Patent 6,210,684

Antigenic and/or immunoregulatory material derived from Mycobacterium vaccae is useful for delaying the onset of AIDS with or without associated tuberculosis.

DETAILED DESCRIPTION OF THE INVENTION

Therapeutic agents which may be used in the present invention comprise dead cells of M. vaccae, preferably cells which have been killed by autoclaving. The immunotherapeutic agent normally comprises more than 10⁸ microorganisms per ml of diluent, and preferably from 10⁸ to 10¹¹ killed M. vaccae microorganisms per ml of diluent.

The diluent may be pyrogen-free saline for injection alone, or a borate buffer of pH 8.0. The diluent should be sterile. A suitable borate buffer is:

                Na₂ B₄ O₇.10H₂ O          3.63 g
                H₃ BO₃                    5.25 g
                NaCl                      6.19 g
                Tween                     0.0005%
                Distilled Water           to 1 litre

The preferred strain of M. vaccae is one denoted R877R isolated from mud samples from the Lango district of Central Uganda (J. L. Stanford and R. C. Paul, Ann. Soc. Belge Med, Trop. 1973, 53, 389). The strain is a stable rough variant and belongs to the aurum sub-species. It can be identified as belonging to M. vaccae by biochemical and antigenic criteria (R. Bonicke, S. E. Juhasz., Zentr albl. Bakteriol. Parasitenkd. Infection skr. Hyg. Abt. 1, Orig., 1964, 192, 133).

The strain denoted R877R has been deposited at the National Collection of Type Cultures (NCTC) Central Public Health Laboratory, Colindale Avenue, London NW9 5HT, United Kingdom on Feb. 13, 1984 under the number NCTC 11659.

For the preparation of an immunotherapeutic agent which may be used in the method of the present invention, the microorganism M. vaccae may be grown on a suitable solid medium. A modified Sauton's liquid medium is preferred (S. V. Boyden and E. Sorkin., J. Immunol, 1955, 75, 15) solidified with agar.

Preferably the solid medium contains 1.3% agar. The medium inoculated with the microorganisms is incubated aerobically to enable growth of the microorganisms to take place, generally at 32^oC. for 10 days. The organisms are harvested, then weighed and suspended in a diluent. The diluent may be unbuffered saline but is preferably borate-buffered and contains a surfactant such as Tween 80 as described above. The suspension is diluted to give 100 mg of microorganism/ml. For further dilution, borate buffered saline is preferably used so that the suspension contains 10 mg wet weight of microorganisms/ml of diluent. The suspension may then be dispensed into 5 ml multidose vials. Although the microorganisms in the vials may be killed using irradiation e.g. from ⁶⁰ Cobalt at a dose of 2.5 megarads, or by any other means, for example chemically, it is preferred to kill the microorganisms by autoclaving, for example at 10 psi for 10 minutes (115^o-125^oC.). It has been discovered that autoclaving yields a more effective preparation than irradiation.

The immunotherapeutic agent is in general administered by injection in a volume in the range 0.1-0.2 ml, preferably 0.1 ml, given intradermally. A single dosage will generally contain from 10⁷ to 10¹⁰ killed M. vaccae microorganisms. It is preferred to administer to patients a single dose containing 10⁸ to 10⁹ killed M. vaccae. However, the dose may be repeated depending on the condition of the patient.

Although the immunotherapeutic agent will generally be administered by intradermal injection, other routes, e.g. oral administration, can also be used.

For 20 to 50% of African patients with HIV infection tuberculosis is the first symptom in development of AIDS. Tuberculosis infection is associated with significant production of interleukin 6 (IL6) and tumour necrosis factor (TNF). There is evidence to show that the addition of TNF and IL6 to HIV-infected T cells in vitro leads to increased multiplication of the virus. The TNF release associated with tuberculosis infection in an HIV-positive subject may precipitate proliferation of the HIV with consequential disruption of the function of T4 cells in the immune system and production of immunodeficiency.

It is believed that the prevention of tuberculosis or, more specifically, the inhibition of TNF, and IL6 associated (Koch) responses, will have a delaying effect on precipitation of the AIDS syndrome. The agents of the invention are believed to exert an immunomodulatory effect on pre-existent cell mediated necrotizing responses, changing them to a non-necrotizing form of response and it is believed that this is due to decreased production of, or a change in function of, IL6 and TNF. It is also believed that protective immunity against both tuberculosis and leprosy is enhanced.

Among a group of patients being treated for tuberculosis were seventeen who were seropositive by the Wellcome ELISA for HIV1. All the patients were prescribed streptomycin, isoniazid, rifampicin and pyrazinamide for their tuberculosis. Therapy was abbreviated and did not last longer than three months in any case. Eight of the seventeen patients received the therapeutic agent of the present invention and nine received placebo (saline). At follow up about one year later only three of the patients who had received only the anti-tuberculosis drugs had survived and all three of these had advanced tuberculosis. Seven of the eight patients treated with the therapeutic agent of the present invention had become sputum smear negative for acid fast bacilli (i.e. tubercule bacilli) and the general improvement in their condition was similar to that in tuberculosis patients who were not HIV positive. Five of the eight patients had generalised lymphadenopathy at the time of diagnosis. This had resolved at the time of follow-up. The two patients who were retested serologically at the follow-up were found to be negative for HIV1.

It may be advantageous and is within the scope of the invention to use more than one strain of M. vaccae, and/or to include in the therapeutic agent other mycobacterial antigens. Tuberculin may also be included.

The therapeutic agent may also contain BCG (Bacillus Calmette-Guerin) vaccine, in particular the freeze-dried form of the vaccine, to promote its effect.

The therapeutic agent can contain further ingredients such as adjuvants, preservatives, stabilizers etc. It may be supplied in sterile injectable liquid form or in sterile freeze-dried form which is reconstituted prior to use.

M. vaccae may be used as such or as an extract or fractionated portion of the organism to prepare therapeutic agents according to the invention.

Claim 1 of 5 Claims

What is claimed is:

1. A method for delaying the onset of AIDS comprising administering to an HIV positive subject, killed cells of Mycobacterium vaccae in an amount effective to delay the onset of AIDS.

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