quite safe and well tolerated. Researchers are currently in the middle of an appropriate Phase II study of the safety and immunogenicity of this vaccine, using an appropriate adjuvant.
In response to questions from the audience, Dr. Monath added the following:
Other groups are investigating other potential immunogens, including vacuolating cytotoxin and other molecules. In the end, some combination of antigens including urease and others may be required to produce a successful vaccine.
Urease is present on the surface of the bacterium, but researchers don’t know how it gets there. They have not discovered the signal sequence. One theory is that as other bacteria are lysed and release cytoplasmic urease, the urease is scavenged by bystander bacteria and collected on their surface.
HP infection is densest in the antrum of the stomach, but there are also bacteria present in the corpus and even the cardia. There is no clear or well-understood relationship between the site of infection and the subsequent site of ulceration. The mechanism is better understood: infection compromises the protective mucous layer as a result of HP virulence factors—mucinase, ammonia, etc., and this exposes the a region of mucosa to acid.
HP have been found colonizing dental plaque, as well as the stomach, but there is no evidence that HP replicates in the gut.
Incidence and Burden. The incidence of gonococcus infections has declined dramatically in Europe, by 80 to 99 percent in most countries and almost to extinction in Sweden. It has also declined by about 40 percent in the United States over the past few years, but the social economics of the disease are such that it is unlikely to disappear from its core regions, which include the inner cities and the rural South. Seroprevalence may be a few percent to 5 percent in these U.S. areas, and gonorrhoea remains a very common disease in much of the rest of the world. In Africa, for example, 5 or 10 percent of many study populations are carrying gonococcus at any one time.
Gonococcus is important not because of its acute symptoms but rather because it causes tubal infertility. In this country, it is probably the number-2 cause of tubal infections, after chlamydia, causing about 100,000 cases per year of salpingitis, ectopic pregnancy, and infertility.