Predictive markers for development of strongyloidiasis in patients infected with both Strongyloides stercoralis and HTLV-1

Abstract

Severe strongyloidiasis has often been reported to occur in some patients infected with both Strongyloides stercoralis (S. stercoralis) and human T-cell leukaemia virus type 1 (HTLV-1); however, there are few useful predictive markers for the risk of development of strongyloidiasis in these patients. To search for such predictive markers, we examined peripheral blood and stool samples of individuals infected with both S. stercoralis and HTLV-1 in Okinawa, Japan, an area in which both of these are endemic. The HTLV-1 proviral load and antibody titre were examined in relation to the S. stercoralis load as measured by the direct faecal smear method in patients infected with both S. stercoralis and HTLV-1. The Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA) antibody titre was also measured in these patients in order to examine the relationship between host immunity and HTLV-1 proviral load or antibody titre. The direct faecal smear-positive group showed both a higher HTLV-1 proviral load and HTLV-1 antibody titre than the -negative group (P < 0.05). In contrast, inverse correlations of these parameters with the EBNA antibody titre were observed, especially for proviral load (rho = -0.387, P < 0.05). These results suggest that HTLV-1 proviral load and antibody titre influence the S. stercoralis load via disturbance of the host immunity, and that proviral load would be an especially useful predictive marker of the risk of development of strongyloidiasis in patients infected with both S. stercoralis and HTLV-1.

Fig. 1

HTLV-1 proviral load and antibody titre were compared between the direct faecal smear-negative (○) (n = 12) and –positive (•) (n = 19) groups. (a) HTLV-1 proviral load in the direct faecal smear-positive group was higher than that in the -negative group (direct faecal smear-negative group, median 3·5%, range 9·7%; direct faecal smear-positive group, median 11·0%, range 17·0%). (b) HTLV-1 antibody titre in the direct faecal smear-positive group was higher than that in the -negative group (direct faecal smear-negative group, median 4,096, range 15,360; direct faecal smear-positive group, median 8,192, range 28,672). (*P < 0·01, **P < 0·05, by Mann–Whitney U-test)

Fig. 2

Correlation between HTLV-1 proviral load and antibody titre in patients infected with both S. stercoralis and HTLV-1. The direct faecal smear-positive group (•) had both higher HTLV-1 proviral load and antibody titre than the -negative group (○). A correlation between HTLV-1 proviral load and antibody titre was observed in these patients infected with both S. stercoralis and HTLV-1 (ρ = +0·566, P < 0·01, by Spearman's rank correlation).

Fig. 3

Relationship between EBNA antibody titre and HTLV-1 proviral load or antibody titre. ○ direct faecal smear-negative patients; • direct faecal smear-positive patients. (a) An inverse correlation was observed between the HTLV-1 proviral load and EBNA antibody titre (ρ = −0·387, P < 0·05, by Spearman's rank correlation). The direct faecal smear-positive group had a higher HTLV-1 proviral load and a lower EBNA antibody titre than the -negative group. (b) An inverse correlation tended to be present between the HTLV-1 antibody titre and EBNA antibody titre, however, it was not significant (ρ = −0·340, P < 0·1, by Spearman's rank correlation).