Mitigation of endemic GI-tract pathogen-mediated inflammation through development of multimodal treatment regimen and its impact on SIV acquisition in rhesus macaques

Abstract

Here, we assessed the efficacy of a short-course multimodal therapy (enrofloxacin, azithromycin, fenbendazole, and paromomycin) to eliminate common macaque endemic pathogens (EPs) and evaluated its impact on gastrointestinal (GI) microbiota, mucosal integrity, and local and systemic inflammation in sixteen clinically healthy macaques. Treatment combined with expanded practices resulted in successful maintenance of rhesus macaques (RM) free of common EPs, with no evidence of overt microbiota diversity loss or dysbiosis and instead resulted in a more defined luminal microbiota across study subjects. Creation of a GI pathogen free (GPF) status resulted in improved colonic mucosal barrier function (histologically, reduced colonic MPO+, and reduced pan-bacterial 16s rRNA in the MLN), reduced local and systemic innate and adaptive inflammation with reduction of colonic Mx1 and pSTAT1, decreased intermediate (CD14+CD16+) and non-classical monocytes (CD14-CD16+), reduced populations of peripheral dendritic cells, Ki-67+ and CD38+ CD4+ T cells, Ki-67+IgG+, and Ki-67+IgD+ B cells indicating lower levels of background inflammation in the distal descending colon, draining mesenteric lymph nodes, and systemically in peripheral blood, spleen, and axillary lymph nodes. A more controlled rate of viral acquisition resulted when untreated and treated macaques were challenged by low dose intrarectal SIVmac239x, with an ~100 fold increase in dose required to infect 50% (AID50) of the animals receiving treatment compared to untreated controls. Reduction in and increased consistency of number of transmitted founder variants resulting from challenge seen in the proof of concept study directly correlated with post-treatment GPF animal’s improved barrier function and reduction of key target cell populations (Ki-67+ CD4+T cells) at the site of viral acquisition in the follow up study. These data demonstrate that a therapeutic and operational strategy can successfully eliminate varying background levels of EPs and their associated aberrant immunomodulatory effects within a captive macaque cohort, leading to a more consistent, better defined and reproducible research model.

Antimicrobial prophylaxis does not improve post-surgical outcomes in SIV/SHIV-uninfected or SIV/SHIV-infected macaques (Macaca mulatta and Macaca fascicularis) based on a retrospective analysis

“…Antibiotics may also negatively affect humans and animals in other ways, due to side effects and microbiome changes [ 8 ]. They have been shown to impact key target cell populations for SIV acquisition and disease progression in the colon, such as Th17+ CD4+ T cells [ 20 ], as well as inducing colitis, which has been shown to have a significant impact on acquisition and disease progression in SIV/SHIV models [ 23 , 27 , 28 ]. Even short courses of antibiotics can cause microbiome perturbations that can persist for weeks to months [ 29 ].…”

“…Antimicrobials should not be used based on perceived risk, as is the case when prophylactic antibiotics are used in SIV infected macaques undergoing clean, minimally invasive surgeries. It is essential to follow evidence-based practices, as were performed in this study, to ensure antimicrobial use has clear benefits, such as those demonstrated with elimination of endemic gastrointestinal pathogens in macaques [ 27 ]. Finally, given the similarities in outcomes between SIV infected macaques and HIV infected patients, it is likely that where similar conditions exist (highly trained surgeons, clean surgeries, minimally invasive procedures, and the ability to achieve good aseptic technique), prophylactic antibiotics are also likely unnecessary in HIV patients.…”

Formal Comment on “Mitigation of endemic GI-tract pathogen-mediated inflammation through development of multimodal treatment regimen and its impact on SIV acquisition in rhesus macaques” by Bochart et al. (2021)

“…In humans and animals, fluoroquinolone treatment is a known risk factor for carrying methicillin-resistant Staphylococcus aureus (MRSA) [ 9 ]. There is increasing emphasis on the need to use the ‘precautionary principle’ when assessing AMR risks, and it is highly plausible that the treatment proposed in Bochart et al [ 1 ] similarly drives MRSA selection in macaques. The multi-antimicrobial regimen described was implemented many years ago, albeit without the use of azithromycin, at the National Cancer Institute [ 11 ].…”

“…Finally, if this approach is used, it must be reported in the literature in the methods section of papers to promote research reproducibility. Given the significant impact that pre-study antimicrobials can have on the microbiome of asymptomatic macaques [ 22 ] and the observations associated with mucosal inflammation [ 1 ], reporting such treatments must be a requirement in the materials and methods of all publications, regardless of the aims of the research.…”

“…In this letter, we raise concerns regarding the recent publication, “ Mitigation of endemic GI-tract pathogen-mediated inflammation through development of multimodal treatment regimen and its impact on SIV acquisition in rhesus macaques ” [ 1 ]. This study describes the use of a prophylactic multimodal regimen of three to four different antimicrobial agents including a fluoroquinolone, a macrolide, an aminoglycoside, and a benzimidazole in clinically normal rhesus macaques at two different institutions.…”