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1.  Antiviral Cytotoxic T Lymphocytes in Vaginal Mucosa of Simian Immunodeficiency Virus-Infected-Rhesus Macaques1 
The mucosal immune system of the female reproductive tract is of central importance for protection against sexually transmitted diseases, including HIV; however, this arm of the immune system remains poorly understood. Antiviral CTL responses never have been documented in the genital tract and the role of CTL in this anatomic site is unknown. In this study, CD8+ intraepithelial lymphocytes (IEL) in the vaginas of six simian immunodeficiency virus (SIV)-infected female rhesus macaques were identified by immunohistochemistry to be CD2+ and TCR β-chain+. In addition, the majority of CD8+ IEL contained TIA-1+ cytoplasmic granules that are associated with CTL activity. CD8+ T cells were isolated from the vaginal epithelium and submucosa and amplified by limiting dilution in the presence of feeder cells. SIV p55gag and/or gp16Oenv-specific lysis was detected in cultures of vaginal epithelial but not submucosal CD8+ T lymphocytes. Estimated SIV-specific precursor CTL frequencies were higher in the vaginal CD8+ IEL population of chronically infected monkeys than in the same cells from acutely infected monkeys or a naive control monkey. These results provide the first demonstration that antiviral CTL are present in the vaginal epithelium, and suggest that a vaccine may be able to generate anti-HIV CTL in the genital mucosa.
PMCID: PMC3549272  PMID: 7499875
2.  Modified vaccinia Ankara expressing HIVA antigen stimulates HIV-1-specific CD8 T cells in ELISpot assays of HIV-1 exposed infants☆ 
Vaccine  2005;23(38):4711-4719.
Recombinant modified vaccinia virus Ankara expressing HIV-1 antigens (MVA.HIVA) was used in ELISpot assays to monitor HIV-1-specific T cell responses in infants. Responses to MVA.HIVA and HIV-1 peptides were examined in 13 infected and 81 exposed uninfected infants in Nairobi, Kenya. Responses to MVA.HIVA (38%) and peptide stimulation (38%) were similar in frequency (p = 1.0) and magnitude (mean 176 versus 385 HIVSFU/106, p = 0.96) in HIV-1 infected infants. In exposed uninfected infants, MVA.HIVA detected more positive responses and higher magnitude responses as compared to peptide. MVA.HIVA ELISpot is a sensitive method for quantification of HIV-1-specific CD8+ T cell responses in HIV-1 exposed infants. These results demonstrate the relevance of HIV-1 clade A consensus-derived immunogen HIVA for the viruses currently circulating in Nairobi.
PMCID: PMC3382083  PMID: 16043269
Enzyme-linked immunospot assay; Exposed seronegatives; Mother to child transmission
3.  Breast Milk α-Defensins Are Associated with HIV Type 1 RNA and CC Chemokines in Breast Milk But Not Vertical HIV Type 1 Transmission 
α-Defensins are proteins exhibiting in vitro anti-HIV-1 activity that may protect against mother-to-child transmission of HIV-1 via breast milk. Correlates of α-defensins in breast milk and transmission risk were determined in a cohort of HIV-1-infected pregnant women in Nairobi followed for 12 months postpartum with their infants. Maternal blood was collected antenatally and at delivery for HIV-1 viral load and infant HIV-1 infection status was determined <48 h after birth and at months 1, 3, 6, 9, and 12. Breast milk specimens collected at month 1 were assayed for α-defensins, HIV-1 RNA, subclinical mastitis, and CC and CXC chemokines. We detected α-defensins in breast milk specimens from 108 (42%) of 260 HIV-1-infected women. Women with detectable α-defensins (≥50 pg/ml) had a median concentration of 320 pg/ml and significantly higher mean breast milk HIV-1 RNA levels than women with undetectable α-defensins (2.9 log10 copies/ml versus 2.5 log10 copies/ml, p = 0.003). Increased α-defensins concentrations in breast milk were also associated with subclinical mastitis (Na+/K+ ratio > 1) and increased breast milk chemokine levels. Overall, 40 (15%) infants were HIV-1 uninfected at birth and subsequently acquired HIV-1. There was no significant association between month 1 α-defensins and risk of HIV-1 transmission. In conclusion, α-defensins were associated with breast milk HIV-1 viral load, chemokine levels, and subclinical mastitis, all of which may alter risk of infant HIV-1 acquisition. Despite these associations there was no significant relationship between breast milk α-defensins and mother-to-child transmission, suggesting a complex interplay between breast milk HIV-1, inflammation, and antiinfective factors.
PMCID: PMC3382116  PMID: 17331027
4.  Human Leukocyte Antigen (HLA) B*18 and Protection against Mother-to-Child HIV Type 1 Transmission 
Human leukocyte antigen (HLA) molecules regulate the cellular immune system and may be determinants of infant susceptibility to human immunodeficiency virus type 1 (HIV-1) infection. Molecular HLA typing for class I alleles was performed on infants followed in a Kenyan perinatal cohort. Early HIV-1 infection status was defined as infection occurring at birth or month 1, while late infection via breast milk was defined as first detection of HIV-1 after 1 month of age. Likelihood ratio tests based on a proportional hazards model adjusting for maternal CD4 T cell count and HIV-1 viral load at 32 weeks of gestation were used to test associations between infant allelic variation and incident HIV-1 infection. Among 433 infants, 76 (18%) were HIV-1 infected during 12 months of follow-up. HLA B*18 was associated with a significantly lower risk of early HIV-1 transmission [relative risk (RR) = 0.26; 95% confidence interval (CI) 0.04–0.82], and none of the 24 breastfeeding infants expressing HLA B*18 who were uninfected at month 1 acquired HIV-1 late via breast milk. We observed a trend toward increased early HIV-1 acquisition for infants presenting HLA A*29 (RR = 2.0; 95% CI 1.0–3.8) and increased late HIV-1 acquisition via breast milk for both Cw*07 and Cw*08 (RR = 4.0; 95% CI 1.0–17.8 and RR = 7.2; 95% CI 1.2–37.3, respectively). HLA B*18 may protect breast-feeding infants against both early and late HIV-1 acquisition, a finding that could have implications for the design and monitoring of HIV-1 vaccines targeting cellular immune responses against HIV-1.
PMCID: PMC3380108  PMID: 15307911
5.  Longitudinal Assessment of Human Immunodeficiency Virus Type 1 (HIV-1)-Specific Gamma Interferon Responses during the First Year of Life in HIV-1-Infected Infants 
Journal of Virology  2005;79(13):8121-8130.
Human immunodeficiency virus type 1 (HIV-1) infection results in different patterns of viral replication in pediatric compared to adult populations. The role of early HIV-1-specific responses in viral control has not been well defined, because most studies of HIV-1-infected infants have been retrospective or cross-sectional. We evaluated the association between HIV-1-specific gamma interferon (IFN-γ) release from the cells of infants of 1 to 3 months of age and peak viral loads and mortality in the first year of life among 61 Kenyan HIV-1-infected infants. At 1 month, responses were detected in 7/12 (58%) and 6/21 (29%) of infants infected in utero and peripartum, respectively (P = 0.09), and in ∼50% of infants thereafter. Peaks of HIV-specific spot-forming units (SFU) increased significantly with age in all infants, from 251/106 peripheral blood mononuclear cells (PBMC) at 1 month of age to 501/106 PBMC at 12 months of age (P = 0.03), although when limited to infants who survived to 1 year, the increase in peak HIV-specific SFU was no longer significant (P = 0.18). Over the first year of life, infants with IFN-γ responses at 1 month had peak plasma viral loads, rates of decline of viral load, and mortality risk similar to those of infants who lacked responses at 1 month. The strength and breadth of IFN-γ responses at 1 month were not significantly associated with viral containment or mortality. These results suggest that, in contrast to HIV-1-infected adults, in whom strong cytotoxic T lymphocyte responses in primary infection are associated with reductions in viremia, HIV-1-infected neonates generate HIV-1-specific CD8+-T-cell responses early in life that are not clearly associated with improved clinical outcomes.
PMCID: PMC1143755  PMID: 15956557
6.  Protection against Simian Immunodeficiency Virus Vaginal Challenge by Using Sabin Poliovirus Vectors 
Journal of Virology  2001;75(16):7435-7452.
Here we provide the first report of protection against a vaginal challenge with a highly virulent simian immunodeficiency virus (SIV) by using a vaccine vector. New poliovirus vectors based on Sabin 1 and 2 vaccine strain viruses were constructed, and these vectors were used to generate a series of new viruses containing SIV gag, pol, env, nef, and tat in overlapping fragments. Two cocktails of 20 transgenic polioviruses (SabRV1-SIV and SabRV2-SIV) were inoculated into seven cynomolgus macaques. All monkeys produced substantial anti-SIV serum and mucosal antibody responses. SIV-specific cytotoxic T-lymphocyte responses were detected in three of seven monkeys after vaccination. All 7 vaccinated macaques, as well as 12 control macaques, were challenged vaginally with pathogenic SIVmac251. Strikingly, four of the seven vaccinated animals exhibited substantial protection against the vaginal SIV challenge. All 12 control monkeys became SIV positive. In two of the seven SabRV-SIV-vaccinated monkeys we found no virological evidence of infection following challenge, indicating that these two monkeys were completely protected. Two additional SabRV-SIV-vaccinated monkeys exhibited a pronounced reduction in postacute viremia to <103 copies/ml, suggesting that the vaccine elicited an effective cellular immune response. Three of six control animals developed clinical AIDS by 48 weeks postchallenge. In contrast, all seven vaccinated monkeys remained healthy as judged by all clinical parameters. These results demonstrate the efficacy of SabRV as a potential human vaccine vector, and they show that the use of a vaccine vector cocktail expressing an array of defined antigenic sequences can be an effective vaccination strategy in an outbred population.
PMCID: PMC114979  PMID: 11462016
7.  Bystander Sensitization to Activation-Induced Cell Death as a Mechanism of Virus-Induced Immune Suppression 
Journal of Virology  2000;74(8):3650-3658.
Viral infections which induce strong T-cell responses are often characterized by a period of transient immunodeficiency associated with the failure of host T cells to proliferate in response to mitogens or to mount memory recall responses to other antigens. During acute infections, most of the activated, proliferating virus-specific T cells are sensitized to undergo apoptosis on strong T-cell receptor (TCR) stimulation, but it has not been known why memory T cells not specific for the virus fail to proliferate on exposure to their cognate antigen. Using a lymphocytic choriomeningitis virus (LCMV) infection model in which LCMV-immune Thy 1.1+ splenocytes are adoptively transferred into Thy 1.2+ LCMV carrier mice, we demonstrate here that T cells clearly defined as not specific for the virus are sensitized to undergo activation-induced cell death on TCR stimulation in vitro. This bystander sensitization was in part dependent on the expression of Fas ligand (FasL) on the activated virus-specific cells and gamma interferon (IFN-γ) receptor expression on the bystander T cells. We propose that FasL from highly activated antiviral T cells may sensitize IFN-γ-conditioned T cells not specific for the virus to undergo apoptosis rather than to proliferate on encountering antigen. This may in part explain the failure of memory T cells to respond to recall antigens during acute and persistent viral infections.
PMCID: PMC111875  PMID: 10729141
8.  Mucosal Immunization of Cynomolgus Macaques with Two Serotypes of Live Poliovirus Vectors Expressing Simian Immunodeficiency Virus Antigens: Stimulation of Humoral, Mucosal, and Cellular Immunity† 
Journal of Virology  1999;73(11):9485-9495.
Poliovirus live virus vectors are a candidate recombinant vaccine system. Previous studies using this system showed that a live poliovirus vector expressing a foreign antigen between the structural and nonstructural proteins generates both antibody and cytotoxic T-lymphocyte responses in mice. Here we describe a novel in vitro method of cloning recombinant polioviruses involving a hybrid-PCR approach. We report the construction of recombinant vectors of two different serotypes of poliovirus-expressing simian immunodeficiency virus (SIV) antigens and the intranasal and intravenous inoculations of four adult cynomolgus macaques with these poliovirus vectors expressing the SIV proteins p17gag and gp41env. All macaques generated a mucosal anti-SIV immunoglobulin A (IgA) response in rectal secretions. Two of the four macaques generated mucosal antibody responses detectable in vaginal lavages. Strong serum IgG responses lasting for at least 1 year were detected in two of the four monkeys. SIV-specific T-cell lymphoproliferative responses were detected in three of the four monkeys. SIV-specific cytotoxic T lymphocytes were detected in two of the four monkeys. This is the first report of poliovirus-elicited vaginal IgA or cytotoxic T lymphocytes in any naturally infectable primate, including humans. These findings support the concept that a live poliovirus vector is a potentially useful delivery system that elicits humoral, mucosal, and cellular immune responses against exogenous antigens.
PMCID: PMC112983  PMID: 10516057
9.  Apoptotic Regulation of T Cells and Absence of Immune Deficiency in Virus-Infected Gamma Interferon Receptor Knockout Mice 
Journal of Virology  1998;72(10):7815-7821.
Acute viral infections often induce a transient period of immune deficiency in which the host’s T cells fail to proliferate in response to T-cell mitogens and fail to make an antigen-specific memory recall response. This has been associated with the enhanced sensitivity of these highly activated T cells to undergo apoptosis, or activation-induced cell death (AICD), upon T-cell receptor ligation. Here we show that gamma interferon receptor-deficient (IFN-γ R−/−) mice mount a T-cell response to lymphocytic choriomeningitis virus (LCMV) infection but fail to undergo the transient immune deficiency. Instead, their T cells were hyperproliferative and relatively, but not completely, resistant to AICD. The immune response returned to homeostasis, but with delayed kinetics, in parallel with delayed clearance of the virus. Wild-type mice receiving high doses of disseminating LCMV Clone 13 are known to undergo clonal exhaustion of their virus-specific cytotoxic T lymphocytes (CTL). To determine whether this process was mediated by AICD associated with IFN-γ or with Fas-Fas ligand interactions, LCMV-specific precursor CTL frequencies were examined in LCMV Clone 13-infected IFN-γ R−/− or lpr (Fas-deficient) mice. In both instances, viral persistence was established and CTL precursors were greatly eliminated. This finding indicates that clonal exhaustion of CTL does not require IFN-γ or Fas, even though both molecules influence AICD and the transient immune deficiency seen in the LCMV infection.
PMCID: PMC110096  PMID: 9733817

Results 1-9 (9)