A recombinant human adenovirus type 5 vectored vaccine co-expression of VP1 and VP2 of chicken anemia virus elicits robust protective immune responses

Sep 29, 2026

Chicken anemia virus (CAV) drives major economic losses in poultry worldwide, yet existing vaccines do not fully protect against infection. Live attenuated vaccines carry risks of reverting to virulence, whereas conventional inactivated or subunit vaccines preferentially induce Th2-biased humoral immunity and often fail to generate the Th1-mediated cellular responses needed to clear infected cells. A recombinant adenovirus rAd5-CAV-VP1-VP2 was engineered to co-express VP1 and VP2, balancing Th1/Th2 responses and supporting VP1 folding. Vaccinated chicks were safe and highly immunogenic, with increased IFN-γ and IL-4, high VP1-specific antibody titers, and complete protection upon challenge, including reduced clinical disease and prevention of thymic atrophy and bone marrow failure.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages8

Reading Time20 min

AccessFree to download

Introduction

Chicken infectious anemia background

CAV transmission and immunopathogenesis

CAV genome and viral proteins

Limitations of conventional vaccines

105 (2026) 106258 Contents lists available at ScienceDirect Poultry Science journal [homepage:](homepage: www.elsevier.com/locate/psj)[ www.elsevier.com/locate/psj](homepage: www.elsevier.com/locate/psj) | A recombinant human adenovirus type 5 vectored vaccine co-expression of VP1 and VP2 of chicken anemia virus elicits robust protective
immune responses
Ruiqi Lia, Fanrun Menga,b, Haoze Zhou a, Fuqiang Guo a, Tianxing Yana, Hongbo Chenc , Feng Lang d, Ziqiang Chenga,*
a College of Veterinary Medicine, Shandong Agriculture University, Tai’an 271017, China b College of Veterinary Medicine, Hebei Agricultural University, Baoding 071001, China c School of Life Sciences, Longyan University, Longyan 364012, China
d Qingdao Yebio Bioengineering Co., Ltd., Qingdao 266000, China | | | | --- | --- | --- | | A R T I C L E I N F O | | A B S T R A C T | | Keywords:
Chicken anemia virus Recombinant adenoviral vector Cytokine
Protection | | Chicken anemia virus (CAV) causes significant economic losses in the poultry industry worldwide. As current vaccines do not confer complete protection, the development of a highly effective and safe vaccine is of paramount importance. Control strategies relying on live attenuated vaccines carry a risk of reversion to virulence, while conventional inactivated or subunit vaccines preferentially induce a Th2-biased humoral immune response. There often fail to elicit the critical Th1-mediated cellular immunity required to clear infected cells. This immunological imbalance underscores the need for a vaccine that activates both arms of the adaptive immune system. Here, we constructed a recombinant adenovirus, rAd5-CAV-VP1-VP2, which co-expresses two CAV antigens, leveraging the intrinsic ability of adenoviral vectors to induce a balanced Th1/Th2 response and utilizing the chaperone-like function of VP2 to ensure the correct conformational folding of VP1. Vaccination trials demonstrated that the rAd5-CAV-VP1-VP2 is safe and highly immunogenic, characterized by significantly upregulated levels of interferon-gamma (IFN-γ) and interleukin-4 (IL-4), and accompanied by high-titer VP1-specific antibodies. Crucially, upon challenge with a virulent CAV strain, the vaccinated chicks exhibited complete protection against mortality (100 %, 25/25), a significant alleviation of clinical symptoms, and prevention of the thymic atrophy and bone marrow failure. In conclusion, rAd5-CAV-VP1-VP2 elicits a robust and comprehensive immune response that effectively protects against CAV-induced clinical and pathological damage, presenting a promising, strategy for the control of chicken infectious anemia (CIA). | Introduction Chicken infectious anemia (CIA) is a highly contagious disease caused by the chicken anemia virus (CAV), primarily affecting chicks, characterized by aplastic anemia and thymic atrophy (Fatoba et al., 2022). Since its first isolation in China in 1996, the prevalence of CAV has continuously expanded (Zhou et al., 1996). For instance, investigations between 2020 and 2022 in chicken flocks showed the prevalence rates of 55-67 % in several Chinese provinces, a sharp increase from the previously reported (Yuasa and Imai, 1986), while the positive rate on farms in northern Vietnam was as high as 73.4 %(Hienet al., 2023). Virulent strains isolated in Japan caused anemia in 100 % of one-day-old chicks, with mortality rates reaching 90 %(Huynh et al., 2020), posing a severe threat to the global poultry industry. CAV persists within poultry populations through both vertical and horizontal transmission. Chicks lacking maternally derived antibodies (MDA) are susceptible to severe clinical disease upon infection (Eltahir et al., 2011). Infection in adult chickens is typically subclinical; however, the resulting persistent viremia impairs lymphoid tissues, rendering the birds highly susceptible to secondary opportunistic infections (Sun et al., 2023). This dual threat, comprising direct patho

FAQs

Why are current CAV vaccines considered insufficient?

Conventional live attenuated vaccines risk reversion to virulence, while inactivated or subunit vaccines often skew toward Th2-biased humoral responses. They may fail to elicit the Th1-mediated cellular immunity needed to clear infected cells.

What is rAd5-CAV-VP1-VP2 and what immune response does it target?

rAd5-CAV-VP1-VP2 is a recombinant adenovirus engineered to co-express CAV VP1 and VP2. The design aims to activate both Th1 and Th2 arms of adaptive immunity, producing stronger cellular and humoral protection.

What protective outcomes were observed after vaccination and challenge?

Vaccinated chicks showed safety and strong immunogenicity, including elevated IFN-γ and IL-4 and high-titer VP1-specific antibodies. Upon challenge with a virulent CAV strain, they demonstrated complete protection against mortality, improved clinical status, and prevention of thymic atrophy and bone marrow failure.

Sep 29, 2026

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