worst case- hiv + tb

8/8/2019 Worst Case- HIV + TB

http://slidepdf.com/reader/full/worst-case-hiv-tb 1/1

NYU PHYSICIAN+ SUMMER 2008 

   I   N   F   O   G   R   A   P   H   I   C

   P   E   T   E   R   O   U   M   A   S   K   I

Doctor:MICHAEL WEIDEN

06

people focus on lymphocytes becausethey are the intelligent part of the immunedo the dirty work, informed by lympho-cytes. But here they can also be instructedby neutrophils.”

Treating TB in conjunction with HIV isa lot more complicated than prescribing

medicines for both. Each group of drugsdoctors know that a patient is infectedwith both diseases, they generally have toonly after the patient has improved. Inworse, a phenomenon no one really under-stands yet. Often, because TB tests can’tdetect the bacterium in someone infectedwith HIV, doctors don’t even realize that apatient has TB until it’s too late.

now trying to tease out the molecular

players involved in interactions betweenthe deadly duo, in the hope that they caneventually understand how to treat one orboth diseases without making the patientworse.

24

  WHEN HIV JOINS FORCES WITH TB, THE

the germs that cause TB. Occasionally, these bacteriatravel through the blood and lymph vessels, forminglesions in the liver, spleen, and beyond. In chest X-rays,

it looks as if the lung were studded with small nodulesthe size of millet seeds.This gruesome scenario is rarely seen

ravages the immune system, TB quicklyand effortlessly spreads through the body.HIV’s compounding effect on TB has longbeen known, but recently scientists havediscovered that this pernicious partner-ship works both ways. TB, in turn, easesthe path of HIV, dismantling the systemthat keeps the virus under control in thelungs, allowing it to mutate and multiply.

“If you have HIV and TB, then TBwill kill you much more rapidly,” notes

of medicine and environmental medicine.In fact, TB is the leading cause of deathamong people who are HIV-positive,accounting for one-third of AIDS deathsworldwide.

Under normal circumstances, the lungis not a hospitable environment for HIV.even the smallest of irritants — dust, for ex-ample — would keep the lung chronicallyalso held in check. The virus is limited toinfecting perhaps one macrophage — a type

of immune cell that serves as a reservoir forthe virus — out of every 10 million.

But a bacterial infection such as TBchanges all that. Attacked by the germsthat cause TB, the lungs respond by re-cruiting neutrophils and T lymphocytes,Neutrophils are deployed early and ingreat numbers to destroy any foreigninvader. T cells are credited with beingsmarter, remembering previous offendersand releasing proteins that regulate theimmune system.

Both types of cells shut down the off switch, allowing HIV to replicate. Othercell types also secrete proteins that speedup HIV’s replication in macrophages andincrease the rate at which HIV mutates,making it more virulent. As a result, HIV’spresence in macrophages grows by asmuch as 100,000-fold.

these interactions in 16 patients with HIVand TB. They reported in the May 2007issue of the Journal of Infectious Diseases thatTB infection activates neutrophils, and

that these cells are responsible for driv-ing the virus’s replication, a surprisinghad looked primarily at T lymphocytes,the virus’s main host in the body. “Most

Worst Case:TB + HIVNYU researchers are hoping tounderstand how to treat oneor both diseases without making

the patient worse.

BY: APOORVAMANDAVILLI

Estimates of HIV Prevalence inNew TB Cases, 2005

HIV Prevalencein TB (ages, 16-49years)

No Estimate0-45-1320-4950 or more

Source: World Health Organization