent, and postvaccination human sera is important in understanding human immunity to meningococcal infections and can aid in the design of an effective group B vaccine. A collection of human sera, including group C and group B convalescent-phase sera, normal sera with naturally occurring cross-reactive bactericidal activity, and some postvaccination sera, was analyzed to determine the specificity of cross-reactive bactericidal antibodies. Analysis of human sera using a bactericidal antibody depletion assay demonstrated that a significant portion of the bactericidal activity could be removed by purified lipopolysaccharide (LPS). LPS homologous to that expressed on the bactericidal test strain was most effective, but partial depletion by heterologous LPS suggested the presence of antibodies with various degrees of cross-reactivity. Binding of anti-L3,7 LPS bactericidal antibodies was affected by modification of the core structure, suggesting that these functional antibodies recognized epitopes consisting of both core structures and lacto-N-neotetraose (LNnT). When the target strain was grown with 5'-cytidinemonophospho-N-acetylneuraminic acid (CMP-NANA) to increase LPS sialylation, convalescent-phase serum bactericidal titers were decreased by only 2- to 4-fold, and most remaining bactericidal activity was still depleted by LPS. Highly sialylated LPS was ineffective in depleting bactericidal antibodies. We conclude that natural infections caused by strains expressing L3,7 LPS induce persistent, protective bactericidal antibodies and appear to be directed against nonsialylated bacterial epitopes. Additionally, subsets of these bactericidal antibodies are cross-reactive, binding to several different LPS immunotypes, which is a useful characteristic for an effective group B meningococcal vaccine antigen.

Safety and immunogenicity of an intranasal Shigella flexneri 2a Invaplex 50 vaccine.

BACKGROUND: Shigella flexneri 2a lipopolysaccharide 50 is a nasally delivered subunit vaccine consisting of a macromolecular complex composed of LPS, IpaB, IpaC and IpaD. The current study examined vaccine safety and immunogenicity across a dose range and the clinical performance of a new intranasal delivery device. METHODS: Volunteers (N=36) were randomized to receive vaccine via the Dolphin™ (Valois of America, Congers, New York) intranasal spray device at one of three doses (240, 480, and 690 µg) on days 0, 14, and 28. Another group (N=8) received the 240 µg dose via pipette. Vaccine safety was actively monitored and antigen-specific humoral and mucosal immune responses were determined. RESULTS: There were no serious adverse events and the majority of adverse events (98%) were mild. Antibody secreting cells (ASC), plasma, and mucosal immune responses to Shigella antigens were detected at all three dose levels with the 690 µg dose inducing the highest magnitude and frequency of responses. Vaccination with comparable doses of Invaplex 50 via the Dolphin™ resulted in higher plasma and ASC immune responses as compared to pipette delivery. CONCLUSION: In this trial the S. flexneri 2a Invaplex 50 vaccine was safe, well-tolerated and induced robust levels of antigen-specific intestinal IgA and ASC responses. The spray device performed well and offered an advantage over pipette intranasal delivery.

U.S. military fatalities due to Neisseria meningitidis: case reports and historical perspective.

Meningococcal disease has historically been associated with military populations, particularly during periods of mobilization. Although the U.S. military has now been engaged in conflicts for nearly a decade, the incidence of meningococcal disease in the U.S. population as a whole has reached historic lows. Despite vaccination of all service members in basic military training, the risk of meningococcal disease appears to be equal to or greater than that of the civilian population. These 3 case reports of recent fatalities in the U.S. military and their historic contexts illustrate the circumstances under which meningococcus can strike and highlight the need for continued vigilance in military populations.

A phase 1 study of a group B meningococcal native outer membrane vesicle vaccine made from a strain with deleted lpxL2 and synX and stable expression of opcA.

This phase 1 clinical trial assessed the safety and immunogenicity of a native outer membrane vesicle (NOMV) vaccine prepared from a lpxL2(-) synX(-) mutant of strain 44/76 with opcA expression stabilized. Thirty-four volunteers were assigned to one of the three dose groups (25 mcg, 25 mcg with aluminum hydroxide adjuvant, and 50 mcg) to receive three intramuscular injections at 0, 6 and 24 weeks. Specific local and systemic adverse events (AEs) were solicited by diary and at visits on days 1, 2, 7 and 14 after each vaccination and at the end of the study at 30 weeks. Blood chemistries, complete blood count, and coagulation studies were measured on each vaccination day and again two days later. Blood for antibody measurements and bactericidal assays were drawn 0, 14, and 42 days after each vaccination. The proportion of volunteers who developed a fourfold or greater increase in serum bactericidal activity (SBA) to the wild-type parent of the vaccine strain with high opcA expression at 6 weeks after the third dose was 12/26 (0.46, 95% confidence interval 0.27-0.65). Antibody levels to OpcA were significantly higher in vaccine responders than in non-responders (p=0.008), and there was a trend for higher antibody levels to the lipooligosaccharide (LOS) (p=0.059). Bactericidal depletion assays on sera from volunteers with high-titer responses also indicate a major contribution of anti-OpcA and anti-LOS antibodies to the bactericidal response.These results suggest that genetically modified NOMV vaccines can induce protection against group B meningococcus.

Design and evaluation in mice of a broadly protective meningococcal group B native outer membrane vesicle vaccine.

A vaccine based on native outer membrane vesicles (NOMV) that has potential to provide safe, broad based protection against group B strains of Neisseria meningitidis has been developed. Three antigenically diverse group B strains of N. meningitidis were chosen and genetically modified to improve safety and expression of desirable antigens. Safety was enhanced by disabling three genes: synX, lpxL1, and lgtA. The vaccine strains were genetically configured to have three sets of antigens each with potential to induce protective antibodies against a wide range of group B strains. Preliminary immunogenicity studies with combined NOMV from the three strains confirmed the capacity of the vaccine to induce a broad based bactericidal antibody response. Analysis of the bactericidal activity indicated that antibodies to the LOS were responsible for a major portion of the bactericidal activity and that these antibodies may enhance the bactericidal activity of anti-protein antibodies.

Whole cell vaccination for meningococcus: Lessons from an idea whose time has gone.

Endotoxin in vaccines has long been recognized as a cause of adverse events and is generally regarded as a contaminant. However there are now a number of vaccine candidates that contain endotoxin as either antigen or adjuvant, particularly vaccines for Neisseria meningitidis based on native outer membrane vesicles (NOMV). Vaccines containing meningococcal endotoxin are not new. From 1907 to 1939 approximately 400,000 individuals were immunized with whole cell vaccines against meningococcus. We reviewed reports of meningococcal vaccinations from this period to characterize the adverse events in order to draw a baseline for evaluating meningococcal NOMV vaccines. The majority of these investigators conclude that whole cell vaccination was well tolerated with an adverse event profile comparable to other whole cell vaccines for Gram negative pathogens. There is insufficient data to draw conclusions on the duration of protection, if any, induced by whole cell meningococcal vaccines.

Evaluation of a whole-blood cytokine release assay for use in measuring endotoxin activity of group B Neisseria meningitidis vaccines made from lipid A acylation mutants.

Bacterial endotoxin interacts with the human immune system via complex immunological pathways. The evaluation of endotoxicity is important in the development of safe vaccines and immunomodulatory therapeutics. The Limulus amebocyte lysate (LAL) assay is generally accepted by the FDA for use for the quantification of lipopolysaccharide (LPS), while the rabbit pyrogen test (RPT) is used to estimate pyrogenicity during early development and production. Other in vitro assays, such as cytokine release assays with human whole blood (WB) or peripheral blood mononuclear cells (PBMCs), have also been used and may better estimate the human immunological response to products containing novel LPS molecules. In this study, WB and PBMC interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) release assays were used to estimate the endotoxic activities of purified LPS and native outer membrane vesicle (NOMV) vaccines derived from wild-type (hexa-acylated lipid A) and genetically detoxified (penta- and tetra-acylated lipid A) group B Neisseria meningitidis. A method for quantification of the differences in endotoxicity observed in the WB and PBMC assays is elucidated. The LAL assay was shown to be relatively insensitive to lipid A variations, and the RPT was less sensitive than the cytokine release assay with WB. The IL-6 and TNF-alpha assays with WB but not the assays with PBMCs distinguished between vaccines containing LPS from penta- and tetra-acylated strains. The high degree of sensitivity of the WB system to LPS variations and the presumed relevance of the use of human tissues to predict toxicity in humans suggest that this assay may be particularly well suited for the safety evaluation of vaccines and therapeutics containing acylation variants of LPS.

Plasma fibrinogen levels after vaccination with a native outer membrane vesicle vaccine for Neisseria meningitidis.

Several studies have shown plasma fibrinogen increases following some vaccinations, but the specific triggers and the kinetics of this response are not well understood. We conducted a phase I trial of an outer membrane vesicle vaccine for Neisseria meningitidis. Plasma fibrinogen was measured on days 0, 2 and 14 following each of 3 doses. The highest dose of vaccine was associated with the greatest increase in fibrinogen at day 2, which decreased by day 14. The first vaccination caused a greater increase than either subsequent vaccination. These transient increases in fibrinogen are comparable to what occurs with upper respiratory infections and have not been demonstrated to represent an increased risk of adverse vascular events.