Transcriptomic responses of Galápagos finches to avian pox virus infection

Abstract

Emerging pathogens can have devastating effects on naive hosts, but disease outcomes often vary among hosts. Comparing the cellular response of different host species to infection can provide insight into mechanisms of host defense and the basis of host susceptibility to disease. Here, we used RNA-seq to characterize the transcriptomic response of Darwin's finches to avian poxvirus, which is introduced to the Galapagos Islands. We tested whether gene expression differs between infected and uninfected birds, and whether transcriptomic differences were related either to known antiviral mechanisms and/or the co-option of the host cellular environment by the virus. We compared two species, the medium ground finch (Geospiza fortis) and the vegetarian finch (Platyspiza crassirostris), to determine whether related species have similar responses to the same novel pathogen. We found that medium ground finches had a strong transcriptomic response to infection, upregulating genes involved in the innate immune response including interferon production, inflammation, and other immune signaling pathways. In contrast, vegetarian finches had a more limited response to infection. Our results also revealed evidence of viral manipulation of the host's cellular function and metabolism, providing insight into the ways in which poxviruses affect their hosts. Many of the transcriptomic responses to infection mirrored known processes seen in model and in-vitro studies of poxviruses indicating that many pathways of host defense against poxviruses are conserved among vertebrates and present even in hosts without a long evolutionary history with the virus. At the same time, the variation we observed between closely related species indicates that some endemic species of Galapagos finch may be more susceptible to avian pox than others.

Improved status of the conservation reliant Oahu Elepaio through effective management and natural adaptation

“…No other pathogen known to occur in Hawaii causes cutaneous lesions like those observed in elepaio. Presence of the distinctive cutaneous lesions is a common method of identifying birds infected with pox and has been used in many previous studies (e.g., Atkinson et al, 2005; McNew et al, 2021; Parker et al, 2011; van Riper et al, 2002; Zylberberg et al, 2012).…”

“…Biosecurity measures to prevent the introduction of alien birds, mosquitoes, and pathogens must be maintained and strengthened (Kilpatrick et al, 2004). Several other endemic Hawaiian bird species are in imminent danger of extinction, primarily because of increases in mosquito-borne diseases (Paxton et al, 2016), and pox also is an increasing threat to endemic birds in the Gal apagos Islands (McNew et al, 2021;Williams et al, 2021). Evolution of pox resistance in the Oahu Elepaio required at least several decades, perhaps longer; similar evolution could occur in other species, and management of other threats, such as predation, parasitism, and habitat degradation, could help to minimize population declines so there is time for adaptation to occur before the species become extinct.…”

Genotype–environment associations reveal genes potentially linked to avian malaria infection in populations of an endemic island bird

“…Pox & Malaria hsp70 upregulated during poxvirus infection in mouse and human models (Brum et al, 2003;Cheng et al, 2018;Jindal & Young, 1992;Kowalczyk et al, 2005;Sedger & Ruby, 1994) hsp70 highly differentiated between malaria-naïve and -exposed populations of a passerine bird Cyclophilins play a role against poxviruses in cell cultures (Castro et al, 2003;Zhou et al, 2021) Overexpressed in malaria-infected passerine (Videvall et al, 2015) mlycD Pox & Malaria --c8A Malaria Complement-related genes differentially expressed in pox-infected passerine birds (McNew et al, 2021). Complement may play a role in poxvirus response in mouse models (Miller et al, 1995) Complement system is activated against malaria (Kurtovic et al, 2020;Silver et al, 2010) and may act to control parasitaemia in passerine birds (Ellis et al, 2015).…”