Detection of bancroftian filariasis in human blood samples from Sorsogon province, the Philippines by polymerase chain reaction.

The polymerase chain reaction (PCR) was used for diagnosing Wuchereria bancrofti infection in a small village in the province of Sorsogon, the Philippines. Of 54 night-time blood samples collected, 4 (7.4%) were found to be microfilaremic as determined by combined direct blood film examination and membrane filtration of blood followed by blood film examination. However, utilization of the SspI PCR assay to detect repeated W. bancrofti DNA sequences in human blood doubled the number of microfilaremic individuals to 8 (13.0%). The results of this survey suggest that utilization of diagnostic tools based on microscopy could underestimate the true prevalence of W. bancrofti in the Philippines.

Paramyosin is a major target of the human IgA response against Schistosoma japonicum.

Human resistance and susceptibility to schistosomiasis is associated with age and specific antibody isotype responses against worm (SWAP) and egg (SEA) antigens. In a cross-sectional study of 176 individuals infected with Schistosoma japonicum in the Philippines, strikingly similar isotype response patterns against SWAP and SEA was observed when compared to other endemic areas. Interestingly, IgA titres to SWAP correlated with older age among S. japonicum-infected individuals (n = 176, P < 0.01), suggesting a role for this isotype in protective immunity. To identify the molecular targets of human IgA, 17 high-IgA/SWAP responders were identified from the said population. IgA antibodies from the majority (14/17) of these individuals recognized a band of 97 kDa (Sj97), comigrating in immunoblots with the myofibrillar protein paramyosin. The antigen was confirmed as paramyosin by expressed sequence tag (EST)-analysis of four clones obtained by screening an adult S. japonicum cDNA library with pooled IgA antisera and mouse antiparamyosin polyclonal antibodies. The identification of paramyosin as a major target of human IgA raises its potential as a vaccine candidate that targets mucosal immune responses. Since this antigen is exposed on the parasite surface only during the lung stages, we propose that human IgA contributes to parasite attrition during schistosome migration in the lungs.

Identification of the Schistosoma japonicum 22.6-kDa antigen as a major target of the human IgE response: similarity of IgE-binding epitopes to allergen peptides.

Human resistance to reinfection with Schistosoma mansoni and Schistosoma haematobium correlates with elevated IgE titers against worm antigens (soluble worm antigen preparation, SWAP). In S. mansoni infection, low levels of reinfection following chemotherapy are associated with the recognition of a cloned tegumental protein Sm22.6. Because of potential species-specific differences in resistance to schistosomes, we attempted to identify Schistosoma japonicum antigens recognized by human IgE. Following a survey of 176 infected individuals in Leyte, Philippines, we show that IgE antibodies from the majority of older, high-IgE/SWAP responders recognize antigens in the 22 (Sj22)-, 45-, 78- and 97-kDa range in SWAP. Limited IgE cross-reactivity between Sj22 and Sm22 was observed following a comparison of Filipino IgE responses to these antigens. The antigen was cloned from an adult S. japonicum lambda-ZAP cDNA library (Mindoro strain) by immunoscreening with pooled high-titer IgE antisera and a rabbit anti-Sj22 polyclonal antibody. The deduced amino acid sequence of the identified cDNA clone, MJ-1, showed significant homology to Sm22.6 (74%) and Sj22.6 (99%). Although the molecular sequence of Sj22.6 has already been reported, this is the first demonstration of its recognition by human IgE, thereby strengthening its potential as a vaccine candidate. Using an overlapping peptide approach, four IgE-binding epitopes were identified in Sj22.6, two of which exhibited similarities to known IgE-binding epitopes from codfish (Gad c 1) and beta-lactoglobulin-related allergens. These findings suggest that allergy and protective immunity to helminth infection may be linked by the structural similarities of epitopes recognized by human IgE.

Molecular epidemiology of HIV-1 infection in the Philippines, 1985 to 1997: transmission of subtypes B and E and potential emergence of subtypes C and F.

The molecular epidemiology of HIV-1 infection in the Philippines from 1985 to 1997 was investigated following subtyping of 54 (33 women, 21 men) prospectively collected clinical specimens using the heteroduplex mobility assay (HMA). In contrast with other Asian countries, subtype B accounted for most (70%) of the infections in the population studied, among female commercial sex workers (CSWs, 18 of 28), overseas contract workers (OCWs, 7 of 10), and men who have sex with men (MSM, 8 of 10). However, although viral specimens from HIV-seropositive persons diagnosed before 1993 (n = 16) were all of subtype B, diagnoses in more recent years (1993-present, n = 38) indicate the existence of subtypes E (29%), F (8%), and C (5%) in the population. Since its estimated introduction in the early 1990s, subtype E has accounted for 60% of the infections among female CSWs diagnosed after 1992 (n = 15). This genotype distribution shift occurred in parallel with a shift in transmission focus from the U.S. military bases to the the Philippine national capital region. So far, both events appear to have had no significant effect on the stability of HIV-1 transmission in the country. The recent identification of non-B subtypes in the Philippines may present novel insights on the dynamics of HIV-1 transmission in a high-risk but low-HIV prevalence setting in Asia.

Identification and molecular cloning of a 67-kilodalton protein in Schistosoma japonicum homologous to a family of actin-binding proteins.

A monoclonal antibody to Schistosoma japonicum which conferred significant protection against cercarial challenge in mice was produced. The predicted translation product of the cDNA corresponding to the antigen recognized by this antibody was homologous to a newly identified family of actin-binding proteins. The expressed protein bound polymerized actin and was recognized by serum from patients infected with S. japonicum.

Paramyosin: a candidate vaccine antigen against Schistosoma japonicum.

Paramyosin, a 97 kDa myofibrillar protein, is a candidate vaccine antigen for prevention of infection with the human parasite Schistosoma mansoni. To determine if paramyosin would also induce protection against Schistosoma japonicum, paramyosin was biochemically purified from S. japonicum adult worms. SDS-PAGE demonstrated a single protein with a molecular weight of 97 kDa. In four separate experiments, vaccination of mice with S. japonicum paramyosin without adjuvant induced significant resistance (62%-86%, P < 0.001) against cercarial challenge as compared to controls. These data suggest that S. japonicum paramyosin may represent a candidate vaccine for immunization against schistosomiasis japonica.