Nielsen Morten A, Vestergaard Lasse S, Lusingu John, Kurtzhals Jørgen A L, Giha Haider A, Grevstad Berit, Goka Bamenla Q, Lemnge Martha M, Jensen James B, Akanmori Bartholomew D, Theander Thor G, Staalsoe Trine, Hviid Lars
Centre for Medical Parasitology at Department of Infectious Diseases and Department of Clinical Microbiology, Copenhagen University Hospital (Rigshospitalet), University of Copenhagen, Copenhagen, Denmark
Infect Immun. 2004 Jun;72(6):3531-5. doi: 10.1128/IAI.72.6.3531-3535.2004.
The slow acquisition of protection against Plasmodium falciparum malaria probably reflects the extensive diversity of important antigens. The variant surface antigens (VSA) that mediate parasite adhesion to a range of host molecules are regarded as important targets of acquired protective immunity, but their diversity makes them questionable vaccine candidates. We determined levels of VSA-specific immunoglobulin G (IgG) in human plasma collected at four geographically distant and epidemiologically distinct localities with specificity for VSA expressed by P. falciparum isolates from three African countries. Plasma levels of VSA-specific IgG recognizing individual parasite isolates depended on the transmission intensity at the site of plasma collection but were largely independent of the geographical origin of the parasites. The total repertoire of immunologically distinct VSA thus appears to be finite and geographically conserved, most likely due to functional constraints. Furthermore, plasma samples frequently had high IgG reactivity to VSA expressed by parasites isolated more than 10 years later, showing that the repertoire is also temporally stable. Parasites from patients with severe malaria expressed VSA (VSASM) that were better recognized by plasma IgG than VSA expressed by other parasites, but importantly, VSASM-type antigens also appeared to show substantial antigenic homogeneity. Our finding that the repertoire of immunologically distinct VSA in general, and in particular that of VSASM, is geographically and temporally conserved raises hopes for the feasibility of developing VSA-based vaccines specifically designed to accelerate naturally acquired immunity, thereby enhancing protection against severe and life-threatening P. falciparum malaria.
对恶性疟原虫疟疾的保护性免疫获得缓慢,这可能反映了重要抗原的广泛多样性。介导寄生虫与一系列宿主分子黏附的可变表面抗原(VSA)被视为获得性保护性免疫的重要靶点,但其多样性使其成为可疑的疫苗候选物。我们测定了在四个地理上相距遥远且流行病学特征不同的地点采集的人类血浆中VSA特异性免疫球蛋白G(IgG)的水平,这些血浆对来自三个非洲国家的恶性疟原虫分离株所表达的VSA具有特异性。识别单个寄生虫分离株的VSA特异性IgG的血浆水平取决于血浆采集地点的传播强度,但在很大程度上与寄生虫的地理来源无关。因此,免疫上不同的VSA的总库似乎是有限的且在地理上是保守的,这很可能是由于功能限制。此外,血浆样本对10多年后分离的寄生虫所表达的VSA通常具有较高的IgG反应性,这表明该库在时间上也是稳定的。重症疟疾患者的寄生虫所表达的VSA(VSASM)比其他寄生虫所表达的VSA更易被血浆IgG识别,但重要的是,VSASM型抗原似乎也表现出相当程度的抗原同质性。我们发现,一般而言,免疫上不同的VSA库,特别是VSASM库,在地理和时间上是保守的,这为开发专门设计用于加速自然获得性免疫的基于VSA的疫苗的可行性带来了希望,从而增强对严重且危及生命的恶性疟原虫疟疾的保护。