IgG AVIDITY WESTERN BLOT USING Toxoplasma gondii rGRA-7 CLONED FROM NUCLEOTIDES 39-711 FOR SERODIAGNOSIS OF ACUTE TOXOPLASMOSIS

Abstract

Toxoplasmosis is an important cause of congenital infection. The present study was performed to evaluate the usefulness of recombinant (r) GRA-7 cloned from nucleotides (n) 39-711 in discriminating between acute and chronic toxoplasmosis. First, commercial IgM, IgG and IgG avidity ELISAs were used to determine the serological profile of the sera. Serum samples were from 20 symptomatic patients with acute infection (low IgG avidity, IgM positive), 10 with chronic infection (high IgG avidity, IgM negative) and 10 with indeterminate IgG avidity (IgM positive) which were tested for IgG avidity status with an in-house developed IgG avidity Western blot using the rGRA-7 recombinant antigen. All 20 sera from cases of probable acute infection showed bands which either faded out completely or reduced significantly in intensity after treatment with 8 M urea, whereas the band intensities of the 10 serum samples from chronic cases remained the same. Of the 10 sera with indeterminate IgG avidity status, after treatment with 8 M urea the band intensities with six sera remained the same, two sera had completely faded bands and another two sera had significantly reduced band intensities. Discrimination between acute and chronic toxoplasmosis was successfully performed by the in-house IgG avidity Western blot.

A Review on the Prevalence of Toxoplasma gondii in Humans and Animals Reported in Malaysia from 2008–2018

“…Lastly, the IgG avidity measures the exact level of the infection as either acute or chronic infection in combination with IgG or IgM. Low IgG avidity indicates that a recent acute infection cannot be excluded (usually less than 4 months), but it may persist at low level after 4 months in about 10% of the infected individuals [ 53 , 54 ].…”

“…A vaccine against T. gondii presents a difficult task with its complex life cycle, stage-specific variation, different strains, and perhaps virulence effect. The acute infection is always the target because the parasite is in the tachyzoite form, which is the active multiplication stage and is found in the blood, which reflects recent exposure [ 54 ]. This is always fatal in immunosuppressed individuals particularly fetuses of pregnant women in their first trimester because the conversion of tachyzoite to the bradyzoite stage will be delayed [ 52 ].…”

“…These antigens included the excretory–secretory antigens (ESA), surface antigens (SAG1, SAG2), rophtry antigens (ROP1, ROP8), and dense granule proteins (GRA2, GRA5, GRA7). The results obtained from works on the improved methods for diagnosis varied among the laboratories [ 27 , 52 , 54 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ]. They reported different levels of sensitivities and specificities of these markers.…”

The Laboratory Diagnosis in Toxoplasma Infection

“…For example, the combinations of SAG2A, GRA2, GRA4, ROP2, GRA8 and GRA7 are potentially useful to detect antibodies IgG in human beings with the infection recently acquired [26], ROP1, SAG1, GRA7, GRA8 and GRA6 are promising to detect speciic IgM antibodies while GRA7 and GRA8 are used to detect IgA speciic antibodies. A speciic protein of sporozoites related with embryogenesis (TgERP) was identiied in a study, it can react with speciic antibodies of oocysts and can be used to detect an early infection by sporozoites implying the oocysts as infection source [27,28].…”

Testes fluorimétricos na sorologia da toxoplasmose humana: detecção simultânea de anticorpos de IgG e IgM específicos

“…Além disso, como demonstram nossos resultados de validação, métodos automáticos comerciais para triagem, muitas vezes, apresentam um ponto de corte baixo, possibilitando resultados falsopositivos. Por isso, existe a necessidade de se utilizarem outros métodos para o diagnóstico sorológico da infecção aguda, como o pareamento de sorologias de IgM e IgG e o teste de avidez de IgG no início da gestação, que são os métodos mais utilizados em laboratórios clínicos, para confirmação de infecção aguda em gestantes (Canales et al, 2010, Deshpande et al, 2013, Elyasi et al, 2010, Kasper et al, 2009, Pour et al, 2011.…”