Feline Leukemia Virus (FeLV) Disease Outcomes in a Domestic Cat Breeding Colony: Relationship to Endogenous FeLV and Other Chronic Viral Infections

Abstract

Exogenous feline leukemia virus (FeLV) is a feline gammaretrovirus that results in a variety of disease outcomes. Endogenous FeLV (enFeLV) is a replication-defective provirus found in species belonging to the genus, which includes the domestic cat (). There have been few studies examining interaction between enFeLV genotype and FeLV progression. We examined point-in-time enFeLV and FeLV viral loads, as well as occurrence of FeLV/enFeLV recombinants (FeLV-B), to determine factors relating to clinical disease in a closed breeding colony of cats during a natural infection of FeLV. Coinfections with feline foamy virus (FFV), feline gammaherpesvirus 1 (FcaGHV-1), and feline coronavirus (FCoV) were also documented and analyzed for impact on cat health and FeLV disease. Correlation analysis and structural equation modeling techniques were used to measure interactions among disease parameters. Progressive FeLV disease and FeLV-B presence were associated with higher FeLV proviral and plasma viral loads. Female cats were more likely to have progressive disease and FeLV-B. Conversely, enFeLV copy number was higher in male cats and negatively associated with progressive FeLV disease. Males were more likely to have abortive FeLV disease. FFV proviral load was found to correlate positively with higher FeLV proviral and plasma viral load, detection of FeLV-B, and FCoV status. Male cats were much more likely to be infected with FcaGHV-1 than female cats. This analysis provides insights into the interplay between endogenous and exogenous FeLV during naturally occurring disease and reveals striking variation in the infection patterns among four chronic viral infections of domestic cats. Endogenous retroviruses are harbored by many animals, and their interactions with exogenous retroviral infections have not been widely studied. Feline leukemia virus (FeLV) is a relevant model system to examine this question, as endogenous and exogenous forms of the virus exist. In this analysis of a large domestic cat breeding colony naturally infected with FeLV, we documented that enFeLV copy number was higher in males and inversely related to FeLV viral load and associated with better FeLV disease outcomes. Females had lower enFeLV copy numbers and were more likely to have progressive FeLV disease and FeLV-B subtypes. FFV viral load was correlated with FeLV progression. FFV, FcaGHV-1, and FeLV displayed markedly different patterns of infection with respect to host demographics. This investigation revealed complex coinfection outcomes and viral ecology of chronic infections in a closed population.

Presence of endogenous viral elements negatively correlates with FeLV susceptibility in puma and domestic cat cells

“…In this sampling of domestic cat fibroblast enFeLV components, solo LTRs range from 32-74 copies per cell, while env ranges from 9-13 copies per cell, similar to previous observations (Figure 2A). This is consistent with previously reported measures of full-length enFeLV range of 6-26 copies per cell (23, 34, 35), versus 19-58 copies of enFeLV LTR per cell (23). LTR copy number variation, but not full enFeLV genomes, correlated with FeLV replication as evidenced by directly proportional antigen load; enFeLV- env showed no correlation to either FeLV replication (Figure 2B-C).…”

“…Linear regression analysis therefore suggests that factors other than proviral integration number contributes to host susceptibility. This also corroborates observations made in vivo in a domestic cat colony naturally infected with FeLV (23), strongly suggesting that enFeLV LTR, versus other enFeLV elements, interacts with exogenous FeLV to mitigate infection.…”

“…It has been hypothesized that enFeLV may be associated with differences in infection outcome. We previously demonstrated enFeLV long terminal repeat (LTR) copy number was associated with better infection outcomes during a natural FeLV outbreak in a multi-cat household (23). Here, we evaluate FeLV infection of puma ( P. concolor ) and domestic cat cells in vitro and in situ to examine the susceptibility of endemic and novel hosts to FeLV infection with respect to enFeLV to provide further evaluation of this relationship.…”

Dynamics in incidence of detection of Feline Leukemia Virus in cats from Moscow metropolitan area in 2016-2018

“…Êðîìå òîãî, îíè, êàê ïðàâèëî, ïðîÿâëÿþòñÿ òîëüêî íà ñòàäèè íåîáðàòèìûõ èçìåíåíèé îðãàíîâ è òêàíåé. ×àñòî áîëåçíü çàêàí÷èâàåòñÿ ãèáåëüþ aeèâîòíûõ [7].…”

Feline leukemias: Features of pathogenic changes in blood

“…Coinfection with FeLV and feline panleukopenia virus (FPV) has been implicated in feline panleukopenia-like syndrome (FPLS), which is also termed FeLV-associated enteritis. FPLS resembles feline panleukopenia both clinically and histopathologically and is characterized clinically by progressive anorexia, depression, vomiting, hemorrhagic diarrhea, weight loss, gingivitis, oral ulceration, severe neutropenia, and septicemia (MacPete, 2014;Powers et al, 2018). FPV antigen is inconsistently present on diagnostic testing in these cases, and the pathogenesis and exact role of each virus in the development of this syndrome are incompletely understood.…”