Serum antibody response to Chlamydia trachomatis TroA and HtrA in women with tubal factor infertility.

Persistent genital chlamydial infection may lead to tubal factor infertility (TFI). Chlamydia trachomatis TroA and HtrA are proteins expressed during persistent chlamydial infection in vitro. We studied serum IgG antibody response against these proteins by EIA in women with TFI and in subfertile women without tubal pathology. Altogether, 22 of 258 subfertile women (8.5%) had TFI which was unilateral in 17 cases and bilateral in 5 cases. Overall, 55 (21.3%) of the 258 women had TroA and 39 (15.1%) had HtrA antibodies. Seropositivity to TroA and HtrA was more common among women with TFI than women with other causes for subfertility (45.5 vs. 19.1%, p = 0.004 for TroA; 36.4 vs. 13.1%, p = 0.004 for HtrA). Mean absorbance values and the prevalence of TroA and HtrA antibodies increased with increasing severity of TFI. On the basis of our results, TroA and HtrA serology has the potential to be further developed to a specific biomarker for C. trachomatis-related TFI.

Parechoviruses, a novel group of human picornaviruses.

Parechoviruses are a recently established group of human viral pathogens. At the time of their first isolation, parechoviruses were classified among the enterovirus genus in the picornavirus family, but based on their different biological properties they were separated into their own genus. The type member is human parechovirus 1 (HPEV1), which frequently infects humans, in particular small children. The parechovirus genus also includes HPEV2 and the Ljungan virus, which was recently isolated from rodents, is a candidate for the group. Seroepidemiological studies have shown that the prevalence of HPEV1 antibodies is surprisingly high, exceeding 95% in adult populations. According to present data, HPEV1 causes mainly gastrointestinal and respiratory infections; however, severe disease conditions, such as myocarditis and encephalitis, have also been reported. HPEV2 infections appear to be rare, and it is currently not known whether the Ljungan virus can infect humans.

Entry of human parechovirus 1.

Human parechovirus 1 (HPEV-1) is a prototype member of parechoviruses, a recently established picornavirus genus. Although there is preliminary evidence that HPEV-1 recognizes alpha(V) integrins as cellular receptors, our understanding of early events during HPEV-1 infection is still very limited. The aim of this study was to clarify the entry mechanisms of HPEV-1, including the attachment of the virus onto the host cell surface and subsequent internalization. In blocking experiments with monoclonal antibodies against different receptor candidates, antibodies against alpha(V) and beta(3) integrin subunits, in particular in combination, appeared to be the most efficient ones in preventing the HPEV-1 infection. To find out whether HPEV-1 uses clathrin-coated vesicles or other routes for the entry into the host cell, we carried out double-labeling experiments of virus-infected cells with anti-HPEV-1 antibodies and antibodies against known markers of the clathrin and the caveolin routes. At the early phase of infection (5 min postinfection [p.i.]) HPEV-1 colocalized with EEA1 (early endosomes), and later, after 30 min p.i., it colocalized with mannose-6-phosphate receptor (late endosomes), whereas no colocalization with caveolin-1 was observed. The data indicate that HPEV-1 utilizes the clathrin-dependent endocytic pathway for entry into the host cells. Interestingly, endocytosed HPEV-1 capsid proteins were observed in the endoplasmic reticulum and cis-Golgi network 30 to 60 min p.i. Depolymerization of microtubules with nocodazole inhibited translocation of the virus to the late endosomes but did not block HPEV-1 replication, suggesting that the RNA genome may be released early during the entry process.

Antigenic properties of human parechovirus 1.

Human parechoviruses 1 and 2 (HPEV1 and HPEV2, respectively), formerly known as echoviruses 22 and 23, have been assigned to a novel picornavirus genus on the basis of their distinct molecular and biological properties. To study the immunological characteristics of HPEV1 capsid proteins, antigenic analysis was carried out by a peptide scanning technique, which can be used to identify the immunogenic peptide sequences of a protein. Partially overlapping peptides, representing the capsid of HPEV1, were synthesized using a 12 aa window in a three residue shift and reactivity of rabbit and murine HPEV1 antisera against these peptides were tested. Using this method, an antigenic site in the VP0 polypeptide, recognized by both rabbit and murine antisera, was identified. The sequence of this region was conserved among HPEV1 clinical isolates obtained from Finland and the United States. Antiserum against this peptide region showed neutralizing activity against HPEV1 in cell culture. Because the C-terminal region of HPEV1 VP1 contains a functional RGD motif, the antigenicity of this region was also tested. By using the corresponding peptide antiserum, neutralization of HPEV1 was observed. Cross-neutralization between HPEV1 and coxsackievirus A9, an enterovirus with a similar RGD motif in VP1, was also detected.

Human parechoviruses--biology and clinical significance.

A new genus of the family Picornaviridae, Parechovirus, has recently been recognised on the basis of distinctive biological and molecular properties. In particular: parechoviruses exhibit characteristic effects on the host cell; cleavage of the capsid protein VP0, required for maturation of the virus particle in most other picornaviruses, does not occur; there is a unique extension, which is highly basic in character, to the N-terminus of the capsid protein VP3; and the 2A protein, in common with those of only two other known picornaviruses, is a homologue of a family of cellular proteins involved in the control of cell proliferation. The type member of the Parechovirus genus is a frequent human pathogen, formerly known as echovirus 22, which has been renamed human parechovirus 1. The genus also includes the closely related virus, human parechovirus 2 (formerly echovirus 23). Human parechoviruses generally cause mild, gastrointestinal or respiratory illness, but more serious consequences of infection, such as myocarditis and encephalitis have been reported. Most infections occur in young children. Ljungan virus, a newly identified virus of rodents, shares a number of molecular features with the human parechoviruses, raising important questions about the evolution of parechoviruses and their introduction into the human population.

Diagnosis and epidemiology of echovirus 22 infections.

To find out whether the appearance and pathogenicity of infections caused by echovirus 22 (EV22)--which has considerably different molecular characteristics from those of typical enteroviruses--exhibit extraordinary features, novel diagnostic approaches were applied. Staining of inoculated cell cultures with specific antibodies was followed by immunoperoxidase detection. Of fecal specimens from 140 children under 6 years of age, four were positive by the immunoperoxidase method. The nucleotide identity between these samples and additional EV22 isolates from Finland and the United States varied from 78% to 93% when studied by specific polymerase chain reaction, followed by sequence analysis of the amplicons. One-hundred ten single serum specimens collected from individuals in different age groups to find out the prevalence of EV22 antibodies were subjected to neutralization tests. Out of 21 neonates, 20 (95%) had EV22 antibodies, probably of maternal origin. Of 10 children aged 2-12 months, only two had neutralizing antibodies to EV22. The antibody levels increased rapidly by age, and among 30 adults tested, 29 (97%) were seropositive. A clear difference was observed with the occurrence of echovirus 30 (EV30) antibodies, which were less prevalent and appeared later in life. A review of previously published studies concerning the epidemiology of EV22 infections showed that gastroenteritis and respiratory infections are the most common symptoms observed in EV22 infections.