Demographic, Clinic characteristics and risk factors of studied subjects
All the women enrolled in this study were Tunisian nationality. The age range across the studied population was 18 to 73 years with a mean age of 37 years. Majority of women from the general population and with cervical lesion (HGSIL and LGSIL) were married (85%) and monogamous. The median age at first intercourse was found to be 19 years (ranges l2 to 27 years). This population was homogenous in terms of social habits. None of the women had history of using contraceptive or condoms systematically, smoking or drinking alcohol. Out of forty-three women with cervical lesions, sixteen were diagnosed as LGSIL and twenty-seven as HGSIL. All the sex workers enrolled in the study were legal, relatively homogenous in terms of sexual activity and high exposure risk factors for HPV infection. Fourteen (27.4%) sex workers had experienced first intercourse before the age of 20. The mean of years of sex work was 4 years (ranging 0 to 16 years). Majority of sex workers reported smoking (n=45, 88.2%) and drinking alcohol (n=25, 49%). The condom use was reported as follow: 18 women (35%) never, 14 women (27%) sometimes and 19 (37%) all of the time.
HPV DNA positivity and antibodies response against anti-L1FG/HPV-16 peptide
As expected, frequencies of the HPV DNA detection were significantly higher among women with HGSIL (81%), LGSIL (62%) and legal sex workers (39%) than general population (16%). The distribution of anti-L1FG/HPV-16 antibodies for all studied populations is summarized in Table 2. Systemic IgG response frequency was significantly higher among women with LGSIL (43.7%; P=0.001) and legal sex workers (25.5%; P=0.002). However, similar frequency was observed in women with HGSIL and general population (14.8% versus 11.7%). Systemic IgA and the local IgG responses were more frequently detected among the legal sex workers, suggesting that these antibody responses correlated with the lifestyle of these women. Unlike all the women groups, the frequencies of the local IgG and IgA were not significant in cervical secretion from women with HGSlL. In addition, we noticed that the frequency of the women with anti- L1FG/HPV-16 antibodies was lower than that with HPV DNA. In contrast, when we consider HPV-16 DNA positive women, only the women with HGSIL have a lower frequency of detected antibodies (48% versus 18% in sera and 0% in cervical secretions).
To identify a prognostic signification of the anti-Ll FG/16 antibodies, we extended our analysis and compared the antibody responses among women diagnosed with LGSIL and HGSIL. The proportion of local IgG and IgA was very low in cervical samples and could not be compared. However, in sera, the frequency of the antibodies was significantly more elevated among women with LGSIL compared to HGSIL (43.7% versus 14.8%; P=0.04). In contrast, the HPV-16 DNA prevalence was higher in women with HGSIL than LGSIL (54% versus 6%; P=0.004). Consequently, antibodies detected using the FGL1/HPV-16 were inversely correlated with the gravity of the lesions as well as with HPV-16 DNA detection.
As antibodies are a marker of past as well as present infection, we examined the relationship between HPV-16 capsid FG loop sero-reactivity and the status of HPV-16 infection (Table 3). The overall frequency of HPV-16 DNA positivity was 13% (n=23/179), interestingly none of the HPV-16 positive women showed positive systemic or local IgG responses. However, among HPV-16 DNA negative women but infected by HPV types other than the HPV-16 (types 6, 11, 18, 31 and 33), we detected a higher frequency of antibody responses in both sera and cervical secretions. These results suggesting that the IgG response elevated against the FG loop was independent of a current infection with HPV-16.
Table 2. Distribution of anti-LlFGJHPV-16 IgG and IgA antibodies in women with different risk of HPV infection
|
Serum
|
Cervical secretions
|
IgG
|
IgA
|
IgG
|
IgA
|
n
|
f (%)
|
p value
|
n
|
f (%)
|
p value
|
n
|
f (%)
|
p value
|
n
|
f (%)
|
p value
|
General population * (n=85)
|
10
|
11.7
|
|
5
|
5.8
|
|
1
|
1.1
|
|
3
|
3.5
|
|
Legal sex workers (n=51)
|
13
|
25.5
|
0.002
|
12
|
23.5
|
0.002
|
8
|
15.7
|
0.001
|
4
|
7.8
|
0.2
|
LGSIL (n=16)
|
7
|
43.7
|
0.001
|
3
|
18.7
|
0.1
|
2
|
12.5
|
0.006
|
1
|
5.5
|
0.5
|
HGSIL (n=27)
|
4
|
14.8
|
0.4
|
4
|
14.8
|
0.1
|
0
|
0
|
0.7
|
0
|
0
|
0.4
|
The chi-square and the Fisher test were used to determine significant differences (P value)
* Reference group
f: frequency
n: number
Table 3. Distribution of anti-L 1 FGIHPV16 IgG and IgA antibodies and HPV cervical infection among the women of the study
|
Serum
|
Cervical secretions
|
|
IgG
|
IgA
|
IgG
|
IgA
|
|
n
|
f (%)
|
p value
|
N
|
f (%)
|
p value
|
n
|
f (%)
|
p value
|
n
|
f (%)
|
p value
|
No HPV infection* (n=111)
|
22
|
20
|
|
12
|
11
|
|
5
|
4.5
|
|
5
|
4.5
|
|
Infection with other HPV type§ (n=45)
|
12
|
26.6
|
0.3
|
8
|
17.7
|
0.2
|
6
|
13
|
0.05
|
2
|
6.6
|
0.6
|
HPV 16 infection
|
0
|
0
|
0.01
|
4
|
17.4
|
0.2
|
0
|
0
|
0.3
|
1
|
4.3
|
0.7
|
The chi-square and the Fisher test were used to determine significant differences (P value)
*Reference group
§HPV positive for the foIIowing types, HPV-6, -11, -18, -31 and -33
ffrequency
We have previously shown that HPV infection decreased with age, among the women of the general population and the legal sex workers [26]. To assess if we observed the same pattern with the antibody reactivity to the L1FG/HPV-16, we compared the HPV DNA prevalence and detection of systemic and local IgG with age (Figure 1). Among the general population, the frequency of HPV DNA prevalence and IgG response was less than 20% and did not change significantly with age. Among the sex workers, frequency of systemic IgG response appears to increase (21% to 66%) but HPV DNA prevalence decreased (54% to 25%) with age. Among the women with cervical lesions, HPV DNA prevalence remained elevated, but frequency of systemic IgG response decreased (57% to 0%) in all the age groups. Therefore, when we compare the pattern among sex workers and women with cervical lesions, we observed reversed progress, suggesting that the higher frequency of anti-L1FG/HPV-16 antibodies leads to the regress of HPV DNA positivity.