Antibody-based CCR5 blockade protects Macaques from mucosal SHIV transmission

In the absence of a prophylactic vaccine, the use of antiretroviral therapy (ART) as pre-exposure prophylaxis (PrEP) to prevent HIV acquisition by uninfected individuals is a promising approach to slowing the epidemic, but its efficacy is hampered by incomplete patient adherence and ART-resistant variants. Here, we report that competitive inhibition of HIV Env-CCR5 binding via the CCR5-specific antibody Leronlimab protects rhesus macaques against infection following repeated intrarectal challenges of CCR5-tropic SHIVSF162P3. Injection of Leronlimab weekly at 10 mg/kg provides significant but partial protection, while biweekly 50 mg/kg provides complete protection from SHIV acquisition. Tissue biopsies from protected macaques post challenge show complete CCR5 receptor occupancy and an absence of viral nucleic acids. After Leronlimab washout, protected macaques remain aviremic, and adoptive transfer of hematologic cells into naïve macaques does not transmit viral infection. These data identify CCR5 blockade with Leronlimab as a promising approach to HIV prophylaxis and support initiation of clinical trials.


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The sample size was based on previous prevention studies in the macaque model, which demonstrate that n=6 per group is sufficient for detecting significant differences in rates of acquisition of infection (Dobard et al., Journal of Infectious Diseases 2020).
For the in vitro assays involving human samples, no sample size calculation was performed as these studies were proof of concept experiments expected to yield binary results, i.e. Leronlimab will/will not prevent replication of CCR5-utilizing strains of HIV or macaques will/ will not express similar number of CCR5 molecules. The samples sizes were deemed sufficient after the binary outcome was achieved.
No data were excluded from the analyses.
The macaque PrEP study was not run all at once. Instead, it was performed as two separate smaller studies. Any experiments associated with the PrEP study were performed independently for a minimum of two times due to having two separate smaller studies that spanned a period of two years. Similar results were obtained in both smaller studies.
In vitro infection assays, with CCR5 delta 32 human cell ((n=1) were replicated twice in independent runs, while CCR5 WT human cells and macaque cells (n=3 per species) with one replicate each. Assays were not ran all at once but in at least two independent runs. Viral extraction and preparation for env sequencing were performed in independent experiments but were all combined for a single sequencing run.
Animals were first balanced between the experimental groups based on gender. Once gender was balanced, then animals were stratified into groups by weight.
Cells from non-animal experiments were allocated at random, with at least three animals testing each variables. Data was presented as mean values throughout the study. Cells from at least 10 different NHP animal were used in in-vitro studies in this paper.
The investigators running and analyzing the assays to measure SHIV plasma and cell-associated viral loads were blinded to the treatment of the study animals during the entirety of the study. The investigators running the ICS assays to assess for SHIV-specific T cell immunity were blinded to the treatment of study animals during the entirety of the study. The investigators running and analyzing ELISA assays to assess antibody concentration and anti-drug antibody (ADA) development were blinded to the treatment groups. No blinding was done for assays measuring receptor occupancy and lymphocyte staining, nor is it relevant because major readout of study was protection from viral acquisition, which viral quantification assays were performed by different investigators.
Because animals were euthanized at ten-weeks post infection or eight-weeks post lost of RO, which ranged from study week 10-38, some investigators were eventually unblinded due to the lengthy period between euthanasias of individual animals. Note that full information on the approval of the study protocol must also be provided in the manuscript.

Human research participants
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Recruitment
Ethics oversight Note that full information on the approval of the study protocol must also be provided in the manuscript. Rhesus macaques (Macaca mulatta) were included in this study. Both male and female animals were included as well as animals between 2-16 years old.
The study did not involved wild animals.
The study did not involve field-collected samples.
All rhesus macaques (Macaca mulatta) used in this study were housed at the Oregon National Primate Research Center (ONPRC) and utilized for studies under the approval of the Oregon Health and Science University (OHSU) Institutional Animal Care and Use Committee (IACUC). All macaques in this study were managed according to the ONPRC animal care program, which is fully accredited by AAALAC International and is based on the laws, regulations, and guidelines set forth by the United States Department of Agriculture (e.g., the Animal Welfare Act and its regulations, and the Animal Care Policy Manual), Institute for Laboratory Animal Research (e.g., Guide for the Care and Use of Laboratory Animals, 8th edition), and the Public Health Service Policy on Humane Care and Use of Laboratory Animals.
The study includes research samples from only one individual, confirmed to have a CCR5 delta 32 homozygous immune system. Individual was a 54 year old male Caucasian.
The individual was aware of the study aims to recapitulate their CCR5 delta 32 homozygous immune system and thus volunteered to partake in the study. The individual was selected as the only individual known cured of HIV due to a stem cell transplant from a CCR5 delta 32 homozygous donor. Thus, it was previously established that T cells from this individual are resistant to CCR5-utilizing HIV strains.
The apheresis was approved by the Research and Institutional Review Committee (RIRC) of the Queens Medical Center approval number RA-2014-307 of the H026 Study protocol at the University of Hawaii.