PROGRESS IN PROTOZOOLOGY

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brate cycle in vitro. Further concentration on the cultivation of the
vector stages of Babesia and Theileria in arthropod tissue culture would
result in the in vitro growth of sporozoites useful for possible immunization
of mammalian hosts.
3
Salivarian Trypanosomes
During the past five years there has been remarkable progress in
the development of culture systems to support the growth of Trypanosoma
brucei sspp. and T. congolense forms infective to mammalian hosts.
Previously only the noninfective procyclic stages could be cultivated
with certainty. In his review of these various methods, Dr. Reto B r u n
also reported in some detail his most significant advances in the cultivation
of bloodstream forms of all three Trypanozoon subspecies and
their relevance to immunization.
(1) Cultivation of Trypanosoma brucei sspp.
(a) Metacyclic Stages
Hitherto when bloodstream forms were added to the commonly used
blood-enriched media and incubated at 28°C or 37°C, they transformed
into procyclic stages corresponding to those in the tsetse fly midgut
and were not infective to mammalian hosts. However, Cunningham
and Honigberg (1977) demonstrated that metacyclic forms infective
to mice, developed in cultures of procyclics of T. b. brucei grown at
28°C in a liquid medium (Cunningham 1977) containing tsetse fly
head-salivary gland explants. This culture system, extended and successfully
applied to many different stocks of T. b. brucei (Cunningham
and Taylor 1979) and several stocks of T. b. gambiense (Jones et
al. 1981), generated metacyclic trypanosomes morphologically (Gardiner
et al. 1980 a) and antigenically (Gardiner et al. 1980 b) similar
to those transmitted by tsetse flies infected with the same stock. In
a series of papers, Nyindo and his co-workers (1978, 1979, 1980) described
the cultivation of metacyclic T. b. brucei in cultures of bovine
cell feeder layers grown in mammalian cell culture media.
(b) Bloodstream Forms
A major achievement in the cultivation of the bloodstream trypanosomes
was reported by Hirumi et al. (1977). He devised a system
consisting of a feeder layer of bovine fibroblast-like cells grown in
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