Cold-adapted Influenza Vaccine Research Articles

Cold-adapted influenza vaccine carrying three repeats of a respiratory syncytial virus (RSV) fusion glycoprotein epitope site protects BALB/c mice and cotton rats against RSV infection

Respiratory syncytial virus is the major cause of respiratory viral infections, particularly in infants, immunocompromised populations, and the elderly (over 65 years old), the prevention of RSV infection has become a priority. In this study, we generated a chimeric influenza virus, termed LAIV/RSV/HA-3F, using reverse genetics technology which contained three repeats of the RSV fusion protein neutralizing epitope site II to the N terminal in the background of the hemagglutinin (HA) gene of cold adapted influenza vaccine A/California/7/2009 ca. LAIV/RSV/HA-3F exhibited cold-adapted (ca) and attenuated (att) phenotype. BALB/c mice immunized intranasally with LAIV/RSV/HA-3F showed robust immunogenicity, inducing viral-specific antibody responses against both influenza and RSV, eliciting RSV-specific humoral, cellular and mucosal immune responses. LAIV/RSV/HA-3F also conferred protection as indicated by reduced viral titers and improved lung histopathological alterations against live RSV virus challenge. Mechanismly, single-cell RNA sequencing (scRNA-seq) and single-cell T cell antigen receptor (TCR) sequencing were employed to characterize the immune responses triggered by chimeric RSV vaccine, displaying that LAIV/RSV/HA-3F provided protection mainly via interferon-γ (IFN-γ). Moreover, we found that LAIV/RSV/HA-3F significantly inhibited viral replication in the challenged lung and protected against subsequent RSV challenge in cotton rats without causing lung disease. Taken together, our findings demonstrated that LAIV/RSV/HA-3F has potential as a promising bivalent vaccine with dual purpose candidate for the prevention of influenza and RSV, and preclinical and clinical studies warrant further investigations.

Safety, Immunogenicity, and Protective Efficacy of an H5N1 Chimeric Cold-Adapted Attenuated Virus Vaccine in a Mouse Model

H5N1 influenza virus is a threat to public health worldwide. The virus can cause severe morbidity and mortality in humans. We constructed an H5N1 influenza candidate virus vaccine from the A/chicken/Guizhou/1153/2016 strain that was recommended by the World Health Organization. In this study, we designed an H5N1 chimeric influenza A/B vaccine based on a cold-adapted (ca) influenza B virus B/Vienna/1/99 backbone. We modified the ectodomain of H5N1 hemagglutinin (HA) protein, while retaining the packaging signals of influenza B virus, and then rescued a chimeric cold-adapted H5N1 candidate influenza vaccine through a reverse genetic system. The chimeric H5N1 vaccine replicated well in eggs and the Madin-Darby Canine Kidney cells. It maintained a temperature-sensitive and cold-adapted phenotype. The H5N1 vaccine was attenuated in mice. Hemagglutination inhibition (HAI) antibodies, micro-neutralizing (MN) antibodies, and IgG antibodies were induced in immunized mice, and the mucosal IgA antibody responses were detected in their lung lavage fluids. The IFN-γ-secretion and IL-4-secretion by the mouse splenocytes were induced after stimulation with the specific H5N1 HA protein. The chimeric H5N1 candidate vaccine protected mice against lethal challenge with a wild-type highly pathogenic avian H5N1 influenza virus. The chimeric H5 candidate vaccine is thus a potentially safe, attenuated, and reassortment-incompetent vaccine with circulating A viruses.

Live Attenuated Cold-Adapted Influenza Vaccines.

Live attenuated, cold-adapted influenza vaccines exhibit several desirable characteristics, including the induction of systemic, mucosal, and cell-mediated immunity resulting in breadth of protection, ease of administration, and yield. Seasonal live attenuated influenza vaccines (LAIVs) were developed in the United States and Russia and have been used in several countries. In the last decade, following the incorporation of the 2009 pandemic H1N1 strain, the performance of both LAIVs has been variable and the U.S.-backbone LAIV was less effective than the corresponding inactivated influenza vaccines. The cause appears to be reduced replicative fitness of some H1N1pdm09 viruses, indicating a need for careful selection of strains included in multivalent LAIV formulations. Assays are now being implemented to select optimal strains. An improved understanding of the determinants of replicative fitness of vaccine strains and of vaccine effectiveness of LAIVs is needed for public health systems to take full advantage of these valuable vaccines.

Early protection against influenza by pandemic live attenuated influenza vaccines

Live attenuated cold-adapted (ca) influenza vaccine (LAIV) is an effective tool for the control of influenza, most likely due to their ability to induce both humoral and cellular immune responses, easy application and relatively low manufacturing costs. Attenuated cold-adapted vaccine strains that have achieved a satisfactory balance between restricted replication and high immunogenicity are desirable. The immunogenicity of live attenuated vaccines may depend upon the interplay between its ability to induce pro-inflammatory cytokine responses and the relative sensitivity of the attenuated vaccine strain to an antiviral effect of these cytokines. To better understand the relationship between attenuation and induction of innate immunity as well as contribution of the early cytokine response to the relative immunogenicity of LAIVs, we have studied early protection induced by LAIV in vivo as well as early cytokine response in human cells macrophage origin in response to infection with vaccine strains or epidemic virus.
 The aim of this study was to investigate the early immune response and protective activity in female CBA mice intranasally immunized with cold-adapted influenza vaccine strains of different genome compositions of 5:3 or 6:2. For experimental infection pandemic influenza viruses A/South Africa/3626/13 (H1N1)pdm09 and A/New York/61/15 (H1N1)pdm09 were used to be administered to animals at a dose of 106 EID50 at day 3 after immunization (challenge infection). Although challenge viruses replicate at mice lungs at various, extend, on day 10 after immunization mice were protected from death from 60 up to 80%. Reassortants LAIV did not differ statistically on these levels.
 Study of the expression of IFN- and IFN- genes in human lung macrophage line cells THP-1 in vitro have shown that macrophages stimulated with vaccine strains with the genome formula 6:2 and 5:3, had a sufficient level of expression of these genes, comparable to that, as in infection with wild virus type A/South Africa/3626/13 (H1N1)pdm09. These data may indicate that surface proteins of influenza A virus are involved in the process of stimulation of the IFN- and IFN- genes.

The safety of attenuated and recombinant nasal influenza vaccines in terms of the development of secondary bacterial superinfection

Introduction. Influenza is a severe viral disease. The most common post-influenza complication is pneumonia. Earlier, we developed an experimental mouse model of viralbacterial pneumonia induced by successive infection with influenza virus and St. aureus, in which lethal synergy between pathogens observed in epidemiological observations was detected.Aim. To study the effect of the administration of intranasal vaccines, followed by infection with St. pneumoniae on the development and completion of the disease.Materials and methods. The animals were immunized intranasal with a strain of attenuated cold-adapted live influenza vaccine A/17/California/2009/38 (H1N1)pdm09 (LAIV) and a recombinant vaccine based on virus-like particles HA(Puerto Rico/8/34)- Gag (VLPs). Control groups of animals were infected with virulent strains of influenza virus A/ California/04/2009 (H1N1)pdm09 or A/Puerto Rico /8/34 (H1N1). On the fifth day after intranasal immunization with the vaccine preparations and infection with pathogenic strains, animals were subjected to bacterial infection with a strain of St. pneumoniae. The presence of synergism of vaccine or viral agent with bacterial infection was assessed by survival and weight loss of animals, virus titer and density of bacteria in nasopharyngeal washes and lungs.Results. It was shown that immunization with vaccine preparations did not lead to increased sensitivity of mice to bacterial infection. Elimination of bacteria from the lungs and nasopharynx in groups immunized with vaccine preparations corresponded to the dynamics in the group of animals immunized by PBS.Discussion. The results obtained indicate the safety of intranasal immunization with LAIV A/17/California/2009/38 (H1N1)pdm09 and virus-like particles HA (Puerto Rico/8/34)- Gag (VLPs) in terms of enhancing secondary bacterial superinfection caused by St. pneumoniae.Conclusion. The studied vaccines successfully blocked infections in the lower respiratory tract.

Anti-caries vaccine based on clinical cold-adapted influenza vaccine: A promising alternative for scientific and public-health protection against dental caries

Dental caries remains one of the most pervasive infectious disease around the world. Protection against dental caries can be achieved experimentally by eliciting salivary IgA targeting surficial antigens of S. mutans, however, no such a vaccine has been launched for human use yet. Live vectored vaccines hold the greatest feasibility to induce potent and long-lasting immunity in the host. The FDA approved intranasal cold-adapted influenza vaccine has been used in clinical settings for many years. The vaccine can not only induce broad adaptive immune responses especially mucosal immunity, but the member strains can also circumvent existing immunity, presenting promising candidates for live vectored anti-caries vaccine. Moreover, the genetic techniques for modification of cold-adapted influenza viruses are well developed and widely applicable. Thus, we hypothesize that effective anti-caries vaccine can be developed with the backbone of cold-adapted influenza viruses by inserting specific antigenic identifier sequences of S. mutans into the viral genome, which is anticipated to protect against dental caries in humans with easy inoculation. The immune efficacies of recombinant cold-adapted influenza viruses expressing exogenous antigens have been verified by in vivo experiments for multiple infectious diseases, giving us great confidence to validate the safety properties and protection effect with this chimeric vaccine in animals or even humans. Existing data suggests that the live anti-caries vaccine may help improve public oral health by controlling the caries disease itself.

Pan-Influenza A Protection by Prime-Boost Vaccination with Cold-Adapted Live-Attenuated Influenza Vaccine in a Mouse Model.

Influenza virus infections continually pose a major public health threat with seasonal epidemics and sporadic pandemics worldwide. While currently licensed influenza vaccines provide only strain-specific protection, antigenic drift and shift occasionally render the viruses resistant to the host immune responses, which highlight the need for a vaccine that provides broad protection against multiple subtypes. In this study, we suggest a vaccination strategy using cold-adapted, live attenuated influenza vaccines (CAIVs) to provide a broad, potent, and safe cross-protection covering antigenically distinct hemagglutinin (HA) groups 1 and 2 influenza viruses. Using a mouse model, we tested different prime–boost combinations of CAIVs for their ability to induce humoral and T-cell responses, and protective efficacy against H1 and H5 (HA group 1) as well as H3 and H7 (HA group 2) influenza viruses. Notably, even in the absence of antibody-mediated neutralizing activity or HA inhibitory activity in vitro, CAIVs provided a potent protection against heterologous and heterosubtypic lethal challenges in vivo. Heterologous combination of prime (H1)–boost (H5) vaccine strains showed the most potent cross-protection efficacy. In vivo depletion experiments demonstrated not only that T cells and natural killer cells contributed to the cross-protection, but also the involvement of antibody-dependent mechanisms for the cross-protection. Vaccination-induced antibodies did not enhance the infectivity of heterologous viruses, and prime vaccination did not interfere with neutralizing antibody generation by the boost vaccination, allaying vaccine safety concerns associated with heterogeneity between the vaccines and challenge strains. Our data show that CAIV-based strategy can serve as a simple but powerful option for developing a “truly” universal influenza vaccine providing pan-influenza A protection, which has not been achieved yet by other vaccine strategies. The promising results of potency, breadth, and safety demonstrated in the mouse model support further studies in higher animal models for clinical relevance.

Generation and protective efficacy of a cold-adapted attenuated avian H9N2 influenza vaccine.

To prevent H9N2 avian influenza virus infection in chickens, a long-term vaccination program using inactivated vaccines has been implemented in China. However, the protective efficacy of inactivated vaccines against antigenic drift variants is limited, and H9N2 influenza virus continues to circulate in vaccinated chicken flocks in China. Therefore, developing a cross-reactive vaccine to control the impact of H9N2 influenza in the poultry industry remains a high priority. In the present study, we developed a live cold-adapted H9N2 influenza vaccine candidate (SD/01/10-ca) by serial passages in embryonated eggs at successively lower temperatures. A total of 13 amino acid mutations occurred during the cold-adaptation of this H9N2 virus. The candidate was safe in chickens and induced robust hemagglutination-inhibition antibody responses and influenza virus–specific CD4+ and CD8+ T cell immune responses in chickens immunized intranasally. Importantly, the candidate could confer protection of chickens from homologous and heterogenous H9N2 viruses. These results demonstrated that the cold-adapted attenuated H9N2 virus would be selected as a vaccine to control the infection of prevalent H9N2 influenza viruses in chickens.

African green monkeys recapitulate the clinical experience with replication of live attenuated pandemic influenza virus vaccine candidates.

Live attenuated cold-adapted (ca) H5N1, H7N3, H6N1, and H9N2 influenza vaccine viruses replicated in the respiratory tract of mice and ferrets, and 2 doses of vaccines were immunogenic and protected these animals from challenge infection with homologous and heterologous wild-type (wt) viruses of the corresponding subtypes. However, when these vaccine candidates were evaluated in phase I clinical trials, there were inconsistencies between the observations in animal models and in humans. The vaccine viruses did not replicate well and immune responses were variable in humans, even though the study subjects were seronegative with respect to the vaccine viruses before vaccination. Therefore, we sought a model that would better reflect the findings in humans and evaluated African green monkeys (AGMs) as a nonhuman primate model. The distribution of sialic acid (SA) receptors in the respiratory tract of AGMs was similar to that in humans. We evaluated the replication of wt and ca viruses of avian influenza (AI) virus subtypes H5N1, H6N1, H7N3, and H9N2 in the respiratory tract of AGMs. All of the wt viruses replicated efficiently, while replication of the ca vaccine viruses was restricted to the upper respiratory tract. Interestingly, the patterns and sites of virus replication differed among the different subtypes. We also evaluated the immunogenicity and protective efficacy of H5N1, H6N1, H7N3, and H9N2 ca vaccines. Protection from wt virus challenge correlated well with the level of serum neutralizing antibodies. Immune responses were slightly better when vaccine was delivered by both intranasal and intratracheal delivery than when it was delivered intranasally by sprayer. We conclude that live attenuated pandemic influenza virus vaccines replicate similarly in AGMs and human subjects and that AGMs may be a useful model to evaluate the replication of ca vaccine candidates. Importance: Ferrets and mice are commonly used for preclinical evaluation of influenza vaccines. However, we observed significant inconsistencies between observations in humans and in these animal models. We used African green monkeys (AGMs) as a nonhuman primate (NHP) model for a comprehensive and comparative evaluation of pairs of wild-type and pandemic live attenuated influenza virus vaccines (pLAIV) representing four subtypes of avian influenza viruses and found that pLAIVs replicate similarly in AGMs and humans and that AGMs can be useful for evaluation of the protective efficacy of pLAIV.

Evaluation of Three Live Attenuated H2 Pandemic Influenza Vaccine Candidates in Mice and Ferrets

H2 influenza viruses have not circulated in humans since 1968, and therefore a significant portion of the population would be susceptible to infection should H2 influenza viruses reemerge. H2 influenza viruses continue to circulate in avian reservoirs worldwide, and these reservoirs are a potential source from which these viruses could emerge. Three reassortant cold-adapted (ca) H2 pandemic influenza vaccine candidates with hemagglutinin (HA) and neuraminidase (NA) genes derived from the wild-type A/Japan/305/1957 (H2N2) (Jap/57), A/mallard/6750/1978 (H2N2) (mal/78), or A/swine/MO/4296424/2006 (H2N3) (sw/06) viruses and the internal protein gene segments from the A/Ann Arbor/6/60 ca virus were generated by plasmid-based reverse genetics (Jap/57 ca, mal/78 ca, and sw/06 ca, respectively). The vaccine candidates exhibited the in vitro phenotypes of temperature sensitivity and cold adaptation and were restricted in replication in the respiratory tract of ferrets. In mice and ferrets, the vaccines elicited neutralizing antibodies and conferred protection against homologous wild-type virus challenge. Of the three candidates, the sw/06 ca vaccine elicited cross-reactive antibodies and provided significant protection against the greatest number of heterologous viruses. These observations suggest that the sw/06 ca vaccine should be further evaluated in a clinical trial as an H2 pandemic influenza vaccine candidate. Influenza pandemics arise when novel influenza viruses are introduced into a population with little prior immunity to the new virus and often result in higher rates of illness and death than annual seasonal influenza epidemics. An influenza H2 subtype virus caused a pandemic in 1957, and H2 viruses circulated in humans till 1968. H2 influenza viruses continue to circulate in birds, and the development of an H2 influenza vaccine candidate is therefore considered a priority in preparing for future pandemics. However, we cannot predict whether a human H2 virus will reemerge or a novel avian H2 virus will emerge. We identified three viruses as suitable candidates for further evaluation as vaccines to protect against H2 influenza viruses and evaluated the immune responses and protection that these three vaccines provided in mice and ferrets.

P114 Modulation of vaccine-induced T cell immunity by specific adjuvants

Introduction Successful vaccination requires generation of long-lasting and protective T cell responses, and thus, therapeutic strategies aimed to enhance vaccine-induced T cell immunity are a source of great interest. Here we have investigated the influence of toll-like receptor (TLR)-3 ligands as well as type I interferon (IFN) agonists on the maintenance of CD8 + T cell memory in the context of mucosal influenza vaccination. Methods Mice and vaccine studies. C57BL/6 J male mice between 8–10 weeks of age were used for our studies. Cold-adapted influenza vaccines were rescued by reverse genetics using A/Puerto Rico/8/34 (H1N1) hemagglutinin (HA) and neuraminidase (NA) segments in a A/Ann Arbor/6/60/ (H2N2) background (6 + 2 reassortant). Recombinant viruses were grown at 33 °C in 9-days old chicken eggs and titrated in Madin-Darby canine kidney cells (MDCKs) as described elsewhere. Nutlin-3 was purchased from Cayman Chemicals, poly I:C was purchased from Invivogen. Combinations of vaccine + adjuvants were administered intranasally in a maximum volume of 50 ml. Tissue samples were harvested from euthanized mice and processed for analysis of viral titers, quantitative RT-PCR, or ELISA. In survival experiments mice were sacrificed if their weight dropped more than 25% of their initial body weight as per institutional guidelines. The animal experiments were performed according to the guidelines of the German animal protection law. All animal protocols were approved by the relevant German authorities. Flow cytometry. Lung samples were enzymatically digested with 2 mg/ml of Collagenase D (Roche). Mediastinal lymph nodes were disrupted mechanically. Tissue samples were processed for flow cytometry and red cells were lysed using BD Red Blood Cell Lysing Buffer. Samples were acquired on a FACS canto II instrument and analyzed with FlowJO software (Treestar). Results Engagement of TLR3 and type I IFN signaling by candidate adjuvants of cold-adapted influenza vaccines in mice, increased vaccine-induced cytokine production early after mucosal administration, including enhanced production of MCP1, IP-10 and G-CSF. This increase in vaccine-induced early inflammatory responses resulted in robust cytotoxic T lymphocyte (CTL) activity, rapid viral clearance, and enhanced survival to influenza challenge. Conversely, vaccine adjuvants did not influence antibody titers in vaccinated individuals, suggesting that the early events that take place during the innate phase of the immune response play a chief role on the establishment and modulation of adaptive immunity. Conclusion Our results indicated that specific adjuvants with the ability to enhance TLR3 and type I IFN signaling enhance cytokine responses associated to vaccine administration, which resulted in improved CD8 + T cell-dependent recall responses. Of note, adjuvant-vaccine regimens reduced the vaccine dose necessary to provide protection to lethal challenge. These findings indicate that modulation of innate immunity via TLR ligands and type I IFN agonists may serve as a therapeutic strategy to enhance T cell memory maintenance after influenza vaccination, and may provide means to reduce the amount of vaccine stock necessary to protect individuals at risk in the face of an influenza pandemic.

Cold-Adapted Influenza and Recombinant Adenovirus Vaccines Induce Cross-Protective Immunity against pH1N1 Challenge in Mice

BackgroundThe rapid spread of the 2009 H1N1 pandemic influenza virus (pH1N1) highlighted problems associated with relying on strain-matched vaccines. A lengthy process of strain identification, manufacture, and testing is required for current strain-matched vaccines and delays vaccine availability. Vaccines inducing immunity to conserved viral proteins could be manufactured and tested in advance and provide cross-protection against novel influenza viruses until strain-matched vaccines became available. Here we test two prototype vaccines for cross-protection against the recent pandemic virus.Methodology/Principal FindingsBALB/c and C57BL/6 mice were intranasally immunized with a single dose of cold-adapted (ca) influenza viruses from 1977 or recombinant adenoviruses (rAd) expressing 1934 nucleoprotein (NP) and consensus matrix 2 (M2) (NP+M2-rAd). Antibodies against the M2 ectodomain (M2e) were seen in NP+M2-rAd immunized BALB/c but not C57BL/6 mice, and cross-reacted with pH1N1 M2e. The ca-immunized mice did not develop antibodies against M2e. Despite sequence differences between vaccine and challenge virus NP and M2e epitopes, extensive cross-reactivity of lung T cells with pH1N1 peptides was detected following immunization. Both ca and NP+M2-rAd immunization protected BALB/c and C57BL/6 mice against challenge with a mouse-adapted pH1N1 virus.Conclusion/SignificanceCross-protective vaccines such as NP+M2-rAd and ca virus are effective against pH1N1 challenge within 3 weeks of immunization. Protection was not dependent on recognition of the highly variable external viral proteins and could be achieved with a single vaccine dose. The rAd vaccine was superior to the ca vaccine by certain measures, justifying continued investigation of this experimental vaccine even though ca vaccine is already available. This study highlights the potential for cross-protective vaccines as a public health option early in an influenza pandemic.

Disruption of the Viral Polymerase Complex Assembly as a Novel Approach to Attenuate Influenza A Virus

To develop a novel attenuation strategy applicable to all influenza A viruses, we targeted the highly conserved protein-protein interaction of the viral polymerase subunits PA and PB1. We postulated that impaired binding between PA and PB1 would negatively affect trimeric polymerase complex formation, leading to reduced viral replication efficiency in vivo. As proof of concept, we introduced single or multiple amino acid substitutions into the protein-protein-binding domains of either PB1 or PA, or both, to decrease binding affinity and polymerase activity substantially. As expected, upon generation of recombinant influenza A viruses (SC35M strain) containing these mutations, many pseudo-revertants appeared that partially restored PA-PB1 binding and polymerase activity. These polymerase assembly mutants displayed drastic attenuation in cell culture and mice. The attenuation of the polymerase assembly mutants was maintained in IFNα/β receptor knock-out mice. As exemplified using a H5N1 polymerase assembly mutant, this attenuation strategy can be also applied to other highly pathogenic influenza A virus strains. Thus, we provide proof of principle that targeted mutation of the highly conserved interaction domains of PA and PB1 represents a novel strategy to attenuate influenza A viruses.

Intranasal DNA Vaccination Induces Potent Mucosal and Systemic Immune Responses and Cross-protective Immunity Against Influenza Viruses

The induction of potent virus-specific immune responses at mucosal surfaces where virus transmission occurs is a major challenge for vaccination strategies. In the case of influenza vaccination, this has been achieved only by intranasal delivery of live-attenuated vaccines that otherwise pose safety problems. Here, we demonstrate that potent mucosal and systemic immune responses, both cellular and humoral, are induced by intranasal immunization using formulated DNA. We show that formulation with the DNA carrier polyethylenimine (PEI) improved by a 1,000-fold the efficiency of gene transfer in the respiratory track following intranasal administration of luciferase-coding DNA. Using PEI formulation, intranasal vaccination with DNA-encoding hemagglutinin (HA) from influenza A H5N1 or (H1N1)2009 viruses induced high levels of HA-specific immunoglobulin A (IgA) antibodies that were detected in bronchoalveolar lavages (BALs) and the serum. No mucosal responses could be detected after parenteral or intranasal immunization with naked-DNA. Furthermore, intranasal DNA vaccination with HA from a given H5N1 virus elicited full protection against the parental strain and partial cross-protection against a distinct highly pathogenic H5N1 strain that could be improved by adding neuraminidase (NA) DNA plasmids. Our observations warrant further investigation of intranasal DNA as an effective vaccination route.

Kinetics of viral shedding and immune responses in adults following administration of cold-adapted influenza vaccine

The optimal type and timing of specimens to study the immune responses to cold-adapted influenza vaccine (CAIV) and shedding of vaccine virus are not well established. Healthy adults were vaccinated with CAIV ( n = 10) or trivalent influenza vaccine (TIV) ( n = 5). Shedding of vaccine strain influenza B was detected by culture in 6 of 10 CAIV recipients; influenza A was also detected in one of these subjects. Viral shedding by quantitative RT-PCR was detected in 9 of 10 subjects. We detected a ≥2-fold increase in influenza-specific IgA in nasal wash in 80–100% of CAIV recipients following vaccination, but specific IgG increased in neither nasal wash nor saliva. Recipients of TIV had significant increases in specific serum IgG antibodies. Recipients of both CAIV and TIV had significant increases in IFNγ-secreting peripheral blood mononuclear cells (PBMCs). PBMCs from subjects receiving CAIV showed a higher proportion of functional, tissue-tropic T-cells (CD4+CD69+CD18+MIP1α+) specific for homotypic and heterosubtypic strains of influenza by flow cytometry.

Immunizations and infectious diseases in pediatric liver transplantation

Liver transplantation (LTx) is an established and effective treatment for children with end-stage and metabolic liver disease. Improved surgical techniques and immunosuppressive regimens have led to enhanced short-term and long-term survival rates, which now approach or exceed 90%. Consequently, more children are being referred for LTx, and an increasing numbers of pediatric centers routinely perform this procedure. Infectious complications are an important cause of morbidity and mortality in children undergoing LTx. However, improvements in immune suppression management along with the availability of new antimicrobial agents and diagnostic tools have resulted in improved treatment and preventative regimens, thus reducing the impact of infectious complications on these children. This review provides an overview of the infectious complications and prevention strategies for children undergoing LTx.

The use of components of plant origin in the development of production technology for live cold-adapted cultural influenza vaccine

The impact of culturing conditions (multiplicity of cell culture infection with influenza virus, composition of growth and maintenance nutrient media) for the efficiency of multiplication of cold-adapted reassortant vaccine strains of influenza A and B viruses was evaluated. Soybean hydrolysate protein-based biological additive to nutrient medium provided effective reproduction of influenza A virus in MDCK cells in the presence of 2 microg/ml trypsin. The use of soybean peptone-based stabilizer provided retention of infectious titer of influenza virus grown in MDCK culture after its lyophilization to a level of 8.5 lg EID50/ml.

Safety and Tolerability of Cold-Adapted Influenza Vaccine, Trivalent, in Infants Younger Than 6 Months of Age

Young children are at high risk for influenza-related complications. Vaccination of close household contacts is recommended to provide indirect protection to children <6 months of age. Studies have shown that live, cold-adapted influenza vaccine, trivalent, is efficacious in children. To assess the risks associated with inadvertent exposure of infants to vaccine viruses from vaccinated contacts, this study was designed to evaluate the safety and tolerability of cold-adapted influenza vaccine, trivalent, administered intranasally to healthy children 6 to <24 weeks of age. Healthy infants aged 6 to <16 weeks and 16 to <24 weeks, respectively, were randomly assigned to receive 2 doses of influenza vaccine, or placebo intranasally 35 +/- 7 days apart. Reactogenicity events were monitored for 11 days after each dose. Other adverse events were monitored through 28 to 35 days after dose 2. Of the infants aged 6 to <16 weeks, 31 received influenza vaccine and 28 received placebo, and of those aged 16 to <24 weeks, 30 received influenza vaccine and 31 received placebo. In the 6- to <16-week cohort, more influenza vaccine, recipients experienced irritability (66.7% vs 35.7%) and runny nose or nasal congestion (63.3% vs 33.3%) after dose 1 but not dose 2. There were no significant increases in any other reactogenicity events or adverse events in the vaccine recipients compared with the placebo group. Although there was an increase in mild reactogenicity events in children 6 to <16 weeks of age, cold-adapted influenza vaccine, trivalent, was generally well tolerated in infants 6 to <24 weeks of age. These findings support further evaluation of cold-adapted influenza vaccine, trivalent, in infants <6 months of age.

Comparison of the Efficacy and Safety of Live Attenuated Cold-Adapted Influenza Vaccine, Trivalent, With Trivalent Inactivated Influenza Virus Vaccine in Children and Adolescents With Asthma

Comparison of the Efficacy and Safety of Live Attenuated Cold-Adapted Influenza Vaccine, Trivalent, With Trivalent Inactivated Influenza Virus Vaccine in Children and Adolescents With Asthma

Comparative Immunogenicities of Frozen and Refrigerated Formulations of Live Attenuated Influenza Vaccine in Healthy Subjects

The frozen version of live attenuated influenza vaccine (LAIV; FluMist) was compared with a newly licensed, refrigerated formulation, the cold-adapted influenza vaccine, trivalent (CAIV-T), for their immunogenicity, safety, and tolerability in healthy subjects 5 to 49 years of age. Eligible subjects were randomized 1:1 to receive CAIV-T or frozen LAIV. Subjects 5 to 8 years of age received two doses of vaccine 46 to 60 days apart; subjects 9 to 49 years of age received one dose of vaccine. Equivalent immunogenicities were defined as serum hemagglutination inhibition (HAI) geometric mean titer (GMT) ratios >0.5 and <2.0 for each of the three vaccine-specific strains. A total of 376 subjects 5 to 8 years of age and 566 subjects 9 to 49 years of age were evaluable. Postvaccination HAI GMT ratios were equivalent for CAIV-T and LAIV. The GMT ratios of CAIV-T/LAIV for the H1N1, H3N2, and B strains were 1.24, 1.02, and 1.00, respectively, for the 5- to 8-year-old age group and 1.14, 1.12, and 0.96, respectively, for the 9- to 49-year-old age group. Seroresponse/seroconversion rates (fourfold or greater rise) were similar in both age groups for each of the three vaccine strains. Within 28 days, the most frequent reactogenicity event in the CAIV-T and LAIV groups was runny nose/nasal congestion, which occurred at higher rates after dose 1 (44% and 42%, respectively) than after dose 2 (41% and 29%, respectively) in the 5- to 8-year-old group. Otherwise, the rates of adverse events (AEs) were similar between the treatment groups and the two age cohorts, with no serious AEs related to the study vaccines. The immunogenicities, reactogenicity events, and AEs were comparable for refrigerated CAIV-T and frozen LAIV.