Try a new search

Format these results:

Searched for:



Total Results:


A strategy for eliciting antibodies against cryptic, conserved, conformationally dependent epitopes of HIV envelope glycoprotein

Kelker, Hanna C; Itri, Vincenza R; Valentine, Fred T
BACKGROUND: Novel strategies are needed for the elicitation of broadly neutralizing antibodies to the HIV envelope glycoprotein, gp120. Experimental evidence suggests that combinations of antibodies that are broadly neutralizing in vitro may protect against challenge with HIV in nonhuman primates, and a small number of these antibodies have been selected by repertoire sampling of B cells and by the fractionation of antiserum from some patients with prolonged disease. Yet no additional strategies for identifying conserved epitopes, eliciting antibodies to these epitopes, and determining whether these epitopes are accessible to antibodies have been successful to date. The defining of additional conserved, accessible epitopes against which one can elicit antibodies will increase the probability that some may be the targets of broadly neutralizing antibodies. METHODOLOGY/PRINCIPAL FINDINGS: We postulate that additional cryptic epitopes of gp120 are present, against which neutralizing antibodies might be elicited even though these antibodies are not elicited by gp120, and that many of these epitopes may be accessible to antibodies should they be formed. We demonstrate a strategy for eliciting antibodies in mice against selected cryptic, conformationally dependent conserved epitopes of gp120 by immunizing with multiple identical copies of covalently linked peptides (MCPs). This has been achieved with MCPs representing 3 different domains of gp120. We show that some cryptic epitopes on gp120 are accessible to the elicited antibodies, and some epitopes in the CD4 binding region are not accessible. The antibodies bind to gp120 with relatively high affinity, and bind to oligomeric gp120 on the surface of infected cells. CONCLUSIONS/SIGNIFICANCE: Immunization with MCPs comprised of selected peptides of HIV gp120 is able to elicit antibodies against conserved, conformationally dependent epitopes of gp120 that are not immunogenic when presented as gp120. Some of these cryptic epitopes are accessible to the elicited antibodies
PMID: 20052405
ISSN: 1932-6203
CID: 106106

Eliciting antibodies against cryptic, conserved, conformationally dependent epitopes of HIV envelope glycoprotein gp120: A strategy [Meeting Abstract]

Kelker, HC; Itri, V; Valentine, FT
ISSN: 1742-4690
CID: 105704

Monitoring virologic responses to antiretroviral therapy in HIV-infected adults in Kenya: evaluation of a low-cost viral load assay

Sivapalasingam, Sumathi; Wangechi, Beatrice; Marshed, Fatuma; Laverty, Maura; Essajee, Shaffiq; Holzman, Robert S; Valentine, Fred
BACKGROUND: A key advantage of monitoring HIV viral load (VL) in persons receiving antiretroviral therapy (ART) is the ability to detect virologic failure before clinical deterioration or resistance occurs. Detection of virologic failure will help clarify the need for enhanced adherence counseling or a change to second- line therapy. Low-cost, locally performable alternates to expensive VL assays are needed where resources are limited. METHODOLOGY/PRINCIPAL FINDINGS: We monitored the response to 48-week ART in 100 treatment-naive Kenyan adults using a low-cost VL measurement, the Cavidi reverse transcriptase (RT) assay and gold-standard assays, Roche RNA PCR and Bayer Versant HIV-1 RNA (bDNA) assays. In Altman-Bland plots, the mean difference in viral loads between the three assays was small (<0.5 log(10) copies/mL). However, the limits of agreement between the methods exceeded the biologically relevant change of 0.5 log copies/ml. Therefore, the RT assay cannot be used interchangeably with the other assays to monitor individual patients. The RT assay was 100% sensitive in detecting viral loads of > or =400 copies/ml compared to gold-standard assays. After 24 weeks of treatment, viral load measured by the RT assay was undetectable in 95% of 65 patients with undetectable RNA PCR VL (<400 copies/ml), 90% of 67 patients with undetectable bDNA VL, and 96% of 57 patients with undetectable VL in both RNA PCR and bDNA assays. The negative predictive value of the RT assay was 100% compared to either assay; the positive predictive value was 86% compared to RNA PCR and 70% compared to bDNA. CONCLUSION: The RT assay compared well with gold standard assays. Our study highlights the importance of not interchanging viral load assays when monitoring an individual patient. Furthermore, the RT assay may be limited by low positive predictive values when used in populations with low prevalence of virologic failure
PMID: 19714253
ISSN: 1932-6203
CID: 101963

Implementation of HIV testing at 2 New York City bathhouses: from pilot to clinical service

Daskalakis, Demetre; Silvera, Richard; Bernstein, Kyle; Stein, Dylan; Hagerty, Robert; Hutt, Richard; Maillard, Alith; Borkowsky, William; Aberg, Judith; Valentine, Fred; Marmor, Michael
BACKGROUND: Commercial sex venues (e.g., bathhouses) that cater to men who have sex with men (MSM) continue to function in most urban areas. These venues present a challenge to developing strategies to prevent the spread of the human immunodeficiency virus (HIV), but they also provide opportunities for interventions to reduce the risk and rate of disease transmission. Several cities in the United States have developed programs that offer HIV testing in these venues. Similar programs have not existed before in New York City. METHODS: A pilot HIV testing program was implemented at 2 New York City bathhouses. Testing included rapid HIV testing, the use of the serologic testing algorithm for recent HIV seroconversion, and pooled plasma HIV viral load to detect and date incident and acute HIV infections. In addition to HIV tests, behavioral and demographic data were collected from 493 presumed HIV-negative participants. RESULTS: The pilot program recruited MSM who were at high risk for HIV infection. Of the 493 men tested, 20 (4%) were found to be positive for HIV, and 8 (40%) of these 20 men demonstrated evidence of acute or recent HIV infection. The program tested men often not tested in more traditional medical settings. Significant disparities were demonstrated in the testing habits of MSM who reported having sex with women and had not disclosed same-sex activities to their caregivers. CONCLUSIONS: Bathhouse-based testing for HIV infection can be implemented in New York City and would include a population of MSM who are at high risk for HIV infection. Because of the high rate of recent HIV infection, expanded testing in these venues may be a good strategy to reduce the forward transmission of HIV in this highly sexually active population
PMID: 19400690
ISSN: 1537-6591
CID: 98009

Blood Dendritic Cell Subsets in Early HIV Infection [Meeting Abstract]

Sabado, RL; O'Brien, M; Subedi, A; Taylor, E; Hutt, R; Haggerty, R; Marmor, M; Margolis, D; Valentine, F; Borrow, P; Bhardwaj, N
ISSN: 0889-2229
CID: 91419

Viral commensalism in humans? [Comment]

Blaser, Martin J; Valentine, Fred T
PMID: 18544010
ISSN: 0022-1899
CID: 79202

Effect of highly active antiretroviral therapy on viral burden in the lungs of HIV-infected subjects

Twigg Iii, Homer L; Weiden, Michael; Valentine, Fred; Schnizlein-Bick, Carol T; Bassett, Roland; Zheng, Lu; Wheat, Joseph; Day, Richard B; Rominger, Helen; Collman, Ronald G; Fox, Lawrence; Brizz, Barbara; Dragavon, Joan; Coombs, Robert W; Bucy, R Pat
BACKGROUND: Human immunodeficiency virus (HIV) is readily detectable in the lungs of infected subjects and leads to an accumulation of CD8(+) lymphocytes in the alveolar space. Although highly active antiretroviral therapy (HAART) is effective in reducing viremia, less is known about its effect on tissue compartments. The AIDS Clinical Trials Group Protocol 723 Team evaluated the effect of HAART on lung viral load and cellular constituents. METHODS: Bronchoalveolar lavage (BAL) fluid and blood were collected before initiation of HAART and again at 4 and 24 weeks after initiation of therapy. The BAL cell differential was determined, lymphocyte phenotyping was performed, and acellular BAL fluid, plasma HIV RNA load, and BAL cell and peripheral blood mononuclear cell HIV RNA and DNA loads were measured. RESULTS: HAART induced a rapid decrease in HIV that was detectable in acellular BAL fluid and a slower decrease in the HIV RNA and DNA loads in BAL cells. HAART was associated with a significant decrease in the absolute number and percentage of CD8(+) alveolar lymphocytes. There was a significant correlation between residual BAL cell DNA at 24 weeks and the absolute number of CD4(+) lymphocytes in the alveolar space. CONCLUSION: HAART is associated with a significant decrease in the pulmonary HIV burden and a return of alveolar cellular constituents to normal
PMID: 18171293
ISSN: 0022-1899
CID: 78802

A Reverse Transcriptase Assay for Early Diagnosis of Infant HIV Infection in Resource-limited Settings

Sivapalasingam, Sumathi; Patel, Usha; Itri, Vincenza; Laverty, Maura; Mandaliya, Kishorchandra; Valentine, Fred; Essajee, Shaffiq
Early diagnosis of pediatric HIV infection is confounded by persistence of maternal antibodies until 18 months, necessitating the use of expensive assays such as HIV-1 DNA PCR, an untenable option in resource-limited settings. This is the first report of a low-cost, commercial, reverse transcriptase (RT) assay for the diagnosis of HIV-1 infection in infants. RT assays were performed on 42 samples from 30 HIV-exposed Kenyan infants under 15 months of age. When correlated with serologic testing conducted after 18 months, the sensitivity, specificity, positive and negative predictive values of the RT assay were 92%, 93%, 87% and 96%. A low-cost assay for infant HIV diagnosis is urgently needed, and these results merit further evaluation.
PMID: 17562687
ISSN: 0142-6338
CID: 72999

Immunological memory after exposure to variola virus, monkeypox virus, and vaccinia virus

Sivapalasingam, Sumathi; Kennedy, Jeffrey S; Borkowsky, William; Valentine, Fred; Zhan, Ming-Xia; Pazoles, Pamela; Paolino, Anna; Ennis, Francis A; Steigbigel, Neal H
We compared cellular and humoral immunity to vaccinia virus (VV) in individuals exposed to 3 different orthopoxviruses: 154 individuals previously vaccinated with VV, 7 individuals with a history of monkeypox virus infection, and 8 individuals with a history of variola virus infection. Among individuals vaccinated >20 years prior, 9 (14%) of 66 individuals demonstrated VV-specific interferon (IFN)- gamma enzyme-linked immunospot (ELISPOT) assay responses; 21 (50%) of 42 had lymphoproliferative (LP) responses, and 29 (97%) of 30 had VV-specific neutralizing antibodies. One year after monkeypox virus infection, 6 of 7 individuals had IFN- gamma ELISPOT responses, all had VV-specific LP responses, and 3 of 7 had VV-specific neutralizing antibodies. Of 8 individuals with a history of variola virus infection, 1 had a VV-specific IFN- gamma ELISPOT response, 4 had LP responses against whole VV, 7 had LP responses against heat-denatured vaccinia antigen, and 7 had VV-specific neutralizing antibodies. Survivors of variola virus infection demonstrated VV-specific CD4 memory cell responses and neutralizing antibodies >40 years after infection
PMID: 17357051
ISSN: 0022-1899
CID: 71299

Low CD4+ T cell nadir is an independent predictor of lower HIV-specific immune responses in chronically HIV-1-infected subjects receiving highly active antiretroviral therapy

Siddique, M Atif; Hartman, Kelly E; Dragileva, Ella; Dondero, Marla; Gebretsadik, Tebeb; Shintani, Ayumi; Peiperl, Laurence; Valentine, Fred; Kalams, Spyros A
The influence of CD4(+) T cell nadirs on human immunodeficiency virus (HIV)-specific immune responses in subjects with apparently normal CD4(+) T cell counts is not known. We evaluated the frequency of HIV-1-specific immune responses in a cohort of patients with complete viral suppression (HIV-1 RNA load, <50 copies/mL) who were receiving highly active antiretroviral therapy and had a wide range of CD4(+) T cell nadirs. We found positive associations between CD4(+) T cell nadirs and the magnitude of HIV-specific CD8(+) T cell responses (P=.02) and of T cell helper responses (P=.04). These data show the CD4(+) T cell nadir to be an independent predictor of HIV-specific CD4(+) and CD8(+) T cell responses in HIV-1-infected subjects with optimal suppression of viremia
PMID: 16897665
ISSN: 0022-1899
CID: 78899