Acquisition of naturally acquired antibody response to Plasmodium falciparum erythrocyte membrane protein 1-DBLα and differential regulation of IgG subclasses in severe and uncomplicated malaria

Objectives:To explore whether individuals infected with Plasmodium falciparum (P.falciparum) develop antibodies directed against PfEMP1-DBLα,and to assess their IgG subclass distribution in severe and uncomplicated malaria.Methods:The anti-PfDBLα IgG and their IgG subclass distributions in plasma of severe (SM) and uncomplicated malaria (UCM) were assessed by enzyme-linked immunoabsorbent assay.The antibody profiles to P.falciparum blood stage antigens were evaluated.CD36 binding ability was determined by static receptor-binding assays.Rosette formation was performed by staining with acridine orange.Results:Significantly higher number of UCM (86.48％) than SM (57.78％) plasma contained total acquisition of specific IgG to P.falciparum antigens (P =0.000).Similar manners were seen in response to P.falciparum DBLα with significant difference (UCM,59.46％ vs SM,40.00％;P =0.014).Anti-PfDBLα-IgG1 and-IgG3 were the predominant subclasses.Similar percentage of UCM (31.82％) and SM (33.33％) plasma contained only IgG1,while 13.64％ of UCM and 27.78％ of SM plasma contained only IgG3.AntiPfTDBLα-IgG1 coexpressed with more than one subclass was noted (UCM,27.27％;SM,16.67％).Obviously,IgG1 coexpressed with IgG3 (9.09％) was observed in only UCM plasma.IgG1 was coexpressed with IgG2 in UCM (9.09％) and SM (11.11％) plasma,while IgG1 was coexpressed with IgG4 only in UCM plasma (4.55％).IgG subclasses to P.falciparum antigens were distributed in a similar manner.Only the levels of IgG1,but not IgG3 were significantly higher in UCM than in SM.Conclusions:These data suggest that individuals infected with P.falciparum can develop the anti-PfEMP1 antibodies with the major contribution of specific IgG subclasses.The balance and the levels of anti-PfDBLα IgG subclasses play a crucial role in antibody mediated protection against severe malaria.

Multiple mutations in katG and inhA identified in Thai isoniazid-resistant Mycobacterium tuberculosis isolates.

A total of 29 Thai multi-drug-resistant/isoniazid-resistant Mycobacterium tuberculosis isolates were analyzed for mutations in katG from codons 254 to 549, inhA promoter and inhA open reading frame by DNA sequencing and single strand conformation polymorphism. Twenty-five multi-drug resistant isolates exhibited single point mutations (17 isolates at Ser315Thr plus Arg463Leu, 1 at Thr308Pro plus Arg463Leu, 7 at either Ser315Thr or Arg463Leu) while the other 4 isoniazid-resistant isolates had single point mutation only at Arg463Leu. Seven of 25 multi-drug-resistant isolates [4 at C(-15)T, 1 at T(-8)C; 1 at C(-15)T plus Ser94Ala and 1 at Ile21Val] and 2 of 4 isoniazid-resistant isolates [1 at C(-15)T, 1 at C (-15)T plus Ile21Thr] had mutations in inhA promoter and open reading frame, while the other 20 isolates had no mutation at any position. No frame shift mutation was observed in any tested isolates. This is the first report of two mutations, Trp308Pro of katG and T (-8)C of inhA in Mycobacterium tuberculosis isolates.

IgG antibody profile to c-terminal region of Plasmodium vivax merozoite surface protein-1 in Thai individuals exposed to malaria.

Naturally acquired immune response to C-terminal region of Plasmodium vivax merozoite surface protein1 (PvMSP1) in 200 individuals with recent clinical episodes of malaria from malaria endemic areas along Thai-Myanmar border in the west and Thai-Cambodia border in the east of Thailand was evaluated by enzyme-linked immunosorbent assay (ELISA). The anti-PvMSP1-IgG antibody was observed in 110 individuals (55%). Among IgG responders, IgG1 coexpressed with IgG3 were the predominant subclasses. The levels of anti-PvMSP1 total IgG, IgG1 and IgG3 antibody response seem to be increased with age although no detectable significant correlation was found (r = 0.004, p = 0.484 for total IgG; r = 0.035, p = 0.386 for IgG1; r = -0.600, p = 0.142 for IgG2; r = 0.077, p = 0.227 for IgG3; r = 0.664, p = 0.051 for IgG4). However, the mean level of specific total IgG was highest in the age group of >40 years. These levels of either specific total IgG or each IgG isotype did not vary among individuals with different malaria episodes. A higher level of specific total IgG, IgG1 and IgG3 antibody response related with the lower of parasitemia density was observed although no significant correlation was found. Our data indicate that individuals exposed to vivax malaria in Thailand developed antibodies to the potential candidate vaccine antigen, PvMSP1 (C-terminal).

Detection of P. vivax antigens in malaria endemic populations of Nepal by ELISA using monoclonal antibodies raised against Thai isolates.

An indirect enzyme linked immunosorbent assay (ELISA) using monoclonal antibody (MAb) originated from the native Thai isolates of P. vivax (McPV1) and the polyclonal antibody (PAb) raised against Nepali isolates of P. vivax was developed for detection of P vivax antigens in red cell lysates. The assay was specific (100%) since it was positive only with P. vivax-infected erythrocytes and was negative when erythrocytes from 40 healthy individuals from malaria non-endemic areas and 40 P. falciparum infected erythrocytes were tested. When the assay was applied to 203 vivax blood samples already proven by microscopic examination collected from Dhanusha district of Nepal, and using the cut-off level of the mean optical density (OD) (0.144) of 40 healthy individuals who had been living in malaria-endemic areas (0.073) + 2 SD (0.016), the assay could detect 189/203 samples, indicating the sensitivity of the test was 93.1% with a detection limit of erythrocytes of 240 parasites/10(6) erythrocytes. In addition, the assay was negative when 40 blood samples with fever of unknown origin, collected from the same malaria-endemic areas, were tested. However, there was a significant correlation between OD values and parasitemia (r=0.649; p=0.018). The results indicate that MAb-PAb indirect ELISA using MAb raised against Thai isolates of P. vivax as the coating antibodies, and polyclonal antibodies raised against local Nepali isolates as the detecting antibody, could detect P. vivax antigens with high degrees of sensitivity and specificity. Furthermore, it seems that the McPV1 MAb raised against Thai isolates of P. vivax could recognize the antigens of Nepali isolates in a wide range of blood samples.

A survey of the Th2R and Th3R allelic variants in the circumsporozoite protein gene of P. falciparum parasites from western Thailand.

Allelic variation in the Plasmodium falciparum circumsporozoite protein (CS) gene has been determined by sequencing the immunodominant T-cell epitopes, Th2R and Th3R, from 95 isolates from two malaria-endemic areas in the west of Thailand. Comparison with a reference sequence revealed only non-synonymous point mutations in the two epitope regions. Point mutations were found outside these epitopes in a minority of samples, and all but four were also non-synonymous. A relatively high number of variants, 11 Th2R and 9 Th3R, were detected and comprised some that had not been previously observed. However, the Th2R*05 and the Th3R*01 allelic variants predominated, as they were found in more than 70% of the 101 sequences obtained.