COMPARTMENTALIZATION OF DEFINED EPITOPES EXPRESSED IN ESCHERICHIA-COLI HAS ONLY A MINOR INFLUENCE ON EFFICIENCY OF PHAGOCYTIC PROCESSING FOR PRESENTATION BY CLASS-I AND CLASS-II MAJOR HISTOCOMPATIBILITY COMPLEX-MOLECULES TO T-CELLS
Mj. Wick et al., COMPARTMENTALIZATION OF DEFINED EPITOPES EXPRESSED IN ESCHERICHIA-COLI HAS ONLY A MINOR INFLUENCE ON EFFICIENCY OF PHAGOCYTIC PROCESSING FOR PRESENTATION BY CLASS-I AND CLASS-II MAJOR HISTOCOMPATIBILITY COMPLEX-MOLECULES TO T-CELLS, Infection and immunity, 61(11), 1993, pp. 4848-4856
The effect of abundance and compartmentalization of antigenic epitopes
expressed in Escherichia coli on phagocytic processing was studied by
expressing fusion proteins containing the epitope from positions 52 t
o 61 of hen egg white lysozyme [HEL(52-61)], which binds the I-A(k) mu
rine major histocompatibility complex class II (MHC-II) molecule or th
e epitope from positions 257 to 264 of chicken egg ovalbumin [OVA(257-
264)], which binds the K(b) murine MHC-1 molecule. Epitopes expressed
as fusion proteins in the outer membrane protein LamB allowed exposure
of the epitopes either at the bacterial surface, in the periplasmic s
pace, or in the cytoplasm. Regardless of epitope compartmentalization
within the bacterium, MHC-H-restricted or MHC-1-restricted presentatio
n to T hybridoma cells occurred after macrophages phagocytosed bacteri
a producing the HEL(52-61) epitope or the OVA(257-264) epitope, respec
tively. Increased epitope abundance within a given microbial compartme
nt resulted in increased processing and presentation to epitope-specif
ic T hybridoma cells. Minor differences in the efficiency of epitope p
rocessing between the constructs was observed, and the HEL or OVA epit
ope exposed in the periplasmic space was processed most efficiently co
mpared with the surface- or cytoplasm-localized epitopes. These differ
ences could be overcome by increasing the amount of epitope per bacter
ium as little as two to five times. The minor differences in processin
g efficiency may be due to differing protein contexts of the epitope a
s well as differing epitope compartmentalizations within the bacteria.
Thus, production of abundant epitope is the important parameter influ
encing processing of epitopes expressed in E. coli to induce T-cell re
sponses rather than targeting of an epitope to a specific bacterial co
mpartment.