Clinical and Molecular Features of Feline Foamy Virus and Feline Leukemia Virus Co-Infection in Naturally-Infected Cats.

Liliane Cavalcante,Fernando Troccoli,Carlos Dias,Cláudia Muniz,William Switzer,André Santos,Sheila Medeiros,Anderson Augusto,Hongwei Jia,Marcelo Soares

doi:10.3390/v10120702

Abstract

Feline foamy virus (FFV) and feline leukemia virus (FeLV) belong to the Retroviridae family. While disease has not been reported for FFV infection, FeLV infection can cause anemia and immunosuppression (progressive infection). Co-infection with FFV/FeLV allows evaluation of the pathogenic potential and epidemiology of FFV infection in cats with FeLV pathology. Blood and buccal swab samples from 81 cats were collected in Rio de Janeiro. Plasma was serologically tested for FeLV. DNA extracted from peripheral blood mononuclear cells and buccal swabs was used to PCR detect FFV and FeLV. A qPCR was developed to detect and measure FFV proviral loads (pVLs) in cats. FeLV qPCR was performed using previous methods. The median log10 pVL of FFV mono-infected individuals was lower than found in FFV/FeLV co-infected cats in buccal swabs (p = 0.003). We found 78% of cats had detectable buccal FFV DNA in FFV mono-infected and FFV co-infected FeLV-progressive cats, while in FeLV-regressive cats (those without signs of disease) 22% of cats had detectable buccal FFV DNA (p = 0.004). Our results suggest that regressive FeLV infection may reduce FFV saliva transmission, the main mode of FV transmission. We did not find evidence of differences in pathogenicity in FFV mono- and -dually infected cats. In summary, we show that FVs may interact with FeLV within the same host. Our study supports the utility of cats naturally co-infected with retroviruses as a model to investigate the impact of FV on immunocompromised mammalian hosts.

Highlights

Foamy viruses (FV) are complex retroviruses that belong to the Retroviridae family and comprise a unique genus within the Spumaretrovirinae subfamily that naturally infect many vertebrates, including feline, simian, bovine, and equine [1]
When we compared median log10 proviral loads (pVLs) of feline foamy virus (FFV) mono- and FFV/feline leukemia virus (FeLV) co-infected individuals (Figure 2) we found higher FFV pVLs in buccal swab specimens in co-infected cats (p < 0.003; Figure 2A)
We evaluated pVLs of cat samples that were tested for both FFV and FeLV, but did not observe a correlation between FeLV and FFV pVLs in Peripheral blood mononuclear cells (PBMCs) among cats with progressive or regressive infection (Figure 3A)

Summary

Introduction

Foamy viruses (FV) are complex retroviruses that belong to the Retroviridae family and comprise a unique genus within the Spumaretrovirinae subfamily that naturally infect many vertebrates, including feline, simian, bovine, and equine [1]. A single case-control study reported the presence of hematological abnormalities in humans infected with gorilla simian foamy viruses (SFVs) [5]. Other studies failed to report diseases associated with FV in either natural infection of nonhuman primates or in zoonotic infection of humans with SFVs [6,7,8,9,10,11]. It has been hypothesized that FVs are not able to cause disease in healthy, naturally-infected individuals due to functional immune systems that control virus infection, but these results may be limited by the small numbers of infected persons followed longitudinally [12]. An absence of disease association with FVs may reflect an absence of systematic studies following infected individuals, animals or humans for long periods of time since other retroviruses can take decades for disease appearance and disease is not always found in all infected individuals.

Methods

Results

Conclusion