Arnold K. Fowler

A Phase I Evaluation of the Safety and Immunogenicity of Vaccination with Recombinant gp160 in Patients with Early Human Immunodeficiency Virus Infection

BACKGROUND Despite multiple antiviral humoral and cellular immune responses, infection with the human immunodeficiency virus (HIV) results in a progressively debilitating disease. We hypothesized that a more effective immune response could be generated by post-infection vaccination with HIV-specific antigens. METHODS We performed a phase I trial of the safety and immunogenicity of a vaccine prepared from molecularly cloned envelope protein, gp160, in 30 volunteer subjects with HIV infection in Walter Reed stage 1 or 2. The vaccine was administered either on days 0, 30, and 120 or on days 0, 30, 60, 120, 150, and 180. HIV-specific humoral and cellular immune responses were measured; local and systemic reactions to vaccination, including general measures of immune function, were monitored. RESULTS In 19 of the 30 subjects both humoral and cellular immunity to HIV envelope proteins increased in response to vaccination with gp160. Seroconversion to selected envelope epitopes was observed, as were new T-cell proliferative responses to gp160. Response was associated with the CD4 cell count determined before vaccination (13 of 16 subjects [81 percent] with greater than 600 cells per milliliter responded, as compared with 6 of 14 [43 percent] with less than or equal to 600 cells per milliliter; P = 0.07) and with the number of injections administered (87 percent of subjects randomly assigned to receive six injections responded, as compared with 40 percent of those assigned to three injections; P = 0.02). Local reactions at the site of injection were mild. There were no adverse systemic reactions, including diminution of general in vitro or in vivo cellular immune function. After 10 months of follow-up, the mean CD4 count had not decreased in the 19 subjects who responded, but it had decreased by 7.3 percent in the 11 who did not respond. CONCLUSIONS This gp160 vaccine is safe and immunogenic in volunteer patients with early HIV infection. Although it is too early to know whether this approach will be clinically useful, further scientific and therapeutic evaluation of HIV-specific vaccine therapy is warranted. Similar vaccines may prove to be effective for other chronic infections.

Characterization of HIV Isolates Arising After Prolonged Zidovudine Therapy

Human immunodeficiency virus type 1 (HIV-1) was isolated from five patients with late-stage disease treated with zidovudine (ZDV) for more than 1 year. Peripheral blood mononuclear cells (PBMCs) were used for all virus isolations and to assay for drug resistance. The isolates exhibited a 10− to 100-fold decrease in ZDV susceptibility compared to pretreatment isolates. Multiple clones of a 618 bp segment of the HIV reverse transcriptase gene encompassing codons 60–250 were sequenced for each isolate. The association of alterations at codons Asp67 → Asn, Lys70 → Arg, Thr215 → Phe or Tyr, and Lys219 → Gin with ZDV resistance has been previously noted (ref. 5). In this study, the most frequent alteration was Thr215 → Tyr although genotypic mixtures of Thr/Tyr and Phe/Tyr were also observed. One isolate with a Tyr215 alteration and unaltered codons at 67, 70, and 219 had high-level ZDV resistance. Alterations at codons 67, 70, and 219 did not appear to increase resistance when seen in combination with Tyr215. Virus isolates obtained from each patient by cultivation with either 0 or 4 μM ZDV were compared and found to have similar alterations at codons 67, 70, 215, and 219, although one instance of apparent in vitro selection for Tyr215 over Phe215 was observed. Assays using PBMCs for virus propagation will permit susceptibility testing of HIV isolates from most patients on antiretroviral drugs to investigate the clinical significance of drug resistance.