Background: Low-cost, scalable strategies are necessary to reach the UNAIDS 2030 target of ending HIV as a public health threat. Use of treatment partners, informal caregivers selected by people living with HIV to support antiretroviral therapy adherence, is one such strategy that is included in many countries' HIV guidelines, including Botswana, a country with high HIV prevalence.

Method: From June 2021 to June 2022, we pilot tested a clinic-based treatment partner intervention ("Mopati"), including standardized language for providers to guide patients on treatment partner selection and workshops to train treatment partners on providing non-directive support to patients using a non-confrontational, non-judgmental approach. Sixty unsuppressed patients (30 per clinic) and 45 treatment partners (17 intervention, 28 control) were recruited from an intervention-control clinic matched-pair in Gaborone, Botswana.

Results: Mopati had medium-to-large effects on increasing patients' adherence, adherence self-efficacy, intrinsic adherence motivation, and perceived non-directive support from treatment partners, and decreasing treatment partner caregiver burden. Aggregate viral suppression rates significantly increased in the intervention (vs. control) clinic. Qualitative data from 14 clinic staff, 21 patients, and 16 treatment partners indicated that Mopati was viewed as effective. Providers said the guidance empowered them to be proactive in communicating about adherence; most reported using the guidance.

Conclusion: This study shows preliminary support for the use of treatment partners in HIV care, and further evidence for interventions that leverage patients' existing support. This research can inform ways to improve adherence to HIV treatment as well as the treatment of HIV-related comorbid conditions in lower-resource settings.

Trial registration: ClinicalTrials.gov Identifier: NCT04796610.

Keywords: Adherence; Antiretroviral therapy; Botswana; HIV; Motivational interviewing; Psychosocial support.