Renal involvement in feline immunodeficiency virus infection: p24 antigen detection, virus isolation and PCR analysis

Investigations into disease associations with feline immunodeficiency virus (FIV) infection in lions (Panthera leo) in Australia: a case-control study

BACKGROUND

Feline immunodeficiency virus (FIV) is a highly mutable retrovirus with numerous species-specific strains, such as those infecting domestic cats (Felis catus, FIVFca) and wild populations of nondomestic cats including lions (Panthera leo, FIVPle). When FIVFca infection manifests as disease in domestic cats, common presentations include lymphadenopathy, lymphoid malignancies, oral cavity disease, immunological dysfunctions and neurological abnormalities. In contrast to domestic cats, there has been little published evidence of direct FIVPle disease associations in lions. The objective of the study, therefore, was to conduct a longitudinal case-control comparison of clinical findings and survival analysis of FIVPle-infected and FIVPle-uninfected captive lions to investigate possible FIVPle disease associations in nondomestic felids in Australia.

METHODS

Between 2005 and 2023, 38 lions were recruited from zoos across Australia. Lions had been FIV tested as part of a routine diagnostic service. The 38 lions included in the study comprised 15 FIV-infected (9 males, 6 females) and 23 FIV-uninfected (9 males, 14 females) animals. Lifetime longitudinal clinical histories and clinicopathological data collected by zoos for these lions were interrogated, including survival data.

RESULTS

FIV-infected lions were more likely to be reported with lower mean corpuscular volume (MCV) (fL) (P = 0.015), monocytes (%) (P = 0.023), chloride (mmol/L) (P = 0.016) and phosphate (mmol/L) (P = 0.029), but with a higher mean corpuscular hemoglobin concentration (MCHC) (g/L) (P = 0.001) and bicarbonate (mmol/L) (P = 0.035), than FIV-uninfected lions. The disease associations usually seen in domestic cats with FIV infection were not observed in lions, and there was no difference in survival between FIV-infected and FIV-uninfected lions. The main limitation of the study was a small sample size dictated by the number of lions able to be recruited from zoos in Australia over an 18-year period.

CONCLUSION

Few differences were found between case and control groups, suggesting that FIV-infected lions did not experience clinicopathological changes that predisposed them to future disease compared with FIV-uninfected lions. Further research will help to determine whether these results are indicative of a general absence of FIV-associated disease in captive lions, or the result of nonpathogenic FIVPle subtype(s) present in Australia.

Systolic blood pressure, routine kidney variables and renal ultrasonographic findings in cats naturally infected with feline immunodeficiency virus

Objectives Hypertension is a common cause of proteinuria in HIV-infected people. In cats, feline immunodeficiency virus (FIV) infection appears to be associated with proteinuria. Therefore, the results from systolic blood pressure (SBP) measurements in naturally infected FIV-positive cats were reviewed to assess whether hypertension contributes to the observed proteinuria in these cats. Ultrasonographic findings in FIV-positive cats were reviewed to complete renal assessment and to extend the scant knowledge on renal ultrasonography in cats. Methods Data from client-owned, naturally infected FIV-positive cats were retrospectively reviewed. To obtain a control group, records were reviewed from age-matched, privately owned, FIV-negative cats. Results Data from 91 FIV-infected and 113 control cats were compared. FIV-infected cats showed a significantly lower SBP ( P <0.0001) and significantly fewer FIV-infected cats were hypertensive (⩾160 mmHg) compared with control cats ( P = 0.025). The prevalence of renal azotaemia did not significantly differ between groups, although FIV-infected cats had significantly lower urine specific gravity (USG) ( P = 0.0273) and a higher incidence of USG below 1.035 ( P = 0.043). Urinary protein:creatinine ratio (UPC) was significantly higher in FIV-infected cats ( P = 0.0005) and proteinuria (UPC >0.4) occurred more frequently in FIV-infected cats ( P <0.001). Renal ultrasonography showed abnormalities in 60/91 FIV-infected cats, with hyperechogenic cortices in 39/91 and enlarged kidneys in 31/91. Conclusions and relevance Hypertension can be excluded as a common cause of renal damage leading to proteinuria in FIV-infected cats. Proteinuria and poorly concentrated urine are common in naturally infected FIV-positive cats, in contrast to azotaemia. Clinicians should cautiously interpret ultrasonographic abnormalities as these occur in over half of FIV-infected cats.

Risk Factors for Development of Chronic Kidney Disease in Cats

BACKGROUND

Identification of risk factors for development of chronic kidney disease (CKD) in cats may aid in its earlier detection.

HYPOTHESIS/OBJECTIVES

Evaluation of clinical and questionnaire data will identify risk factors for development of azotemic CKD in cats.

ANIMALS

One hundred and forty-eight client-owned geriatric (>9 years) cats.

METHODS

Cats were recruited into the study and followed longitudinally for a variable time. Owners were asked to complete a questionnaire regarding their pet at enrollment. Additional data regarding dental disease were obtained when available by development of a dental categorization system. Variables were explored in univariable and multivariable Cox regression models.

RESULTS

In the final multivariable Cox regression model, annual/frequent vaccination (P value, .003; hazard ratio, 5.68; 95% confidence interval, 1.83-17.64), moderate dental disease (P value, .008; hazard ratio, 13.83; 95% confidence interval, 2.01-94.99), and severe dental disease (P value, .001; hazard ratio, 35.35; 95% confidence interval, 4.31-289.73) predicted development of azotemic CKD.

CONCLUSION

Our study suggests independent associations between both vaccination frequency and severity of dental disease and development of CKD. Further studies to explore the pathophysiological mechanism of renal injury for these risk factors are warranted.

Antiviral treatment of feline immunodeficiency virus-infected cats with (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine

Feline immunodeficiency virus (FIV), the causative agent of an acquired immunodeficiency syndrome in cats (feline AIDS), is a ubiquitous health threat to the domestic and feral cat population, also triggering disease in wild animals. No registered antiviral compounds are currently available to treat FIV-infected cats. Several human antiviral drugs have been used experimentally in cats, but not without the development of serious adverse effects. Here we report on the treatment of six naturally FIV-infected cats, suffering from moderate to severe disease, with the antiretroviral compound (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine ([R]-PMPDAP), a close analogue of tenofovir, a widely prescribed anti-HIV drug in human medicine. An improvement in the average Karnofsky score (pretreatment 33.2 ± 9.4%, post-treatment 65±12.3%), some laboratory parameters (ie, serum amyloid A and gammaglobulins) and a decrease of FIV viral load in plasma were noted in most cats. The role of concurrent medication in ameliorating the Karnofsky score, as well as the possible development of haematological side effects, are discussed. Side effects, when noted, appeared mild and reversible upon cessation of treatment. Although strong conclusions cannot be drawn owing to the small number of patients and lack of a placebo-treated control group, the activity of (R)-PMPDAP, as observed here, warrants further investigation.

Aspectos histopatológicos das lesões renais em gatos experimentalmente infectados pelo vírus da imunodeficiência felina

A infecção pelo vírus da imunodeficiência felina (FIV) em gatos domésticos é caracterizada por distúrbios imunológicos, que geralmente se manifestam tardiamente na doença. Semelhante à infecção pelo vírus da imunodeficiência humana (HIV) em humanos, a infecção pelo FIV geralmente está associada a infecções oportunistas e ao desenvolvimento progressivo de nefropatia. Portanto, o objetivo do presente estudo foi avaliar as alterações histopatológicas em rins de 10 gatos experimentalmente infectados pelo FIV submetidos a eutanásia 60 meses após a inoculação viral. Nos rins de 100% dos gatos infectados pelo FIV foram visualizadas lesões glomerulares e tubulointersticiais. As lesões glomerulares eram caracterizadas principalmente por espessamento global ou segmentar da membrana basal glomerular (glomerulonefrite membranosa). Glomeruloesclerose e, em dois casos, proliferação de células epiteliais intraglomerulares (crescente glomerular), também foram observados. Nefrite intersticial linfoplasmocítica foi a alteração tubulointersticial mais frequente, visualizada em diferentes intensidades nos rins de 100% dos gatos. Os resultados do presente estudo demonstram que o tempo prolongado entre a infecção e a avaliação histopatológica pode ter sido decisivo para o surgimento das lesões renais em todos os gatos infectados pelo FIV e para o agravamento dessas lesões em alguns gatos.

Amyloidosis in association with spontaneous feline immunodeficiency virus infection

Tissues from 34 naturally feline immunodeficiency virus (FIV)-infected cats, 13 asymptomatic cats and 21 cats with signs of feline acquired immunodeficiency syndrome (F-AIDS), and 35 FIV-seronegative subjects were examined to determine the presence of amyloid deposits. Twenty experimentally FIV-infected cats and five specific pathogen-free (SPF) control cats were also included in the study. Paraffin-embedded sections from kidney and other organs were submitted to histological and histochemical analysis. Amyloid deposits were identified by a modified Congo red stain and confirmed by electron microscopy to demonstrate the presence of amyloid fibrils in amyloid positive glomeruli. In all positive cases, secondary amyloidosis was identified with potassium permanganate pretreatment and amyloid type was further characterised by immunohistochemistry using primary antibodies against human AA and feline AL amyloids. Amyloid deposits were present in different tissues of 12/34 (35%) naturally FIV-infected cats (seven presenting F-AIDS and five in asymptomatic phase) and in 1/30 FIV-seronegative cats. All the experimentally FIV-infected and SPF subjects showed no amyloid deposits. Amyloidosis has been reported in human lentiviral infections, and the data reported here demonstrate the need, in naturally FIV-infected cats, to consider the presence of amyloidosis in differential diagnosis of hepatic and renal disorders to better assess the prognosis of the disease.

Renal alterations in feline immunodeficiency virus (FIV)-infected cats: a natural model of lentivirus-induced renal disease changes

Human immunodeficiency virus (HIV) is associated with several renal syndromes including acute and chronic renal failures, but the underlying pathogenic mechanisms are unclear. HIV and feline immunodeficiency virus (FIV) share numerous biological and pathological features, including renal alterations. We investigated and compared the morphological changes of renal tissue of 51 experimentally and 21 naturally infected cats. Compared to the latter, the experimentally infected cats exhibited some mesangial widening and glomerulonephritis, milder proteinuria, and lower tubular and interstitial alterations. The numbers of giant protein tubular casts and tubular microcysts were also lower. In contrast, diffuse interstitial infiltrates and glomerular and interstitial amyloidosis were detected only in naturally infected cats. Similar alterations are found in HIV infected patients, thus supporting the idea of a causative role of FIV infection in renal disease, and underlining the relevance of the FIV and its natural host as an animal model for investigating lentivirus-associated nephropathy.

Feline immunodeficiency virus: disease association versus causation in domestic and nondomestic felids

Feline immunodeficiency virus (FIV) is an important infection in both domestic and nondomestic cats. Although many studies have provided insight into FIV pathophysiology and immunologic responses to infection in cats, questions remain regarding the association of FIV with specific disease syndromes. For many diseases, both association and causation of disease with FIV remain to be confirmed and clarified. The use of experimental infection models is unlikely to yield answers about naturally infected domestic cats and is not feasible in nondomestic felids, many of which are endangered species. Researches might consider further study of naturally occurring disease with an emphasis on confirming which diseases have a likely association with FIV.

Transgenic and infectious animal models of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) is a major cause of HIV-related morbidity and mortality. Transgenic and infectious models of HIVAN faithfully recapitulate the human disease and are important tools in advancing our understanding of disease pathogenesis, genetic susceptibility, and therapeutic intervention beyond the inhibition of viral replication. This review discusses the available transgenic murine models and infectious models of HIVAN in mice, rats, nonhuman primates, and felines. Particular emphasis is given to cell type-specific HIV expression as well as partial HIV genome expression used to map HIV-1 Nef and Vpr as pathologic determinants.

Naturally-occurring chronic renal disease in Australian cats: a prospective study of 184 cases

OBJECTIVE

To describe cases of naturally occurring feline chronic renal disease (CRD) in a defined population of Sydney.

DESIGN

Prospective case series.

METHODS

The inclusion criteria were the presence of a serum creatinine concentration above the reference range with either inadequately concentrated urine (urine specific gravity < or = 1.035), necropsy findings consistent with CRD, renal proteinuria or persistent azotaemia despite rehydration. Cats were excluded if a specific aetiology was identified ante or post mortem. Patients were divided into two categories (renal insufficiency or renal failure) on the basis of history, physical findings and serum creatinine concentration. The gender and age of cats with CRD was compared to an estimated Australian urban pet cat population. The breeds of cats with CRD were compared to the breeds of cats visiting the respective veterinary hospital where possible. Breed and gender comparisons were made using Fisher's exact tests. Age comparisons were made using Mann-Whitney U tests. The age at which cats were diagnosed with CRD was compared between veterinary hospitals using a Kruskal-Wallis test.

RESULTS

One hundred and eighty-four (99 female; 85 male) cats fulfilled the inclusion criteria. Amongst cats with CRD, males (median 12 years) were significantly younger than females (median 15 years; p = 0.001). The overall proportion of male and female cats with CRD was similar to that of the reference urban cat population (p = 0.41), however, between the ages of 9 and 11 years, male cats with CRD were over-represented (p = 0.038). Patients diagnosed with renal insufficiency (123 cats; median age 15 years) were significantly older than patients diagnosed with renal failure (61 cats; median age 11 years; p = 0.0001). The age at diagnosis of cats with CRD differed significantly between veterinary hospitals (p = 0.002).

CONCLUSION

Male cats with CRD were significantly younger than female cats with CRD. Younger cats were more likely to be diagnosed at an advanced stage of disease than older cats. The age at which cats were diagnosed with CRD was influenced by the clinic the cats attended. Whether these differences reflect differences in the aetiology of CRD or in the rate of disease progression warrants further investigation. Breed did not appear to play a significant role in the development of CRD in this survey.

Nuclear factor-kappa B binding to the HIV-1 LTR in kidney: implications for HIV-associated nephropathy

BACKGROUND

We have recently shown that renal epithelium is infected by HIV-1 and supports HIV-1 transcription in seropositive patients with renal disease. To investigate the regulation of HIV-1 gene expression in kidney, an HIV-1 transgenic mouse model was used to analyze the host transcriptional proteins that bind the 5' long-terminal repeat (LTR).

METHODS

Viral gene expression was assessed in transgenic mouse tissue using Northern blotting and mRNA in situ hybridization. The transcription factors involved in LTR binding were determined using electrophoretic mobility shift assays. Cytoplasmic and nuclear extracts were prepared from tissues with varied levels of transgene expression. The binding of transcription factors to specific LTR fragments was determined using DNA competition experiments and supershifts with transcription factor-specific antibodies.

RESULTS

Tissue-specific expression of the transgene was variable, with viral gene expression in the kidney at an intermediate level as compared with other tissues. Overall, the level of transgene expression directly correlated with abundance of nuclear factor-kappa B (NF-kappa B) in the nuclear extracts. High expressing tissue, however, had a constitutively active form of NF-kappa B. In contrast, the kidney contained an inducible NF-kappa B, which bound the LTR in combination with Sp1, suggesting a requirement for an activating event in renal HIV-1 expression of the LTR.

CONCLUSIONS

These studies indicate that the regulation of the HIV-1 LTR in the kidney is similar to lymphoid tissues, and may explain, in part, why the HIV-1 life cycle is supported in kidney.

Epidemiology of feline foamy virus and feline immunodeficiency virus infections in domestic and feral cats: a seroepidemiological study

Although foamy viruses (Spumaviruses) have repeatedly been isolated from both healthy and diseased cats, cattle, and primates, the primary mode of transmission of those common viruses remains undefined. A database of the feline foamy virus (FeFV) and feline immunodeficiency virus (FIV) antibody status, age, and sex of 389 domestic cats presented to veterinarians was assembled. A similar database for 66 feral (wild) cats was also assembled. That FeFV antibody status reflects infection was validated by PCR. Both FeFV and FIV infection rates were found to gradually increase with age, and over 70% of cats older than 9 years were seropositive for FeFV. In domestic cats, the prevalence of FeFV infection was similar in both sexes. In feral cats, FeFV infection was more prevalent in female cats than in male cats. Although both FeFV and FIV have been reported to be transmitted by biting, the patterns of infection observed are more consistent with an interpretation that transmission of these two retroviruses is not the same. The prevalence of FIV infection is highest in nondesexed male cats, the animals most likely to display aggressive behavior. The gradual increase in the proportion of FeFV-infected animals is consistent with transmission of foamy viruses by intimate social contact between animals and less commonly by aggressive behavior.