Intracellular Bacteria and Protozoa - Intracellular Delivery: Fundamentals and Applications - page 759

20 mg/kg of bw either daily for 5 consecutive days or twice weekly for 3 weeks
(Klemens et al. 1990 ). Liposomal GEN significantly reduced viable cell counts in
the spleen and liver compared with the free GEN. Consecutive and intermittent
treatments produced a 1.5-log and a 2.5-log reduction in cell counts in spleen and
liver, respectively. None of the regimens resulted in sterilization of spleen and liver
and the bactericidal activity of liposomal GEN was not present in lungs.
A further assay employed CLF, used for leprosy, although it is also used in cases
of tuberculosis resistant to other drugs (Sepkowitz et al. 1995 ), and it shows activity
against MAC. This drug, in addition to causing many side effects, it has not been
therapeutically beneficial for tuberculosis. Liposomal encapsulation of CLF
allowed its parenteral administration and resulted more effective in treatment of
MAC infection than free CLF i.v. or orally administered to beige mice (Kansal
et al. 1997 ; Mehta 1996 ). The maximum tolerated dose of free CLF was 5 mg/kg
bw, which was not enough to cause a significant reduction in the number of viable
M. tuberculosis bacilli (Mehta 1996 ). Even this concentration of free drug cannot
be administered i.v. to patients because of its lipophilicity, the presence of organic
solvents and crystallization in the aqueous phase. An equivalent concentration of
liposomal CLF did not improve the treatment outcome; however, encapsulation of
CLF in liposomes reduced toxicity and allowed i.v. administration as well as
administration of higher doses, enhancing therapeutic efficacy as observed with
MAC (Kansal et al. 1997 ; Mehta 1996 ).
After the liposomal CLF activity against experimental tuberculosis was proven,
its performance against acute and chronic infection was determined. CLF was
loaded in MLV (dipalmitoyl phosphatidylcholine (DPPC): dipalmitoyl phosphati-
dylglycerol (DPPG), 7:3 M ratio) and administered to infected mice at 50 mg/kg
bw. It was found that the antibacterial activity was more pronounced in the chronic-
infection model. This was attributed to the combined effect of the drug, the acquired
specific immunity, and granuloma formation. Overall, the treatment was more
effective in liver and spleen than in lungs, similar to previous studies with MAC
infection (Kansal et al. 1997 ; Mehta 1996 ). Once again, the lungs responded poorly
to liposomal CLF therapy when the animals were infected with greater numbers of
bacteria. In the lungs, a gradual decrease in CFU was observed, though a rebound
was found 2 months post-treatment. Regardless of the apparently total clearance of
the bacilli following a second treatment with the liposomal CLF, a similar phenom-
enon was observed after 2 months (Adams et al. 1999 ).
A recent study reinforced the effectivity of liposomal antibiotics in the intermittent
treatment of tuberculosis. PYZ was loaded in liposomes (DPPC: cholesterol (chol),
7: 2 M ratio) and administered to mice infected with M. tuberculosis (El-Ridy et al.
2007 ). Liposomal PYZ caused a significant reduction in bacterial counts (CFU/g) in
lungs, 10, 20 and 30 days after the last treatment dose. Histopathological examination
of mice lungs showed highest severity of infection in empty liposomes > liposomal
PYZ > free PYZ 6 days/week. The results indicate high therapeutic efficacy of lipo-
somal PYZ injected twice weekly in treatment of M. tuberculosis in mice.
In a second study, the performance of liposomal Rifabutin (RFB a rifamycin
used for patients taking drugs (particularly antiretroviral drugs) that have unacceptable