This substudy is a prospective, observational, open-label, randomised study within the MARCH study. The purpose of this substudy is to investigate the changes in cerebral function parameters at 5 timepoints over 96 weeks of the three different treatment arms within the MARCH study. The investigators hypothesise that there will be improvements in cerebral function in those patients randomised, as part of the parent study, into the maraviroc arms.

the assessments in this CNS substudy will include:

1. Neurocognitive function as assessed by a computerised testing battery called CogState;
2. changes in cerebral metabolites as measured via 1H Magnetic Resonance Spectroscopy (1H-MRS)

In those randomised to the maraviroc arms (arms 2 and 3) there is an optional Lumbar puncture at week 48. The cerebrospinal fluid will be used to measure maraviroc levels and an ultrasensitive CSF HIV-1 viral load. These results will be matched with levels in the plasma.

this is detailed above, this is a substudy of MARCH

Inclusion Criteria:

• Provision of written, informed consent for participation in the substudy
• Enrolled into the substudy either at or before the week 0 visit of the main study

Exclusion Criteria:

• Pre-existing CNS diseases
• Recent head injury (past three months)
• Current history of major depression or psychosis

participants in the MARCH main study who are eligible for the CNS substudy and provide written informed consent for participation