Genetic Approaches to the Control 
of Mycobacterial Diseases 
William R. Jacobs, Jr., Ph.D. — Assistant Investigator 
Dr. Jacobs is also Associate Professor of Microbiology and Immunology and of Molecular Genetics at 
Albert Einstein College of Medicine. He received a B.A. degree in mathematics at Edinboro University of 
Pennsylvania and a Ph.D. degree in molecular cell biology from the University of Alabama at 
Birmingham. His doctoral work on Mycobacterium leprae was performed in the laboratory of Josephine 
Clark Curtiss and Roy Curtiss III, first at the University of Alabama and then at Washington University, 
St. louis. His postdoctoral studies with Barry Bloom focused on developing systems to express foreign 
antigens in the tuberculosis vaccine strain BCG (bacille Calmette-Guerin). 
TUBERCULOSIS, caused by Mycobacterium 
tuberculosis, continues to be a serious 
health problem throughout the world. Even in 
the developed countries, this plague has been 
escalating in recent years. The World Health Orga- 
nization (WHO) estimates a worldwide inci- 
dence of approximately 8 million new cases and 
over 3 million deaths annually. After 32 years of 
steady decline in the United States, the number of 
new cases has taken a surprising and alarming up- 
ward turn for each of the last five years. In 1990 
there was a 34 percent increase in New York City 
and a 10 percent increase nationally. More re- 
cently a strain of multidrug-resistant M. tubercu- 
losis has resulted in numerous deaths, demon- 
strating the dire reality that tuberculosis caused 
by a virtually invincible pathogen is now 
spreading. 
Other mycobacteria play significant roles in 
world health. Mycobacterium leprae is the caus- 
ative agent of leprosy, an affliction know to the 
ancients that affects over 1 3 million in the world 
today. Another agent is Mycobacterium avium, a 
major opportunistic pathogen for many individ- 
uals with AIDS. 
Our ongoing studies are aimed at developing 
novel ways of treating mycobacterial disease, par- 
ticularly tuberculosis, using molecular genetic 
approaches. In addition, we have taken a new 
look at the vaccine known as BCG (bacille 
Calmette-Guerin), which has been used widely 
since 1 924 to prevent tuberculosis. We are genet- 
ically engineering BCG into a multivalent vac- 
cine vector that can elicit a protective immune 
response to a wide variety of bacterial, viral, and 
parasitic pathogens. The development of systems 
to alter mycobacteria genetically should permit 
both goals to be achieved. 
Genetic manipulation of these microorganisms 
has only been possible in the last few years. M. 
tuberculosis, like other mycobacteria, is difficult 
to analyze genetically for a variety of reasons. 
First, the tubercle bacillus, which multiplies 
only once every 24 hours, requires 3 weeks to 
form a colony from a single cell. In contrast, Esch 
erichia coli yields visible colonies in 8 hours. 
The leprosy bacillus has yet to be cultivated in 
the laboratory and can only be grown in mouse 
footpads or the nine-banded armadillo. Over the 
last five years, we have developed a series of 
phage- and plasmid-based vectors that have en- 
abled the efficient introduction of recombinant 
DNA into mycobacteria. Recombinant DNA tech- 
nologies have opened exciting new doors to basic 
knowledge about these organisms and the ways 
they cause infection. In addition, these technolo- 
gies offer novel reagents, such as luciferase re- 
porter phages, and recombinant vaccines that 
could play major roles in combating human 
disease. 
Epidemiological Analysis 
of Tuberculosis Infections 
Use of restriction fragment length polymor- 
phisms (RFLPs) can play a key role in determin- 
ing the mode of transmission of tuberculosis, as 
individual isolates can be tracked from one in- 
fected person to the next. The recent increases in 
the incidence of tuberculosis in the United States 
seem to be largely associated with the AIDS epi- 
demic. However, it was unclear whether the tu- 
berculosis seen in AIDS patients results from 
reactivated disease, reflecting pre -AIDS expo- 
sure, or from a first-time infection. In collabora- 
tions with researchers in San Francisco, including 
Gary Schoolnik (HHMI, Stanford University), we 
have undertaken analyses to distinguish these two 
possibilities. 
Different isolates of M. tuberculosis have dif- 
ferent RFLP patterns when probed with a particu- 
lar DNA element found in M. tuberculosis 
strains. In isolates from a recent tuberculosis out- 
break among AIDS patients in a group home, RFLP 
analysis revealed that 1 1 persons had all been in- 
fected with the same strain of M. tuberculosis. 
This demonstrates that AIDS patients are highly 
susceptible to M. tuberculosis infection and con- 
firms that tuberculosis is highly contagious. 
These clear results should be translatable into 
better public health care policies. Similar analy- 
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