Genotyping assay for differentiation of wild-type and vaccine viruses in subjects immunized with live attenuated influenza vaccine.

Live attenuated influenza vaccines (LAIVs) are considered as safe and effective tool to control influenza in different age groups, especially in young children. An important part of the LAIV safety evaluation is the detection of vaccine virus replication in the nasopharynx of the vaccinees, with special attention to a potential virus transmission to the unvaccinated close contacts. Conducting LAIV clinical trials in some geographical regions with year-round circulation of influenza viruses warrants the development of robust and reliable tools for differentiating vaccine viruses from wild-type influenza viruses in nasal pharyngeal wash (NPW) specimens of vaccinated subjects. Here we report the development of genotyping assay for the detection of wild-type and vaccine-type influenza virus genes in NPW specimens of young children immunized with Russian-backbone seasonal trivalent LAIV using Sanger sequencing from newly designed universal primers. The new primer set allowed amplification and sequencing of short fragments of viral genes in NPW specimens and appeared to be more sensitive than conventional real-time RT-PCR protocols routinely used for the detection and typing/subtyping of influenza virus in humans. Furthermore, the new assay is capable of defining the origin of wild-type influenza virus through BLAST search with the generated sequences of viral genes fragments.

Immunogenicity and Cross Protection in Mice Afforded by Pandemic H1N1 Live Attenuated Influenza Vaccine Containing Wild-Type Nucleoprotein.

Since conserved viral proteins of influenza virus, such as nucleoprotein (NP) and matrix 1 protein, are the main targets for virus-specific CD8+ cytotoxic T-lymphocytes (CTLs), we hypothesized that introduction of the NP gene of wild-type virus into the genome of vaccine reassortants could lead to better immunogenicity and afford better protection. This paper describes in vitro and in vivo preclinical studies of two new reassortants of pandemic H1N1 live attenuated influenza vaccine (LAIV) candidates. One had the hemagglutinin (HA) and neuraminidase (NA) genes from A/South Africa/3626/2013 H1N1 wild-type virus on the A/Leningrad/134/17/57 master donor virus backbone (6 : 2 formulation) while the second had the HA, NA, and NP genes of the wild-type virus on the same backbone (5 : 3 formulation). Although both LAIVs induced similar antibody immune responses, the 5 : 3 LAIV provoked greater production of virus-specific CTLs than the 6 : 2 variant. Furthermore, the 5 : 3 LAIV-induced CTLs had higher in vivo cytotoxic activity, compared to 6 : 2 LAIV. Finally, the 5 : 3 LAIV candidate afforded greater protection against infection and severe illness than the 6 : 2 LAIV. Inclusion in LAIV of the NP gene from wild-type influenza virus is a new approach to inducing cross-reactive cell-mediated immune responses and cross protection against pandemic influenza.

Comparative studies of infectivity, immunogenicity and cross-protective efficacy of live attenuated influenza vaccines containing nucleoprotein from cold-adapted or wild-type influenza virus in a mouse model.

This study sought to improve an existing live attenuated influenza vaccine (LAIV) by including nucleoprotein (NP) from wild-type virus rather than master donor virus (MDV). H7N9 LAIV reassortants with 6:2 (NP from MDV) and 5:3 (NP from wild-type virus) genome compositions were compared with regard to their growth characteristics, induction of humoral and cellular immune responses in mice, and ability to protect mice against homologous and heterologous challenge viruses. Although, in general, the 6:2 reassortant induced greater cell-mediated immunity in C57BL6 mice than the 5:3 vaccine, mice immunized with the 5:3 LAIV were better protected against heterologous challenge. The 5:3 LAIV-induced CTLs also had better in vivo killing activity against target cells loaded with the NP366 epitope of recent influenza viruses. Modification of the genome of reassortant vaccine viruses by incorporating the NP gene from wild-type viruses represents a simple strategy to improve the immunogenicity and cross-protection of influenza vaccines.

Discovery of a new class of antiviral compounds: camphor imine derivatives.

A new class of compounds featuring a camphor moiety has been discovered that exhibits potent inhibitory activity against influenza A(H1N1)pdm09 and A(H5N1) viruses. The synthesized compounds were characterized by spectroscopic analysis; in addition the structures of compound 2 and 14 were elucidated by the X-ray diffraction technique. Structure-activity relationship studies have been conducted to identify the 1,7,7-trimethylbicyclo[2.2.1]heptanes2-ylidene group as the key functional group responsible for the observed antiviral activity. The most potent antiviral compound is imine 2 with therapeutic index more than 500.

Camphor-based symmetric diimines as inhibitors of influenza virus reproduction.

Influenza is a continuing world-wide public health problem that causes significant morbidity and mortality during seasonal epidemics and sporadic pandemics. The purpose of the study was synthesis and investigation of antiviral activity of camphor-based symmetric diimines and diamines. A set of C2-symmetric nitrogen-containing camphor derivatives have been synthesized. The antiviral activity of these compounds was studied against rimantadine- and amantadine-resistant influenza virus A/California/7/09 (H1N1)pdm09 in MDCK cells. The highest efficacy in virus inhibiting was shown for compounds 2a-e with cage moieties bound by aliphatic linkers. The therapeutic index (selectivity index) for 2b exceeded that for reference compounds amantadine, deitiforin and rimantadine almost 10-fold. As shown by structure-activity analysis, the length of the linker has a dramatic effect on the toxicity of compounds. Compound 2e with -C12H24- linker exhibited the lowest toxicity (CTD50=2216µM). Derivatives of camphor, therefore, can be considered as prospective antiinfluenza compounds active against influenza viruses resistant to adamantane-based drugs.

New quaternary ammonium camphor derivatives and their antiviral activity, genotoxic effects and cytotoxicity.

The synthesis and biological evaluation of a novel series of dimeric camphor derivatives are described. The resulting compounds were studied for their antiviral activity, cyto- and genotoxicity. Compounds 3a and 3d in which the quaternary nitrogen atoms are separated by the C5H10 and С9H18 aliphatic chain, exhibited the highest efficiency as an agent inhibiting the reproduction of the influenza virus A(H1N1)pdm09. The cytotoxicity data of compounds 3 and 4 revealed their moderate activity against malignant cell lines; compound 3f had the highest activity for the CEM-13 cells. These results show close agreement with the data of independent studies on toxicity of these compounds, in particular that the toxicity of compounds strongly depends on spacer length.