Immune responses to cryptosporidium species in HIV/AIDS infected adults attending Kenyatta National Hospital, Nairobi, Kenya
Kanyi, Henry Muriuki
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Cryptosporidium causes significant morbidity and mortality in AIDS patients worldwide particularly in developing countries where ART is not widely available or affordable. In Kenya, approximately 8% of the adult population lives with HIV/AIDS and Cryptosporidium has been reported as the leading indicator of death among adult HIV/AIDS patients. There is very little information about the molecular epidemiology of cryptosporidiosis and no documented data on immune responses to Cryptosporidium in HIV/AIDS patients in Kenya. A number of Cryptosporidium antigens have been found to induce host immune responses in immunocompetent persons, however, their effects in the immunity of immunocompromised individuals are not understood. Glycoprotein 15 (gp15) and Cryptosporidium 23 (Cp23) are conserved Cryptosporidium antigens that trigger host immune responses and are thus potent agents for vaccine development. This study was aimed at evaluating molecular epidemiology and immune responses against Cryptosporidium with an aim of preventing HIV/AIDS disease progression especially in immunocompromised HIV-Cryptosporidium co-infected persons. A total of 164 HIV/AIDS patients, 94p asymptomatic (no diarrhea) and 70 symptomatic (with diarrhea) respectively were recruited. Recruited persons provided stool samples for Cryptosporidium oocysts microscopic examination and blood for immune responses evaluation. Cryptosporidium species were identified through microscopy, and confirmed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) targeting 18S rRNA. Antibodies and IFN-γ responses against Cryptosporidium antigens were assessed by enzyme linked immunosorbent assays (ELISA). In this study, Cryptosporidium species was found to infect both symptomatic and asymptomatic persons. The species found were C. hominis, C. parvum, C. meleagridis, C. muris and C. Canis, with C. hominis being the most prevalent species. On immune responses there was a significant difference between patients with asymptomatic and symptomatic cryptosporidiosis in secretion of serum IgG to Chgp15 (P = 0.005) and Cp23 (P = 0.001) and fecal IgA to Chgp15 (P = 0.002). No significant difference was observed in IgM and IFN-g levels between patients with asymptomatic and symptomatic cryptosporidiosis. Cryptosporidium hominis was found to be associated with majority cases of Cryptosporidium infection in HIV/AIDS adult patients and often recurrent/chronic diarrhea in patients, especially those with low CD4 counts. Serum IgG to Chgp15 and Cp23 and fecal IgA to Chgp15 antibodies were also seen to be protective against diarrhea. These findings indicate that Serum IgG to Chgp15 and Cp23 and fecal IgA to Chgp15 antibodies may be good candidate antigens for vaccine development against Cryptosporidium species. However, study of the roles of CD8+ cells and other cytokines especially Th2 cytokines should be done to establish their effects on the host protective responses against Cryptosporidium observed in this study. These study findings indicate that improvement of immune status especially serum IgG and Innate mucosal IgA may be major remedial measures towards reducing effects of cryptosporidiosis which is a predominant infection in HIV/AIDS infected patients in Kenya.