The protective rate of the feline immunodeficiency virus vaccine: An Australian field study

Global seroprevalence and factors associated with seropositivity for feline immunodeficiency virus (FIV) in cats: A systematic review and meta-analysis

The feline immunodeficiency virus (FIV) is a retrovirus of the Lentivirus genus, distributed worldwide, that causes persistent infection with a significant impact on the cats' health. Due to the importance of this infection in feline medicine, this pioneering study aimed to obtain an integrated estimate of the global seroprevalence of FIV in cats and to characterize the factors associated with this infection. Four electronic databases were screened for observational studies with FIV seroprevalence in cats published globally for this systematic review and meta-analysis. The initial search method returned 873 studies, of which 113 met all predefined criteria and were therefore included in this review. Meta-analysis with general data was performed, and a combined global seropositivity of 9.43 % (95 % CI: 8.24 % - 10.78 %) was found. Seropositivity was 14.34 % (95 % CI = 10.92 % - 18.61 %) in Asia, 11.90 % (95 % CI = 9.82 % - 14.34 %) in Oceania, 10.90 % (95 % CI = 5.71 % - 19.82 %) in Central America, 9.43 % (95 % CI = 6.95 % - 12.66 %) in South America, 9 % (95 % CI = 0 - 80 %) in Africa, 8.98 % (95 % CI = 7.31 % - 10.98 %) in Europe, and 5.93 % (95 % CI = 4.33 % - 8.07 %) in North America. Meta-analysis of factors associated with seropositivity demonstrated that FIV seroprevalence was higher in male (Prevalence ratio [PR] = 2.53, 95 % CI = 2.16 - 2.95), adult (PR = 2.83, 95 % CI = 2.24 - 3.56), unowned status (PR = 1.47, 95 % CI = 1.07 - 2.03), sick status (PR = 2.46, 95 % CI = 1.97 - 3.06), and cats with outdoor access (PR = 4.38, 95 % CI = 2.26 - 8.47). The results demonstrated that FIV is globally distributed and has a high seroprevalence in some geographical areas. Information compiled from this research is relevant to understanding the worldwide epidemiology of FIV. It presents the potential to contribute to the planning of strategies focused on controlling and reducing cases in cat populations.

Biochemical and structural comparisons of non-nucleoside reverse transcriptase inhibitors against feline and human immunodeficiency viruses

BACKGROUND

Feline immunodeficiency virus (FIV) causes an acquired immunodeficiency-like syndrome in cats. FIV is latent. No effective treatment has been developed for treatment the infected cats. The first and second generations non-nucleoside reverse transcriptase inhibitors (NNRTIs) for HIV treatment, nevirapine (NVP) and efavirenz (EFV), and rilpivirine (RPV), were used to investigate the potential of NNRTIs for treatment of FIV infection.

OBJECTIVE

This study aims to use experimental and in silico approaches to investigate the potential of NNRTIs, NVP, EFV, and RPV, for inhibition of FIV reverse transcriptase (FIV-RT).

METHODS

The FIV-RT and human immunodeficiency virus reverse transcriptase (HIV-RT) were expressed and purified using chromatography approaches. The purified proteins were used to determine the IC50 values with NVP, EFV, and RPV. Surface plasmon resonance (SPR) analysis was used to calculate the binding affinities of NNRTIs to HIV-RT and FIV-RT. The molecular docking and molecular dynamic simulations were used to demonstrate the mechanism of FIV-RT and HIV-RT with first and second generation NNRTI complexes.

RESULTS

The IC50 values of NNRTIs NVP, EFV, and RPV against FIV-RT were in comparable ranges to HIV-RT. The SPR analysis showed that NVP, EFV, and RPV could bind to both enzymes. Computational calculation also supports that these NNRTIs can bind with both FIV-RT and HIV-RT.

CONCLUSIONS

Our results suggest the first and second generation NNRTIs (NVP, EFV, and RPV) could inhibit both FIV-RT and HIV-RT.

Field Performance of a Rapid Test to Detect Progressive, Regressive, and Abortive Feline Leukemia Virus Infections in Domestic Cats in Australia and Germany

Different feline leukemia virus (FeLV) infection outcomes are possible in cats following natural exposure, such as progressive infections (persistent viremia), regressive infections (transient or no viremia followed by proviral persistence) and abortive infections (presence of only antibodies). Laboratory-based testing is currently required for categorization of infection outcomes in cats. The aim of this study was to evaluate the field performance of a novel, rapid, combination point-of-care (PoC) test kit commercially available in Europe (v-RetroFel^®Ag/Ab; 2020-2021 version) to determine different FeLV infection outcomes by concurrent detection of FeLV antigen (p27) and antibodies against FeLV transmembrane envelope protein (p15E). A secondary aim was to evaluate the performance of the same test kit (v-RetroFel^®FIV) to determine positive/negative feline immunodeficiency virus (FIV) infection status by the detection of antibodies to FIV capsid protein (p24) and transmembrane glycoprotein (gp40). Two cohorts of domestic cats were recruited and tested with v-RetroFel^® using plasma or serum, including cats in Australia (n = 200) and cats in Germany (n = 170). Results from p27 antigen PoC testing, proviral DNA PCR, and neutralizing antibody testing or testing for antibodies against non-glycosylated surface unit envelope protein (p45) were used to assign cats to groups according to different FeLV infection outcomes. Testing with a laboratory-based FeLV p15E antibody ELISA was also performed for comparison. In the first cohort, v-RetroFel^®Ag/Ab correctly identified 89% (109/122) FeLV-unexposed cats and 91% (21/23) progressive infections, but no regressive (0/23) or abortive (0/32) infections. In the second cohort, v-RetroFel^®Ag/Ab correctly identified 94% (148/158) FeLV-unexposed cats and 100% (4/4) progressive infections, but no regressive (0/2) and only 17% (1/6) abortive infections. There was test agreement between v-RetroFel^®Ab and the p15E laboratory ELISA in 58.9% of samples. As a secondary outcome of this study, the sensitivity and specificity of v-RetroFel^®FIV testing in cohort 1 were 94.7% (18/19) and 98.3% (178/181), and in cohort 2, 30.0% (3/10) and 100.0% (160/160), respectively. Prior history of FIV vaccination did not produce any false-positive FIV results. In conclusion, v-RetroFel^®Ag/Ab (2020-2021 version) was unable to accurately determine different FeLV infection outcomes in the field. Improvements of the test prior to application to field samples are required.

Evaluation of a Point-of-Care Feline Immunodeficiency Virus (FIV) Test Kit (RapidSTATUS™ FIV) to Determine the FIV Status of FIV-Vaccinated and FIV-Unvaccinated Pet Cats in Australia

Simple Summary

This study evaluated a commercial point-of-care (PoC) feline immunodeficiency virus (FIV) test kit (RapidSTATUS™ FIV) for its accuracy in determining the FIV status of FIV-vaccinated and FIV-unvaccinated pet cats in Australia. In countries where FIV vaccination is used, veterinarians need a PoC kit that will produce a negative result for a FIV-uninfected cat, even if the cat is FIV-vaccinated or the FIV vaccination history is unknown, since incorrect diagnoses can impact negatively on the welfare of cats. FIV PoC kits also need to produce positive results in FIV-infected cats to help with appropriate management and to enable strategies to be implemented to prevent other cats from becoming FIV-infected. Results presented here show RapidSTATUS™ FIV to be highly accurate (98.8−100%) in a range of FIV-vaccinated and FIV-unvaccinated scenarios. Therefore, Australian veterinarians can reliably use RapidSTATUS™ FIV to rapidly and accurately determine the FIV status of all cats.

Abstract

Feline immunodeficiency virus (FIV) is a retrovirus that can cause immunosuppression, co-morbidities, and neoplasia in infected cats, and is commonly tested for in veterinary clinics and animal shelters in Australia. FIV diagnosis using point-of-care (PoC) kits to detect FIV antibodies in Australia is complicated by the commercial availability of an inactivated whole-FIV vaccine. The aim of this study was to determine the accuracy of the RapidSTATUS™ FIV antibody test kit in FIV-vaccinated and FIV-unvaccinated cats in Australia. Plasma from pet cats of known FIV vaccination and FIV infection statuses (n = 361), comprised of 57 FIV-uninfected cats annually vaccinated against FIV, 10 FIV-uninfected cats with lapsed FIV vaccination histories, 259 FIV-unvaccinated/FIV-uninfected cats, and 35 FIV-infected cats, was tested. RapidSTATUS™ FIV testing had sensitivity of 97.1% (34/35) and specificity of 100% (326/326), with an overall accuracy of 99.7% (360/361). Additional testing was undertaken using plasma from FIV-uninfected cats recently administered a primary FIV vaccination course (n = 12) or an annual booster FIV vaccination (n = 10). RapidSTATUS™ FIV was 98.8% (81/82) accurate and 100% (32/32) accurate in cats recently administered primary or annual FIV vaccinations, respectively. The high level of accuracy of RapidSTATUS™ FIV (98.8–100%) therefore establishes this PoC kit as a DIVA (differentiating infected from vaccinated animals) test. RapidSTATUS™ FIV is recommended to aid animal shelters, veterinarians, and researchers in Australia to accurately determine FIV infection status, irrespective of FIV vaccination history.

Developing a Feline Immunodeficiency Virus Subtype B Vaccine Prototype Using a Recombinant MVA Vector

The feline immunodeficiency virus (FIV) is a retrovirus with global impact and distribution, affecting both domestic and wild cats. This virus can cause severe and progressive immunosuppression culminating in the death of felids. Since the discovery of FIV, only one vaccine has been commercially available. This vaccine has proven efficiency against FIV subtypes A and D, whereas subtype B (FIV-B), found in multiple continents, is not currently preventable by vaccination. We, therefore, developed and evaluated a vaccine prototype against FIV-B using the recombinant viral vector modified vaccinia virus Ankara (MVA) expressing the variable region V1-V3 of the FIV-B envelope protein. We conducted preclinical tests in immunized mice (C57BL/6) using a prime-boost protocol with a 21 day interval and evaluated cellular and humoral responses as well the vaccine viability after lyophilization and storage. The animals immunized with the recombinant MVA/FIV virus developed specific splenocyte proliferation when stimulated with designed peptides. We also detected cellular and humoral immunity activation with IFN-y and antibody production. The data obtained in this study support further development of this immunogen and testing in cats.

Clinicopathological and Epidemiological Findings in Pet Cats Naturally Infected with Feline Immunodeficiency Virus (FIV) in Australia

Feline immunodeficiency virus (FIV) infection in experimentally infected domestic cats produces characteristic clinical manifestations including hematological changes, neurological disease, neoplasia (most notably lymphoma) and lymphopenia-mediated immunodeficiency predisposing cats to a range of secondary infections. Conflicting reports exist, however, with regard to disease associations and survival time in naturally FIV-infected cats. The purpose of this retrospective case−control study was to investigate the effect of natural FIV infection on hematological, blood biochemical and urinalysis parameters and survival time in three cohorts of pet cats in Australia. Cohorts 1 and 2 were recruited from a large veterinary hospital in Melbourne, Victoria (n = 525 and 282), while a third cohort consisted of cats recruited from around Australia as part of a FIV field vaccine efficacy trial (n = 425). FIV-infected cats in cohorts 1, 2 and 3 were found to have 15/37 (41%), 13/39 (33%) and 2/13 (15%) clinicopathological parameters significantly different to FIV-uninfected cats, respectively. Two changes in FIV-infected cats in cohort 1, hypochromia (low hemoglobin) and hyperglobulinemia, were outside the supplied reference intervals and should serve as diagnostic triggers for FIV testing. Kaplan−Meier survival analysis of cats in cohorts 1 and 2 combined did not find any difference between FIV-infected and FIV-uninfected cats, however a confounding factor was a large euthanasia rate within the first 12 months in both groups. Three significant (p < 0.05) spatial clusters of FIV infection were identified in Melbourne. A possible relationship between FIV infection status and socioeconomic disadvantage was discovered, based on three government indices of socioeconomic status (p < 0.001). Until longitudinal field studies are performed in Australia to further investigate the long-term effects of natural FIV infection, Australian veterinarians should consider FIV to be an important infection of pet cats, and recommend measures to prevent FIV infection.

Lack of association between feline AB blood groups and retroviral status: a multicenter, multicountry study

OBJECTIVES

The relationship between blood group antigens and disease has been studied in humans. Blood types have been associated with both decreased and increased rates of various infections. In addition, blood group expression has been shown to vary with some cancers and gastrointestinal diseases. The objective of this study was to explore whether there is a relationship between blood type and retroviral infections in cats.

METHODS

Case records from a veterinary research laboratory, veterinary teaching hospitals and veterinary blood banks were retrospectively searched for cats where both blood type and retroviral status (feline leukemia [FeLV], feline immunodeficiency virus [FIV] or both) were listed (part 1). In addition, a sample of 33 cats with confirmed FIV infection was genotyped to determine blood groups (part 2).

RESULTS

In part 1, 709 cats were identified, 119 of which were positive for retroviral infection. Among all cases, 621 were type A (87.6%), 68 were type B (9.6%) and 20 were type AB (2.8%). There was no relationship between overall retroviral status (positive/negative) and blood type (P = 0.43), between FeLV status and blood type (P = 0.86) or between FIV status and blood type (P = 0.94). There was no difference in the distribution of blood types between cats that were healthy and typed as possible blood donors vs sick cats that were typed prior to a possible transfusion (P = 0.13). In part 2, of the 33 FIV-infected cats, all blood group genotypes were identified, although this test did not discriminate type A from type AB.

CONCLUSIONS AND RELEVANCE

No relationship was identified between feline retroviral status and blood type in this study. The relationship between blood type and other disease states requires further study in veterinary patients.

Risk factors and clinical and laboratory findings associated with feline immunodeficiency virus and feline leukemia virus infections in Bangkok, Thailand

Background and Aim: Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses associated with chronic and neoplastic diseases in domestic and non-domestic cats. There has been increasing interest in the clinical importance of feline retroviruses in Thailand and the identification of associated risk factors in domestic cats. To prevent the spread of retroviral diseases and improve the management of retrovirus-infected cats, risk factors and associated clinical laboratory data must be clearly understood. This study aimed to identify the influence of household, lifestyle, health status, sterilization, clinical presentations, and laboratory findings on FIV- and FeLV-infected cats in Bangkok, Thailand. Materials and Methods: A total of 480 cats were evaluated for FeLV p27 antigen and FIV antibodies using Witness FeLV-FIV Rapid Test and SNAP FIV/FeLV Combo Test at a veterinary hospital service. Results: Of the 480 cats tested, 113 were positivefor virus infection, including 60 for FeLV (12.5%), 40 for FIV (8.3%), and 13 for both FeLV and FIV (2.7%). The findings revealed that the risk factors for cats infected with FeLV, FIV, or both FeLV and FIV were significantly different compared with those for non-infected cats (p < 0.05). Multivariate analysis showed that multi-cat ownership is a risk factor for the high prevalence of feline retrovirus infection, as multi-cat households exhibited a higher prevalence of infection than single-cat households. Anemic and sick cats were also at a greater risk of testing positive for specific retrovirus infections. FeLV-infected cats had a higher risk of anemia and low erythrocyte and thrombocyte counts (p ≤ 0.0001), whereas FIV-infected cats were more likely to have anemia and leukocytopenia than controls. Conclusion: Knowledge of the risk factors for retroviral diseases and associated clinical and laboratory findings can be used to develop strategies to reduce FIV and FeLV infections in cats.

Feline immunodeficiency virus (FIV) infection in domestic pet cats in Australia and New Zealand: Guidelines for diagnosis, prevention and management

Despite the passage of over 30 years since its discovery, the importance of feline immunodeficiency virus (FIV) on the health and longevity of infected domestic cats is hotly debated amongst feline experts. Notwithstanding the absence of good quality information, Australian and New Zealand (NZ) veterinarians should aim to minimise the exposure of cats to FIV. The most reliable way to achieve this goal is to recommend that all pet cats are kept exclusively indoors, or with secure outdoor access (e.g., cat enclosures, secure gardens), with FIV testing of any in‐contact cats. All animal holding facilities should aim to individually house adult cats to limit the spread of FIV infection in groups of animals that are stressed and do not have established social hierarchies. Point‐of‐care (PoC) FIV antibody tests are available in Australia and NZ that can distinguish FIV‐infected and uninfected FIV‐vaccinated cats (Witness™ and Anigen Rapid™). Although testing of whole blood, serum or plasma remains the gold standard for FIV diagnosis, PoC testing using saliva may offer a welfare‐friendly alternative in the future. PCR testing to detect FIV infection is not recommended as a screening procedure since a negative PCR result does not rule out FIV infection and is only recommended in specific scenarios. Australia and NZ are two of three countries where a dual subtype FIV vaccine (Fel‐O‐Vax® FIV) is available and offers a further avenue for disease prevention. Since FIV vaccination only has a reported field effectiveness of 56% in Australia, and possibly lower in NZ, FIV‐vaccinated cats should undergo annual FIV testing prior to annual FIV re‐vaccination using a suitable PoC kit to check infection has not occurred in the preceding year. With FIV‐infected cats, clinicians should strive to be even more thorough than usual at detecting early signs of disease. The most effective way to enhance the quality of life and life expectancy of FIV‐infected cats is to optimise basic husbandry and to treat any concurrent conditions early in the disease course. Currently, no available drugs are registered for the treatment of FIV infection. Critically, the euthanasia of healthy FIV‐infected cats, and sick FIV‐infected cats without appropriate clinical investigations, should not occur.

Anti-SU Antibody Responses in Client-Owned Cats Following Vaccination against Feline Leukaemia Virus with Two Inactivated Whole-Virus Vaccines (Fel-O-Vax® Lv-K and Fel-O-Vax® 5)

A field study undertaken in Australia compared the antibody responses induced in client-owned cats that had been vaccinated using two inactivated whole feline leukaemia virus (FeLV) vaccines, the monovalent vaccine Fel-O-Vax^® Lv-K and the polyvalent vaccine Fel-O-Vax^® 5. Serum samples from 428 FeLV-uninfected cats (118 FeLV-vaccinated and 310 FeLV-unvaccinated) were tested for anti-FeLV neutralising antibodies (NAb) using a live virus neutralisation assay to identify 378 FeLV-unexposed (NAb-negative) and 50 FeLV-exposed (NAb-positive; abortive infections) cats, following by anti-surface unit (SU) FeLV-A and FeLV-B antibody ELISA testing. An additional 42 FeLV-infected cats (28 presumptively regressively infected, 14 presumptively progressively infected) were also tested for anti-SU antibodies. NAb-positive cats displayed significantly higher anti-SU antibody ELISA responses compared to NAb-negative cats (p < 0.001). FeLV-unexposed cats (NAb-negative) that had been vaccinated less than 18 months after a previous FeLV vaccination using the monovalent vaccine (Fel-O-Vax^® Lv-K) displayed higher anti-SU antibody ELISA responses than a comparable group vaccinated with the polyvalent vaccine (Fel-O-Vax^® 5) (p < 0.001 for both anti-FeLV-A and FeLV-B SU antibody responses). This difference in anti-SU antibody responses between cats vaccinated with the monovalent or polyvalent vaccine, however, was not observed in cats that had been naturally exposed to FeLV (NAb-positive) (p = 0.33). It was postulated that vaccination with Fel-O-Vax^® 5 primed the humoral response prior to FeLV exposure, such that antibody production increased when the animal was challenged, while vaccination with Fel-O-Vax^® Lv-K induced an immediate preparatory antibody response that did not quantitatively increase after FeLV exposure. These results raise questions about the comparable vaccine efficacy of the different FeLV vaccine formulations and correlates of protection.

Lack of protection against feline immunodeficiency virus infection among domestic cats in New Zealand vaccinated with the Fel-O-Vax® FIV vaccine

Infections with feline immunodeficiency virus (FIV) are common in New Zealand, although the impact of those infections on the health status of the cats remains unclear. Although many cats are vaccinated yearly with a commercial FIV vaccine containing FIV subtypes A and D, the effectiveness of this vaccine in protection against infection with field FIVs is unclear, as a high proportion of New Zealand viruses belong to subtype C. The objective of the study was to compare the frequency of FIV infection among adult FIV-vaccinated and FIV-unvaccinated domestic cats with access to outdoors. Buccal swabs were collected by the participating veterinarians and tested for the presence of FIV provirus by quantitative PCR. Overall, 26/185 (14.0 %) samples were positive for FIV, including 7/82 (8.5 %) samples from FIV-unvaccinated and 19/103 (18.4 %) from FIV-vaccinated cats. There was no protective effect of vaccination on FIV infection among sampled cats (p = 0.05). Partial sequences of the FIV envelope gene from five New Zealand viruses were analysed by the maximum likelihood method. All clustered with other New Zealand FIV sequences from subtypes A (n = 2), C (n = 2) or putative recombinant viruses (n = 1). While the FIV vaccination did not prevent FIV infection among sampled cats, it may have had an impact on transmissibility of the virus or on disease progression. As neither was addressed in the current study, further research is needed to fully assess the potential benefits of FIV vaccination. Considering the frequency of FIV infection in FIV-vaccinated cats, FIV infection status should be monitored not only before the first vaccination, but before each yearly booster.

Cloning, Prokaryotic Soluble Expression, and Analysis of Antiviral Activity of Two Novel Feline IFN-ω Proteins

Cats are becoming more popular as household companions and pets, forming close relationships with humans. Although feline viral diseases can pose serious health hazards to pet cats, commercialized preventative vaccines are lacking. Interferons (IFNs), especially type I IFNs (IFN-α, IFN-β, and interferon omega (IFN-ω)), have been explored as effective therapeutic drugs against viral diseases in cats. Nevertheless, there is limited knowledge regarding feline IFN-ω (feIFN-ω), compared to IFN-α and IFN-β. In this study, we cloned the genes encoding feIFN-ωa and feIFN-ωb from cat spleen lymphocytes. Homology and phylogenetic tree analysis revealed that these two genes belonged to new subtypes of feIFN-ω. The recombinant feIFN-ωa and feIFN-ωb proteins were expressed in their soluble forms in Escherichia coli, followed by purification. Both proteins exhibited effective anti-vesicular stomatitis virus (VSV) activity in Vero, F81 (feline kidney cell), Madin-Darby bovine kidney (MDBK), Madin-Darby canine kidney (MDCK), and porcine kidney (PK-15) cells, showing broader cross-species antiviral activity than the INTERCAT IFN antiviral drug. Furthermore, the recombinant feIFN-ωa and feIFN-ωb proteins demonstrated antiviral activity against VSV, feline coronavirus (FCoV), canine parvovirus (CPV), bovine viral diarrhea virus (BVDV), and porcine epidemic diarrhea virus (PEDV), indicating better broad-spectrum antiviral activity than the INTERCAT IFN. The two novel feIFN-ω proteins (feIFN-ωa and feIFN-ωb) described in this study show promising potential to serve as effective therapeutic agents for treating viral infections in pet cats.

Uncontrolled Outdoor Access for Cats: An Assessment of Risks and Benefits

Uncontrolled outdoor access is associated with a number of welfare concerns for companion cats, including increased risks of disease and parasites, injury or death due to traffic, predation or ingestion of toxic substances, and getting permanently separated from their owner. In addition, cats pose a threat to local wildlife due to predatory behaviors, and can sometimes be a nuisance to human neighbors. Despite these concerns, recent estimates suggest that many owners are still providing their cats with uncontrolled outdoor access, likely because it also offers welfare benefits by allowing cats to perform natural behaviors, such as hunting, exploring, and climbing. While some have suggested that outdoor access is necessary to meet cats' behavioral needs and to prevent related behavioral problems, others have recommended various environmental enrichment strategies that can be developed to meet these needs within an indoor environment or through supervised and controlled outdoor access. This review examines the welfare issues and benefits associated with outdoor access for cats, as well as what is currently known about peoples' practices, knowledge, and attitudes about the provision of outdoor access for cats.

2020 AAFP Feline Retrovirus Testing and Management Guidelines

CLINICAL IMPORTANCE

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) infections are found in cats worldwide. Both infections are associated with a variety of clinical signs and can impact quality of life and longevity.

SCOPE

This document is an update of the 2008 American Association of Feline Practitioners' feline retrovirus management guidelines and represents current knowledge on pathogenesis, diagnosis, prevention and treatment of retrovirus infections in cats.

TESTING AND INTERPRETATION

Although vaccines are available for FeLV in many countries and for FIV in some countries, identification of infected cats remains an important factor for preventing new infections. The retrovirus status of every cat at risk of infection should be known. Cats should be tested as soon as possible after they are acquired, following exposure to an infected cat or a cat of unknown infection status, prior to vaccination against FeLV or FIV, and whenever clinical illness occurs. It might not be possible to determine a cat's infection status based on testing at a single point in time; repeat testing using different methods could be required. Although FeLV and FIV infections can be associated with clinical disease, some infected cats, especially those infected with FIV, can live for many years with good quality of life.

MANAGEMENT OF INFECTED CATS

There is a paucity of data evaluating treatments for infected cats, especially antiretroviral and immunomodulatory drugs. Management of infected cats is focused on effective preventive healthcare strategies, and prompt identification and treatment of illness, as well as limiting the spread of infection.

Risk of Feline Immunodeficiency Virus (FIV) Infection in Pet Cats in Australia is Higher in Areas of Lower Socioeconomic Status

Simple Summary

Some diseases are known to occur at a higher frequency in Australia in areas of social and economic disadvantage. Identification of these diseases is important for effective infection control strategies. We investigated whether an association existed between socioeconomic factors and three infectious diseases in cats (feline immunodeficiency virus, FIV; feline calicivirus, FCV; and feline herpesvirus-1, FHV-1) in Australia. Disease cases that were reported to a voluntary veterinary disease surveillance system (Disease WatchDog) between January 2010 and July 2017 were extracted and analysed. Postcodes of the owners of these cats were compared to four government-published indexes measuring socioeconomic disadvantage and advantage. An association between socioeconomic status and FIV infection, but not FCV and FHV-1 infection, was found. FIV infection was more commonly reported in areas of socioeconomic disadvantage according to all four indexes. Prevention strategies targeting lower socioeconomic communities may help to reduce the overall prevalence of FIV infection in Australia.

Abstract

Feline immunodeficiency virus (FIV), feline calicivirus (FCV), and feline herpesvirus (FHV-1) are common viral infections of domestic cats in Australia. A study was performed to investigate the possible effect of area-based socioeconomic factors on the occurrence of FIV, FCV, and FHV-1 infection in Australian client-owned cats. A total of 1044 cases, reported to a voluntary Australian online disease surveillance system between January 2010 and July 2017, were analysed with respect to their postcode-related socioeconomic factors using the Socio-Economic Indexes For Areas (SEIFA). SEIFA consists of four different indexes which describe different aspects of socioeconomic advantage and disadvantage. Signalment details including age, sex, neuter status, and breed were also considered. A significant correlation was observed between areas of lower socioeconomic status and a higher number of reported cases of FIV infection for all four SEIFA indexes (p ≤ 0.0002). Postcodes with SEIFA indexes below the Australian median (“disadvantaged” areas) were 1.6–2.3 times more likely to have reported cases of FIV infection than postcodes with SEIFA indexes above the median (“advantaged” areas). In contrast, no correlation was observed between the number of reported cases of FCV or FHV-1 infection and any of the four SEIFA indexes (p > 0.05). When signalment data were analysed for the three infections, FIV-infected cats were more likely to be older (p < 0.00001), male (p < 0.0001), neutered (p = 0.03), and non-pedigree (p < 0.0001) compared to FCV and FHV-1 infected cats. Results from this study suggest that area-based disease control strategies, particularly in areas of social disadvantage, might be effective in reducing the prevalence of FIV infection in pet cats in Australia.

The Diagnosis of Feline Leukaemia Virus (FeLV) Infection in Owned and Group-Housed Rescue Cats in Australia

A field study was undertaken to (i) measure the prevalence of feline leukaemia virus (FeLV) exposure and FeLV infection in a cross-section of healthy Australian pet cats; and (ii) investigate the outcomes following natural FeLV exposure in two Australian rescue facilities. Group 1 (n = 440) consisted of healthy client-owned cats with outdoor access, predominantly from eastern Australia. Groups 2 (n = 38) and 3 (n = 51) consisted of a mixture of healthy and sick cats, group-housed in two separate rescue facilities in Sydney, Australia, tested following identification of index cases of FeLV infection in cats sourced from these facilities. Diagnostic testing for FeLV exposure/infection included p27 antigen testing using three different point-of-care FeLV kits and a laboratory-based ELISA, real-time polymerase chain reaction (qPCR) testing to detect FeLV proviral DNA in leukocytes, real-time reverse-transcription PCR (qRT-PCR) testing to detect FeLV RNA in plasma, and neutralising antibody (NAb) testing. Cats were classified as FeLV-uninfected (FeLV-unexposed and presumptively FeLV-abortive infections) or FeLV-infected (presumptively regressive and presumptively progressive infections). In Group 1, 370 FeLV-unexposed cats (370/440, 84%), 47 abortive infections (47/440, 11%), nine regressive infections (9/440, 2%), and two progressive infections (2/440, 0.5%) were identified, and 12 FeLV-uninfected cats (12/440, 3%) were unclassifiable as FeLV-unexposed or abortive infections due to insufficient samples available for NAb testing. In Groups 2 and 3, 31 FeLV-unexposed cats (31/89, 35%), eight abortive infections (8/89, 9%), 22 regressive infections (22/89; 25%), and 19 progressive infections (19/89; 21%) were discovered, and nine FeLV-uninfected cats (9/89; 10%) were unclassifiable due to insufficient samples available for NAb testing. One of the presumptively progressively-infected cats in Group 3 was likely a focal FeLV infection. Two other presumptively progressively-infected cats in Group 3 may have been classified as regressive infections with repeated testing, highlighting the difficulties associated with FeLV diagnosis when sampling cats at a single time point, even with results from a panel of FeLV tests. These results serve as a reminder to Australian veterinarians that the threat of FeLV to the general pet cat population remains high, thus vigilant FeLV testing, separate housing for FeLV-infected cats, and FeLV vaccination of at-risk cats is important, particularly in group-housed cats in shelters and rescue facilities, where outbreaks of FeLV infection can occur.

Immunogenicity and Efficacy of a Novel Multi-Antigenic Peptide Vaccine Based on Cross-Reactivity between Feline and Human Immunodeficiency Viruses

For the development of an effective HIV-1 vaccine, evolutionarily conserved epitopes between feline and human immunodeficiency viruses (FIV and HIV-1) were determined by analyzing overlapping peptides from retroviral genomes that induced both anti-FIV/HIV T cell-immunity in the peripheral blood mononuclear cells from the FIV-vaccinated cats and the HIV-infected humans. The conserved T-cell epitopes on p24 and reverse transcriptase were selected based on their robust FIV/HIV-specific CD8⁺ cytotoxic T lymphocyte (CTL), CD4⁺ CTL, and polyfunctional T-cell activities. Four such evolutionarily conserved epitopes were formulated into four multiple antigen peptides (MAPs), mixed with an adjuvant, to be tested as FIV vaccine in cats. The immunogenicity and protective efficacy were evaluated against a pathogenic FIV. More MAP/peptide-specific CD4⁺ than CD8⁺ T-cell responses were initially observed. By post-third vaccination, half of the MAP/peptide-specific CD8⁺ T-cell responses were higher or equivalent to those of CD4⁺ T-cell responses. Upon challenge, 15/19 (78.9%) vaccinated cats were protected, whereas 6/16 (37.5%) control cats remained uninfected, resulting in a protection rate of 66.3% preventable fraction (p = 0.0180). Thus, the selection method used to identify the protective FIV peptides should be useful in identifying protective HIV-1 peptides needed for a highly protective HIV-1 vaccine in humans.

A survey of vaccine history in German cats and owners' attitudes to vaccination

OBJECTIVES

Vaccination is the most important measure for prevention of feline infectious diseases. Cat owner compliance with vaccination recommendations has been investigated in the UK but not in other European countries. The aim of the present study was to determine cat owners' attitudes towards vaccination in cats in Germany, to identify factors that are associated with the vaccination status of their cats and to compare the results with those of the UK survey.

METHODS

The survey was conducted using an online questionnaire and was aimed at respondents throughout Germany. Respondents under 16 years of age, cats that were less than 9 weeks old and veterinarians were excluded. A total of 920 questionnaires were evaluated, and information about cats and respondents was assessed with respect to the current vaccination status of the cats using a linear logistic regression model.

RESULTS

The majority of cats (77.9%; n = 717) were vaccinated according to current guidelines; only 5.4% (n = 50; 95% confidence interval [CI] 5.00-9.00) of cats had never received a vaccine. Having visited a cattery, a cat show or travelled abroad in the past 12 months (n = 96/773; odds ratio [OR] 6.95; 95% CI 1.65-52.19) had the highest positive impact on the vaccination status of cats. In addition, detailed veterinary advice about vaccination had a positive impact (n = 275/773; OR 2.09; 95% CI 0.67-6.25) on the attitude of owners towards vaccinating their cats.

CONCLUSIONS AND RELEVANCE

A history of travelling abroad or visiting cat shows or a cattery, and thus regulatory requirements, had the greatest positive impact on the current vaccination status of the cats. Veterinary consultation on preventive measures, including vaccination, is crucial for protecting the cat population against infectious diseases.

Lessons Learned in Developing a Commercial FIV Vaccine: The Immunity Required for an Effective HIV-1 Vaccine

The feline immunodeficiency virus (FIV) vaccine called Fel-O-Vax^® FIV is the first commercial FIV vaccine released worldwide for the use in domestic cats against global FIV subtypes (A⁻E). This vaccine consists of inactivated dual-subtype (A plus D) FIV-infected cells, whereas its prototype vaccine consists of inactivated dual-subtype whole viruses. Both vaccines in experimental trials conferred moderate-to-substantial protection against heterologous strains from homologous and heterologous subtypes. Importantly, a recent case-control field study of Fel-O-Vax-vaccinated cats with outdoor access and ≥3 years of annual vaccine boost, resulted in a vaccine efficacy of 56% in Australia where subtype-A viruses prevail. Remarkably, this protection rate is far better than the protection rate of 31.2% observed in the best HIV-1 vaccine (RV144) trial. Current review describes the findings from the commercial and prototype vaccine trials and compares their immune correlates of protection. The studies described in this review demonstrate the overarching importance of ant-FIV T-cell immunity more than anti-FIV antibody immunity in affording protection. Thus, future efforts in developing the next generation FIV vaccine and the first effective HIV-1 vaccine should consider incorporating highly conserved protective T-cell epitopes together with the conserved protective B-cell epitopes, but without inducing adverse factors that eliminate efficacy.

FIV vaccine with receptor epitopes results in neutralizing antibodies but does not confer resistance to challenge

Feline immunodeficiency virus (FIV) is the feline analogue to human immunodeficiency virus (HIV) and utilizes parallel modes of receptor-mediated entry. The FIV surface glycoprotein (SU) is an important target for induction of neutralizing antibodies, and autoantibodies to the FIV binding receptor (CD134) block infection ex vivo; thus highlighting the potential for immunotherapies which utilize anti-receptor antibodies to block viral infection. To determine whether vaccination with CD134-SU complexes could induce protection against FIV infection, cats (n = 5 per group) were immunized with soluble CD134, recombinant FIV-SU protein, and/or CD134+SU complexes. Two trials were performed with different antigen combinations and vaccination schedules. In vivo generation of anti-CD134 and anti-SU IgG antibodies was measured, and in vitro neutralization assays were conducted. Immunization induced production of anti-CD134 and anti-SU antibodies that significantly inhibited FIV infection in vitro. However, no vaccine combination protected cats from FIV infection, and neat serum from vaccinated cats enhanced FIV growth in vitro. CD134+SU vaccinated cats exhibited increased CD4:CD8 ratio immediately prior to challenge, and antibodies were much more efficiently generated against vaccine by-products versus target antigens. Results suggest vaccination against viral and cryptic receptor epitopes yields neutralizing antibodies that synergistically inhibit FIV infection in vitro. Factors contributing to vaccine failure may include: (1) Heat-labile serum factors that enhance viral replication, (2) changes in circulating target cell populations induced by vaccination, and (3) weak immunogenicity of neutralizing epitopes compared to off-target vaccine components. Results reinforce the need to monitor vaccine preparation components and avoid non-specific immune stimulation during vaccination.

A vaccine candidate for feline immunodeficiency virus elicits strong immunological reaction in vitro, but no protection to live cats. The feline analog to human immunodeficiency virus, FIV shares a similar infection paradigm and has only one partially effective vaccine. A US team, led by Colorado State University’s Susan VandeWoude, immunized cats using a complex of an FIV surface protein and a feline cell-surface protein known to facilitate FIV’s entry into immune cells. Tissue culture assays yielded promising results; however, this did not translate to live-animal protection. The researchers highlighted multiple factors that could explain the lack of success, including circulatory pro-infection factors, and immune responses generated against vaccine by-products rather than intended targets. While the vaccine candidate failed, the research provides invaluable guidance for future efforts into FIV vaccination with implications for HIV vaccine trials.

Applications of the FIV Model to Study HIV Pathogenesis

Feline immunodeficiency virus (FIV) is a naturally-occurring retrovirus that infects domestic and non-domestic feline species, producing progressive immune depletion that results in an acquired immunodeficiency syndrome (AIDS). Much has been learned about FIV since it was first described in 1987, particularly in regard to its application as a model to study the closely related lentivirus, human immunodeficiency virus (HIV). In particular, FIV and HIV share remarkable structure and sequence organization, utilize parallel modes of receptor-mediated entry, and result in a similar spectrum of immunodeficiency-related diseases due to analogous modes of immune dysfunction. This review summarizes current knowledge of FIV infection kinetics and the mechanisms of immune dysfunction in relation to opportunistic disease, specifically in regard to studying HIV pathogenesis. Furthermore, we present data that highlight changes in the oral microbiota and oral immune system during FIV infection, and outline the potential for the feline model of oral AIDS manifestations to elucidate pathogenic mechanisms of HIV-induced oral disease. Finally, we discuss advances in molecular biology, vaccine development, neurologic dysfunction, and the ability to apply pharmacologic interventions and sophisticated imaging technologies to study experimental and naturally occurring FIV, which provide an excellent, but often overlooked, resource for advancing therapies and the management of HIV/AIDS.

Duration of antibody response following vaccination against feline immunodeficiency virus

Objectives Recently, two point-of-care (PoC) feline immunodeficiency virus (FIV) antibody test kits (Witness and Anigen Rapid) were reported as being able to differentiate FIV-vaccinated from FIV-infected cats at a single time point, irrespective of the gap between testing and last vaccination (0-7 years). The aim of the current study was to investigate systematically anti-FIV antibody production over time in response to the recommended primary FIV vaccination series. Methods First, residual plasma from the original study was tested using a laboratory-based ELISA to determine whether negative results with PoC testing were due to reduced as opposed to absent antibodies to gp40. Second, a prospective study was performed using immunologically naive client-owned kittens and cats given a primary FIV vaccination series using a commercially available inactivated whole cell/inactivated whole virus vaccine (Fel-O-Vax FIV, three subcutaneous injections at 4 week intervals) and tested systematically (up to 11 times) over 6 months, using four commercially available PoC FIV antibody kits (SNAP FIV/FeLV Combo [detects antibodies to p15/p24], Witness FeLV/FIV [gp40], Anigen Rapid FIV/FeLV [p24/gp40] and VetScan FeLV/FIV Rapid [p24]). Results The laboratory-based ELISA showed cats from the original study vaccinated within the previous 0-15 months had detectable levels of antibodies to gp40, despite testing negative with two kits that use gp40 as a capture antigen (Witness and Anigen Rapid kits). The prospective study showed that antibody testing with SNAP Combo and VetScan Rapid was positive in all cats 2 weeks after the second primary FIV vaccination, and remained positive for the duration of the study (12/12 and 10/12 cats positive, respectively). Antibody testing with Witness and Anigen Rapid was also positive in a high proportion of cats 2 weeks after the second primary FIV vaccination (8/12 and 7/12, respectively), but antibody levels declined below the level of detection in most cats (10/12) by 1 month after the third (final) primary FIV vaccination. All cats tested negative using Witness and Anigen Rapid 6 months after the third primary FIV vaccination. Conclusions and relevance This study has shown that a primary course of FIV vaccination does not interfere with FIV antibody testing in cats using Witness and Anigen Rapid, provided primary vaccination has not occurred within the previous 6 months. Consequently, Witness and Anigen Rapid antibody test kits can be used reliably to determine FIV infection status at the time of annual booster FIV vaccination to help detect 'vaccine breakthroughs' and in cats that have not received a primary course of FIV vaccination within the preceding 6 months. The duration of antibody response following annual booster FIV vaccination and the resulting effect on antibody testing using PoC kits needs to be determined by further research. The mechanism(s) for the variation in FIV antibody test kit performance remains unclear.

Feline Immunodeficiency Virus Neuropathogenesis: A Model for HIV-Induced CNS Inflammation and Neurodegeneration

Feline Immunodeficiency virus (FIV), similar to its human analog human immunodeficiency virus (HIV), enters the central nervous system (CNS) soon after infection and establishes a protected viral reservoir. The ensuing inflammation and damage give rise to varying degrees of cognitive decline collectively known as HIV-associated neurocognitive disorders (HAND). Because of the similarities to HIV infection and disease, FIV has provided a useful model for both in vitro and in vivo studies of CNS infection, inflammation and pathology. This mini review summarizes insights gained from studies of early infection, immune cell trafficking, inflammation and the mechanisms of neuropathogenesis. Advances in our understanding of these processes have contributed to the development of therapeutic interventions designed to protect neurons and regulate inflammatory activity.

The Comparative Value of Feline Virology Research: Can Findings from the Feline Lentiviral Vaccine Be Translated to Humans?

Feline immunodeficiency virus (FIV) is a lentivirus of domestic cats that shares several similarities with its human counterpart, human immunodeficiency virus (HIV). Their analogies include genomic organization, lymphocyte tropism, viral persistence and induction of immunodeficiency. FIV is the only lentivirus for which a commercial vaccine is registered for prevention in either human or veterinary medicine. This provides a unique opportunity to investigate the mechanisms of protection induced by lentivirus vaccines at the population level and might contribute to the development of efficacious HIV vaccines. As well as having comparative value for vaccine studies, FIV research has shed some light on the relationship between lentiviral tropism and pathogenesis. Recent studies in our laboratory demonstrated that the interaction between FIV and its primary receptor changes as disease progresses, reminiscent of the receptor switch observed as disease progresses in HIV infected individuals. Here we summarise findings illustrating that, in addition to its veterinary significance, FIV has comparative value, providing a useful model to explore lentivirus–host interactions and to examine potential immune correlates of protection against HIV infection.

First Molecular Characterization of Feline Immunodeficiency Virus in Domestic Cats from Mainland China

The feline immunodeficiency virus (FIV) is a retrovirus of the Lentivirus genus that was initially isolated from a colony of domestic cats in California in 1986 and has now been recognized as a common feline pathogen worldwide. To date, there is only one recent serology-based report on FIV in mainland China which was published in 2016. We designed this study to investigate the molecular prevalence and diversity of feline immunodeficiency virus (FIV) in domestic cats from mainland China. We studied the prevalence of FIV in whole blood samples of 615 domestic cats in five cities (Beijing, Guangzhou, Nanjing, Shanghai and Yangzhou) of mainland China and examined them using FRET-PCR (Fluorescence Resonance Energy Transfer-Polymerase Chain Reaction) and regular PCRs for the gag and env genes. Overall, 1.3% (8/615) of the cats were positive for provirus DNA with nucleotide analysis using PCRs for the gag and env sequences showing the cats were infected with FIV subtype A. This is the first molecular characterization of FIV in mainland China and the first description of subtype A in continental Asia.