Immunization with cocktail of HIV-derived peptides in montanide ISA-51 is immunogenic, but causes sterile abscesses and unacceptable reactogenicity

Abstract

Background: A peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA).

Methods: Low-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, (51)Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens.

Results: 24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions.

Conclusions: The severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events.

Trial registration: ClinicalTrials.gov NCT00000886.

Figure 1. Case report of local reaction and sterile abscess formation.

Two days after the 1^st immunization, a 22 year old man in the 1 mg dose cohort developed mild tenderness over the injection site that resolved on day 4. After the 2^nd immunization was administered 28 days later, mild tenderness occurred that lasted for one day. 15 days after the 2^nd immunization a 0.25 cm asymptomatic subcutaneous nodule was detected on routine physical exam. There was no erythema at that time. Fifty days post 2^nd immunization the volunteer reported the onset of throbbing pain and that was treated with warm compresses and nonsteroidal anti-inflammatory drugs. On day 56 there was erythema and induration of 8 and 9 cm diameter over the prior injection sites, and the subject was afebrile with a WBC of 9,600/cm². On day 63 there was less pain and the area of induration was unchanged. However, the induration was less firm and the central area of erythema (A and B) was fluctuant. On day 84 there was spontaneous drainage from the lesions, from multiple fistulas on the right arm (C) and a single fistula on the left (D). The clinical course of all 4 subjects with sterile abscess formation is reviewed in Table S2.