Vaccination with recombinant Ascaris suum 24-kilodalton antigen induces a Th1/Th2-mixed type immune response and confers high levels of protection against challenged Ascaris suum lung-stage infection in BALB/c mice.
Previous studies have shown that antigens from various life-cycle stages of Ascaris suum can induce host-protective immunity against challenge infections with infective eggs of A. suum. This study evaluated whether Escherichia coli-expressed recombinant 24-kDa antigen from A. suum (rAs24) was a suitable vaccine candidate for the control of Ascaris infections by examining its performance in a mouse model. Immunization of BALB/c mice in three consecutive doses with rAs24 in Freund's Complete Adjuvant (FCA) results in protection against challenge infections as manifested by a 58% reduction (P<0.001) in recovery and stunted development of A. suum lung-stage larvae at day 7 post-challenge. Sera obtained from immune protected mice had a significantly increased level of immunoglobulin G (IgG) (P<0.0001) but had no IgE response. Analysis of IgG-subclass profiles revealed that IgG1 (P<0.0001) showed the greatest increase followed by IgG2b (P<0.005), IgG2a (P<0.006) and IgG3 (P<0.04). Splenic T cells from rAs24-FCA immunized mice secreted significantly high levels of both Th1 cytokine gamma-interferon (P<0.005) and Th2 cytokine interleukin-10 (P<0.001) after stimulation with rAs24 in vitro. Interestingly, affinity purified anti-rAs24 IgG was shown to inhibit moulting of A. suum lung-stage L3 to L4 in vitro by 26%, indicating an in vivo function of the endogenous As24 in the moulting processes. An intense expression of endogenous As24 in the hypodermis and gut epithelium of A. suum lung-stage L3 by immunofluorescence supports a function for endogenous As24. These findings may contribute to the understanding of rAs24-induced Th1/Th2-mediated effector mechanisms required for the protection of A. suum lung-stage larval infection.
Laboratory of Parasitic Diseases, National Institute of Animal Health, National Agricultural Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan.
M Khyrul
MK
Islam
Takeharu
T
Miyoshi
Naotoshi
N
Tsuji
D000818:Animals; D000909:Antibodies, Helminth / Q000096:biosynthesis; D000947:Antigens, Helminth / Q000276:immunology*; D001196:Ascariasis / Q000276:immunology / Q000517:prevention & control*; D017165:Ascaris suum / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D007074:Immunoglobulin G / Q000096:biosynthesis; D008174:Lung Diseases, Parasitic / Q000276:immunology / Q000517:prevention & control*; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology; D018418:Th2 Cells / Q000276:immunology; D014611:Vaccination; D014614:Vaccines, Synthetic / Q000276:immunology
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D016207:Cytokines; D007074:Immunoglobulin G; D014614:Vaccines, Synthetic