Molecular Basis of Live-Attenuated Influenza Virus
Citation: He W, Wang W, Han H, Wang L, Zhang G, et al. (
Molecular Basis of Live-Attenuated Influenza Virus
Wen He 0
Wei Wang 0
Huamin Han 0
Lei Wang 0
Ge Zhang 0
Bin Gao 0
Paulo Lee Ho, Instituto Butantan, Brazil
0 1 CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences , Beijing , PR China , 2 Hebei Key Laboratory of Medical Biotechnology , Shijiazhuang , PR China , 3 Graduate University of Chinese Academy of Sciences , Beijing, PR China, 4 China- Japan Joint Laboratory of Molecular Immunology and Microbiology, Institute of Microbiology, Chinese Academy of Sciences , Beijing , PR China , 5 School of Life Sciences, University of Science and Technology of China , Hefei , China
Human influenza is a seasonal disease associated with significant morbidity and mortality. The most effective means for controlling infection and thereby reducing morbidity and mortality is vaccination with a three inactivated influenza virus strains mixture, or by intranasal administration of a group of three different live attenuated influenza vaccine strains. Comparing to the inactivated vaccine, the attenuated live viruses allow better elicitation of a long-lasting and broader immune (humoral and cellular) response that represents a naturally occurring transient infection. The cold-adapted (ca) influenza A/AA/6/60 (H2N2) (AA ca) virus is the backbone for the live attenuated trivalent seasonal influenza vaccine licensed in the United States. Similarly, the influenza A components of live-attenuated vaccines used in Russia have been prepared as reassortants of the cold-adapted (ca) H2N2 viruses, A/Leningrad/134/17/57-ca (Len/17) and A/Leningrad/134/ 47/57-ca (Len/47) along with virulent epidemic strains. However, the mechanism of temperature-sensitive attenuation is largely elusive. To understand how modification at genetic level of influenza virus would result in attenuation of human influenza virus A/PR/8/34 (H1N1,A/PR8), we investigated the involvement of key mutations in the PB1 and/or PB2 genes in attenuation of influenza virus in vitro and in vivo. We have demonstrated that a few of residues in PB1 and PB2 are critical for the phenotypes of live attenuated, temperature sensitive influenza viruses by minigenome assay and real-time PCR. The information of these mutation loci could be used for elucidation of mechanism of temperature-sensitive attenuation and as a new strategy for influenza vaccine development.
-
Funding: This work was supported by National Science and Technology Major Project (grant No. 2008ZX10003-012), National Natural Science Foundation of
China (NSFC, grant No. 81021003), National Science and Technology Major Project (grant No. 2009ZX 1004-305 ) and NSFC (grant No. 31070783). The funders had
no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
Influenza A viruses belong to Orthomyxoviridae family viruses and
are highly contagious pathogens for both human and animals. As a
major cause for winter respiratory infection, seasonal influenza
contributes the biggest number of morbidity and mortality each
year. Annual epidemics results in about three to five million cases
of severe illness and about 250,000500,000 deaths worldwide [1].
Vaccination is the primary strategy for the prevention and
control of influenza. Two different types of vaccines, inactivated
and live attenuated viruses are currently licensed for the
prevention of seasonal influenza [2,3,4,5]. The trivalent
inactivated influenza virus vaccine (TIV) has been used since 1945. Each
dose is formulated to contain three viruses (or their HA proteins)
representing the influenza A H3N2, influenza A H1N1, and
influenza B strains chosen to be the most likely strains to circulate
in the upcoming influenza season [6]. Three components are
updated annually as needed on the basis of national and
international recommendations [7,8,9].
Reassortants of cold-adapted (ca) influenza donor strains have
been used as live -attenuated vaccines for direct administration to
the respiratory tract. In USA, influenza A vaccines have been
derived from a cold-adapted influenza donor strain originally
prepared by serial passage of the H2N2 virus Ann Arbor/6/60
(A/AA/6/60) 32 times in chicken kidney cultures at successively
lower temperatures to 25uC to produce a cold-adapted donor
strain A/AA/6/60-ca [10]. The AA ca virus displays important
phenotypes that have been crucial to the development of the virus
for clinical use. The virus replicates efficiently at 25uC and 33uC
but does not replicate well at temperatures above 39uC; these
phenotypic traits have respectively been designated cold-adapted
(ca) and temperature-sensitive (ts) phenotypes. In addition, the AA
ca virus is attenuated in vivo (att phenotype) and is restricted in
replication in the respiratory tract of mice a (...truncated)