Role of human Pegivirus infections in whole Plasmodium falciparum sporozoite vaccination and controlled human malaria infection in African volunteers

BACKGROUND

Diverse vaccination outcomes and protection levels among different populations pose a serious challenge to the development of an effective malaria vaccine. Co-infections are among many factors associated with immune dysfunction and sub-optimal vaccination outcomes. Chronic, asymptomatic viral infections can contribute to the modulation of vaccine efficacy through various mechanisms. Human Pegivirus-1 (HPgV-1) persists in immune cells thereby potentially modulating immune responses. We investigated whether Pegivirus infection influences vaccine-induced responses and protection in African volunteers undergoing whole P. falciparum sporozoites-based malaria vaccination and controlled human malaria infections (CHMI).

METHODS

HPgV-1 prevalence was quantified by RT-qPCR in plasma samples of 96 individuals before, post vaccination with PfSPZ Vaccine and after CHMI in cohorts from Tanzania and Equatorial Guinea. The impact of HPgV-1 infection was evaluated on (1) systemic cytokine and chemokine levels measured by Luminex, (2) PfCSP-specific antibody titers quantified by ELISA, (3) asexual blood-stage parasitemia pre-patent periods and parasite multiplication rates, (4) HPgV-1 RNA levels upon asexual blood-stage parasitemia induced by CHMI.

RESULTS

The prevalence of HPgV-1 was 29.2% (28/96) and sequence analysis of the 5' UTR and E2 regions revealed the predominance of genotypes 1, 2 and 5. HPgV-1 infection was associated with elevated systemic levels of IL-2 and IL-17A. Comparable vaccine-induced anti-PfCSP antibody titers, asexual blood-stage multiplication rates and pre-patent periods were observed in HPgV-1 positive and negative individuals. However, a tendency for higher protection levels was detected in the HPgV-1 positive group (62.5%) compared to the negative one (51.6%) following CHMI. HPgV-1 viremia levels were not significantly altered after CHMI.

CONCLUSIONS

HPgV-1 infection did not alter PfSPZ Vaccine elicited levels of PfCSP-specific antibody responses and parasite multiplication rates. Ongoing HPgV-1 infection appears to improve to some degree protection against CHMI in PfSPZ-vaccinated individuals. This is likely through modulation of immune system activation and systemic cytokines as higher levels of IL-2 and IL17A were observed in HPgV-1 infected individuals. CHMI is safe and well tolerated in HPgV-1 infected individuals. Identification of cell types and mechanisms of both silent and productive infection in individuals will help to unravel the biology of this widely present but largely under-researched virus.

Chronic Human Pegivirus 2 without Hepatitis C Virus Co-infection

Most human pegivirus 2 (HPgV-2) infections are associated with past or current hepatitis C virus (HCV) infection. HPgV-2 is thought to be a bloodborne virus: higher prevalence of active infection has been found in populations with a history of parenteral exposure to viruses. We evaluated longitudinally collected blood samples obtained from injection drug users (IDUs) for active and resolved HPgV-2 infections using a combination of HPgV-2–specific molecular and serologic tests. We found evidence of HPgV-2 infection in 11.2% (22/197) of past or current HCV-infected IDUs, compared with 1.9% (4/205) of an HCV-negative IDU population. Testing of available longitudinal blood samples from HPgV-2–positive participants identified 5 with chronic infection (>6 months viremia in >3 timepoints); 2 were identified among the HCV-positive IDUs and 3 among the HCV-negative IDUs. Our findings indicate that HPgV-2 can establish chronic infection and replicate in the absence of HCV.

Beneficial effect of GB virus C co-infection in Human Immunodeficiency Virus type 1-infected individuals

Several reports have documented a better prognosis for HIV-1-infected patients co-infected with GBV-C, while other reports have contradicted such findings with the result that this issue remains controversial. We attempted to clarify the complicated status of the effect of GBV-C co-infection on HIV-1-infected patients. GBV-C RNA was detected in 37 samples in 182 HIV-1-infected patients (20.3%) using RT/nested PCR. Of these, 3 were determined to be GBV-C genotype 1, 12 were genotype 2, and the remaining 22 were genotype 3. The GBV-C viral load quantified by real-time PCR ranged from 7.8x10(3) to 3.3x10(6) copies/ml. Weakly negative correlation was observed between GBV-C viral load and HIV-1 viral load in 19 HAART-naïve patients, indicating that a higher GBV-C viral load is associated with a greater suppression of HIV-1 replication. A previously published in vitro study suggested that GBV-C infection would induce up-regulation of RANTES, leading to suppression of HIV-1 replication. However, in our present study, the blood RANTES level was significantly lower in the GBV-C co-infected group than in the uninfected group (190-9,959 vs. 264-31,038 pg/ml, P=0.004). Our results suggested that a suppression of HIV-1 replication by GBV-C co-infection is not mediated by up-regulated RANTES, and thus call for another as yet unknown factor.

Study on the blood-borne virus co-infection and T lymphocyte subset among intravenous drug users

AIM: To investigate the features of various blood-borne virus infections and co-infection in intravenous drug users (IDUs), and to examine the correlation of T lymphocyte subsets with virus co-infection.

METHODS: Four hundred and six IDUs without any clinical manifestation of hepatitis and 102 healthy persons were enrolled in this study. HBV-DNA and HCV-RNA were detected by fluorescence quantitative PCR. HBsAg, HBeAg, anti-HBc, anti-HCV, HDV-Ag, anti-HGV, anti-HIV, and HCMV-IgM were assayed by enzyme-linked immunosorbent assay (ELISA) and immunochromatographic tests. The levels of Th1 and Th2 cytokines were measured by ELISA and radioactive immune assay (RIA). The T lymphocyte subpopulation was detected by using fluorescence immunoassay. The similar indices taken from the healthy persons served as controls.

RESULTS: The viral infection rate among IDUs was 36.45% for HBV, 69.7% for HCV, 47.3% for HIV, 2.22% for HDV, 1.97% for HGV, and 3.45% for HCMV. The co-infection rate of blood-borne virus was detected in 255 of 406 (62.81%) IDUs. More than 80% (161/192) of subjects infected with HIV were co-infected with the other viruses, such as HBV, HCV. In contrast, among the controls, the infection rate was 17.65% for HBV and 0% for the other viruses. Our investigation showed that there was a profound decrease in the proportion of CD4/CD8 and the percentage of CD3 and CD4, but not in the percentage of CD8. The levels of PHA-induced cytokines (IFN-γ and IL-4) and serum IL-2 were obviously decreased in IDUs. On the other hand, the level of serum IL-4 was increased. The level of IFN-γ and the percentage of CD4 were continuously decreased when the IDUs were infected with HIV or HIV co-infection. IDUs with HIV and HBV co-infection was 15.1% (29/192). Of those 29 IDU with HIV and HBV co-infection, 51.72% (15/29) and 37.93% (11/29) were HBV-DNA-positive and HBeAg-positive, respectively. But, among IDUs without HIV infection, only 1.68% (2/119) of cases were HBV-DNA-positive.

CONCLUSION: HCV, HBV and HIV infections are common in this population of IDU, leading to a high incidence of impaired Th1 cytokine levels and CD4 lymphocyte. IDUs with HIV and HBV/HCV co-infection have lower expression of Th1 cytokine with enhancement of the Th2 response. HIV may be causing HBV replication by decreasing Th1 function.

[Registration rate of IgG antibodies produced against antigens of virus hepatitis G in patients with HIV infection]

201 HIV infected and 200 non HIV infected patients have been observed to detect antibodies to virus hepatitis G. It was established that IgG antibodies are detected more often in HIV infected than in non-HIV-infected persons (24,9% of cases). The highest number of hepatitis G-infected patients is observed among HIV patients at before-HIV clinically apparent stage and HIV clinical stage as well as in patients infected by HIV virus during parenteral infusion.

High prevalence of HGV coinfection with HBV or HCV among northeastern Thai blood donors

Hepatitis G viral (HGV) infection among northeastern Thai blood donors was determined by the nested RT-PCR technique. HGV RNA was amplified by the degenerated helicase primers for a product of the expected size of 83 base pairs were used in this study. Serum samples from 322 of three different categories of northeastern Thai blood donors were included in this study. There were 104 HBsAg and Anti-HCV seronegative blood donors (control group), 100 samples of HBs Ag seropositive blood donors (HBV infected group) and 118 serum samples from anti-HCV seropositive blood donors (HCV infected group). The results demonstrated that HGV RNA was not detected in the control group but was found in 10 individuals (10%) in the HBV infected group and 13 (11%) in the anti-HCV positive blood donors. The prevalences of HGV in both seropositive groups were significantly different from the control group (p = 0.001). HGV co-infection is highly prevalent among northeastern Thai blood donors who are infected with HBV or HCV. The results also reveal that blood donors seronegative for HCV and HBV are a low risk group for HGV infection.

Antigenicity of chimeric and cyclic synthetic peptides based on nonstructural proteins of GBV-C/HGV

In this work, new putative epitopes located in nonstructural proteins of GBV-C/HGV were synthesized using solid-phase chemistry for their use in immunoassays. The antigens were obtained in linear, chimeric and cyclic forms with the main aim of improving the sensitivity of the enzyme immunoassays. Our results showed, on one hand, that the combination of different antigens seems to be necessary to ensure good sensitivity and more specificity and, on the other hand, that cyclic compounds show higher ability to recognize anti-GBV-C/HGV antibodies than its parent peptide. Furthermore, CD and FTIR have been used in conjunction to characterize the conformational changes therein with synthetic constructs that could explain their different antigenicity.

[Serum level of soluble forms of membranous antigens of immune system cells in carriers of virus hepatitis G markers]

The levels of soluble CD38 (sCD38), CD50 (sCD50), and CD95 (sCD95) antigens and HLA class I (sHLA-I) were determined in the serum samples from persons infected with hepatitis G virus (HGV). HGV monoinfection was accompanied by a rise in the serum content of sCD38, sCD50, and sCD95 antigens. The serum presence of HGV RNA and anti-E2 HGV antibodies was characterized by the normal content of sCD38 and sCD95 while the level of sCD50 was elevated and the serum content of sHLA-I was decreased. If the serum contained only anti-E2 HGV antibodies, the level of sCD50 remained increased 4-fold. It is suggested that the higher adhesion-inhibiting level of sCD50 is a reason of a weak immune response to HGV and hence of a long HGV persistence in the body.

GB virus C/hepatitis G virus infection in Indian blood donors and high-risk groups

The hepatitis G virus (HGV) or GB virus C (GBV-C) was discovered in 1995 as a putative agent of post-transfusion, non-A-E hepatitis. The present study was carried out with the aim to find the prevalence of this virus among various subject groups at risk for parenteral transmission as well as in healthy control subjects both individually and along with other parenterally transmitted hepatitis viruses. Of the 402 subjects tested, 6.22% were positive for the HBsAg surface antigen, 7.21% were positive for HCV RNA while only 2.24% were seen to be carriers of the HGV/GBV-C RNA. All the HGV/GBV-C positive cases were either multi-transfused thalassaemic subjects or hemodialysis patients. None of the healthy control subjects showed presence of the virus. Seven of the HGV/GBV-C positive subjects showed co-infection with one or more additional virological markers. Also, of the 9 HGV/GBV-C positive subjects, 5 showed elevated ALT levels while 4 showed elevated alkaline phosphatase levels. Overall our findings seem to indicate that HGV infections generally are asymptomatic, transient and self-limiting and the virus does not seem to show a very high prevalence among the Indian population.

[GB virus C: lack of association with transaminases levels, CD4 and HIV viral load in aids patients]

OBJECTIVE

To study the prevalence of GBV-C-RNA in sera of HIV-infected patients and determine whether differences in immunological condition and hepatic disease exist between GBV-C positive and negative patients.

METHODS

The presence of GBV-C-RNA was determined in sera of 222 HIV-positive patients by semi-automated RT-PCR. A comparison of GBV-C-RNA positive and negative patients was made by studying a series of clinical and analytical parameters. This same comparison was made in particular between those coinfected with HCV and GBV-C and those who only presented GBV-C.

RESULTS

Prevalence of GBV-C-RNA was 28.8%. The most frequent hepatotropic virus was HCV, appearing in 71.6% of cases. Coinfection with HCV and HGV was present in 17% and 8.6% only had GBV-C. Patients positive for GBV-C-RNA showed clinical and analytical characteristics similar to those found in GBV-C-RNA negative patients. Among the HCV-GBV-C coinfected and those presenting HGV as the only virus it was observed that the coinfected group presented alterations in transaminases and predominance of parenteral transmission as a risk factor for HIV, whereas the GBV-C group presented normal transaminases and predominance of sexual transmission. No differences were perceived in mean CD4 and HIV-RNA values in both groups.

CONCLUSIONS

Being positive for GBV-C in HIV-positive patients does not influence the presence of hepatic disease that in these patients is frequently accompanied by coinfection with other hepatotropic viruses. Moreover, it does not seem to influence the viremia of the HIV nor the CD4 cell counts.

Molecular investigation of GB virus C RNA in hemodialysis and thalassemics patients from Brazil

The GB virus C (GBV-C)/hepatitis G virus (HGV) is a member of the Flaviviridae family. Based on the clinical and epidemiological profiles, this virus could be acquired mainly by parenteral transmission through contaminated blood. We therefore investigated the presence of GBV-C/HGV and its relation with the other blood borne viruses as hepatitis B and C viruses (HBV, HCV) in hemodialysis and thalassemic individuals and blood donors from Ribeirão Preto-Brazil. Detection of blood borne virus markers including HBV surface antigen (HbsAg), HBV core antibody (anti-Hbc) and HCV antibody was carried out. HIV-1, HIV-2, HTLV-1 and HTLV-2 were also investigated. GBV-C/HGV RNA was detected by reverse transcriptase and polymerase chain reaction (RT-PCR). Ninety-four serum samples from patients with chronic renal failure were analyzed. GBV-C/HGV RNA was identified in 12 (12.8%) patients, anti-HCV antibodies in 28 (29.8%), anti-Hbc in 9 (9.6%), anti-HIV in 1 (1%), HBsAg in 33 (35.1%), and HBsAg/ anti-HBc was observed in 2 (2.1%) patients. Thirty-six (38.3%) samples were non-reactive. Seven of the 12 GBV-C/HGV RNA infected samples were co-infected with other viruses: 3 (25%) with HBsAg, 2 (16.7%) with anti-HCV and 2 (16.7%) with anti-HBc/anti-HCV/HBsAg. Among the 42 thalassemic patients GBV-C/HGV RNA was detected in 6/42 patients (14.2 %). Three patients presented GBV-C/HGV, with other blood borne markers. We also detected GBV-C/ HGV in 6/50 (12%) blood donors. In these GBV-C/HGV positive thalassemics patients, 50% (3/6) were young individuals (lesser 15 years old) and 67% (4/6) were female patients. The presence of GBV-C RNA in the absence of hepatitis B and C infection in the young patients and healthy donors could be indicate that this virus is capable of independent transmission and does not contribute to liver disease.

Genomic and antigenomic chains of hepatitis C virus and hepatitis G virus in serum, liver and peripheral blood mononuclear cells

OBJECTIVE

To determine HCV and HGV replication sites in patients with chronic hepatitis C and to study interaction between these two viruses.

PATIENTS

HGV RNA was studied in 272 patients with chronic hepatitis C. Of these, 35 were positive (group I). Twenty-three patients with chronic hepatitis C not co-infected with HGV were selected (group II).

RESULTS

Genomic and antigenomic chains of HCV were studied in both groups and those of HGV in group I in serum samples, peripheral blood mononuclear cells and liver tissue. In group I genomic chains of HCV and HGV were observed in 86 and 100%, respectively (ns), in serum samples (n = 35), and antigenomic chains in 17 and 23%, respectively (ns). In mononuclear cell samples (n = 15) 100% presented the genomic chain of HCV and 60% presented that of HGV (p < 0.05). Antigenomic chains were detected in 13 and 33%, respectively (ns). In liver tissue (n = 25) genomic chains were observed in 100 and 12%, respectively (p < 0.001); the antigenomic chain of HCV was detected in 76% while that of HGV was not present (p < 0.001). In group II genomic chains of HCV were found to be present in a very high percentage in all samples, while antigenomic chains appeared in 13% of serum and mononuclear cell samples and 89% of liver samples.

CONCLUSIONS

HCV and HGV have different sites of replication: whereas HCV replicates mainly in the liver, HGV is not hepatotropic. Mononuclear cells could represent a replication site for HGV but they are less important for HCV. Lastly, HGV does not modify the viral replication of HCV.

The prevalence of TT virus and GB virus C/hepatitis G virus infection in individuals with raised liver enzymes but without HBV or HCV infection in Taiwan

The prevalence of TT virus (TTV) and GB virus-C/hepatitis G virus (GBV-C/HGV) infection and the association with raised liver function tests in 546 Taiwanese with negative HBsAg, anti-HCV and HCV RNA was elucidated. They were tested for serum alanine aminotransferase (ALT), GBV-C/HGV RNA, anti-envelope protein 2 antibody (anti-E2) and TTV DNA. Direct sequencing and phylogenetic analyses were performed on 58 isolates for TTV genotype determination. The prevalence of TTV DNA, GBV-C/HGV RNA, anti-E2 and over all GBV-C/HGV exposure was 24.9, 3.4, 8.2 and 11.1%, respectively. Using uni- and multi-variate analyses, male gender and TTV viremia were associated significantly with raised ALT values. Sixty-nine percent of TTV isolates were deduced to be TTV genotype 1 and they had significantly lower mean age than genotype non-1 isolates. In the population, raised ALT may be related to male gender and be attributable to TTV infection but not to GBV-C/HGV among individuals with no evidence of current HBV and HCV infection. TTV genotype 1 is the most prevalent genotype and associated with younger age.

[The effects of hepatitis G virus infection on clinical features and liver pathologic lesions of chronic hepatitis C]

OBJECTIVE

To explore the clinical and pathological effect of hepatitis G virus infection on chronic hepatitis C.

METHODS

Detecting HGV-RNA by reverse transcription-polymerase chain reaction from serum samples of 53 chronic hepatitis C through patients as diagnosed by liver biopsy. The clinical and pathologic features of the patients with positive HGV-RNA were compared with those of patients with negative HGV-RNA.

RESULTS

The results showed that 15 patients (28.3%) were positive for serum HGV-RNA and there were no significant differences in clinical manifestations, biochemical indexes, HCV-RNA positive rates and the liver pathologic lesions between these HGY RNA positive and negative groups (P > 0.05).

CONCLUSIONS

These data indicate that HGV coinfection does not affect the liver lesions and HCV replication of chronic hepatitis C.

[Dynamic observation of serological and histological changes of Chinese rhesus monkeys infected by hepatitis G virus]

OBJECTIVE

To study the genesis, development and pathogenesis of hepatitis G.

METHODS

The Chinese Rhesus monkeys were intravenously injected with the serum from a hepatitis G patient only with HGV RNA positive. The dynamic changes of serum and liver tissues of the animals were observed before and after infection. Also the immunohistochemical study were done with monocolonal antibody against NS5 gene antigen of HGV. One male monkey was dissected and the internal organs were taken for histological examination 18 months after infection.

RESULTS

Serum ALT and AST became increasing 30 days after infection and showed abnormal continuously for 9 months. Spotty and focal necrosis and piecemeal necrosis were found in liver tissue from 2 to 18 months after infection. Positive staining of HGV antigen was present in cytoplasm of liver cells by immunohistochemistry. Histological observation showed that the internal organs were normal except the liver tissue in which the damages were similar with that in hepatitis.

CONCLUSION

The successful infection of Chinese Rhesus monkey by serum from hepatitis G patient can used as a good animal model for the study of hepatitis G.

Studies on an outbreak of Wesselsbron virus in the Free State Province, South Africa

In early March 1996, Wesselsbron (WSL) virus caused mortality among lambs on a farm near Bultfontein in the northern Free State Province, South Africa. Mosquito collections were therefore undertaken from 27 March to 1 April to collect floodwater Aedes mosquitoes for attempts at virus isolation. In all, 4,732 floodwater Aedes were tested; 5 WSL, 1 Middelburg (MID), and 5 unidentified viruses were isolated from 3,052 Aedes (Neomelaniconion) mcintoshi/luridus (minimum infection rate [MIR] for WSL = 1.63) and 5 WSL, 1 MID, and 3 unidentified viruses from 1,478 Aedes (Ochlerotatus) juppi/caballus (MIR for WSL = 3.38). One of the authors developed WSL fever on 3 April; WSL virus was isolated from his serum, and he developed a titer of 1:640 in the hemagglutination inhibition (HI) test and became IgM positive against WSL virus. Among a sample of 44 sheep bled on 4-5 September, 59% were antibody positive by the HI test against WSL and 48% against MID viruses. Mosquito collecting was restricted to 2 discrete, shallow, grassy depressions that were the main floodwater Aedes breeding sites on the farm so they will be investigated further as possible foci of transovarial transmission of WSL and MID viruses.

Genomic organization of GB viruses A and B: two new members of the Flaviviridae associated with GB agent hepatitis

The genomes of two positive-strand RNA viruses have recently been cloned from the serum of a GB agent-infected tamarin by using representational difference analysis. The two agent, GB viruses A and B (GBV-A and GBV-B, respectively), have genomes of 9,493 and 9,143 nucleotides, respectively, and single large open reading frames that encode potential polyprotein precursors of 2,972 and 2,864 amino acids, respectively. The genomes of these agents are organized much like those of other pestiviruses and flaviviruses, with genes predicted to encode structural and nonstructural proteins located at the 5' and 3' ends, respectively. Amino acid sequence alignments and subsequent phylogenetic analysis of the RNA-dependent RNA polymerases (RdRps) of GBV-A and GBV-B show that they possess conserved sequence motifs associated with supergroup II RNA polymerases of positive-strand RNA viruses. On the basis of similar analyses, the GBV-A- and GBV-B-encoded helicases show significant identity with the supergroup II helicases of positive-strand RNA viruses. Within the supergroup II RNA polymerases and helicases, GBV-A and GBV-B are most closely related to the hepatitis C virus group. Across their entire open reading frames, the GB agents exhibit 27% amino sequence identity to each other, approximately 28% identity to hepatitis C virus type 1, and approximately 20% identity to either bovine viral diarrhea virus or yellow fever virus. The degree of sequence divergence between GBV-A and GBV-B and other Flaviviridae members demonstrates that the GB agents are representatives of two new genera within the Flaviviridae family.