Menu

Incomplete Immunity

By combining experimental data with computer models, researchers were able to predict a pathogen’s evolution toward more virulence.

Jun 1, 2018
Jim Daley

BYE BYE BIRDIE: A study suggests a weak immune response could drive pathogens toward greater virulence. MARIE READ

EDITOR’S CHOICE IN EVOLUTION

The paper
A.E. Fleming-Davies et al., “Incomplete host immunity favors the evolution of virulence in an emergent pathogen,” Science, 359:1030-33, 2018.

FINCH KILLER
Since 1994, an epidemic of conjunctivitis caused by the bacterium Mycoplasma gallisepticum has ravaged house finch (Haemorhous mexicanus) populations across North America. Arietta Fleming-Davies and Dana Hawley, disease ecologists at the University of San Diego and Virginia Tech, respectively, noted that many birds that had been infected remained susceptible to later infection. The phenomenon reminded Fleming-Davies of findings by other researchers that when a vaccine partially protects a host, it can drive a pathogen to evolve more virulence. (See “Do Pathogens Gain Virulence as Hosts Become More Resistant?The Scientist, October 2017.)

BIRD IN A CAGE
To find out whether something similar was happening in finches, the duo and their colleagues simulated the natural epidemic in the lab, infecting captive birds with increasingly virulent strains of M. gallisepticum and observing the severity of their symptoms. Fleming-Davis then used the data to model infection and the evolution of pathogen virulence in the wild.

CHINKS IN THE ARMOR
The model predicted almost twice as much virulence when bacterial attackers were confronted with incomplete immunity compared to zero immunity, Fleming-Davis tells The Scientist. This suggests, the authors write, that a weak immune response favors nastier pathogens that can overcome defenses.

NOT THE WHOLE STORY
That idea is “an interesting concept, especially as it relates to vaccine research,” says Molly Staley, an evolutionary biologist at the Brookfield Zoo, “but it doesn’t quite fit with what we know” about M. gallisepticum. The birds’ ability to resist manipulation of their immune systems by the bacteria is the primary driver of the pathogen’s increased virulence in the wild, Staley explains, adding that most of the birds infected in the wild are immunologically naïve juveniles, so the responses of previously infected birds likely have only a small effect on virulence evolution.

Correction (June 21): The photo credit on the image that accompanies this article originally referred to the wrong photographer and has been corrected. The Scientist regrets the error.

September 2018

The Muscle Issue

The dynamic tissue reveals its secrets

Marketplace

Sponsored Product Updates

Enabling Genomics-Guided Precision Medicine

Enabling Genomics-Guided Precision Medicine

Download this eBook from Qiagen to learn more about the promise of precision medicine and how QCITM Interpret can help deliver better care with better knowledge.

Best Practices for Sample Preparation and Lipid Extraction from Various Samples

Best Practices for Sample Preparation and Lipid Extraction from Various Samples

Download this white paper from Bertin Technologies to learn how to extract and analyze lipid samples from various models!

Bio-Rad Launches CHT Ceramic Hydroxyapatite XT Media and Nuvia HP-Q Resin for Process Protein Purification

Bio-Rad Launches CHT Ceramic Hydroxyapatite XT Media and Nuvia HP-Q Resin for Process Protein Purification

Bio-Rad Laboratories, Inc. (NYSE: BIO and BIOb), a global leader of life science research and clinical diagnostic products, today announced the launch of two new chromatography media for process protein purification: CHT Ceramic Hydroxyapatite XT Media and Nuvia HP-Q Resin.

Immunophenotypic Analysis of Human Blood Leukocyte Subsets

Immunophenotypic Analysis of Human Blood Leukocyte Subsets

Download this application note from ACEA Biosciences, Inc., to find out how to perform an immunophenotypic analysis of a human blood sample utilizing 13 fluorescent markers using a compact benchtop flow cytometer equipped with 3 lasers!