Subcutaneous fluid and culture chamber and implant technique

A subcutaneous culture chamber for providing a priviledged site for studying infectious disease processes of microorganisms in laboratory animals consists of a pliable polyethylene cylinder with holes at each end. The cylinder can be collapsed and inserted in a flat injector of the plunger type which is employed to force the flattened cylinder through an incision in the skin of an animal into a subcutaneous site. After insertion, the chamber soon expands to operational size and the incision is closed. Thereafter the chamber is suitable for use as an infection site to study the pathogenesis and immunology of microorganisms or for obtaining, with a syringe and needle, tissue fluid usable in a serum bacteriological assay or other study.

FIELD OF THE INVENTION 
This invention relates to apparatus and techniques for studying infectious 
diseases, and more particularly to subcutaneous culture chamber apparatus 
and techniques for in vivo testing of antigens and infectious disease 
agents or immunization mechanisms in laboratory animals. 
BACKGROUND OF THE INVENTION 
The subcutaneous implant procedure provides a priviledged site for studying 
the infectious disease process of microorganisms in laboratory animals. 
Prior to this technique there was no practical immunological model in 
laboratory animals for studying such diseases as Neisseria gonorrhoeae. By 
employing the subcutaneous implant procedure, animal models have been 
developed for N. gonorrhoeae, and in addition the procedure has provided 
the basic techniques required for studying the immunology of other 
microorganisms. The increased use of this procedure in microbiology has 
however resulted in the implantation in animals of chambers of 
unacceptable design, for example, glass rods, plastic test tubes, dropper 
bottles, polyethylene practice golf balls, and the like. These implants 
have produced inhumane suffering in laboratory animals and have not always 
given satisfactory results. 
Further background will be given by examining the following U.S. prior 
patents and publications, which appear to represent the closest prior art 
relating to the present invention, found in the course of a preliminary 
search: 
Delgado, U.S. Pat. No. 3,640,269; 
Arlen, U.S. Pat. No. 3,765,414; 
Schulte, U.S. Pat. No. 3,310,051; 
Bardani, U.S. Pat. No. 3,921,632; 
Wichterle, U.S. Pat. No. 3,971,376. 
Arko, "Implantation and Use of a Subcutaneous Culture Chamber in Laboratory 
Animals", Laboratory Animal Science, Vol. 23, No. 1, 105-106, 1973. 
Arko, "Neisseria Gonorrhoeae: Experimental Infection of Laboratory 
Animals", Science, Vol. 177, 1200-1201, 1972. 
Arko, "An Immunologic Model in Laboratory Animals for the Study of 
Neisseria Gonorrhoeae", Journal of Infectious Diseases, Vol. 129, No. 4, 
451-455, 1974. 
SUMMARY OF THE INVENTION 
Subcutaneous chambers can provide researchers with an easily accessible 
means of studying host-parasite relationships heretofore observed with 
great difficulty or only by in vitro techniques. For example, large 
polyethylene chambers (practice golf balls) have been implanted in rabbits 
to produce fluids containing antibody to viral antigens. Similar chambers 
have been used to study the pathogenesis and immunology of Neisseria 
gonorrhoeae infection is small laboratory animals. 
In general, the technique consists of implanting a chamber subcutaneously 
and allowing the chamber to fill with fluid, such as a serous transudate 
containing white and red blood cells. The chamber becomes suitable for use 
as an infection site to study the pathogenesis and immunology of 
microorganisms, or for obtaining, with a syringe and needle, tissue fluid 
for use as a component in a serum bactericidal antibody assay for N. 
gonorrhoeae, for example. 
Accordingly, a main object of the invention is to provide a novel and 
improved subcutaneous implant apparatus and technique which produces 
minimum discomfort to the animal host and which provides a conveniently 
accessible site for studying the infectious disease process of 
microorganisms in the animal. 
A further object of the invention is to provide an improved subcutaneous 
culture chamber which can be easily inserted, which can expand or collapse 
as fluids are injected into or removed therefrom, and which makes possible 
the sterile collection of tissue fluid by the use of a needle and syringe. 
A still further object of the invention is to provide an improved 
subcutaneous implant chamber which is commercially practical, which is 
designed to prevent the development of pressure necrosis in the host 
animal, and which may be installed by means of a relatively simple and 
safe implantation procedure. 
A still further object of the invention is to provide an improved 
subcutaneous culture chamber which is designed to incorporate living host 
tissue into the wall of the chamber, thereby providing intimate contact 
between the chamber fluid and surrounding tissues, which is pliable and of 
inert material, which is designed to readily expand or collapse as fluids 
are injected into or removed from the implanted chamber, and which has a 
configuration providing for improved host animal comfort and safety by 
preventing the development of subcutaneous pressure necrosis resulting in 
subsequent expulsion of the implant. 
A still further object of the invention is to provide an improved 
subcutaneous culture chamber substantially in the form of a flexible 
cylinder adapted to be inserted subcutaneously in a relatively flattened 
condition and to expand to its normal cylindrical shape after insertion, 
so as to define a culture chamber, said chamber being formed to be 
relatively yieldable at its end portions so as to facilitate insertion by 
allowing the chamber to become more flattened at its forward end portion 
and to become somewhat tapered and thereby facilitate inward subcutaneous 
travel of the flattened chamber, and also to provide greater comfort to 
the host animal by allowing a large degree of wall flexure at the end 
portions of the chamber as compared with that allowed at the intermediate 
portion thereof.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to the drawings, 11 designates a typical subcutaneous implant 
culture chamber according to the present invention. Said typical chamber 
may comprise a polyethylene cylindrical tube of sufficiently small wall 
thickness to be easily flexed and soft enough to be readily penetrable by 
the needle of a hypodermic syringe, for example, of the order of 1 mm., 
but being resilient enough to tend to return to its cylindrical shape 
after being flattened or distorted. In a typical example, the chamber 11 
is 3 cm. in length and 1 cm. in diameter. The tubular chamber 11 is formed 
at its opposite end portions with a plurality of evenly spaced circular 
apertures 12, of the order of 5 mm. in diameter. In said typical example, 
four evenly spaced circular apertures 12 are provided adjacent each end. 
The apertures 12 are employed to increase pliability and to improve animal 
comfort, as well as to increase the area of direct exposure of the 
implanted culture chamber to the surrounding tissue, to aid in 
incorporating living tissue into the wall of the chamber and therefore 
provide intimate contact between the chamber fluid and the surrounding 
tissue. 
The chamber 11 is inserted by means of a relatively flat syringe-type 
injector 13 comprising an elongated flat rectangular tubular main body 14 
provided with an extended end wall 15 defining a peripheral gripping 
flange and with a rectangular plunger block 16 slidably disposed in said 
main body, the plunger block being rigidly connected to a plunger rod 17 
which extends slidably through a central aperture in end wall 15 and which 
is provided at its outer end with a finger-engaging head 18. The flat 
tubular body 14 is shaped to receive the flattened tubular chamber 11 in 
the manner shown in FIG. 3 and to allow the plunger block 16 to push the 
flattened tubular chamber subcutaneously into the host animal, as will be 
presently described. 
To insert the chamber 11, it is collapsed to a flattened shape and placed 
in the flat tubular syringe body 14. This assembly is then sterilized. An 
approximately 2.0 cm. skin incision is then made at the selected site of 
the host animal, one lip of the skin layer 20 is elevated at the incision, 
and the flattened chamber 11 is then forced beneath the elevated skin 
portion by means of the plunger block 16, namely, by forcing the plunger 
rod 17 downwardly relative to body 14, using gripping force between head 
18 and flange element 15. 
Due to the increased yieldability at the forward end of the flattened 
chamber 11 afforded by the holes 12, said forward end becomes somewhat 
tapered in profile as it is forced between the skin layer 20 and the 
subjacent tissue 23, as shown in FIG. 1, which facilitates its forward 
progress beneath the skin layer. After the flattened chamber 11 has been 
completely ejected from the syringe body 14 and forced beneath the 
elevated skin lip at the incision 19 by the plunger block 16, the elevated 
lip of the incision is returned to a flush closed position relative to the 
opposite and may be suitably held to allow the incision to heal. 
The chamber is thus allowed to expand to operational size and may 
eventually reach a shape close to its original cylindrical shape. In a 
typical embodiment, such as is shown in FIGS. 2 and 5, approximately one 
week after implantation the chamber 11 is suitable for use as an infection 
site to study the pathogenesis and immunology of microorganisms, or for 
obtaining, such as by a hypodermic syringe 21 with a sterile needle, 
biofiltered tissue fluid 22, for example, tissue fluid which may be used 
as a fresh complement component in a serum bactericidal antibody assay for 
N. gonorrhoeae. 
The chamber 11, being of pliable material, is adapted to expand or collapse 
as fluids are injected into or removed from the implanted chamber. This 
makes possible the sterile collection of moderate amounts of tissue fluid 
by using a conventional hypodermic syringe 21. 
As above mentioned, the subcutaneous culture chamber 11 is provided with 
multiple openings 12 which, together with the open ends of the chamber, 
allow the incorporation of host tissue into the wall of the chamber, 
therefore providing intimate contact between the chamber fluid 22 and 
surrounding tissues. In addition, the subcutaneous culture implant chamber 
11 consists of pliable inert material and is designed to expand or 
collapse as fluids are injected into or removed from the implanted 
chamber. The yieldable-end configuration of the implant provides for 
greater host animal comfort and safety by preventing the developement of 
subcutaneous pressure necrosis resulting in subsequent expulsion of the 
implant. 
The purpose of the subcutaneous culture chamber implant is to provide an 
immunologically priviledged site in laboratory animals for studying the 
host-parasite interaction in the infectious disease process of pathogenic 
microorganisms for which other research models are either not practical or 
unobtainable. By using the described chamber implant in which the host 
animal's subcutaneous and connective tissues form a living part of the 
implant wall, the natural resistance of the host to the infectious agent 
is temporarily reduced. This probably occurs through the selective 
retention from the chamber fluid of certain serum components which do not 
normally penetrate the wall of capillary blood vessels in the surrounding 
tissue. This permits the experimental disease agent to become established 
in an in vivo site which is accessible for repetitive sampling by needle 
and syringe of tissue fluid, antibodies, and cells involved in the disease 
process being studied. As the disease process continues, pathogenic 
lesions as well as humoral and cellular resistance to the disease agent 
develops in the fluid and wall tissue surrounding the implant, simulating 
the conditions that occur in some natural infectious diseases. By using 
the subcutaneous culture chamber implant herein described, these 
pathological and immunological factors can be studied in a research animal 
such as the guinea pig, therefor avoiding many of the medical/legal 
problems surrounding similar research in human subjects. 
While a specific embodiment of an improved subcutaneous fluid and culture 
chamber and a related implant technique has been disclosed in the 
foregoing description, it will be understood that various modifications 
within the scope of the invention may occur to those skilled in the art. 
Therefore it is intended that adaptations and modifications should and are 
intended to be comprehended within the meaning and range of equivalents of 
the disclosed embodiment.