Genetic Basis of Attenuation of Cold-Adapted Influenza Strain B/Leningrad/14/17/55 - Backup Master Donor Virus for Influenza Type B Live Attenuated Vaccines.

The reassortant vaccine strain of live attenuated influenza vaccine inherits temperature sensitivity and areactogenicity from cold-adapted attenuated master donor virus. In Russia, B/ USSR/60/69 master donor virus (B60) is currently in use for the preparation of live attenuated type B influenza vaccine candidates. Trivalent live attenuated influenza vaccine based on A/ Leningrad/134/17/57 and B60 are licensed for the use in Russia for single dose vaccination of adults and children over 3 years. B/Leningrad/14/17/55 (B14) cold-adapted virus is a backup master donor virus for live attenuated type B influenza vaccine. According to our preliminary estimates, it is more attenuated than B60, which can allow expanding applicability of this vaccine for children under 3 years of age. In this paper, the role of B14 genes in its attenuation was assessed. Representative collection of reassortants of B14 with epidemic influenza B viruses was obtained, a phenotypic analysis of reassortants was performed, and their pathogenicity for animals was assessed. The leading role of PB2 and PA genes in attenuation of B14 master donor virus was proven.

[Local antibody immune responses in influenza patients and persons vaccinated with seasonal, pre-pandemic, and pandemic live attenuated influenza vaccines].

Mucosal immunity is one of the most important factors of human anti-influenza defense. The data about local immune responses in influenza A (H3N2) patients and in persons vaccinated within 2000-2009 with different seasonal LAIVs, A (H1N1)pdm2009 LAIV, and A (H5N2) LAIV are discussed. The influenza infection resulted in the larger quantities of local IgA and IgG conversions than seasonal LAIV vaccination. 56% of young (18-21 y.o.) persons had high titers (> or = 1:64) of IgA to A (H1N1)pdm2009 virus before its circulation. 19% of persons had anti A (H5N2) IgA before vaccination. Two-fold vaccination with A (H1N1) pdm2009 and A (H5N2) LAIVs resulted in local antibody conversions in 54% and 27% of volunteers, respectively. Both these vaccines increased local IgA avidity. The number of antibody conversions after vaccination with seasonal LAIVs was in inverse dependence on their titers before vaccination. These results make it possible to conclude that the intensity of local antibody immune response to any LAIV depends on the state of local immunological memory, particularly on the presence of the crossreactive antibody-secreting B cells.

[Humoral and cell-mediated immune responses in humans to the A/California/07/ 2009 (H1N1) virus, A(H1N1)pdm2009].

During the twentieth century the world faced four influenza A pandemics: A (H1N1) in 1918, A (H2N2) in 1957, A (H3N2) in 1957 and A (H1N1) recirculation in 1977. In the beginning of 2009 the global spread of A(H1N1)pdm2009 virus was detected. In consideration of clinical evidences and genetic data analysis WHO declared as the novel pandemic of 21th century. However, the fact of exceedingly prolonged previous worldwide circulation of A (H1N1) influenza viruses was not taken into account. Further development showed epidemiological prognosis not to be accurate enough. The present work is an attempt to analyze this question from the immunological standpoint based on our studies of antibody and cellular immunity to A(H1N1)pdm2009 virus in vaccinated and non-vaccinated persons of different ages. The study results allow concluding that A(H1N1)pdm2009 is the drift variant of A (H1N1) viruses antigenically close to A/Swine/1976/1931 (H1N1). It was shown that the significant of persons have cross-reactive B and T cell immunological memory to A(H1N1)pdm2009 strain. This could be a reason of decreased A(H1N1)pdm2009 pandemic severity.

[Genetic and phenotypic analysis of heterogeneous population of a cold-adapted donor of the A/Leningrad/134/17/57 (H2N2) attenuation and of the donor-based reassortant influenza vaccine strains].

Cold-adapted (CA) temperature sensitive and attenuated virus A/Leningrad/134/17/57 (H2N2) (Len/17) has been recently used in Russia as a donor of internal genes in the preparation of reassortant vaccine strains of CA live influenza vaccine (LIV) for all age groups. The Len/17 population was found to be heterogeneous and to be made up of clones, which differ by combinations of mutations in internal genes. Around 50% of the Len/17 population had clones with all 8 coding mutations in internal genes. The others were made up of clones with mutation combinations, which were different from the original Len/17. The PCR restriction method was used to analyze 5 clones of Len/17 and 8 LIV vaccine strains. There were no Ala-86-Thr mutation in the M2 protein in 4 clones and 3 vaccine strains. The PB-1 gene of 4 clones and 3 vaccine strains had a mutation encoding Met-317-IIe more typical of a more attenuated virus A/Leningrad/134/47/57 (H2N2) (Len/47). The NP protein of a clone had a mutation Leu-341-IIe also typical of Len/47. However, neither the absence of mutation in the M2 gene nor an extra mutation in the PB1 gene affected the attenuation extent of reassortant CALIV.

[Local immune response to live cold-adapted reassortant influenza vaccine in children, adults, and aged people]. / Mestnyi immunnyi otvet na zhivuiu kholodoadaptirvannuiu reassortantnuiu grippoznuiu vaktsinu u detei, vzroslykh i predstarelykh lits.

A study was conducted to compare the production of the serum and local IgA-antibodies in persons of different age groups (aged: 3-6, 7-14, 18-30, 65-89) after a single intranasal immunization with trivalent live cold-adapted reassortant of influenza vaccine (LIV). The geometric mean of titers of local IgA-antibodies increased, during post-vaccination period, against influenza viruses A(H1N1), A(H3N2) and B as much as people's age went up. It is noteworthy, that the parameters of the young and elderly did not virtually differ. As for the children, aged 3-6 and especially 7-14, an active local immune response developed in them to the LIV administration. Thus, no pronounced age-related immunologic insufficiency was found in children, aged 3-14, or in the elderly above 65 to the induced local response caused by LIV.

[Humoral and local immune response to the influenza vaccine in people of old and young ages]. / Gumoral'ny i mestnyi otvet na grippoznye vaktsiny u lits pozhilogo i molodogo vozrasta.

The specific features of the humoral and local immune responses to influenza vaccines were comparatively studied in people of different age groups. A total of 79 elderly people (aged 67-89) and 80 young people (aged 18-27) were immunized according to one of the four schemes: live cold-adapted reassortant trivalent influenza vaccine (LIV), administered intranasally; inactivated split trivalent influenza vaccine (IIV), administered parenterally; a combination of both above vaccines; and placebo. IIV was found, as compared to LIV, to stimulate more effectively the production of circulating antihaemagglutinins as well as of IgG,-, Ig1-, and Ig3-AT in young persons, while LIV has advantages before IIV in stimulating the synthesis of these immunoglobulins in the elderly. LIV has advantages before IIV in stimulating the synthesis of secretory IgA-AT irrespective of an age of the immunized persons. The combined immunization of the elderly by both vaccines increases the quantitative parameters of the humoral and local responses up to the level of intensity observed in young people. The obtained data are indicative of the possibility of correcting the immune response in the high-risk elderly in respect to influenza infection.

[The temperature sensitivity of epidemic influenza A viruses as a marker of immunogenicity of reassortant vaccinal strains]. / Temperaturochuvstvitel'nost' épidemicheskikh virusov grippa A kak vozmozhnyi marker immunogennosti reassortantnykh vaktsinnykh shtammov.

The influence of ts-phenotype of epidemic viruses and of cold-adapted (CA) reassortant vaccines' strains, appropriately prepared, produced on the human immunogenicity was under investigation. A widespread variability of epidemic viruses' thermal sensitivity sign was established. It was shown that the CA reassortant vaccine strains, obtained through crossbreeding of attenuation donors and of thermally resistant epidemic viruses, are described by a higher immunogenicity. Therefore, the immunogenicity of live influenza vaccines (LIV) can be defined by the ts-phenotype of epidemic parent viruses, which must be sampled for the reassortant vaccine strains not only through searching for samples of antigenically actual viruses but also through search for non-ts-phenotype viruses.

[The investigation of the safety, genetic stability and immunogenicity of live influenza vaccine for adults in vaccination of 3-6 years old children]. / Izuchenie bezvrednosti, geneticheskoi stabil'nosti i immunogennosti zhivoi grippoznoi vaktsiny dlia vzroslykh pri vaktsinatsii detei 3-6 let.

The study of the based on the A/Leningrad/134/17/57/(H2N2) attenuated adult live influenza vaccine (LIV) investigated features for immunization of the children, aged 3-6 years. During autumn, 1999, out of 256 children, aged 3-6 years, residents of the Leningrad region, who attended the kindergarten, 184 children were immunized with 1 or 2 doses of the live influenza vaccine, and 72 ones were given placebo. There were no any moderate or strong temperature reactions revealed after the inoculation. The LIV was shown to be genetically stable. After a single dose of the vaccine seroconversion to influenza type A virus and to influenza type B virus was observed respectively in 58% and in 39% of seronegative 3-6 year old vaccinees. The twofold LIV administration failed to give any advantages in stimulation of the immune response. During 6 months after immunization the morbidity rate in vaccinees did not exceed the morbidity rate in unvaccinated children. Thus LIV for adults proved safe and immunogenic and can be recommended for single dose immunization both of adults and children.

[The comparative characteristics of the safety, immunogenic activity and prophylactic potency of the adult and children types of live influenza vaccine in schoolchildren aged 7-14 years]. / Sravnitel'naia otsenka bezvrednosti, immunogennoi aktivnosti i profilakticheskoi éffektivnosti vzroslogo i detskogo variantov zhivoi grippoznoi vaktsiny u shkol'nikov 7-14 let.

In Russia for prevention of influenza in children, aged from 3 to 14 years, the children's live influenza vaccine (LIV), based upon A/Leningrad/134/47/57(H2N2) master strain (LIVI) is used. The need for double immunization appears to be one out of the faulties of this preparation. The study was aimed to comparing the safety, immunogenic activity and prevention of influenza by LIV for adults (LIVII) (A/Leningrad/134/17/57(H2N2 master strain) and LIVI in children aged from 7 to 17 years under similar administration schedule. The safety, the preventive efficacy, humoral and secretory immunity were studied. In total 2486 persons, including 539 children, twice inoculated with LIVI, 971 persons once inoculated with LIVII, and 840 treated by placebo were obserbed. From the data of the clinical observations during 7 days after immunization both vaccines appeared to be low reactogenic. The LIVII advantages in induction of the humoral and secretory antibodies in comparison with children's vaccine had been revealed. Both vaccines were highly efficacious, the efficiency of both preparations was more pronounced after serologic correction of the diagnosis. The results obtained permit to recommend the single immunization by the variant of LIV at the base on A/Leningrad/134/17/57/(H2N2) master strain for prevention of influenza in school children.

[Immune response to live influenza vaccine]. / Immunnyi otvet na zhivuiu groppoznuiu vaktsinu.

Priority data on the induction, by using a Russian live cold-adapted reassortant influenza vaccine (LIV), of the cellular and humoral immunity with regard for attenuation and genetic reassortment of vaccine stains as well as with regard for the age of vaccinated persons and the production of Th1 (IFNY, IL-2) and Th2 (IL-4) cytokine markers in vitro are presented. It was demonstrated in vivo that a pathogenic virus of the A group by far more actively induced the lymphocyte apoptosis as compared with attenuated genetically reassorted stains. Unlike the influenza pathogenic virus, the genetically attenuated and reassorted strain did not produce any negative effects on the induction of cellular immunity. A comparative study of the LIV immunogenic properties in vaccinated persons showed an advantage of LIV over inactivated influenza vaccine (IIV) in stimulating the cellular and local immunity in the elderly. Unlike IIV, LIV induced an active and balanced immune response developing due to Th1 and Th2 activation. LIV was found to stimulate well enough the production of IFN and IL-2 in both young and old persons.

[In vitro proliferative activity of lymphocytes from elderly persons after separate and combined immunization with live and inactivated flu vaccines]. / Proliferativnaia aktivnost' limfotsitov lits pozhilogo vozrasta in vitro pri razdel'noi i sochetannoi immunizatsii zhivoi i inaktivirovannoi grippoznymi vaktsinami.

Cellular (lymphocyte proliferation activity--LPA), humoral (serum antibodies), and secretory (IgA antibodies from the upper respiratory tract) immune responses were compared in 45 subjects aged 66-95 years, vaccinated with two influenza trivalent A(H1N1) + A(H3N2) + B vaccines: Russian live attenuated cold-adapted reassortant (LIV) and USA inactivated split-virus (IIV) vaccines. None of immunization protocols suppressed LPA after in vitro stimulation of cell culture with homologous virus antigens and nonspecific polyclonal mitogen (PHA). Simultaneous LIV + IIV vaccination was the most effective method of immunization, inducing humoral, secretory, and cellular immunity. LIV more actively than IIV stimulated the lymphoproliferative immune responses. Fluctuations in the mean values of cellular, humoral, and secretory immunity were in good correlation over the entire period of observation (19 weeks). Analysis of individual immune responses showed that a significant increase in quantitative parameters of LPA was observed only in 39-52% vaccinees.

[Production of interleukin-2 in vitro and in vivo in elderly people, vaccinated with live and inactivated flu vaccines separately and combined]. / Produktsiia interleikina-2 in vitro i in vivo u pozhilykh liudei, privitykh razdel'no i sochetanno zhivoi i inaktivirovannoi grippoznymi vaktsinami.

Forty-three elderly individuals were immunized with Russian trivalent live cold-adapted influenza vaccine (LIV) and US trivalent influenza vaccine (IIV) administered separately or in combination. IL-2 production in vitro (in supernatants of cultures of lymphocytes stimulated with homologous viral antigens and PHA) and in vivo (in blood serum) and other factors of specific antiinfluenza immunity were compared. Vaccination of elderly subjects with commercial vaccines induced T-helper immunological memory, which manifests by increased secretion of IL-2 in vitro and in vivo. Simultaneous vaccination with LIV + IIV and revaccination (in 1 month) with LIV was the most effective method stimulating IL-2 production. The levels of IL-2 production in vitro were in good correlation with the secretion of this cytokin in vivo, lymph proliferation, and serum antibody production. No correlation between IL-2 production in vitro and the formation of local immune response (IgA in nasal swabs) was detected.

[Immune response of elderly persons depending on the number of annual seasonal immunizations of live and inactivated influenza vaccines]. / Immunnyi otvet lits pozhilogo vozrasta v zavisimosti ot chisla ezhgodnykh sezonnykh immunizatsii zhivoi i inaktivirovannoi grippoznymi vaktsinami.

A total of 159 subjects aged 65-87 years were immunized with live cold-adapted reassortant influenza vaccine (CRIV), inactivated influenza vaccine (IIV), and with both vaccines (CRIV + IIV) one year, two and three years running. The frequency and intensity of accumulation of postvaccinal secretory and humoral antibodies in elderly subjects depend on the scheme of immunization and history of vaccinations. Combination of the two vaccines effectively stimulated both components of immunity and ensured a longer persistence of postvaccinal antibodies in high concentrations. Immunization with CRIV + IIV for three years resulted in a gradual increase of the intensity of prevaccination secretory and humoral immunity. Before the third seasonal immunization the majority (63-75%) of vaccinees had antibodies in protective titers.

[Formation of humoral and secretory immunity in elderly persons with different schemes of immunization with flu vaccines]. / Formirovanie gumoral'nogo i sekretornogo immuniteta u lits pozhilogo vozrasta pri razlichnykh skhemakh immunizatsii grippoznymi vaktsinami.

The immunological efficacy of 5 protocols of immunization with two influenza vaccines are compared in 168 elderly subjects aged 64 to 87 years. Russian live cold-adapted reassortant trivalent (LCIV) and American inactivated cleaved trivalent (ICIV) influenza vaccines were used. The protocols of vaccination were as follows: 1) simultaneous vaccination with LCIV and ICIV and revaccination with LCIV after 1 months; 2) simultaneous vaccination with LCIV and ICIV and revaccination with placebo after 1 month; 3) vaccination and revaccination with LCIV; 4) vaccination with ICIV and revaccination with placebo; 5) vaccination and revaccination with placebo preparation (control); 6) vaccination with ICIV and revaccination with LCIV after 1 month. The incidence of significant increments and intensity of accumulation of serum (assessed by the hemagglutination inhibition test) and secretory (IgA) antibodies (assessed by enzyme immunoassay) was evaluated. For elderly subjects, simultancous vaccination with LCIV and ICIV followed by revaccination with LCIV is the most effective. After such vaccinations both secretory and humoral immune responses are characterized by the highest production of secretory IgA and serum antibodies. The quantitative parameters of both types of immune response in elderly subjects thus immunized are much higher than in young subjects vaccinated traditionally, that is, by LCIV or ICIV alone.

[Current strategies for vaccine prevention of influenza]. / Taktika vaktsionoprofilaktiki grippa na sovremennom étape.

Six-year immunologic surveillance of schoolchildren vaccinated according to different schedules in the town of Novgorod demonstrated the efficacy of overall vaccinations of children and young people with live anti-influenza vaccines in autumn and winter for 2 years. Then an interval of 3 years is to be made, followed by another 2-year revaccination cycle, provided the same serologic subtypes of influenza A and B are still circulating.

[Prophylactic effectiveness of a live recombinant influenza type A vaccine in immunizing children aged 3-14 years]. / Profilakticheskaia éffektivnost' zhivoi grippoznoi rekombinantnoi vaktsiny tipa A pri immunizatsii detei 3-14 let.

Children aged 3 to 14 were immunized with live recombinant influenza A vaccine; about 120,000 children were followed up for 6 months. Analysis of the morbidity (excepting ARVI and influenza) of the immunized and control groups permitted a conclusion about the safety of the preparation. The protective index of vaccine efficacy during influenza epidemic caused by A/Taiwan/1/86(H1N1) virus was 1.3 to 1.42. Live recombinant influenza vaccine is recommended for public health to be used for protection of children aged 3 to 14 from influenza.

[A comparative study of live and inactivated influenza vaccines: the organization of the observation and the results of a study of their reactogenicity and immunogenicity]. / Sravnitel'noe izuchenie zhivoi i inaktivirovannykh grippoznykh vaktsin: organizatsiia nabliudeniia i rezul'taty izucheniia reaktogennosti i immunogennosti.

Schoolchildren of 30 to 34 schools of Novgorod were vaccinated over a three-year period with Russian live cold-adapted attenuated vaccine for children and whole-virus inactivated vaccines and placebo for comparative field study of the vaccines properties and efficacy. In control trials both bi- and trivalent live attenuated vaccines were well tolerated and areactogenic. A whole-virus inactivated trivalent vaccine induced mild and moderate fever and local reactions in 2-4% of the vaccinees. Special observations are necessary to establish the possibility of use and to determine a dose of this inactivated vaccine for immunization of children, especially those of 7-10 years of age. All the vaccines induced HI antibody production in 50-80% and antineuraminidase in 50-70% of seronegative children. The pattern of the results was similar to that in revaccinated children with preexisting antibody at a level of 1:20, but much lower in children with the initial titre above 1:20. After the 3rd year of vaccination the immune response of the vaccinees was similar, most of the results depending on the initial antibody titre and also on the change of vaccine strains. This raises a question of the expediency of annual influenza revaccination of the same person after 2 years of successful immunization and of the necessity of vaccine strains replacement after 2-3 years of use.

[The immunogenic properties and prophylactic efficacy of a live polyvalent influenza vaccine in children 5 to 14 years old]. / Izuchenie immunogennykh svoistv i profilakticheskoi éffektivnosti zhivoi grippoznoi polivalentnoi vaktsiny u detei 5--14 let.

Production lots of a live influenza vaccine made of strains A/47/T (N1H1), A/47/6/2 (H3N2), and B/60/32 were used for vaccination of 3663 children aged from 5 to 14 years inoculated twice with monovaccines, a trivaccine made of the above strains, or placebo. Both mono- and polyvaccine were practically areactogenic. An average per cent of subjects with a significant rise in antibody titres to the respective three antigens was 60%. The efficacy of the vaccination was 31.0-42.8% for monopreparations and 36.3% for the trivaccine. The studies showed the possibility and expedience of using for children the live influenza vaccine in the form of a polyvalent preparation including current influenza type A and B viruses.

[The inoculation properties of live recombinant influenza vaccine types A and B used separately and jointly in children 3 to 14]. / Privivochnye svoistva zhivoi grippoznoi rekombinantnoi vaktsiny tipov A i B pri razdel'nom i sovmestnom primenenii detiam 3--14 let.

The reactogenicity and immunizing activity of vaccine influenza virus A (H1N1) and B strains used as mono- and bi-preparations in children of 3 to 14 years was studied. No increased reactogenicity after the use of bivaccine was observed in the children. Febrile reactions as well as 9 other clinical symptoms which could indicate the reactogenicity of the vaccines were identical for mono- and bivaccine and corresponded to the requirements of the technical documents for the vaccine. The optimal conditions for the evaluation of the immunogenicity of the B component by HI test were developed, and the necessity of using additionally the enzyme immunoassay for this purpose is substantiated. The above method demonstrated that the immunogenicity of the live influenza type A and B vaccine was high in children. No significant inhibition of immunological parameters was observed when the two viruses were combined in the bivaccine.

[The formation of an immune response in volunteers inoculated with a live recombinant influenza vaccine]. / Formirovanie immunnogo otveta u dobrovol'tsev, privitykh zhivoi grippoznoi rekombinantnoi vaktsinoi.

The capacity of a live influenza vaccine (LIV) to stimulate cytotoxic cells (ADCMC and NK) was studied in 49 volunteers and 56 patients with influenza. Experimental batches of LIV from influenza A and B viruses prepared by genetic recombination on the basis of cold-adapted attenuation donors were used. Type A and B LIV were shown to stimulate the cytotoxic cell-mediated and humoral immunity; the intensity of immune response, however, depended on the molecular genetic characteristics of the vaccine (genome structure, properties of the donor of attenuation), its biological activity and capacity of reproduction in tissues.