Characterization of an Isotype-Dependent Monoclonal Antibody against Linear Neutralizing Epitope Effective for Prophylaxis of Enterovirus 71 Infection
et al. (2012) Characterization of an Isotype-Dependent Monoclonal Antibody against Linear Neutralizing
Epitope Effective for Prophylaxis of Enterovirus 71 Infection. PLoS ONE 7(1): e29751. doi:10.1371/journal.pone.0029751
Characterization of an Isotype-Dependent Monoclonal Antibody against Linear Neutralizing Epitope Effective for Prophylaxis of Enterovirus 71 Infection
Xiao Fang Lim 0
Qiang Jia 0
Wei Xin Khong 0
Benedict Yan 0
Balraj Premanand 0
Sylvie Alonso 0
Vincent T. K. Chow 0
Jimmy Kwang 0
Esper Georges Kallas, University of Sao Paulo, Brazil
0 1 Animal Health Biotechnology, Temasek Life Sciences Laboratory, Singapore, 2 Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 3 Immunology Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 4 Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, 5 Department of Pathology, National University Health System , Singapore
Background: Enterovirus 71 (EV71) is the main causative agent of Hand, Foot and Mouth disease (HFMD) and is associated with severe neurologic complications and mortalities. At present, there is no vaccine or therapeutic available for treatment. Methodology/Principal Finding: In this study, we generated two mAbs, denoted as mAb 51 and 53, both targeting the same linear epitope on VP1 capsid protein, spanning amino acids 215-219. In comparison, mAb 51 belonging to isotype IgM possesses neutralizing activity in vitro, whereas, mAb 53 belonging to isotype IgG1 does not have any neutralizing ability, even towards its homologous strain. When mAb 51 at 10 mg/g of body weight was administered to the 2-week-old AG129 mice one day prior to lethal challenge, 100% in vivo passive protection was observed. In contrast, the isotype control group mice, injected with an irrelevant IgM antibody before the challenge, developed limb paralysis as early as day 6 postinfection. Histological examination demonstrated that mAb 51 was able to protect against pathologic changes such as neuropil vacuolation and neuronal loss in the spinal cord, which were typical in unprotected EV-71 infected mice. BLAST analyses of that epitope revealed that it was highly conserved among all EV71 strains, but not coxsachievirus 16 (CA16). Conclusion: We have defined a linear epitope within the VP1 protein and demonstrated its neutralizing ability to be isotype dependent. The neutralizing property and highly conserved sequence potentiated the application of mAb 51 and 53 for protection against EV71 infection and diagnosis respectively.
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Funding: This project is funded by Temasek Life Sciences Laboratory (http://www.tll.org.sg/), Singapore. 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.
. These authors contributed equally to this work.
Enterovirus 71 or EV71 (BrCr strain) was first isolated and
identified in the United States in 1969 [1] , and was not associated
with hand, foot mouth disease (HFMD) until 1973, when small
epidemics broke out in Japan and Sweden [2,3]. From then on,
successive waves of EV71 outbreaks have been reported globally,
in United Kingdom, Australia, Sweden, Bulgaria, Japan, China,
Hong Kong, Taiwan, Malaysia and Singapore [2,4,5,6,7,8,9,10].
Over the past decade, the Asia-Pacific region was considered the
most seriously affected area, with occurrence of both major and
small-scale outbreaks associated with mortalities and neurologic
complications such as aseptic meningitis, fatal encephalitis and
poliomyelitis-like paralysis [11]. In the 1998 outbreak in Taiwan,
EV71 infected thousands of children and resulted in 405 severe
cases of neurologic disease, and 78 deaths in children [10,12].
HFMD had also emerged in China since 2008, resulting in
approximately 3.4 million of accumulated cases with 1400
fatalities [13]. Thus, EV71 represented a pre-eminent neurotropic
virus ever since the almost complete eradication of poliomyelitis.
Typical of a member of the family Picornaviridae, EV71 is a small,
non-enveloped, positive-stranded RNA virus, comprising four
capsid proteins VP1, VP2, VP3 and VP4. These capsid proteins
form the icosahedral structure, with VP13 exposed on the virus
surface and VP4 arranged internally [14]. Among these capsid
proteins, VP1 is believed to be the major contributor in viral
pathogenesis, playing critical roles in the adsorption and uncoating
processes of virus infection [15]. In addition, VP1 protein also
contains important neutralization sites. Studies utilizing high-titer
human neutralizing antibodies from cord blood samples collected
in Sarawak in 1999 demonstrated that these neutralizing
antibodies were more reactive towards the N-terminal half of
VP1 protein [16]. In contrast, another study revealed linear
neutralizing epitopes on VP (...truncated)