The family Togaviridae comprises several significant human and veterinary mosquito-borne pathogens. Two togaviruses (genus Alphavirus) have been previously identified in association with marine mammals, the southern elephant seal virus (SESV) and Eastern equine encephalitis virus (EEEV) from a fatal captive harbor seal infection. Herein we report the ultrastructural and phylogenomic characterization of a novel marine togavirus, the first isolated from a cetacean, an Alaskan harbor porpoise (Phocoena phocoena) displaying ulcerative dermatitis. A skin sample was processed for virus isolation on Vero.DogSLAMtag cells and cytopathic effects (CPE) were observed on primary isolation approximately 20 days post-infection. Transmission electron microscopy of the infected Vero.DogSLAMtag cells revealed typical alphavirus particles budding from both plasma and vacuolar membranes of infected cells. A next-generation sequencing approach was used to determine the near complete genome of the Alaskan harbor porpoise alphavirus (AHPV). Phylogenetic analysis supported the AHPV as the sister species to the SESV, forming a marine mammal alphavirus clade separate from the recognized alphavirus antigenic complexes. Genetic comparison of the protein coding sequence of the AHPV to other alphaviruses demonstrated amino acid identities ranging from 42.1-67.1%, with the highest identity to the SESV. Based on its genetic divergence, we propose the AHPV represents a novel alphavirus species, pending formal proposal to and ratification by the International Committee on Taxonomy of Viruses. The ecological and genetic characteristics of the AHPV and the SESV also suggest they represent a novel antigenic complex within the genus Alphavirus, which we propose to be named the Marine Mammal Virus Complex. The role of the AHPV in the associated harbor porpoise cutaneous pathology, if any, remains unclear. Further research is needed to determine AHPV’s route(s) of transmission and potential vectors, host range, prevalence, and pathogenicity in cetaceans including harbour porpoises.

家庭披膜病毒包括几个显著人用和兽用蚊子传播的病原体。两种披膜病毒（甲病毒属）先前已被发现与海洋哺乳动物有关，南象海豹病毒 (SESV) 和东部马脑炎病毒 (EEEV) 来自致命的圈养斑海豹感染。在此，我们报告了一种新型海洋披膜病毒的超微结构和系统发育特征，该病毒首次从鲸类动物、阿拉斯加港湾鼠海豚 ( Phocoena phocoena) 显示溃疡性皮炎。处理皮肤样本以在 Vero.DogSLAMtag 细胞上分离病毒，并在感染后大约 20 天在初次分离时观察到细胞病变效应 (CPE)。受感染的 Vero.DogSLAMtag 细胞的透射电子显微镜显示出典型的甲病毒颗粒从受感染细胞的质膜和液泡膜中出芽。下一代测序方法用于确定阿拉斯加港湾鼠海豚甲病毒 (AHPV) 的近乎完整的基因组。系统发育分析支持 AHPV 作为 SESV 的姊妹物种，形成一个与公认的甲病毒抗原复合物分离的海洋哺乳动物甲病毒进化枝。AHPV 的蛋白质编码序列与其他甲病毒的遗传比较表明氨基酸同一性范围为 42.1-67.1%，与 SESV 的最高身份。基于其遗传差异，我们建议 AHPV 代表一种新的甲病毒种，等待国际病毒分类委员会的正式提议和批准。AHPV 和 SESV 的生态和遗传特征也表明它们代表了该属内的一种新型抗原复合物Alphavirus，我们建议将其命名为海洋哺乳动物病毒复合体。AHPV 在相关港湾鼠海豚皮肤病理学中的作用（如果有的话）仍不清楚。需要进一步的研究来确定 AHPV 的传播途径和潜在载体、宿主范围、流行率和在包括港湾鼠海豚在内的鲸类中的致病性。