Vaccination protects against in vivo-grown feline immunodeficiency virus even in the absence of detectable neutralizing antibodies.

ABSTRACT Here we report the antiretroviral activity of the experimental nucleoside reverse transcriptase inhibitor (NRTI) compound stampidine in cats chronically infected with feline immunodeficiency virus (FIV). Notably, a single oral bolus dose of 50 or 100 mg of stampidine per kg resulted in a transient ≥1-log decrease in the FIV load of circulating peripheral blood mononuclear cells in five of six FIV-infected cats and no side effects. A 4-week stampidine treatment course with twice-daily administration of hard gelatin capsules containing 25 to 100 mg of stampidine per kg was also very well tolerated by cats at cumulative dose levels as high as 8.4 g/kg and exhibited a dose-dependent antiretroviral effect. One of three cats treated at the 25-mg/kg dose level, three of three cats treated at the 50-mg/kg dose level, and three of three cats treated at the 100-mg/kg dose level (but none of three control cats treated with placebo pills) showed a therapeutic response, as evidenced by a ≥1-log reduction in the FIV load in peripheral blood mononuclear cells within 2 weeks. The previously documented in vitro and in vivo antiretroviral activity of stampidine against primary clinical human immunodeficiency virus type 1 isolates with genotypic and/or phenotypic NRTI resistance, together with its favorable animal toxicity profile, pharmacokinetics, and in vivo antiretroviral activity in FIV-infected cats, warrants further development of this promising new NRTI compound.

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Feline Immunodeficiency Virus-Infected Cat Sera Associated with the Development of Broad Neutralization Resistance In Vivo Drive Similar Reversions In Vitro

Journal of Virology ◽

10.1128/jvi.75.18.8868-8873.2001 ◽

2001 ◽

Vol 75 (18) ◽

pp. 8868-8873 ◽

Cited By ~ 6

Author(s):

Simone Giannecchini ◽

Donatella Matteucci ◽

Aldo Ferrari ◽

Mauro Pistello ◽

Mauro Bendinelli

Keyword(s):

Tissue Culture ◽

Feline Immunodeficiency Virus ◽

Surface Glycoprotein ◽

Virus Variant ◽

Humoral Immune ◽

Immunodeficiency Virus ◽

Escape Mutants ◽

Intervening Factors

ABSTRACT We previously reported that, upon reinoculation into cats, a neutralization-sensitive, tissue culture-adapted strain of feline immunodeficiency virus constantly reverted to the broad neutralization resistance typical of primary virus isolates and identified residue 481 in the V4 region of the surface glycoprotein as a key determinant of the reversion. Here, we found that well-characterized immune sera, obtained from cats in which such reversion had occurred, selected in tissue culture in favor of virus variants that also had a neutralization-resistant phenotype and had amino acid 481 changed, thus indicating that the host's humoral immune response is capable of driving the reversion in the absence of other intervening factors. In contrast, a second group of immune sera, elicited by a virus variant that had already reverted to neutralization resistance in independent cats, induced the emergence of escape mutants lacking broad neutralization resistance and neutralized fewer virus variants. It is proposed that the viral variants used to produce the two sets of sera may have generated different antibody repertoires.

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Induction of Primary Virus-Cross-Reactive Human Immunodeficiency Virus Type 1-Neutralizing Antibodies in Small Animals by Using an Alphavirus-Derived In Vivo Expression System

Journal of Virology ◽

10.1128/jvi.77.5.3119-3130.2003 ◽

2003 ◽

Vol 77 (5) ◽

pp. 3119-3130 ◽

Cited By ~ 40

Author(s):

Ming Dong ◽

Peng Fei Zhang ◽

Franziska Grieder ◽

James Lee ◽

Govindaraj Krishnamurthy ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Neutralizing Antibodies ◽

Neutralizing Activity ◽

Immunodeficiency Virus ◽

Hiv 1 ◽

Primary Virus

ABSTRACT We have studied the induction of neutralizing antibodies by in vivo expression of the human immunodeficiency virus type 1 (HIV-1) envelope by using a Venezuelan equine encephalitis virus (VEE) replicon system with mice and rabbits. The HIV-1 envelope, clone R2, has broad sensitivity to cross-reactive neutralization and was obtained from a donor with broadly cross-reactive, primary virus-neutralizing antibodies (donor of reference serum, HIV-1-neutralizing serum 2 [HNS2]). It was expressed as gp160, as secreted gp140, and as gp160ΔCT with the cytoplasmic tail deleted. gp140 was expressed in vitro at a high level and was predominantly uncleaved oligomer. gp160ΔCT was released by cells in the form of membrane-bound vesicles. gp160ΔCT induced stronger neutralizing responses than the other forms. Use of a helper plasmid for replicon particle packaging, in which the VEE envelope gene comprised a wild-type rather than a host range-adapted sequence, also enhanced immunogenicity. Neutralizing activity fractionated with immunoglobulin G. This activity was cross-reactive among a panel of five nonhomologous primary clade B strains and a Chinese clade C strain and minimally reactive against a Chinese clade E (circulating recombinant form 1) strain. The comparative neutralization of these strains by immune mouse sera was similar to the relative neutralizing effects of HNS2, and responses induced in rabbits were similar to those induced in mice. Together, these results demonstrate that neutralizing antibody responses can be induced in mice within 2 to 3 months that are similar in potency and cross-reactivity to those found in the chronically infected, long-term nonprogressive donor of HNS2. These findings support the expectation that induction of highly cross-reactive HIV-1 primary virus-neutralizing activity by vaccination may be realized.

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Effects of Regulatory T Cell Depletion on NK Cell Responses against Listeria monocytogenes in Feline Immunodeficiency Virus Infected Cats

Viruses ◽

10.3390/v11110984 ◽

2019 ◽

Vol 11 (11) ◽

pp. 984

Author(s):

Simões ◽

LaVoy ◽

Dean

Keyword(s):

Immune Response ◽

Listeria Monocytogenes ◽

Dendritic Cell ◽

Innate Immune Response ◽

Feline Immunodeficiency Virus ◽

Innate Immune ◽

Treg Depletion ◽

Cell Responses ◽

Immunodeficiency Virus

Regulatory T cells (Treg) are key players in the maintenance of peripheral tolerance, preventing autoimmune diseases and restraining chronic inflammatory diseases. Evidence suggests Treg cells and NK cells have important roles in feline immunodeficiency virus (FIV) pathogenesis; however, in vivo studies investigating the interplay between these two cell populations are lacking. We previously described innate immune defects in FIV-infected cats characterized by cytokine deficits and impaired natural killer cell (NK) and NK T cell (NKT) functions. In this study, we investigated whether in vivo Treg depletion by treatment with an anti-feline CD25 monoclonal antibody would improve the innate immune response against subcutaneous challenge with Listeria monocytogenes (Lm). Treg depletion resulted in an increased overall number of cells in Lm-draining lymph nodes and increased proliferation of NK and NKT cells in FIV-infected cats. Treg depletion did not normalize expression of perforin or granzyme A by NK and NKT cells, nor did Treg depletion result in improved clearance of Lm. Thus, despite the quantitative improvements in the NK and NKT cell responses to Lm, there was no functional improvement in the early control of Lm. CD1a+ dendritic cell percentages in the lymph nodes of FIV-infected cats were lower than in specific-pathogen-free control cats and failed to upregulate CD80 even when Treg were depleted. Taken together, Treg depletion failed to improve the innate immune response of FIV-infected cats against Lm and this may be due to dendritic cell dysfunction.

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Increased Immunogenicity of Human Immunodeficiency Virus gp120 Engineered To Express Galα1-3Galβ1-4GlcNAc-R Epitopes

Journal of Virology ◽

10.1128/jvi.00310-06 ◽

2006 ◽

Vol 80 (14) ◽

pp. 6943-6951 ◽

Cited By ~ 60

Author(s):

Ussama Abdel-Motal ◽

Shixia Wang ◽

Shan Lu ◽

Kim Wigglesworth ◽

Uri Galili

Keyword(s):

Human Immunodeficiency Virus ◽

Neutralizing Antibodies ◽

T Cell Response ◽

Immunogenic Peptides ◽

Immunodeficiency Virus ◽

Glycoprotein Gp120 ◽

Antigen Presenting ◽

Hiv Envelope ◽

Carbohydrate Chains

ABSTRACT The glycan shield comprised of multiple carbohydrate chains on the human immunodeficiency virus (HIV) envelope glycoprotein gp120 helps the virus to evade neutralizing antibodies. The present study describes a novel method for increasing immunogenicity of gp120 vaccine by enzymatic replacement of sialic acid on these carbohydrate chains with Galα1-3Galβ1-4GlcNAc-R (α-gal) epitopes. These epitopes are ligands for the natural anti-Gal antibody constituting ∼1% of immunoglobulin G in humans. We hypothesize that vaccination with gp120 expressing α-gal epitopes (gp120αgal) results in in vivo formation of immune complexes with anti-Gal, which targets vaccines for effective uptake by antigen-presenting cells (APC), due to interaction between the Fc portion of the antibody and Fcγ receptors on APC. This in turn results in effective transport of the vaccine to lymph nodes and effective processing and presentation of gp120 immunogenic peptides by APC for eliciting a strong anti-gp120 immune response. This hypothesis was tested in α-1,3-galactosyltransferase knockout mice, which produce anti-Gal. Mice immunized with gp120αgal produced anti-gp120 antibodies in titers that were >100-fold higher than those measured in mice immunized with comparable amounts of gp120 and effectively neutralized HIV. T-cell response, measured by ELISPOT, was much higher in mice immunized with gp120αgal than in mice immunized with gp120. It is suggested that gp120αgal can serve as a platform for anti-Gal-mediated targeting of additional vaccinating HIV proteins fused to gp120αgal, thereby creating effective prophylactic vaccines.

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Simple in vitro methods for titrating Feline Immunodeficiency Virus (FIV) and FIV neutralizing antibodies

Journal of Virological Methods ◽

10.1016/0166-0934(92)90026-a ◽

1992 ◽

Vol 37 (3) ◽

pp. 241-252 ◽

Cited By ~ 23

Author(s):

Franco Tozzini ◽

Donatella Matteucci ◽

Patrizia Bandecchi ◽

Fulvia Baldinotti ◽

Alessandro Poli ◽

...

Keyword(s):

Feline Immunodeficiency Virus ◽

Neutralizing Antibodies ◽

In Vitro Methods ◽

Immunodeficiency Virus

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Construction and In Vitro Characterization of Attenuated Feline Immunodeficiency Virus Long Terminal Repeat Mutant Viruses

Journal of Virology ◽

10.1128/jvi.75.2.1054-1060.2001 ◽

2001 ◽

Vol 75 (2) ◽

pp. 1054-1060 ◽

Cited By ~ 12

Author(s):

Luisa Bigornia ◽

Kristen M. Lockridge ◽

Ellen E. Sparger

Keyword(s):

Long Terminal Repeat ◽

Virus Replication ◽

Feline Immunodeficiency Virus ◽

Terminal Repeat ◽

Immunodeficiency Virus ◽

Activation Pathways ◽

Virus Expression ◽

Transcriptional Elements

ABSTRACT AP-1- and ATF-binding sites are cis-acting transcriptional elements within the U3 domain of the feline immunodeficiency virus (FIV) long terminal repeat (LTR) that serve as targets for cellular activation pathways and may regulate virus replication. We report that FIV LTR mutant proviruses encoding U3 deletions of the ATF-binding sequence exhibited restricted virus expression and replication in both feline lymphocytes and macrophages. In contrast, deletion of the AP-1 site had negligible effects on virus expression and replication. FIV LTR mutant proviruses encoding deletions of both the AP-1 and ATF sites or a 72-bp deletion encompassing the AP-1 site, duplicated C/EBP sites, and ATF sites were severely restricted for virus expression. These results demonstrate that deletion of either the ATF-binding site or multiplecis-acting transcriptional elements attenuates FIV. These attenuated FIV mutants provide opportunities to characterize the role of cis-acting elements in virus replication in vivo and to test LTR mutants as attenuated virus vaccines.

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Differential Cell Tropism of Feline Immunodeficiency Virus Molecular Clones In Vivo

Journal of Virology ◽

10.1128/jvi.73.4.2596-2603.1999 ◽

1999 ◽

Vol 73 (4) ◽

pp. 2596-2603 ◽

Cited By ~ 39

Author(s):

Gregg A. Dean ◽

Sunee Himathongkham ◽

Ellen E. Sparger

Keyword(s):

Feline Immunodeficiency Virus ◽

Mononuclear Cells ◽

Lymphocyte Subsets ◽

Cell Tropism ◽

Replication Efficiency ◽

Proviral Dna ◽

Immunodeficiency Virus ◽

Differential Cell

ABSTRACT Independent studies have demonstrated different cell tropisms for molecular clones of feline immunodeficiency virus (FIV). In this report, we examined three clones, FIV-pF34, FIV-14, and FIV-pPPR, for replication in Crandell feline kidney (CrFK) cells, feline peripheral blood mononuclear cells (PBMC), and feline macrophage cultures. Importantly, cell tropism for these three clones was also examined in vivo. FIV-pF34 replication was efficient in CrFK cells but severely restricted in PBMC, whereas replication of FIV-pPPR was vigorous in PBMC but severely restricted in CrFK cells. FIV-14 replication was productive in both CrFK cells and PBMC. Interestingly, all three molecular clones replicated with similar efficiencies in primary feline monocyte-derived macrophages. In vivo, FIV-pF34 proved least efficient for establishing persistent infection, and proviral DNA when detectable, was localized predominately to nonlymphoid cell populations (macrophages). FIV-pPPR proved most efficient for induction of a persistent viremia in vivo, and proviral DNA was localized predominately in CD4+ and CD8+ lymphocyte subsets. FIV-14 inoculation of cats resulted in an infection characterized by seroconversion and localization of proviral DNA in CD4+ lymphocytes only. Results of this study on diverse FIV molecular clones revealed that in vitro replication efficiency of an FIV isolate in PBMC directly correlated with replication efficiency in vivo, whereas proficiency for replication in macrophages in vitro was not predictive for replication potential in vivo. Also, infection of both CD4+ and CD8+ lymphocyte subsets was associated with higher virus load in vivo. Results of the studies on these three FIV clones, which exhibited differential cell tropism, indicated a correlation between in vitro and in vivo cell tropism and virus replication.

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Kinetics of Replication of a Partially Attenuated Virus and of the Challenge Virus during a Three-Year Intersubtype Feline Immunodeficiency Virus Superinfection Experiment in Cats

Journal of Virology ◽

10.1128/jvi.73.2.1518-1527.1999 ◽

1999 ◽

Vol 73 (2) ◽

pp. 1518-1527 ◽

Cited By ~ 17

Author(s):

Mauro Pistello ◽

Donatella Matteucci ◽

Giancarlo Cammarota ◽

Paola Mazzetti ◽

Simone Giannecchini ◽

...

Keyword(s):

Feline Immunodeficiency Virus ◽

Mononuclear Cells ◽

Acute Infection ◽

Low Grade ◽

Peripheral Blood Mononuclear ◽

Subtype B ◽

Immunodeficiency Virus ◽

Attenuated Virus

ABSTRACT The effects of preinfecting cats with a partially attenuated feline immunodeficiency virus (FIV) on subsequent infection with a fully virulent FIV belonging to a different subtype were investigated. Eight specific-pathogen-free cats were preinfected with graded doses of a long-term in vitro-cultured cell-free preparation of FIV Petaluma (FIV-P, subtype A). FIV-P established a low-grade or a silent infection in the inoculated animals. Seven months later, the eight preinfected cats and two uninfected cats were challenged with in vivo-grown FIV-M2 (subtype B) and periodically monitored for immunological and virological status. FIV-P-preinfected cats were not protected from acute infection by FIV-M2, and the sustained replication of this virus was accompanied by a reduction of FIV-P viral loads in the peripheral blood mononuclear cells and plasma. However, from 2 years postchallenge (p.c.) until 3 years p.c., when the experiment was terminated, preinfected cats exhibited reduced total viral burdens, and some also exhibited a diminished decline of circulating CD4+ T lymphocytes relative to control cats infected with FIV-M2 alone. Interestingly, most of the virus detected in challenged cats at late times p.c. was of FIV-P origin, indicating that the preinfecting, attenuated virus had become largely predominant. By the end of follow-up, two challenged cats had no FIV-M2 detectable in the tissues examined. The possible mechanisms underlying the interplay between the two viral populations are discussed.

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