Persistence of Immunogenicity of a Monovalent Influenza Virus A/H1N1 2009 Vaccine in Healthy Volunteers

After WHO declared H1N1 pandemic, global vaccination was carried out immediately after much research. However, the data on long-term immunogenicity were lacking. We aimed to investigate the long-term immunogenicity of different H1N1 vaccine dosage groups 24 weeks after vaccination by a randomized clinical trial. A total of 218 participants were stratified into adult (≤60 years old) and elderly (>60 years old) groups. The adults were randomized in a 1:1:1 ratio. The first group received a single dose of vaccine with 15 μg hemagglutination antigen (HA). The other two groups received two doses with 15 μg or 30 μg HA triweekly. The elderly were randomized 1:1 for two doses of 15 or 30 μg HA. We evaluated serologic responses at prevaccination and weeks 3, 6, and 24. We also examined possible associated factors of immunogenicity by multivariate logistic regression analyses. At week 24, seroprotection (anti-HA antibody level ≥ 1:40) remained at 76.8% and 46.2% in the adult and elderly groups, respectively. The adult group had a higher seroprotection rate (odds ratio of 2.98, 95% confidence interval [CI]: 1.21 to 7.36) than the elderly group. There was no statistical difference in seroprotection and seroconversion rates between different adult and elderly dosage groups. Lower immunogenicity in the elderly than in the adults 24 weeks after the vaccination was observed. However, there was no statistically significant difference among different dose groups. Therefore, we suggest only a single vaccination dose of 15 μg HA for adults and two doses of 15 μg HA for the elderly in the future.     

Phase I study of a herpes simplex virus type 2 (HSV-2) DNA vaccine administered to healthy, HSV-2-seronegative adults by a needle-free injection system

We conducted a double-blind, vehicle-controlled, dose escalation safety and immunogenicity trial of a candidate herpes simplex virus type 2 (HSV-2) surface glycoprotein D2 (gD2) DNA vaccine administered by use of a needle-free device. Sixty-two healthy adults were randomized using a 4:1 vaccine-to-placebo ratio. Half of the participants were HSV-1 seronegative, and all were HSV-2 seronegative. Vaccine doses included 100 μg, 300 μg, 1,000 μg or 3,000 μg of a plasmid expressing the gD2 protein. Subjects received vaccine at 0, 4, 8, and 24 weeks. Some subjects received an additional 1,000-μg boost at 52 weeks. We found that the vaccine was safe and well tolerated, with most adverse events being local site reactions. No dose-limiting toxicities were observed. gD2-specific cytotoxic T-lymphocyte and lymphoproliferation responses were detected 2 weeks after the third vaccine injection in one of four HSV-1-seronegative, HSV-2-seronegative participants who received 3,000 μg of vaccine. A DNA-based vaccination strategy against HSV-2 appears to be safe and may generate a vaccine-specific cellular immune response, but high vaccine doses are likely needed to elicit an immune response in most vaccinees.     

An Inactivated,Adjuvanted Whole Virion Clade 2.2 H5N1 (A/Chicken/Astana/6/05) Influenza Vaccine Is Safe and Immunogenic in a Single Dose in Humans

In this study, we assessed in humans the immunogenicity and safety of one dose (7.5 or 15 μg of hemagglutinin [HA]) of a whole-virion inactivated prepandemic influenza vaccine adjuvanted with aluminum hydroxide. The vaccine strain was made by reverse genetics from the highly pathogenic avian A/Chicken/Astana/6/05 (H5N1) clade 2.2 strain isolated from a dead bird in Kazakhstan. The humoral immune response was evaluated after a single vaccination by hemagglutination inhibition (HI) and microneutralization (MN) assays. The vaccine was safe and immunogenic, inducing seroconversion in 55% of the evaluated patients, with a geometric mean titer (GMT) of 17.1 and a geometric mean increase (GMI) of 3.42 after a dose of 7.5 μg in the HI test against the vaccine strain. The rate of seroconversion increased up to 70% when the dose of 15 μg was used. The percentages of individuals achieving anti-HA titers of ≥1:40 were 52.5% and 57.5% for the 7.5- and 15-μg dose groups, respectively. Similar results were obtained when antibodies were analyzed in an MN test. Substantial cross-neutralization titers (seroconversion in 35% and 52.5% of subjects in the two dose groups, respectively) were detected against heterologous clade 1 strain NIBRG14 (H5N1). Thus, one dose of this whole-virion prepandemic vaccine adjuvanted with aluminum has the potential to be effective against H5N1 viruses of different clades.     

A Reduced-Dose Seasonal Trivalent Influenza Vaccine Is Safe and Immunogenic in Adult and Elderly Patients in a Randomized Controlled Trial

With the recent pandemic of influenza A (H1N1) and vaccine shortages, there has been considerable interest in developing influenza vaccines with reduced doses, allowing for increased production capacity. Here we report a prospective, randomized, double-blind, single-center clinical trial of a reduced-dose whole-virion inactivated, adjuvanted influenza vaccine in adult and elderly volunteers. A total of 234 subjects, including 120 adults (18 to 60 years of age) and 114 elderly subjects (>60 years of age) were enrolled to receive either 6 μg or the conventional 15-μg dose of seasonal trivalent influenza vaccines. The subjects were followed for safety analysis, and serum samples were obtained to assess immunogenicity by hemagglutination inhibition testing. The subjects developed antibody responses against the seasonal influenza A virus H1N1 and H3N2 strains, as well as the seasonal influenza B virus included in the vaccines. Single doses of 6 μg fulfilled licensing criteria for seasonal influenza vaccines. No significant differences in rates of seroconversion or seroprotection or in geometric mean titers were found between the two dosage levels. All adverse events were rare, mild, and transient. We found that the present reduced-dose vaccine is safe and immunogenic in healthy adult and elderly subjects and triggers immune responses that comply with licensing criteria.     

Virus-Like Particle Vaccine Confers Protection against a Lethal Newcastle Disease Virus Challenge in Chickens and Allows a Strategy of Differentiating Infected from Vaccinated Animals

In this study, we developed Newcastle disease virus (NDV) virus-like particles (VLPs) expressing NDV fusion (F) protein along with influenza virus matrix 1 (M1) protein using the insect cell expression system. Specific-pathogen-free chickens were immunized with oil emulsion NDV VLP vaccines containing increasing dosages of VLPs (0.4, 2, 10, or 50 μg of VLPs/0.5-ml dose). Three weeks after immunization, the immunogenicity of the NDV VLP vaccines was determined using a commercial enzyme-linked immunosorbent assay (ELISA) kit, and a lethal challenge using a highly virulent NDV strain was performed to evaluate the protective efficacy of the NDV VLP vaccines. NDV VLP vaccines elicited anti-NDV antibodies and provided protection against a lethal challenge in a dose-dependent manner. Although the VLP vaccines containing 0.4 and 2 μg of VLPs failed to achieve high levels of protection, a single immunization with NDV VLP vaccine containing 10 or 50 μg could fully protect chickens from a lethal challenge and greatly reduced challenge virus shedding. Furthermore, we could easily differentiate infected from vaccinated animals (DIVA) using the hemagglutination inhibition (HI) test. These results strongly suggest that utilization of NDV VLP vaccine in poultry species may be a promising strategy for the better control of NDV.     

Immunogenicity of whole cell and outer envelope leptospiral vaccines in hamsters

The immunogenicity of leptospiral whole cell (WC) and outer envelope (OE) vaccines from virulent and avirulent strains was compared in hamsters. The 50% protective dose against death (PD_50D) and kidney infection (PD_50K) was evaluated for serotypes icterohaemorrhagiae, canicola, pomona, and grippotyphosa. The OE and WC of virulent strains possessed greater immunogenicity than the OE and WC of avirulent strains. More vaccine (<0.1 to 11.0 μg [dry weight] per hamster) was required for the PD_50K than for the PD_50D (<0.1 to 1.7 μg [dry weight] per hamster). The OE from virulent strains of these four serotypes plus hardjo were combined to form a pentavalent OE vaccine which proved to be satisfactory in immunogenic potency. Duration of immunity was not evaluated.     

Protective T Cell and Antibody Immune Responses against Hepatitis C Virus Achieved Using a Biopolyester-Bead-Based Vaccine Delivery System

Hepatitis C virus (HCV) infection is a major worldwide problem. Chronic hepatitis C is recognized as one of the major causes of cirrhosis, hepatocellular carcinoma, and liver failure. Although new, directly acting antiviral therapies are suggested to overcome the low efficacy and adverse effects observed for the current standard of treatment, an effective vaccine would be the only way to certainly eradicate HCV infection. Recently, polyhydroxybutyrate beads produced by engineered Escherichia coli showed efficacy as a vaccine delivery system. Here, an endotoxin-free E. coli strain (ClearColi) was engineered to produce polyhydroxybutyrate beads displaying the core antigen on their surface (Beads-Core) and their immunogenicity was evaluated in BALB/c mice. Immunization with Beads-Core induced gamma interferon (IFN-γ) secretion and a functional T cell immune response against the HCV Core protein. With the aim to target broad T and B cell determinants described for HCV, Beads-Core mixed with HCV E1, E2, and NS3 recombinant proteins was also evaluated in BALB/c mice. Remarkably, only three immunization with Beads-Core+CoE1E2NS3/Alum (a mixture of 0.1 μg Co.120, 16.7 μg E1.340, 16.7 μg E2.680, and 10 μg NS3 adjuvanted in aluminum hydroxide [Alum]) induced a potent antibody response against E1 and E2 and a broad IFN-γ secretion and T cell response against Core and all coadministered antigens. This immunological response mediated protective immunity to viremia as assessed in a viral surrogate challenge model. Overall, it was shown that engineered biopolyester beads displaying foreign antigens are immunogenic and might present a particulate delivery system suitable for vaccination against HCV.     

Characterization of an Experimental Vaccine for Bovine Respiratory Syncytial Virus

Bovine respiratory syncytial virus (BRSV) and human respiratory syncytial virus (HRSV) are major causes of respiratory disease in calves and children, respectively, and are priorities for vaccine development. We previously demonstrated that an experimental vaccine, BRSV-immunostimulating complex (ISCOM), is effective in calves with maternal antibodies. The present study focuses on the antigenic characterization of this vaccine for the design of new-generation subunit vaccines. The results of our study confirmed the presence of membrane glycoprotein (G), fusion glycoprotein (F), and nucleoprotein (N) proteins in the ISCOMs, and this knowledge was extended by the identification of matrix (M), M2-1, phosphoprotein (P), small hydrophobic protein (SH) and of cellular membrane proteins, such as the integrins α_Vβ₁, α_Vβ₃, and α₃β₁. The quantity of the major protein F was 4- to 5-fold greater than that of N (∼77 μg versus ∼17 μg/calf dose), whereas G, M, M2-1, P, and SH were likely present in smaller amounts. The polymerase (L), M2-2, nonstructural 1 (NS1), and NS2 proteins were not detected, suggesting that they are not essential for protection. Sera from the BRSV-ISCOM-immunized calves contained high titers of IgG antibody specific for F, G, N, and SH. Antibody responses against M and P were not detected; however, this does not exclude their role in protective T-cell responses. The absence of immunopathological effects of the cellular proteins, such as integrins, needs to be further confirmed, and their possible contribution to adjuvant functions requires elucidation. This work suggests that a combination of several surface and internal proteins should be included in subunit RSV vaccines and identifies absent proteins as potential candidates for differentiating infected from vaccinated animals.     

Functional Antibody Activity Elicited by Fractional Doses of Haemophilus influenzae Type b Conjugate Vaccine (Polyribosylribitol Phosphate–Tetanus Toxoid Conjugate)

We evaluated the functional activities of antibodies, serum bactericidal activity (SBA), and immunoglobulin G (IgG) antibody avidity indices, using sodium thiocyanate (NaSCN) elution, elicited after vaccination with fractional doses of the Haemophilus influenzae type b conjugate (polyribosylribitol phosphate [PRP] conjugated to tetanus toxoid [PRP-T]) vaccine. A cohort of 600 infants from the Dominican Republic were randomized to receive one of three regimens of the PRP-T vaccine at ages 2, 4, and 6 months: full doses (10 μg of PRP antigen), one-half doses (5.0 μg), and one-third doses (3.3 μg) (J. Fernandez et al., Am. J. Trop. Med. Hyg. 62:485–490, 2000). Sixty serum samples, collected at age 7 months, with ≥2.0 μg of anti-PRP IgG per ml were randomly selected for avidity determinations. Geometric mean IgG concentrations were 13, 14, and 17 μg/ml for infants who received the full-dose (n = 19), one-half-dose (n = 19), and one-third-dose (n = 22) regimens, respectively. SBA geometric mean titers (1/dilution) were 85.0, 82.0, and 76.1 in sera from infants receiving the full-, one-half-, and one-third-dose regimens, respectively. Avidity indices (mean ± standard error weighted average of NaSCN molar concentration × serum dilution factor) were 71.9 ± 9.4, 123.6 ± 26.8, and 150.9 ± 24.9 for the full-, one-half-, and one-third-dose regimens, respectively. Upon comparison, the only significant difference (P = 0.024) found was a greater avidity index for sera from infants receiving the one-third-dose regimen than for sera from infants receiving the the full-dose regimen. We conclude that fractional doses elicit similar functional antibody activities in infants with ≥2 μg of anti-PRP IgG per ml, corresponding to 89, 90, and 97% of infants receiving three doses of either the full concentration or one-half or one-third of the labeled concentration, respectively. This approach offers an alternative strategy for the prevention of H. influenzae type b disease in countries with limited resources.     

Evaluation of the Safety and Immunogenicity of Two Antigen Concentrations of the Mtb72F/AS02A Candidate Tuberculosis Vaccine in Purified Protein Derivative-Negative Adults

Tuberculosis (TB) remains a major cause of illness and death worldwide, making a new TB vaccine an urgent public health priority. Purified protein derivative (PPD)-negative adults (n = 50) were equally randomized to receive 3 doses at 1-month intervals (at 0, 1, and 2 months) of one of the following vaccines: Mtb72F/AS02_A (10 or 40 μg antigen), Mtb72F/saline (10 or 40 μg antigen), or AS02_A. Mtb72F/AS02_A recipients received an additional dose 1 year after the first dose to evaluate if the elicited immune response could be boosted. Mtb72F/AS02_A vaccines were locally reactogenic but clinically well tolerated, with transient adverse events (usually lasting between 1 and 4 days) that resolved without sequelae being observed. No vaccine-related serious adverse events were reported. Vaccination with Mtb72F/AS02_A induced a strong Mtb72F-specific humoral response and a robust Mtb72F-specific CD4⁺ T-cell response, both of which persisted at 9 months after primary immunization and for 1 year after the booster immunization. There was no significant difference between the magnitude of the CD4⁺ T-cell response induced by the 10-μg and 40-μg Mtb72F/AS02_A vaccines. The Mtb72F-specific CD4⁺ T cells predominantly expressed CD40L; CD40L and interleukin-2 (IL-2); CD40L and tumor necrosis factor alpha (TNF-α); CD40L, IL-2, and TNF-α; and CD40L, IL-2, TNF-α, and gamma interferon (IFN-γ). Serum IFN-γ, but not TNF-α, was detected 1 day after doses 2 and 3 for the Mtb72F/AS02_A vaccine but did not persist. Vaccine-induced CD8⁺ T-cell responses were not detected, and no immune responses were elicited with AS02_A alone. In conclusion, Mtb72F/AS02_A is clinically well tolerated and is highly immunogenic in TB-naïve adults. The 10- and 40-μg Mtb72F/AS02_A vaccines show comparable safety and immunogenicity profiles.Tuberculosis (TB) is a major cause of illness and death worldwide, causing approximately 1.7 million deaths a year (43). Despite global efforts to control or eradicate the disease, the WHO estimates that in 2008 an estimated 8.9 million to 9.9 million people became infected with Mycobacterium tuberculosis. The situation is compounded by the emergence of multidrug-resistant TB. Since one-third of the world''s population is estimated to be latently infected with M. tuberculosis and at possible risk of disease, TB prevention remains one of today''s greatest public health challenges. An efficacious vaccination strategy is an essential tool to control TB.M. bovis bacillus Calmette-Guérin (BCG), consisting of attenuated strains of M. bovis, is the only TB vaccine currently available. It effectively prevents meningeal and miliary TB in young children (8) but appears to be ineffective in preventing adult-onset TB (protection rates, 0 to 80%) (10) and pulmonary TB in children.GlaxoSmithKline (GSK) Biologicals'' candidate TB vaccine antigen, Mtb72F, is composed of a fusion protein derived from two highly immunogenic M. tuberculosis antigens: Mtb39A (Rv0125 encoding PepA) and Mtb32A (Rv1196 encoding PPE18) (34, 35). Mtb72F, formulated with GSK Biologicals'' proprietary AS02_A adjuvant system, was shown to be well tolerated in animal models and protected against M. tuberculosis challenge in nonhuman primates, where Mtb72F/AS02_A was shown to be capable of inducing long-term protection against tuberculosis, as determined by protection against severe disease and death and by other clinical and histopathological parameters (6, 30, 34, 39). A first-time-in-human study evaluated Mtb72F/AS02_A (10 μg) in purified protein derivative (PPD)-negative TB-naïve, healthy adults in the United States given according to a 0-, 1-, and 2-month schedule and was found to be clinically well tolerated and highly immunogenic (42).This study assessed whether a larger amount of the Mtb72F/AS02_A vaccine antigen (40 μg) could improve the elicited immune response compared with the response elicited by the previously tested 10-μg antigen dose (42). In addition, a fourth vaccine dose was given to the vaccine recipients to evaluate whether the immune response could be boosted approximately 1 year after the primary vaccination course.     

Protective Immunity against Tularemia Provided by an Adenovirus-Vectored Vaccine Expressing Tul4 of Francisella tularensis

Francisella tularensis, a category A bioterrorism agent, is a highly infectious organism that is passed on via skin contact and inhalation routes. A live attenuated vaccine strain (LVS) has been developed, but it has not been licensed for public use by the FDA due to safety concerns. Thus, there exists a need for a safer and improved vaccine. In this study, we have constructed a replication-incompetent adenovirus, Ad/opt-Tul4, carrying a codon-optimized gene for expression of a membrane protein, Tul4, of F. tularensis LVS. Its ability to protect against lethal challenge and its immunogenicity were evaluated in a murine model. An intramuscular injection of a single dose (1 × 10⁷ PFU) of Ad/opt-Tul4 elicited a robust Tul4-specific antibody response. Assays suggest a Th1-driven response. A single dose elicited 20% protection against challenge with 100 × 50% lethal dose (LD₅₀) F. tularensis LVS; two additional booster shots resulted in 60% protection. In comparison, three doses of 5 μg recombinant Tul4 protein did not elicit significant protection against challenge. Therefore, the Ad/opt-Tul4 vaccine was more effective than the protein vaccine, and protection was dose dependent. Compared to LVS, the protection rate is lower, but an adenovirus-vectored vaccine may be more attractive due to its enhanced safety profile and mucosal route of delivery. Furthermore, simple genetic modification of the vaccine may potentially produce antibodies protective against a fully virulent strain of F. tularensis. Our data support the development and further research of an adenovirus-vectored vaccine against Tul4 of F. tularensis LVS.     

Assessment of Antigen-Specific and Cross-Reactive Antibody Responses to an MF59-Adjuvanted A/H5N1 Prepandemic Influenza Vaccine in Adult and Elderly Subjects

Preparedness against an A/H5N1 influenza pandemic requires well-tolerated, effective vaccines which provide both vaccine strain-specific and heterologous, cross-clade protection. This study was conducted to assess the immunogenicity and safety profile of an MF59-adjuvanted, prepandemic influenza vaccine containing A/turkey/Turkey/01/2005 (H5N1) strain viral antigen. A total of 343 participants, 194 adults (18 to 60 years) and 149 elderly individuals (≥61 years), received two doses of the investigational vaccine given 3 weeks apart. Homologous and heterologous antibody responses were analyzed by hemagglutination inhibition (HI), single radial hemolysis (SRH), and microneutralization (MN) assays 3 weeks after administration of the first vaccine dose and 3 weeks and 6 months after the second dose. Immunogenicity was assessed according to European licensure criteria for pandemic influenza vaccines. After two vaccine doses, all three European licensure criteria were met for adult and elderly subjects against the homologous vaccine strain, A/turkey/Turkey/1/2005, when analyzed by HI and SRH assays. Cross-reactive antibody responses were observed by HI and SRH analyses against the heterologous H5N1 strains, A/Indonesia/5/2005 and A/Vietnam/1194/2004, in adult and elderly subjects. Solicited local and systemic reactions were mostly mild to moderate in severity and occurred less frequently in the elderly than in adult vaccinees. In both adult and elderly subjects, MF59-adjuvanted vaccine containing 7.5 μg of A/Turkey strain influenza virus antigen was highly immunogenic, well tolerated, and able to elicit cross-clade, heterologous antibody responses against A/Indonesia and A/Vietnam strains 6 weeks after the first vaccination.     

Low-dose priming before vaccination with the phase I chloroform-methanol residue vaccine against Q fever enhances humoral and cellular immune responses to Coxiella burnetii

Although the phase I Coxiella burnetii cellular vaccine is completely efficacious in humans, adverse local and systemic reactions may develop if immune individuals are inadvertently vaccinated. The phase I chloroform-methanol residue (CMRI) vaccine was developed as a potentially safer alternative. Human volunteers with no evidence of previous exposure to C. burnetii received a subcutaneous vaccination with the CMRI vaccine in phase I studies under protocol IND 3516 to evaluate the safety and immunogenicity of the vaccine. This clinical trial tested escalating doses of the CMRI vaccine, ranging from 0.3 to 60 μg, followed by a booster dose of 30 μg, in a placebo-controlled study. Although priming doses of the CMRI vaccine did not induce a specific antibody detectable by enzyme-linked immunosorbent assay, booster vaccination stimulated the production of significant levels of anti-C. burnetii antibody. Peripheral blood cells (PBCs) of vaccinees responded to C. burnetii cellular antigen in vitro in a vaccine dose-dependent manner. After the booster dose, PBCs were activated by recall antigen in vitro, regardless of the priming dose. These findings suggest that vaccination with the CMRI vaccine can effectively prime the immune system to mount significant anamnestic responses after infection.     

Priming of Immunological Memory by Pneumococcal Conjugate Vaccine in Children Unresponsive to 23-Valent Polysaccharide Pneumococcal Vaccine

Pneumococcal polysaccharide vaccine (PPV) is of limited immunogenicity in infants and immunocompromised patients. Our prospective randomized controlled trial investigated whether priming with pneumococcal conjugate vaccine (PCV) induced specific immunological memory in previously nonresponders to PPV. Of a total of 33 children (2 to 18 years) with polysaccharide-specific immunodeficiency (PSI), group A (n = 16) received two doses of 7-valent PCV in a 4- to 6-week interval, and a booster dose of 23-valent PPV after one year. Group B (n = 17) received two doses of PPV in a 1-year interval exclusively. Specific antibody concentrations for serotypes 4, 5, 6B, 9V, 14, 18C, 19F, and 23F were determined (enzyme-linked immunosorbent assay) before and at 7 and 28 days after administration of the PPV booster and compared to an opsonophagocytosis assay. Of group A, 64 to 100% had antibody concentrations of ≥1 μg/ml on day 28 after the booster versus 25 to 94% of group B. Group A had significantly higher antibody concentrations for all PCV-containing serotypes already on day 7, indicating early memory response. Antibody concentrations were in accordance with functional opsonic activity, although opsonic titers varied among individuals. Pneumococcal vaccination was well tolerated. The incidence of airway infections was reduced after priming with PCV (10/year for group A versus 15/year for group B). Following a PPV booster, even patients primarily not responding to PPV showed a rapid and more pronounced memory response after priming with PCV.     

Comparison of the Long-Term Immunogenicity of Two Pandemic Influenza A/H1N1 2009 Vaccines,the MF59-Adjuvanted and Unadjuvanted Vaccines,in Adults

Since the first reports of the A/H1N1 virus in April 2009, the pandemic influenza virus spread globally and circulated for a long time. The primary method for the control of influenza is vaccination, but levels of influenza vaccine-induced antibody are known to decline rapidly during a 6-month period. In adults aged 18 to 64 years, we compared the long-term immunogenicity of two of the influenza A/H1N1 2009 monovalent vaccines, 3.75-μg MF59-adjuvanted vaccine and 15-μg unadjuvanted vaccine. The serum hemagglutinin inhibition (HI) titers were determined prevaccination and at 1, 6, and 10 months after vaccination. One hundred six (88.3%) of the 120 subjects were monitored for the entire 10-month period after receiving the influenza A/H1N1 2009 monovalent vaccine. There were 60 patients who received the unadjuvanted vaccine and 46 patients who received the MF59-adjuvanted vaccine. The seroprotection rates, seroconversion rates, and the geometric mean titer (GMT) folds fulfilled the criteria of the European Medicines Agency (EMA) for influenza A/California/7/2009 (H1N1) at 1 month after vaccination irrespective of the vaccine composition. Although the GMTs at 1 month postvaccination were somewhat higher in the unadjuvanted vaccine recipients than in the MF59-adjuvanted vaccine recipients, the difference was not significant (P = 0.29). The seroprotection rates at 6 and 10 months postvaccination were preserved above 70% but only in the MF59-adjuvanted vaccine recipients. In conclusion, low-dose MF59-adjuvanted influenza vaccine, even with 3.75 μg hemagglutinin antigen, might induce excellent long-term immunity that is comparable to the conventional dose of unadjuvanted vaccine among healthy adults aged 18 to 64 years.     

Effect of rTsP53 on the M1/M2 activation of bone-marrow derived macrophage in vitro

We investigated that if rTsP53 could be used to activate bone-marrow derived macrophage (BMDM) into M2 macrophage and stop M1 macrophage activation. After 72 h incubation in blank culture medium, cells with PE-CCR7 (-) and FITC-CD206 (-) was extracted and its mean proportion was 92.30 ± 0.22%. With the stimulation of 20 μg/ml IFN-γ for 72 h, cells with PE-CCR7 (+) was extracted and its mean proportion was 16.24 ± 0.82%. With the stimulation of IL-3/IL-14 (both 10 μg/ml) for 72 h, cells with FICT-CD206 (+) was extracted and its mean proportion was 87.32 ± 4.29%. Co-incubation with different dose of rTsP53 (0.001 μg/ml, 0.01 μg/ml, 0.1 μg/ml, 1 μg/ml, 2 μg/ml, 5 μg/ml, 10 μg/ml, respectively) for 72 h, FITC-CD206 (+) macrophage was extracted. The mean proportion in each group was 1.09 ± 0.22%, 2.13 ± 0.13%, 4.91 ± 0.07%, 5.48 ± 0.29%, 9.81 ± 0.06%, 12.83 ± 0.55%, 17.87 ± 0.02%, respectively. The dose of rTsP53 was significantly positive correlated to the proportion of FITC-CD206 (+) macrophage. Co-incubation with 20 μg/ml IFN-γ and 5 μg/ml rTsP53 for 72 h, cells with PE-CCR7 (+) was extracted and its mean proportion was 10.60 ± 0.19%. Compared to that of mere co-incubation with IFN-γ, there was significant difference between the two groups. ELISA showed that Th1 cytokines’ (IFN-γ, IL-6 and TNF-α) level decreased in the culture medium supernatant of BMDM co-incubated with rTsP53. There was negative correlation between the Th1 cytokines’ level and the dose of rTsP53. Both Th2 cytokines (IL-4 and IL-13) and regulatory cytokines in the culture medium increased. There was positive correlation between the Th2 cytokines’ level and the dose of rTsP53. There was also positive correlation between the regulatory cytokines’ level and the dose of rTsP53. Compared to that of BMDM co-incubated with IFN-γ, levels of TNF-α and IL-6 were significant lower than that of BMDM co-incubated with both IFN-γ and rTsP53 (both P < 0.05), while the levels of IL-4 and TGF-β were significant higher (both P < 0.05). There was no significant difference in the levels of IL-13 and IL-10 between the two groups.     

Immunogenicity of Mycoplasma pneumoniae

The immunogenicity of Mycoplasma pneumoniae for New Zealand white female rabbits was studied by using an immunization scheme which employed initial intramuscular immunization with vaccine in incomplete Freund adjuvant followed 3 weeks later by a series of five intravenous injections of fluid vaccine. Small doses of immunogen (15 to 150 μg of mycoplasmic protein per rabbit) gave rise to sera which contained antilipid complement-fixing antibody, produced one to three precipitin lines, but gave poor growth-inhibition on agar. Larger doses of immunogen (1.5 to 15 mg per rabbit) gave rise to sera which gave higher antilipid complement-fixing titers, four to eight precipitin lines, and good growth-inhibition. Doses smaller than 15 μg per rabbit failed to give rise to detectable antibody. Growth-inhibiting antibody was produced later than the other antibodies. The number of precipitin lines was controlled more critically by the quality of the antisera, as determined by the amount of immunogen, than by the quantity of serological test antigen. All sera which gave any precipitin lines produced a common precipitin line which stained for lipid.     

Determinants of Hepatitis A Vaccine Immunity in a Cohort of Human Immunodeficiency Virus-Infected Children Living in Switzerland

Vaccination in HIV-infected children is often less effective than in healthy children. The goal of this study was to assess vaccine responses to hepatitis A virus (HAV) in HIV-infected children. Children of the Swiss Mother and Child HIV Cohort Study (MoCHiV) were enrolled prospectively. Recommendations for initial, catch-up, and additional HAV immunizations were based upon baseline antibody concentrations and vaccine history. HAV IgG was assessed by enzyme-linked immunosorbent assay (ELISA) with a protective cutoff value defined as ≥10 mIU/ml. Eighty-seven patients were included (median age, 11 years; range, 3.4 to 21.2 years). Forty-two patients were seropositive (48.3%) for HAV. Among 45 (51.7%) seronegative patients, 36 had not received any HAV vaccine dose and were considered naïve. Vaccine responses were assessed after the first dose in 29/35 naïve patients and after the second dose in 33/39 children (25 initially naïve patients, 4 seronegative patients, and 4 seropositive patients that had already received 1 dose of vaccine). Seroconversion was 86% after 1 dose and 97% after 2 doses, with a geometric mean concentration of 962 mIU/ml after the second dose. A baseline CD4⁺ T cell count below 750 cells/μl significantly reduced the post-2nd-dose response (P = 0.005). Despite a high rate of seroconversion, patients with CD4⁺ T cell counts of <750/μl had lower anti-HAV antibody concentrations. This may translate into a shorter protection time. Hence, monitoring humoral immunity may be necessary to provide supplementary doses as needed.     

Phase I Safety and Immunogenicity Evaluations of an Alphavirus Replicon HIV-1 Subtype C gag Vaccine in Healthy HIV-1-Uninfected Adults

On the basis of positive preclinical data, we evaluated the safety and immunogenicity of an alphavirus replicon HIV-1 subtype C gag vaccine (AVX101), expressing a nonmyristoylated form of Gag, in two double-blind, randomized, placebo-controlled clinical trials in healthy HIV-1-uninfected adults. Escalating doses of AVX101 or placebo were administered subcutaneously to participants in the United States and Southern Africa. Because of vaccine stability issues, the first trial was halted prior to completion of all dose levels and a second trial was implemented. The second trial was also stopped prematurely due to documentation issues with the contract manufacturer. Safety and immunogenicity were evaluated through assessments of reactogenicity, reports of adverse events, and assessment of replication-competent and Venezuelan equine encephalitis (VEE) viremia. Immunogenicity was measured using the following assays: enzyme-linked immunosorbent assay (ELISA), chromium 51 (⁵¹Cr)-release cytotoxic T lymphocyte (CTL), gamma interferon (IFN-γ) ELISpot, intracellular cytokine staining (ICS), and lymphoproliferation assay (LPA). Anti-vector antibodies were also measured. AVX101 was well tolerated and exhibited only modest local reactogenicity. There were 5 serious adverse events reported during the trials; none were considered related to the study vaccine. In contrast to the preclinical data, immune responses in humans were limited. Only low levels of binding antibodies and T-cell responses were seen at the highest doses. This trial also highlighted the difficulties in developing a novel vector for HIV.     

Evaluation of the Safety,Tolerability, and Immunogenicity of an Oral,Inactivated Whole-Cell Shigella flexneri 2a Vaccine in Healthy Adult Subjects

Shigella causes high morbidity and mortality worldwide, but there is no licensed vaccine for shigellosis yet. We evaluated the safety and immunogenicity of a formalin-inactivated whole-cell Shigella flexneri 2a vaccine, Sf2aWC, given orally to adult volunteers. In a double-blind, placebo-controlled trial, 82 subjects were randomized to receive three doses of vaccine in dose escalation (2.6 ± 0.8 × 10⁸, × 10⁹, × 10¹⁰, and × 10¹¹ vaccine particles/ml). Vaccine safety was actively monitored, and antigen-specific systemic and mucosal immune responses were determined in serum, antibody in lymphocyte supernatant (ALS), and fecal samples. Cytokines were measured in the serum. Sf2aWC was well tolerated and generally safe at all four dose levels. The vaccine resulted in a dose-dependent immune response. At the highest dose, the vaccine induced robust responses to lipopolysaccharide (LPS) in both serum and ALS samples. The highest magnitude and frequency of responses occurred after the first dose in almost all samples but was delayed for IgG in serum. Fifty percent of the vaccinees had a >4-fold increase in anti-LPS fecal antibody titers. Responses to invasion plasmid antigens (Ipa) were low. The levels of interleukin-17 (IL-17), IL-2, gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and IL-10 were increased, and IL-8 was decreased immediately after first dose, but these changes were very transient. This phase I trial demonstrated that the Sf2aWC vaccine, a relatively simple vaccine concept, was safe and immunogenic. The vaccine elicited immune responses which were comparable to those induced by a live, attenuated Shigella vaccine that was protective in prior human challenge studies.