Evaluating anti-Orthopoxvirus antibodies in individuals from Brazilian rural areas prior to the bovine vaccinia era

Abstract

Vaccinia virus naturally circulates in Brazil and is the causative agent of a zoonotic disease known as bovine vaccinia (BV). We retrospectively evaluated two populations from the Amazon and Southeast Regions. BV outbreaks had not been reported in these regions before sample collection. Neutralising antibodies were found in 13 individuals (n = 132) with titres ranging from 100 ≥ 6,400 neutralising units/mL. Univariate analysis identified age and vaccination as statistically significant risk factors in individuals from the Southeast Region. The absence of detectable antibodies in vaccinated individuals raises questions about the protection of smallpox vaccine years after vaccination and reinforces the need for surveillance of Orthopoxvirus in Brazilian populations without evidence of previous outbreaks.

Seroprevalence of Orthopoxvirus in rural Brazil: insights into anti-OPV immunity status and its implications for emergent zoonotic OPV

“…The prevalence of anti-OPV neutralizing antibodies observed in this study (30.1 %) was similar to those reported in a retrospective study performed in 2010 in Amazon region (27.9 %) [ 14 ], and higher when compared to 9.8 % found in another study done with two distinct Brazilian populations [ 16 ]. Although in these two studies [ 14 , 16 ] the populations analyzed had some different characteristics and contexts for OPV serosurvey related to our study, other characteristics are similar, such as subsistence agriculture and farming as the main economic activities. Another Brazilian study carried out in the State of Rio de Janeiro showed a seropositivity of 43 % [ 13 ], where participants were from rural properties affected by outbreaks and most of them were infected, presenting clinical signs and symptoms.…”

“…Seroprevalence studies of OPV in different populations worldwide have also been used as a marker for the status of protection elicited by vaccination [ 14 , 16 , 23 , 25 , 27 , 28 , 30 , 31 ]. In this study, we have assessed only anti-OPV protective immunity (ie neutralizing antibody titers) and our findings demonstrated that 53.1 % of presumed vaccinated individuals presented OPV neutralizing antibodies, in comparison to 57.1 % of true vaccinees (represented by those with vaccine take), a non-significant difference ( p > 0.05).…”

“…The OPV seroprevalence has been used as an indicator of wild OPV exposure/circulation [ 5 , 14 – 16 , 35 , 36 ]. The prevalence of anti-OPV neutralizing antibodies observed in this study (30.1 %) was similar to those reported in a retrospective study performed in 2010 in Amazon region (27.9 %) [ 14 ], and higher when compared to 9.8 % found in another study done with two distinct Brazilian populations [ 16 ]. Although in these two studies [ 14 , 16 ] the populations analyzed had some different characteristics and contexts for OPV serosurvey related to our study, other characteristics are similar, such as subsistence agriculture and farming as the main economic activities.…”

“…Nowadays, individuals less than 35 years were not vaccinated against smallpox and most of those over 35 did not receive booster immunizations since the early 70s. Therefore, immunity to smallpox and consequently to other zoonotic OPV is considered low or non-existent in the current populations [ 3 , 10 – 16 ].…”

Vaccinia virusdetection in dairy products made with milk from experimentally infected cows

“…However, human subclinical infections could not be ruled out. There is evidence of positive serology tests detecting anti‐orthopoxvirus (OPXV) antibodies in habitants of communities that have never had contact with diseased cattle, but have shown protective antibodies to the disease (Figueiredo et al., ; Mota et al., ). Furthermore, OPXV seroprevalence and possible exposure factors related to VACV infections were determined in humans who lived in regions that had outbreaks of BV in Brazil (Costa et al., ).…”