Characterization and evaluation of a Sarcoptes scabiei allergen as a candidate vaccine.
BACKGROUND
Sarcoptic mange caused by the mite Sarcoptes scabiei is a worldwide disease affecting both humans and animals. Here we report the molecular characterization and evaluation of a recombinant S. scabiei tropomyosin (SsTm) protein in a vaccination trial in rabbits.


METHODS
The full-length cDNA was cloned in a bacterial pET vector, and the recombinant protein was expressed in BL21 (DE3) cells and purified. Using specific rabbit antiserum, tropomyosin was localized immunohistochemically in mite tissue sections. Vaccination trials with the recombiant SsTm was carried out in New Zealand rabbits.


RESULTS
The full-length open reading frame (ORF) of the 852 bp cloned gene from S. scabiei encodes a 32.9 kDa protein. The amino acid sequence showed 98.94%, 97.89% and 98.59% homology to Dermatophagoides farina and Dermatophagoides pteronyssinus group 10 allergens and Psoroptes ovis tropomyosin, respectively. Tropomyosin was localized immunohistochemically in mite tissue sections mainly in the mouthparts, legs and integument of the epidermis. The predicted cross-reactivity of SsTm indicated that it is an allergenic protein. While vaccination with the recombiant SsTm resulted in high levels of specific IgG (P < 0.01), a low IgE antibody response and no significant protection against S. scabiei challenge were observed. After challenge, specific IgG levels remained significantly higher than the control (P < 0.01), while changes of total IgE levels were not significant (P > 0.05). However, the lesion areas in the vaccination group decreased at the end of the experiment compared with controls.


CONCLUSIONS
Although vaccination with recombinant SsTm did not efficiently control sarcoptic mange in rabbits, the immunogenic properties of tropomyosin suggest it may be developed as a vaccine with alternative adjuvants or delivery methods.
Department of Parasitology, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, China.
Runhui
R
Zhang
Quwu
Q
Jise
Wanpeng
W
Zheng
Yongjun
Y
Ren
Xiang
X
Nong
Xuhang
X
Wu
Xiaobin
X
Gu
Shuxian
S
Wang
Xuerong
X
Peng
Songjia
S
Lai
Guangyou
G
Yang
D000485:Allergens / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology; D007814:Larva; D008969:Molecular Sequence Data; D009758:Nymph; D010802:Phylogeny; D011817:Rabbits; D012520:Sarcoptes scabiei / Q000276:immunology*; D012532:Scabies / Q000517:prevention & control / Q000662:veterinary*; D014335:Tropomyosin / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D014612:Vaccines / Q000276:immunology*
D000485:Allergens; D014335:Tropomyosin; D014612:Vaccines