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Background: The 2 strains of Epstein-Barr virus (EBV), EBV type 1 (EBV-1) and EBV-2, differ in latency genes, suggesting that they use distinct mechanisms to establish latency. We previously reported that EBV-2 infects T cells in vitro. In this study, we tested the possibility that EBV-2 infects T cells in vivo.Methods: Purified T-cell fractions isolated from children positive for EBV-1 or EBV-2 and their mothers were examined for the presence of EBV and for EBV type.Results: We detected EBV-2 in all T-cell samples obtained from EBV-2-infected children at 12 months of age, with some children retaining EBV-2-positive T cells through 24 months of age, suggesting that EBV-2 persists in T cells. We were unable to detect EBV-2 in T-cell samples from mothers but could detect EBV-2 in samples of their breast milk and saliva.Conclusions: These data suggest that EBV-2 uses T cells as an additional latency reservoir but that, over time, the frequency of infected T cells may drop below detectable levels. Alternatively, EBV-2 may establish a prolonged transient infection in the T-cell compartment. Collectively, these novel findings demonstrate that EBV-2 infects T cells in vivo and suggest EBV-2 may use the T-cell compartment to establish latency. [ABSTRACT FROM AUTHOR]

Rift Valley fever (RVF) in ungulates and humans is caused by a mosquito-borne RVF phlebovirus (RVFV). Live attenuated vaccines are used in livestock (sheep and cattle) to control RVF in endemic regions during outbreaks. The ability of two or more different RVFV strains to reassort when co-infecting a host cell is a significant veterinary and public health concern due to the potential emergence of newly reassorted viruses, since reassortment of RVFVs has been documented in nature and in experimental infection studies. Due to the very limited information regarding the frequency and dynamics of RVFV reassortment, we evaluated the efficiency of RVFV reassortment in sheep, a natural host for this zoonotic pathogen. Co-infection experiments were performed, first in vitro in sheep-derived cells, and subsequently in vivo in sheep. Two RVFV co-infection groups were evaluated: group I consisted of co-infection with two wild-type (WT) RVFV strains, Kenya 128B-15 (Ken06) and Saudi Arabia SA01-1322 (SA01), while group II consisted of co-infection with the live attenuated virus (LAV) vaccine strain MP-12 and a WT strain, Ken06. In the in vitro experiments, the virus supernatants were collected 24 h post-infection. In the in vivo experiments, clinical signs were monitored, and blood and tissues were collected at various time points up to nine days post-challenge for analyses. Cell culture supernatants and samples from sheep were processed, and plaque-isolated viruses were genotyped to determine reassortment frequency. Our results show that RVFV reassortment is more efficient in co-infected sheep-derived cells compared to co-infected sheep. In vitro, the reassortment frequencies reached 37.9% for the group I co-infected cells and 25.4% for the group II co-infected cells. In contrast, we detected just 1.7% reassortant viruses from group I sheep co-infected with the two WT strains, while no reassortants were detected from group II sheep co-infected with the WT and LAV strains. The results indicate that RVFV reassortment occurs at a lower frequency in vivo in sheep when compared to in vitro conditions in sheep-derived cells. Further studies are needed to better understand the implications of RVFV reassortment in relation to virulence and transmission dynamics in the host and the vector. The knowledge learned from these studies on reassortment is important for understanding the dynamics of RVFV evolution. [ABSTRACT FROM AUTHOR]

Background: CCR5 antagonists have clinically been approved for prevention or treatment of HIV/AIDS. Countries in Sub-Saharan Africa with the highest burden of HIV/AIDS are due to adopt these regimens. However, HIV-1 can also use CXCR4 as a co-receptor. There is hence an urgent need to map out cellular tropism of a country’s circulating HIV strains to guide the impending use of CCR5 antagonists. Objectives: To determine HIV-1 coreceptor usage among patients attending a comprehensive care centre in Nairobi, Kenya. Methods: Blood samples were obtained from HIV infected patients attending the comprehensive care centre, Kenyatta National Hospital in years 2008 and 2009. The samples were separated into plasma and peripheral blood mononuclear cells (PBMCs). Proviral DNA was extracted from PBMCs and Polymerase Chain reaction (PCR) done to amplify the HIV env fragment spanning the C2-V3 region. The resultant fragment was directly sequenced on an automated sequencer (ABI, 3100). Co-receptor prediction of the env sequences was done using Geno2pheno [co-receptor], and phylogenetic relationships determined using CLUSTALW and Neighbor Joining method. Results: A total of 67 samples (46 treatment experienced and 21 treatment naive) were successfully amplified and sequenced. Forty nine (73%) sequences showed a prediction for R5 tropism while 18(27%) were X4 tropic. Phylogenetic analysis showed that 46(69%) were subtype A, 11(16%) subtype C, and 10(15%) subtype D. No statistical significant associations were observed between cell tropism and CD4+ status, patient gender, age, or treatment option. There was a tendency for more X4 tropic strains being in the treatment experienced group than the naive group: Of 46 treatment experiencing participants, 14(30%) harboured X4, compared with 4(19%) of 21 of the treatment-naïve participants, the association is however not statistically significant (p = 0.31). However, a strong association was observed between subtype D and CXCR4 co- receptor usage (p = 0.015) with 6(60%) of the 10 subtype D being X4 tropic and 4(40%) R5 tropic. Conclusion: HIV-1 R5 tropic strains were the most prevalent in the study population and HIV infected patients in Kenya may benefit from CCR5 antagonists. However, there is need for caution where subtype D infection is suspected or where antiretroviral salvage therapy is indicated. [ABSTRACT FROM AUTHOR]

The African citrus triozid (ACT), Trioza erytreae (Del Guercio), is the primary vector of Candidatus Liberibacter africanus (CLaf), the causative agent of Africa citrus greening disease (ACGD). This study evaluates the diversity of ACT parasitoids and further characterizes endosymbionts associated with both T. erytreae and its parasitoids that could be used as biological control agents of T. erytreae and management of ACGD. Mitochondrial cytochrome oxidase I gene was used to reconstruct T. erytreae and its parasitoids phylogeny, while 16S rRNA gene was used for the bacterial phylogeny. One well‐supported clade of ACT was detected within the Triozidae phylogeny, while the parasitoid species clustered into four groups within eulophid and encyrtid phylogeny. The phylogenetic result of parasitoids was supported by morphological identification where five different parasitoid species could be identified, that is Tamarixia dryi, Psyllaephagus pulvinatus, Tetrastichus sp., Aphidencyrtus cassatus and Charipine species. Moreover, four eubacterial symbionts (Wolbachia,Rickettsia,Arsenophonus and Candidatus Liberibacter sp.) were detected in T. erytreae and three symbionts (Wolbachia,Rickettsia and Cardinuim) in the parasitoid specimens. Maximum likelihood phylogenetic inferences clustered the identified eubacterial symbionts within α and γ proteobacteria subdivisions. Phylogenetic inferences of 16S rRNA gene sequences indicated that Wolbachia strains from ACT and the parasitoids did not form a single monophyletic clade; however, both clustered within Supergroup B. The impacts of these parasitoid species and endosymbionts on ACT are still unknown, but their occurrence and broad distribution indicate the possibility of future use for control of T. erytreae. [ABSTRACT FROM AUTHOR]

Background: Simian immunodeficiency virus (SIV) naturally infects African non‐human primates (NHPs) and poses a threat of transmission to humans through hunting and consumption of monkeys as bushmeat. This study investigated the as of yet unknown molecular diversity of SIV in free‐ranging Chlorocebus species (African green monkeys—AGMs) and Papio anubis (olive baboons) within Mombasa, Kisumu and Naivasha urban centres in Kenya. Methods: We collected blood samples from 124 AGMs and 65 olive baboons in situ, and detected SIV by high‐resolution melting analysis and sequencing of PCR products. Results: Simian immunodeficiency virus prevalence was 32% in AGMs and 3% in baboons. High‐resolution melting (HRM) analysis demonstrated distinct melt profiles illustrating virus diversity confirmed by phylogenetic analysis. Conclusions: There is persistent evolutionary diversification of SIVagm strains in its natural host, AGMs and cross‐species infection to olive baboons is occurring. Further study is required to establish pathogenesis of the diverse SIVagm variants and baboon immunological responses. [ABSTRACT FROM AUTHOR]

Background: Little is known about the impact of HIV-1 group M subtypes on mother-to-child transmission (MTCT) of HIV-1 in African settings where multiple HIV-1 group M subtypes are co-circulating., Objective: To assess the role of subtype variation on MTCT., Methods: HIV-1-infected women attending an antenatal clinic in western Kenya were enrolled for a prospective study (1996-2000) of MTCT. HIV-1 subtype analysis of p24gag and gp41env identified potential recombinants, and their role in MTCT was determined., Results: Among 414 women for whom HIV-1 subtype and HIV transmission status were available, MTCT occurred in 80 (19.3%). MTCT rates were higher among women with subtype D compared with subtype A in either the gp41 region [31.6 versus 16.1%, relative risk (RR) 2.0, P=0.002] or p24 region (29.9 versus 18.0%, RR 1.7, P=0.02). Discordant subtype combinations were identified in 103 of the women (25.9%), and were associated with higher rates of MTCT (28.2 versus 17.0%, RR 1.7, P=0.01). In multivariate analysis, women with subtype combinations D/D, D/A, and A/D had an increased risk of MTCT (adjusted odds ratios 3.5, 2.5, 6.2; P=0.005, 0.05, and 0.0003, respectively) compared with A/A women after adjustment for maternal HIV viral load, placental malaria infection, episiotomy or perineal tear, and low birthweight., Conclusion: MTCT appears to be more common among mothers infected with subtype D compared with subtype A. Such differences in MTCT frequency may be caused by altered cellular tropism for placental cell types.