The Detection and Characterization of Herpes Simplex Virus Type 1 in Confirmed Measles Cases

Abstract

Based on measles surveillance in Shanghai, People's Republic of China, from 2006 to 2015, we found that measles virus isolates from 40 throat swab samples exhibited atypical cytopathic effects in Vero/hSLAM cells, which was found to be a result of coinfection with measles virus (MeV) and human herpes simplex virus type 1 (HSV-1). Serological and molecular approaches were used to confirm and characterize the coinfections in these patients. Among the 40 measles cases, measles-specific IgM was detected in 37 cases, while measles-specific IgG was detected in 27 cases. HSV-1-specific IgM and IgG were detected in 7 and 34 cases, respectively, suggesting that most of the MeV infections were primary, but that HSV-1 infection was due to the reactivation of latent virus in most cases. The titers of HSV-1 IgG in patients with either measles or measles-HSV-1 coinfection were significantly higher than those in the healthy group (P = 0.0026 and P < 0.0001, respectively); however, there was no significant difference in the titers of HSV-1 IgG in the MeV and MeV-HSV-1 coinfection patients (P = 0.105). Nucleic acids from MeV and HSV-1 were detected in 40 and 39 throat swabs, respectively. Twenty five MeV RNA sequences were genotyped, and all represented genotype H1, which is the endemic genotype in China. Sequences from the glycoprotein G gene of HSV-1 were used to classify the isolates into two distinct phylogenetic groups: 34 belonged to group A and 3 belonged to group B.

Figure 1

Laser scanning confocal microscopy of Vero/hSLAM cells coinfected by MeV and HSV-1 from different passages. Vero/hSLAM cells were infected with virus isolated from the clinical throat swab from SH13390 at the third, sixth, and tenth passage; these cells and a cell control (3^rd, 6^th, 10^th, CC) as indicated on the left were subjected to immunostaining using antibodies against MeV M (green) and HSV-1 ICP0 (red) protein. Images were captured at 40× magnification using a Leica TCS SP8 confocal microscope (Leica Microsystems; Wetzlar, Germany). The cell nuclei were stained with DAPI.

Figure 2

Phylogenetic tree of selected MeV strains isolated from Shanghai from 2006–2015 based on the N-450 sequences. Sequences shown in color are from this study: red represents HSV-1 coinfection cases, blue represents genotype D8 and green represents genotype B3. Sequences in black are from reference strains of different genotypes or subgenotypes. The numbers at the nodes are bootstrap values.

Figure 3

Phylogenetic tree of HSV-1 isolates from Shanghai from 2006–2015 based on nucleotide sequences from the gG gene. : group A isolates from coinfection cases; : reference strains from group (A); : group B isolates from coinfection cases; : reference strains from group B; : reference strains from group C; : AF117121 (a recombinant strain reported previously). The numbers at the nodes are bootstrap values.