Lymphocyte proliferation and antibody responses to Plasmodium falciparum liver-stage antigen-1 in a highland area of Kenya with seasonal variation in malaria transmission.

Abstract

Abstract. Lymphocyte proliferation and antibody responses to five peptides corresponding to the N-and C-terminal non-repeat and central repeat regions of Plasmodium falciparum liver-stage antigen-1 (LSA-1) were examined in residents of a highland area of Kenya where malaria transmission is episodic and varies with rainfall. The frequency of lymphocyte proliferation responses (stimulation index > 2) by children (persons Յ 6 years old) and adults (persons Ն 18 years old) was similar and did not differ significantly across seasons. In contrast, the proportion of individuals with IgG antibodies to LSA-1 peptides was higher in the rainy than dry season, and the frequency of these responses was greater for adults than children (39.4% versus 18.7% during the period of high transmission; P ‫ס‬ 0.009). Antibodies to LSA-1 were primarily of the IgG1 and IgG3 subclasses, and these also varied with season (30.1% and 32.5% of individuals had IgG1 and IgG3 in the rainy season versus none and 10.9% in the dry season). There was no significant difference in the time to re-infection between groups of persons with or without IgG antibody or lymphocyte proliferation responses to LSA-1 peptides. These data indicate that age and transmission intensity independently affect IgG antibody responses to LSA-1 but do not influence lymphocyte proliferation in this highland area where malaria transmission is highly variable.

Antibodies to thePlasmodium falciparumAntigens Circumsporozoite Protein, Thrombospondin-Related Adhesive Protein, and Liver-Stage Antigen 1 Vary by Ages of Subjects and by Season in a Highland Area of Kenya

“…In the rainy season, the frequencies and levels of IgG antibodies to CSP and TRAP were similar in children and adults, but, as described previously, the frequencies and levels of IgG antibodies to LSA-1 were significantly lower in children than in adults (8). In the dry season, the frequencies and levels of antibodies to all three antigens were lower in children than in adults.…”

“…It was reported previously that the proportion of people with IgG, IgG1, and IgG3 subclass antibodies to LSA-1 decreased during a period of low transmission in a highland area of Kenya. However, antibodies to LSA-1 did not correlate with time to reinfection (8). In this paper, we describe IgG antibodies to the additional preerythrocytic antigens CSP and TRAP in these children and adults during the dry and rainy seasons and compare the frequencies and levels of these antibodies with those previously described for LSA-1 (8).…”

“…However, antibodies to LSA-1 did not correlate with time to reinfection (8). In this paper, we describe IgG antibodies to the additional preerythrocytic antigens CSP and TRAP in these children and adults during the dry and rainy seasons and compare the frequencies and levels of these antibodies with those previously described for LSA-1 (8). We also compare the time to reinfection with the presence of these antibodies in children and adults in whom preexisting blood-stage infections were cured with antimalarial chemotherapy.…”

“…The development of such antibodies is influenced strongly by age and the pattern of transmission (8,14). Most studies of antibodies to P. falciparum antigens have focused on a single antigen, have exclusively involved children or adults, and have been performed in areas where malaria transmission is stable and perennial.…”

Evidence That Invasion-Inhibitory Antibodies Specific for the 19-kDa Fragment of Merozoite Surface Protein-1 (MSP-119) Can Play a Protective Role against Blood-Stage Plasmodium falciparum Infection in Individuals in a Malaria Endemic Area of Africa

“…Malaria infection surveys conducted in Kabobo during periods of no or little rainfall have shown that the prevalence of blood-stage P. falciparum in symptom-free 5-to 10-year-old school children is 8.9%. The prevalence increased to 45.5% during a period of heavy rainfall (37,38).…”