Recent studies suggest that a group of Chlamydia strains known as TWAR, which are now proposed to be a new species called Chlamydia pneumoniae, may be a frequent cause of respiratory disease in the United States and many other countries. Current serotesting methods do not allow rapid screening of large numbers of samples to distinguish C. trachomatis exposure from C. pneumoniae exposure. We developed an enzyme immunoassay to decrease cross-reactivity between immunoglobulin G antibodies reactive with C. trachomatis and C. pneumoniae. Elementary bodies of C. trachomats or C. pneumoniae were treated with a detergentchelating solution to decrease the reactivity of the common lipopolysaccharide antigens. Sera from four groups of patients, totaling 143 persons, were tested by this assay. The prevalences of titers of .128 to C. trachomatis and C. pneumoniae, respectively, were as follows: (i) for 23 women seropositive for C. trachomatis by the microimmunofluorescence test, 21 (91%) and 18 (78%); (il) for 50 adult blood donors, 13 (26%) and 39 (78%);

Chlamydia trachomatis is an obligate intracellular energy parasitic bacterium with a genome of 660 X 10(6) daltons, possessing a plasmid and unique life cycle which includes the differentiation of the infective elementary body to a replicative reticulate body. C. trachomatis is the etiological agent of trachoma, which affects approximately 500 million people in developing countries. Recently it became evident that in industrialised Western nations certain strains of C. trachomatis are the most common cause of sexually transmitted infections such as non-gonococcal urethritis, cervicitis, endometritis, salpingitis and subsequent ectopic pregnancies or infertility, perihepatitis, neonatal conjunctivitis and pneumonia, adult conjunctivitis and epididymitis. Since C. trachomatis infections are often asymptomatic, widespread screening of sexually active young people is needed in order to initiate early antibiotic treatment which may prevent serious complications such as ectopic pregnancies and infertility. Development of sensitive and simple techniques for mass screening for detection of Chlamydia in excretions as well as techniques for detection of specific markers of chronic internal infections (such as Chlamydia specific IgA antibodies) is of great importance.

The rates of the enzymatic cleavage of the side chains of cholesterol and cholesterol sulfate have been studied using subcellular fractions from the adrenal cortex of the rat and cow. Although impermeable to exogenous TPNH, intact mitochondria in vitro can convert doubly labeled [3H]cholesterol [ asS]sulfate into [ aH]pregnenolone [ 36S]sulfate. When Ca2+ is present, exogenously added TPNH accelerates the rates of side-chain cleavage of both cholesterol sulfate and cholesterol. The addition of isocitrate also increases the oxidation of both substrates. However, succinate accelerates 0 ne of the metabolic fates of cholesterol sulfate, a ubiquitous compound found in many mammalian tissues and body fluids, is its enzymatic conversion into pregnenolone sulfate ' (Roberts et al., 1967;Raggatt and Whitehouse, 1966;Young and Hall, 1969). The steroid conjugate serves as a substrate for the side-chain cleavage enzyme systems present in the adrenal and in the testes (Ponticorvo and Lieberman, unpublished results), through mechanisms that have been (by about 7 0 x ) the rate of side-chain cleavage of only cholesterol sulfate. The rate of oxidation of cholesterol is only slightly affected by succinate. Determination of the kinetic parameters of the two substrates indicated that the apparent K , for cholesterol sulfate is smaller than that of cholesterol and also that the V,,, for the conjugate is greater than that of the free sterol. Inhibition studies have shown that each of the substrates can inhibit the cleavage of the other. Cholesterol glucuronide inhibits the oxidation of neither cholesterol nor its sulfate.shown to occur with the retention of the sulfate moiety. In this regard, cholesterol sulfate is unique, since all other known esters of cholesterol are not transformed into Czl steroids without prior hydrolysis.The experiments described in this paper were designed to investigate further the role of cholesterol sulfate as a substrate for the adrenal side-chain cleavage enzyme. Whether cholesterol sulfate can be converted into pregnenolone sulfate by t From the Departments of Biochemistry, Obstetrics, and Gynecology,

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