About

Ronald G. Collman, MD, is a Professor of Medicine specializing in Pulmonary, Allergy, and Critical Care at the University of Pennsylvania School of Medicine. His research focuses on mechanisms of HIV/SIV entry and target cell tropism, and their role in disease pathogenesis. He studies how HIV and SIV infect T lymphocytes and macrophages, with particular attention to entry pathways involving CCR5, CXCR4, and non-canonical coreceptors, and how these pathways influence disease outcomes in pathogenic and natural host infections. His work also investigates monocyte and macrophage activation in HIV infection, exploring mechanisms, their contribution to pathogenesis, and potential modulation strategies. This includes studying persistent immune activation even in ART-treated subjects and its link to neurocognitive deficits. Additionally, Collman researches the microbiome and molecular microbiology of the human respiratory tract, analyzing bacterial, fungal, and viral populations in health and disease states such as HIV infection and lung transplantation. His contributions aim to deepen understanding of viral entry, immune activation, and microbiome interactions in lung and systemic diseases.

Research topics

• Biology
• Medicine
• Virology
• Chemistry
• Internal medicine
• Molecular biology
• Biochemistry
• Immunology
• Zoology
• Genetics
• Computational biology
• Endocrinology
• Pathology
• Pharmacology
• Evolutionary biology
• Gerontology

Selected publications

• Antibodies Elicited by the 2025–2026 Influenza Vaccine

  NEJM Evidence · 2026-03-03

  article

  AbstractA new H3N2 variant (named subclade K) possesses several key hemagglutinin substitutions and is circulating widely during the 2025-2026 influenza season. We sought to determine whether the 2025-2026 seasonal influenza vaccine elicits antibodies in humans that recognize this variant. We found that H3N2 subclade K viruses are antigenically advanced; however, the 2025-2026 seasonal influenza vaccine elicited antibodies in many individuals that efficiently recognized these viruses. Thus, the current seasonal influenza vaccine likely will be partially effective at preventing illness associated with H3N2 subclade K virus infections.

  PublisherDOI

• Antibodies elicited by the 2025-2026 influenza vaccine in humans

  medRxiv · 2026-01-06 · 7 citations

  articleOpen access

  Abstract A new H3N2 variant (named subclade K) possesses several key hemagglutinin substitutions and is circulating widely during the 2025-2026 influenza season. In this report, we completed experiments to determine if the 2025-2026 seasonal influenza vaccine elicits antibodies in humans that recognize this variant. We find that H3N2 subclade K viruses are antigenically advanced; however, the 2025-2026 seasonal influenza vaccine elicited antibodies in many individuals that efficiently recognized these viruses. Thus, the current seasonal influenza vaccine will likely be somewhat effective at preventing H3N2 subclade K virus infections.

  PublisherOA PDFDOI

• Mapping the specificity of H3N2 strain-specific and cross-reactive human neutralizing antibodies elicited by the 2025-2026 influenza vaccine

  medRxiv · 2026-02-22 · 1 citations

  articleOpen access

  An H3N2 variant, named subclade K, continues to circulate widely during the 2025-2026 influenza season. This virus possesses a hemagglutinin (HA) protein that has eleven substitutions relative to the HA of the Northern Hemisphere 2025-2026 H3N2 vaccine strain. Many of these substitutions are in epitopes in well-characterized HA antigenic sites. Despite this, interim vaccine effectiveness studies indicate that the 2025-2026 influenza vaccine provides moderate protection against H3N2 subclade K infection. We previously reported that many individuals who received the 2025-2026 influenza vaccine produced antibodies that inhibit H3N2 subclade K virus cellular attachment. Here, we show these individuals also produced antibodies that neutralize H3N2 subclade K virus infection, and we observed a strong correlation between hemagglutination-inhibition titers and neutralizing antibody titers. We completed additional specificity studies using samples from individuals who did or did not have antibodies that cross-reacted to H3N2 subclade K viruses. Using high-throughput neutralization assays, we determined that antibodies that bound to the vaccine strain but not H3N2 subclade K viruses typically targeted antigenic site B of HA. Conversely, we found that cross-reactive neutralizing antibodies elicited by vaccination commonly targeted antigenic site A, D, and E of HA that are conserved between the vaccine strain and H3N2 subclade K viruses. Additional electron microscopy-based polyclonal epitope mapping studies confirmed that cross-reactive antibodies elicited by vaccination typically target epitopes on the side of HA. Together, our studies provide an immunological explanation of why the 2025-2026 influenza vaccine was partially effective against antigenically advance H3N2 subclade K viruses. Our data suggest that vaccine strains for subsequent seasons need to be carefully considered, since subclade K viruses have already started to acquire additional substitutions in HA antigenic sites targeted by cross-reactive antibodies.

  PublisherDOI

• Dynamics of gut bacteriophage in diversity outbred mice studied over lifespan and during extreme caloric restriction

  Microbiome · 2026-03-03

  articleOpen access

  BACKGROUND: The majority of bacteria in the vertebrate gut harbor integrated bacterial viruses ("bacteriophages" or "phages"; integrated phage are termed "prophages"). To probe phage replication strategies in the mammalian gut microbiome, we investigated phage activity in a large longitudinal study of diversity outbred mice (913 animals) undergoing extreme dietary restriction with detailed phenotypic characterization across lifespan. RESULTS: We assembled 54,119 candidate DNA viral genomes from 2997 longitudinal metagenomes, forming 6462 viral operational taxonomic units (vOTUs). Over 85% of vOTUs annotated as novel. Viruses annotated predominantly as prophages in the Caudoviricetes class. We detected no eukaryotic DNA viruses, and none of the strictly lytic Crassvirales order that is abundant in human gut. The most prevalent phages had the widest predicted host ranges. The relative abundance of most phages was highly correlated to that of their inferred host bacteria, suggesting quiescent prophages dominate viral metagenomes, consistent with "piggyback-the-winner" dynamics. After accounting for close phage-bacterial covariation, we did identify a subset of phages changing in relative abundance and prevalence relative to their hosts in response to dietary restriction and aging. In particular, phages with larger genomes become less common in diets with restricted calories, potentially reflecting a higher fitness cost to their host. Generalist phages were enriched for a gene encoding a single-strand DNA binding protein which is reportedly involved in DNA repair and protection from nucleases encoded by host cells. Lytic phages became more common with aging, and we observed a reduction in phage richness with age, both findings previously observed in human cohorts. CONCLUSION: These studies enrich our understanding of DNA phage dynamics in gut while emphasizing the predominance of "piggyback-the-winner" strategies.

  PublisherDOI

• Enhanced Isolation and Detection of COVID-19 in Hospitalized Patients Undergoing Antiviral Therapy

  Emerging infectious diseases · 2026-01-01

  articleOpen access

  We evaluated the efficiency of SARS-CoV-2 detection from patient respiratory specimens by comparing 3 cell lines: Vero E6, Vero E6 expressing transmembrane protease serine 2 (Vero E6 T2), and Vero E6 expressing angiotensin-converting enzyme 2 and transmembrane protease serine 2 (Vero E6 A2T2). We compared a range of sample types, clinical conditions, and real-time reverse transcription PCR cycle threshold values. Vero E6 A2T2 exhibited enhanced sensitivity by supporting efficient virus entry and replication with faster cytopathic effect. Vero E6 culture isolated infectious virus only up to 3 days after PCR confirmation but with Vero E6 A2T2 cells, culture occurred up to 7 days after confirmation. Whole-genome sequencing showed no evidence of adaptive mutations when Vero E6 A2T2 was used for viral culture, supporting use for downstream analyses. Optimized infectious virus detection systems are needed for research and clinical settings, particularly for high-risk, immunocompromised populations that produce virus longer and contribute to variant emergence.

  PublisherDOI

• Optimizing methods for virome analysis based on studies of a synthetic viral community

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-10-23

  preprintOpen access

  Studies of whole viral populations--the "virome"--are yielding exciting new insights into biological systems, but methods are still being optimized. Here we describe generation and use of a synthetic viral community to assess several technical challenges important in virome analysis. Our mock community was comprised of phages lambda, T4, M13, MS2, and phi6, together with adeno-associated virus (AAV), murine hepatitis virus (MHV), and vaccinia virus (VV). We spiked the mock community into different human sample types, including stool, saliva, oropharyngeal (OP) wash, and bronchoalveolar lavage (BAL), then passed the samples through different virus enrichment protocols and analyzed by Illumina sequencing. Compared to direct metagenomic sequencing, VLP enrichment protocols greatly increased viral read yields from virus-rich samples such as from stool and saliva. Three VLP enrichment work flows were compared, and each was found to have strengths and weaknesses. Four methods for DNA amplification were compared, with three showing over-amplification of small circular ssDNA viruses, most notably GenomiPhi. Studies of viral particle stability in the presence of nuclease showed that most viral genomes were stable when protected in viral particles, but phage MS2 RNA was unexpectedly labile under some of the conditions tested. Comparison of Illumina 1000-cycle sequencing versus 300-cycle sequencing showed that longer reads supported generation of longer viral genome assemblies. Bacteriophage DNA can be modified by at least 12 different chemistries, raising the question of whether these modifications might block recovery in virome analytical protocols. We tested bacteriophage T4 DNA modified with glucosyl-hydroxymethylcytosine (ghmC) and hydroxymethylcytosine (hmC), and found that both were readily detected, though the recovery of ghmC-modified DNA was reduced. These studies together with published data help provide guidance for virome researchers optimizing analytical protocols.

  PublisherOA PDFDOI

• Childhood immunological imprinting of cross-subtype antibodies targeting the hemagglutinin head domain of influenza viruses

  Cell Host & Microbe · 2025-09-25

  articleOpen access
  PublisherOA PDFDOI

• Lung transplant for CF: Low lung bacterial burden and immune mediators in year one associate with CLAD development

  Journal of Cystic Fibrosis · 2025-10-10

  articleSenior author
  PublisherDOI

• Galantamine for 12 weeks does not improve neurocognition or immune activation in ART-suppressed people with HIV

  AIDS · 2025-11-27

  articleCorresponding

  OBJECTIVE: People with HIV on ART are highly vulnerable to non-AIDS-related comorbidities, including HIV-associated neurocognitive disorders, which are linked to persistently activated monocytes/macrophages. Smoking is a major contributor to HIV-related comorbidities. However, nicotine alone has anti-inflammatory effects, mainly through α7-nicotinic receptor (nAChR) activation. Galantamine (GAL) is an FDA-approved pro-cognitive medication that increases endogenous acetylcholine and also directly potentiates the α7-nAChR. We hypothesized that GAL would improve neurocognition in PWH, both by direct pro-cognitive effects and by reducing inflammation. We also explored whether effects differed by smoking status. DESIGN/METHODS: Smoking and nonsmoking PWH/ART participated in a double-blind, randomized, placebo-controlled crossover study of 12 weeks of GAL treatment. Primary outcomes were composite neurocognitive test score; monocyte CD16, CD163 and CCR2, and CD8 T-cell CD38/HLA-DR; and plasma sCD16, sCD163 and CCL2. Plasma hsCRP and neurofilament light chain (NFL) were also measured. Exploratory analyses included plasma mediators by Luminex and monocyte transcriptome by RNAseq. RESULTS: Neurocognition did not differ between GAL and placebo treatment (adjusted standardized difference (95% CI) -0.02 (-0.2, 0.2); P = 0.82), with no difference by smoking status ( P = 0.51). Monocyte CCR2 expression was 15.2% (5, 25.1) greater with GAL than placebo ( P = 0.006). No differences were seen in monocyte CD16 ( P = 0.76) or CD163 ( P = 0.8), CD8 + T-cell CD38/HLA-DR ( P = 0.54), or plasma sCD163 ( P = 0.36), sCD14 ( P = 0.46), or CCL2 ( P = 0.34). NFL and hsCRP were not different, but several pro-inflammatory cytokines increased with GAL. Only modest effects were seen on monocyte gene expression. CONCLUSIONS: Galantamine for 12 weeks did not improve cognition or reduce inflammation in PWH/ART regardless of smoking status.

  PublisherDOI

• Association of smoking with neurocognition, inflammatory and myeloid cell activation profiles in people with HIV on antiretroviral therapy: Erratum

  AIDS · 2025-05-29

  erratumSenior author
  PublisherDOI

Recent grants

• Molecular & Translational Immunotechnology Core

  NIH · $36.7M · 1999–2029

• NIH Grant P01NS027405

  NIH · $18.9M · 2010

• NIH Grant U01HL098957

  NIH · $3.9M · 2015

• Targeting the Cholinergic Pathway in HIV-associated Inflammation and Cognitive Dysfunction

  NIH · $3.8M · 2017–2025

• NIH Grant U01HL112712

  NIH · $469k · 2016

Frequent coauthors

• Frederic D. Bushman

  97 shared

• Yanjie Yi

  University of Pennsylvania

  61 shared

• Sundarasamy Mahalingam

  Indian Institute of Technology Madras

  50 shared

• Brendan J. Kelly

  49 shared

• Claude E. Monken

  Rutgers, The State University of New Jersey

  47 shared

• Abhay Srinivasan

  Children's Hospital of Philadelphia

  44 shared

• Kyle Bittinger

  California University of Pennsylvania

  39 shared

• Jevon Graham-Wooten

  University of Pennsylvania

  38 shared

Labs

• Ronald G. Collman LaboratoryPI