Jennifer Lehrman

Broad and Potent Neutralizing Antibodies from an African Donor Reveal a New HIV-1 Vaccine Target

Anti-HIV Antibodies One of the top priorities for an HIV vaccine is the ability to elicit a broadly neutralizing antibody response, which should provide the best protection against infection. In the 25 years since the discovery of HIV, very few broadly neutralizing antibodies have been identified, and those that do exist were discovered nearly two decades ago. Using a high-throughput culture system, Walker et al. (p. 285; published online 3 September) now identify two additional broadly neutralizing antibodies isolated from a clade A HIV-infected African donor. These antibodies exhibit great potency and, in contrast to other known broadly neutralizing antibodies, are able to neutralize a wide range of viruses from many different clades. The antibodies recognize a motif in the trimerized viral envelope protein that is found in conserved regions of the variable loops of the gp120 subunit. Identification of this motif provides an intriguing new target for vaccine development. High-throughput screening has revealed two new broadly neutralizing antibodies from a clade A–infected donor in Africa. Broadly neutralizing antibodies (bNAbs), which develop over time in some HIV-1–infected individuals, define critical epitopes for HIV vaccine design. Using a systematic approach, we have examined neutralization breadth in the sera of about 1800 HIV-1–infected individuals, primarily infected with non–clade B viruses, and have selected donors for monoclonal antibody (mAb) generation. We then used a high-throughput neutralization screen of antibody-containing culture supernatants from about 30,000 activated memory B cells from a clade A–infected African donor to isolate two potent mAbs that target a broadly neutralizing epitope. This epitope is preferentially expressed on trimeric Envelope protein and spans conserved regions of variable loops of the gp120 subunit. The results provide a framework for the design of new vaccine candidates for the elicitation of bNAb responses.

Human Immunodeficiency Virus Type 1 Elite Neutralizers: Individuals with Broad and Potent Neutralizing Activity Identified by Using a High-Throughput Neutralization Assay together with an Analytical Selection Algorithm

ABSTRACT The development of a rapid and efficient system to identify human immunodeficiency virus type 1 (HIV-1)-infected individuals with broad and potent HIV-1-specific neutralizing antibody responses is an important step toward the discovery of critical neutralization targets for rational AIDS vaccine design. In this study, samples from HIV-1-infected volunteers from diverse epidemiological regions were screened for neutralization responses using pseudovirus panels composed of clades A, B, C, and D and circulating recombinant forms (CRFs). Initially, 463 serum and plasma samples from Australia, Rwanda, Uganda, the United Kingdom, and Zambia were screened to explore neutralization patterns and selection ranking algorithms. Samples were identified that neutralized representative isolates from at least four clade/CRF groups with titers above prespecified thresholds and ranked based on a weighted average of their log-transformed neutralization titers. Linear regression methods selected a five-pseudovirus subset, representing clades A, B, and C and one CRF01_AE, that could identify top-ranking samples with 50% inhibitory concentration (IC50) neutralization titers of ≥100 to multiple isolates within at least four clade groups. This reduced panel was then used to screen 1,234 new samples from the Ivory Coast, Kenya, South Africa, Thailand, and the United States, and 1% were identified as elite neutralizers. Elite activity is defined as the ability to neutralize, on average, more than one pseudovirus at an IC50 titer of 300 within a clade group and across at least four clade groups. These elite neutralizers provide promising starting material for the isolation of broadly neutralizing monoclonal antibodies to assist in HIV-1 vaccine design.

A phase 1 study to evaluate the safety and immunogenicity of a recombinant HIV type 1 subtype C adeno-associated virus vaccine.

A novel prophylactic AIDS vaccine candidate, consisting of single-stranded DNA for HIV-1 subtype C gag, protease, and part of reverse transcriptase genes, enclosed within a recombinant adeno-associated virus serotype-2 protein capsid (tgAAC09) induced T cell responses and antibodies in nonhuman primates. In this randomized, dose escalation phase I trial, HIV-uninfected healthy volunteers (50 in Europe, 30 in India) received a single intramuscular injection of tgAAC09 at 3 x 10(9) DNase resistant particles (DRP) (n = 16), 3 x 10(10) DRP (n = 23), 3 x 10(11) DRP (n = 25), or placebo (n = 16). Twenty-one participants in Europe received a second (boost) dose of 3 x 10(11) DRP tgAAC09 or placebo at least 24 weeks after the first injection. The vaccine was safe and well-tolerated after initial and boost vaccination. Local and systemic reactogenicity was experienced by 13-25% of participants and was not dose related. No vaccine-related serious adverse events were reported. Modest HIV-specific T cell responses were detected in 7/64 vaccinees (40-385 SFC/10(6) PBMC), with 16% (4/25) responders in the highest dose group. All responses were to Gag epitopes. tgAAC09 appears to be safe, well-tolerated, and modestly immunogenic. Further evaluation of higher doses of tgAAC09 and boost injections is ongoing in Africa.

A Phase I Double Blind, Placebo-Controlled, Randomized Study of the Safety and Immunogenicity of Electroporated HIV DNA with or without Interleukin 12 in Prime-Boost Combinations with an Ad35 HIV Vaccine in Healthy HIV-Seronegative African Adults

Background Strategies to enhance the immunogenicity of DNA vaccines in humans include i) co-administration of molecular adjuvants, ii) intramuscular administration followed by in vivo electroporation (IM/EP) and/or iii) boosting with a different vaccine. Combining these strategies provided protection of macaques challenged with SIV; this clinical trial was designed to mimic the vaccine regimen in the SIV study. Methods Seventy five healthy, HIV-seronegative adults were enrolled into a phase 1, randomized, double-blind, placebo-controlled trial. Multi-antigenic HIV (HIVMAG) plasmid DNA (pDNA) vaccine alone or co-administered with pDNA encoding human Interleukin 12 (IL-12) (GENEVAX IL-12) given by IM/EP using the TriGrid Delivery System was tested in different prime-boost regimens with recombinant Ad35 HIV vaccine given IM. Results All local reactions but one were mild or moderate. Systemic reactions and unsolicited adverse events including laboratory abnormalities did not differ between vaccine and placebo recipients. No serious adverse events (SAEs) were reported. T cell and antibody response rates after HIVMAG (x3) prime—Ad35 (x1) boost were independent of IL-12, while the magnitude of interferon gamma (IFN-γ) ELISPOT responses was highest after HIVMAG (x3) without IL-12. The quality and phenotype of T cell responses shown by intracellular cytokine staining (ICS) were similar between groups. Inhibition of HIV replication by autologous T cells was demonstrated after HIVMAG (x3) prime and was boosted after Ad35. HIV specific antibodies were detected only after Ad35 boost, although there was a priming effect with 3 doses of HIVMAG with or without IL-12. No anti-IL-12 antibodies were detected. Conclusion The vaccines were safe, well tolerated and moderately immunogenic. Repeated administration IM/EP was well accepted. An adjuvant effect of co-administered plasmid IL-12 was not detected. Trial Registration ClinicalTrials.gov NCT01496989

A Phase 2 Study to Evaluate the Safety and Immunogenicity of a Recombinant HIV Type 1 Vaccine Based on Adeno-Associated Virus

The recombinant vaccine, tgAAC09, based on an adeno-associated virus serotype 2 (AAV2) vector encoding HIV-1 subtype C Gag, protease, and part of reverse transcriptase, induced robust T cell and antibody responses in nonhuman primates. In a previous phase I study in 80 healthy HIV-seronegative European and Indian adults, the vaccine was generally safe, well tolerated, and modestly immunogenic when administered once at doses up to 3 x 10(11) DRP. This phase II double-blind, randomized, placebo-controlled trial tested two administrations and a higher dosage of tgAAC009. Ninety-one healthy HIV-seronegative adults from three African countries were given one of three dosage levels of tgAAC09 (3 x 10(10), 3 x 10(11), or 3 x 10(12) DRP) intramuscularly, either at a 6- or 12-month interval; follow-up was 18 months. Overall, 65% and 57% of vaccine recipients experienced local and systemic signs and symptoms, respectively, most being mild. Frequency and severity were not dose related and were similar to those in placebo recipients. No vaccine-related serious adverse events were reported. Overall, HIV-specific T cell responses were detected by IFN-gamma ELISPOT in 17/69 (25%) vaccine recipients with 38% (10/26) responders in the highest dosage group. The response rate improved significantly with boosting at 6, but not 12 months, in the 3 x 10(11) and 3 x 10(12) dosage groups only. Neutralizing antibody titers to the AAV2 did not alter the frequency of immune responses to HIV. Two doses of tgAAC09 were well tolerated at the dosage levels given. Fewer than half the recipients of the highest vaccine dosage, 3 x 10(12) DRP, had T cell responses to HIV.

Acceptability and Feasibility of Repeated Mucosal Specimen Collection in Clinical Trial Participants in Kenya

Background Mucosal specimens are essential to evaluate compartmentalized immune responses to HIV vaccine candidates and other mucosally targeted investigational products. We studied the acceptability and feasibility of repeated mucosal sampling in East African clinical trial participants at low risk of HIV and other sexually transmitted infections. Methods and Findings The Kenya AIDS Vaccine Initiative (KAVI) enrolled participants into three Phase 1 trials of preventive HIV candidate vaccines in 2011–2012 at two clinical research centers in Nairobi. After informed consent to a mucosal sub-study, participants were asked to undergo collection of mucosal secretions (saliva, oral fluids, semen, cervico-vaginal and rectal), but could opt out of any collection at any visit. Specimens were collected at baseline and two additional time points. A tolerability questionnaire was administered at the final sub-study visit. Of 105 trial participants, 27 of 34 women (79%) and 62 of 71 men (87%) enrolled in the mucosal sub-study. Nearly all sub-study participants gave saliva and oral fluids at all visits. Semen was collected from about half the participating men (47–48%) at all visits. Cervico-vaginal secretions were collected by Softcup from about two thirds of women (63%) at baseline, increasing to 78% at the following visits, with similar numbers for cervical secretion collection by Merocel sponge; about half of women (52%) gave cervico-vaginal samples at all visits. Rectal secretions were collected with Merocel sponge from about a quarter of both men and women (24%) at all 3 visits, with 16% of men and 19% of women giving rectal samples at all visits. Conclusions Repeated mucosal sampling in clinical trial participants in Kenya is feasible, with a good proportion of participants consenting to most sampling methods with the exception of rectal samples. Experienced staff members of both sexes and trained counselors with standardized messaging may improve acceptance of rectal sampling.

Tolerability and acceptability of electroporation during a Phase 1 vaccine trial at two sites in Uganda and Rwanda

Background DNA vaccines are weakly immunogenic in humans and one way of increasing their immunogenicity is by administering the vaccines using electroporation (EP). This technique increases the uptake of the DNA into the cell by producing an electrical field which makes the cellular membrane more permeable. In the ongoing trial, we are using the ICHOR TriGrid Delivery system (TDS-IM) to administer bilateral injections of an HIV pDNA vaccine by EP into the medial deltoid muscles.

Uptake and tolerability of repeated mucosal specimen collection in two Phase 1 AIDS preventive vaccine trials in Kenya

Methods The Kenya AIDS Vaccine Initiative (KAVI) initiated two AIDS preventive vaccine trials in Nairobi in 2011. After informed consent for a mucosal substudy, participants were asked to provide any of several types of mucosal secretions: saliva, oral fluids, semen, cervico-vaginal and rectal. Specimens were collected at baseline, one month after final vaccination, and at the next scheduled trial visit. A tolerability questionnaire was administered at the final visit.

Electroporation (EP)-related technical errors experienced during an HIV vaccine clinical trial conducted in Rwanda and Uganda: lessons learned

Background Intracellular DNA vaccine delivery is essential for antigen expression and induction of immune response. Unfortunately, conventional intramuscular injection provides low efficiency DNA uptake and suboptimal immunogenicity. Electroporation-based DNA vaccination can enhance potency by 100-1000 fold. In this trial we used the TriGrid Delivery System by Ichor Medical Systems. We describe the electroporation technical errors that occurred during administration of an HIV pDNA vaccine in a clinical trial conducted at sites in Rwanda and Uganda and how those errors were resolved.