Intra- and inter-clade cross-reactivity by HIV-1 Gag specific T-cells reveals exclusive and commonly targeted regions: implications for current vaccine trials.

The genetic diversity of HIV-1 across the globe is a major challenge for developing an HIV vaccine. To facilitate immunogen design, it is important to characterize clusters of commonly targeted T-cell epitopes across different HIV clades. To address this, we examined 39 HIV-1 clade C infected individuals for IFN-γ Gag-specific T-cell responses using five sets of overlapping peptides, two sets matching clade C vaccine candidates derived from strains from South Africa and China, and three peptide sets corresponding to consensus clades A, B, and D sequences. The magnitude and breadth of T-cell responses against the two clade C peptide sets did not differ, however clade C peptides were preferentially recognized compared to the other peptide sets. A total of 84 peptides were recognized, of which 19 were exclusively from clade C, 8 exclusively from clade B, one peptide each from A and D and 17 were commonly recognized by clade A, B, C and D. The entropy of the exclusively recognized peptides was significantly higher than that of commonly recognized peptides (p = 0.0128) and the median peptide processing scores were significantly higher for the peptide variants recognized versus those not recognized (p = 0.0001). Consistent with these results, the predicted Major Histocompatibility Complex Class I IC(50) values were significantly lower for the recognized peptide variants compared to those not recognized in the ELISPOT assay (p<0.0001), suggesting that peptide variation between clades, resulting in lack of cross-clade recognition, has been shaped by host immune selection pressure. Overall, our study shows that clade C infected individuals recognize clade C peptides with greater frequency and higher magnitude than other clades, and that a selection of highly conserved epitope regions within Gag are commonly recognized and give rise to cross-clade reactivities.

Safety and immunogenicity study of Multiclade HIV-1 adenoviral vector vaccine alone or as boost following a multiclade HIV-1 DNA vaccine in Africa.

BACKGROUND: We conducted a double-blind, randomized, placebo-controlled Phase I study of a recombinant replication-defective adenovirus type 5 (rAd5) vector expressing HIV-1 Gag and Pol from subtype B and Env from subtypes A, B and C, given alone or as boost following a DNA plasmid vaccine expressing the same HIV-1 proteins plus Nef, in 114 healthy HIV-uninfected African adults. METHODOLOGY/PRINCIPAL FINDINGS: Volunteers were randomized to 4 groups receiving the rAd5 vaccine intramuscularly at dosage levels of 1×10(10) or 1×10(11) particle units (PU) either alone or as boost following 3 injections of the DNA vaccine given at 4 mg/dose intramuscularly by needle-free injection using Biojector® 2000. Safety and immunogenicity were evaluated for 12 months. Both vaccines were well-tolerated. Overall, 62% and 86% of vaccine recipients in the rAd5 alone and DNA prime - rAd5 boost groups, respectively, responded to the HIV-1 proteins by an interferon-gamma (IFN-γ) ELISPOT. The frequency of immune responses was independent of rAd5 dosage levels. The highest frequency of responses after rAd5 alone was detected at 6 weeks; after DNA prime - rAd5 boost, at 6 months (end of study). At baseline, neutralizing antibodies against Ad5 were present in 81% of volunteers; the distribution was similar across the 4 groups. Pre-existing immunity to Ad5 did not appear to have a significant impact on reactogenicity or immune response rates to HIV antigens by IFN-γ ELISPOT. Binding antibodies against Env were detected in up to 100% recipients of DNA prime - rAd5 boost. One volunteer acquired HIV infection after the study ended, two years after receipt of rAd5 alone. CONCLUSIONS/SIGNIFICANCE: The HIV-1 rAd5 vaccine, either alone or as a boost following HIV-1 DNA vaccine, was well-tolerated and immunogenic in African adults. DNA priming increased the frequency and magnitude of cellular and humoral immune responses, but there was no effect of rAd5 dosage on immunogenicity endpoints. TRIAL REGISTRATION: ClinicalTrials.gov NCT00124007.

Safety & immunogenicity of tgAAC09, a recombinant adeno-associated virus type 2 HIV-1 subtype C vaccine in India.

BACKGROUND & OBJECTIVES: A phase 1 trial of adeno-associated virus based HIV-1 subtype C vaccine (tgAAC09) was conducted at two sites in Germany and Belgium and one site in India. This paper reports the safety and immunogenicity of tgAAC09 in healthy adult Indian volunteers. METHODS: Between January 2005 and December 2006, 30 consenting volunteers were enrolled in the placebo controlled double-blind dose-escalation trial [3x10(9), 3x10(10) and 3x10(11) DNase resistant particles (DRPs)/ml]. Single injection of the candidate vaccine was administered to ten volunteers randomized in 8:2 ratio in vaccine and placebo arms at each dosage level. RESULTS: The mean age of study volunteers (16 men and 14 women) was 34 yr. Six local reactogenicity events and 14 systemic reactogenicity events like malaise, fever, headache and myalgia were reported, both were dose-dependent. The difference between the adverse events reported by vaccine and placebo recipients (79 and 67%) was not significant. A modest IFN-gamma ELISPOT response [248 spot forming units (SFU)/million cells] was detected in one volunteer from high dose group and low response (56 and 75 SFU/million cells) in two volunteers in low and mid-dose groups. A post-vaccination dose-dependent increase was observed in anti AAV2 neutralizing titres. None of the volunteers showed a positive antibody response to HIV-1. INTERPRETATION & CONCLUSIONS: The trial was a benchmark in phase I clinical evaluation of HIV candidate vaccines in India. The vaccine was generally well tolerated and raised no safety concerns. The vaccine was found to be weakly immunogenic. It is essential to understand the role of pre-existing immunity against vectors and significance of evaluation in a prime-boost strategy.

A Phase 1 study to evaluate the safety and immunogenicity of a recombinant HIV type 1 subtype C-modified vaccinia Ankara virus vaccine candidate in Indian volunteers.

A recombinant modified vaccinia Ankara virus vaccine candidate (TBC-M4) expressing HIV-1 subtype C env, gag, tat-rev, and nef-RT genes was tested in a randomized, double-blind, dose escalation Phase I trial in 32 HIV-uninfected healthy volunteers who received three intramuscular injections of TBC-M4 at 0, 1, and 6 months of 5 x 10(7) plaque-forming units (pfu) (low dosage, LD) (n = 12) or 2.5 x 10(8) pfu (high dosage, HD) (n = 12) or placebo (n = 8). Local and systemic reactogenicity was experienced by approximately 67% and 83% of vaccine recipients, respectively. The reactogenicity events were mostly mild in severity. Severe but transient systemic reactogenicity was seen in one volunteer of the HD group. No vaccine-related serious adverse events or events suggesting perimyocarditis were seen. A higher frequency of local reactogenicity events was observed in the HD group. Cumulative HIV-specific IFN-gamma ELISPOT responses were detected in frozen PBMCs from 9/11 (82%), 12/12 (100%), and 1/8 (13%) volunteers after the third injection of the LD, HD, and placebo groups, respectively. Most of the responses were to gag and env proteins (maximum of 430 SFU/10(6) PBMCs) persisting across multiple time points. HIV-specific ELISA antibody responses were detected in 10/11, 12/12, and 0/8 volunteers post-third vaccination, in the LD, HD, and placebo groups, respectively. No neutralizing activity against HIV-1 subtype C isolates was detected. TBC-M4 appears to be generally safe and well-tolerated. The immune response detected was dose dependent, modest in magnitude, and directed mostly to env and gag proteins, suggesting further evaluation of this vaccine in a prime-boost regimen.

Concordant proficiency in measurement of T-cell immunity in human immunodeficiency virus vaccine clinical trials by peripheral blood mononuclear cell and enzyme-linked immunospot assays in laboratories from three continents.

The gamma interferon (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay is used routinely to evaluate the potency of human immunodeficiency virus (HIV) vaccine candidates and other vaccine candidates. In order to compare candidates and pool data from multiple trial laboratories, validated standardized methods must be applied across laboratories. Proficiency panels are a key part of a comprehensive quality assurance program to monitor inter- and intralaboratory performance, as well as assay performance, over time. Seven International AIDS Vaccine Initiative-sponsored trial sites participated in the proficiency panels described in this study. At each laboratory, two operators independently processed identical sample sets consisting of frozen peripheral blood mononuclear cell (PBMC) samples from different donors by using four blind stimuli. PBMC recovery and viability after overnight resting and the IFN-gamma ELISPOT assay performance were assessed. All sites demonstrated good performance in PBMC thawing and resting, with a median recovery of 78% and median viability of 95%. The laboratories were able to detect similar antigen-specific T-cell responses, ranging from 50 to >3,000 spot-forming cells per million PBMC. An approximate range of a half log in results from operators within or across sites was seen in comparisons of antigen-specific responses. Consistently low background responses were seen in all laboratories. The results of these proficiency panels demonstrate the ability of seven laboratories, located across three continents, to process PBMC samples and to rank volunteers with differential magnitudes of IFN-gamma ELISPOT responses. These findings also illustrate the ability to standardize the IFN-gamma ELISPOT assay across multiple laboratories when common training methods, reagents such as fetal calf serum, and standard operating procedures are adopted. These results are encouraging for laboratories that are using cell-based immunology assays to test HIV vaccines and other vaccines.

Clinical performance of an in-house real-time RT-PCR assay using a fluorogenic LUX primer for quantitation of human immunodeficiency virus type-1 (HIV-1).

The South African National Antiretroviral Treatment Guideline recommends the use of HIV viral load assays for routine monitoring of HIV-1 positive patients on Highly Active Antiretroviral Therapy (HAART). Approved commercial HIV-1 viral load assays are expensive for developing countries where a large number of patients are treated in the public sector. The evaluation of an in-house HIV-1 viral load assay (LUX assay) is described using 458 plasma specimens. Good specificity of the LUX assay was demonstrated using 50 seronegative plasma specimens. A group of 142 HIV-1 positive patients was used to assess the agreement between the LUX assay and the COBAS Amplicor assay. An intra class correlation (ICC) coefficient of 0.85 (CI 95%) indicated good agreement between the assays. The Bland-Altman model showed good agreement between the assays for approximately 87% of the results (mean 0.03 [-1.26; 1.32], CI 95%). In a cohort of 55 patients followed-up longitudinally the LUX assay showed similar declines in viral load to the COBAS Amplicor assay in response to therapy. Viral rebound was detected in 5 patients out of 55 by both assays. Thus, the LUX assay compares well to the gold standard and represents an affordable alternative for high volume testing in resource limited settings.

Fluorogenic LUX primer for quantitation of HIV-1 by real-time RT-PCR.

Measurement of HIV-1 viral load in plasma is an important marker of disease progression and efficacy of antiretroviral therapy. Real-time polymerase chain reaction (PCR) offers an opportunity to develop more affordable alternative viral load assays. This article reports on the development of a novel real-time reverse-transcriptase (RT)-PCR assay for quantitation of HIV-1 RNA copies. This assay utilizes the LightCycler (version 2) real-time PCR platform and light upon extension (LUX) primer for specific detection of amplicons. An external standard (ES) for quantitation of viral RNA represents an in vitro transcribed RNA. The LUX assay shows a wide linear (R2 = 0.99) dynamic range from 4 x 10(6) to 4 x 10(2) copies/mL. Analytical sensitivity of the assay is 4 x 10(2) copies/mL of ES RNA. Intra- and inter-assay variability of the LUX assay was less than 0.5log(10) copies of ES RNA (i.e., no clinically significant variability was found). Virology quality assurance (VQA) HIV-1 RNA copy controls were used to validate ES and preliminarily evaluate the assay performance. This feasibility study demonstrated that the LUX assay is sensitive, reproducible, and compares well to the Roche Amplicor tests used for characterization of the RNA copy controls. These results suggest further evaluation of the LUX assay using a large cohort of well-characterized samples from HIV-1 positive individuals.

Dried blood spots improve access to HIV diagnosis and care for infants in low-resource settings.

Effective health care delivery to the majority of perinatally exposed infants worldwide, including those enrolled in prevention of mother-to-child transmission programs, is hampered by lack of access to an HIV diagnosis in infancy. Dried blood spot collection from young infants for centralized HIV polymerase chain reaction (PCR) testing is attainable in low-resource settings, provided PCR methodology suitable for routine laboratory service is available. The accuracy of the Roche Amplicor HIV-1 DNA test version 1.5 (Branchburg, NJ) performed on dried blood spots collected prospectively on ordinary Whatman filter paper from a cohort of 300 6-week-old infants born to HIV-infected women in Johannesburg, South Africa, was assessed. Anonymous analysis of the blood spots using a unique DNA extraction procedure was performed in a routine diagnostic laboratory and the results compared with HIV DNA and RNA PCR liquid blood tests at age 6 weeks, and the HIV status of the infant. Dried blood spots were available for 288 infants (96%) of whom 25 (8.7%) were HIV infected. The Roche Amplicor assay yielded a sensitivity of 100% and a specificity of 99.6%. HIV DNA PCR tests on dried blood spots have the potential to improve health care delivery to HIV-affected children in low-resource settings right now.

Affordable diagnosis of human immunodeficiency virus infection in infants by p24 antigen detection.

The expense of PCR testing limits diagnosis of HIV infection in infancy in low resource settings. The ultrasensitive p24 antigen assay has been proposed as an accurate substitute; however, its ability to detect different HIV viral subtypes remains to be determined. A sensitivity of 98.1% and specificity of 98.7% was obtained testing 203 samples from 24 HIV-infected and 66 uninfected infants born to HIV subtype C-infected women.