Enhancing DNA vaccine potency against hantavirus by co-administration of interleukin-12 expression vector as a genetic adjuvant.
BACKGROUND
The heavy incidence and mortality of hemorrhagic fever with renal syndrome, as well as no specific drugs in curing the disease, clearly indicate the need for development of the more effective hantavirus vaccine. Refining the DNA vaccination strategy to elicit more clinically efficacious immune responses is now under intensive investigation. In the present study, we examined the effects of using an interleukin-12 expression plasmid as a genetic adjuvant to enhance the immune responses induced by a DNA vaccine based on the S gene encoding nucleocapsid protein against hantavirus.


METHODS
BALB/c mice were immunized three times by intramuscular inoculations of DNA vaccine encoding of hantanvirus nucleocapsid protein alone or in combination with a plasmid expressing murine interleukin-12 (pcIL-12). Booster immunizations were employed 2 times at 2-week interval. To evaluate the humoral and cellular immune responses, antigen-specific lymphocyte proliferation and antibody production were assayed by MTT method and ELISA respectively. The level of interleukin-4 and interferon-gamma in the splenic lymphocytic cultured supernatant were detected with ELISA kit at day 5, 10, 17, 35 and 42 after primary immunization.


RESULTS
Antigen-specific IgG antibodies was increased markedly at day 17 in the experiment groups and reached a plateau after day 35. As pcIL-12 co-injected, a significant inhibition of antigen-specific IgG levels was displayed over the period and the antibody mean titre was decreased to only about 1:50 at day 42 after primary immunization, significantly lower than the group immunized with pcDNA3.1 + S alone, in which the mean titre was about 1:70. Interferon-gamma was increased remarkably by the co-injection of pcIL-12 compared with the injection of pcDNA3.1 + S alone. However, the production of interleukin-4 was inhibited by pcIL-12 co-injection. Furthermore, pcIL-12 co-injection efficiently enhanced antigen-specific lymphocyte proliferation.


CONCLUSIONS
Humoral and cytokine responses elicited by pcDNA3.1 + S inoculation can be modulated by co-inoculation with pcIL-12 and efficiently induced Th1-dominant immune responses.
Zheng
Lan-yan
LY
Department of Microbiology and Parasitology, China Medical University, Shenyang 110001, China.
Mou
Ling
L
Lin
Song
S
Lu
Run-ming
RM
Luo
En-jie
EJ
D000818:Animals; D016207:Cytokines / Q000096:biosynthesis; D015316:Genetic Therapy; D006476:Orthohantavirus / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood; D016130:Immunophenotyping; D018664:Interleukin-12 / Q000235:genetics*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019251:Nucleocapsid / Q000235:genetics / Q000276:immunology*; D019444:Vaccines, DNA / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
D016207:Cytokines; D007074:Immunoglobulin G; D019444:Vaccines, DNA; D014765:Viral Vaccines; D018664:Interleukin-12