Cryptosporidium parvum is a protozoan parasite that causes diarrheal illness in a wide range of mammalian hosts, including humans. Characteristic serum immunoglobulin G (IgG) antibody responses to antigens in the 27-and 17-kDa size ranges have been shown to develop after infection, and several enzyme-linked immunosorbent assay (ELISA) and Western blot assay formats have been used to measure these IgG levels in human serum. Using a collection of serial samples from laboratory-confirmed cryptosporidiosis patients, we compared the results obtained by using two new ELISAs with those obtained with two different Western blot assays. When assayed with the large-format Western blot, 97% of the 67 patients had a demonstrable antibody response on at least one occasion. The Cp23 ELISA correctly identified 93% of the samples that had a 27-kDa response by Western blot and 100% of the negative samples. The Triton antigen ELISA detected 77% of the samples that had a 17-kDa response by Western blot and 88% of the negative samples. The sensitivity of the Triton antigen assay was higher for samples collected between 16 and 92 days after the onset of symptoms (96%). The minigel-format Western blot did not compare favorably with the large-format blot for the detection of antibodies to the 27-kDa antigen (71% sensitivity). A half-life of about 12 weeks was estimated for antibodies to both the 27-and 17-kDa antigens. We believe the Cp23 and Triton antigen ELISAs will be useful in epidemiologic studies of the prevalence of Cryptosporidium infection in the population.Cryptosporidium parvum, a protozoan parasite that invades the intestinal epithelium of a wide range of mammalian hosts, causes a self-limiting but sometimes severe diarrheal illness in immunocompetent humans (2). However, in those with compromised immune systems, the disease can be debilitating, chronic, and life threatening (4, 23). Because of its ubiquitous distribution in the environment, its small size, and its resistance to standard chlorination techniques, C. parvum contamination of drinking water may pose a significant public health risk (1,11,12). Numerous outbreaks have been traced to contaminated water, and waterborne outbreaks have even occurred in communities served by state-of-the-art water treatment facilities (3,8,9,15). To conduct epidemiologic studies to assess the risks of C. parvum infection that may be associated with drinking water and other potential sources of exposure, new serologic assays that are rapid, sensitive, and specific are needed.Characteristic serum immunoglobulin G (IgG) antibody responses have been shown to develop in humans after C. parvum infection. As shown by Western blot analysis of serum samples collected from outbreak patients and human volunteers, the antibody response is consistently directed toward two low-molecular-weight antigen families: one in the 27-kDa size range and a second in the 17-kDa size range (16-19, 25, 26).We recently reported the development of two enzyme-linked immunosorbent assays (ELISAs) for the detection ...

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In the first experiment, osmotic pressure of semen and seminal plasma in a semen sample from each of the 20 mature NiliRavi buffalo bulls was determined. In the second experiment, effects of osmotic pressure on motility (%), plasma membrane integrity (%) and viability (%) in fresh and frozen-thawed semen samples from each of the seven mature Nili-Ravi buffalo bulls was determined. In the first experiment, seminal plasma was harvested by centrifuging semen at 400 3 g for 10 min at 378C and osmotic pressure was determined using an osmometer. In the second experiment, motility (%) was assessed in fresh and frozen-thawed (378C for 30 s) semen samples using a phase-contrast microscope (3400). Plasma membrane integrity (%) was determined by mixing 50 ml each of fresh and frozen-thawed semen with 500 ml of solution having an osmotic pressure of 50, 100, 150, 190 or 250 mOsm/l (hypotonic treatments of fructose 1 sodium citrate) and incubating at 378C for 1 h. Viability (%) of fresh and frozen-thawed spermatozoa before and after challenging them to osmotic pressure (hypotonic treatments) was assessed using supravital stain under a phase-contrast microscope (3400). In the first experiment, the mean 6 s.e. osmotic pressures of the buffalo semen and seminal plasma were 268.8 6 1.17 and 256.0 6 1.53 mOsm/l, respectively. In the second experiment, motility (%) decreased (P , 0.05) in frozen-thawed semen samples as compared with fresh semen (60.1 6 1.34 v. 81 6 1.57, respectively). The plasma membrane integrity (%) and magnitude of osmotic stress in fresh and frozen-thawed semen samples was higher (P , 0.05) at 50, 100, 150 and 190 mOsm/l as compared with 250 mOsm/l. Loss of viability (%) in fresh and frozen-thawed semen samples was higher (P , 0.05) at 50 mOsm/l (59% in fresh, 70% frozen thawed) as compared with other osmotic pressures, while it was lowest at 250 mOsm/l (4.1% for fresh, 9.7% frozen thawed). In conclusion, osmotic pressure of Nili-Ravi buffalo semen and seminal plasma is determined. Furthermore, variation in osmotic pressure below 250 mOsm/l is not favorable to fresh and frozen-thawed buffalo spermatozoa.

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