Immunologic Memory (Supp. of ATN 024)

This substudy will enroll volunteers from participants of ATN 024 and ATN 025. Participants
in ATN 024 are HIV-infected youths aged 12-24 years while participants in ATN 025 are
HIV-uninfected youths aged 12-17 years. These youths must also be negative for HBV core
antibody, HBV surface antigen, and HBV surface antibody to be eligible.

Blood will be drawn from study participants prior to immunization, 1 month after completion
of primary immunization and at study exit (week 72 for ATN 024 and week 76 for ATN 025) for
cytokine assays and enumeration of antibody-secreting cells. In addition, the antibody to
HBV surface antigen will be determined 2 and 4 weeks after supplemental immunization in
nonresponders to the primary series and at study exit.

This laboratory substudy is designed to evaluate some aspects of cellular immune response to
hepatitis B vaccination that are directly related to the generation and durability of
antibody response to HBV surface antigen in HIV-infected and HIV-uninfected adolescents.
Cytokine production by peripheral mononuclear cells will be determined following in-vitro
stimulation, and antibody-secreting cells will be enumerated.

Inclusion Criteria:

- Subjects that are eligible for participation in ATN 024 and ATN 025 are eligible for
ATN 048. Subjects consented for ATN 024 or ATN 025 should be consented for ATN 048 at
the same time. A written informed assent/consent must be obtained from the subject
along with written parental/legal guardian permission as determined by the local IRB
before any study-related procedures are performed.