WO1998051338A1

WO1998051338A1 - Improved method for administration of vaccine against shigella infections

Info

Publication number: WO1998051338A1
Application number: PCT/US1998/010042
Authority: WO
Inventors: Thomas L. Hale; Trinka S. Coster
Original assignee: US Army Medical Research and Development Command
Current assignee: US Army Medical Research and Development Command
Priority date: 1997-05-16
Filing date: 1998-05-15
Publication date: 1998-11-19
Anticipated expiration: 1999-11-16

Abstract

A new method for vaccinating a susceptible host against Shigella species comprises the steps of: 1) administering a buffering solution to a vaccinee in an amount sufficient to buffer acidity of the upper gastrointestinal tract, then 2) administer a dose of about 104 CFU of Shigella organisms in alkaline solution. The method reduces morbidity while providing excellent protection against shigellosis.

Description

Title: IMPROVED METHOD FOR ADMINISTRATION OF VACCINE AGAINST SHIGELLA INFECTIONS

Field of the Invention;

This invention relates to the field of vaccination against shigellosis. While other means of achieving protection from shigellosis are known, the instant invention makes it possible to administer a single, smaller dosage than was previously suggested for purposes of obtaining protection.

Background of the Invention:

A transformed Shigella has been disclosed in European application EP 351322. That disclosure suggests that the preferred dosage for administration contains 10⁸ to 10¹¹ cells of the lyophilized Shigella. At this level, the subjects often developed signs of morbidity related to shigellosis, including diarrhea and elevated temperature. Using the methods of the instant invention, it is possible to reliably protect from shigellosis using a smaller dosage of organisms whilst avoiding uncomfortable side effects which developed when using the large number of organisms as suggested by the prior art.

Description of the Invention:

This invention relates to means for administration of organisms to protect against intestinal infection. Using means of the instant invention it was possible to obtain protection from shigellosis by administration of one dose of about 10⁴ colony forming units (CFU) of Shigella. The method consists of administration of a single dose of 10,000 CFU of Shigella organisms characterized by the ability to bind Congo red dye when cultured on a Trypticase Soy Agar plate.

The method of the invention for vaccinating a susceptible host against Shigella species comprises the steps of:

1) administering a buffering solution to a vaccinee in an amount sufficient to buffer acidity of the upper gastrointestinal tract, then

2) administer a dose of about 10⁴ CFU of Shigella organisms in buffer solution.

In a preferred embodiment reconstituted CS602 product is diluted to attain the 10,000 CFU of organisms suspended in 30 ml of sodium bicarbonate solution (3.2 g per 240 ml of water) . The vaccinee ingests 120 ml of the sodium bicarbonate solution (3.2 g/240 ml of water) five minutes before ingesting the vaccine dose of 10,000 CFU suspended in 30 ml of bicarbonate solution.

Using the method above (120 ml bicarbonate solution followed in five minutes by 30 ml bicarbonate solution containing suspended organisms) , three Phase I dose selection studies of SC602 were performed in the clinical isolation ward of the United States Army Medical Research Institute for Infectious Diseases at Ft. Detrick, Maryland. In the first study increasing doses of SC602 were tested in small groups of volunteers. Transient fever was recorded in one volunteer and 2 of 3 volunteers experienced mild to moderate constitutional symptoms after ingesting doses of 2.3 X 10⁷ CFU of the vaccine. When the dosage was increased to 2.9 X 10⁸ CFU, 2 of 3 volun- teers had febrile diarrhea and moderate to severe constitutional symptoms. Since this study showed that 10⁸ CFU is a reactogenic dose of the SC602 vaccine, a second Phase I trial was designed to evaluate the safety of a 10⁶ CFU dose of SC602 in a group of fifteen volunteers. Seven of the latter volunteers experienced diarrhea and five had fever (Table 1) . A total of 10 (66%) vaccinees had one or both reactions and the symptoms of one vaccinee met the definition of severe shigellosis. Hence, it was feared that the 10⁶ dosage of SC602 was too reactogenic for vaccine use. A third Phase 1 trial was performed in 12 volunteers using a dosage of 1 X 10⁴ CFU (Table 1) . One volunteer met the definition of diarrhea after ingesting this dose of SC602, but this individual experienced only mild intestinal symptoms. Compared to the 10⁶ dosage, the 10⁴ CFU dose of SC602 appeared to be more appropriate for administration under the conditions wherein bicarbonate is administered to buffer the acidity of the upper intestinal tract. Robust intestinal colonization was observed in all volunteers ingesting >_.10⁴ CFU of SC602 vaccine. For example, 8 of 15 volunteers inoculated with 2 X 10⁶ CFU excreted the organisms until Ciprofloxacin treatment commenced twelve days after vaccination. After vaccination with 1 X 10⁴ CFU of SC602, 11 of 12 volunteers shed shigellae until Ciprofloxacin treatment commenced the eighth day. Quantitative plate counts performed on all stools passed by vaccinees indicated excretion of 10⁵ to 10⁶ CFU/gm of stool, regardless of the initial dose of vaccine. Analysis of IgA antibody secreting cells recognizing S. flexneri 2a LPS showed that 7 of 12 volunteers who received 10⁴ CFU of SC602 experienced significant mucosal immune stimulation. It was surmised that the gradual, persistent intestinal colonization that follows ingestion of this dose of vaccine elicits mucosal immune responses but minimizes the massive inflammatory response that portents the symptomatology of shigellosis . Table 1. Summary of Phase 1 trials

D arrhea: two or more grade 3 stools within 48 hours equaling 200 ml or one grade 3 stool of >300 ml within 24 hours. Dysentery; one or more >grade 3 stools with gross blood.

Brief description of outpatient study plan:

A total of 35 volunteers were recruited from the District of Columbia, Baltimore and Frederick, Maryland. Two of these subjects ingested only bicarbonate placebo, while 33 received either 3 X 10 or 5 X 10 CFU of SC602 in bicarbonate buffer. Fever was documented by having vaccinees use an orally administered Tempa-Dot indicator and recording other symptoms in a diary. On study days 1-10, each volunteer reported daily to the clinical center to review these diaries and to deliver inoculated stool culture plates for microbiological work-up. On study days 11-42, review of diaries and delivery of inoculated stool culture plates occurred three times per week. All vaccinees were treated with ciprofloxacin on day 36 to terminate the study.

Summary of current SC602 clinical data:

Table 1 summarizes the clinical and bacteriological parameters associated with ingestion of 1 - 5 X 10 CFU of SC602 in three Phase 1 trials. In the 1996 trial, one volunteer experienced diarrheal stools associated with ingestion of this dosage. During the 1997 outpatient study, three additional vaccinees reported 3 to 5 small volume diarrheal stools over a period of a few hours. One of these volunteers had a fever of 102.5 °F and another had slight fever of 100.6 °F. The diarrhea and/or fever reported by vaccinees during the November study was of short duration and did not prevent normal activities.

Excretion of SC602 : Table 1 indicates that all volunteers ingesting -10 CFU of SC602 (with bicarbonate buffer) excreted the vaccine on at least one occasion. This robust intestinal colonization by SC602 for one or two weeks is undoubtedly responsible for the solid immunity induced by SC602 against shigellosis. In the daily analysis of vaccine excretion, volunteers who shed vaccine intermittently were considered to be colonized from the first positive culture until the day when all subsequent cultures were negative for SC602. By this criterion, the mean period of colonization was 12 days, and 5-10% of vaccinees were colonized for over four weeks.

Summary of clinical results from Phase 1 trials SC602

The results of the third Phase 1 study using 1 X 10⁴ CFU of SC602 were considered sufficiently promising to justify an S. flexneri 2a challenge study. Seven vaccinees who had received this dose were readmitted to the clinical ward six weeks after vaccination along with 7 unvaccinated controls. All were challenged with 2 X 10³ CFU of virulent S. flexneri 2a 2457T in sodium bicarbonate. Three vaccinees experienced transient diarrhea with minimal associated symptoms in the absence of fever, but all vaccinees were protected against febrile diarrhea, dysentery or shigellosis. In contrast, 6 of 7 unvaccinated volunteers experienced severe shigellosis as a result of challenge. The scientific literature contains no example of similar levels of protection against experimentally induced shigellosis as a result of vaccination.

Claims

What we claim is :

1. A composition of matter comprising about 10⁴ CFU of Shigella organisms in alkaline solution.

2. A method of vaccinating against Shigella species by administration of a composition of claim 1.

3. A method of vaccinating against Shigella species compris- ing the steps of:

2) administering a dose of about 10⁴ CFU of Shigella organisms in buffering solution.

4. A method of claim 3 wherein the buffering solution is rendered alkaline by addition of bicarbonate.

5. A method of claim 4 wherein the alkaline solution of about 120 ml is administered about 5 minutes before administration of the dose containing Shigella organisms.

6. A composition of claim 1 containing bicarbonate