Maternal hematological and virological characteristics during early feline immunodeficiency virus (FIV) infection of cats as predictors of fetal infection and reproductive outcome at early gestation

Reproduction of Domestic Cats in Laboratories, Catteries, and Feral Colonies: A Review

Cat reproduction is important for research and commercial cat breeding operations, as well as the control of feral cat populations. This review describes studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats, including sexual maturity, the estrous cycle (timing, behavior, and hormonal changes), seasonal effects, gestation length, parturition (litter size, litter weight, and parity effects), mortality, and stillbirth. Because the studies highlighted in this review vary in the location where they were conducted and the region's management practices, these factors should be considered depending on the goal of the reader when interpreting these data. Furthermore, standard practices were lacking in some earlier studies of cat reproduction, so they should be considered for historical context only and may not reflect the actual reproductive potential of cats as described in the new studies due to advancements in husbandry practices and nutrition. The objective of this manuscript is to review scientific studies examining reproductive performance in laboratory cats, privately-owned breeding cats, and feral cats. The data sources for this manuscript included original research publications and scientific reviews from the veterinary literature. All reviews or studies that augmented the knowledge of the reproduction of domestic cats in laboratories, catteries, and feral colonies were included. Most studies on laboratory cats have been conducted under the conditions of controlled light cycles, temperature, and diet. The environmental effects on reproductive behavior are subtler than those in feral cat studies, but the effects are still distinguishable. Cat breeding studies focus on genetic effects and rely heavily on surveys or questionnaires from cat breeders. However, the reliability of these data can be variable, in part because the methodology of record-keeping and other protocols are generally not reported. In addition, laboratory animal management standards, specific pathogen-free cat colonies, and nutritional requirements for cats were not fully established until the 1970s. Reproductive outcomes of earlier studies may not be a true representation of the modern cat due to more advanced, regulated husbandry practices, including improvements in nutrition, resulting in diets formulated to meet feline requirements for every life stage.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) Transfusion Reaction Small Animal Consensus Statement (TRACS). Part 1: Definitions and clinical signs

OBJECTIVE

To use a systematic, evidence-based consensus process to develop definitions for transfusion reactions in dogs and cats.

DESIGN

Evidence evaluation of the literature was carried out for identified transfusion reaction types in dogs and cats. Reaction definitions were generated based on synthesis of human and veterinary literature. Consensus on the definitions was achieved through Delphi-style surveys. Draft recommendations were made available through industry specialty listservs and comments were incorporated.

RESULTS

Definitions with imputability criteria were developed for 14 types of transfusion reactions.

CONCLUSIONS

The evidence review and consensus process resulted in definitions that can be used to facilitate future veterinary transfusion reaction research.

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.

Role of Feline Immunodeficiency Virus in Lymphomagenesis--Going Alone or Colluding?

Feline immunodeficiency virus (FIV) is a naturally occurring lentivirus of domestic and nondomestic feline species. Infection in domestic cats leads to immune dysfunction via mechanisms similar to those caused by human immunodeficiency virus (HIV) and, as such, is a valuable natural animal model for acquired immunodeficiency syndrome (AIDS) in humans. An association between FIV and an increased incidence of neoplasia has long been recognized, with frequencies of up to 20% in FIV-positive cats recorded in some studies. This is similar to the rate of neoplasia seen in HIV-positive individuals, and in both species neoplasia typically requires several years to arise. The most frequently reported type of neoplasia associated with FIV infection is lymphoma. Here we review the possible mechanisms involved in FIV lymphomagenesis, including the possible involvement of coinfections, notably those with gamma-herpesviruses.

Update on Canine and Feline Blood Donor Screening for Blood-Borne Pathogens

An update on the 2005 American College of Veterinary Internal Medicine (ACVIM) Consensus Statement on blood donor infectious disease screening was presented at the 2015 ACVIM Forum in Indianapolis, Indiana, followed by panel and audience discussion. The updated consensus statement is presented below. The consensus statement aims to provide guidance on appropriate blood‐borne pathogen testing for canine and feline blood donors in North America.

Aberrant placental immune parameters in the feline immunodeficiency virus (FIV)-infected cat suggest virus-induced changes in T cell function

Background

Immune activity during pregnancy must be tightly regulated to ensure successful pregnancy. This regulation includes the suppression of inflammatory activity that could target the semi-allogeneic fetus. Tregs are immunosuppressive; Th17 cells are pro-inflammatory. A precise balance in the two cell populations is critical to pregnancy maintenance, while dysregulation in this balance accompanies compromised pregnancy in humans and mice. FIV is known to target Tregs preferentially in the infected cat. Therefore, it may be hypothesized that FIV infection alters the placental Treg/Th17 cell balance resulting in aberrant immunomodulator expression by these cells and consequent pregnancy perturbation.

Methods

RNA was purified from random sections of whole placental tissues collected from both uninfected and FIV-infected queens at early pregnancy, including tissues from viable and nonviable fetuses. Real time qPCR was performed to quantify expression of intranuclear markers of Tregs (FoxP3) and Th17 cells (RORγ); cytokine products of Tregs (IL-10 and TGF-β), Th17 cells (IL-2, IL-6, and IL-17a), and macrophages (IL-1β); and the FIV gag gene. Pairwise comparisons were made to evaluate coexpression patterns between the cytokines and between the cytokines and the virus.

Results

Both FoxP3 and RORγ were reduced in placentas of infected animals. Neither infection status nor fetal viability affected placental expression of IL-1β. However, fetal nonviability was associated with reduced levels of all other cytokines. Infection and fetal nonviability impacted coexpression of various cytokine pairs. No obvious bias toward Treg or Th17 cells was observed.

Conclusions

FIV infection coupled with fetal nonviability alters expression patterns of T cell cytokines. These data suggest that functionally altered placental T cell leukocyte populations may occur in the infected queen and possibly contribute to fetal nonviability.

Imbalance of placental regulatory T cell and Th17 cell population dynamics in the FIV-infected pregnant cat

BACKGROUND

An appropriate balance in placental regulatory T cells (Tregs), an immunosuppressive cell population, and Th17 cells, a pro-inflammatory cell population, is essential in allowing tolerance of the semi-allogeneic fetus. TGF-β and IL-6 are cytokines that promote differentiation of Tregs and Th17 cells from a common progenitor; aberrant expression of the cytokines may perturb the balance in the two cell populations. We previously reported a pro-inflammatory placental environment with decreased levels of FoxP3, a Treg marker, and increased levels of IL-6 in the placentas of FIV-infected cats at early pregnancy. Thus, we hypothesized that FIV infection in the pregnant cat causes altered placental Treg and Th17 cell populations, possibly resulting in placental inflammation.

METHODS

We examined the effect of FIV infection on Treg and Th17 populations in placentas at early pregnancy using quantitative confocal microscopy to measure FoxP3 or RORγ, a Th17 marker, and qPCR to quantify expression of the key cytokines TGF-β and IL-6.

RESULTS

FoxP3 and RORγ were positively correlated in FIV-infected placentas at early pregnancy, but not placentas from normal cats, indicating virus-induced alteration in the balance of these cell populations. In control cats the expression of IL-6 and RORγ was positively correlated as predicted, but this relationship was disrupted in infected animals. TGF-β was reduced in infected queens, an occurrence that could dysregulate both Treg and Th17 cell populations. Co-expression analyses revealed a highly significant positive correlation between IL-6 and TGF-β expression in control animals that did not occur in infected animals.

CONCLUSION

Collectively, these data point toward potential disruption in the balance of Treg and Th17 cell populations that may contribute to FIV-induced inflammation in the feline placenta.

Immunomodulator expression in trophoblasts from the feline immunodeficiency virus (FIV)-infected cat

Background

FIV infection frequently compromises pregnancy under experimental conditions and is accompanied by aberrant expression of some placental cytokines. Trophoblasts produce numerous immunomodulators that play a role in placental development and pregnancy maintenance. We hypothesized that FIV infection may cause dysregulation of trophoblast immunomodulator expression, and aberrant expression of these molecules may potentiate inflammation and compromise pregnancy. The purpose of this project was to evaluate the expression of representative pro-(TNF-α, IFN-γ, IL-1β, IL-2, IL-6, IL-12p35, IL-12p40, IL-18, and GM-CSF) and anti-inflammatory cytokines (IL-4, IL-5, and IL-10); CD134, a secondary co-stimulatory molecule expressed on activated T cells (FIV primary receptor); the chemokine receptor CXCR4 (FIV co-receptor); SDF-1α, the chemokine ligand to CXCR4; and FIV gag in trophoblasts from early-and late-term pregnancy.

Methods

We used an anti-cytokeratin antibody in immunohistochemistry to identify trophoblasts selectively, collected these cells using laser capture microdissection, and extracted total RNA from the captured cell populations. Real time, reverse transcription-PCR was used to quantify gene expression.

Results

We detected IL-4, IL-5, IL-6, IL-1β, IL-12p35, IL-12p40, and CXCR4 in trophoblasts from early-and late-term pregnancy. Expression of cytokines increased from early to late pregnancy in normal tissues. A clear, pro-inflammatory microenvironment was not evident in trophoblasts from FIV-infected queens at either stage of pregnancy. Reproductive failure was accompanied by down-regulation of both pro-and anti-inflammatory cytokines. CD134 was not detected in trophoblasts, and FIV gag was detected in only one of ten trophoblast specimens collected from FIV-infected queens.

Conclusion

Feline trophoblasts express an array of pro-and anti-inflammatory immunomodulators whose expression increases from early to late pregnancy in normal tissues. Non-viable pregnancies were associated with decreased expression of immunomodulators which regulate trophoblast invasion in other species. The detection of FIV RNA in trophoblasts was rare, suggesting that the high rate of reproductive failure in FIV-infected queens was not a direct result of viral replication in trophoblasts. The influence of placental immune cells on trophoblast function and pregnancy maintenance in the FIV-infected cat requires additional study.

Cytokine dysregulation in early- and late-term placentas from feline immunodeficiency virus (FIV)-infected cats

PROBLEM

Experimental infection of cats with FIV-B-2542 produces high rates of fetal infection and reproductive failure. We hypothesized that dysregulation of placental cytokine expression occurs in FIV-infected queens, and aberrant expression potentiates inflammation and impacts pregnancy outcome. Our purpose was to quantify expression of representative pro-inflammatory cytokines (IL-6, IL-12p35, and IL-1β), IL-10 (anti-inflammatory), and the chemokine SDF-1α in early- and late-term placental tissues.

METHOD OF STUDY

 Real-time reverse transcriptase PCR was used to measure gene expression in placental tissues.

RESULTS

 Increased expression of IL-6 and IL-12p35 and decreased expression of IL-10 occurred in FIV-infected tissues at early pregnancy; at late gestation, IL-6 expression increased and IL-1β and SDF-1α decreased. At late pregnancy, IL-6 expression positively correlated with FIV load. IL-12:IL-10 ratios were higher in infected tissues at early, but not late pregnancy. Fetal non-viability accompanied decreased IL-12p35 and SDF-1α expression at both stages and decreased IL-12:IL-10 ratio at late pregnancy.

CONCLUSION

FIV infection caused a pro-inflammatory placental microenvironment at early, but not late pregnancy.

Expression of regulatory T cell (Treg) activation markers in endometrial tissues from early and late pregnancy in the feline immunodeficiency virus (FIV)-infected cat

Regulatory T cells (Tregs) support pregnancy maintenance by suppressing placental inflammation, while diminished Treg function may accompany reproductive failure. Experimental FIV infection frequently results in vertical transmission and increased pregnancy failure in the cat. The mechanism of reproductive compromise is unknown. We hypothesized that FIV infection alters endometrial Treg population dynamics and function, potentiating vertical transmission and reproductive failure. RNA collected from early and late gestation reproductive tissue and fetuses from FIV infected and control cats was probed for expression of FIV gag and Treg markers CD25, FOXP3, and CTLA4, using real time reverse-transcriptase (RT)-PCR. Frequent placental and fetal infection and reproductive failure were detected at early and late pregnancy. Expression of FOXP3 and CTLA4 was higher in early gestation tissues from control cats. FIV infection significantly reduced expression of FOXP3 and CTLA4 at early, but not late pregnancy. At late pregnancy, CTLA4 was expressed to higher levels in infected tissues. The number of tissues with decreased co-expression of FOXP3 and CTLA4 was significant in infected cats at early pregnancy. No significant changes in CD25 expression occurred between FIV-infected and control animals at early or late pregnancy. Differences in Treg marker expression were not significant between viable and non-viable pregnancies in infected cats. The detection of Treg markers in these feline tissues provides the first evidence of feline endometrial Tregs and suggests that such cells diminish as pregnancy progresses. These cells may be depleted or rendered less functional by viral infection, but understanding their role in pregnancy requires further study.

Placental immunopathology in the FIV-infected cat: a role for inflammation in compromised pregnancy?

In utero transmission of feline immunodeficiency virus (FIV) occurs frequently in queens experimentally infected with FIV-B-2542 and other FIV isolates. Fetal infection has been detected as early as 3-4 weeks gestation, and the incidence of fetal infection increases with progressing gestation. Reproductive failure occurs commonly, including fetal resorptions and developmentally-arrested fetuses, demonstrating that fetal demise occurs early in gestation. Precise, temporal immunomodulation within the placenta is essential for successful pregnancy. Placental Th1 and Th2 cytokines must be appropriately balanced, typically favoring Th2 cytokines at the maternal-fetal interface. Abnormal inflammatory cytokine expression often accompanies miscarriage. Regulatory T cells (Tregs) play an essential role in maternal tolerance of the semi-allogeneic fetus by suppressing inflammation. We are using the FIV-infected cat to examine the relationship between lentivirus-induced placental immunopathology and reproductive outcome. Using TaqMan real time reverse transcriptase (RT)-PCR, we measured relative expression of key immunomodulators in the placentas of FIV-B-2542-infected and control cats, including placentas from both viable and nonviable pregnancies. Our data associate significantly-increased expression of inflammatory cytokines with failed pregnancies, identify Treg markers in the placentas, and provide preliminary evidence that Tregs or other cells bearing similar activation markers may be involved in pregnancy maintenance. Our data suggest that placental inflammation in the FIV-infected cat may compromise pregnancy.