Banca de DEFESA: SAMARA ALVES SANTOS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : SAMARA ALVES SANTOS
DATE: 02/12/2021
TIME: 09:00
LOCAL: defesa virtual por web conferencia
TITLE:

Evaluation of Indirect Immunofluorescence and Western blotting in the detection of serum anti-Giardia duodenalis antibodies

KEY WORDS:

Giardia duodenalis, Diagnosis, Western blotting, Immunofluorescence.

PAGES: 54
BIG AREA: Ciências Biológicas
AREA: Parasitologia
SUBÁREA: Protozoologia de Parasitos
SPECIALTY: Protozoologia Parasitária Humana
SUMMARY:

Giardia duodenalisis considered one of the oldest human parasites with wide distribution worldwide, infecting more than 280 million people a year. Giardiasis is a highly prevalent protozoosis in Brazilian children, with asymptomatic or acute or persistent diarrhea, accompanied by abdominal cramps, flatulence, malabsorption and weight loss. Laboratory diagnosis of this infection is usually performed through the morphological identification of cysts and/or trophozoites in the stool through microscopy. In addition, serological assays such as Indirect Immunofluorescence (IFI), ELISA (Enzyme-linked immunosorbent assay) and Western Blotting (WB) have been used to detect specific antibodies to Giardia in serum. However, there is much controversy regarding the use of these assays as diagnostic tools. Thus, this work aimed to evaluate the performance of Indirect Immunofluorescence (IFI) and Western blotting (WB) assays for the detection of IgG antibodies against Giardia duodenalis in infected individuals. Fecal and serum samples were selected from children from day care centers and their guardians, as well as from users of the Clinical Analysis Laboratory of the Faculty of Pharmacy (LACTFAR-UFBA) infected with Giardia duodenalis, infected with other parasites, or non-parasitized. Sera were analyzed using the IFI and WB technique in order to compare the sensitivity and specificity of the methods and identify immunodominant molecules of the parasite and possible cross-reactions with other parasites. Ninety-seven sera were tested in the IFI at 1:20 and 1:40 seric dilutions, and of these, 40 samples were tested in the WB assay. The sensitivity of the IFI was 97% at the 1:20 dilution of the sera, dropping to 39.4% at the 1:40 dilution. For the WB, the sensitivity was 85.7%, considering the total of 14 sera from patients eliminating Giardia cysts. However, the specificity for IFI ranged from 46.9% to 59.4%, depending on the serum dilution, while in WB it was 75%. Most of the serum samples from patients with amoebas were positive in the IFI at a 1:20 dilution, evidencing a possible cross-reaction, also observed in the WB. Proteins of 25, 27-31 and 45-55kDa were considered immunodominant because they were the most recognized by sera of people infected with G. duodenalis, presenting an exclusive diagnostic sensitivity of each protein of 42.8%, 50% and 57.1% respectively. The agreement between WB and the detection of G. duodenalis in feces by microscopy was considered substantial, Kappa = 0.61, while for IFI the serum dilutions 1:20 and 1:40 were considered low, Kappa = 0, 27 and 0.31, respectively. The agreement between the two serological methods tested was weak with sera diluted 1:20 in the IFI, Kappa = 0.150, or null, with a 1:40 dilution of sera. Constant lifetime exposure to Giardia infection can maintain high levels of specific antibodies in the serum, even without active infection, which may explain the high sensitivity and low specificity of assays. The use of fractionated antigens, as in WB, allows the recognition of specific immunodominant antigens and their combinations or exclusion criteria, which can be used as an alternative test in the diagnosis of giardiasis.

BANKING MEMBERS:
Presidente - 3187360 - MARCIA CRISTINA AQUINO TEIXEIRA
Interna - 2584365 - LUCIANA SANTOS CARDOSO
Externo ao Programa - 1673868 - THIAGO CAMPANHARO BAHIENSE