Treatment strategies for cryptosporidiosis

Bumped-Kinase Inhibitors for Cryptosporidiosis Therapy

Bumped kinase inhibitors (BKIs) of Cryptosporidium parvum calcium-dependent protein kinase 1 (CpCDPK1) are leading candidates for treatment of cryptosporidiosis-associated diarrhea. Potential cardiotoxicity related to anti-human ether-à-go-go potassium channel (hERG) activity of the first-generation anti-Cryptosporidium BKIs triggered further testing for efficacy. A luminescence assay adapted for high-throughput screening was used to measure inhibitory activities of BKIs against C. parvum in vitro. Furthermore, neonatal and interferon γ knockout mouse models of C. parvum infection identified BKIs with in vivo activity. Additional iterative experiments for optimum dosing and selecting BKIs with minimum levels of hERG activity and frequencies of other safety liabilities included those that investigated mammalian cell cytotoxicity, C. parvum proliferation inhibition in vitro, anti-human Src inhibition, hERG activity, in vivo pharmacokinetic data, and efficacy in other mouse models. Findings of this study suggest that fecal concentrations greater than parasite inhibitory concentrations correlate best with effective therapy in the mouse model of cryptosporidiosis, but a more refined model for efficacy is needed.

Cryptosporidiosis and the challenges of chemotherapy

Cryptosporidium parvum is a protozoan parasite that infects the epithelial cells of the small intestine causing diarrheal illness in humans. Cryptosporidium has a worldwide distribution and is considered an emerging zoonosis. Despite intensive efforts to develop workable experimental models, and the evaluation of over 200 chemotherapeutic agents, adequate therapies to clear the host of these parasites are still lacking. The reasons for the lack of drug efficacy are probably manifold and may include the unusual location of the parasite in the host cell, distinct structural and biochemical composition, or its ability to either block import or rapidly efflux drug molecules. Understanding some of the basic mechanisms by which drugs are transported to the parasite and identifying unique targets is a first step in developing effective therapeutic agents.

Treatment of non-HIV cryptosporidial diarrhea with azithromycin

OBJECTIVE

To report a patient with non-HIV-related cryptosporidial diarrhea who was treated effectively with a regimen of high-dose azithromycin therapy.

CASE SUMMARY

A 42-year-old immunocompetent man contracted cryptosporidiosis from an ailing calf that he had purchased. He finally was admitted to the hospital because of excessive weight loss and profuse diarrhea. The patient was started on a course of high-dose azithromycin therapy and symptoms resolved within 48 hours. Follow-up stool cultures were negative for the parasite.

DISCUSSION

Although usually associated with immunocompromised patients, cryptosporidiosis occurs in immunocompetent hosts in a significant portion of the reported cases each year. Although self-limiting in most cases in this population, the disease can be severe at times and require treatment. Paromomycin therapy has been used in the past with good results. Although macrolides have had erratic effects against this parasite in the past, azithromycin (an azalide) demonstrated good efficacy in this patient.

CONCLUSIONS

Azithromycin has demonstrated that it may be an effective option for the treatment of cryptosporidiosis in immunocompromised patients. Studies involving its use in immunocompromised patients are currently underway.

Update on the management of intestinal cryptosporidiosis in AIDS

OBJECTIVE

To update readers on the pharmacotherapeutic management of cryptosporidiosis in patients with AIDS.

DATA SOURCES

A MEDLINE search was used to identify pertinent literature. Additionally, programs and abstracts from the 33rd Interscience Conference on Antimicrobial Agents and Chemotherapy; the 1st International Conference on Macrolides, Azalides, and Streptogramins; the 93rd American Society for Microbiology Meeting; and the 6th and 7th International Conferences on AIDS were used.

DATA EXTRACTION

Available data from in vitro, animal, and human experiments were reviewed.

DATA SYNTHESIS

Intestinal cryptosporidiosis in patients with AIDS can be a life-threatening opportunistic infection. However, there can be significant variability in disease expression, including spontaneous remission. Supportive care with hydration and nutritional supplementation remains a hallmark of therapy. Unfortunately, there is no proven specific pharmacotherapy of cryptosporidiosis in patients with AIDS. Numerous agents have been analyzed for in vitro activity and efficacy in experimental animal models and actual human cases of the infection, including paromomycin, azithromycin, clarithromycin, octreotide, hyperimmune bovine colostrum, bovine transfer factor, and many others. Because limited numbers of controlled trials have been conducted with potential therapeutic agents, the majority of the information to date is preliminary in nature.

CONCLUSIONS

Despite the availability of some evolving and potentially promising treatment modalities, further controlled clinical trials are necessary to evaluate the role of pharmacotherapy for intestinal cryptosporidiosis in patients with AIDS.

Treatment of cryptosporidial diarrhea in an AIDS patient with paromomycin

OBJECTIVE

To report a case of diarrhea caused by Cryptosporidium in an AIDS patients which was successfully treated with paromomycin.

CASE SUMMARY

An AIDS patient with a 12-month history of cryptosporidial diarrhea unresponsive to other treatment measures was treated with paromomycin 500 mg q6h for 14 days. Before initiating therapy, the patient was experiencing, on average, 20 bowel movements per day and had lost more than 25 kg. After therapy was initiated, the number of bowel movements dropped to 1-2 per day and the patient began to gain weight. The diarrhea recurred when therapy was discontinued. After retreatment for 14 days with paromomycin 500 mg q6h, the diarrhea stopped. The patient has not had a recurrence of Cryptosporidium diarrhea, stool cultures remain negative for Cryptosporidium oocysts, and the patient has regained most of the weight.

DISCUSSION

Literature concerning the use of paromomycin for the treatment of cryptosporidiosis is discussed. A treatment algorithm for the management of cryptosporidiosis in AIDS patients is presented.

CONCLUSIONS

We believe that we have presented a clear example of a case in which paromomycin was effective in treating and eradicating intestinal cryptosporidiosis in an AIDS patient. Paromomycin is the most effective agent available to date for the treatment of this devastating complication of AIDS.

Coccidian infections in AIDS. Toxoplasmosis, cryptosporidiosis, and isosporiasis

Cryptosporidium sp. and Isospora belli are coccidian protozoan parasites that were long recognized as pathogens for many animal species. The medical community became acquainted with these organisms with the advent of AIDS. Both parasites are associated with persistent, debilitating enteritis and, in the case of Cryptosporidium, biliary tract involvement in patients with AIDS. For the immunocompetent host, infection with these two pathogens usually results in self-limited diarrhea. Cryptosporidiosis appears to occur more often than isosporiasis, but the true prevalence of both infections for various populations of humans is unknown. Clinically, cryptosporidiosis is indistinguishable from isosporiasis. Diagnosis is based on finding the acid-fast (red staining oocyst in stained fecal specimens). There is no known effective therapy for cryptosporidiosis, whereas patients with isosporiasis respond promptly to treatment with trimethoprim-sulfamethoxazole. Patients with AIDS and isosporiasis have a high relapse rate after achieving complete remission and therefore need to be maintained on suppressive therapy. Much more needs to be learned about these two fascinating, "newly recognized" parasites.