Serum IgG Responses and Seroconversion Patterns to Cryptosporidium gp15 among Children in a Birth Cohort in South India

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>The correlates of protective immunity to cryptosporidiosis are not well understood. This study was conducted to assess the effect of maternal serum IgG against<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>gp15 on responses to this antigen in children with (cases) and without (controls) PCR-confirmed cryptosporidial diarrhea. Maternal sera (<jats:italic>n</jats:italic>= 129) and sera from cases (<jats:italic>n</jats:italic>= 39) and controls (<jats:italic>n</jats:italic>= 90) collected at 3.5, 9, and 24 months of age were tested for serum IgG against<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>gp15 by enzyme-linked immunosorbent assay (ELISA). Seroconversion patterns were evaluated by estimating probabilities of seroconversion along three time points based on the transition pathways by using a first-order Markov chain process and empirical Bayesian estimates. There was no difference in serum IgG levels or seropositivity rates to gp15 between cases and controls across all time points in children or in IgG levels to this antigen between mothers of cases and controls. The most common transition pathway can be described as a seronegative child at 3.5 months who seroconverts at 9 months and remains seropositive at 24 months. This pattern remained stable irrespective of the serological status of the mother or the case or control status of the child. Children were most likely to be exposed to<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>for the first time between the ages of 3 and 9 months, and most of the children seroconverted by 24 months. The high degree of seroconversion among control children is suggestive of high rates of asymptomatic transmission in this region.</jats:p>

An evaluation of the potential use ofCryptosporidiumspecies as agents for deliberate release

“…Distinct subsets of effector and memory CD4 T cells were shown to develop after infection with C parvum and are believed to mediate protective immunity to re-challenge 57. The role of seroconversion is unclear and studies from areas of endemicity suggest high numbers of asymptomatic seroconverters 58. A pronounced serological response to the cryptosporidial 27 kDa antigen group was, however, shown to be associated with a reduced risk of diarrhoea in immunocompromised subjects (Table 1).…”

Cryptosporidium in humans and animals—a one health approach to prophylaxis

“…Several antigens, aimed at raising immunoglobulin G antibodies, are being developed as vaccine candidates . Some of the best studied are gp 15, cp 15 and cp 23 . The gp 15 antigen is derived from the glycoprotein gp 60, which is cleaved by a parasite serine proteinase into two surface proteins— gp 15 and gp 40, both of which play an essential role in parasite motility and attachment to and invasion of host epithelial cells, and can stimulate γ‐interferon production by peripheral blood mononuclear cells of those previously infected .…”

Cryptosporidium parvum vaccine candidates are incompletely modified with O-linked-N-acetylgalactosamine or contain N-terminal N-myristate and S-palmitate

“…Polymorphisms in Gp15 and Gp40 have been used to distinguish among isolates of C . parvum , while recombinant Gp15 has been used to measure the serological response in epidemiological studies [ 25 – 30 ]. Vaccination studies have been performed using recombinant C .…”