Live Influenza Virus Vaccine Research Articles

Efficacy trial of live, cold-adapted and inactivated influenza virus vaccines in older adults with chronic obstructive pulmonary disease: a VA cooperative study

We assessed whether trivalent live, cold-adapted influenza virus (CAIV-T) vaccine provides added protection when co-administered with trivalent inactivated influenza virus vaccine (TVV) in patients with chronic obstructive pulmonary disease (COPD). Subjects ( N=2215) were randomly assigned to receive either TVV intramuscularly (IM) and CAIV-T intranasally (TC), or TVV and placebo (TP). The vaccines were well-tolerated. Efficacy of TC compared to TP was not statistically significant and was 0.16 for any influenza virus strain (95% confidence limit (CL): −0.22, 0.43), 0.26 for A (H3N2) virus (95% CL: −0.17, 0.53), and −0.05 for type B virus (95% CL: −1.13, 0.48). However, there was a possible advantage for TC over TP in reducing respiratory consequences of an influenza season measured by pulmonary function and symptoms at end of study.

Plasmid-only rescue of influenza A virus vaccine candidates.

The potential threat of another influenza virus pandemic stimulates discussion on how to prepare for such an event. The most reasonable prophylactic approach appears to be the use of effective vaccines. Since influenza and other negative-stranded RNA viruses are amenable to genetic manipulation using transfection by plasmids, it is possible to outline new reverse genetics-based approaches for vaccination against influenza viruses. We suggest three approaches. First, we use a plasmid-only rescue system that allows the rapid generation of high-yield recombinant vaccine strains. Second, we propose developing second-generation live influenza virus vaccines by constructing an attenuated master strain with deletions in the NS1 protein, which acts as an interferon antagonist. Third, we suggest the use of Newcastle disease virus recombinants expressing influenza virus haemagglutinin proteins of pandemic (epizootic) strains as novel vaccine vectors for use in animals and possibly humans.

A new modified live equine influenza virus vaccine: phenotypic stability, restricted spread and efficacy against heterologous virus challenge.

Flu Avert IN vaccine is a new, live attenuated virus vaccine for equine influenza. We tested this vaccine in vivo to ascertain 1) its safety and stability when subjected to serial horse to horse passage, 2) whether it spread spontaneously from horse to horse and 3) its ability to protect against heterologous equine influenza challenge viruses of epidemiological relevance. For the stability study, the vaccine was administered to 5 ponies. Nasal swabs were collected and pooled fluids administered directly to 4 successive groups of naïve ponies by intranasal inoculation. Viruses isolated from the last group retained the vaccine's full attenuation phenotype, with no reversion to the wild-type virus phenotype or production of clinical influenza disease. The vaccine virus spread spontaneously to only 1 of 13 nonvaccinated horses/ponies when these were comingled with 39 vaccinates in the same field. For the heterologous protection study, a challenge model system was utilised in which vaccinated or naïve control horses and ponies were exposed to the challenge virus by inhalation of virus-containing aerosols. Challenge viruses included influenza A/equine-2/Kentucky/98, a recent representative of the 'American' lineage of equine-2 influenza viruses; and A/equine-2/Saskatoon/90, representative of the 'Eurasian' lineage. Clinical signs among challenged animals were recorded daily using a standardised scoring protocol. With both challenge viruses, control animals reliably contracted clinical signs of influenza, whereas vaccinated animals were reliably protected from clinical disease. These results demonstrate that Flu Avert IN vaccine is safe and phenotypically stable, has low spontaneous transmissibility and is effective in protecting horses against challenge viruses representative of those in circulation worldwide.

Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression.

To determine safety, efficacy, and immunogenicity of an intranasal cold-adapted modified-live equine influenza virus vaccine administered to ponies following induction of exercise-induced immunosuppression. Prospective study. Fifteen 9- to 15-month old ponies that had not had influenza. Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5 were vaccinated without undergoing exercise, and 5 were not vaccinated or exercised and served as controls. Three months later, all ponies were challenged by nebulization of homologous equine influenza virus. Clinical and hematologic responses and viral shedding were monitored, and serum and nasal secretions were collected for determination of influenza-virus-specific antibody isotype responses. Exercise caused immunosuppression, as indicated by depression of lymphocyte proliferation in response to pokeweed mitogen. Vaccination did not result in adverse clinical effects, and none of the vaccinated ponies developed clinical signs of infection following challenge exposure. In contrast, challenge exposure caused marked clinical signs of respiratory tract disease in 4 control ponies. Vaccinated and control ponies shed virus after challenge exposure. Antibody responses to vaccination were restricted to serum IgGa and IgGb responses in both vaccination groups. After challenge exposure, ponies in all groups generated serum IgGa and IgGb and nasal IgA responses. Patterns of serum hemagglutination inhibition titers were similar to patterns of IgGa and IgGb responses. Results suggested that administration of this MLV vaccine to ponies with exercise-induced immunosuppression was safe and that administration of a single dose to ponies provided clinical protection 3 months later.

Development of novel influenza virus vaccines and vectors.

Approaches to improve the efficacy of the current (killed) influenza virus vaccines include the generation of cold-adapted and genetically engineered influenza viruses containing specific attenuating mutations. It is hoped that these genetically altered viruses, in which the hemagglutinin and neuraminidase genes from circulating strains have been incorporated by reassortment, can be used as safe live influenza virus vaccines to induce a long-lasting protective immune response in humans. In addition, genetically engineered influenza viruses may provide a means for expressing foreign antigens. Immunization of mice with recombinant influenza and vaccinia viruses expressing specific antigens of Plasmodium yoelii resulted in a dramatic protective immune response against malaria in this model. Mice immunized with recombinant influenza viruses expressing human immunodeficiency virus (HIV) epitopes generated long-lasting HIV-specific serum antibodies and secretory IgA in the secretory nasal, vaginal, and intestinal mucosa. These results suggest that genetically engineered influenza viruses may be developed for use as live virus vaccines against influenza as well as other diseases.

The relative amount of an influenza A virus segment present in the viral particle is not affected by a reduction in replication of that segment.

The principles of influenza A virus replication and packaging are not fully understood. In order to investigate the signals required for these processes we have introduced mutations in the terminal non-coding region of an influenza A virus neuraminidase (NA) gene. Specifically, we have obtained two viruses, NA/X and NA/Y, which produced a reduced amount of NA-specific genomic RNA in infected cells but not in the viral particle. These data indicate that (i) specific signals which affect the amount of RNA in the viral particle are distinct from those required for viral replication and (ii) the amount of packaged RNA is not strictly dependent on the amount of RNA produced during replication. In addition, mutant NA/Y was shown to be effectively attenuated in mice. Thus, diminished replication of one viral segment might be a principle on which to base a live influenza virus vaccine.

Developments in mucosal influenza virus vaccines

Immunogenicity and efficacy of aerosol inactivated split influenza virus vaccines, which are threefold the strength of the vaccines for parenteral use, and cold-adapted reassortant live influenza virus vaccines were evaluated. Mucosal immune responses were evaluated by quantifying specific IgA antibody of the nasal swab solution, and systemic immune responses were evaluated by determining serum haemagglutination inhibition antibody levels. Efficacy of the aerosol inactivated vaccine was evaluated by a challenge test using live vaccine virus. It was concluded that mucosally administered inactivated influenza virus vaccine stimulated systemic and mucosal immune responses more strongly than live influenza virus vaccine and manifested a much stronger booster effect than live vaccine. Mucosal administration of inactivated influenza virus vaccine was effective in preventing infection by live vaccine virus.

Now and Future Influenza Vaccines

Influenza is a modern day plague. In the young, the clinical picture is classical, but in the elderly, the disease may go unsuspected until complications such as pneumonia develop. Influenza A and B viruses are responsible, and these viruses mutate with great regularity. Antibodies to the HA and NA surface antigens of influenza viruses, both naturally and vaccine induced, are protective. The earliest influenza vaccines were crude, toxic, and ineffective. With modern purification techniques, the egg-grown viruses have been turned into safe, immunogenic, and effective killed-virus vaccines--whole virus and split virus. Surveillance permits the correct virus strains to be incorporated into each new vaccine. Those who have been experiencing the worst effects of influenza have been identified. These individuals need to be immunized each year. In the future, live influenza virus vaccines may offer the benefits of ease of administration and longer-lasting protection. Synthetic peptides, genetically engineered antigens, and even nonantigen (anti-idiotype) vaccines are possible, but such vaccines will require adjuvant enhancement. For the present, greater efforts must be made to use existing influenza vaccines.

Effects of killed and live attenuated influenza vaccine on symptoms and specific airway conductance in asthmatics and healthy subjects.

Killed and live influenza virus vaccines were given to asthmatics and healthy subjects to investigate symptoms and alterations in their respiratory performance after vaccination. Polyvalent killed influenza virus vaccine was given to 16 asthmatics and live attenuated influenza virus vaccine to 23 asthmatics and 21 healthy subjects. Fourteen of the 16 asthmatics vaccinated with the killed vaccine displayed a significant rise in serum antibody level as measured by a single radial haemolysis in gel (SRH test). 11 of the 23 asthmatics and 14 of the 21 healthy subjects vaccinated with the live attenuated vaccine displayed a significant rise in the SRH test. Among the subjects with no measurable initial antibodies and with a significant rise in the SRH test, one asthmatic vaccinated with the killed vaccine experienced symptoms of common cold with fever and dyspnoea 1 week after vaccination. Three asthmatics and four healthy subjects vaccinated with live attenuated vaccine experienced mild symptoms, mainly rhinorrhoea, cough and sore throat 2 to 3 days after vaccination. No alterations in specific airway conductance in asthmatics or in healthy subjects were observed. We conclude that both killed and live attenuated influenza virus vaccines are tolerated well by asthmatics and appear to be safe for asthma patients.

Serological evaluation of an influenza A virus cold-adapted reassortant live vaccine, CR-37 (H1N1), in Japanese adult volunteers.

A cold-adapted influenza A virus, CR-37 (H1N1), derived from genetic reassortment between A/Ann Arbor/6/60 (H2N2) cold-adapted variant virus and A/California/10/78 (H1N1) wild-type virus, was tested in Japanese adult volunteer. The CR-37 live virus preparation induced only low-grade clinical reactions in volunteers for the first 3-4 days after inoculation. Two vaccinees who did not show any antibody changes became febrile (over 38.0 degrees C). Skin tests using the vaccine preparation and uninfected allantoic fluid were performed, and indicated that one of these two vaccines was positive for the CR-37 vaccine preparation. A high proportion of the vaccinees whose sera had a haemagglutination-inhibition (HI) antibody titre against the vaccine strain of less than or equal to 64 before inoculation, seroconverted in both HI and neuraminidase-inhibition (NAI) antibody titrations, and only a few seroconverted in the titration of antibody against type-specific internal antigens. The serological examinations against heterotypic H1N1 variants indicated that the cold-adapted live influenza virus vaccine could induce a broad spectrum of HI antibody reactivity and immunity of long duration.

Characterization and clinical evaluation of live influenza a vaccine prepared from a recombinant of the A/USSR/92/77 (H 1N 1) and the cold-adapted A/Ann Arbor/6/60 (H 2N 2) strains

Live influenza vaccine was prepared after genetic recombination of the A/USSR/92/77 (H 1N 1) strain with the cold-adapted A/Ann Arbor/6/60 (H 2N 2) strain. The recombinant contains the genes coding for the HA and NA proteins from the A/USSR/92/77 (H 1N 1) strain and the genes coding for the P 1, P 2, P 3, NP, M and NS proteins from the A/Ann Arbor/6/60 (H 2N 2) strain. To assess the properties of this vaccine, it was administered under double-blind conditions to 14 healthy volunteers, while another 14 healthy volunteers received placebo. The vaccine virus appeared to be sufficiently attenuated. No febrile reactions were observed. The vaccinees showed an increase in mean serum haemagglutination-inhibiting antibody level from 19 to 73 after two vaccinations. From nasal swabs and antibody responses, it was concluded that the vaccine virus showed no transmission to the placebo group under conditions of close contact. Also, the vaccine virus was found to be genetically stable. It is concluded that this live influenza virus vaccine meets the requirements for safe use in humans. However, several problems still exist which may impede a general use of live influenza vaccines.

From the National Institute of Allergy and Infectious Diseases. The present status of live influenza virus vaccine.

From the National Institute of Allergy and Infectious Diseases. The present status of live influenza virus vaccine.

A study of live influenza virus vaccine in patients with chronic bronchitis: Report to medical research council's committee on influenza and other respiratory virus vaccines

A multicentre study of the effects of influenza virus RIT 4050 (H3N2) in patients with chronic bronchitis was conducted by members of an MRC Committee. The results showed that RIT 4050 vaccine virus did not cause a deterioration in clinical or physiological status in these patients within the limitation of the relatively reproducible ventilatory tests which were employed. This conclusion applied equally to those who were inoculated and became infected and to those who failed to develop serological evidence of infection. The relatively high proportion of antibody-negative volunteers not infected by the inoculated virus raises doubts concerning the value of this method of immunization for patients at risk during influenza epidemics.

Alterations in Pulmonary Function Following Respiratory Viral Infection

Respiratory viral illness is a major cause of morbidity in both adults and children. This report focuses on both the acute and chronic effects on respiratory function of these ubiquitous infections. Infant airways are particularly vulnerable due to the relatively low conductance in immature peripheral airways. Bronchiolitis, caused predominantly by respiratory syncytial virus, is the most important of these viral illnesses and is emerging as a major risk factor for the subsequent development of obstructive airway disease in adults, possibly by interference with normal alveolar proliferation. The basic pathogenic mechanism involved in adult respiratory viral infection is bronchial hyperreactivity, presumably secondary to epithelial damage and resultant sensitization of rapidly adapting airway receptors. In addition, there may be virus-related alterations in the autonomic and humoral regulation of airway tone. Viral infections may alter the effects of common air pollutants on respiratory function.

The Infant Rat as a Model for Assessment of the Attenuation of Human Influenza Viruses

The intranasal infection of infant rats with Haemophilus influenzae type b can be considerably enhanced by prior infection of the rats with influenza virus. When influenza virus A/England/939/69 was used to infect the animals a minimum of 10(4-0) EID50 was required to enhance H. influenzae infection; infection with 4 x 10(6) H. influenzae bacteria was needed to reveal this enhancement and infant rats two days old at the time of virus inoculation had to be used. By this method, nine strains of influenza virus were assessed for their ability to enhance H. influenzae infection, and the results were compared with their known virulence for man. The results showed a close correlation in this respect for all of the viruses, except strain A/PR/8/34. The replication of these viruses in infant-rat turbinates and lungs was also studied; virus concentrations in turbinate tissues 48 h after infection showed a close correlation with virulence for man. Thus, three influenza virus strains known to be virulent for man reached concentrations in infant-rat turbinates ranging from 10(4-8) to 10(5-7) EBID50/0-05 ml at 48 h; the concentrations of six viruses known to be attenuated or non-infectious for man grew less well in infant rat turbinates, and reached concentrations at 48 h of 10(1-0) to 10(3-5) EBID50/0-05 ml. The results are discussed in relation to the use of the infant-rat model for assessment of the attenuation of candidate live influenza virus vaccine strains.

Amantadine for Influenza

To the Editor.— Although there is certainly a case to be made for the consideration of amantadine as a chemoprophylactic agent, perhaps even a therapeutic agent, in influenza type A virus infections, the commentary by Chanin has some misleading implications. First of all, Chanin recommends a drug dosage that is one half that of the licensed product, yet he presents no data to substantiate the efficacy of his reduced dosage schedule. Secondly, in discussing the effects of influenza vaccine on the pulmonary function of patients with chronic lung disease, he alludes to studies with experimental live influenza virus vaccines but fails to differentiate for the reader that this was an investigative vaccine totally different from the licensed, inactivated vaccines that are used in prophylaxis. This confusion is further compounded by his comment that the immunization leads to adverse effects in the high-risk patient. Finally, he restates the old complaint that

Formation of secretory and circulating antibodies after immunization with live and inactivated influenza virus vaccines.

The formation of secretory and circulating antibodies in volunteer teenagers and adults immunized intranasally with live and inactivated influenza virus vaccines has been studied. The antibody response to the vaccine was directly dependent upon the amount of virus contained in the inoculum. The live vaccine was more effective than the inactivated vaccine in stimulating the production of secretory antibodies. Antibody levels in serum before immunization did not affect the production of secretory and circulatory antibodies. However, production of both of these antibodies was observed to be inversely correlated with the initial level of secretory antibodies. Secretory antibodies were shown to have a wider spectrum of activity against type A influenza viruses than circulating antibodies. Antibody titers in nasal secretions were correlated with the concentration of IgA in total protein but could not be correlated with concentrations of IgG.

Respiratory effects of live influenza virus vaccine: healthy older subjects and patients with chronic respiratory disease.

Twenty-one healthy, middle-aged volunteers and 8 patients with chronic lung disease were given live, attenuated influenza virus vaccine by nasal spray. Forced vital capacity, 1-sec forced expiratory volume, ratio of 1-sec forced expiratory volume to forced vital capacity, residual volume, ratio of airway conductance to lung volume, maximal expiratory flows after exhalation of 50 and of 75 per cent of the forced vital capacity, closing volume, slope of Phase III, volume of isoflow, single-breath diffusing capacity for CO, and arterial blood gases were measured before and 3, 7, 10, and 21 days after exposure. Vaccination was well tolerated by the healthy volunteers without change in pulmonary function. In contrast, the patients tended to develop increased respiratory symptoms and had a slight decrease in mean forced expiratory volume in 1 sec 3 weeks after vaccination.

The production of live attenuated influenza A strains by recombination with A/Okuda/57 (H2N2)

Summary A new recombination system for the production of live attenuated influenza-A vaccine strains is described. The attenuated parent is the Japanese strain A/Okuda/57 (H2N2) which has a known passage history and a good record of human safety. This virus has been recombined with two recent field isolates, A/England/42/72 and A/Finland/4/74, and in each case several recombinants were isolated and tested in volunteers. These recombinants differed in their degree of attenuation, but on each occasion it was possible to choose one that was suitably attenuated for a candidate vaccine strain. The genetic stability of such a recombinant produced with the A/England/42/72 strain was demonstrated by subjecting it to three successive human passages. A single intra-nasal dose of the A/Finland/4/74 recombinant vaccine gave a seroconversion rate of 75%. This recombination system offers considerable advantages for the production of live influenza virus vaccines.