Pigs immunized with a novel E2 subunit vaccine are protected from subgenotype heterologous classical swine fever virus challenge.
BACKGROUND
Classical swine fever (CSF) or hog cholera is a highly contagious swine viral disease. CSF endemic countries have to use routine vaccination with modified live virus (MLV) vaccines to prevent and control CSF. However, it is impossible to serologically differentiate MLV vaccinated pigs from those infected with CSF virus (CSFV). The aim of this study is to develop a one-dose E2-subunit vaccine that can provide protection against CSFV challenge. We hypothesize that a vaccine consisting of a suitable adjuvant and recombinant E2 with natural conformation may induce a similar level of protection as the MLV vaccine.


RESULTS
Our experimental vaccine KNB-E2 was formulated with the recombinant E2 protein (Genotype 1.1) expressed by insect cells and an oil-in-water emulsion based adjuvant. 10 pigs (3 weeks old, 5 pigs/group) were immunized intramuscularly with one dose or two doses (3 weeks apart) KNB-E2, and 10 more control pigs were administered normal saline solution only. Two weeks after the second vaccination, all KNB-E2 vaccinated pigs and 5 control pigs were challenged with 5 × 10(5) TCID50 CSFV Honduras/1997 (Genotype 1.3, 1 ml intramuscular, 1 ml intranasal). It was found that while control pigs infected with CSFV stopped growing and developed high fever (>40 °C), high level CSFV load in blood and nasal fluid, and severe leukopenia 3-14 days post challenge, all KNB-E2 vaccinated pigs continued to grow as control pigs without CSFV exposure, did not show any fever, had low or undetectable level of CSFV in blood and nasal fluid. At the time of CSFV challenge, only pigs immunized with KNB-E2 developed high levels of E2-specific antibodies and anti-CSFV neutralizing antibodies.


CONCLUSIONS
Our studies provide direct evidence that pigs immunized with one dose KNB-E2 can be protected clinically from CSFV challenge. This protection is likely mediated by high levels of E2-specific and anti-CSFV neutralizing antibodies.
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.
Rachel
R
Madera
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.|Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, China.
Wenjie
W
Gong
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.
Lihua
L
Wang
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.|Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506, USA.
Yulia
Y
Burakova
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.
Karen
K
Lleellish
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA.
Amy
A
Galliher-Beckley
Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS, 66506, USA.
Jerome
J
Nietfeld
Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS, 66506, USA.
Jamie
J
Henningson
Department of Chemistry, Kansas State University, Manhattan, KS, 66506, USA.
Kaimin
K
Jia
Department of Chemistry, Kansas State University, Manhattan, KS, 66506, USA.
Ping
P
Li
Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS, 66506, USA.
Jianfa
J
Bai
Department of Chemical Engineering, Kansas State University, Manhattan, KS, 66506, USA.
John
J
Schlup
United States Department of Agriculture, Agricultural Research Service, Arthropod Borne Animal Disease Research Unit, Manhattan, KS, 66502, USA.
Scott
S
McVey
Institute of Military Veterinary Medicine, Academy of Military Medical Sciences, Changchun, China. changchun_tu@hotmail.com.
Changchun
C
Tu
Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA. jshi@vet.k-state.edu.
Jishu
http://orcid.org/0000-0002-7177-9280
J
Shi
D000818:Animals; D006691:Classical Swine Fever / Q000517:prevention & control* / Q000821:virology; D006692:Classical Swine Fever Virus / Q000235:genetics*; D005838:Genotype; D007115:Immunization Schedule; D013552:Swine; D014614:Vaccines, Synthetic; D014765:Viral Vaccines / Q000276:immunology*; D014779:Virus Replication
D014614:Vaccines, Synthetic; D014765:Viral Vaccines
Adjuvant; CSF; CSFV; Classical swine fever; E2; KNB-E2; Vaccine