The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.. months (followed by a multiple linear regression model. With regards to matAb titres, after controlling for birth weight level, birth order levels and being born in or out of an epidemic, using a multiple linear regression model, a univariate analysis was initially performed, and subsequently all variables, irrespective of significance level at univariate analysis, combined. The matAb titres for the infected groups remained significantly lower (P?=?0.011) when compared to the noninfected groups (3.02 log AU versus 2.81 log AU; t?=?2.32, df?=?91.46, P?=?0.011; 1 tail; an ELISA-confirmed serological response at the at the 2-fold seroconversion cut-off level). It was noted that only cord blood levels (P<0.001) affected the rate of decay of the two population subgroups (non-infected and infected children), the remaining risk factors having no effect. With reference to the rate of decay or differences in gradient of matAb decline between these two population subgroups however, no differences (?0.009 versus ?0.007, t?=??1.47, df?=?109.39, P?=?0.145; 2 tail) were identified. Discussion RSV specific matAb and infection were investigated in a birth cohort comprising 635 children in Kilifi District. The distribution, duration and risk factors of RSV maternally-derived immunity over the 1st six months of life were explored. At the cut-off point for seropositivity of 1 1.5 log AU (ascertained from the bimodal distribution of the assay results), maternal transfer was deemed to be efficient as approximately 97% of infants displayed RSV-specific matAb at birth. By 6C7 months however, 50% infants were noted to be still seropositive. This is in contrast to earlier studies [6], [7], [25] with the exception of the study by Ebihara et al. [26], in which seroprevalence levels were seen to reach a nadir by 6 months of life, and seroprevalence varied from between 2C16% when carried out by the ELISA, and 21% by both the G- and F-specific (RSV surface glycoproteins) competition ELISA. In the study by Ebihara and colleagues [26], a similar level Angiotensin II of prevalence of 48% was observed. Increasing the cut-off levels for seropositivity from 1.5 to 1 1.8 log AU Angiotensin II and above, resulted in a more rapid decline in seropositivity and a minimum Ab level being attained by 6 months, as previously described [6], [7], [25]. There is little data to indicate what level of systemic anti-RSV Ab provides adequate transudate across the respiratory mucosa to confer protection from infection. The relationship between cut-off level and rate of decay in seroprevalence (Figure 4) provides possible scenarios for the rate of Angiotensin II decay of actual protective titres of RSV antibody which requires clarification. It should be borne in mind that the measurement of ELISA binding titres using a crude extract is an indirect measure of functional Ab. It would have been more suitable to measure neutralizing Ab titres to get a direct measurement of functional Ab following infection and in the presence of matAb. Furthermore, the use of A2 rather than the currently circulating strain in the assay procedure could have led to an under-estimation of seroconversion due to poor cross-reactivity [4]. Over the first 6 months, the pristine T1/2 of RSV-specific matAb in the population without both serologic evidence and/or IFAT-positive indication of infection was estimated as 79 days Angiotensin II (95% CL: 76C81) and matAb had an average duration of 112 days (95% CL: 107C118). This rate of decay is shorter than that observed by Cox et al. [7], Ward et al. [15] and Hacimustafaoglu et al. [25]. These authors calculated rates that varied from between 91C100 days, although it is not clear as to whether the authors included or excluded seronegative individuals with infections in their calculations. This rate for RSV- matAb decay for the Kilifi population however, was longer than that for measles, mumps and rubella [24], [27], and human parainfluenza type 3 [28], which vary from 35C40 and 51 days respectively. Again, however, it is important to recognise the likely difference between the protective potential of matAb to these systemic infections as opposed to protection against RSV at the respiratory mucosa. Our study suggests that the rate of matAb decay does Rabbit Polyclonal to CBX6 not differ between the wider population that also included those who had infections compared to the noninfected population. Angiotensin II This implies that RSV infections below 6 months of age have no significant effect on the rate of RSV-specific matAb decay. In other words, the presence of matAb has a masking effect on infections under.
