The two canine adenovirus serotypes, CAV-1 and CAV-2, are distinguished by neutralization using canine antisera and via molecular analysis [
1]. CAV-1 targets the digestive tract and causes infectious hepatitis; CAV-2 infects respiratory tissues and induces infectious laryngotracheitis in dogs, raccoon dogs, foxes, and wolves [
2]. CAV-2, a member of the genus
Mastadenovirus of the family
Adenoviridae, is a non-enveloped icosahedral virus that replicates in the nucleus [
3]. The CAV-2 genome is double-stranded DNA 35 kb in size with approximately 30 open reading frames; the virus is 70–90 nm in dimensions. The three major structural proteins form the hexon, the penton base, and the fiber [
3]. The hexon (a major component of the viral capsid) is key in terms of inducing an immune response. The penton base stabilizes the capsid by interacting with the hexon, the capsomeres, and hexon-associated protein IIIa. The fiber featuring a tail, a shaft, and a knob interacts with the coxsackie adenovirus receptor (CAR); variable sequences on the fiber knob modulate hemagglutination with red cells of various species [
4]. CAV infects a wide range of animals including dogs worldwide [
56]. In Korea, the first CAV-1 infection was reported in a Eurasian rover otter in 2007, and the second in a fennec fox in 2014 [
78]. The first CAV-2 infections were reported in stray dogs in 2010 [
9]. The Korean CAV-2 isolate was obtained from a naturally infected dog in 2018 and its biological properties characterized [
10]. Typical symptoms of CAV-2 infection in dogs include a cough, fever, a runny nose, and red watery eyes. Dogs with strong defense mechanisms exhibit relatively mild respiratory symptoms. However, dogs infected with bacteria such as
Bordetella bronchiseptica, or that are immunocompromised, may die. In Korea, combination canine vaccines including CAV-1 and -2 antigens have been used to prevent dog infections since 1987. Although CAV-infected animals typically show moderate clinical symptoms, the prevalence of such infections among Korean animals is unclear. We previously performed a sero-surveillance of CAV-2 status in several animal species [
11]. Although live attenuated CAV vaccines have been given to Korean dogs, they are sourced from the United States or Canada. A vaccine based on the Korean CAV-2 strain would be preferable. Recently, we isolated a novel CAV-2 strain termed APQA1701 from a naturally infected Korean dog and sequentially passaged it 40 times in MDCK cell culture. The complete sequence showed that APQA1701 was a CAV-2 strain. Various adjuvants added to inactivated, subunit, and DNA vaccines enhanced dendritic cell activation and thus induced strong immune responses [
12]. New adjuvants such as Carbopol and the IMS gel are safe and efficient [
1314]. Here, we prepare an inactivated CAV-2 vaccine and assess its safety and immunogenicity in guinea pigs and dogs.