This is an observational, prospective cohort study to describe the demographic, clinical, immunologic, and virologic characteristics of HIV-infected children at participating clinical sites in Latin American countries. Enrollment in this study will consist of approximately 500 HIV-infected children in two cohorts who acquired HIV infection through mother-to-child transmission (MTCT). The first group will be a static cohort consisting of HIV-infected children who were five years of age or younger when previously enrolled into the NISDI Pediatric Protocol. The second cohort will be a dynamic cohort of prospectively enrolled, HIV-infected children who are five years of age or younger. We will characterize complications from both the disease and its treatments. Subjects will be evaluated every six months for approximately five years and assessments of growth, morbidity, disease progression and mortality will be made.

This is an observational, prospective cohort study to describe the demographic, clinical, immunologic, and virologic characteristics of HIV-infected children at participating clinical sites in Latin American countries. Enrollment in this study will consist of approximately 500 HIV-infected children in two cohorts who acquired HIV infection through mother-to-child transmission (MTCT). The first group will be a static cohort consisting of HIV-infected children who were five years of age or younger when previously enrolled into the NISDI Pediatric Protocol. The second cohort will be a dynamic cohort of prospectively enrolled, HIV-infected children who are five years of age or younger. We will characterize complications from both the disease and its treatments. Subjects will be evaluated every six months for approximately five years and assessments of growth, morbidity, disease progression and mortality will be made.

• INCLUSION CRITERIA:

Static Cohort:

1. Previous participation in a NISDI Protocol

2. Less then 6 years of age (before their 6th birthday) at the time of enrollment into the NISDI Pediatric Protocol

3. HIV-infected

4. HIV infection must be documented in the medical records by:

   1. For children less than 18 months old when tested, two or more of the following (separate determinations on separate blood specimens):

      • Positive HIV culture
      • Positive HIV DNA PCR
      • Positive neutralizable p24 antigen
      • Quantitative HIV RNA greater than or equal to 10,000 copies/ml

   2. For children greater than or equal to 18 months old when tested, two or more of the following (separate determinations on separate blood specimens):

      • Reactive test for HIV antibody in a sample obtained at greater than or equal to 15 months of age with confirmatory test by Western Blot or Immunofluorescence assay
      • Positive HIV culture
      • Positive HIV DNA PCR
      • Positive neutralizable p24 antigen
      • Quantitative HIV RNA greater than or equal to 1,000 copies/ml

5. Documentation of maternal HIV infection by country appropriate National Guidelines

6. Signed informed consent from parent or legal guardian. An informed assent document will be provided for children 8 years of age or older when appropriate.

7. Subjects must be able to be followed at a participating clinical site.

8. Subjects may be co-enrolled in clinical trials for treatment of HIV infection, opportunistic infections, or other HIV-related effects.

Dynamic cohort:

1. HIV-infected less then 6 years of age (before their 6th birthday) at enrollment into this protocol

2. HIV infection documented by:

   1. For children <18 months old when tested, two or more of the following (separate determinations on separate blood specimens):

      • Positive HIV culture
      • Positive HIV DNA PCR
      • Positive neutralizable p24 antigen
      • Quantitative HIV RNA greater than or equal to 10,000 copies/ml

   2. For children greater than or equal to 18 months old when tested, two or more of the following (separate determinations on separate blood specimens):

      • Reactive test for HIV antibody in a sample obtained at greater than or equal to 15 months of age with confirmatory test by Western Blot or Immunofluorescence assay
      • Positive HIV culture
      • Positive HIV DNA PCR
      • Positive neutralizable p24 antigen
      • Quantitative HIV RNA greater than or equal to 1,000 copies/ml

3. Documentation of maternal HIV infection by country appropriate National Guidelines

4. Signed informed consent from parent or legal guardian. An informed assent document will be provided for children 8 years of age or older when appropriate.

5. Subjects must be able to be followed at a participating clinical site

6. Subjects may be co enrolled in clinical trials for treatment of HIV infection, opportunistic infections, or other HIV related effects

EXCLUSION CRITERIA:

1. Children who are born to an HIV infected mother, but are uninfected or of indeterminate HIV infection status
2. Children who are orphans without legal guardians or are wards of the state

500 HIV-infected children in two cohorts who acquired HIV infection through mother-to-child transmission (MTCT). The first group will be a static cohort consisting of HIV-infected children who were five years of age or younger when previously enrolled into the NISDI Pediatric Protocol. The second cohort will be a dynamic cohort of prospectively enrolled, HIV-infected children who are five years of age or younger. We will characterize complications from both the disease and its treatments. Subjects will be evaluated every six months for approximately five years and assessments of growth, morbidity, disease progression and mortality will be made.