This laboratory-based substudy of an effectiveness trial of two Hepatitis B vaccines in HIV-negative youths is being done to evaluate the genetic contribution to the individualized immune response.

This laboratory-based substudy of ATN 024 and 025 will evaluate the genetic contribution to highly individualized immune responses to hepatitis B vaccine in individuals and confirm the correlation of specific human leukocyte antigen (HLA) alleles and haplotypes with Hepatitis B Virus (HVB) antibody concentrations and antibody decay kinetics in vaccinated adolescents. Approximately 5 ml of whole blood will be collected from study participants at the time of the week 28 visit or at any subsequent study visit or clinic visit following successful completion of the week 28 visit. Peripheral blood mononuclear cells will be obtained and QIA amp Blood kit will be used to extract high-quality genomic DNA for polymerase chain reaction-based genotyping by the PEII laboratory.

The study is expected to be available for the duration of the parent studies which is approximately 2 years. This study requires one visit that may be arranged to coincide with a study or routine clinic visit. There are no follow up visits.

Inclusion Criteria:

• Subjects currently enrolled in ATN 024 or ATN 025 are eligible for enrollment in ATN 052 beginning at or following completion of the week 28 visit.
• Subjects previously enrolled in ATN 024 or ATN 025 are eligible for enrollment in ATN 052, unless the subject was prematurely discontinued from the study prior to the first post-vaccination serology assessment which is performed at week 28.
• Current pregnancy is permitted.
• A signed informed assent/consent must be obtained from the subject.
• Written parental or guardian permission must be obtained where required by the institutional review board/ethics committee (IRB/EC).

Exclusion Criteria:

• Inadequate post-vaccination serology evaluation in ATN 024 or ATN 025.
• Unable to obtain informed consent and/or parental/legal guardian permission where required by the local IRB/EC.

All subjects who are currently enrolled or have completed ATN 024 or ATN 025 are eligible for participation on this substudy with the exception of those who were discontinued from ATN 024 or ATN 025 prior to completing the first post-vaccination serology (week 28) visit.

Participants in ATN 024 are HIV-infected youths aged 12 to 24 years, while participants in ATN 025 are HIV-uninfected youths aged 12 to17 years, thus participants in this substudy will be HIV-infected and uninfected youth aged 12 to 24 years. All eligible youths must be negative for HBV core antibody, HBV surface antigen, and HBV surface antibody at the time of enrollment in to the parent protocols.