# Heterologous prime-boost immunization based on a human adenovirus 5 vectored containing Trichinella spiralis Cystatin-like protein elicits protective mucosal immunity in mice

## TL;DR

A new vaccine strategy using an adenovirus vector and a protein from Trichinella spiralis boosts mucosal immunity and protects mice from parasitic infection.

## Contribution

A heterologous prime-boost regimen using rAd5TsCLP and rTsCLP induces strong mucosal and systemic immunity against Trichinella.

## Key findings

- The vaccine regimen reduced adult worm and muscle larvae burdens by 61.17% and 58.22%, respectively.
- It induced high levels of IgG, IgG1, IgG2a, IgM, and secretory IgA, along with Th1/Th2 cytokine responses.
- Mucosal immunity was enhanced through increased histamine and goblet cell proliferation in the intestine.

## Abstract

Trichinellosis is a globally distributed zoonotic parasitic disease. The Trichinella infective larvae migrate through the intestine after ingestion and settle in muscles, thus intestinal mucosal immunity plays a vital role against early infection with Trichinella. In this study, a recombinant adenovirus vector expressing the cysteine protease inhibitor of Trichinella spiralis (rAd5TsCLP) was constructed and combined with the recombinant protein rTsCLP in a heterologous prime-boost regimen. The regimen elicits strong, specific, and neutralizing antibodies in BALB/c mice, significantly enhancing cellular immunity through Th1 (IFN-γ, TNF-α) and Th2 (IL-13, IL-4) cytokine production in the peripheral blood, spleen, and cervical lymph nodes, driven by the activation of CD4+ and CD8+ T-cells. Notably, immunization with rAd5TsCLP:rTsCLP elevated mucosal secretory IgA (sIgA) levels, boosted histamine concentrations, and increased goblet cell numbers in the intestinal epithelium. Vaccinated mice showed a significant 61.17% reduction in adult worms and a 58.22% reduction in muscle larvae after the T. spiralis challenge. The adenovirus vector-delivered TsCLP amplifies local mucosal immunity, eliciting a Th1/Th2 mixed immune response that facilitates the expulsion of T. spiralis. Our study provides a feasible and promising approach for Trichinella vaccines, further highlighting the potential of an adenovirus vector for anti-helminth vaccine development.

Trichinellosis, a zoonotic parasitic disease caused by Trichinella spiralis, poses a significant threat to global food safety and public health. Current vaccine strategies face a critical limitation in their inability to effectively induce mucosal immunity, particularly during the early intestinal invasion phase of the parasite. To address this challenge, we developed a recombinant adenovirus vaccine (rAd5TsCLP) targeting the T. spiralis cystatin-like protein (TsCLP). Though a heterologous strategy (intranasal priming with adenoviral vaccine followed by intramuscular with recombinant protein vaccine) effectively induced high levels of specific serum antibodies(IgG, IgG1, IgG2a, IgM) and neutralizing antibodies, with peak of IFN-γ, IL-13, and IL-4 in serum, spleen and cervical lymph node. Furthermore, elevated levels of secretory IgA (sIgA), histamine, and goblet cell proliferation were observed. After challenge, immunized mice showed significant protective efficacy, with adult worm and muscle larvae burdens reduced by 61.17% and 58.22%. These findings highlight the potential of adenoviral vectors to enhance local mucosal immunity and induce mixed Th1/Th2 responses, offering a promising prime-boost strategy for the development of Trichinella vaccines.