Genetic diversity of Koala retrovirus env gene subtypes: insights into northern and southern koala populations

Sarker, Nishat; Fabijan, Jessica; Seddon, Jennifer M.; Tarlinton, Rachael; Owen, Helen; Simmons, G. C.; Thia, Joshua A.; Blanchard, Adam; Speight, Natasha; Kaler, Jasmeet; Emes, Richard D.; Woolford, Lucy; Trott, Darren J.; Hemmatzadeh, Farhid; Meers, J.

doi:10.1099/jgv.0.001304

Cited by 28 publications

(75 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the current study, the South Australian koalas were KoRV‐A positive and KoRV‐B negative by PCR; however, they may have been infected with KoRV‐B or other subtypes at low levels below PCR detection . Despite this, it is unlikely that KoRV‐B is solely responsible for immune suppression and disease progression in South Australian koalas.…”

Section: Discussionmentioning

confidence: 58%

“…KoRV is a gammaretrovirus that is endogenous in all northern Australian populations (Queensland and New South Wales), while there are KoRV negative koalas in southern populations (South Australia and Victoria) and KoRV is presumed to be exogenously transmitted . Variants of KoRV, KoRV‐A to KoRV‐J, as determined by differences in the KoRV envelope gene, have been detected at high levels in Queensland koalas, while in South Australian koalas, KoRV‐A was the dominant variant type and other variants were detected at lower levels . Additionally, only KoRV‐A and not KoRV‐B was detected in wild South Australian koalas by PCR, suggesting KoRV‐A is the dominant infection in this population .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Periodontal disease in free‐ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection

et al. 2020

Self Cite

View full text Add to dashboard Cite

Background In northern Australian koala populations (Queensland and New South Wales), periodontal disease (gingivitis and periodontitis) is common while koala retrovirus subtype A is endogenous, with other subtypes transmitted exogenously. Koala retrovirus has been hypothesised to cause immune suppression and may predispose koalas to diseases caused by concurrent infections. In southern Australia populations (Victoria and South Australia) periodontal disease has not been investigated, and koala retrovirus is presumably exogenously transmitted. This study described oral health in South Australian koalas and investigated if an association between periodontal disease and koala retrovirus exists. Methods Oral health was examined for wild‐caught koalas from the Mount Lofty Ranges (n = 75). Koala retrovirus provirus was detected in whole blood using nested PCR and proviral load determined with qPCR. Periodontal disease severity was recorded and used to calculate the Final Oral Health Index (0‐normal, 24‐severe).Results Periodontal disease was observed in 84% (63/75) of koalas; 77% had gingivitis (58/75) and 65% (49/75) had periodontitis. The average Final Oral Health Index was 5.47 (s.d 3.13). Most cases of periodontal disease were associated with the incisors. Koala retrovirus‐infected koalas were more likely to present with periodontitis (p = 0.042) and the Final Oral Health Index was negatively correlated with proviral load (ρ = −0.353, p = 0.017). Conclusion South Australian koalas had a high prevalence of gingivitis and periodontitis. Periodontal disease was more prevalent in the incisors. Exogenous koala retrovirus infection may also facilitate the development of periodontitis by modulation of the immune response to concurrent oral bacterial infections.

show abstract

Section: Discussionmentioning

confidence: 58%

mentioning

confidence: 99%

Periodontal disease in free‐ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…While the identification of novel Env variants is important for understanding the epidemiology and evolutionary history of KoRV, the presence of a complete, intact genome is required to confirm a specific KoRV variant is replication competent, as both endogenous and exogenous retroviruses can be defective. For example, others found defective KoRV-B sequences in both zoo and wild koalas (7) and subtypes D and E were shown to be defective viruses (16,20,21,34).…”

Section: Discussionmentioning

confidence: 99%

“…In 2015, KoRV genetic diversity was found to be greater than originally believed with heterogeneity in subtypes occurring in the variable region A (VRA, amino acid positions 86-230) of the envelope protein (Env) involved in retrovirus receptor recognition and binding (7,8). Since then, studies employing PCR and sequence analysis have identified at least 9 different KoRV variants classified as subtypes A to I, with the first KoRV called subtype A and subtype B was found in a small group of captive koalas with increased neoplasia (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). A subtype J KoRV was reported but phylogenetic analysis with these newer subtypes shows it is clearly a subtype B variant (8,10,17).…”

Section: Introductionmentioning

confidence: 99%

“…A subtype J KoRV was reported but phylogenetic analysis with these newer subtypes shows it is clearly a subtype B variant (8,10,17). Not surprisingly for retroviruses, defective genomes have also been reported for KoRV subtypes B, D and E and included variants with env deletions (7,16,20,21). Like KoRV-A, KoRV-B and -E were also shown to infect a broad range of cells, including human cell lines, associated with the ability to utilize different thiamine transport protein 1 (THTR1) or other receptors raising concerns for zoonotic potential to humans (22)(23)(24)(25).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Koala Retrovirus Diversity, Transmissibility, and Disease Associations

Zheng¹,

Pan²,

Tang

et al. 2020

Preprint

View full text Add to dashboard Cite

Background Koalas are infected with the koala retrovirus (KoRV) that exists as exogenous or endogenous viruses. KoRV is genetically diverse with co-infection with up to ten envelope subtypes (A-J) possible; KoRV-A is the prototype endogenous form. KoRV-B, first found in a small number of koalas with an increased leukemia prevalence at one US zoo, has been associated with other cancers and increased chlamydial disease. To better understand the molecular epidemiology of KoRV variants and the effect of increased viral loads (VLs) on transmissibility and pathogenicity we developed subtype-specific quantitative PCR (qPCR) assays and tested blood and tissue samples from koalas at US zoos (n=78), two Australian zoos (n=27) and wild-caught (n=21) in Australia. We analyzed PCR results with available clinical, demographic, and pedigree data. Results All koalas were KoRV-A-infected. A small number of koalas (10.3%) at one US zoo were also infected with non-A subtypes, while a higher non-A subtype prevalence (59.3%) was found in koalas at Australian zoos. Wild koalas from one location were only infected with KoRV-A. We observed a significant association of infection and plasma VLs of non-A subtypes in koalas that died of leukemia/lymphoma and other neoplasias and report cancer diagnoses in KoRV-A-positive animals. Infection and VLs of non-A subtypes was not associated with age or sex. Transmission of non-A subtypes occurred from dam-to-offspring and likely following adult-to-adult contact, but associations with contact type were not evaluated. Brief antiretroviral treatment of one leukemic koala infected with high plasma levels of KoRV-A, -B, and -F did not affect VL or disease progression. Conclusions Our results show a significant association of non-A KoRV infection and plasma VLs with leukemia and other cancers. Although we confirm dam-to-offspring transmission of these variants, we also show other routes are possible. Our validated qPCR assays will be useful to further understand KoRV epidemiology and its zoonotic transmission potential for humans exposed to koalas because KoRV can infect human cells.

show abstract

Koala retrovirus epidemiology, transmission mode, pathogenesis, and host immune response in koalas (Phascolarctos cinereus): a review

2020

View full text Add to dashboard Cite

Koala retrovirus (KoRV) is a major threat to koala health and conservation. It also represents a series of challenges across the fields of virology, immunology, and epidemiology that are of great potential interest to any researcher in the field of retroviral diseases. KoRV is a gammaretrovirus that is present in both endogenous and exogenous forms in koala populations, with a still-active endogenization process. KoRV may induce immunosuppression and neoplastic conditions such as lymphoma and leukemia and play a role in chlamydiosis and other diseases in koalas. KoRV transmission modes, pathogenesis, and host immune response still remain unclear, and a clear understanding of these areas is critical for devising effective preventative and therapeutic strategies. Research on KoRV is clearly critical for koala conservation. In this review, we provide an overview of the current understanding and future challenges related to KoRV epidemiology, transmission mode, pathogenesis, and host immune response and discuss prospects for therapeutic and preventive vaccines.

show abstract

Genetic diversity of Koala retrovirus env gene subtypes: insights into northern and southern koala populations

Cited by 28 publications

References 41 publications

Periodontal disease in free‐ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection

Periodontal disease in free‐ranging koalas (Phascolarctos cinereus) from the Mount Lofty Ranges, South Australia, and its association with koala retrovirus infection

Koala Retrovirus Diversity, Transmissibility, and Disease Associations

Koala retrovirus epidemiology, transmission mode, pathogenesis, and host immune response in koalas (Phascolarctos cinereus): a review

Contact Info

Product

Resources

About