Pharmaceutical Manufacturing Handbook: Production and

PEPTIDE/PROTEIN ENCAPSULATED INTO BIODEGRADABLE MICROSPHERES 423
optimal particle sizes in micrometer ranges for improved humoral response from
single - point immunization. Increasing antigen load on polymer particles was found
to have a positive infl uence on the generation of antibody titers from particle - based
immunization. Maximum peak antibody titer of ∼ 300 μ g/mL was achieved on day
50 upon immunization with particles having the highest load of antigen (94 μ g/mg
of polymer). Increase in dose of polymer - entrapped antigen resulted in concomitant
increase in peak antibody titers, indicating the importance of antigen stability, particle
size, and load on generating a reproducible immune response. Optimization of
particle size, antigen load, dose, and use of additional adjuvant resulted in high and
sustained anti - TT antibody titers over a period of more than 250 days from single -
point immunization. Serum anti - TT antibody titers from single - point immunization
of admixture of PLA particles and alum were comparable with immunization from
two divided doses of alum - adsorbed TT.
Vibrio Cholerae ( VC) Whole -Cell Vaccine Cholera, an acute intestinal infection
caused by the bacterium Vibrio cholerae , produces an enterotoxin that causes a
copious, painless, watery diarrhea that can quickly lead to severe dehydration and
death if treatment is not promptly given. For prevention of cholera, cholera vaccine
is usually given. VC was successfully entrapped in the PLGA microspheres by a
double - emulsion method with trapping effi ciencies up to 98%. The immnunogenic
potential of VC - loaded microspheres physically mixed with or without amphotericin
B was evaluated in adult mice by oral immunization in comparison to VC solution.
The immunogenicity of VC - loaded microparticles mixed with amphotericin B in
evoking Vibrio - specifi c serum IgG and IgM responses was higher than that of VC -
loaded microparticles only [228, 229] . However, VC was loaded in different polymer
compositions (50 : 50 PLGA, 75 : 25 PLGA, and PLA/PEG blended), the higher
antibody responses and serum IgG, IgA, and IgM responses were obtained when
sera from both VC - loaded 75 : 25 PLGA and PLA/PEG - blended microparticles
immunized mice were titrated against VC solution [230] .
Japanese Encephalitis Virus ( JEV) Japanese encephalitis is a disease that is
spread to humans by infected mosquitoes in Asia. It is one of a group of
mosquito - borne viral diseases that can affect the central nervous system and
cause severe complications and even death. Vaccination is one of the ways of
treating it. JEV vaccine was encapsulated in PLGA microspheres by a double -
emulsion technique and infl uences of various process variables such as stirring
rate, types and concentration of emulsifi er, and polymer concentration were
studied on size, size distribution, and biodegradation. The mean size of microspheres
decreased with increasing speed, increasing concentration of emulsifi er,
and decreasing polymer concentration. Rate of biodegradation of nonporous
microspheres was slower than that of porous microspheres, leading to the conclusion
that PLGA microspheres can be used to apply oral vaccination through
Peyers patches across the gastrointestinal tract (GIT) [231] .
Several approaches to develop an improved JEV vaccine are in progress in
various laboratories. Of these, immunization of mice with plasmid DNA encoding
JEV envelope (E) protein has shown great promise. The technology, developed by
Kaur et al. [232] , involved the adsorption of DNA onto cetyltrimethyl - ammonium
bromide (CTAB) containing cationic poly(lactide - co - glycolide) (PLG) microspheres.