Cellular responses to Plasmodium falciparum major surface antigens and their relationship to human activities associated with malaria transmission.

Abstract

Abstract. In Brazil, two types of activities have led to the worsening of malarial transmission in the Amazon region: prospecting/mining and agricultural settlements. In the present study, we analyze the cellular response of 52 of these individuals (14 gold-miners and 38 farmers) living within the same endemic area. Two Plasmodium falciparum major surface antigens (recombinant proteins) were used for cellular proliferative assays: circumsporozoite protein and merozoite surface protein-1. The frequency of these cellular responses were significantly higher among the miners (57-64%) than the farmers (10-20%) when either recombinant protein was used. Our data suggest that a higher exposure to malaria of the gold-miners contributed to their higher in vitro cellular response compared with the farmers. These findings point the way to further studies evaluating the influence of risk factors associated with the life styles of different social groups and the immune responses to these antigens.Research directed towards developing an effective vaccine against Plasmodium falciparum has been conducted for decades. 1 The surface antigens of sporozoites and merozoites are of particular interest because they represent two of the major candidates for inclusion in a subunit vaccine. The major constituents of the merozoite surface are polypeptides derived from a high molecular mass precursor protein known as merozoite surface protein-1 (MSP-1). Immunization with proteins derived from MSP-1 has been shown to protect animals from experimental infections, demonstrating its usefulness as a potential vaccine target. 2-5The best characterized of the anti-sporozoite vaccine candidates is the circumsporozoite (CS) protein. 6 Initial clinical trials with the central repeat epitope of the P. falciparum CS protein, (NANP) n , resulted in a low level of protection. 7,8 New clinical trials with the CS protein have been carried out in small number of subjects, 9,10 but only one CS subunit vaccine was shown to be protective. 11 Although these results represent a considerable advance in the development of malaria vaccines, it is still important to better understand the immune mechanisms involved in natural transmission, in which there are multiple parasite strains and the levels of transmission are variable.In Latin America, malaria remains a serious public health problem affecting the lives and health of certain social groups, particularly those engaged in forest-related economic activities, gem mining, and work on road construction and hydroelectric dams. In Brazil, malaria is endemic in the Amazon area, which comprises 51% of the country's territory and harbors only 9% of its inhabitants.12 Malaria has mainly affected the migrant populations coming from malaria-free areas of the country, attracted by opportunities for farming and mining. 13,14 This was largely in response to the agricultural settlement projects of the National Institute of Colonization and Agrarian Reform, whose main emphasis was to start farms. Moreover, stimulated by the gove...

Plasmodium vivax Duffy binding protein: baseline antibody responses and parasite polymorphisms in a well‐consolidated settlement of the Amazon Region

“…2011). Overall, these data corroborate earlier studies, concluding that malaria transmission is a local problem, which varies within a village according to the microepidemiological factors (Carvalho et al. 1999; da Silva‐Nunes et al.…”

Low cellular response in vitro among subjects with long-term exposure to malaria transmission in Brazilian endemic areas.

“…11,15 Cells from adults who reported less than five years of malaria exposure in Brazilian endemic areas also had a significant proliferative response to CS proteins. 7,8,16 The high frequency of proliferative response now observed in the CB group is consistent with those earlier studies. However, a low level of in vitro cellular proliferative response to CS proteins in subjects continuously exposed to P. falciparum and P. vivax transmission for at least 10 years (Terra Nova do Norte group) is reported for the first time in Brazil.…”

Serologically Defined Variations in Malaria Endemicity in Pará State, Brazil

“…For example, gold mining is the predominant activity in the riverine Jacareacanga. It was previously shown that mining populations exhibit acquisition of immunity to malaria [43]. Mining can also contribute to an increase in number of mosquito breeding sites due to extensive borrow pits dug along mining sites, mimicking the riverine floodwater impoundments [9].…”