Holly L. Jordan

Cytotoxic T lymphocytes specific for the simian immunodeficiency virus.

Summary: A non‐human primate model for acquired immunodeficiency syndrome (AIDS), the simian immunodeficiency virus (SIV)‐infected rhesus monkey, was used to explore the role of the AIDS virus‐specific cytotoxic T‐lymphocyce (CTL) response in disease pathogenesis. This CTL response was measured using the major histocompatibility complex (MHC) class I/peptide tetramer technology, large numbers of tetramer‐binding CDS’ T lymphocytes were demonstrable not only in the peripheral blood, but in lymph nodes and even in semen of chronically SIV‐infected monkeys. The central role of these effector T lymphocytes in containing SIV spread during primary infection was demonstrated by showing that early SIV clearance during primary infection correlated with the emergence of the tetramer binding CD8+ T lymphocytes and that in vivo depletion of CD8+ lymphocytes eliminated the ability of the infected monkeys to contain SIV replication. These observations suggest that an effective AIDS vaccine should elicit a potent virus‐specific CTL response. In fact, a live, recombinant SIV vaccine constructed using the attenuated pox virus vector modified vaccinia Ankara (MVA) elicited a high‐frequency CTL response, comparable in magnitude to that elicited by SIV infection itself This suggests that vaccine modalities such as MVA may prove useful in creating an effective human immunodeficiency virus (HIV) vaccine, These studies also indicate the power of both the SIV/macaque model and MHC class I/peptide tetramers for assessing AIDS vaccine strategies.

Mucosally Transmitted Feline Immunodeficiency Virus Induces a CD8+ Antiviral Response that Correlates with Reduction of Cell-Associated Virus

Intravaginal inoculation of cats with feline immunodeficiency virus (FIV) results in acute systemic infection accompanied by a strong CD8+ immune response that inhibits viral replication. CD8+ anti-FIV activity, revealed by increased FIV replication in peripheral blood mononuclear cells (PBMC) depleted of CD8+ lymphocytes, was detected by 6 weeks after inoculation and correlated with reduced PBMC-associated virus at 12, 16, and 32 weeks after inoculation. Some cats with strong CD8+ anti-FIV activity during acute infection did not seroconvert and yielded no evidence of FIV infection at later times. These data suggest that CD8+ immunity may play a major role in eliminating virus during primary transmucosal FIV infection and may down-regulate viral replication during asymptomatic infection.

Elevated Interleukin-10-to-Interleukin-12 Ratio in Feline Immunodeficiency Virus-Infected Cats Predicts Loss of Type 1 Immunity to Toxoplasma gondii

Similar to human immunodeficiency virus, feline immunodeficiency virus (FIV) induces immunodeficiency and enhanced susceptibility to secondary pathogens. To explore cytokine alterations in lentivirus immunodeficiency, constitutive mRNA expression was measured in lymph nodes of healthy and FIV-infected cats before and after challenge with Toxoplasma gondii. Cytokine mRNA expression was similar in control and FIV-infected cats during the first 10 weeks after infection. At 16 weeks, interferon (IFN)-gamma, tumor necrosis factor-alpha, and interleukin (IL)-10 mRNA were increased in FIV-infected cats. Challenge with T. gondii induced an increase in IL-2, IFN-gamma, and IL-12 in the lymph nodes of control cats, whereas IFN-gamma and IL-10 but not IL-2 or IL-12 increased in the lymph nodes of FIV-T. gondii coinfected cats. These results indicate that FIV immunodeficiency may derive from a failure to generate an IL-12-dependent type 1 response and that an elevated level of IL-10 mRNA expression is a predictor of lentivirus immunodeficiency.

Horizontal transmission of feline immunodeficiency virus with semen from seropositive cats

The AIDS virus of cat species, feline immunodeficiency virus (FIV), has been used extensively as an animal model of HIV-1 infection. This felid lentivirus shares many molecular and biochemical traits with HIV-1 and causes similar immunologic and clinical perturbations, most notably CD4+ cell loss, impaired cell-mediated immunity and increased susceptibility to opportunistic pathogens. Previous reports have shown that FIV is transmitted horizontally by biting and vertically in utero and through nursing. Our objective was to determine whether FIV could be venereally transmitted in domestic cats. In the first experiment, susceptibility of the female reproductive tract to mucosal transmission of the FIV isolate, NCSU1, was demonstrated via intravaginal inoculation with infected cultured cells. We next identified virus in electroejaculates from asymptomatic, chronically FIV-NCSU1-infected, adult males. A fragment of FIV gag provirus DNA was detected by nested polymerase chain reaction (PCR) in nonfractionated seminal cells and in swim-up sperm preparations. Additionally, replication-competent virus was isolated from cell-free seminal plasma and seminal cells by co-cultivation with a feline CD4+ T-cell line. In the third study, queens were artificially inseminated via an intrauterine laparoscopic technique with electroejaculates from FIV-NCSU1-infected males. Of six inseminations carried out with fresh semen, three resulted in infection of queens. Lastly, immunohistochemical studies identified potential virus target cell populations in normal female reproductive tissues. In conclusion, these experiments indicate that FIV infection in domestic cats may provide a unique small animal model of sexual transmission of HIV-1.

Changes in lymphocyte subsets with age in perinatal cats: late gestation through eight weeks

The age-related changes in numbers and proportions of peripheral blood lymphocyte subsets (pan-T, CD4, CD8, Ig, and null) were evaluated by two-color flow cytometry in 16 feline fetuses (56-58 days gestational age) and 21 kittens from birth through 8 weeks of age. Populations of pan-T+, CD4+, and CD8+ cells increased in total numbers as a function of increases in total lymphocyte numbers while proportions of these subsets remained relatively static. In contrast, both the total number and proportion of Ig+ cells increased from birth to 4 weeks of age, after which there were essentially no changes. Null (pan-T-, Ig-) cells were highest during late gestation and declined steadily thereafter to become a minimal component of the peripheral lymphocyte subsets. Compared with normal adult values, CD4/CD8 ratios were high throughout the 8 week study period. These results illustrate that the neonatal cat blood lymphocyte profile undergoes maturational changes and emphasize the importance of evaluating age-matched controls in studies of conditions that may alter feline lymphocyte subsets.

Detection of feline immunodeficiency virus RNA by two nucleic acid sequence based amplification (NASBA) formats

Feline immunodeficiency virus (FIV) is an AIDS-inducing lentivirus that infects domestic cats worldwide. Because of its clinicopathologic similarities to human immunodeficiency virus type 1 (HIV-1) infection, the FIV/cat infection system is a valuable animal model for investigating comparative aspects of HIV-1 biology. An assay that detects quickly and efficiently FIV RNA in relatively small volume samples of feline blood or other body fluids would be of benefit in studies of viral transmission and antiviral interventions. Nucleic acid sequence based amplification (NASBA) technology is particularly suited for the detection of RNA in a variety of body fluids. In this report, the development of two rapid, sensitive and versatile NASBA formats is described for the detection of FIV gag RNA in plasma from infected cats. RNA detection by either format was unaffected by the presence of feline plasma. The limits of detection were at least 200 copies of input RNA for both formats. Results from seropositive and seronegative feline plasma samples were clearly distinguishable. These results demonstrate that NASBA provides a rapid and sensitive alternative to RT-PCR and culture isolation for detecting FIV RNA in infected feline plasma.

Distribution of immune cells in the female reproductive tract in uninfected and FIV infected cats

Cell-free and cell-associated FIV effectively cross the mucosa of the feline female reproductive tract. To identify possible cellular targets of FIV and to characterize changes in mucosal immunity after infection, we examined the types and numbers of immune cells residing in the reproductive tracts of control and intravaginally FIV-infected cats. Sections of the vestibule, vagina, cervix, uterus, and ovaries, were examined by immunohistochemistry for CD4+ and CD8+ T lymphocytes, CD22+ B lymphocytes, CD1a+ dendritic cells, and CD14+ macrophages. The reproductive tract of uninfected cats contained substantial numbers of CD8+ T lymphocytes, CD4+ T lymphocytes and macrophages, as well as moderate numbers of CD1a+ dendritic cells, and few B lymphocytes. The most prominent change between FIV- and FIV+ cats was a marked decrease in the concentration of CD4+ T lymphocytes resulting in inverted CD4+:CD8+ ratios throughout the reproductive tract of infected cats. There was also a trend towards increasing numbers of CD1a+ dendritic cells in the intravaginally-infected FIV+ cats, and decreasing numbers of macrophages and CD22+ B lymphocytes. This study indicates that similar to the peripheral immune system, FIV infection is associated with CD4+ cell loss and reduced CD4+:CD8+ ratios in the female reproductive mucosal tissue.

Domestic Cat Model for Predicting Human Nucleoside Analogue Pharmacokinetics in Blood and Seminal Plasma

ABSTRACT To establish whether a feline model can predict nucleoside analogue behavior in human semen, zidovudine (ZDV) and lamivudine (3TC) pharmacokinetic parameters (PKs) were determined in the blood and seminal plasma of healthy cats. Our results show considerable similarity in ZDV and 3TC PKs between cats and humans. As in humans, ZDV and 3TC tend to accumulate in feline seminal plasma. Area under the blood plasma concentration-time curve was predictive of seminal plasma excretion. The felid model offers a unique in vivo experimental alternative for investigating the pharmacokinetics of nucleoside analogues in the male genital tract.