Larisa Rudenko

Immunogenicity and efficacy of Russian live attenuated and US inactivated influenza vaccines used alone and in combination in nursing home residents

The immunogenicity and efficacy of Russian live attenuated and US inactivated trivalent influenza vaccines administered alone or in three different combinations were evaluated in a randomized, placebo-controlled, double-blinded study of 614 elderly or chronically ill nursing home residents in St. Petersburg, Russia during the 1996-97 influenza season. Postvaccination serum antibody responses were more frequent among individuals administered the combination vaccines than among those vaccinated with live or inactivated vaccine alone. Only individuals who received live vaccine, alone or in combination with inactivated vaccine, achieved significant postvaccination increases in virus-specific nasal IgA. Efficacy in preventing laboratory-confirmed influenza in vaccinated versus nonvaccinated individuals was 67% (95%CI, 36-81%) for recipients of a combination of the vaccines compared with 51% (95%CI, -17-79%) for recipients of live vaccine alone and 50% (95%CI, -26-80%) for recipients of inactivated vaccine alone. These results suggest that administration of a combination of influenza vaccines may provide a strategy for improved influenza vaccination of elderly people.

Live attenuated pandemic influenza vaccine: Clinical studies on A/17/California/2009/38 (H1N1) and licensing of the Russian-developed technology to WHO for pandemic influenza preparedness in developing countries

In February 2009, Nobilon granted the World Health Organization (WHO) a non-exclusive licence to develop, register, manufacture, use and sell seasonal a pandemic live attenuated influenza vaccine (LAIV) produced on embryonated chicken eggs. WHO was permitted to grant sub-licences to vaccine manufacturers in developing countries within the framework of its influenza vaccine technology transfer initiative. In parallel, the Institute of Experimental Medicine (IEM), Russia, concluded an agreement with WHO for the supply of Russian LAIV reassortants for use by these manufacturers. Also in 2009, IEM carried out a study on a novel A/17/California/2009/38 (H1N1) pandemic LAIV candidate derived from the pandemic-related A/California/07/2009 (H1N1) influenza virus and the attenuated A/Leningrad/134/17/57 (H2N2) master donor virus, using routine reassortant technique in embryonated chicken eggs. Following successful preclinical studies in eggs and in ferrets, a double-blind, controlled, randomized clinical trial was carried out in immunologically naïve study participants between 12-18 and 18-60 years old. Collectively, the immunogenicity data (haemagglutinin inhibition test, ELISA and cytokine tests for the detection of memory T cells) support the use of a single dose of the pandemic H1N1 LAIV in 12-60 year olds. The outcome of the studies showed no significant adverse reactions attributable to the vaccine, and suggests that the vaccine is as safe and immunogenic as seasonal influenza vaccines. Importantly, it was clearly demonstrated that reliance on the HAI assay alone is not recommended for testing LAIV. To date, via the licence agreement with WHO, the H1N1 LAIV has been transferred to the Government Pharmaceutical Organization in Thailand, the Serum Institute of India, and the Zhejiang Tianyuan Bio-Pharmaceutical Co., Ltd. in China.

Genetic bases of the temperature-sensitive phenotype of a master donor virus used in live attenuated influenza vaccines: A/Leningrad/134/17/57 (H2N2).

Trivalent live attenuated influenza vaccines whose type A components are based on cold-adapted A/Leningrad/134/17/57 (H2N2) (caLen17) master donor virus (MDV) have been successfully used in Russia for decades to control influenza. The vaccine virus comprises hemagglutinin and neuraminidase genes from the circulating viruses and the remaining six genes from the MDV. The latter confer temperature-sensitive (ts) and attenuated (att) phenotypes. The ts phenotype of the vaccine virus is a critical biological determinant of attenuation of virulence. We developed a plasmid-based reverse genetics system for MDV caLen17 to study the genetic basis of its ts phenotype. Mutations in the polymerase proteins PB1 and PB2 played a crucial role in the ts phenotype of MDV caLen17. In addition, we show that caLen17-specific ts mutations could impart the ts phenotype to the divergent PR8 virus, suggesting the feasibility of transferring the ts phenotype to new viruses of interest for vaccine development.

Assessment of Human Immune Responses to H7 Avian Influenza Virus of Pandemic Potential: Results from a Placebo–Controlled, Randomized Double–Blind Phase I Study of Live Attenuated H7N3 Influenza Vaccine

Introduction Live attenuated influenza vaccines (LAIVs) are being developed to protect humans against future epidemics and pandemics. This study describes the results of a double–blinded randomized placebo–controlled phase I clinical trial of cold–adapted and temperature sensitive H7N3 live attenuated influenza vaccine candidate in healthy seronegative adults. Objective The goal of the study was to evaluate the safety, tolerability, immunogenicity and potential shedding and transmission of H7N3 LAIV against H7 avian influenza virus of pandemic potential. Methods and Findings Two doses of H7N3 LAIV or placebo were administered to 40 randomly divided subjects (30 received vaccine and 10 placebo). The presence of influenza A virus RNA in nasal swabs was detected in 60.0% and 51.7% of subjects after the first and second vaccination, respectively. In addition, vaccine virus was not detected among placebo recipients demonstrating the absence of person–to–person transmission. The H7N3 live attenuated influenza vaccine demonstrated a good safety profile and was well tolerated. The two–dose immunization resulted in measurable serum and local antibody production and in generation of antigen–specific CD4+ and CD8+ memory T cells. Composite analysis of the immune response which included hemagglutinin inhibition assay, microneutralization tests, and measures of IgG and IgA and virus–specific T cells showed that the majority (86.2%) of vaccine recipients developed serum and/or local antibodies responses and generated CD4+ and CD8+ memory T cells. Conclusions The H7N3 LAIV was safe and well tolerated, immunogenic in healthy seronegative adults and elicited production of antibodies broadly reactive against the newly emerged H7N9 avian influenza virus. Trial registration ClinicalTrials.gov NCT01511419

Safety and immunogenicity of live attenuated influenza reassortant H5 vaccine (phase I-II clinical trials).

Objective  Our studies aimed to evaluate in clinical trials the safety and immunogenicity of an H5 live influenza vaccine candidate obtained using classical reassortment techniques from a low pathogenicity avian influenza (LPAI) A/Duck/Potsdam/1402‐6/86(H5N2) virus and the cold‐adapted (ca) donor strain A/Leningrad/134/17/57(H2N2).

Comparative Study of Influenza Virus Replication in MDCK Cells and in Primary Cells Derived from Adenoids and Airway Epithelium

ABSTRACT Although clinical trials with human subjects are essential for determination of safety, infectivity, and immunogenicity, it is desirable to know in advance the infectiousness of potential candidate live attenuated influenza vaccine strains for human use. We compared the replication kinetics of wild-type and live attenuated influenza viruses, including H1N1, H3N2, H9N2, and B strains, in Madin-Darby canine kidney (MDCK) cells, primary epithelial cells derived from human adenoids, and human bronchial epithelium (NHBE cells). Our data showed that despite the fact that all tissue culture models lack a functional adaptive immune system, differentiated cultures of human epithelium exhibited the greatest restriction for all H1N1, H3N2, and B vaccine viruses studied among three cell types tested and the best correlation with their levels of attenuation seen in clinical trials with humans. In contrast, the data obtained with MDCK cells were the least predictive of restricted viral replication of live attenuated vaccine viruses in humans. We were able to detect a statistically significant difference between the replication abilities of the U.S. (A/Ann Arbor/6/60) and Russian (A/Leningrad/134/17/57) cold-adapted vaccine donor strains in NHBE cultures. Since live attenuated pandemic influenza vaccines may potentially express a hemagglutinin and neuraminidase from a non-human influenza virus, we assessed which of the three cell cultures could be used to optimally evaluate the infectivity and cellular tropism of viruses derived from different hosts. Among the three cell types tested, NHBE cultures most adequately reflected the infectivity and cellular tropism of influenza virus strains with different receptor specificities. NHBE cultures could be considered for use as a screening step for evaluating the restricted replication of influenza vaccine candidates.

Genetic stability of cold-adapted A/Leningrad/134/47/57 (H2N2) influenza virus: sequence analysis of live cold-adapted reassortant vaccine strains before and after replication in children

We previously reported that the A/Leningrad/134/47/57 (H2N2) cold-adapted virus (A/Len/47) used in preparing reassortant live attenuated vaccines for children acquired 14 (11 coding) mutations in genes coding for proteins other than haemagglutinin and neuraminidase during cold-adaptation. Preservation of these mutations in genomes of viruses isolated from children on the second, fifth, or eighth day after vaccination was examined by sequence analysis. The sequence data demonstrated that all nine coding mutations selected for examination were conserved in the genomes of all 11 strains investigated, indicating that the mutations accompanying cold-adaptation and attenuation of the A/Len/47 master vaccine are highly stable.

H7N3 live attenuated influenza vaccine has a potential to protect against new H7N9 avian influenza virus

After recent emergence of new avian influenza A(H7N9) viruses in humans many people and Governments are asking about H7 influenza vaccine which could provide cross-protection against new viruses, until H7N9 vaccine is prepared from a relevant strain. Here we scientifically justify that available H7N3 live attenuated influenza vaccine (LAIV) can be protective against H7N9 viruses due to the presence of conserved immune epitopes in its hemagglutinin. We used Immune Epitope Database analysis resource to predict B-cell and CTL epitopes distributed across H7N3 HA molecule and assessed their identity with new H7N9 viruses at near 70% and 60% of the epitopes, respectively. In addition, we tested serum samples of volunteers participated in phase I clinical trial of H7N3 LAIV for the presence of anti-H7N9 hemagglutination-inhibition and neutralizing antibodies and found seroconversions in 44.8% of vaccinated persons, which suggests the potential of H7N3 LAIV to protect against new H7N9 avian influenza viruses.

Memory T-Cell Immune Response in Healthy Young Adults Vaccinated with Live Attenuated Influenza A (H5N2) Vaccine

ABSTRACT Cellular immune responses of both CD4 and CD8 memory/effector T cells were evaluated in healthy young adults who received two doses of live attenuated influenza A (H5N2) vaccine. The vaccine was developed by reassortment of nonpathogenic avian A/Duck/Potsdam/1402-6/68 (H5N2) and cold-adapted A/Leningrad/134/17/57 (H2N2) viruses. T-cell responses were measured by standard methods of intracellular cytokine staining of gamma interferon (IFN-γ)-producing cells and a novel T-cell recognition of antigen-presenting cells by protein capture (TRAP) assay based on the trogocytosis phenomenon, namely, plasma membrane exchange between interacting immune cells. TRAP enables the detection of activated trogocytosis-positive T cells after virus stimulation. We showed that two doses of live attenuated influenza A (H5N2) vaccine promoted both CD4 and CD8 T-memory-cell responses in peripheral blood of healthy young subjects in the clinical study. Significant differences in geometric mean titers (GMTs) of influenza A (H5N2)-specific IFN-γ+ cells were observed at day 42 following the second vaccination, while peak levels of trogocytosis+ T cells were detected earlier, on the 21st day after the second vaccination. The inverse correlation of baseline levels compared to postvaccine fold changes in GMTs of influenza-specific CD4 and CD8 T cells demonstrated that baseline levels of these specific cells could be considered a predictive factor of vaccine immunogenicity.

Pandemic preparedness with live attenuated influenza vaccines based on A/Leningrad/134/17/57 master donor virus

Continuously evolving avian influenza viruses pose a constant threat to the human public health. In response to this threat, a number of pandemic vaccine candidates have been prepared and evaluated in animal models and clinical trials. This review summarizes the data from the development and preclinical and clinical evaluation of pandemic live attenuated influenza vaccines (LAIV) based on Russian master donor virus A/Leningrad/134/17/57. LAIV candidates of H5N1, H5N2, H7N3, H1N1 and H2N2 subtypes were safe, immunogenic and protected animals from challenge with homologous and heterologous viruses. Clinical trials of the pandemic LAIVs demonstrated their safety and immunogenicity for healthy adult volunteers. The vaccine viruses were infectious, genetically stable and did not transmit to unvaccinated contacts. In addition, here we discuss criteria for the assessment of pandemic LAIV immunogenicity and efficacy necessary for their licensure.