Differences in time of virus appearance in the blood and virus-specific immune responses in intravenous and intrarectal primary SIV(mac251) infection of rhesus macaques; a pilot study

BACKGROUND: HIV-I can be transmitted by intravenous inoculation of contaminated blood or blood product or sexually through mucosal surfaces. Here we performed a pilot study in the SIV(mac251) macaque model to address whether the route of viral entry influences the kinetics of the appearance and the size of virus-specific immune in different tissue compartments. METHODS: For this purpose, of 2 genetically defined Mamu-A*01-positive macaques, 1 was exposed intravenously and the other intrarectally to the same SIV(mac251) viral stock and virus-specific CD8+ T-cells were measured within the first 12 days of infection in the blood and at day 12 in several tissues following euthanasia. RESULTS: Virus-specific CD8+ T-cell responses to Gag, Env, and particularly Tat appeared earlier in the blood of the animal exposed by the mucosal route than in the animal exposed intravenously. The magnitude of these virus-specific responses was consistently higher in the systemic tissues and GALT of the macaque exposed by the intravenous route, suggesting a higher viral burden in the tissues as reflected by the faster appearance of virus in plasma. Differences in the ability of the virus-specific CD8+ T-cells to respond in vitro to specific peptide stimulation were also observed and the greatest proliferative ability was found in the GALT of the animal infected by the intrarectal route. CONCLUSIONS: These data may suggest that the natural mucosal barrier may delay viral spreading. The consequences of this observation, if confirmed in studies with a larger number of animals, may have implications in vaccine development

Contrasting Effects of Low-Dose IL-2 on Vaccine-Boosted Simian Immunodeficiency Virus (SIV)-Specific CD4+ and CD8+ T Cells in Macaques Chronically Infected with SIVmac251

Abstract IL-2, the first cytokine discovered with T cell growth factor activity, is now known to have pleiotropic effects on T cells. For example, it can promote growth, survival, and differentiation of Ag-selected cells, or facilitate Ag-induced cell death of T cells when Ag persists, and in vivo, it is thought to contribute to the regulation of the size of adaptive T cell response. IL-2 is deficient in HIV-1 infection and has been used in the management of HIV-1-infected individuals undergoing antiretroviral therapy. In this study, we investigated how continuous low-dose IL-2 affected the CD4+ and CD8+ T cell response induced by two inoculations of a canarypox recombinant SIV-based vaccine candidate in healthy macaques chronically infected with SIVmac251. These macaques had normal levels of CD4+ T cells at the beginning of antiretroviral therapy treatment. Vaccination in the presence of IL-2 significantly augmented Gag-specific CD8+ T cell responses, but actually reduced Gag-specific CD4+ T cell responses. Although IL-2 at low doses did not change the overall concentration of circulating CD4+ or CD8+ T cells, it expanded the frequency of CD4+CD25+ T cells. Depletion of the CD4+CD25+ T cells in vitro, however, did not result in a reconstitution of Gag-specific CD4+ responses or augmentation of SIV-specific CD8+ T cell responses. Thus, we conclude that the decrease in virus-specific CD4+ T cell response may be due to IL-2-promoted redistribution of cells from the circulation, or due to Ag-induced cell death, rather than suppression by a T regulatory population

Cervicovaginal Lamina Propria Lymphocytes: Phenotypic Characterization and Their Importance in Cytotoxic T-Lymphocyte Responses to Simian Immunodeficiency Virus SIV(mac251)

Most human immunodeficiency virus (HIV) type 1 infections occur by the mucosal route. Thus, it is important to assess the immune responses to HIV in the vaginal, cervical, and rectal compartments. Here we quantitated the virus-specific CD8(+) T-cell response and characterized the phenotype of lymphocytes in the genital tracts of naive macaques, macaques acutely or chronically infected with simian immunodeficiency virus SIV(mac251), and macaques chronically infected with chimeric simian/human immunodeficiency virus SHIV(KU2.) Vaginal biopsy samples or samples obtained at the time of euthanasia were used in this analysis. The percentage of Gag-specific, tetramer-positive T cells was as high as 13 to 14% of the CD3(+) CD8(+) T-cell population in the vaginal and cervical laminae propriae of both SIV(mac251) and SHIV(KU2) chronically infected macaques. In most cases, the frequency of this response in the cervicovaginal compartment far exceeded the frequency in the blood or the draining iliac lymph node. Vaginal laminae propriae of naive macaques contained 55 to 65% CD3(+) CD8(+) cells and 28 to 34% CD3(+) CD4(+) cells, while the majority of intraepithelial cells were CD8(+) T cells (75 to 85%). For the same cells, the surface expression of CD62L was low whereas that of αEβ7 was high. No difference in the expression of CD45RA on CD8(+) T cells was observed in the chronic stage of SIV(mac251) infection. Although no decrease in the percentage of CD4(+) cells in the genital tract was observed within the first 12 days of infection, by 6 weeks from SIV(mac251) infection and thereafter the percentage of CD4(+) T cells was decreased in the laminae propriae of the vagina and cervix. Expression of CD45RA did not differ in naive and acutely SIV(mac251) infected macaques. Information on the quality and quantity of local immune responses may help in the design of vaccine strategies aimed at containing viral replication at the site of viral encounter

Emergence of Cytotoxic T Lymphocyte Escape Mutants following Antiretroviral Treatment Suspension in Rhesus Macaques Infected with SIVmac251

Structured treatment interruption (STI) of antiretroviral drugs has been proposed as an alternative approach for managing patients infected with HIV-1. While STI is thought to spare drug-related side effects and enhance the HIV-1-specific immune response, the long-lasting clinical benefit of this approach remains uncertain, particularly in patients with long-standing HIV-1 infection. Here, we investigated the basis of unabated virological replication following different STI regimens in rhesus macaques that expressed the MHC class I Mamu-A*01 molecule treated during acute and long-standing infection with SIVmac251. An amino acid change at the anchor residue within the immunodominant Mamu-A*01-restricted Gag181–189 CM9 epitope (T → A) in one of six macaques with acute SIVmac251 infection and in three of four macaques with long-standing SIVmac251 infection (T → A; T → S; S → C) was found in the majority of plasma virus. These amino acid changes have been shown to severely decrease binding of the corresponding peptides to the Mamu-A*01 molecule and, in the case of the T → A change, escape from CTL. In one macaque with long-standing SIVmac251 infection, a mutation emerged that conferred resistance to one of the antiretroviral drugs (PMPA) as well. These results provide insights into the mechanism underlying the limited capacity of repeated interruption of antiretroviral therapy as an approach to restrain viral replication. In addition, these data also suggest that interruption of therapy may be less effective in chronic infection because of preexisting immune escape and that immune escape is a risk of interruption of therapy

Both Mucosal and Systemic Routes of Immunization with the Live, Attenuated NYVAC/Simian Immunodeficiency Virus SIV(gpe) Recombinant Vaccine Result in Gag-Specific CD8(+) T-Cell Responses in Mucosal Tissues of Macaques

As most human immunodeficiency virus (HIV) infection occurs via mucosal surfaces, an important goal of vaccination may be the induction of virus-specific immune responses at mucosal sites to contain viral infection early on. Here we designed a study in macaques carrying the major histocompatibility complex class I Mamu-A∗01 molecule to assess the capacity of the highly attenuated poxvirus NYVAC/simian immunodeficiency virus (SIV) SIV(gpe) vaccine candidate administered by the intranasal, intramuscular, or intrarectal route to induce mucosal immunity. All macaques, including one naive macaque, were exposed to SIV(mac251) by the intrarectal route and sacrificed 48 h after infection. The kinetics of immune response at various time points following immunization with NYVAC/SIV(gpe) and the anamnestic response to SIV(mac251) at 48 h after challenge were assessed in blood, in serial rectal and vaginal biopsy samples, and in tissues at euthanasia with an SIV(mac) Gag-specific tetramer. In addition, at euthanasia, antigen-specific cells producing gamma interferon or tumor necrosis factor alpha from the jejunum lamina propria were quantified in all macaques. Surprisingly, antigen-specific CD8(+) T cells were found in the mucosal tissues of all immunized macaques regardless of whether the vaccine was administered by a mucosal route (intranasal or intrarectal) or systemically. In addition, following mucosal SIV(mac251) challenge, antigen-specific responses were mainly confined to mucosal tissues, again regardless of the route of immunization. We conclude that immunization with a live vector vaccine results in the appearance of CD8(+) T-cell responses at mucosal sites even when the vaccine is delivered by nonmucosal routes