Menus Subscribe Search

Follow us


Quick Studies

fung.jpg

Cryptococcus. (Photo: Public Domain)

How Weak Immune Systems Escort a Deadly Fungus Into the Brain

• April 30, 2014 • 10:50 AM

Cryptococcus. (Photo: Public Domain)

A pervasive fungus, passed along by pigeon droppings, can kill HIV patients by using a Trojan Horse strategy to invade their brains.

Pigeon droppings and vulnerable immune systems can be a deadly combination.

Fortunately, scientists are starting to figure out how different strains of a yeast that hitchhiked its way around the world in pigeon intestines can ride along inside immune cells through our bodies and into our brains.

Droppings of the humble rock dove often teem with a species of Cryptococcus, better known as Crypto, a soil-dwelling genus of fungus that researchers in 2007 concluded “gained the ability to sexually reproduce in pigeon guano and then swept the globe.” We breathe the yeast into our lungs all the time. After most of us do that, our immune systems successfully attack, either killing the invaders or smothering them and rendering them harmless. The story is different, however, for those with weakened immune systems. In the bodies of HIV patients, in particular, C. neoformans can radiate from the lungs throughout the body. Once the fungal cells reach the central nervous system, they can trigger deadly meningitis.

Scientists are starting to figure out how different strains of a yeast that hitchhiked its way around the world in pigeon intestines can ride along inside immune cells through our bodies and into our brains.

This is no obscure disease. An estimated 625,000 people are killed every year by the painful malady, most of them infected with HIV. It is a leading killer of HIV sufferers.

Understanding how the fungus works its way from the lung to the brain is a priority for medical researchers. And research published this month in the Journal of Clinical Investigation has revealed that it does this by tricking our immune systemsit hitches a ride, Trojan Horse style, inside the cells that were dispatched to attack it.

The scientists studied C. neoformans strains taken from 65 HIV patients in parts of South Africa and Thailand. They measured how effectively human macrophages (also known as phagocytes), which are large defensive cells that move freely around the body, gobbled up each strain. They found a positive correlation between the density of fungal cells in the patients’ central nervous systems and the rate at which the strains were absorbed by macrophages. The patients infected with strains that were most easily engulfed by the defensive cells were most likely to die of fungal meningitis.

The scientists propose that the macrophages are ferrying the pathogen into the brains of HIV patients. “In HIV-infected patients … the ease of uptake of cryptococci by macrophages, coupled with the inability to orchestrate an effective IFN-γ-activated fungicidal macrophage response, results in unchecked proliferation and survival,” they write.

The findings reveal that still-functioning elements of HIV patients’ immune systems help the disease spread, while broken down elements cruelly hobble any kind of an effective response.

“The immunocompromised patients that come down with Crypto have defects in adaptive immunity, or T-cell function,” says University of Birmingham professor Robin May, one of the authors of the paper. “Phagocyte function is usually semi-normal in such patients, which is why Cryptococci can still exploit these cells.”

May says the findings could help doctors figure out whether patients are infected with higher-risk strains, and prescribe treatments accordingly. In the longer term, they could lead to the development of more effective therapies.

John Upton
John Upton is a science journalist with an ecology background. He has written recently for VICE, Slate, Nautilus, Modern Farmer, Grist, and Audubon magazine. He blogs at Wonk on the Wildlife. Upton's favorite eukaryotes are fungi, but he won't fault you for being human. Follow him on Twitter @johnupton.

More From John Upton

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

November 21 • 4:00 PM

Why Are America’s Poorest Toddlers Being Over-Prescribed ADHD Drugs?

Against all medical guidelines, children who are two and three years old are getting diagnosed with ADHD and treated with Adderall and other stimulants. It may be shocking, but it’s perfectly legal.



November 21 • 2:00 PM

The Best Moms Let Mess Happen

That’s the message of a Bounty commercial that reminds this sociologist of Sharon Hays’ work on “the ideology of intensive motherhood.”


November 21 • 12:00 PM

Eating Disorders Are Not Just for Women

Men, like women, are affected by our cultural preoccupation with thinness. And refusing to recognize that only makes things worse.


November 21 • 10:00 AM

Queens of the South

Inside Asheville, North Carolina’s 7th annual Miss Gay Latina pageant.


November 21 • 9:12 AM

‘Shirtstorm’ and Sexism in Science

Following the recent T-shirt controversy, it’s clear that sexism in science persists. But the forces driving the gender gap are still being debated.


November 21 • 8:00 AM

What Makes a Film Successful in 2014?

Domestic box office earnings are no longer a reliable metric.



November 21 • 6:00 AM

What Makes a City Unhappy?

According to the National Bureau of Economic Research, Dana McMahan splits time between two of the country’s unhappiest cities. She set out to explore the causes of the happiness deficits.


November 21 • 5:04 AM

Sufferers of Social Anxiety Disorder, Your Friends Like You

The first study of friends’ perceptions suggest they know something’s off with their pals but like them just the same.


November 21 • 4:00 AM

In 2001 Study, Black Celebrities Judged Harshly in Rape Cases

When accused of rape, black celebrities were viewed more negatively than non-celebrities. The opposite was true of whites.


November 20 • 4:00 PM

Women, Kink, and Sex Addiction: It’s Not Like the Movies

The popular view is that if a woman is into BDSM she’s probably a sex addict, and vice versa. In fact, most kinky women are perfectly happy—and possibly healthier than their vanilla counterparts.


November 20 • 2:00 PM

A Majority of Middle-Class Black Children Will Be Poorer as Adults

The disturbing findings of a new study.


November 20 • 12:00 PM

Standing Up for My Group by Kicking Yours

Members of a minority ethnic group are less likely to express support for gay equality if they believe their own group suffers from discrimination.


November 20 • 10:00 AM

For Juvenile Records, It’s ‘Justice by Geography’

A new study finds an inconsistent patchwork of policies across states for how juvenile records are sealed and expunged.


November 20 • 8:00 AM

Surviving the Secret Childhood Trauma of a Parent’s Drug Addiction

As a young girl, Alana Levinson struggled with the shame of her father’s substance abuse. But when she looked more deeply into the research on children of drug-addicted parents, she realized society’s “conspiracy of silence” was keeping her—and possibly millions of others—from adequately dealing with the experience.



November 20 • 6:00 AM

Extreme Weather, Caused by Climate Change, Is Here. Can Nike Prepare You?

Following the approach we often see from companies marketing products before big storms, Nike focuses on climate change science in the promotion of its latest line of base-layer apparel. Is it a sign that more Americans are taking climate change seriously? Don’t get your hopes up.


November 20 • 5:00 AM

How Old Brains Learn New Tricks

A new study shows that the neural plasticity needed for learning doesn’t vanish as we age—it just moves.


November 20 • 4:00 AM

The FBI’s Dangerous Misrepresentation of Encryption Law

The FBI no more deserves a direct line to your data than it deserves to intercept your mail at the post office. But it doesn’t want you to know that.


November 20 • 2:00 AM

Brain Drain Is Economic Development

It may be hard to see unless you shift your focus from places to people, but both destination and source can benefit from “brain drain.”


November 19 • 9:00 PM

Gays Rights Are Great, but Ixnay on the PDAs

New research suggests both heterosexuals and gay men are uncomfortable with public same-sex kissing.


November 19 • 4:00 PM

The Red Cross’ Own Employees Doubt the Charity’s Ethics

Survey results obtained by ProPublica also show a crisis of trust in the charity’s senior leadership.



November 19 • 2:00 PM

Egg Freezing Isn’t the Feminist Issue You Think It Is

New benefits being offered by Apple and Facebook probably aren’t about discouraging women from becoming mothers at a “natural” age.


Follow us


Sufferers of Social Anxiety Disorder, Your Friends Like You

The first study of friends' perceptions suggest they know something's off with their pals but like them just the same.

Standing Up for My Group by Kicking Yours

Members of a minority ethnic group are less likely to express support for gay equality if they believe their own group suffers from discrimination.

How Old Brains Learn New Tricks

A new study shows that the neural plasticity needed for learning doesn't vanish as we age—it just moves.

Ethnic Diversity Deflates Market Bubbles

But it's not in the rainbow and sing-along way you'd hope for. We just don't trust outsiders' judgments.

Online Brain Exercises Are Probably Useless

Even under the guidance of a specialist trainer, computer-based brain exercises have only modest benefits, a new analysis shows.

The Big One

One company, Comcast, will control up to 40 percent of Internet service coverage in the U.S., and 19 of the top 20 cable markets, if a proposed merger with Time Warner Cable is approved by regulators. November/December 2014

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.