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Cryptosporidium parvum merozoites share neutralization-sensitive epitopes with sporozoites
J M Bjorneby1, M W Riggs, L E Perryman
1Department of Veterinary Microbiology and Pathology, Washington State University, Pullman 99164-7040.
Abstract:
Sporozoites and merozoites are stages in the life cycle of Cryptosporidium parvum that can cyclically infect intestinal cells, causing persistent infection and severe diarrhea in immunodeficient patients. Infection by sporozoites can be neutralized by surface-reactive mAb. We show that merozoite infectivity can also be neutralized by surface-reactive mAb. To do this, viable C. parvum merozoites were isolated by differential and isopycnic. centrifugation, and distinguished from sporozoites by transmission electron microscopy. Differential reactivity with a panel of seven mAb was used to determine the amount of sporozoite contamination in isolated merozoite preparations. The isolated merozoites were distinguished from sporozoites (p less than 0.0001) by four sporozoite-specific mAb (16.332, 16.502, 17.25, and 18.357) in an indirect immunofluorescence assay. Three mAb (16.29, 17.41, and 18.44) consistently reacted with both merozoites and sporozoites. Isolated merozoites were infectious for neonatal mice when administered by intraintestinal injection. Infectivity for mice was significantly neutralized (p less than 0.05) when 1 to 2 x 10(5) merozoites were incubated with sporozoite-neutralizing mAb 17.41 or 18.44, before inoculation. Merozoites incubated with an isotype control mAb remained infectious for neonatal mice. We conclude that C. parvum merozoites share neutralization-sensitive epitopes with sporozoites.
Insights
Cryptosporidium parvum merozoite infectivity can be neutralized by specific monoclonal antibodies (mAbs). These mAbs target epitopes shared with sporozoites, offering new strategies for controlling persistent infections.
Area of Science:
- Immunology
- Parasitology
- Microbiology
Background:
- Cryptosporidium parvum sporozoites and merozoites cause persistent intestinal infections, particularly severe in immunodeficient individuals.
- Surface-reactive monoclonal antibodies (mAbs) can neutralize sporozoite infectivity.
Purpose of the Study:
- To investigate whether merozoite infectivity can also be neutralized by surface-reactive mAbs.
- To identify shared neutralization-sensitive epitopes between C. parvum merozoites and sporozoites.
Main Methods:
- Isolation of viable C. parvum merozoites using differential and isopycnic centrifugation.
- Distinguishing merozoites from sporozoites using transmission electron microscopy and indirect immunofluorescence assays with specific mAbs.
- Assessing merozoite infectivity in neonatal mice and neutralization by mAbs.
Main Results:
- Isolated merozoites were distinguished from sporozoites using four sporozoite-specific mAbs.
- Three mAbs reacted with both merozoites and sporozoites.
- Merozoite infectivity in mice was significantly neutralized by mAbs 17.41 and 18.44, which also react with sporozoites.
Conclusions:
- C. parvum merozoites possess neutralization-sensitive epitopes that are shared with sporozoites.
- Surface-reactive mAbs targeting these shared epitopes can neutralize merozoite infectivity, suggesting potential therapeutic applications.