Abstract
BackgroundOur previous studies showed that Trichinella spiralis paramyosin (TsPmy) is an immunomodulatory protein that inhibits complement C1q and C8/C9 to evade host complement attack. Vaccination with recombinant TsPmy protein induced protective immunity against T. spiralis larval challenge. Due to the difficulty in producing TsPmy as a soluble recombinant protein, we prepared a DNA vaccine as an alternative approach in order to elicit a robust immunity against Trichinella infection.Methods and FindingsThe full-length TsPmy coding DNA was cloned into the eukaryotic expression plasmid pVAX1, and the recombinant pVAX1/TsPmy was transformed into attenuated Salmonella typhimurium strain SL7207. Oral vaccination of mice with this attenuated Salmonella-delivered TsPmy DNA vaccine elicited a significant mucosal sIgA response in the intestine and a systemic IgG antibody response with IgG2a as the predominant subclass. Cytokine analysis also showed a significant increase in the Th1 (IFN-γ, IL-2) and Th2 (IL-4, 5, 6, 10) responses in lymphocytes from the spleen and MLNs of immunized mice upon stimulation with TsPmy protein. The expression of the homing receptors CCR9/CCR10 on antibody secreting B cells may be related to the translocation of IgA-secreted B cells to local intestinal mucosa. The mice immunized with Salmonella-delivered TsPmy DNA vaccine produced a significant 44.8% reduction in adult worm and a 46.6% reduction in muscle larvae after challenge with T. spiralis larvae.ConclusionOur results demonstrated that oral vaccination with TsPmy DNA delivered by live attenuated S. typhimurium elicited a significant local IgA response and a mixed Th1/Th2 immune response that elicited a significant protection against T. spiralis infection in mice.
Highlights
Trichinellosis, a serious food-borne parasitic zoonosis and an important public health problem worldwide, is mainly caused by infection with the tissue-dwelling nematode Trichinella spiralis [1, 2]
Our results demonstrated that oral vaccination with Trichinella spiralis paramyosin (TsPmy) DNA delivered by live attenuated S. typhimurium elicited a significant local IgA response and a mixed Th1/Th2 immune response that elicited a significant protection against T. spiralis infection in mice
Transcription of TsPmy mRNA and recombinant TsPmy expression in vivo Total RNAs were isolated from the mesenteric lymph nodes (MLNs), liver and spleen tissues of mice one week after the first immunization for reverse transcription polymerase chain reaction (RT-PCR) to determine the transcription of TsPmy in these tissues
Summary
Trichinellosis, a serious food-borne parasitic zoonosis and an important public health problem worldwide, is mainly caused by infection with the tissue-dwelling nematode Trichinella spiralis [1, 2]. People develop this infection through ingestion of raw or undercooked meat contaminated with encapsulated parasite larva. Domestic pork has been the major source of this infection in China and other countries. Vaccination with recombinant TsPmy protein induced protective immunity against T. spiralis larval challenge. Due to the difficulty in producing TsPmy as a soluble recombinant protein, we prepared a DNA vaccine as an alternative approach in order to elicit a robust immunity against Trichinella infection
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