Koalas vaccinated against Koala retrovirus respond by producing increased levels of interferon-gamma
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Koalas vaccinated against Koala retrovirus respond by producing increased levels of interferon‑gamma Olusola Olagoke* , Bonnie L. Quigley and Peter Timms
Abstract Koala retrovirus (KoRV) is believed to be in an active state of endogenization into the koala genome. KoRV is present as both an endogenous and exogenous infection in all koalas in northern Australia. KoRV has been linked to koala pathologies including neoplasia and increased susceptibility to Chlamydia. A KoRV vaccine recently trialled in 10 northern koalas improved antibody response and reduced viral load. This communication reports the expression of key immune genes underlining the innate and adaptive immune response to vaccination in these northern koalas. The results showed that prior to vaccination, IL-8 was expressed at the highest levels, with at least 200-fold greater expression compared to other cytokines, while CD8 mRNA expression was significantly higher than CD4 mRNA expression level. Interferon-γ was up-regulated at both 4- and 8-weeks post-vaccination while IL-8 was down-regulated at 8-weeks post-vaccination. Keywords: Koala retrovirus, Vaccination, Immune response, mRNA, NanoString Background KoRV is currently undergoing endogenization into the koala genome, thus offering an exciting opportunity to study retroviral endogenization in real time [1, 2]. Nine KoRV subtypes (KoRV-A to -I) have been identified with the subtypes A and B being the most studied [3]. All northern koalas (Queensland and New South Wales) are thought to be harbour at least KoRV-A, a KoRV subtype which is both endogenous and infectious in these koala populations. KoRV infection has been linked to immune alterations, with infected southern koalas shown to have altered immune profiles [4] and KoRVB infected northern koalas shown to possess levels of immune dysregulation [5]. KoRV has also been linked to increased susceptibility to diseases in koalas [6]. We recently described antibody production and reduction in viral load following vaccination in koalas harbouring *Correspondence: [email protected] Genecology Research Centre, University of the Sunshine Coast, Sunshine Coast, QLD, Australia
endogenous KoRV [7]. Briefly, koalas were vaccinated with a recombinant KoRV Env protein along with a Triadjuvant of poly I:C, polyphosphazine and host defence peptide 1002. Each animal received the vaccine subcutaneously on day zero with a booster dose delivered four weeks after. The vaccine was shown to lead to a significant increase in serum anti-KoRV IgG levels and neutralising antibody titres. The antibodies were shown to be cross-reactive against exogenous KoRV subtypes. In the present study, we examined the expression of important koala cytokines, immune markers and host restrictions factors to determine their pre- and post-vaccination levels in northern koalas harbouring endogenous KoRV.
Main text To understand the expression profiles of key immune genes associated with vaccine response, we compared the pre-vaccination levels to 4- and 8-weeks p
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