[New cold-adapted donor strains for live influenza vaccine].

Cold-adapted (CA) strains A/Krasnodar/35 and B/Victoria/63 were isolated using passages of A/Krasnodar/101/59 and B/Victoria/2/87 wild type strains at low temperatures. The resulting CA strains possessed TS and CA phenotypes and had a reduced ability to reproduce in mouse lungs and nasal turbinates. They displayed a high protective efficacy in experiments on mice. The two CA strains reproduced well in chick embryos and MDCK cell line without change of TS and CA markers. The CA A/Krasnodar/35 strain during passages at low temperature acquired 13 mutations in the 6 internal genes, 8 of those mutations led to amino acid changes. The CA B/Victoria/63 strain acquired 8 mutations in the internal genes, 6 of which led to amino acid changes. The intranasal vaccination of mice with the CA A/Krasnodar/35 strain led to a transitory suppression of various lymphocyte subpopulations, as well as to an increase in the number of some other cell types. The CA strains in question may be used in the future as attenuation donors for live influenza vaccines.

[High level of efficacy and safety of antiviral vaccines and unsubstantiated critique].

To counterbalance the unsubstantial declarations of some vaccinologists that vaccines and vaccination are not only useless, but also injurious to the health, this work represents the evidence that vaccines and vaccination not only reduce the morbidity of viral infection, but also allow some viral diseases to be eradicated and eliminated. The work also adduces the data about reducing economic impact of viral infections with the help of vaccination, as well as the data, which clearly show that serious reactions to vaccination are thousands of times less frequent than reactions and complications caused by infectious diseases.

[Epidemiologic and economic effectiveness of school closure during influenza epidemics and pandemics].

Epidemiologic and economic effectiveness of school closure during influenza epidemics and pandemics is discussed. Optimal effect of school closure is observed when this measure is taken at the start of the epidemic or pandemic and for a sufficiently long time. School closure during high morbidity among schoolchildren, in the middle (at the peak) and by the end of epidemic or pandemic does not influence significantly the spread of influenza or morbidity. Significant economic losses and other negative consequences of school closure are noted. School closure may be the most appropriate during the emergence of influenza pandemic when the pandemic vaccine is not yet available, however timely mass immunization of schoolchildren against influenza may be a more appropriate measure than school closure for the reduction of influenza morbidity and spread during seasonal influenza epidemics.

[Study of immunogenicity and protective efficacy of a novel inactivated vaccine with chitosan against influenza A/H1N1/2009].

AIM: Study of immunogenicity and protective efficacy of a novel inactivated vaccine with chitosan against influenza A/H1N1/2009. MATERIALS AND METHODS: Influenza virus A/California/7/2009 (H1N1) strain was used in the study. Mice were immunized twice (21 day interval) with experimental samples of inactivated influenza vaccine: No. 1--without the addition of chitosan, No. 2--with addition of chitosan. The blood was obtained 21 days after the first and 10 days after the second immunization with the vaccines and was treated with RDE. Antibody levels were evaluated in HI reaction. RESULTS: HI reaction method showed that antibody titers induced after immunization of vaccine No. 2 were higher than those induced after immunization with vaccine No. 1. Evaluation of protective efficacy of the vaccines against an experimental form of influenza infection in mice showed that after immunization with vaccine that does not contain chitosan the level of virus accumulation does not differ from the control statistically significantly (p < or = 0.05), at the same time the level of virus accumulation in the lungs of infected animals immunized with chitosan containing vaccine significantly (significantly with 95% probability) decreased by an average 3.01g when compared with control. CONCLUSION: Comparative analysis of immunogenicity and protective efficacy of experimental samples of inactivated influenza vaccine against influenza A/H 1N1/2009 showed that the vaccine with the addition of chitosan stimulates the formation of a higher immune response and promotes a more significant suppression of influenza A infectious agent reproduction in the lung target-organ.

[Increasing the immunogenicity of inactivated chitosan adjuvanted vaccine from A/California/7/09 (H1N1) strain and analyzing the antigenic specificity of this influenza virus strain].

Addition of chitosan as an adjuvant to subunit vaccine from the swine origin influenza virus A/California/7/09 (H1N1) increases vaccine immunogenicity by 8-16 times and significantly enhances its protective potency. Single immunization with chitosan adjuvanted vaccine induced similar antibody titers as two immunizations with unadjuvanted vaccine. Chitosan stabilized the immunogenicity of subunit vaccine when stored at 4 degrees C. The antigenic specificity of the A/California/7/09 (H1N1) virus strain did not resemble substantially that of the human influenza strains A/Brisbane/59/07 (H1N1) and A/Solomon Isles/3/06 (H1N1), which are among the 2008/2009 and 2007/2008 seasonal influenza vaccines, respectively, as well as that of the human influenza H1N1 virus strains that circulated about 30 years ago.

[Problem of influenza prophylaxis by vaccines].

Scientific data is presented and problems of influenza prophylaxis in various age groups are discussed. Influenza prophylaxis in neonates is possible by inducing maternal antibodies, this dictates the necessity of influenza vaccination in pregnancy. Problems of influenza prophylaxis are most pressing in the group of children from 6 months to 2 years of age. More effective vaccines that do not cause adverse reactions are necessary for the children of this age group. Influenza prophylaxis in healthy working adults is most important for reducing economical impact during influenza epidemics. Influenza prophylaxis in the elderly is reasonable by using novel and more effective vaccines with adjuvants. The optimal method for influenza prophylaxis in the population in general is mass vaccination of children (80%), when, besides the induction of protection in children, influenza morbidity may decrease up to 80% in the other age groups of unvaccinated population.

[Live cold-adapted influenza vaccine: state-of-the-art].

The review characterizes the currently used cold-adapted donor strains of influenza virus attenuation to prepare cold-adapted reassortants with actual epidemic influenza virus strains. It considers new procedures for preparing attenuated influenza virus strains for live influenza vaccines, as well as analytical methods and the genome composition of reassortants. Recent data on the safety of live cold-adapted influenza vaccines (LCAIVs), including those on the genetic stability of vaccine reassortants and the immunogenicity and efficacy of these vaccines for different age groups, are discussed. There is evidence for the design of live human vaccines against avian influenza. It is concluded that LCAIVs are highly effective for immunization of children.

[Enhancing the immunogenicity of inactivated polio vaccines with chitosan used as an adjuvant].

Addition of chitosan to inactivated trivalent polio vaccine or inactivated preparations of attenuated poliomyelitis viruses (Sabin strains) significantly increases immunogenicity of these inactivated poliomyelitis virus preparations. High neutralizing antibody titers are detected after two immunizations of mice and a single immunization of rats, as well as when the antigen dose was reduced by 4 times. Addition of chitosan as an adjuvant significantly induces cellular immunity.

[Increase of immunogenicity of cold-adapted influenza vaccine by using adjuvant].

AIM: To assess increase of protective efficacy of live cold-adapted (ca) influenza vaccine after addition of adjuvant chitozan. MATERIALS AND METHODS: Used viruses: ca donor of attenuation A/Krasnodar/101/35/59 (H2N2) and epidemic strain A/Krasnodar/101/59 (H2N2); as an adjuvant--derivative of chitozan and microparticles of chitozan. Experiments were performed in outbred mice. Protective effect of immunization was measured by intranasal challenge by virulent strain of virus. Immune response was assessed by ELISA and indirect hemagglutination inhibition assay. RESULTS: During intranasal immunization of mice with intact CA donor of attenuation A/Krasnodar/101/35/59 (H2N2) addition of 1% solution of chitozan glutamate to vaccine material resulted in increased serum IgG in immunized mice and protective effect of immunization. Addition of adjuvant to ca donor strain did not influence on its ts-characteristic. It was shown that inactivated with ultraviolet radiation ca donor strain in combination with chitozan did not protect against infection caused by virulent strain A/Krasnodar/101/59, whereas the same doses of intact ca donor strain with chitozan were protective. Chitozan did not enhance replication of donor strain in upper respiratory tract of mice. CONCLUSION: Obtained data demonstrate that chitozan as a mucous-adhesive adjuvant could increase efficacy of live ca influenza vaccine.

[Swine-origin influenza H1N1/California--passions and facts].

Analysis of pandemic caused by swine influenza virus H1N1/California showed moderate virulence of this virus compared to pandemic viruses, which caused pandemics in 1918, 1957, and 1968. During seasonal influenza epidemic in countries of southern hemisphere (June-August 2009) despite on circulation of H1N1/California strain, epidemics was caused by human influenza viruses H3N2 and H1N1. It was concluded that strain H1N1/California could not be attributed to pandemic strains of influenza viruses.

[Prevention of influenza in pregnant women and neonatal infants].

The review presents the data available in the literature on the incidence of influenza, postinfluenza complications, hospitalizations, and deaths in pregnant women, on the negative fetal and neonatal impact of this disease in pregnant women, on vaccination of pregnant women with inactivated influenza vaccines. It also gives data on the high rates of influenza complications, admissions, and death in the newborns and on possible prevention of neonatal influenza at the expense of maternal antibodies. It is concluded that it is expedient to vaccinate pregnant women against influenza to reduce the rates of morbidity, hospitalization, and mortality due to influenza infection among both women themselves and neonatal infants.

[Chitosan as an adjuvant for inactivated vaccines against avian influenza viruses].

AIM: To study chitozan as an adjuvant for inactivated vaccines against A/H5 influenza viruses. MATERIALS AND METHODS: Avian A/H5 influenza viruses were grown on chicken embryos or on MDCK cell line; viruses-containing fluid was inactivated with formalin. Mice were vaccinated intramuscularly with inactivated avian influenza virus mixed with chitozan and then levels of hemagglutination-inhibiting and neutralizing antibodies as well as protective efficacy against both homologous and drifted strains of avian influenza viruses A/H5 were measured. RESULTS: Addition of chitozan to inactivated preparations of A/H5 avian influenza viruses for immunization of mice significantly increased levels of hemagglutination-inhibiting and neutralizing antibodies to both homologous and drifted variants of A/H5 influenza viruses, including those containing neuraminidase from other subtype as well as strains isolated 10 - 20 years earlier than virus used for vaccination. Chitozan significantly improved protective efficacy of inactivated avian influenza vaccines against infection with both homologous and drifted variant of the virus. Vaccination with inactivated avian influenza viruses A/H5 and chitozan induced high levels of antibodies even after single immunization as well as after administration of 8-fold reduced dose of preparation. CONCLUSION: Chitozan is a perspective adjuvant for inactivated vaccines against avian influenza viruses, which could significantly improve immune response and protective efficacy against both homologous and drifted variants of avian influenza viruses A/H5.

[Chitosan as an adjuvant for parenteral inactivated influenza vaccines].

Addition of 0.5% chitosan derivative to parenteral inactivated influenza vaccines increased antibody titers in the single immunization of mice by 4-5 times while double immunization showed 6-to-10-fold increases as compared with immunization without chitosan. Moreover, chitosan-containing vaccines induced the generation of antibodies to the drift variants of influenza virus. When the mice were given inactivated influenza virus A/H5N2 vaccine containing chitosan, immunogenicity and protective efficacy were much higher than when they received a vaccine containing no chitosan.

[Influenza pandemic: hypotheses and facts].

Data on influenza pandemics as well as on the characteristics of influenza viruses, which caused pandemicsin 1918, 1957, 1968, and 1977 are presented. Mechanisms of pandemic influenza virus strains evolving, including mutations resulting in increase of virulence, as well as possibility of human and avian influenza viruses reassortment process as the source of pandemic strains are discussed. Mechanisms of transformation of mildly virulent influenza virus strains to highly virulent, which can cause epizootics, are reviewed. Genes and proteins determining species specificity of avian influenza viruses as well as possible emergence of influenza pandemic caused by H5N1 strain are discussed. Suggestion of low probability of such event is expressed.

[Influence of chitosan on immunophenotype and functional activity of murine mononuclear leukocytes after immunization with inactivated influenza vaccine].

In the overwhelming majority of countries inactivated vaccines, which form mainly humoral immunity, are used for prevention of influenza. The objective of the study was to assess the combined effect of inactivated influenza vaccine and chitozan on cellular immunity in CBA line mice. Intramuscular administration of 2 doses (with 4 week interval) of inactivated influenza vaccine and chitozan resulted in increased cytotoxic activity of splenic NK cells against NK-sensitive cell line K562 as well as in increased proliferative activity of mononuclear leukocytes, and numbers of CD3 T-lymphocytes, NKT cells, B-lymphocytes in animals' spleens. Combination of inactivated influenza vaccine with chitozan modulated the number MHC II-expressing cells by eliminating the increased reactivity of immune system cells as well as increased the number of MHC I-expressing cells. This point on the activation of cellular properties, which recognize intracellular pathogens, and thus on activation of both humoral and cellular factors of immune response. It can be proposed that inclusion of chitozan in the vaccine allows to modulate switching of the immune response from Th-2 to Th-1 type.

[Influenza vaccination of children as a general factor in prevention of influenza epidemics].

The data about high morbidity of children influenza and their hospitalization, and principle role of children in speacling of influenza are presented. Total influenza vaccination of children decrease the influenza morbidity and hospitalization of children, and also may be to decrease the influenza morbidity of nonvaccinated population whole during influenza epidemics. Problems of effective vaccination of infants are discussed and data about economic effect of their total vaccination are presented.

[Vaccines and chemicals for the prevention of influenza].

The review gives data on the reactogenicity, immunogenicity, and protective efficacy of the existing influenza vaccines, such as inactivated (conjugate, subunit, virosomal, cultural vaccines with adjuvants) and live vaccines, as well as on the new directions in the design of influenza vaccines. It also provides data on specific medications against influenza and discusses the problem associated with the occurrence of influenza viruses resistantto these drugs. The economic efficiency of the prevention of influenza with vaccines and drugs is under debate.

[Molecular mechanisms of reversions to the ts+ -phenotype of cold-adapted influenza virus A strains--attenuation donors for live influenza reassortant vaccines].

A ts+ revertant of cold-adapted (ca) strain A/Leningrad/134/47/57--the attenuation donor for live influenza reassortant vaccines--was obtained by passages of the ca strain in chick embryos at nonpermissive temperatures. The ts+ revertant acquired the ability to grow in chick embryos at 40 degrees C and lost the capacity to reproduce there at 25 degrees C. A complementation-recombination test using the fowl plague virus (FPV0 ts-mutants showed the loss of the ts-phenotype in the RNA-segments of ts+ revertants' genome coding for PB2, NP, and NS (NS2) proteins. However, PCR-restriction analysis revealed a true reversion in RNA-segment coding for PB2 protein only. All the investigated mutations in the ts+ revertant genome were preserved. This phenomenon could be explained by the appearance of intragenic and extragenic suppression mutations in the ts+ revertant genome. The data of the complementation-recombination test suggest that reversion of ts-phenotype occurs more frequently due to extra- or intragenic suppression rather than as a result of a true mutation loss. Estimation of the genetic stability of vaccine ca strains of influenza virus should be based on the combined use of PCR-restriction and complementation tests.

[Avian flu epizootia and its prevention].

In the review cited the data about avian flu epizootia for last years, about economic damage by epizootia, the information on an infection of people by viruses of animals. Problems the development of vaccines against a avian flu, including ways of designing of vaccine strains are discussed. Data on methods of struggle with avian influenza epizootia of poultry, about methods of prevention the epizootia and uses for this purpose of vaccines and drugs are resulted.

[Prevention of influenza in infants].

The review summarizes recent data on the incidence of influenza and hospital admissions for this disease among infants aged 0 to 2 years. It considers the optimal influenza prevention regimens in the age groups of 0 to 6 months and 6 months to 2 years, by using influenza vaccines for immunization of infants and all those contacting them inside and outside, as well as pregnant women. Whether prophylaxis of influenza A can be made in Russia is also discussed.