Lynn W. Enquist

Henry L. Hillman Professor of Molecular Biology, Emeritus




My research focuses on mechanisms of herpesvirus pathogenesis. Most alpha-herpesviruses (e.g., herpes simplex virus HSV; varicella-zoster virus, VZV; and pseudorabies virus, PRV) are parasites of the peripheral nervous system (PNS) in their natural hosts. This life style is remarkable because of all the neurotropic viruses that also enter the PNS (e.g., rabies), only the alpha-herpesviruses routinely STOP in the PNS of their natural hosts and establish a reactivatable, latent infection. Normally, this PNS infection is relatively benign, promoting survival of both virus and host. However, aberrations in this pathway give rise to the set of common diseases caused by these viruses. For example, invasion of the CNS is a rare, but exceedingly serious possibility. The directional spread of a herpes infection from epithelial surfaces to PNS neurons (where latency is established), and then, upon reactivation, spread back to epithelial surfaces constitutes the virus survival strategy. Research in my laboratory is directed toward answering several basic questions: What are the virus- and cell-encoded mechanisms that direct virus into and back out of the PNS? Why does the virus only occasionally enter the CNS in its natural host? What are the molecular roadblocks that make CNS infection rare in the natural host and frequent in the non-natural host? What are the viral gene products that promote disease and how do they work? How do the PNS and CNS respond to viral infection? These basic questions continue to lead us into exciting (and sometimes unexpected) areas. Two major areas of work are outlined below.

Pseudorabies Virus (PRV) as a Model System

PRV is a broad host range herpesvirus that causes fatal encephalitis in a wide variety of animal species except its natural host, the adult pig. PRV is not a human pathogen and grows well in the lab. Using rodent and chick embryo models and defined mutations in specific PRV genes, we are studying mechanisms of spread from site of primary infection, evasion of innate and acquired immune defense, and cell/tissue damage. We have identified several PRV gene products that affect the extent of PRV pathogenesis in both model systems affecting cell to cell spread, direction of spread, and host response to infection. We have constructed infectious bacterial artificial chromosomes carrying the entire PRV genome and are using E. coli mutagenesis and recombination techniques for genetic analysis of PRV. cDNA analyses coupled with gene array technology are being developed to understand the role of virus and host genes in virus replications in various cell types and tissues of infected animals.

Genetics of Directional Spread of Virus In and Between Neurons

Our work with PRV infections in rats, mice, and chicken embryos demonstrates that directional spread of virus in the nervous system is regulated, in part, by several viral genes. We have developed technology to culture primary embryonic sensory and autonomic PNS neurons from mice, rats, and chickens. Based on these systems, we have defined two distinct processes involved in directional spread: (1) movement of virion components into axons and long distance movement of these components to axon terminals; and (2) interactions between the infected axon terminals and connected cells that promote assembly, virus release, or both. The small type II membrane protein called Us9 affects the first process: it promotes the movement of virion envelope (but not tegument or capsid) components into axons. The type I viral membrane proteins gE and gI also are required for directional spread in the nervous system, but the mechanism for their action is distinct from that of Us9. gE and gI affect the entry of all viral components into axons. gE expression also exacerbates symptoms and speeds time to death in vivo, but this phenotype is not correlated with virus spread. Green and red fluorescent protein fusions to Us9, gE, gI, and other membrane proteins, as well as capsid and tegument proteins enable us to follow synthesis, transport, and assembly of virions in cultured neurons as well as in tissue. The genetics and biochemistry of these proteins and others that affect endocytosis, targeting, virus assembly, egress, spread, and virulence are a major focus of our work.

Tracing the Hardwiring of the Nervous System with a Virus

Unlike infections of the natural host (the adult pig), PRV infections of all other permissive species (e.g., baby pigs, chicken embryos, rodents, dogs, cats, and cows, to name a few) are lethal and quickly transmitted through peripheral nerves to the brain and spinal cord. These infections enable us to study not only mechanisms of virulence and how the nervous system responds to infection, but also how the virus spreads in the nervous system. Amazingly enough, in all permissive species, the virus spreads only in chains of synaptically connected neurons (trans-neuronal spread). Therefore, PRV can be used as a self-amplifying tracer of neuronal circuits. The ability to reveal a neural circuit (neuron A is wired to neuron B is wired to neuron C etc) is powerful technology, but demands attention to many details. Tracing studies are rewarding because they require close collaboration between neurobiologists and virologists. For example, circuit tracing requires use of mutant viruses that are much less virulent than wild type PRV. Understanding why these mutants are good tracing strains has led us to a better understanding of virulence and mechanisms by which virus spreads between neurons. In addition, we capitalize on our ability to manipulate PRV to construct less virulent, innovative tracing viruses: e.g., viruses expressing beta-galactosidase and variants of green fluorescent protein, as well as viruses that replicate only in certain neurons and not others. These viruses provide powerful tools to study neural circuits and how the nervous system responds to infection.


Lynn W. Enquist is Henry L. Hillman Professor in Molecular Biology and Professor in the Princeton Neuroscience Institute at Princeton University.

He received his BS degree in Bacteriology at South Dakota State University in 1967. He received his Ph.D. in Microbiology from Medical College of Virginia, Virginia Commonwealth University in 1971 with S. Gaylen Bradley studying streptomyces biology. He did postdoctoral training at the Roche Institute of Molecular Biology from 1971 to 1973 studying bacteriophage lambda replication and recombination with Ann Skalka. He served in the US Public Health Service from 1973-1981. He was a senior staff fellow at the National Institutes of Health in the laboratory of Dr. Philip Leder working with Robert Weisberg from 1974-1977 studying bacteriophage lambda site-specific recombination and development of recombinant DNA technology. He held a tenured staff position in the National Cancer Institute from 1977 to 1981 where he continued the development of recombinant DNA technology and also began his work on neurotropic herpes viruses. George VandeWoude was his lab chief. In 1981 he left the National Cancer Institute to be Executive Scientist at Molecular Genetics Incorporated in Minnetonka, Minnesota where he worked on recombinant DNA based viral vaccines. In 1984, he joined DuPont as a Research Leader where he ran a laboratory studying neurotropic viruses. In 1990, he joined DuPont Merck Pharmaceutical Company where he was a Senior Research Fellow working on developing neurotropic viruses as tools for gene therapy and studying the mammalian nervous system. In 1993, he accepted the position of tenured full professor of Molecular Biology at Princeton University. He was chair of the department of Molecular Biology from 2004 to 2013.

His research interests are in the field of neurovirology, specifically on the mechanisms of herpesvirus spread and pathogenesis in the mammalian nervous system. His laboratory focuses on understanding the molecular mechanisms by which neuroinvasive alpha-herpesviruses invade and spread in the mammalian nervous system and how the nervous system responds to infection. His laboratory develops and uses imaging technology to define the molecular mechanisms of neuronal spread and subsequent pathogenesis. His work has also lead to the development of these viruses as tools to trace neuronal circuitry in living animals. He has published over 280 peer-reviewed papers, reviews, books and has 4 patents.

He is a Fellow of the American Academy of Microbiology and the American Association for the Advancement of Sciences (AAAS). He was member of the board of directors of the AAAS. He was a member of the National Science Advisory Board for Biosecurity. He was a member of the Scientific Council of the Pasteur Institute from 2007-2013. He was elected to the American Academy of Arts and Sciences. He was past President of the American Society for Virology and editor in chief for the Journal of Virology. He currently is the president of the American Society for Microbiology and the founding editor of the Annual Reviews of Virology.

Honors & Awards


  • President, American Society for Microbiology


  • Honorary Degree, Ghent University


  • B.S., South Dakota State University
  • Ph.D., Medical College of Virginia

Selected Publications